Redescription, deposition of life cycle stages specimens of Sarcocystis bovifelis Heydorn, Gestrich, Mehlhorn, and Rommel, 1975, and amendment to Sarcocystis hirsuta Moulé, 1888

Authors: Dubey, Jitender

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2022
Publication Date: 8/4/2022
Citation: Dubey, J.P. 2022. Redescription, deposition of life cycle stages specimens of Sarcocystis bovifelis Heydorn, Gestrich, Mehlhorn, and Rommel, 1975, and amendment to Sarcocystis hirsuta Moulé, 1888. Parasitology. 149(12):1575-1589. https://doi.org/10.1017/S0031182022001044.
DOI: https://doi.org/10.1017/S0031182022001044

Interpretive Summary: Sarcocystis species are a group of single celled parasites affecting humans and livestock. There are more than 200 species in the genus Sarcocystis. Some of them cause abortion, generalized disease, muscle weakness, low milk production, and retarded growth in livestock. Of the 8 named species of Sarcocystis in cattle, Sarcocystis cruzi is most pathogenic and the APDL scientists pioneered research on this species. Two species of Sarcocystis in beef are zoonotic, S. hominis and S.heydorni; humans become infected by eating undercooked beef infected with these parasites. Some species of Sarcocystis (Sarcocystis hirsuta) form cysts in beef that become grossly visible, and their presence can lead to condemnation of parts or whole carcasses mainly for aesthetic reasons. There is considerable confusion concerning the identity of Sarcocystis species in cattle, partly because most species (except S. cruzi) are poorly defined. Here Dr. Dubey has redescribed the morphology of one of the species, Sarcocystis bovifelis, and distinguished it from S. hirsuta. For the benefit of future researchers, the reference materials were deposited by Dr. Dubey in the Smithsonian. This paper conclusively clarifies distinctions between two species of Sarcocystis with thick sarcocyst walls that occur in cattle: S. bovifelis and S. hirsuta. This paper will be of interest to biologists, parasitologists, and veterinarians. This research was conducted in 1980’s before the closure of Toxoplasma research and the cat colony.

Technical Abstract: There is considerable confusion concerning the life cycles and taxonomy of Sarcocystis species in cattle. Of the eight species of Sarcocystis named from cattle, two (S. cruzi and S. heydorni) are morphologically distinctive because their sarcocysts are microscopic and the sarcocyst wall is thin (< 0.5 µm thick). The sarcocysts of the remaining six (S. hirsuta, S. hominis, S. bovini, S. bovifelis, S. sinensis, S. rommeli) have thick (5-8 µm) walls undistinguishable by light microscopy, alone. The identity of some of these, and of additional, unnamed species of Sarcocystis in cattle, remain uncertain. Poor descriptions of the thick-walled species contribute to this confusion. To provide needed clarity, I herein review the history, nomenclature, and life cycle of S. bovifelis (originally named by Heydorn and associates) and deposit specimens of its various life cycle stages to a museum for future reference. I also provide means to distinguish this parasite from S. hirsuta. Cats are the definitive hosts for S. bovifelis. It has two schizogonic stages. First-generation schizonts were found 7-23 days p.i. in arteries associated with mesenteric lymph nodes and intestines; they were 37.2 x 22.3 µm and contained more than 100 merozoites, which measured 5.1 x 1.2 µm. Merozoites measuring 5.4 x 1.5 µm were found free in the peripheral blood of a calf 16 days post-inoculation (p.i.). Second-generation schizonts were found in capillaries of striated muscles and heart 15-23 days p.i.; they were 13.9 x 6.5 µm and contained up to 35 merozoites that measured 4.0 x 1.5 µm. Sarcocysts formed between 25 and 30 days p.i. in striated muscles, but not in heart. Sarcocysts matured on day 75 and were infective for cats. Sarcocysts were up to 675 µm long and up to 105 µm wide, the wall was up to 6 µm thick. Gamonts were found in cat intestinal epithelium, primarily in goblet cells. Sporogony occurred in the lamina propria. Sporulated oocysts were 17.1 x 12.7 µm and sporocysts were 12.8 x 8.4 µm. Sarcocystis bovifelis is distinguished morphologically from Sarcocystis hirsuta.