EXPERIMENTAL INFECTION WITH MURRAY VALLEY ENCEPHALITIS VIRUS. PIGS, CATTLE, SHEEP, DOGS, RABBITS, MACROPODS AND CHICKENS

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Abstract
A tool of 142 young animals including 10 domestic and 14 feral pigs, 12 Hereford calves, 12 crossbred and 24 Merino lambs, 11 dogs, 8 domestic and 16 feral rabbits, 14 Grey kangaroos, 9 Agile wallabies and 12 chickens was exposed to infection with 4 strains of Murray Valley encephalitis virus (MVE), mainly using orally infected Culex annulirostris mosquitoes. In terms of their viraemic response, the animals were grouped into high (Grey kangaroos, rabbits), moderate (pigs, dogs, chickens) and low (calves, lambs, Agile wallabies). Recipient Cx annulirostris induced to bite these animals 1–7 d post-inoculation exhibited infection rates up to 95% but usually were much lower. Some animals in which virus was not detected by intracerebral inoculation of suckling mice were capable of infecting up to 5% Cx annulirostris. Haemagglutination-inhibiting antibody (HI) was of high titre and persistent in rabbits und Grey kangaroos but moderated in others, e.g., cattle, sheep, Agile wallabies to be transient and of low titre. Cattle and Merino lambs were often completely non-responsive. This study increases the range of vertebrates that could be considered as maintenance or amplifying hosts of MVE and, on the basis of their HI antibody responses, evaluates them as potential sentinels of infection in Australia.