Detection of Sarcocystis aucheniae in blood of llama by a duplex semi-nested PCR assay and its association with cyst infestation

DECKER FRANCO C; ROMERO S; FERRARI A; SCHNITTGER L; MÓNICA FLORIN-CHRISTENSEN

Congreso; International Congress on Tropical Veterinary Medicine, 2nd Joint AITVM-STVM Meeting; 2018

Sarcocystis aucheniae is the causative agent of South American camelid (SAC) sarcocistiosis. Infections are characterized bythe presence of macroscopic cysts in muscles that resemble to rice grains. Asconsumption of insufficiently cooked infected meat produces gastroenteritis,cyst-containing SAC meat is confiscated or depreciated by sanitary authoritieswith serious economic consequences for breeders. In the present study, a duplexsemi-nested PCR was designed to simultaneously detect parasite and llama DNA inblood samples. Species-specific regions of the S. aucheniae 18S rRNA andLama glama 16S mitochondrial gene were amplified, yielding bands of 583and 257 bp, respectively. The method proved to be highly sensitive, with adetection limit of 0.5 parasites per ml of blood. Blood samples were collectedfrom llamas of Argentina and Bolivia (n=225) and analyzed using this method, ofwhich 18.7% resulted positive for S. aucheniae. No correlation was foundbetween PCR results and llama age, sex or the finding of macroscopic cysts inmeat after slaughter. Lack of molecular detection in the blood of some llamasharboring macrocysts suggests that parasite circulation in the bloodstreamafter encystment is below the detection threshold of the test or even absent,while PCR positive results in cyst-infected animals suggests that priorexposure to the parasite does not impede subsequent infections. Finding ofcysts in carcasses upon slaughter was significantly higher (p< 0.01) infemale llamas and in animals of both genders older than 3 years of age. Themethod was also applied to the blood of alpacas (Lama pacos, n= 13) andvicugnas (Vicugna vicugna; n= 100), with 7.7% and 11% of positivedetection. Molecular detection of S. aucheniae using the describedduplex semi-nested PCR can be useful in epidemiological studies, to assess theeffectiveness of parasiticide treatments, and for the surveillance and tracingof the definitive hosts. It also proved useful to determine for the first timethat vicugnas can be infected with S. aucheniae. Financial support bythe Ministry of Science and Technology (MINCyT, PICT 2014-3747) and theNational Institute of Agricultural Technology (INTA, SAJU1232204 and PNSA1115055), Argentina, is gratefully acknowledged.