Epidemiology

Serological surveys show that the infection is common in goats, with a level of prevalence of around 70% in adult goats of US origin and of some countries of Europe (for example, France and Norway). Comparison of detections of the virus by either ELISA serology or polymerase chain reaction (PCR) show greater sensitivity but lower specificity for the PCR at the present time, although the PCR assay for CAEV and visna virus detection is still in its infancy.

The higher incidence of goats infected with CAEV, compared with visna virus in sheep, is probably due to the common practice in the dairy goat industry of feeding kids with pooled colostrum and milk from dairy mothers. In contrast, pooled milk is rarely fed to lambs. This enhanced transmission in dairy goats may therefore explain the high prevalence of CAEV infection in goats in Western Europe, Australia and North America, and the lack of such infections in African countries that have no dairy goat operations based on Western models. This marked difference in prevalence of infection between dairy and nondairy goats was also observed in Australia, where it was reported that Angora goats were much less infected than dairy goats.

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