Sheep and Goat Pox

Sheep (Ovine pox or Variola ovina) and Goat Pox (Variola capra) are viral diseases of sheep and goats characterized by fever, generalized papules or nodules, vesicles (rarely) and internal lesions (particularly in the lungs).

Etiology

Sheep pox is caused by sheep pox virus and goat pox is caused by goat pox virus, these viruses are highly host specific, Kenya sheep and goat virus infect both sheep and goat equally all are member of genus capripox virus, belongs to family pox viridae.

Epidemiology

• The disease is endemic in Africa northern part of the Equator, Middle East, Turkey, Iran, Iraq, Afghanistan, Pakistan, India, Nepal, parts of the Peoples in Republic of China and Bangladesh.
• The Morbidity and mortality vary with the breed of the host and the strain of the virus.
• Mortality may be up to 50% in a fully susceptible flock, and as high as 100% in young animals.
• Imported breeds such as merinos highly susceptible than native breeds.
• Mild infections are common in indigenous breeds; however, symptoms may be more severe in kids or lambs, stressed animals, animals that have concurrent infections, or animals from areas where pox has not occurred for some time.

Transmission

• Direct contact with an infected animals and contaminated equipment.
• Inhalation of aerosols containing virus.
• Stable flies (Stomoxys calcitrans) may transmit the viruses mechanically.

Clinical manifestation

Sheep

• Incubation period is 12- 14 days.
• The disease occur in two forms namely; malignant and benign form.
• Malignant form is common in young animals.
• The symptoms include high fever, marked depression; prostration and serous or mucopurulent discharge from eye and nose, affected lamb may die during this stage development of typical pox lesions.
•  Some animals shows conjunctivitis, rhinitis, lymphadenopathy, anorexia and depression, the initial rise in temperature is followed by development of macules (small circumscribed areas of hyperaemia), which are most obvious on unpigmented skin and then papules (hard swellings 0.5 and 1 cm in diameter), which may cover the entire body or may be restricted to the groin, axilla and perineum.
• Papules on the mucous membranes of the eyes and nose ulcerate, so the discharge becomes mucopurulent, the mucosa of the mouth, anus and prepuce or vagina becomes necrotic.
• Breathing may become laboured and noisy due to pressure on the upper respiratory tract from the swollen retropharyngeal lymph nodes, due to the developing lung lesions.
• Secondary pneumonia is common and abortion is rare.
• The benign form is common in adult, only skin lesion occur, particularly under the base of the tail and ear region. There is no systemic reaction.
• Goat pox in sheep is more severe than sheep pox, the lesions occur on the lips, oral mucosa, teat and udder.

Goat

• Symptoms are similar to sheep pox.
• Young kids suffer from systemic disease, the pox lesions spread generally all over the skin, alimentary and respiratory mucosa.
• Adult goat may have a systemic disease and extensive lesion, but symptoms are usually mild.

Necropsy Finding

• The lungs often contain discrete congested or edematous lesions or hard white nodules. Nodules in the lungs can be up to 5cm in diameter.
•  Pale foci are sometimes present on the surface of the kidney and liver.

Sample collection

• Live animals– whole blood during peak temperature, scab 10% glycerol saline and paired sera sample.
• Dead animal–  skin lesion, lung lesion and lymph node.

Diagnosis

• Based on clinical symptoms and lesion.
• Virus isolation in tissue culture of ovine or caprine origin or lamb kidney cells.
• Detection of  viral antigen by PCR, AGID and FAT.
• Detection of antigen by ELISA, the samples to be collected within first week of occurrence of clinical signs.
• Detection of antibody by virus neutralization test, AGID, IFAT, Western blot analysis and ELISA.

Differential diagnosis

• Contagious ecthyma
• Blue tongue

Treatment

• Administration of antibiotics to control secondary infection and good nursing care are recommended.
• Infection results in good immunity.

Prevention

• Vaccination is the best method to prevent the disease in susceptible animals.
• The live attenuated sheep pox vaccine is administered above 3 months of age in healthy sheep, and revaccination is done every year in endemic area.

Control

• Elimination of infected and exposed animals by slaughter.
• Proper disposal of cadaver and contaminated product by burning or deep burial.
• Cleaning and disinfection of contaminated premises and equipment with 2% sodium hypochlorite or 2% phenol.
• If the disease spread in extensively in endemic area mass vaccination with restriction of animal movement is advisable.
• Quarantine the infected area is required to prevent the spread of the disease.
• Isolation of infected herds and sick animals for at least 45 days after recovery is recommended.