Abstract

Encephalomyocarditis virus (EMCV) is a ubiquitous picornavirus with a worldwide distribution, capable of establishing infection in a vast range of species. Episodes of EMCV-associated fatality have been reported in zoos and national parks around the world, including sporadic cases at Taronga Zoo, Sydney, N.S.W.

An inactivated EMCV vaccine was evaluated by inoculating Barbary sheep (Ammotragus lervia), Indian antelope (Antilope cervicapra), Eastern wallaroo (Macropus robustus) and chimpanzees (Pan troglodytes). A proportion of the vaccinated ungulates were administered a booster vaccination 4 weeks following the initial dose. Neutralizing antibody titres were monitored over a period of 6 months. All vaccinated groups developed significant antibody titres by 1 month that persisted at least 6 months post-vaccination. Boosted animals had significantly higher titres at 3 and 6 months following the initial vaccination compared with animals receiving a single vaccine dose. We recommend this vaccine preparation for the protection of non-domestic species against EMCV.

An immunoperoxidase staining technique to identify EMCV antigen in formalin-fixed specimens was successfully applied to zoo animal tissues. Archival specimens from cases of acute myocarditis were retrieved and subjected to immunohistochemistry. EMCV antigen was identified in the myocardium of two of these retrospective cases. This is the first time immunohistochemistry for EMCV has been described in a diagnostic context for zoo animals, and the first report of EMCV infection in a quokka (Setonix brachyurus). This technique offers an additional method of EMCV diagnosis, especially where tissues suitable for virus isolation are not available.