Research brief Characterization of Sarcocystis species in domestic animals using a PCR-RFLP analysis of variation in the 18S rRNA gene: a cost-effective and simple technique for routine species identification Zhao-Qing Yang, a,b,c Qing-Qing Li, c Yang-Xian Zuo, c Xin-Wen Chen, c Yong-Jiu Chen, a Long Nie, a Chang-Gue Wei, b Jia-Shun Zen, b S.W. Attwood, d Xue-Zheng Zhang, b and Ya-Ping Zhang a, * a Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming, Yunnan 650223, China b Parasitology Department, Kunming Medical College, Kunming, Yunnan 650031, China c Biology Department, Yunnan University, Kunming, Yunnan 650091, China d Department of Zoology, The Natural History Museum, Cromwell Road, SW7 5BD London, UK Received 9 December 2001; received in revised form 21 October 2002; accepted 12 March 2003 Abstract Thirteen restriction endonucleases were used to investigate nucleotide sequence variation in the 18S rRNA DNA of 88 indi- vidualsfromten Sarcocystis taxacollectedascystsfromtheirintermediatehosts,swine,cattleandwaterbuffalo.ADNAsequence of approximately 900bp was used. A total of 26 electromorphs were detected. The electromorphs were sorted into seven different haplotypes that coincided with the six named species and an unidentified species from cattle. These findings support those of our morphological examinations, which suggested that the taxa resembling Sarcocystis hirsuta, S. hominis,bothfoundinwaterbuffalo, and S. sinensis foundincattle,arenotnewspeciesbutareinfact S. hirsuta and S. hominis asfoundincattle,and S. sinensis asfound inwaterbuffalo;thisfindingsupportstheideathatthesespeciescanutilizebothcattleandwaterbuffaloasintermediatehostsand arenotrestrictedtooneortheotherhostgroupaspreviouslythought.PCR-RFLPresolvedbyagarosegelelectrophoresisisshown to be an easy and rapid method of discriminating between these species. Ó 2003 Elsevier Science (USA). All rights reserved. Index Descriptors: 18S ribosomal RNA (rRNA) gene, small subunit (SSU), polymerase chain reaction (PCR)-restriction fragment length poly- morphism(RFLP),deoxyribonucleicacid(DNA),speciesidentification,intermediatehostrange,Protozoa,Apicomplexa,Sporozoa,Sarcocystidae, Sarcocystis, S. fusiformis, S. hirsuta, S. hominis, S. mischeriana, S. sinensis, S. suihominis. Sarcocystis is one of the most prevalent parasites of livestock (Dubey et al., 1989b). The prevalence of in- fections with Sarcocystis species in domestic animals, suchascattle,waterbuffalo,andswine,havebeenfound to be up to 100% in south China (Zuo, 1992). Some species of Sarcocystis can cause reduced weight gain, poorfeedingefficiency,anorexia,fever,anaemia,muscle weakness, reduced milk yield, abortion, and death in intermediate hosts such as cattle, sheep, goats, and swine. Certain species infect humans and can cause di- gestive disturbances such as nausea, vomiting, and di- arrhoea (Dubey et al., 1989b; Zuo, 1992). Of those Sarcocystis species infecting domestic ani- mals (i.e., those species most often studied), a given species usually infects only one species of intermediate hostanduseseitherfelidsorcanids,butnotboth,asits definitive host (Huong et al., 1997b; Odening et al., 1996; Odening et al., 1995; Zuo et al., 1995). The con- ventional method of distinguishing the different Sarco- cystis species is by observing the structure of the cyst wall under light microscopy or transmission electron microscopy,andcombiningthesedatawithinformation on the lifecycle (i.e., host species involved). However, such methods are not suitable for the routine identifi- Experimental Parasitology 102 (2002) 212–217 www.elsevier.com/locate/yexpr * Corresponding author. Fax: +86-871-519-5430. E-mail address: zhangyp@public.km.yn.cn (Y.-P. Zhang). 0014-4894/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0014-4894(03)00033-X