Common Diseases

COCCIDIOSIS

Coccidiosis is caused by a host specific species of Eimeria and it is a protozoon common in chickens and less often in turkeys it also occurs occasionally in geese, guineas, pigeons, pheasants, quail, and many other birds. It is usually seen in young birds under conditions of warmth and high humidity or conditions that lead to wet litter.

The infective oocysts are present in the litter having been deposited there by infected chickens. Oocysts are easily transported by blowing dust, boots, clothing, crates, vehicle wheels, other animals, and people.

Susceptible chickens ingest sporulated oocysts in feed, water, litter and become infected. If exposure is moderate, the chickens become immune to that species of coccidia. Outbreaks occur when susceptible chickens ingest massive numbers of oocysts.

Coccidia produce lesions by destruction of epithelial cells in which they develop and multiply and by trauma to the intestinal mucosa and submucosa.

The clinical signs vary with species of coccidia. Pathogenic species cause diarrhoea which may be mucoid or bloody, dehydration, ruffled feathers, anaemia, listlessness, weakness, retraction of the head and neck. In turkeys, the signs are the same except the diarrhoea isn’t bloody.

The prevention of Coccidiosis is usually by the incorporation of anticoccidials in the feed. A low level exposure allows immunity to develop. Various products are available for treatment.

HEXAMITIASIS

This is seen in 1-9 week old turkey poults. It is caused by a motile protozoon Hexamita meleagridis (Hexamita columbae in pigeons).

Recovered birds often are carriers and shed the parasite in their faeces which contaminate feed, water and range. Susceptible birds get the organism by ingestion.

Initially birds are very nervous and active. They shiver, crowd around any heat source and have subnormal temps. There is watery or foamy diarrhoea and the birds dehydrate rapidly. Later on the birds are depressed, stand with their heads retracted, feathers ruffled and wings drooping before going into coma, and dying.

Diagnosis is by post mortem.

Hygiene is the most important factor in the prevention of outbreaks. Various treatments are available.

TRICHOMONIASIS

This occurs in pigeons and doves and raptors that feed on them and also in turkeys, chickens, and game birds. Outbreaks usually occur in warm weather.

The disease is caused by Trichomonas gallinae, a motile protozoon. Pigeons are carriers and contaminate surface water or water containers. Pigeons can transmit trichomonads to their young during feeding. Raptors expose themselves and their young by feeding them infected doves and pigeons.

The main clinical sign in pigeons, doves, and raptors is that they have trouble closing their mouth due to oral lesions. There is drooling and repeated swallowing movements with watery eyes in birds and lesions in the sinuses or periorbital area. In rare cases with penetrating cranial lesions may show CNS signs. Turkeys have a gaunt appearance with a hollowed area over the crop.

HISTOMONIASIS (Blackhead)

This is caused by Histomonas meleagidis, a protozoon and it occurs most frequently in exposed, unmedicated turkeys, especially under 3 months; it also occurs in chickens. Young birds are more frequently and severely affected.
It is transmitted by the ingestion of fresh faeces containing the infected ova of Heterakis gallinarum that are within earthworms.

The clinical signs initially are listlessness, anorexia, drooping wings and yellow faeces the head may be cyanotic. In chickens there may be bloody faeces. In the later stages there is depression, drooping wings, eyes closed, head drawn close to the body, and emaciation. Mortality may be 100% in young turkeys.

Diagnosis is by post mortem. Prevention is by practising good hygiene and not mixing turkeys with other species of birds. Also it is important to de-worm regularly. There is no treatment available.

MYCOPLASMOSIS

The clinical signs observed in birds with mycoplasmosis are red, swollen eyelids and conjunctival tissue with a clear ocular discharge. The condition can become more severe resulting in extreme swelling of the eyelid and conjunctiva, crust formation along the eyelid margins resulting in ulcerations on the cornea and purulent discharge and loss of sight. Inflammation of the sinuses may occur resulting in discharge flowing from the nares. The birds may also display wet, matted feathers on the face (especially around the eyes), fluffed body feathers, inactivity, weight loss, loss of appetite and death due to starvation, exposure or predation.

Domestic poultry display respiratory symptoms such as coughing, sneezing and nasal discharge. They are lethargic, stop feeding and undergo severe weight loss. In turkeys, the sinus under the eye becomes swollen.

A diagnosis can be made using blood samples and post mortem. There are a number of treatments available once a diagnosis has been made. The response to treatment often depends upon how early the disease was identified and treatment started.

MAREK’S DISEASE

This occurs in Chickens between 12 to 25 weeks of age; occasionally pheasants, quail, game fowl and turkeys can be infected. Marek’s disease is a type of avian cancer; tumours in nerves cause lameness and paralysis. Tumours can occur in the eyes and cause irregularly shaped pupils and blindness. Tumours of the liver, kidney, spleen, gonads, pancreas, proventriculus, lungs, muscles, and skin can cause incoordination; unthriftiness, weak laboured breathing, and enlarged feather follicles. In terminal stages, the birds are emaciated with pale, scaly combs and greenish diarrhoea.

Marek’s disease is very similar to Lymphoid Leucosis, but Marek’s usually occurs in chickens 12 to 25 weeks of age and Lymphoid Leucosis usually starts at 16 weeks of age. Transmission: The Marek’s virus is transmitted by air within the poultry house. It is in the feather dander, chicken house dust, faeces and saliva. Infected birds carry the virus in their blood for life and are a source of infection for susceptible birds. Treatment: none Prevention: Chicks can be vaccinated at the hatchery. While the vaccination prevents tumour formation, it does not prevent infection by the virus.