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Infectious Disease of the Chicken: a guide Book · June 2019

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Contents Page Foreword

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Bacterial Infections Fowl Typhoid Pullorum Disease Salmonellosis Campylobacter Escherichia coli (APEC) Pasteurella multocida (Fowl Cholera) Necrotic Enteritis Ornithobacterium rhinotracheale Gallibacterium Mycoplasma Infectious Coryza Other Bacterial Infections

4 5 6 7 8 9 10 11 12 13 14 15

Viral Infections Newcastle Disease Avian Influenza Gumboro (Infectious Bursal Disease) Marek’s Disease Fowlpox Avian retroviruses (ALV, REV) Avian Metapneumovirus Infectious Bronchitis (IBV) ILT Other viral infections

17 18 19 20 21 22 23 24 25 26

Other infections Eimeria (coccidiosis) Other Protozoal Infections Helminths Ectoparasites Fungal Infections & Mycotoxins

28 29 30 31 35

Management of Chicken Production Diet Housing Biosecurity Hygiene & Disinfection Management of Backyard Production in Developing Countries

38 38 39 41 42

Foreword The chicken is now the most reared livestock animal in the world; around 75% of all ‘farm’ animals being chickens. The reasons for this are many and varied, ranging from the adaptability of the chicken to many production systems to the high productivity of eggs or meat in modern hybrid layer and broiler breeds. The chicken represents an important source of income for village or backyard and semi-intensive systems which can range from a handful of birds in a village system, to small urban and peri-urban farmers who may rear a few hundred animals. Large scale, intensive production of meat and eggs brings affordable protein to many, though not without issues of disease and welfare. Infectious disease remains the biggest threat to chicken production. Zoonotic infection either from close contact with birds, or perhaps more importantly through foodborne bacterial infections also represent a real threat to human health. The aim of this guide is to act as a basic reference for the main infections associated with chickens regardless of the production system. It is intended to be used by anyone working with or studying poultry. It does not replace the definitive text ‘Diseases of Poultry’ now in its 13th edition, or ‘Diseases of Poultry’ in its 6th edition. These are excellent resources but are large and expensive volumes. The intention of this guide is one that can be easily carried in a pocket or a bag and will be accessible to anyone at no financial cost. This book is free and made available under a creative commons licence. An online PDF version will be free to download from the University of Liverpool website and a free smartphone app based on this content will also be available. This is made possible through financial support from United Kingdom Research and Innovation via the GIAA scheme and based around our BBSRC Newton Fund Project ‘Rapid Diagnostics and Control Strategies for Enteric Pathogens in Backyard and Commercial Production in Thailand and the Philippines’. I would also like to thank my current and former colleagues in Liverpool and Ethiopia who provided photographs and source material used in this guide particularly Rob Christley, Marisol Collins and Judy Bettridge Paul Wigley University of Liverpool, March 2019



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Section One Bacterial Infections Bacterial infections of the chicken remain a major problem both as a cause of ill-health for commercial and backyard chicken production, and as the chicken is one of the main carriers of Salmonella and Campylobacter, the most common causes of foodborne bacterial infection through meat and eggs. Unlike some viral infections, bacterial disease of the chicken is not usually associated with high-mortality outbreaks but more usually with endemic disease that can lead to mortality, morbidity and loss of productivity. As well as the specific agents detailed here, many bacterial species may act as secondary infections to viral or parasitic diseases. Treatment and control of bacterial disease has relied on the use of antimicrobial (antibiotic) drugs as a therapeutic, prophylactic and growth promoting use. The rise in antimicrobial resistance (AMR) is a considerable problem and needs us to address how antimicrobial are used in poultry production. Growth promoting antimicrobials have been banned in Europe since 2006 and other countries are following suit. In the United Kingdom, the promotion of good antimicrobial stewardship has led to more than a 70% reduction in use, with antimicrobial drugs increasingly restricted to therapeutic use. The rise of AMR means that care and consideration is need in the use of antimicrobials and that other control measures including improvements to hygiene and biosecurity, the use of vaccines and live therapeutics such as probiotic bacteria will play a more important part.



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Fowl Typhoid (Salmonella Gallinarum) The Pathogen • Gram negative bacterial rod • Facultative anaerobe • Avian-adapted serovar of Salmonella enterica now rare in Europe & North America • 09 serotype, no flagella Clinical signs • Acute, high mortality infection • Diarrhoea, frequently bloody, at later stages of infection • Inflammation of liver and spleen (hepatosplenomegaly) • White spot lesions on liver and spleen, with ‘bronzing’ of liver on exposure to air • Persistent carriers may not show symptoms Transmission/Epidemiology Experimental Fowl Typhoid in • Bird-to-bird transmission via 3-week old layer (right) faeces shows hepatosplenomegaly • Vertical transmission to chicks and liver discolouration Zoonotic risk compared to uninfected bird • Low risk (left). On prolonged exposure Diagnosis to air the liver can develop a • Culture of faeces or post ‘bronzed ’appearance mortem material on selective media (e.g Brilliant Green/XLD agar) • Low numbers can be detected by enrichment culture (selenite/RV media) • Serology (ELISA, slide agglutination) can detect exposure and carriers Controls • Vaccination • Good hygiene and biosecurity • Culling of infected birds is recommended



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Pullorum Disease (Salmonella Pullorum) The Pathogen • Gram negative bacterial rod • Facultative anaerobe • Avian-adapted serovar of Salmonella enterica now rare in Europe & North America • 09 serotype, no flagella Clinical signs • Acute high mortality infection of chicks • White diarrhoea • Inflammation of liver and spleen (hepatosplenomegaly) with small white spot lesions • Frequent persistent carriage-carriers may not show symptoms Transmission/Epidemiology • Frequent vertical transmission to chicks • Bird-to-bird transmission via faeces Zoonotic risk • Low risk Diagnosis • Culture of faeces or post mortem material on selective media (e.g Brilliant Green/XLD agar) • Low numbers can be detected by enrichment culture (selenite/RV media) • Serology (ELISA, slide agglutination) can detect exposure and carriers Controls • Vaccination • Good hygiene and biosecurity • Culling of infected birds is recommended



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Salmonellosis (Salmonella enterica) The Pathogen • Gram negative bacterial rod • Facultative anaerobe • Around 2,500 serotypes of Salmonella enterica can infect warm blooded animals including birds • Most frequent serovars are Typhimurium & Enteritidis Clinical signs • Intestinal carriage usually without clinical signs • Dependent of serotype and isolate may cause transient diarrhoea or systemic infection • Hatchery infections can lead to high mortality outbreaks Transmission/Epidemiology • Bird-to-bird transmission via faeces • Vertical transmission to chicks either via transovarian infection (S. Enteritidis) or via faeces in hatchery Zoonotic risk • Major foodborne zoonotic pathogen • Associated with eggs (S. Enteritidis) and poultry meat Diagnosis • Culture of faeces or post mortem material on selective media • Low numbers can be detected by enrichment culture (selenite/RV media) • Serology (ELISA, slide agglutination) can detect exposure and carriers Salmonella Typhimurium grown on XLD (left) and Brilliant Green Agar (right). Selective chromogenic (colour changing) culture media such as these are effective in isolating Salmonella from faecal or food material. Both turn a red-pink colour when Salmonella grow Controls • Vaccination of breeders and layers • Live attenuated (mainly drinking water) and inactivated injectable vaccines • Good hygiene and biosecurity • Routine surveillance of flocks is practiced in some countries such as within the EU.



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Campylobacter The Pathogen • Highly motile Gram negative spiral rod with “gull wing” appearance • Slight thermophile (41°C) and microaerophile (low oxygen) for • Main species associated with poultry is Campylobacter jejuni • Low infectious dose Clinical signs • Often carried without apparent disease • May cause mild-to moderate transient diarrhoea • Invasive infection may be associated with vibrionic hepatitis with ‘spotted’ lesions on the liver Transmission/Epidemiology • Rapid spread from bird-to bird via faeces • Can be carried by wild birds and vermin or transferred on boots, clothing and tools. Zoonotic risk • Most common cause of foodborne bacterial infection with poultry meat main source • High levels of contamination in commercial poultry production Diagnosis • Culture on selective media under microaerophilic conditions (approx. 10% O2) using cabinet or gas jar. • Blood free media includes Charcoal-Cefoperazone-Deoxycholate Agar (CCDA) • Media with blood such as Skirrow’s Agar or Columbia Blood Agar • Confirmation based on morphology and Gram stain Controls • No vaccine available • Good biosecurity and hygiene can reduce transmission Campylobacter jejuni on modified CCDA. C. jejuni has distinct flat and silvery or metallic-looking colonies on this selective media



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Escherichia coli (APEC) The Pathogen • Facultative anaerobic Gram negative rod • Wide range of strains ranging from part of the natural flora of the gut to highly pathogenic Avian Pathogenic E. coli (APEC) often of O1 or O78 serotype Clinical signs • Most E. coli carried without disease • Wide range of disease from opportunistic infection through to systemic colibacilllosis • Systemic colibacillosis is a syndromic condition ranging from respiratory disease (infection of air sacs) to lesions on organs including heart, liver and kidneys • Reproductive tract infection in laying hens can lead to egg peritonitis Transmission/Epidemiology • Spread from bird-to bird via faeces including via aerosols to respiratory tract • Almost always carried in the intestines that may lead to opportunistic infections e.g. following viral infection. Zoonotic risk • Limited, though some strains common to humans and chickens Typical pathologies associated with APEC. (From right to left) Perihepatitis with fibrinous lesions, pericarditis and airsacculits with exudate in respiratory tract Diagnosis • Largely based on pathology including fibrinous or caseous lesions of air sacs, lungs, liver and heart. • Culture can determine presence of E. coli • Serotyping or molecular methods (MLST or genome sequence) to determine pathotype Controls • Vaccine to O78 serotype has some efficacy • Good biosecurity and hygiene can reduce transmission • Antimicrobial treatment of layers may be appropriate



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Pasteurella multocida

(Fowl Cholera)

The Pathogen • Gram negative non-motile rod • Wide range of strains specific to species i.e. ruminant strains do not cause disease in chickens and vice versa Clinical signs • Acute high mortality systemic disease which can be mistaken for Fowl Typhoid-septicaemia, anaemia, haemorrhage and lesions on liver are all common • Chronic form is often associated with some increased mortality • Chronic form typically leads to facial swelling (Comb & wattles), decrease appetite and sometimes green diarrhoea occurs Transmission/Epidemiology • Spread from bird-to bird via feed or water contamination • Contamination of feed and water by vermin Zoonotic risk • Low Diagnosis • Bacterial culture or PCR • Further typing needed to confirm avianspecific variants Controls • Vaccines (mainly killed bacteria) • Good biosecurity, hygiene and rodent Green diarrhoea is a control can reduce transmission common feature of Fowl • Culling of infected birds is recommended Cholera in its chronic form • Antimicrobial treatment can stop Picture by Hassan Iraqui outbreaks, but care must be taken to remove any carrier birds.



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Clostridium perfringens (Necrotic enteritis/NE) The Pathogen • Gram positive spore-forming rod • A wide range of strains produce various toxins • Type A and NetB toxin producing strains associated with NE • Increased prevalence when antimicrobial growth promoters are withdrawn Clinical signs • Increased mortality and reduced productivity in flock • Diarrhoea and ruffled feathers • At post mortem necrotic lesions of the small intestine, sometimes with a pseudomembrane structure and occasional liver lesions

A

C

B

Intestinal lesions in experimental necrotic enteritis. Figure A shows a heavy pseudomembrane structure with a tan-yellow ‘Turkish Towel’ appearance. B & C show typical lesions with some pseudomembrane. Pictures: Filip Van Immerseel, Martina Husta & Evelien Dierick

Transmission/Epidemiology • C. perfringens is a normal part of the intestinal microflora and ubiquitous in the environment • Disease most frequent in broiler chicks 2-5 weeks of age • A number of factors (diet, stress, immunosuppression, coccidial infection) may trigger disease • Isolates may be transferred horizontally or vertically between birds Zoonotic risk • Low Diagnosis • Anaerobic culture on blood or clostridial isolation agar followed by Gram staining & biochemical confirmation • Toxin typing (PCR) Controls • Good biosecurity, management and hygiene • Control of coccidiosis & modification of diet-lower content of certain cereals such as wheat and barley may reduce incidence.



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Ornithobacterium rhinotracheale (ORT) The Pathogen • Gram negative, non-motile, slow-growing rod • Recently emerging pathogen of poultry Clinical signs • Respiratory disease with increased mortality and reduced productivity in flock • Birds may have difficulty breathing and show signs of pneumonia • Air sacculitis at post mortem and in sub-clinical cases at slaughter is common and can lead to carcass condemnation • May be a secondary infection to a range of viral pathogens and can be mistaken for the chronic form of Fowl Cholera Transmission/Epidemiology • Bird-to-bird transmission via aerosol • Vertical transmission via egg • Difficulty in culture may mean infection is often overlooked Zoonotic risk • Negligible Diagnosis • Optimal culture on 5-10% sheep blood agar under microaerophilic conditions to reduce overgrowth of other bacteria. ORT forms small white/grey colonies • Identification by ELISA or specific PCR Controls • Good biosecurity, management and hygiene • Some success with antimicrobial treatment but assessment of sensitivity important • Autogenous vaccines have been used in commercial production with mixed success.



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Gallibacterium anatis The Pathogen • Gram negative non-motile rod of family Pasteurellacae • Previously known as Pasteurella anatis/haemolytica or Mannheimia haemolytica • Haemolytic isolates are associated with disease • Both haemolytic and non-haemolytic isolates may be carried as a commensal in upper respiratory tract Clinical signs • Main site of infection is reproductive tract • Infection of ovaries and oviduct can lead to lesions and salpingitis • Infection most typical at point-of-lay and may be accompanied by diarrhoea • Respiratory tract infections may also occur Transmission/Epidemiology • As normal commensal organism, it may be carried in flocks without disease • Bird-to-bird transmission Zoonotic risk • Low but human cases are recorded

Gallibacterium anatis after 48h growth on Columbia Blood Agar. Smooth grey colonies with zones of haemolysis Picture Stefan Walkowski

Diagnosis • Culture on enriched media such as Columbia Blood Agar gives smooth greyish colonies with haemolysis • PCR and ELISA based tests are in development for confirmation Controls • Limited as carried as commensal • Good biosecurity, management and hygiene



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Mycoplasma The Pathogen • Mycoplasmas are small bacterial species of the family Mollicutes which lack a bacterial cell wall • Several species are associated with poultry with Mycoplasma gallisepticum and Mycoplasma synoviae most frequently associated with chicken Clinical signs • M. gallisepticum causes chronic respiratory disease with reduced productivity and reduction in egg quality. Some strains may cause conjunctivitis • M. synoviae may cause respiratory disease, but also affects joints leading to lesions and often thickening of the synovial membrane leading to swollen joints and difficulty in moving • Mycoplasmas are frequent secondary infections Transmission/Epidemiology • Mycoplasmas are shed in secretions so may be spread by aerosol, direct contact or via the environment Zoonotic risk • Minimal Diagnosis • Growth from swabs (e.g. nasal swabs) • PCR detection • Serological detection of exposure by ELISA or serum agglutination -particularly useful for monitoring at flock level Controls • Mycoplasmas have been eliminated from many breeding flocks so sourcing chicks from such flocks can reduce risk • Live and killed vaccines are available • Therapeutic antimicrobials following diagnosis



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Infectious Coryza Pathogen • Caused by Avibacterium paragallinaraum (Haemophilus paragallinarum) and less frequently Avibacterium gallinarum • Gram-negative non-motile rod shaped bacterium with capsule Clinical signs • High morbidity but relatively low mortality with rapid spread • Initial signs are nasal and eye discharge with facial swelling • Conjunctivitis, facial swelling and swollen wattles with breathing difficulties are main signs Transmission/Epidemiology • Disease is spread from bird-to-bird by direct contact or via contaminated feed and water • The disease is relatively short in duration but carrier birds can lead to re-infection Zoonotic risk • Low Diagnosis • Primarily based on symptoms • PCR or ELISA based detection • Culture difficult Controls • Good biosecurity, management and hygiene • Removal (culling) of infected and carrier birds

Swollen Wattles are a common sign of Infectious Coryza Photograph Sakina Rubab



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Other Bacterial Infections

Brachyspira (Fowl Spirochaetosis) Diarrheal (watery, often yellowish) disease caused by colonisation of intestine with species of Brachyspira, a Gram negative spirochaete. Enterococcus & Streptococcus Gram positive cocci that are facultative anaerobes that may associated with septicaemia, bone and joint infections, cellulitis and endocarditis. Enterococci form part of the early intestinal microbiome in commercial production and opportunistic infections may be a significant cause of mortality in young broilers. Staphylococcus Staphylococci are Gram positive facultative anaerobes that may be associated with septicaemia; bone, joint and tendon infections including arthritis, pneumonia and infectious dermatitis and skin abscesses. Clostridia Other Clostridium species may also affect chickens. Clostridium colinum can cause ulcerative enteritis. Infection with Clostridium botulinum can lead to botulism or limberneck. As in mammals the action of the neurotoxins produced can cause paralysis and can be fatal. A range of species may be associated with gangrenous oedema, cellulitis and dermatitis. Erysipelas Caused by the Gram-positive rod shaped bacterium Erysipelothrix rhusiopathiae. Erysipelas manifests as a rapid-onset, acute infection with despression and diarrhea. Inflammation may occur in multiple body systems, which may result is patches of dark thickenned skin. Mycobacterium avium (Avian Tuberculosis) M. avium is a complex of mycobacteria that can infect multiple hosts. In chickens infection is usually chronic with lesions found in lungs, liver, spleen and digestive tract. The health of infected birds tends to deterioate over many months.



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Section Two Viral Infections

Poultry viruses are often more ‘headline grabbing’ than other infectious agents due to the high mortality rates of some infections, and in the case of influenza its very real potential of causing human infections. Perhaps more than any other area the development of molecular tools have advanced both the study and our capacity to diagnose infection directly, rather than reliance on serological tests of exposure. Great advances have been made in viral vaccines. On the other hand intensification of poultry production has led to the increased prevalence of infections such as Marek’s Disease Virus and respiratory diseases including infectious bronchitis in allowing these viruses to spread through housed flocks. Indeed endemic viral infections like IBV, although not responsible for high mortality outbreaks lead to a high disease burden and economic costs. Unlike bacteria, there has not been the capacity for either therapeutic or preventative drug treatment hence the greater reliance on vacination. As genomic approaches open up new diagnostics, they also open our understanding of disease processes and potentially new targets to allow anti-viral therapies.



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Newcastle Disease (NDV) The Pathogen • Single stranded enveloped RNA virus • Member of Paramyxovirdiae • Frequent cause of high mortality disease outbreaks Clinical signs • High mortality (up to 100%) with respiratory and nervous system problems including twisting of head (torticollis), green diarrhoea and swollen heads • Mild form of infection can lead to respiratory disease including sneezing, nasal discharge and coughing Transmission/Epidemiology • Main route of transmission from birdto bird via faeces • Transmission by respiratory route from nasal discharges etc. • Can be carried by wild birds, transmitted via carcasses or transferred on boots, clothing and tools. Zoonotic risk Torticollis (twisting of head) • Negligible due to NDV infection Diagnosis • Serology via Haemagglutination Inhibition (HAI) test • Growth of virus from tissue samples • Molecular detection by sequencing or quantitative RT-PCR Controls • A range of live attenuated and inactivated vaccines available • Culling of infected birds • Good biosecurity and hygiene, including effective disposal of carcasses can reduce transmission



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Avian Influenza (AI) The Pathogen • Type A Influenza (RNA) virus • Member of Orthomyxovridiae • Highly variable with newly evolving variants • High Pathogenicity (HPAI) and Low Pathogenicity (LPAI) based on variant • Multiple serotypes (H and N), with HPAI primarily H5 & H7 serotypes Clinical signs • HPAI- High mortality (up to 100%) with respiratory and nervous system problems including twisting of head (torticollis), green diarrhoea and swollen heads (similar to NDV) • LPAI-mainly respiratory distress and diarrhoea Transmission/Epidemiology • Main route of transmission from bird-to bird via faeces. • Transmission by respiratory route from nasal discharges etc. • Transmission from wild birds and rodents including migratory birds, • Waterfowl including a ducks a major carrier of AI. H1N1 virus (gold) in cultured Zoonotic risk MDCK cells • Significant risk of zoonotic transmission (green) • LPAI can lead to conjunctivitis • HPAI can lead to human influenza Picture: Centers for • H5N1 HPAI associated with significant mortality Disease Control Diagnosis • Serology via Haemagglutination Inhibition (HAI) test or ELISA • Growth of virus in embryonated eggs • Molecular detection by sequencing or quantitative RT-PCR Controls • No treatment • Some vaccines available, but high variability limits protection. Vaccines protect against disease but not carriage of virus • Culling of infected birds • Good biosecurity and hygiene, including effective disposal of carcasses can reduce transmission



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Gumboro (Infectious Bursal Disease) The Pathogen • Double stranded non-enveloped RNA virus • Member of Birnoviridiae • Cause of immunosuppressive disease that targets the Bursa of Fabricius/B lymphocytes Clinical signs • Depletion of B lymphocytes leading to reduced antibody production • Increased susceptibility to a range of infections and poor vaccine responses • Acute infection in older birds can lead to a disseminated infection leading to listless birds that often huddle together Transmission/Epidemiology • Rapid spread from bird-to bird via faeces or respiratory route Zoonotic risk • Negligible Diagnosis • Serology by ELISA • RT-PCR Controls • Live attenuated vaccines and immune complex (live vaccines coupled with antibody) available-usually delivered via drinking water • Vaccination of breeders is important to give early protection via maternally-derived antibody • Good biosecurity and hygiene can reduce transmission

Marek’s Disease (MDV) The Pathogen • Marek’s Disease Virus is an alpha herpesvirus (large DNA virus) Clinical signs • Classical Marek’s- nervous system infection leading to paralysis typically leading to birds with a ‘hurdle jumper’ appearance. Infection may also lead to eye infection. Classical Marek’s is most likely to be seen in low intensity production environments • Virulent and very virulent MDV (vMDV & vvMDV) lead to neoplastic or tumour-forming infection more frequent in commercial flocks. Infection leads to transformation of lymphocytes in the blood causing them to become cancerous. This leads to lymphoma or cancer of the blood system which is usually fatal. MDV may also persist or become latent within the chicken where it can persist for life or re-emerge to cause lymphoma. Transmission/Epidemiology • Rapid spread from inhalation of feather dust/dander. Virus particles are released from feather follicles. Zoonotic risk • Negligible Diagnosis • Serology by ELISA • PCR Controls Classical Marek’s Disease in a Backyard • Multiple live attenuated, Chicken in Ethiopia. Nervous system vector and DNA vaccines infection leading to paralysis and ‘hurdle used in commercial jumper’ appearance production delivered by spray, drinking water or in ovo. • Early vaccines such as HVT did not prevent infection and drove evolution of the current virulent neoplastic form. • No treatment available so affected birds should be culled. • Good biosecurity and hygiene can reduce transmission.



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Fowlpox The Pathogen • Double stranded DNA virus • Member of Avipoxvirus genus Clinical signs • Cutaneous or ‘Dry’ Fowl Pox causes raised scab-like lesions on un-feathered areas (Comb, Wattle, mouth, legs, vent) and may lead reduced production • Infection of the trachea or oesophagus may lead to lesions that lead to impaired feed uptake and frequent secondary bacterial infections known as ‘Wet Pox’ Transmission/Epidemiology • Transmission is slow and primarily via airborne spread. • Biting insects can also transmit the virus in its cutaneous form. Zoonotic risk • Negligible Diagnosis • Serology by ELISA • RT-PCR Controls • Live attenuated and recombinant injectable vaccines • Vaccination often leads to a small lesion or ‘take’ at the vaccination site • No direct treatment of infection, but antimicrobials may be used against secondary bacterial infections.

Fowl Pox showing lesions on comb and wattle. Picture Roman Halouzka



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Avian Retroviruses The Pathogen • Avian Leukosis Virus (ALV)-alpha retrovirus group associated with formation of tumours including sarcoma • Rous Sarcoma Virus-first discovered oncogenic virus. Closely related to ALV. Together form the Avian Leukosis Sarcoma Vorus Group (ALSV or ASLV) • Reticuloendothelial Virus (REV)-Gamma retrovirus which can lead to leukosis (tumour) formation but often carried without disease Clinical signs • ALV- Can lead to a range of leukosis or cancer of blood cells including erythroid, myeloid and lymphoid leukosis. May lead to tumours of connective tissue (sarcoma). • Rous Sarcoma- formation of sarcoma • REV-Leads to three different syndromic conditions 1. Acute neoplastic disease leading to tumours in various body systems 2. Chronic neoplasia leading to lymphoid leukosis 3. Runting disease where there is a failure of chicks to fully grow. Transmission/Epidemiology • ALSV-vertical and horizontal transmission, though not very infectious. • REV mainly horizontally transmitted in flock. • Some possibility of biting insects transmitting viruses. Zoonotic risk • Negligible Diagnosis • ELISA & PCR-based diagnostic tests • Similarity of clinical signs to Marek’s means specific diagnosis is important Controls • Lack of specific controls and no vaccines • Elimination of ALV in breeding flocks through culling • REV may be present without disease



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Avian (Metapneumovirus aMPV) The Pathogen • Enveloped group of RNA viruses • Member of Paramyxovirus family Clinical signs • Can lead to ‘swollen head’ syndrome in broiler chickens and breeders • Low mortality respiratory disease in chickens which can lead to swelling around the eyes and a nasal discharge. • Infection in chicken can show little or no clinical signs • Bacterial secondary infections are common • In turkeys, infection causes a more serious disease-Turkey Rhinotracheitis Virus Transmission/Epidemiology • Direct contact within flocks Zoonotic risk • Negligible Diagnosis • Serology by ELISA • RT-PCR Controls • Live attenuated and inactivated vaccines • Use of antimicrobials to control secondary bacterial infections • Good management



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Infectious Bronchitis Virus (IBV) The Pathogen • Avian restricted Coronavirus (RNA virus) Clinical signs • Respiratory distress often affecting the whole flock • Signs include coughing/sneezing, gasping and discharge from the nasal cavity and reduced productivity • Although morbidity is high, mortality is usually less than 5%. • Some isolates may cause kidney damage(nephritis). • Secondary infections are common Transmission/Epidemiology • Highly transmissible via aerosol route and contamination of environment • Multiple serotypes with distribution around the world • The recently emerged QX-like type is a particular problem in many countries. Zoonotic risk • None Diagnosis • Serology by ELISA or slide agglutination • RT-PCR/ PCR can also rapidly identify serotype Controls • Multiple live vaccines available across serotypes including against QX strain • Protection across serotypes is limited, so ideal vaccination regimen may require multiple vaccines e.g. triple vaccine.



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Infectious Laryngotracheitis (ILT) The Pathogen • Alpha herpesvirus • Gallid herpesvirus 1 Clinical signs • Acute respiratory disease • Affected birds may display gasping, coughing and a foamy, sometimes blood-stained or caseous or cheesy exudate from mouth and nasal cavity. • Significant mortality may occur due to haemorrhagic lesions of the trachea restricting breathing • Mild and latent forms of infection show few if any clinical signs through virus may still be carried. Transmission/Epidemiology • Transmission primarily via airborne spread of droplets due to coughing etc. • Infected birds may remain carriers for life Zoonotic risk • Negligible Diagnosis • Based on clinical signs • Serology by slide agglutination • PCR Controls • Live attenuated vaccines including a fowlpox vector vaccine • Biosecurity & management



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Other Viral Infections Avian Encephalomyelitis Virus A Picornavirus that causes Epidemic Tremor. Infection can lead to a range of neurological problems including tremors. Adenoviruses Avian Adenoviruses or Aviadenoviruses are a group of DNA viruses. At least 12 serotypes infect the chicken where they initially grow in the intestines but may spread to cause infection throughout the body. Disease has no specific symptoms. Infection may persist and become latent and re-emerge later. Transmission is largely vertical through eggs. Reoviruses Double stranded RNA viruses including reovirus and rotavirus. Reovirus can cause an acute viraemia, but primarily affects the joints leading to viral arthritis. Vaccines are occasionally used in breeding flocks. Rotaviruses, which are species-specific, can lead to enteritis and diarrhoea. Chicken Anaemia Virus (CAV) A circovirus with a DNA genome. CAV is commonly carried in chicken flocks usually sub-clinically. CAV can lead to immune suppression, with its effects enhanced when a co-infection with other agents such as IBDV. Caliciviruses A family of small non-enveloped RNA viruses associated with liver infections in poultry giving rise to Big Liver & Spleen Disease and Hepatitis-Splenomegaly Syndrome. Chickens and vector-borne viruses Birds can act as hosts for several arthropod-borne viruses. Chickens can carry and amplify West Nile Virus, a mosquito-borne infection that can lead to encephalitis in humans. Young chicks are susceptible to disease, but older birds do not amplify infection and can be used as a sentinel species in surveillance. Chickens may also carry the tick-borne zoonotic infection Crimean-Congo Haemorrhagic Virus.



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Section Three Other Infections Whilst parasitic and fungal infections of the chicken are rarely a cause of mortality, with the notable exception of some Eimeria species, they do represent a considerable economic burden in terms of reduced productivity. Many of these infections are more commonly seen in backyard production where controls are often difficult to apply. Red Mite has emerged more recently as a problem in commercial laying flocks causing considerable welfare problems. Fungal infection and contamination of feed stuff with fungal toxins (mycotoxins) is both a risk to animal health and may be passed on to people through the food chain. For example, Afalotoxins in the food chain are associated with high levels of liver cancer. In many cases, simple low-cost steps can be taken to reduce parasitic infections, especially infestations with ectoparasites, that can improve health and welfare considerably.



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Eimeria (coccidiosis) The Pathogen • Seven species of the apicomplexan protozoa Eimeria can lead to coccidiosis in chickens • Clinical signs Disease can be divided into three groups based on the disease caused: Severe-E. brunetti. E. necatrix & E. tenella Moderate-E. acervulina, E. maxima Mild- E. mitis, E. praecox: • Infection can lead to diarrhoea or dysentery, reduced food and water intake, weight loss and visibly depressed birds. • Can be life-threatening to birds as infection can lead to bloody dysentery in severe cases. • Milder disease leads to general poor health including susceptibility to other infections and reduced productivity. Transmission/Epidemiology • Transmission via consumption of occysts (eggs) in faeces. • Contamination of environment, litter, feed etc can lead to persistent infection within flock as occysts may survive for 4 years. Zoonotic risk • Negligible Diagnosis • Detection and speciation of oocysts in faeces by microscopy or RT-PCR. Eimeria are mainly diagnosed through microscopy of their oocysts from faeces with differentiation into species based on size and morphology. E. maxima (pictured) are the largest oocysts at up to 30 µm Picture USDA-ARS

Controls • Vaccines (live and subunit) are available but relatively expensive and can have limited efficacy. • Prophylactic treatment with coccidiostatic drugs (ionophoric antimicrobials) widely used but problems with resistance, toxicity and entry of residues into food chain mean care is needed in use. • Good hygiene and management reduces risk of transmission.



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Other protozoal infections Histomonas (Blackhead) Histomonas meleagridis is more usually associated with turkeys, but can cause disease in chickens. It is usually transmitted via infection of the nematode Heterakis gallinarum which colonises the caeca. Histomonas may spread through the gut and into the liver forming lesions. Protozoa are spread by infection of the larval stages of Heterakis shed in faeces. Earthworms may also act as an intermediate host for the nematode and protozoan. Cryptosporidium Avian-specific Cryptosporidium baileyi and Cryptosporidium meleagridis are associated with respiratory and enteric disease respectively. Oocysts may be shed in faeces and persist in the environment for some time. Leucocytozoon Leucocytozoon spp. are arthropod-transmitted protozoa related to Plasmodium the parasite that causes malaria. L. caulleryi is the main species associated with the chicken infection and common in SE Asia. Infection leads to increased mortality and anaemia. The main vectors are blackflies and Culicoides midges. Avian Malaria Multiple Plasmodium species may infect birds via mosquito vectors with P. gallinaceum, P. juxtanucleare, and P. durae considered most pathogenic for chicken. Avian malaria may cause significant mortality in wild and caged bird species including penguins. Although avian malaria can cause mortality in commercial flocks, local indigenous chicken breeds in Asia or Africa are rarely susceptible and it is not a major threat to chicken production.



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Helminths (Worms) Chickens may be infected with a range of many intestinal worms. In general worm infections are not associated with mortality but can have an adverse effect on productivity. Worm burdens are usually greater in backyard production due to difficulty in control and the frequent use of anti-helminthic drugs in commercial production. The clinical signs associated with heavy intestinal worm burden are non-specific, but include loss of weight, appetite, condition and productivity, and in some cases diarrhoea with or without passage of worms or worm segments. Diagnosis is by clinical signs, the visible presence of worms and the identification of worm eggs in faeces by microscopy. Worm eggs shed in the faeces are directly picked up by chickens and can also lead to contaminated feed or water. Certain worm species, require an intermediate host, such as an earthworm or beetle, which can be readily eaten by the chicken when scavenging. Worm eggs can survive in temperate conditions in the environment for many months. Intestinal Nematodes • Perhaps the easiest intestinal heminths to diagnose are large roundworms, such as Ascaridia galli which can measure 5-10cm in length. Ascaridia live in the small intestine and infection can cause to damage of the intestinal mucosa that can lead to enteritis and failure to thrive. • Capillaria spp. are small nematodes that parasitize different parts of the intestinal tract dependent on the species. High Capillaria burdens can lead to disease. • Heterakis gallinarum is a caecal nematode which causes little damage itself, but in the main carrier of Histomonas. Gapeworm The gapeworm Syngamus trachea can be found in the trachea and lungs of infested birds, with high burdens cause the disease gapes which may manifest as difficulty breathing (breathing with an open beak) and cyanosis leading potentially to death. Syngamus eggs may persist for a long time in environment meaning the infection is most frequent in outdoor reared animals. Tapeworms Multiple species of Tapeworms may be found in the chicken, with species such as Raillietina species and Davainea proglottina found in the small intestine the most frequently associated with clinical disease.

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Ectoparasites Scaly Leg Mite • Scaly leg mites (Cnemidocoptes mutans) are common microscopic parasites that burrow and live within the skin of the birds’ feet and legs. • Heavy infestation will cause raised scales, crusting and distortion of the skin which in severe cases can lead to malformation, lameness and secondary infection of affected tissue. • Transmitted by direct contact with infected birds. Scaly Leg Mite infestation on an adult bird. Scaly leg mite is a difficult parasite to treat. Treatment involves a combination of softening the scales, via gentle regular washing, together with application of treatment to suffocate or kill the mites, such as paraffin jelly (Vaseline), paraffin, mineral oil or an insecticide. Treatment may take several months to have effect.

Red Mite & other skin mites • Mites are generally very small arthropods, just visible to the naked eye, and fast moving on the skin of the bird. • They are bloodsucking and heavy infestations can lead to irritation and severe blood loss that affects the overall condition of the birds • The Red Poultry Mite, Dermanyssus gallinae, lives in the housing environment and largely feeds on birds at night. • Ornithonyssus sylviarum and Ornithonyssus bursa are other main species of mites that live on chicken but feed during day and night.



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• Mites can be controlled by use of insecticides or through fumigation of houses. There should be a withdrawal period on consuming eggs of met following insecticide treatment The Red Poultry Mite (Dermanyssus gallinae) Picture Gilles San Martin

Ticks • Ticks are blood-sucking parasites that can be found on the skin, particularly areas with little or no feather cover, such as the face and under wings. Although small, all life stages, usually a bluebrown colour, are typically visible on the bird. • Infested animals may lose condition and show reduced productivity. The skin, comb and wattles may become pale due to blood loss, and red spots may be seen on the skin where the ticks have fed • The main species is the Fowl Tick (Argas persicus) though chickens may host other species normally associated with mammals including sheep and cattle ticks • Ticks often feed at night, living in cracks and crevices of housing in the day. • Reduction of ticks in housing, including use of insecticides can help in control. • Ticks may also act as vectors/carriers of several infections.

Fleas • The stick-tight or stick-fast flea (Echidnophaga gallinacea) is commonly found in warm tropical and sub-tropical climates. • Fleas are often visible in clusters firmly attached to the skin, typically around the eyes, on the face, comb and wattles. • Adult fleas feed on blood and stay firmly attached to the bird, while eggs and nymphs remain in the surrounding environment.



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• Flea infestations may lead to irritation and blood loss leading to poor condition. Heavy infestations in young birds can lead to death through anaemia.

Heavy infestation with the stick-tight flea, E.gallinacea. Clusters of female fleas can be seen attached to the featherless skin around the eyes, wattle and face. Fleas should not be physically removed but treated with Vaseline or paraffin.

Lice • Chewing lice are small, rapidly moving, yellow/brown parasites, often visible to the naked eye, which can be found over the entire skin and feathers of the bird. • Species commonly found include Menacanthus stramineus, Menacanthus cornutus, Menopon gallinae, Goniodes gigas and Goniocotes gallinae. • Lice are transmitted mainly through direct contact between birds, though heavy infestations and overcrowding can lead to transmission via shared infested bedding and roosts. • Birds can usually tolerate mild to moderate infestations, but heavy infestations can lead to anaemia through blood loss and lead to lost productivity. • Infestations may also lead to local skin irritation and damage. • Strict sanitation, avoiding overcrowded housing, providing dust or ash baths for the birds can help to treat lice, as will keeping roosting areas, nests, bedding and litter clean. • Insecticidal treatments and powders licensed for the treatment of mites can be used under the guidance of a veterinary or poultry specialist.



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The yellow body louse Menacanthus cornutus on light microscopy (100x).

Clusters of lice seen infesting the vent area of a hen. (Right), feather and skin damage typical of lice infestation (Left)



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Fungal Infections & Mycotoxins Aspergillosis Respiratory infection caused by various species of Aspergillus. Inhalation of spores, usually coupled with poor flock management (cold, high ammonia, excessively dusty housing) may lead to granulomatous lesions in trachea, lungs or air sacs. More frequent in chicks where it is called Brooder Pneumonia. Candidiasis Infection of crop, oral cavity or oesophagus with species of Candida, most frequently Candida albicans, can lead to crop mycosis or thrush. More common in younger birds. Most frequently occurs following antimicrobial therapy. Favus/Ringworm/White Comb Dry, scaly and often crusty lesions on unfeathered skin (comb, wattle, legs) caused by dermatophytic fungi, most commonly Trichophyton species. Mycotoxicoses Disease caused by ingesting fungal (myco) toxins found in feed or litter are called mycotoxicoses. Growth of fungi may take place on grain used for food, or more frequently during storage of grain or processed feeds. Avoiding contaminated grain and good storage conditions for grain and feed (dry and cool) reduce risk. Commercially produced feeds should test for mycotoxins in grain prior to formulation. Mycotoxins can both directly affect the health of birds or lead to increased susceptibility to common infections. In general, the effects of toxins are more pronounced in younger birds. Mycotoxins may also accumulate in muscle and in eggs which can enter the food chain and pose a risk to human health, notably increased risk of liver cancer.



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The major mycotoxins found in poultry are summarised in the table below: Toxin Type & Source

Where found

AfalotoxinsMaize, Aspergillus Peanuts flavus/parasiticus Millet, Sorghum and other grains OchratoxinMaize, Aspergillus Peanuts ochraceus Millet, Sorghum and other grains Trichothecence Wheat mycotoxinsMaize Fusarium, Stachybotrys & others Others: Citrinin Oosporein Moniliformin Ergot



Cereals

Effects of toxin

Comments

Liver damage, Most frequent Immunosuppression, toxicosis of Metabolic problems poultry. Kidney damage, Immunosuppression

Often found in conjunction with afalotoxins

Necrotic lesions/ulcers on epithelial membranes, Feather loss, Immunosuppression Various-but tend to manifest as poor wait gain/low productivity

Ulcers most common in mouth and on tongue

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Section Four Management of chicken production

Management of poultry is a complex subject and largely outside of the intentions of this guide. Here we aim to give some basic understanding of good practice that can be used by large or small producers and to give veterinarians and animal health officers some information to help provide advice in maintaining health and welfare.



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Diet Providing chickens with clean water and a balanced feed is very important to the health of poultry, as well as to maximize production. The feed should be high in its nutritional content and fulfil the nutrient requirement of chickens, which varies with age and production stage. In commercial production feed requirements are met to maximise production of the bird. For example, in Europe diets are based mainly around wheat or barley with vegetable protein and other supplements. In North America maize-based diets are more common. In developing industries access to commercial feed is not always available or may be variable in nutritional content. Backyard production a scavenging-based diet, with or without supplement to the diet may be more common. However, it is clear that supplementary feeding is needed to maximise productivity and support health and should be use whenever possible. Feed may be commercially-produced or sourced locally with what is available. In certain countries, such the United Kingdom, the use of ‘left over’ human food for chickens is prohibited due to concerns around zoonotic infections. Fresh drinking water should always be available and it is important that both feeders and drinkers are kept clean and regularly disinfected to reduce the risk of disease transmission. Top tips. • Ensure feed is stored in a cool, dry place to avoid fungal growth and mycotoxins • Ensure birds are fed a balanced diet. Absence of some micronutrients (minerals and vitamins) from the diet can lead to range of nutritional diseases • Ideally commercial feed should be heat treated to reduce the risk of pathogen transmission • Excessive feed should not be left on the ground to avoid attracting vermin • Drinkers and feeders should be cleaned and disinfected regularly Housing Commercially produced chickens, both layers and broilers, are usually housed. Layers may be caged, barn-housed or have access to outside space (free range). Broilers are usually reared in sheds on the floor, though like layers may have outside access in free range systems. In

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backyard production, specific housing may be provided, shared with other livestock or even people. Housing provides shelter, protection from predation and can help reduce the entry of infection into a flock. Ideal housing should provide warmth but be well-ventilated. For hens, the provision of perches and next boxes helps promote natural behaviours and improves welfare and productivity with even large-scale egg producers adopting these enhancements. Housing should be designed to allow easy cleaning and disinfection as required. Litter should be provided to absorb faecal material. A range of substrate including straw, paper, cocoa shells and wood shavings may be used. In Europe litter is replaced between broiler flocks, but in North America ‘Deep Litter’ systems are used, meaning additional litter is added with the theory that heat acts to kills any pathogens present. There is increasing evidence that deep litter systems are poorer for bird welfare and pose a greater risk in disease transmission. A separate brooder area for rearing chicks may also be useful, especially in backyard systems. This can allow supplementary feeding of the chicks without competition from older birds and provide protection. Simple constructions, even based around cardboard boxes can be used successfully. Top Tips: • Housing helps reduce the risk of predation and improve welfare • Housing should be well-ventilated with clean and absorbent litter material • Cleaning and regular replacement of litter material can help reduce disease transmission • Provision of nest boxes and perches should be considered Biosecurity The basis of biosecurity is to limit the exposure of flock to diseasecausing organisms. Whilst there is no single correct way to undertake biosecurity as all farms and production systems may differ, there are common approaches and rules that can be followed.



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Isolation, traffic control and sanitation are the three biosecurity principles which should be implemented in all production systems to prevent occurrence of disease in a flock, but how these are applied can be based on three main approaches 1. Procedural Biosecurity- identifying strategies to implement biosecurity, who will manage them and how they will be achieved 2. Physical biosecurity- The structural components around biosecurity such as equipment, buildings, hygiene barriers such as foot dips and vehicle washes, barriers to vermin etc. 3. Operational biosecurity- putting the identified procedures into place and appropriate record keeping. Procedural Biosecurity is based around identification of risks and what can be done in a practical way to reduce these risks. Step one: Identify what are the main disease risks and how are these likely to be brought into a flock. Step two: What can be done to reduce these risks? Step three: Put in place controls and management procedures. Physical Biosecurity is the mainstay of biosecurity. It is putting in place barriers to reduce the likelihood of a disease entering a farm. It can include: • Ensuring poultry houses are well built and maintained to reduce the risk of vermin entering • Buildings are located away from water where migratory waterfowl may land • Procedures are in place to effectively deal with waste litter and faecal material • Safe disposal (e.g. incineration of dead birds) • Provision of clean water and feed • Fencing to prevent vermin or unwanted visitors • House chickens separately from other animals • Providing hygiene barrier such as foot dips on entry, vehicle washes • Vaccination and disease monitoring prorammes • Providing quarantine quarters for new birds brought onto a farm • Provision of dedicated protective clothing and equipment for a farm or each house in large scale farms Operational Biosecurity is the day-today delivery of a biosecurity plan. It may include:



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• Record keeping of cleaning, sanitation, use of vaccines or medication • Exclusion of unauthorised visitors and records of any visitors kept • Ensuring any staff comply with measures in place e.g. use protective clothing, foot dips etc. • Providing staff training and updates • Provide protective clothing for visitors • Avoid bringing equipment onto site unless disinfected thoroughly The biosecurity regime adopted will depend very much on the type of production and site. Whilst the above would be appropriate for a large commercial farm, not all are practical or affordable for a small backyard farm. However, basic measures such as foot dips, dedicated protective clothing and prevention of wild birds and vermin should be considered on even the smallest farm. Hygiene & disinfection As mentioned above disposal of waste material and dead birds safely can reduce the likelihood of disease persisting within a flock. Whilst large scale producers will have a dedicated waste procedure, for small scale producers, disposal of dead birds by incineration or burying (with lime) can reduce disease transmission. Used litter may be burned or composted to reduce pathogen load. Regular cleaning or disinfection are important, especially if using an ‘all, in all out’ system which means housing can be regularly cleaned and disinfected between flocks. Cleaning of drinkers and feeders is important. All equipment should be cleaned and disinfected on a regular basis. Many different disinfectants are available and choice should be made based on the nature of housing and affordability. Ideally in use disinfectants should: • Have low toxicity. • Be made up to the appropriate working concentration • Replaced regularly, especially in foot dips and where there is high organic contamination (litter, faeces etc.) and records kept of this • Have a wide spectrum of activity and stably maintain its activity over a period of time. • Be cost effective.

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Management of backyard flocks in developing countries Every backyard or village system is, by its definition, unique to the householder but in many households, relatively low input improvements in management can increase productivity of both eggs and meat. There are obvious advantages in both vaccination and the use of supplementary feeding if affordable, and there is an argument that rearing smaller flocks with improved health and welfare may be more economically viable than over-extending flock sizes. The information given here is very much a guideline of good practice rather than ‘an ideal’ production system. Stock selection The following points should be considered when selecting or rearing birds: • Purchase of chicks or breed from existing stock. Whilst rearing chicks is cheaper, it will require more time. • When purchasing stock ensure you use a reliable disease-free supplier. • Consider having a period of quarantine for newly purchased flock in case of carriage of infectious agents. • Consider whether commercial hybrid breeds or local breeds are better suited to your needs. Whilst in theory commercial breeds are more productive, local chickens are better adapted to local conditions and are usually more resistant to diseases found in the area and better adapted to local environmental conditions. Housing Basic housing constructed out of locally available materials can help decrease losses of birds and improve welfare. Rearing birds away from the family house can also reduce the chance of transmission of a zoonotic infection. Any housing should provide shelter but be easy to clean and well-ventilated.



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Basic accommodation constructed from local materials such as this chicken shed in Ethiopia can protect birds from predation and the spread of infection from wildlife. Chickens are usually housed overnight and forage outside at day. Feeding



As described above, the provision of high quality, nutritious feed can enhance productivity. This can range from a simple handful of grain to more complex commercial diets. It is also vital that chickens have access to a clean and plentiful water source. Storage of feed to avoid contamination with pathogens, especially from faecal contamination by rodents and wild birds is important, as is ensuring a dry and relatively cool storage area to avoid the growth of fungi and production of mycotoxins. In general it is better to avoid ‘medicated‘ feeds as their use in the absence of disease can led to antimicrobial resistance and furthermore it is difficult to be certain that the listed ingredient is present in the quantity stated or indeed may not be that ingredient at all. It is more advisable to medicate animals as and when required. The simplest form of feeding is ground feeding, where small quantities of grain or pelleted feeds are scattered amongst a flock. For small numbers of birds this is a good method as it is quick and easy and allows the birds to forage for the feed promoting natural behaviour. However, in larger flocks it is difficult to ensure all birds receive feed and leaving larger amounts on the floor is not recommended as this may attract vermin or wild birds.



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For larger groups, it is better to place larger quantities of feed in a dedicated feeder. These can be purchased commercially or constructed at home. Metal and plastic are easier to disinfect, but wooden feeders that use readily available materials can also be effective. Any feeder should be cleaned regularly to avoid contamination. Any feed left uneaten in feeders after several days should be discarded to avoid fungal growth.

Nesting and brooding chicks

Fresh water should be provided for birds at all times. Bell drinkers are a good choice for small producers as the water does not evaporate and is less likely to become contaminated. Metal or plastic drinkers are widely available, but it is also possible to use waste plastic bottles to form a basic drinker. Bell drinkers such as the picture shown here also allow several animals to drink at the same time.

Perching and nesting are key natural behaviours for hens. Provision of nest boxes allows this behaviour and means that eggs are more likely to be laid in the same place regularly and make collection for sale, consumption or to be used to hatch new chicks easier. Eggs in a nest are less likely to be trampled on or broken than those laid on the ground. Simple nests can be made from a cardboard or plastic box with some bedding material. The material should be changed regularly and the box cleaned, though nesting birds are best left undisturbed.



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For larger groups a simple nest box construction may be made insider a poultry house that allows several hens to nest and perch. Where eggs are to be set to hatch chicks, it is best to select hens with good brooding instincts. A fertile egg takes around 21 days to develop and can be incubated by a hen or in an incubator. Small incubators are widely available but need a constant power supply. When hatched, chicks need protection from predation and from older, larger birds. They also need to be kept warm. Whilst some of this can come from the mother, it is also possible to use a brooder to rear the chicks on from hatch. In cooler climates, chicks may be provided with a heat source such as a lamp or a burner, though care must be taken to avoid direct contact with the chick or bedding and litter. In warm climates, such as South East Asia, chicks may not need an additional heath source. Various home constructed brooders can be made to help rear chicks.

Home constructed brooder in the Philippines. Construction is a large cardboard box with mesh roof and newspaper on the base. Chicks are provided with a bell drinker and feed in small troughs



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A ‘Hay Box’ Brooder in Ethiopia. Of simple wooden construction these boxes can protect and keep chicks warm especially overnight. Their use leads to increased productivity.



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