Detection of Sarcocystis aucheniae DNA in placental and umbilical cord tissues suggests possible vertical transmission in domestic South American camelids.

Sarcocystis aucheniae is a coccidian parasite of South American camelids (SAC) that causes substantial economic losses through carcass condemnation due to the presence of macroscopic muscular cysts. Although horizontal transmission through canid definitive hosts is well established, the remarkably high prevalence of infection observed in alpacas and llamas suggests that additional transmission routes may contribute to parasite maintenance. The aim of this study was to investigate the occurrence of S. aucheniae DNA in placenta and umbilical cord tissues. Placenta and umbilical cord samples were collected from pregnant alpacas and llamas in the final third of gestation at a slaughterhouse in southern Peru, as well as from alpacas sampled at parturition in a breeding establishment. DNA was extracted and analyzed using a previously described duplex semi-nested PCR targeting the S. aucheniae 18S rRNA gene. Selected positive amplicons were subjected to Sanger sequencing. Parasite DNA was detected in at least one tissue (placenta and/or umbilical cord) in 33 of 42 animals (78.6%). Parasite detection in placenta and umbilical cord was not statistically significantly different in paired samples, and animals positive in umbilical cord samples had increased odds of testing positive in placenta. Agreement between tissues was moderate, suggesting an uneven distribution of parasites within maternal-fetal compartments. No association was observed between parasite detection and age category. Sequencing confirmed the identity of the amplified fragments as S. aucheniae. Although detection of parasite DNA in placental and umbilical cord tissues does not by itself demonstrate fetal infection, the high frequency of positive animals and the significant association between both tissues provide the first molecular findings consistent with possible vertical transmission in S. aucheniae. These findings broaden current understanding of the parasite life cycle and suggest that vertical transmission may contribute to parasite persistence in SAC populations, with important implications for disease control.