The protozoon Sarcocystis aucheniae is the causative agent of South American camelid (SAC) sarcocystosis. Infections are characterized by the presence of cysts in muscles which are in size and appearance similar to rice grains. As consumption of insufficiently cooked infected meat produces gastroenteritis, cyst-containing SAC meat is confiscated by sanitary authorities or depreciated with serious economic consequences for SAC breeders. In this work, a duplex semi-nested PCR was designed to simultaneously detect parasite and llama DNA in host blood samples. Species-specific regions of S. aucheniae 18S rRNA gene and Lama glama 16S mitochondrial gene were amplified, yielding bands of 583 and 257 bp, respectively, and separated by gel electrophoresis. The method proved to be highly sensitive, with a detection limit lower than one parasite per milliliter blood, and the inclusion of primers to detect llama-specific DNA resulted useful as a methodological control. Blood samples collected from llamas of Argentina and Bolivia (n = 225) were analyzed using this method, and 18.7 % resulted positive for S. aucheniae. No correlation was found between PCR results and llama age, sex or the finding of macroscopic cysts in meat after slaughter. Lack of molecular detection in the blood of some llamas harboring macrocysts suggests that parasite circulation in the bloodstream after encystment is under the detection threshold of the test or even absent, while PCR positive results in cyst-infested animals suggests that prior exposure to the parasite does not impede subsequent infections. The described method can be useful to detect active foci of infection, to assess the effectiveness of parasiticide treatments, and for the surveillance and tracing of definitive hosts.

Sarcocystis aucheniae is a coccidian parasite that produces macroscopic sarcocysts in South American camelid (SAC) muscles and causes a disease known as SAC sarcocystosis. This parasitosis hampers the commercialization of llama and alpaca meat, a vital economic activity in the Andean regions. No control or prevention methods are available, and diagnosis is based on postmortem visual inspection of carcasses. The aim of this study was to identify S. aucheniae B-cell epitopes suitable for the development of diagnostic methods for SAC sarcocystosis. To this end, sarcocyst immunoreactive protein bands were analyzed via mass spectrometry, and proteins in each band were identified in silico by searching in the parasite transcriptome. Five highly antigenic, hydrophilic B-cell epitopes, predicted not to cross-react with antibodies against other coccidia, were selected for future development of peptide-based serological tests. In addition, conserved domains present in the identified proteins allowed us to unravel metabolic pathways and mechanisms active in the parasitic stages present in sarcocysts, including aerobic respiration, antioxidant activity, signal transduction, protein synthesis and processing, and host–pathogen interactions. This study provides novel information on the biology of S. aucheniae, as well as new protein sequences that can be used for the development of diagnostic tests and chemotherapeutic approaches for SAC sarcocystosis.