Isolation of Sarcocystis neurona from an opossum (Didelphis albiventris) in Argentina

Abstract

Sarcocystis neurona is an Apicomplexan parasite which affects awide range of animal hosts. This protozoan is the main cause ofequine protozoal myeloecephalitis (EPM) inWestern Hemispherehorses. The parasite reproduces sexually in the intestine ofdefinitive hosts (DH) and asexually in tissues of intermediate andaberrant hosts. The geographical distribution of S. neurona isrelated with the distribution its definitive hosts, the opossumsDidelphis virginiana and D. albiventris. A recent serological studyconducted in Argentinean horses using S. neurona antigenrevealed an overall seroprevalence of 26.1%. However, the parasitehas not been isolated in Argentina. Tissues from an opossum (D.albiventris) hunted by dogs in a farm from the central region ofBuenos Aires province were collected. Horses raised in the farmshowed a 50% (10/20) S. neurona seroprevalence. One seropositivehorse developed neurological signs and evidenced clinicalimprovement after a 2 month treatment with Ponazuril. A completenecropsy of the opossum was conducted and the intestinalmucosal scraping was subjected to a parasitological study withsucrose solution. A high amount of Sarcocystis spp. oocysts/sporocystswere observed (Fig. 1). DNA was extracted from concentratedoocysts with a commercial kit (ZR Fecal DNA, ZymoResearch). The sample was identified as S. neurona by specificPCR-restriction fragment length polymorphism (RFLP) and bysequencing of a fragment of the 18S rRNA gene. Approximately 5 x105 oocysts were subjected to a pepsin-HCl digestion followed bya physical disruption. Released sporozoites were used to infectfresh BM cell cultures, maintained by 3 passages during 2 monthsand further preserved in liquid nitrogen. This study represents thefirst isolation of S. neurona in Argentina. Further studies will beconducted in order to identify antigen expression as well as tocompare genetic characteristics between the isolated strain andreference strains.