The validity of Sarcocystis sinensis.

Abstract

Recently, in a publication of Dubey et al (2014) was suggested that Sarcocystis sinensis was a nomen nudum based on what they considered insufficient description of the pararasite and lack of publicly available voucher material. They singled out that Zuo et al (1990) was not an appropriate venue for publishing a new species description, but we believe they did not adequately acknowledge two other reports in 1992 and 1995 when reaching their conclusion. Dubey et al (2014) correctly state that “the species of Sarcocystis from the water buffalo in China was presented under the name ‘S. sinensis’ by Zuo (Zuo et al, 1990) at a national meeting (Fifth Symposium of the Chinese Society of Protozoology, Chongqing), and an abstract without figures was released.”(Dubey et al, 2014). That presentation would not serve as a valid basis for naming the new species. However, S. sinensis was first formally published by Zuo et al (1995). There, in the book “the Proceedings of the Tenth Anniversary of the Founding of the China Parasitological Society” (ISBN 7-5046-2012-2, Chinese Science and Technology Express, Beijing, China, 1995), and a book “Coccidians in Livestock and Birds and Human Coccidiosis” (ISBN 7-5308-1195-9, Science and Technology Publishing Company of Tianjin, Tianjin, China, 1992), the cyst’s clear and detailed morphological structure was described and the life cycle was studied by Zuo (Zuo, 1992; Zuo et al, 1995). We present here the translation of the original descriptions as well as the detailed morphology of muscular cysts of Sarcocystis sinensis and infection experiments. In the book (Zuo et al, 1995), the new species was described from cysts in muscles of water buffalo (Bubalus bubalis) from Kunming, Yunnan, China. Cysts were long and thin and/or fusiform in shape, 1 250 μm×100 μm (480-3 570 μm×45-152 μm) in average size. Leaning, finger-like protrusions (Figure 1, 10), 4.2-10.1 μm in size, averaged 5.8 μm, contained microtubules and few electron-dense granules (Figure 1, 11). There were invaginations on the surface of the protrusions’ mostly in the middle and base parts. Ground substrate was 0.41.7 μm in thickness, extending inside of the cyst formed the septa-like structures or segmentation inside the cyst, in which a lot of concentrated banana-shaped bradyzoites, 13.0 μm×3.6 μm (10.9-16.1 μm×2.7-4.7 μm) in size could be seen. Under the scanning electron microscopy (SEM), the tip surface of the protrusions was arranged as regular square-shaped structures with space measured 0.4×0.8 μm, between reach other (Figure 1, 12). Natural prevalence was estimated at 58.0%. Location of parasite was skeletal muscle. Light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were presented. The cysts structure under LM, TEM and SEM were presented from both books were copied as Figure 1. 1 In order to identify its definitive host, experimental infections were conducted initially in carnivorous animals. The first experiment was performed from April to May, 1988. Two dogs, two cats and two rhesus monkeys (Macaca mulatta) were infected with fresh S. sinensis cysts isolated from water buffalo. Each animal was fed with 60 cysts. Stools of the infected animals were examined for the presence of sporocysts and oocysts from day 5 to day 40 post feeding. Finally, animal were killed and the scrape from the intestinal mucosa was examined for Sarcocystis sporocysts and oocysts. No sporocysts and oocysts were found. Second experiment was performed from December 1989 to June1990, and three cats, three dogs, one eurasian sparrow hawk (Accipiter nisus), a boreal owl (Aegolius funereus), an eurasian tawny owl (Strix aluco), and a littlebanded goshawk (A. badius), two vultures (A. monachus) were infected with S. sinensis cysts. Each animal were fed with 200 cysts. Stools of the infected animals were examined for the presence of sporocysts and oocysts from day 5 to day 40 post feeding. Except of goshawk and vultures, all animals were checked as first experiment in 1988, killed and intestinal mucosa were examined. No sporocysts and oocysts were found. The third infection experiment was performed in 1995. Two volunteers (one 55 years old woman and one 29 years old man) swallowed 1 600 and 2 000 cysts respectively, but no sporocysts and oocysts were found later. These attempts demonstrated that none of these hosts serves as the definitive host for this parasite (Zuo et al, 1995). The definitive host of S. sinensis remains unknown to this day. The identification of S. sinensis is as following: Intermediate host: water buffalo Definitive host: unknown