Results of an epidemiological investigation on viral arteritis in France and some other European and African countries.

An original microplate seroneutralization technique was developed in order to study the existence of antibodies against equine viral arteritis. The technique involves a high amount of complement, and has allowed to demonstrate antibodies in 18.5% out of 4,037 horses examined. Titers varied not or little during periods as long as 6 years. Among 3,324 sera samples from French horses, a 15.2% frequency of antibodies was shown. The infection level was not very different between breeds, which is different from results obtained in the U.S.A. with another technique. The infection level increased regularly from 1 to 20 years of age, but, for a constant age, the percentage decreased with the year of birth, between 1950 and 1970. Eight individual infection cases have been identified between 1966 and 1974. It seems that more often the disease occurs without clinical symptoms, or sometimes manifests itself through sporadic abortion. Serological marks of infection have been found at variable levels in all the countries of Europe and Africa investigated. In Africa, a higher level (37.1% among 468 sera) was observed.