The potential usefulness of the modified Kato thick smear technique in the detection of intestinal sarcocystosis during field surveys.

A total of 479 stool specimens were collected from rural communities of Ubon Ratchathani Province, Thailand and examined by two techniques: the modified Kato thick smear and the direct smear. The prevalence of Opisthorchis viverrini (14.8%), hookworm (10.2%), Sarcocystis spp (4.6%), Taenia spp (2.9%), Strongyloides stercoralis (2.1%), Giardia lamblia (1.2%), Echinostoma spp (0.6%), Ascaris lumbricoides (0.4%), Entamoeba histolytica (0.2%), Chilomastix mesnili (0.2%) and Endolimax nana (0.2%) were determined. The morphology of the Sarcocystis spp sporocysts examined by both procedures looked similar and was found to be easily recognizable. Among these specimens, 22 cases (4.6%) were positive for Sarcocystis infection detected by the modified Kato technique, whereas only one case (0.2%) was detected by both techniques. These differences were found to be statistically significant (p < 0.05), indicating that the modified Kato technique was decidedly more sensitive than the direct smear procedure in identifying Sarcocystis infection. An epidemiological survey was conducted in Khon Kaen Province involving 1124 stool samples using the modified Kato technique. The greatest frequency was Opisthorchis viverrini at 32.0% while the second highest was Sarcocystis spp at 8.0%. The prevalences of hookworm, Echinostoma spp, Taenia spp, Trichuris trichiura and Enterobius vermicularis were 2.7, 2.1, 1.0, 0.2 and 0.2%, respectively. Other than opisthorchiasis, northeastern Thailand may be an endemic area for sarcocystosis. This is the first report of the applicability and potential usefulness of the Kato thick smear technique for the diagnosis of Sarcocystis infection in a field survey.