Getah virus as an equine pathogen.

Getah virus is a member of the genus Alphavirus in the family Togaviridae and has been frequently isolated from mosquitoes. Seroepizootiologic studies indicate that the virus is mosquito-borne and widespread, ranging from Eurasia to southeast and far eastern Asia, the Pacific islands, and Australasia. The natural host animal of the virus was not known until the first recognized occurrence of Getah virus infection among racehorses in two training centers in Japan in 1978. Outbreaks of clinical disease due to Getah virus infection occur infrequently, and only one outbreak has been reported outside Japan; this was in India in 1990. Clinical signs of the disease are mild and nonlife-threatening and are characterized by pyrexia, edema of the hind limbs, swelling of the submandibular lymph nodes, and urticarial rash, as reported in the 1978 epizootic. The morbidity was 37.9% (722 of 1903 horses) in one training center, with 96% of 722 affected horses making a full clinical recovery within a week without any significant sequelae. Antibodies against Getah virus were detected in 61.2% (172 of 281) and 55.8% (254 of 455) of horses at two training centers, respectively. Virus isolation can be attempted in VERO, RK-13, BHK-21, and many other cell lines as well as in suckling mouse brain. Blood plasma collected from suspect cases of infection at the onset of pyrexia is the specimen of choice. A diagnosis of Getah virus infection can also be confirmed serologically based on testing acute and convalescent phase sera by using SN, CF, HI, and ELISA tests. An inactivated vaccine is available for the prevention and control of Getah virus infection in horses in Japan.