Every year chicken farmers undergo huge losses due to diseases on the farm. Therefore disease management is a huge consideration for anyone wanting to run a viable chicken farming business. Being able to recognise and respond to a disease attack on the farm is vital to have effective control of the attack.
A sick bird will generally look lethargic and unhappy. But that is not enough to diagnose the disease. The table below helps you identify some common diseases and what you can do about them.
Protozoa such as Emiria tenella (coccidia) are larger than bacteria and hence more easily visible by microscope. Outbreaks of protozoan diseases are an indication of poor sanitation and hygiene.
Prevention and Control
Vaccination and isolation of healthy birds from sick ones and proper disposal of dead birds can prevent diseases.
Vaccination is the use of mild, live or inactivated infective agent (virus or bacteria) to stimulate production of antibodies to a specific infective agent. Antibodies are chemical substances produced within the host body. They recognise and destroy the virus or bacteria used during vaccination before onset of disease. Vaccines are prepared from the same virus or bacteria that cause the disease to be vaccinated against. They are sensitive to heat, pH (acidity) and therefore should be handled following manufacturers’ instructions.
Vaccination for indigenous chicken in a free-range system depends on age, disease incidence, severity and status of endemic diseases (Table 2).
Bacteria are minute germs that can only be seen under microscopes. They cause diseases that can be prevented through good hygiene and treated using antibiotics such as Tetracycline.
Pullorum disease caused by sub-species S. pullorum is fatal in chicks. It is transmitted from hen to chicks during egg formation, contamination of eggs at laying or the chicks are infected from faeces. Symptoms include dead embryo in eggs that do not hatch, chicks develop wet vents (tail) within the 1st week, whitish diarrhoea, huddling and difficulty in breathing. Mortality can reach 100% in the 1st 2 weeks.
Fowl typhoid is caused by the species S. gallinarum and is severe in growers and adult birds. It is spread by contamination of feed and water by faecal matter from infected birds. Symptoms include drop in egg production, egg fertility and hatchability, anorexia and dullness followed by sudden death.
Salmonellosis is caused by any other Salmonella species. It is severe in both chicks and adult birds. It is spread by contamination of eggs at laying or to both chicks and adults through contaminated feed, water and faeces. Symptoms include drop in egg production, egg fertility and hatchability, anorexia and dullness followed by sudden death.
Sanitation, and eggs and nest fumigation using formaldehyde pellets in the nest can prevent it. Broad-spectrum antibiotics such as sulphur drugs can control infections. Control is by vaccination (Table 3).
Collibacillosis is acute in chicks and chronic in adult chicken. It is transmitted through eggs to chicks and through contaminated faeces, feed and water to both adult birds and chicks. Symptoms include respiratory distress, diarrhoea and high mortality in chicks while those in embryonic infection include dead embryos in spoiled eggs. It can be avoided by maintaining standard egg sanitation and using broad-spectrum antibiotics such as sulphur and tetracycline to treat and to reduce transmission. It can be controlled by vaccinating with bacterin.
Infectious Coryza can be acute, mild or chronic. It is spread by faecal matter, aerosols or through contaminated feed and water. Symptoms include swollen watery eyes, nasal discharge, laboured breathing and drop in egg production. It can be prevented by vaccinating with bacterin in water at 10-12 weeks and 16-18 weeks. All clinically ill birds should be destroyed.
Parasites are organisms that live on others without benefit to the host and include worms living in the opening of organs, and lice and fleas on the external. The parasites may cause diseases, weakening the system so that other disease-causing agents thrive or transmit diseases. Worms are internal parasites that inhabit the alimentary canal and other internal organs such as the proventriculus, gizzards, trachea, and lungs. There are 2 groups of worms, roundworms and flatworms (Fig. 6)
Roundworms Ascaridia galli infects both chicks and adult chickens. Eggs are laid by female worms in birds’ intestines and are passed out in droppings. They mature in one week or more after which they may be swallowed up by chicken, hatch and cause fresh infection. Clinical signs include slow growth (stunted), culled feathers and drooping head, thirst, low egg production and death due to intestinal obstruction in young birds. Due to their feeding habits, it is difficult to prevent this condition in scavenging chicken.
Gape worms Syngamus trachea roundworms infect the trachea (windpipe) of chickens. Adult worms live and lay eggs in the birds’ trachea; the eggs may be coughed out or into the oesophagus and swallowed in which case the hen passes the eggs in the stool. The eggs hatch to larvae which infect chicken or enter simple carriers (intermediate hosts) such as beetles and earthworms. Symptoms include difficulty in breathing and gasping for air, hence the term gapeworm, culling and huddling and death due to suffocation. The condition can be controlled by giving Thiabendazole or Gapex in drinking water.
Tapeworm Raillietina tetragona infests scavenging chicken. The worms pass eggs either as free eggs or retained in a segment. Intermediate hosts such as beetles and snails ingest the eggs or segments. The eggs develop in the host and in turn infect chicken that feeds on the intermediate hosts. Symptoms include stunting, thirst, poor health, low egg production and death in young birds on poor diets. It can be
prevented in scavenging chicken by using clean containers and drenching at 3- month intervals with Albendazole and Fenbendazole.
Isolation disposal of dead birds
Do not introduce new birds purchased from markets or given as gifts directly in to the flock. Keep them separate and observe them for at least one week. Sick birds should be confined away from the rest. Carcasses should be disposed of by burying at more than 3 feet underground.
Viruses are the smallest germs and cause incurable viral diseases. They should be prevented by early vaccination.
Newcastle disease is the most economically important and the only notifiable disease in chicken. It is spread by sick birds, dogs, wild birds and man. Symptoms include respiratory stress, lack of appetite, diarrhoea, nervous symptoms and high mortality. Sometimes death can be sudden without the symptoms (Fig. 7). Chicken that reach the tertiary stage showing nervous symptoms may survive but will always show lack of nervous co-ordination. The only way to protect chicken is by early vaccination.
Fowl Pox is a chronic disease in adult birds but acute and fatal among chicks and growers. It is caused by Pox virus and transmitted by mosquito bites and mechanically through broken skin. Clinical symptoms include pimples or scabs on the birds’ combs (Fig. 8), wattle and eyelids, a watery discharge from eyes, difficulty in breathing indicated by whizzing sound and loss of appetite. Mortality is low in adult chicken but high in chicks and growers. There is usually a drop in egg production in laying birds. The disease can be avoided by clearing bushes or controlled by vaccinating the chicken when they are 4 weeks old by wing web stab using a needle. Follow this by examining the vaccination site after 7 days for reaction. Pox virus can survive for 10 years in the soil. Since infected chicken are predisposed to secondary infections, infected chicken should be covered with an antibiotic treatment.
Fig. 7. (left) This hen did not show signs of sickness when it was put in the basket with chicks but died of acute Newcastle disease 4 h later. Fig 8. (right) A hen with Fowl Pox pimples on the comb
Infectious bronchitis is a contagious disease, acute in chicks and chronic in adult birds. The disease is transmitted from sick birds through faeces, litter and air. Symptoms in adults include sneezing and watery eyes, nasal discharge, wet droppings, and poor eggshell with no death unless from secondary infection.
Chicks gasp and cough, breath noisily, have watery eyes and nostrils, become depressed and huddle. Mortality can be as high as 25%. It is controlled by vaccinating with multiple serotype or covering with antibiotics during outbreaks.
|Chiggers, red bugs
|Air Sac Disease
|Ascarids (Large Intestinal Roundworms)
|Fowl pox can come in two forms, wet or dry.
•Areas without feathers have wart-like lesions that heal in about two weeks.
• lesions around the mouth
• discharge from the eyes.
|Fowlpox can come in two forms, wet or dry.
• unfeathered areas have wart-like lesions that heal in about two weeks.
• lesions around the mouth
• discharge from your eyes.
|Bowlegs in Chicken
|• chicks unable to walk in a straight line.
• chick may suddenly shake, topple and fall on their sides
• putting their heads between their legs.
• chicks alert. appetite not affected.
• Ruffled feathers.
• Loss of appetite.
• Nasal, ocular and oral discharge.
• Swollen and cyanotic wattles and face.
• Sudden death.
• Swollen joints.
|• ruffled feathers
• pale head
• drooping comb
• orange coloured diarrhoea
Fowl Tick (Blue Bug)
|• open-mouth breathing
• grunting sound
• difficulty breathing
|• open-mouth breathing
• grunting sound
• difficulty breathing
|• Reduced egg production
• discharge from • the bird's eyes and nostrils
• laboured breathing.
more on infectious brochitis
|• swelling of the face around the eyes and wattles
• nasal discharge
• swollen sinuses
• Watery discharge from the eyes
|Chickens with lymphoid leukosis have few typical clinical signs. These may include:
• depressed before death
• enlarged bursa and liver
|New Castle Disease
|• Egg laying stops.
• misshapen eggs are produced with rough shells and sometimes bleached shells.
• In chicks, gasping coughing and sneezing
• Birds may be seen sitting on their back hock joints
• walking backwards or in circles
• putting the head between their legs
• breathing difficulties, nasal discharge, murky eyes
• paralysis in their legs and wings.Newcastle Disease
navel illness, mushy chick disease
|• drowsy and droopy
• Down(feathers) “puffed up”
• stand near the heat source
• indifferent to feed or water.
• Diarrhoea sometimes occurs.
• poorly healed navels
• bluish colour of the abdominal muscles
|• Chicks utter squeaky chirps
• appear drowsy
• ruffled feathers.
• Vent smeared with faecal discharges.
• no external symptoms are seen in adult birds.
|• Droopy wings
• ruffled feathers
• pale beaks and shanks
• bloody diarrhoea
• weight loss.
|Twisted legsPerosis disease
|swollen, twisted, broken, or bowed legs, or loss of color in feathers, the comb, or the roof of the mouth.
|• bird has difficulty balancing while standing because the neck twists,
• bird tries to balance by permanently looking upwards.
|Ulcerative Enteritis (Quail disease)
inflammation and ulcers in the cecum and liver
|• Flaccid paresis of legs, wings, necks and eyelids
• The paresis rapidly progresses to paralysis
• birds fall into a deep coma with neck and head typically extended forward.
|chicken pecking each other
|CAPILLARIA (CAPILLARY OR THREAD WORMS)
|severe inflammation of intestines
Erosion of the intestinal lining
|Curly Toe paralysis
|• unable to stand or walk
• toes curled
|eating eggs laid by other birds or themselves.
|Infectious Bursal Disease (Gumboro)
|Gumboro has no symptoms of its own. But infections leaves the chick's immune system dented and thus it susceptible to many other infections.
|• swollen, red, and warm hock joints.
• limping and difficult painful in walking.
|also referred to as fowl paralysis,
• irregularly shaped pupils
• partial paralysis
|• Swollen stomach
• (postmotem: rotten intestines, foul smelling water in cavity)
|No signs in chicken but in quil:
• respiratory distress, coughing, sneezing, rales
• nasal or ocular discharge
• Loose, watery droppings
|too much scratching with feet and beaks.