Avian Pox
Sinonim : Fowl Pox (FP), Pox
Introduction
Avian pox is a relatively slow-spreading viral disease in birds, characterized by wart-like nodules on the skin and diphtheritic necrotic membranes lining the mouth and upper respiratory system. It has been present in birds since the earliest history. Mortality is not usually significant unless the respiratory involvement is marked. The disease may occur in any age of bird, at any time.
Avian pox is caused by a virus of which there are at least three different strains or types; fowl pox virus, pigeon pox virus and canary pox virus. Although some workers include turkey pox virus as a distinct strain, many feel that is identical to fowl pox virus.
Each virus strain is infective for a number of species of birds. Natural occurring pox in chickens, turkeys and other domestic fowl is considered to be caused by fowl pox virus.
Transmission
The virus is present in lesions and in desquamated scabs. It is resistant to environmental factors and persists in the environment for many months. It usually infects birds through minor abrasions. Mechanical transmission occurs by cannibalism. Some mosquitoes can transmit the virus from infected to uninfected birds. The virus can be also transmitted by injury to the skin. Since fowl pox usually spreads slowly, a flock may be affected for several months. The course of the disease in the individual bird takes three to five weeks. Affected young birds are retarded in growth. Laying birds experience a drop in egg production. Birds of all ages that have oral or respiratory system involvement have difficulty eating and breathing. The disease manifests itself in one or two ways, cutaneous pox (dry form) or diphtheritic pox (wet form).
Antemortem findings: Two forms of lesions are recognized, - the cutaneous (dry form) and the diphtheric (wet form)
Cutaneous form
1. Low mortality
2. Lack of flock vigour and weight loss
3. A mild to moderate loss in egg production
4. Scabby lesions on the head, neck and unfeathered parts of the skin
Diphtheric form
1. Mortality low to moderate
2. Difficult breathing
3. Nasal and ocular discharge
Postmortem findings: The following stages of the pox lesions papules, vesicles and pustules may be observed.
Cutaneous lesions
1. Papules are light coloured nodules.
2. Vesicles and pustules are raised and commonly yellow.
Diphtheric lesions
3. Buff to yellow plaques on mucous membranes in the mouth oesophagus and upper respiratory tract
4. Occlusion of trachea, and death due to asphyxiation
Histopathology shows characteristic intracytoplasmic inclusion bodies (Bollinger bodies) in the infected epithelium.
Treatment
There is no treatment for fowl pox. Disease control is accomplished best by preventative vaccination since ordinary management and sanitation practices will not prevent it. Several kinds of vaccines are available and are effective if used properly.
Vaccination of broilers is not usually required unless the mosquito population is high or infections have occurred previously. The chicks may be vaccinated as young as one day of age by using the wing-web method and using a one needle applicator. All replacement chickens are vaccinated against fowl pox when the birds are six to ten weeks of age. One application of fowl pox vaccine results in permanent immunity.
(Source: vet-zone)
Introduction
Avian pox is a relatively slow-spreading viral disease in birds, characterized by wart-like nodules on the skin and diphtheritic necrotic membranes lining the mouth and upper respiratory system. It has been present in birds since the earliest history. Mortality is not usually significant unless the respiratory involvement is marked. The disease may occur in any age of bird, at any time.
Avian pox is caused by a virus of which there are at least three different strains or types; fowl pox virus, pigeon pox virus and canary pox virus. Although some workers include turkey pox virus as a distinct strain, many feel that is identical to fowl pox virus.
Each virus strain is infective for a number of species of birds. Natural occurring pox in chickens, turkeys and other domestic fowl is considered to be caused by fowl pox virus.
Transmission
The virus is present in lesions and in desquamated scabs. It is resistant to environmental factors and persists in the environment for many months. It usually infects birds through minor abrasions. Mechanical transmission occurs by cannibalism. Some mosquitoes can transmit the virus from infected to uninfected birds. The virus can be also transmitted by injury to the skin. Since fowl pox usually spreads slowly, a flock may be affected for several months. The course of the disease in the individual bird takes three to five weeks. Affected young birds are retarded in growth. Laying birds experience a drop in egg production. Birds of all ages that have oral or respiratory system involvement have difficulty eating and breathing. The disease manifests itself in one or two ways, cutaneous pox (dry form) or diphtheritic pox (wet form).
Antemortem findings: Two forms of lesions are recognized, - the cutaneous (dry form) and the diphtheric (wet form)
Cutaneous form
1. Low mortality
2. Lack of flock vigour and weight loss
3. A mild to moderate loss in egg production
4. Scabby lesions on the head, neck and unfeathered parts of the skin
Diphtheric form
1. Mortality low to moderate
2. Difficult breathing
3. Nasal and ocular discharge
Postmortem findings: The following stages of the pox lesions papules, vesicles and pustules may be observed.
Cutaneous lesions
1. Papules are light coloured nodules.
2. Vesicles and pustules are raised and commonly yellow.
Diphtheric lesions
3. Buff to yellow plaques on mucous membranes in the mouth oesophagus and upper respiratory tract
4. Occlusion of trachea, and death due to asphyxiation
Histopathology shows characteristic intracytoplasmic inclusion bodies (Bollinger bodies) in the infected epithelium.
Treatment
There is no treatment for fowl pox. Disease control is accomplished best by preventative vaccination since ordinary management and sanitation practices will not prevent it. Several kinds of vaccines are available and are effective if used properly.
Vaccination of broilers is not usually required unless the mosquito population is high or infections have occurred previously. The chicks may be vaccinated as young as one day of age by using the wing-web method and using a one needle applicator. All replacement chickens are vaccinated against fowl pox when the birds are six to ten weeks of age. One application of fowl pox vaccine results in permanent immunity.
(Source: vet-zone)
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