Morphological and molecular characteristics of Sarcocystis bertrami from horses and donkeys in China

Authors: ZENG, WEILIN - Kunming Medical University; SUN, LING - Kunming Medical University; XIANG, ZHENG - Kunming Medical University; LI, NA - Kunming Medical University; ZHANG, JIE - Kunming Medical University; HE, YONGSHU - Kunming Medical University; LI, QING - Kunming Medical University; YANG, FANG - Kunming Medical University; HU, JUNJIE - Yunnan University; SONG, JINGLING - Kunming Medical University; MORRIS, JAMES - Clemson University; Rosenthal, Benjamin; YANG, ZHAOQING - Kunming Medical University

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2018
Publication Date: 3/15/2018
Citation: Zeng, W., Sun, L., Xiang, Z., Li, N., Zhang, J., He, Y., Li, Q., Yang, F., Hu, J., Song, J., Morris, J., Rosenthal, B.M., Yang, Z. 2018. Morphological and molecular characteristics of Sarcocystis bertrami from horses and donkeys in China. Veterinary Parasitology. 252:89-94. https://doi.org/10.1016/j.vetpar.2018.01.024
DOI: https://doi.org/10.1016/j.vetpar.2018.01.024

Interpretive Summary: Species of Sarcocystis are parasites are maintained by cycles of transmission involving two types of hosts. Carnivores become infected by eating infected tissues of an herbivore, and excrete environmentally-resistant parasite cysts that contaminate the water, soil, and vegetation consumed by the herbivore. There are many such parasites, most relegated to wildlife and livestock hosts, some of which compromise livestock health and a few known to pose risks to human health via contaminated food. Microscopic and genetic features are needed in order to establish the identities and transmission routes of these many, otherwise difficult to distinguish protozoa. Here, USDA scientists at the Beltsville Agricultural research center worked with international partners to examine such parasites in horses and donkeys. They found that although these parasites expressed variation in size and certain structural features, all such parasites seemed to share especially close genetic affinities and concluded that donkeys and horses were infected by the same parasitic species. These data contribute to our understanding of parasite diversity and to the epidemiology and host range of the parasite, and will interest veterinarians, epidemiologists, parasitologists, farmers, and food safety professionals.

Technical Abstract: Sarcocystis cysts collected from donkeys and horses were studied by morphological and molecular methods. Morphological studies performed by light microscopy (LM) revealed that each of two types of cysts were present in samples from both donkey and horse. These two types of cysts, type I (larger) and type II (smaller), had in some cases short or long finger-like villi, or no protrusions (VP) under LM. By electron microscopy (EM), VPs from both horse and donkey cysts were found to share similar structures, appearing to be typical of ‘type 11a’ VPs found on the Sarcocystis wall of Sarcocystis fayeri as described by Dubey (2016). The VP from horse and donkey cysts contained microtubules, which extended from the villar tips to the ground substance (GS). Ovoid osmiophilic bodies (OB), were found along the length of the microtubules within the villi, but this feature was not found in all VP. Phylogenetic relationships based on about 1000 bp the 18S rDNA and Cox I sequences of these organisms were analyzed. Phylogenetic relationships show that the all studied samples, regardless of host origin or morphological appearance under LM, group in one branch. Ours is the first attempt to combine the power of morphological and molecular analysis to such equine parasites, and the results confirm a close relationship of the horse and donkey parasite with S. fayeri. Further, the data suggest that the cysts in both hosts are the same species. As the species was first named Sarcocystis bertrami, we propose that S. bertrami is the appropriate descriptor for the parasite found in horse and donkey.