A highly divergent Encephalomyocarditis virus isolated from nonhuman primates in Singapore

Abstract

BackgroundIn 2001 and 2002, fatal myocarditis resulted in the sudden deaths of four, two adult and two juvenile, orang utans out of a cohort of 26 in the Singapore Zoological Gardens.MethodsOf the four orang utans that underwent post-mortem examination, virus isolation was performed from the tissue homogenates of the heart and lung obtained from the two juvenile orang utans in Vero cell cultures. The tissue culture fluid was examined using electron microscopy. Reverse transcription and polymerase chain reaction with Encephalomyocarditis virus (EMCV)-specific primers targeting the gene regions of VP3/VP1 and 3D polymerase (3Dpol) confirmed the virus genus and species. The two EMCV isolates were sequenced and phylogenetic analyses of the virus genes performed. Serological testing on other animal species in the Singapore Zoological Gardens was also conducted.ResultsElectron microscopy of the two EMCV isolates, designated Sing-M100-02 and Sing-M105-02, revealed spherical viral particles of about 20 to 30 nm, consistent with the size and morphology of members belonging to the family Picornaviridae. In addition, infected-Vero cells showed positive immunoflorescence staining with antiserum to EMCV. Sequencing of the viral genome showed that the two EMCV isolates were 99.9% identical at the nucleotide level, indicating a similar source of origin. When compared with existing EMCV sequences in the VP1 and 3Dpol gene regions, the nucleotide divergence were at a maximum of 38.8% and 23.6% respectively, while the amino acid divergence were at a maximum of 33.9% and 11.3% respectively. Phylogenetic analyses of VP1 and 3Dpol genes further grouped the Sing-M100-02 and Sing-M105-02 isolates to themselves, away from existing EMCV lineages. This strongly suggested that Sing-M100-02 and Sing-M105-02 isolates are highly divergent variants of EMCV. Apart from the two deceased orang utans, a serological survey conducted among other zoo animals showed that a number of other animal species had neutralizing antibodies to Sing-M105-02 isolate, indicating that the EMCV variant has a relatively wide host range.ConclusionsThe etiological agent responsible for the fatal myocarditis cases among two of the four orang utans in the Singapore Zoological Gardens was a highly divergent variant of EMCV. This is the first report of an EMCV infection in Singapore and South East Asia.

Encephalomyocarditis virus infection in Macaca sylvanus and Hystrix cristata from an Italian rescue centre for wild and exotic animals

“…Unfortunately, to avoid causing unnecessary and potentially damaging stress, no blood samples were collected from the surviving animals to verify their seropositivity or their status of persistently infected, but EMCV is known to be a potential issue for other zoological park animals as it may involve several species [2, 3, 7, 8]. …”

“…A probable third EMCV type has been isolated from orang utan in 2001 and 2002 [2]. It is spread worldwide and infects a huge range of vertebrate hosts with zoonotic potential for humans [1, 3, 4].…”

“…Several lethal outbreaks have been described in zoos in Australia and the USA [2, 7, 8] and in Northern Italy [3]. …”

Encephalomyocarditis virus in a captive Malayan tapir (<i>Tapirus indicus</i>)

“…Since the toxicology lab did not find any of the ionophores that could be involved in Belgium (maduromicin, narasin, lasalocid, monensin, salinomycin, semduramicin) in the liver tissue, this possibility was also excluded. Outbreaks of encephalomyocarditis virus are notorious for their suddenness and many cases occur as asymptomatic deaths both in zoo mammals and in young domestic pigs (Wells et al, 1989;Reddacliff et al, 1997;Gelmetti et al, 2006;Vogelnest et al, 2006;Canelli et al, 2010;Yeo et al, 2013). In our case, the Malayan tapir died suddenly without any predictive symptoms.…”

“…There is no descriptive report on encephalomyocarditis virus (EMCV) in tapirs in the international literature, but the occurrence of this disease is mentioned in the Tapir (Tapiridae) Care Manual of the Association of Zoos and Aquariums (2013) and two cases were mentioned briefly by Janssen et al (1996). Yet, several publications exist of EMCV in other mammal species in zoological collections (Wells et al, 1989;Reddacliff et al, 1997;Vogelnest et al, 2006;Canelli et al, 2010;Liu et al, 2013;Yeo et al, 2013). The present report describes the gross necropsy, histopathology and ancillary laboratory examinations of a fatal EMCV infection in a young captive Malayan tapir.…”