Identifying Sarcocystis spp. infection in goats: a combined morphological, serological, and molecular approach

Domestic goats (Capra aegagrus hircus) are intermediate hosts for three species of Sarcocystis: S. capracanis, S. hircicanis, and S. moulei. The present study aimed to describe and identify Sarcocystis spp. in goat/kid muscles utilizing optical and transmission electron microscopy, a serological method, and PCR-sequencing of individual cysts. Both S. capracanis and S. hircicanis were identified by light and transmission electron microscopy and molecular methods. No macroscopic cysts were detected in any of the examined animals (n = 90, from two Argentinean provinces); only microscopic sarcocysts of Sarcocystis spp. were detected in 17 of 19 adult goats (90%), but in no kids (n = 71) aged 37 to 290 days. Fourteen 18S rRNA and the six coxI sequences from individual cysts highlighted high similarity (99.06-100% and 98.89-99.81%, respectively) with S. capracanis sequences from other regions. Two distinct groups of S. capracanis 18S rRNA sequences with high intra-group identities (99.42-100%) were identified, as well as another sequence that did not group. Each group was integrated from samples of both sampled provinces. Despite relatively extensive differences between these groups of sequences (up to 3.8%), the phylogenetic analyses positioned the three representative sequences all together in a branch with S. capracanis sequences but also containing S. tenella. In addition, one 18S rRNA sequence showed a 100% identity with those of S. hircicanis. Two animals harbor S. capracanis and S. hircicanis cysts. Twelve out of 18 adult goats were seropositive by Sarcocystis spp. IFAT with titers ≤ 100. This is the first report that confirmed the infection and co-infection of S. capracanis and S. hircicanis in domestic goats from Argentina and evidenced a high variability in the 18S rRNA fragment sequences of S. capracanis.