Chicken Diseases

Diseases

Credit: Biovision-Infonet

What causes diseases? 

• Infections with microorganisms
• Parasites (Internal and external)
• Malnutrition
• Injuries
• Chemical (eg. Sodium chloride poisoning).

Disease outbreak and death of the animals depend on their age, nutrional status and hygiene of their housing. 

Characteristics of healthy birds:Alert and on guard.Bright eyes and comb.Walk, run, stand and scratch.Continuously eat and drink.Normally lay eggs.Normally smooth and neat feathers.Soft compact droppings breathe quietly.

Characteristics of unhealthy birds/sick birdsTired and lifelessDull eyes and combSit or lie downEat and drink lessLay less or stop laying eggsRuffled and loose feathersWet droppings with blood or worms, diarrheaCough, sneeze and breathe noisily.

Health and disease management

• Starts at the hatchery and continues to maturity.
• Poultry will often remain healthy when they are well fed and managed,  vaccinated against diseases when relevant in your area.
• In case of disease outbreak, sick birds should be isolated and dead birds removed burnt or buried
  • Apply strict sanitary measures in all houses. 
  • Notify veterinarian as soon as possible.

Good disease prevention practices 

• Vaccinate the chicken as recommended by the vet
• Vaccinate only health chicken
• Give access to the right feed and clean water, in particular for small chicks
• Build shelters against wind and rain and predators
• Clean houses regularly and apply lime wash/disinfect the floor and walls
• Provide dry litter regularly where applicable
• Do not put too many birds together
• Different species of poultry for example hens, turkeys, pigeons, ducks and guinea fowls should be kept separate
• Separate chicks from adult birds except from the mother hen
• Isolate and treat sick birds
• Burn or burry dead birds (do not try to eat sick birds that have died – diseases can sometimes transfer to human beings never mind how well they are cooked).

Vaccination regime recommended for commercial chicks, but also applicable to improved management of indigenous chicken (Sigma feeds chicken recommendations):

Age	Vaccinate against	Application
1st week	Marek and Newcastle disease	Subcut (neck)
2nd week	Gumboro	In drinking water
3rd week	Lasota + IB (Newcastle)	In drinking water or eye/nostril drop
4th week	Deworming, IBD forte	In drinking water
5th week	Lasota + IB	In drinking water
6 – 8th week	Typhoid	Injection
9th week	Deworming (every 2-4 weeks)	In drinking water
8 – 10th week	Fowl pox	Wing stab
12 – 14th week	Typhoid	Injection
16 – 18th week	Renewed Newcastle (where disease is prevalent)	Optional

Importance of a disease is judged by mortality rates and effect on production. Diseases in poultry are divided into three categories:

• High importance
  • high mortality (more than 30% of the flock)
  • highly contagious and difficult treatment. 
• Medium importance
  • medium mortality (10-30%) of the flock and/or difficult treatment.
• Less importance, signifies not common
  • lower mortality and/or easy treatment 

Diseases with high mortality (more than 30% of the flock), highly contagious and difficult treatment

• Newcastle Disease
• Avian Influenza (AI)
• Fowl pox 
• Fowl cholera (pasteurellosis)
• Coccidiosis (internal parasites)

Disease with medium mortality (10-30%) of the flock and/or difficult treatment

• Pullorum disease (Baciillary white diarrhea)
• Fowl typhoid
• Gumboro (Infectious Bursal Disease, IBD)
• Infectious coryza
• Chronic respiratory disease (Mycoplasmosis)
• Roundworms and tapeworms (Internal parasites)
• Mycotoxicosis (fungal poisoning)
• External Parasites

Less importance, signifies not common, lower mortality and/or easy to treatment

• Marek’s disease
• E. coli infection
• Scaly legs
• Nutritional diseases 

1) Nutritional diseases

Symptoms: Bone and leg deformation and feather loss. The birds walk with difficulty; they limp.  Some deficiencies may cause feather loss. Treatment, if detected in time: Supplementary vitamins and calcium, fresh grass, and cow dung. Nutritional diseases may be avoided when the birds have access to normal vegetation and are therefore rare in scavenging chickens. 

2) Protozoan diseases

Protozoa such as Emiria tenella (coccidia) are larger than bacteria and can be easily seen under the microscope. Protozoan diseases are caused by poor hygiene and sanitation. Symptoms: Sick looking birds with head down, ruffled feathers and bloody diarrhea, death of young chicks.
Prevention and control:

• Avoid keeping different age groups of birds in the same house as disease may spread from adults to young chicks
• Use of EM or BM in drinking water for prevention
• Clean up chicken house and disinfect the area with lime (dusting with whitewash or agricultural lime)
• During outbreaks use coccidiostat mixture in drinking water

3) Bacterial diseases

Bacteria are minute germs that can only be seen under microscopes. Bacterial diseases can be prevented through good hygiene and sanitation. Very common are diseases caused by Salmonella bacteria, namely:

• Pullorum disease. It is caused by sub-species S. pullorum and it is severe by chicks. It is transmitted from hen to chicks during egg formation, contamination of eggs during laying or the chicksget infected form faeces. 
  Symptoms: dead embryo in eggs that do not hatch; chicks develop wet tails within the first week; whitish diarrhoea, chicks walk with difficulty, show big bellies and drag their wings, huddling anddifficulty in breathing. Mortality can reach 100% in the first two weeks. 
• Fowl typhoid. It is caused by the species S. gallinarum and it affects growers and adult chickens. It is spread through contamination of feed and water by faeces of infected birds.
  Symptoms: Usually seen in older birds, high body temperature, tiredness, blue comb, decrease in egg production, egg fertility and hatchability; anorexia and dullness followed by sudden death.
• Salmonellosis. It is caused by another Salmonella species. It affects chicks and adults.It is spread by contamination of eggs at laying or through contaminated feed and water and faeces. 
  Symptoms: Decline in egg production, egg fertility and hatchability; anorexia and dullness followed by sudden death.
• Collibacillosis. It is acute in chicks and chronic in adult chicken. Common in newly hatched chicks. Chicks get contaminated through eggs and contaminated faeces, while feed and water transmit the disease to both chicks and adults. It can be prevented by keeping good egg and nest sanitation. 
  Symptoms: Respiratory distress, diarrhoea, high mortality of chicks and dead embryos in spoiled eggs. 
• Infectious Coryza. This disease can be acute, mild or chronic. Contamination occurs by faecal matter, aerosols or through feed and water. It can be prevented by vaccination with bacterin in water at 10 to 12 weeks and 16 to 18 weeks.
  Symptoms: Swollen watery eyes, closed eyes, nasal discharge (runny nose), laboured breathing and decrease in egg production. All clinically ill chicken should be destroyed.
• Fowl Cholera (Pasteurellosis). This may occur at all ages of chicken, causing infection of the stomach region. 
  Symptoms: severe diarrhea, breathing problems, loss of appetite, blue combs and wattles. May occur as a cronic disease or as sudden death. Infection is mainly through contaminated feed and drinking water. There is no treatment. Best prevention is strict hygiene and vaccination. Destroy through killing and burn affected birds. 

Prevention and control Salmonella and other pathogenic bacteria are present in the air and feaces of most animals, and can even be present in some of the food items bought in the shops. Bacterial diseases can be prevented through good hygiene and sanitation. Which means regular cleaning of chicken houses and runs, regular disinfections with lime, etc. Some diseases such as fowl typhoid can be prevented by vaccinating the birds. 

Note: Do not vaccinate sick birds. They are too weak to handle vaccinations and may die.

4) Parasitic diseases

Parasites are organisms that live in or on a host (animal or plant); the parasite obtains nourishment from the host without benefiting or killing the host. Chicken parasites include lice and fleas, and worms living in the opening of organs. They may cause diseases and weaken the immune-system, making the chicken susceptible to other diseases.Worms

Worms inhabit the alimentary canal and other internal organs such as lungs, trachea, etc. There are two groups of worms: round worms and flat worms.

a) Round worms 

• Ascridia galli. They infect both chicks and adult chicken. Infection occurs through eggs that are laid by female worms in birds’ entestines and are passed out in droppings. They mature in one week or longer, and are swallowed up by chicken, hatch and cause new infection. Prevention is difficult due to feeding habits, especially by scavenging chicken.
  Symptoms: Slow growth and stunted, culled feathers and drooping head, thirst, low egg production and death due to intestinal obstruction in young birds.
• Gape worms (Syngamus treachea). They infect the trachea (windpipe) of chicken. Adult worms live and lay eggs in the birds trachea; the eggs get coughed out or get swallowed into the oesophagus and discarded via faeces. The eggs hatch to larvae which infect chicken or enter intermediate hosts such as beetles and earthworms. 
  Symptoms: Difficulty in breathing and gasping for air (thus the term gapeworm), huddling, and death fue to suffocation.

b) Flat worms 

• Tape worm (Raillietina tetragona) infests scavenging chicken. The worms release the eggs free or retained in a segment. Beetles and snails ingest the eggs. The eggs develop in these intermediate hosts infecting chicken that feed on them. Prevention occurs by using clean containers.
  Symptoms: Stunting, Thirst, poor health, low egg production and death of young birds on poor diets.

Prevention and cure: Intestinal worms in chicken are controlled by regular deworming with recommended deworming medicine usually mixed with drinking water.
 c) External parasites

• The most common external parasites include lice, mites, fleas and ticks. They infest poultry houses and breed in cracks of the buildings. Infestation occurs through infected birds and pets, and affect all ages of birds but are severe in chicks.
• Prevention can be done by maintaining cleaniliness of the poultry nests and houses and sealing cracks in the walls and on the floors.
• Lice can be seen around eyes and nose. They lay eggs on the feathers and suck blood from chicken, causing discomfort.

 Mites live in cracks in the poultry houses, not on the host. They suck blood from the birds at night and remain in the cracks during the day. In severe infections, birds become anaemic. Fleas can be seen on the belly. They suck blood from birds after which they drop and lay eggs in the litter. The eggs mature to adult fleas, which can survive for up to a month without feeding. Attacks all ages any time, but occurs more frequently in humid chicken houses with bad hygiene. Adult birds are clearly disturbed and spend a lot of time pecking and polishing feathers. Young chicks may die from anemia. If not treated, mites, lice, fleas, ticks will cause weight loss and possibly loss of feathers due to the parasites sucking blood and to skin irritation  Treatment: Spray or dust with pesticides, ashes, and oil. Ashes and sulphur powder may be used where the hens do dust bathing. Nests may be protected by putting a few tobacco leaves mixed with ashes in the nests.

External parasites (behaviour and parasites) Scaly legs Scaly leg is caused by an external parasite irritating the skin on the birds’ legs.Symptoms: Legs clearly have scales and wounds and may become crippled in their appearance.
Treatment: Dip the legs daily in kerosene, oil or in an insecticide until the scales disappear.   

5) Viral diseases

Viruses can be prevented by vaccination. They are the smallest germs and can cause incurable diseases. There is no treatment for virus diseases.

a) Newcastle diseaseNewcaste is the most economically important and the only notifiable disease in chicken. Often 30-80% of the flock dies. It is spread by dogs, birds, wild birds and man. There is no cure, affected chicken must be killed in a most humane way. Prevention occurs only by early vaccination. 
Symptoms: Respiratory stress, lack of appetite, green diarrhoea, nervous symptoms and high mortality. Death can also be sudden without symptoms. 

b) Fowl PoxFowl pox is a chronic disease in adult birds and deadly among chicks and growers. It is caused by Pox virus and is transmitted by mosquito bites and mechanically through broken skin. Prevention occurs by clearing bushes. 

Symptoms: Pimples or scabs on the birds combs, wattle and eyelids, high body temperature a watery discharge from eyes, difficulty in breathing indicated by whizzing sound and loss of appetite, tiredness followed by sudden death. 

c) Infectious bronchitisThis is a contagious disease, acute in chicks and chronic in adult birds. Transmission occurs through faeces from sick birds, contamination of litter and by air. 
Symptoms: Sneezing, watery eyes, nasal discharge, wet droppings, poor egg shell 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%.  

d) Avian Influenza (Fowl plague)This is an acute disease in chicken, turkeys, ducks and wild birds. The disease is found naturally in ducks and other waterfowl, and may spread as a highly contagious and potentially dangerous form to chickens. Infects through contaminated feed and drinking water from ponds. Transmission occurs through contaminated faeces, water and air.
Symptoms: Respiratory distress, sneezing, swollen head and face, emaciation and nervous disorder. High flock mortality, blue and swollen comb and wattles, Infected birds must be destroyed and location of infection quarantined. Always call a veterinarian if you suspect AI. Do not eat infected birds. 

e) Infectious Bursa Disease (Gumboro)This disease is common in hatcheries. It affects young chicken 2 to 6 weeks old and it is rare in indigenous birds. Transmission occurs through feed, water and faeces.
Symptoms: Diarrhoea, sleepiness and depression, ruffled feathers and trembling of the head. Mortality is between 50% and 80%. The disease weakens the immun-system, making the birds more susceptible to other infections. It can be controlled by vaccinating the chicken when they are 2 to 6 weeks old though drinking water. 

f) Marek’s disease Seen only in birds older than 16 weeks. Initially the birds may show paralysis of one or both wings. Or one or both legs might be paralysed. The disease is a virus, so there is no treatment, but commercial vaccines are available.  

g) Mycotoxicosis (fungal poisoning)Symptoms: Weakness, pale combs. Treatment: Supplementary vitamins. Prevention: Proper storage of feed to prevent growth of the fungi producing mycotoxins, the cause of the disease.