Identification of Opossums (Didelphis virginiana) as the Putative Definitive Host of Sarcocystis neurona

Abstract

Sarcocystis neurona is an apicomplexan that causes equine protozoal myeloencephalitis (EPM) in North and South America. Horses appear to be an aberrant host, because the merozoites continually divide in the central nervous system, without encysting. The natural host species has not previously been identified. The small subunit ribosomal RNA (SSURNA) gene of S. neurona was compared to those of Sarcocystis muris, Sarcocystis cruzi, Toxoplasma gondii, and Cryptosporidium parvum to identify a unique region suitable for a species-specific amplification primer. The S. neurona SSURNA primer was used in a polymerase chain reaction (PCR) assay for the purpose of identifying this organism in feces and intestinal digest of wildlife specimens. Sporocysts were isolated from 4 raccoons (Procyon lotor), 2 opossums (Didelphis virginiana), 7 skunks (Mephitis mephitis), 6 cats (Felis catus), 1 hawk (Accipiter sp.), and 1 coyote (Canis latrans). The S. neurona SSURNA PCR assay and a control PCR assay using protist-specific primers were applied to all sporocyst DNA samples. All sporocyst DNA samples tested positive on the control assay. The SSURNA PCR assay yielded a 484-bp product only when applied to opossum samples. The SSURNA gene of both opossum sporocyst samples was sequenced to determine its relationship to the S. neurona SSURNA gene. The sequence had 99.89% similarity with S. neurona. This suggests that opossums are the definitive host of S. neurona.

Temporal Association Between Land-Based Runoff Events and California Sea Otter (Enhydra Lutris Nereis) Protozoal Mortalities

“…Although infection is most often asymptomatic, death due to disseminated disease can occur in immunocompromised humans, and acute infection during pregnancy can result in abortion or congenital disease in the fetus (Jones et al, 2003). Sarcocystis neurona is not known to infect humans but is one of the main causes of equine protozoal myeloencephalitis (EPM), resulting in substantial morbidity and mortality of affected animals (Fenger, 1997).…”

“…Infection of sea otters with T. gondii and S. neurona has been puzzling because the only recognized definitive hosts of these parasites are felids (domestic and wild cats) and opossums (Didelphis virginiana and D. albiventris), respectively (Dubey et al, 1970;Fenger et al, 1995). These terrestrial mammals are the only species capable of shedding infective oocysts (Toxoplasma) or sporocysts (Sarcocystis) in their feces, which are the environmentally resistant stages of the parasites.…”

Frequency of antibodies against Sarcocystis neurona and Neospora caninum in domestic cats in the state of Bahia, Brazil

“…Marsupials of the genus Didelphis are definitive hosts (DH) for S. neurona; D. virginiana is the DH in North America (FENGER et al, 1995), and D. albiventris has been identified as a DH in South America (DUBEY et al, 2001a). Domestic cats (Felis catus) were the first intermediate hosts of S. neurona identified experimentally (DUBEY et al, 2000).…”

Equine Protozoal Myeloencephalitis: An Updated Consensus Statement with a Focus on Parasite Biology, Diagnosis, Treatment, and Prevention

“…The opossum Didelphis virginiana is the definitive host for S. neurona in North America 12. As well, South American opossums can act as definitive hosts for S. neurona in the southern hemisphere 13.…”