Variola caprina (goat pox) is a
contagiousviral disease caused by Goatpox virus, a
pox virus that affects
goats. The virus usually spreads via the
respiratory system, and sometimes spreads through abraded skin. It is most likely to occur in crowded stock. Sources of the virus include cutaneous lesions,
saliva, nasal secretions and
faeces. There are two types of the disease: the papulo-vesicular form and the nodular form (stone pox). The incubation period is usually 8–13 days, but it may be as short as four days.
It is thought the same virus spreads sheep pox, to which European sheep breeds are highly susceptible. The virus may be present in dried scabs for up to six months.[1]
In endemic areas the morbidity rate is 70–90% and the mortality rate is 5–10%. The mortality rate may reach nearly 100% in imported animals. Resistant animals may show only a mild form of the disease, which may be missed as only a few lesions are present, usually around the
ears or the
tail.
Spread
Goat pox is found in the part of
Africa north of the equator, the
Middle East,
Central Asia and
India. It may be spread between animals by:
Direct contact
Indirect transmission by contaminated implements, vehicles or products such as litter or fodder
Indirect transmission by insects (mechanical vectors).
Contamination by
inhalation, intradermal or subcutaneous inoculation, or by respiratory, transcutaneous and transmucosal routes
Eruption of
skin lesions after a few days. These lesions first develop into
vesicles,
pustules and then hairy and dark-colored
scabs. They may take up to 6 weeks to heal. Scabs are often found in hair-free or wool-free areas such as the udders, perineum, inguinal area, scrotum, muzzle, eyelids and axillae.
Appearance on
udders and
teats of small, red spotty areas which may form scabs. The orifices of the teats may become infected and cause
mastitis.
Papules become a white-grey colour, desiccate and form crusts that are easy to remove
Papules are 0.5–1.5 cm in diameter and are hard to the touch. The papules become depressed, gray and
necrotic, and may be surrounded by an area of
hyperemia.
Rarely, papules may transform into large, fluid-filled vesicles. After the vesicles rupture, a thick crust covers the lesions
Nodular form
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.