Encephalomyocarditis virus infection in an Italian zoo

Abstract

A fatal Encephalomyocarditis virus (EMCV) infection epidemic involving fifteen primates occurred between October 2006 and February 2007 at the Natura Viva Zoo. This large open-field zoo park located near Lake Garda in Northern Italy hosts one thousand animals belonging to one hundred and fifty different species, including various lemur species. This lemur collection is the most relevant and rich in Italy. A second outbreak between September and November 2008 involved three lemurs. In all cases, the clinical signs were sudden deaths generally without any evident symptoms or only with mild unspecific clinical signs. Gross pathologic changes were characterized by myocarditis (diffuse or focal pallor of the myocardium), pulmonary congestion, emphysema, oedema and thoracic fluid. The EMCV was isolated and recognized as the causative agent of both outbreaks. The first outbreak in particular was associated with a rodent plague, confirming that rats are an important risk factor for the occurrence of the EMCV infection.

Figure 1

Thoracic cavity of a Callithrix jacchus that died during the first outbreak. Sero-hemorragic transudate

Figure 2

Heart of a Lemur catta that died during the first outbreak. Some typical white foci of necrosis in the myocardium

Figure 3

Vero cells culture. a) Negative control: uninfected cell monolayer. (20× magnification). b) Evident cytopathic effect due to EMCV, 72 hours after the infection. (20× magnification).

Figure 4

Electromicrograph. EMCV particles using IEM. (NaPT 2%. Bar = 100 nm).

Figure 5

Histological examination of myocardium. a) Severe myocarditis characterized by an interstitial infiltration of lymphocytes and neutrophilic granulocytes. (Hematoxylin-eosin, 40× magnification) b) EMCV - immunopositive myocardiocytes using immunohistochemistry. (100× magnification).