Sheep pox and goat pox
Aetiology Epidemiology Diagnosis Prevention and control References
AETIOLOGY
Classification of the causative agent
Virus family Poxviridae, genus Capripoxvirus
Resistance to physical and chemical action
Temperature: Susceptible to 56°C/2 hours; 65°C/30 min pH: Susceptible to highly alkaline or acid pH Chemicals: Sensitive to ether (20%), chloroform, and formalin (1%) Disinfectants: Inactivated by phenol (2%) in 15 min. Sensitive to detergents, e.g. sodium dodecyl sulphate Survival: Can survive for many years in dried scabs at ambient temperatures. Virus remains viable in wool for 2 months and in premises for as long as 6 months EPIDEMIOLOGY
- Morbidity rate: Endemic areas 70-90%
- Mortality rate: Endemic areas 5-10%, although can approach 100% in imported animals
Hosts
- Sheep and goats (breed-linked predisposition and dependent on strain of capripoxvirus)
Transmission
- Direct contact
- Indirect transmission by contaminated implements vehicles or products (litter, fodder)
- Indirect transmission by insects (mechanical vectors) has been established (minor role)
- Contamination by inhalation, intradermal or subcutaneous inoculation, or by respiratory, transcutaneous and transmucosal routes
Sources of virus
- Cutaneous lesions (crusts, nodules) resulting in aerosols
- Saliva
- Nasal secretions
from sick animals for 1 or 2 months
- Faeces
Occurrence
Sheep pox and goat pox are endemic in most of Africa, the Middle East and Asia
For detailed information on occurrence, see recent issues of World Animal Health and the OIE Bulletin
DIAGNOSIS
Incubation period is up to 21 days. Following contact, incubation period is approximately 12 days, but is shorter than this following intradermal inoculation by insects
Clinical diagnosis
- Subclinical cases
- Clinical cases vary from mild to severe:
- fever, depression, polypnoea
- conjunctivitis, lacrimation, rhinitis, oedema of eyelids, photophobia
- cutaneous eruption beginning with erythematous areas especially noticeable in hair or wool-free parts of the body, such as the perineum, inguinal area, scrotum, udder, muzzle, eyelids and axillae
- lesions evolve into papules
- Papulo-vesicular form
- Papules become a white-grey colour, desiccate and form crusts that are easy to remove
- Rarely, papules may transform into vesicles. After rupture of vesicles, a thick crust covers the lesions
- Nodular form ('stone pox')
- Papules give rise to nodules involving all the layers of the skin and the subcutaneous tissue
- Necrosis and sloughing of the nodules leaves a hairless scar
- In both forms, nodules develop in the lungs causing bronchopneumonia with cough, abundant nasal discharge, depression, anorexia and emaciation
- Animals may recover within 20-30 days
- Death is frequent when complications occur (abortion, which is rare, secondary infections, fly strike, septicaemia, digestive localisation)
Lesions
- Skin lesions: congestion, haemorrhage, oedema, vasculitis and necrosis. All the layers of epidermis, dermis and sometimes musculature are involved
- Lymph nodes draining infected areas: enlargement (up to eight times normal size), lymphoid proliferation, oedema, congestion, haemorrhage
- Pox lesions: on mucous membranes of the eyes, mouth, nose, pharynx, epiglottis, trachea, on the rumenal and abomasal mucosae, and on the muzzle, nares, in the vulva, prepuce, testicles, udder, and teats. Lesions may coalesce in severe cases
- Lung lesions: severe and extensive pox lesions, focal and uniformly distributed throughout the lungs; congestion, oedema, focal areas of proliferation with necrosis, lobular atelectasis. Enlargement, congestion, oedema and haemorrhages of mediastinal lymph nodes
Differential diagnosis
- Bluetongue
- Peste des petits ruminants
- Contagious ecthyma
- Photosensitisation
- Dermatophilosis
- Insect bites
- Parasitic pneumonia
- Caseous lymphadenitis
- Mange (scrabies)
Laboratory diagnosis
Procedures
Identification of the agent
- Cell inoculation and identification by immunofluorescence staining of intracytoplasmic inclusion bodies
- Inhibition of cytopathic effect using positive serum
- Antigen detection ELISA
Lamb testis and goat testis, and goat cells kidney Serological tests
- Virus neutralisation
- Indirect fluorescent antibody test
- Agar gel immunodiffusion
- ELISA
NB!! Differentiation from lumpy skin disease is not possible by serological methods Samples
- Full skin thickness biopsies taken within 1 week of the first appearance of the lesions
- Lesions in the lungs
- Paired sera
PREVENTION AND CONTROL
No treatment
Sanitary prophylaxis
- Isolation of infected herds and sick animals for at least 45 days after recovery
- Slaughtering of infected herd (as far as possible)
- Proper disposal of cadavers and products
- Stringent disinfection
- Quarantine before introduction into herds
- Animal and vehicle movement controls within infected areas
Medical prophylaxis
- There are numerous attenuated virus vaccines delivered by subcutaneous or intradermal route
- The conferred immunity lasts up to 2 years
REFERENCES AND OTHER INFORMATION
- Reference experts and laboratories
- Classified as an OIE List A disease (A100)
- Chapter 2.1.10. in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.
- Terrestrial Animal Health Code
- Other references - see the Index
- World Animal Health .
- Current Animal Health Status (Disease Information)
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Contact : scientific.dept@oie.int