«Infectious Diseases of Poultry A. Janmaat* and R. Morton, Biosecurity and Product Integrity, Darwin * Formerly of DoR INTRODUCTION Poultry that have ...»
Infectious Diseases of Poultry
A. Janmaat* and R. Morton, Biosecurity and Product Integrity, Darwin
* Formerly of DoR
Poultry that have an infection show a variety of symptoms, such as
respiratory problems, diarrhoea and paralysis. It should be
emphasised at the outset that prevention of infection in a poultry flock
through sound management is very important. This is because
although some infectious diseases can be treated, for many it is a waste of time and money and infected birds should be disposed of immediately.
Infectious organisms may be divided into four classes: protozoan, bacterial, fungal and viral. Specific drugs are usually recommended for bacterial, protozoan and fungal infections, while some viral diseases can be prevented by vaccination. For more information on suitable drugs, consult your local veterinarian.
The diseases commonly found in poultry in the Northern Territory (NT) are denoted by an asterisk (*).
Affected birds can be treated with antibiotics. To prevent further spread of this organism, disinfect the premises and the pens with a commercial disinfectant, and provide good drainage.
(b) *Salmonella infection (paratyphoid and pullorum) (i) Paratyphoid (salmonellosis) Salmonella infections may affect all domestic poultry, although adult birds often do not show any symptoms.
Salmonella bacteria may also contaminate hatching eggs, which results in diarrhoea, depression and death in young chicks. Paratyphoid is highly infectious and can be transmitted by mice, rats, other birds and/or through contaminated feed. Symptomless adult birds constitute a human health risk if meat and egg hygiene are not adequate.
(ii) Pullorum (bacillary white diarrhoea) Usually a symptomless disease in adults, pullorum is transmitted to young chicks through the egg. This results in fatal diarrhoea within the first four weeks of life. Adult birds may suffer from infection of the ovaries, or septicaemia. This disease can be eliminated with good hatchery hygiene. No cases have been reported in the NT in recent years. All poultry entering the NT must come from pullorum-free hatcheries. To avoid this disease, buy chicks only from a reputable hatchery.
(c) Psittacosis Psittacosis is found mainly in psittacine birds (parrots, lorikeets, galahs,cockatoos, budgerigars etc), but may also affect pigeons, turkeys and chickens. In chickens, symptoms may pass unnoticed or the birds may exhibit general weakness, diarrhoea and discharge from the eyes and nose. All infected birds should be culled and burned. The remainder of the flock should be treated with antibiotics in the feed. As the disease can be transmitted to humans, great care must be taken when handling infected birds. In humans, the disease resembles influenza but can progress to a severe, and possibly fatal, pneumonia.
(d) Avian spirochaetosis (tick fever) In chickens and turkeys the blood parasite Borrelia anserina causes a relapsing fever-like condition. This disease, which is transmitted by the fowl tick Argas persicus, has been diagnosed in Darwin, Alice Springs and on many stations. Birds of all ages may be infected. They become feverish, have green diarrhoea and may become paralysed in the wings or legs.
The disease can be controlled by eliminating ticks from the flock (see Agnote K2 External Parasites of Poultry). In backyard flocks, the painting of perches and woodwork with sump-oil or creosote and removing and disposing of wood and rubbish from yards is usually an effective method of control.
(e) *Staphylococcus infections The bacterium Staphylococcus aureus is widespread in the environment and causes a variety of opportunistic infections in poultry, especially in the tropics. These include foot abscesses, infections of joint membranes and dermatitis of combs and wattles.
These infections may be treated with suitable antibiotics in the feed. Badly-infected birds are best removed and destroyed, as full recovery does not usually occur. The premises should be disinfected.
(f) Infectious coryza Infectious coryza is caused by a small bacterium Haemophilus gallinarum, which mainly infects growing and laying fowls under conditions of poor hygiene, ventilation and nutrition. Symptoms are discharge from the eyes and nostrils, a swollen face, a drop in egg production and sometimes diarrhoea. It is a chronic disease, which can result in mortalities when complicated with other infectious agents. Infected birds should be culled, as they may remain carriers for several months after infection. Preventative measures include rearing growers away from older birds, culling of carrier birds and improved management.
(g) Chronic respiratory disease (CRD) CRD is caused by Mycoplasma gallisepticum. Its symptoms are sniffling, sneezing and depressed egg production in chickens and sinusitis in turkeys. Its severity often depends on the concurrent presence of other diseases. Both turkeys and fowls of all ages can be infected. This disease is transmitted by inhaling infected air droplets, through eggs to the next generation, or by mechanical means, such as boots and equipment. The organism will die in a day or two when pens are empty, but recovered birds may remain carriers for some time. CRD may be treated with specific antibiotics and vitamin supplements in the feed if only a few birds are involved.
Another bacterium of this group, Mycoplama synoviae, causes subclinical upper respiratory tract infection and may be involved in air sacculitis associated with Newcastle disease and infectious bronchitis. Consult your veterinarian for antibiotic recommendations for these diseases. Vaccines are available for both of them.
(h) *Fowl cholera All domestic poultry are susceptible to this highly infectious disease, caused by the bacterium Pasteurella multocida. Fowl cholera may be deadly, or may linger in infected birds. Symptoms are variable and include respiratory problems and diarrhoea. It is spread through the flock by contaminated water, in droppings and in nasal discharges. All infected birds should be culled and burned. The disease can be treated with a number of antibiotics or sulphonamide drugs. It can be prevented by good management and vaccination.
© Northern Territory Government Page 2 of 6 (i) *Tuberculosis (Mycobacterium avium) Rarely found in young chicks, this infection is a "wasting" disease of all domestic poultry, canaries, parrots, pigeons and wild birds kept in captivity. Avian tuberculosis may be transmitted to humans, cattle and pigs.
Symptoms are not specific and may include gradual loss of weight, diarrhoea, lameness, general weakness and eventually, death.
Treatment is not recommended. All infected birds should be culled and burned. The premises should be cleaned with a phenolic disinfectant or lime and then left for two years before introducing a new flock. Notify the Department of Resources if you suspect tuberculosis in your poultry.
FUNGAL DISEASESAs all domestic poultry, wild birds, other animals and humans can be infected by fungi, take great care when handling infected birds. Transmission occurs by inhaling fungal spores from sick birds, contaminated litter or feed.
(a) *Aspergillosis The most common fungal disease in birds is Aspergillus fumigatus, which causes pneumonia or enteritis in all age groups, especially in the presence of other infections.
Treatment is not recommended. Infected birds should be culled and burned. All mouldy litter should be removed and burned and the pens should be sprayed with 1% copper sulphate.
(b) *Candidiasis or thrush Candidiasis is another common fungal disease, which is found in younger age groups of all domestic poultry. It usually affects the mouth and crop, with sour-smelling crop content. It may also cause diarrhoea. It primarily affects stressed birds. Check for unsanitary conditions, overcrowding and coccidiosis. Treat with nystatin to provide effective control.
PROTOZOAN DISEASES(a) *Coccidiosis Coccidiosis is one of the most common diseases of poultry. It is caused by a number of species of protozoa called coccidia. Fowls, turkeys, ducks and geese are all affected. However, coccidia are host-specific, so fowls are not affected by duck coccidia and vice versa.
The disease usually affects birds over three weeks of age. The symptoms include ruffled feathers, drooping wings, pale combs and diarrhoea, sometimes streaked with blood. Most losses occur in young birds, but adult birds can also be affected. Large numbers of chickens may die suddenly without apparent symptoms.
The coccidia live in the intestine or caecum of the bird and pass out through the droppings. They become infective in damp surroundings and are spread from bird to bird when infected droppings are eaten. Coccidia may survive for long periods in the litter.
Good management will help prevent serious outbreaks of coccidiosis. If birds are denied access to droppings, the life cycle will be broken. This is achieved when birds are raised on wire. Damp litter around water troughs will allow coccidia to become infective.
Medication in feed is often necessary to prevent outbreaks of coccidiosis. Young birds raised on the ground should be routinely treated with a coccidiostat. As the wet season provides ideal conditions for coccidia to become infective, medication is recommended at that time.
© Northern Territory Government Page 3 of 6 (b) *Blackhead The protozoon that causes this disease is Histomonas meleagridis. Both young fowls and turkeys are affected by this protozoon but turkeys are far more susceptible and are more likely to contract this disease when run with poultry than when run on their own. Histomonads live largely in the caecum (blind gut) and invade other organs from there. Symptoms of blackhead include a drooped and huddled appearance, dark colouration of the head, shrunken comb and wattles and yellowish diarrhoea.
Living in the caecum places the histomonads in contact with the caecal worm (Heterakis gallinae) and the eggs of the worm become infected with the protozoa. Blackhead is transmitted when birds eat droppings containing these infected worm eggs.
Drugs are available to treat blackhead. To prevent re-infection, control caecal worms at the same time with good management. Turkeys and fowls should not be run together.
(c) Trichomoniasis Trichomoniasis is caused by Trichomonas gallinae. It is a disease of the upper digestive tract. It has been found in pigeons, doves and kites in the NT but may invade hens and turkeys if they drink infected water or eat infected feed. Affected pigeons will go off-feed, appear ruffled, become emaciated and die, with a green yellow fluid dripping from the beak.
VIRAL DISEASESViral diseases are the most common cause of losses, not only in large commercial flocks, but also in backyard chickens. Mostly, they do not respond to drug therapy. Treatment relies on supportive measures. Prevention and control relies on vaccination where this is effective, or by limiting exposure to infected birds. If a secondary bacterial infection is also present, antibiotics may reduce the severity of an outbreak.
(a) *Marek's disease (MD) This disease usually affects birds two to five months old and causes lymphoid tumours. Symptoms vary according to the position of the tumours. Usually the nerves are affected and spastic paralysis occurs either in the legs, wings or neck. The virus of MD can remain infective for many months in litter or dry feathers. MD is prevented very effectively by vaccinating day-old chicks. Buy only vaccinated chicks.
(b) Lymphoid leucosis This disease is normally found in chickens more than four months old. They pick it up in the first few weeks of their life, or from the mother which, if affected, passes leucosis through the egg. The tumours develop slowly;
birds become sickly, pale and thin, and often have an enlarged abdomen.
There is no known effective treatment for leucosis, nor are there any vaccines available. Affected birds should be culled from the flock.