Molecular Detection of Haplorchis pumilio Eggs in Schoolchildren, Kome Island, Lake Victoria, Tanzania

H aplorchis pumilio, a species of the zoonotic minute intestinal flukes belonging to the family Heterophyidae, was first discovered in the small intestines of birds and mammals in Egypt (1).Infection with this fluke also occurs in humans through the consumption of raw or improperly cooked fish harboring the metacercariae.Abdominal pain, diarrhea, lethargy, anorexia, malabsorption, and weight loss are the possible clinical symptoms (2).This fluke is widely distributed geographically from Africa to Asia, Australia, and the Americas (1).However, human infections were reported in only 5 countries in Africa and Asia: Egypt, China, Laos, Thailand, and Vietnam (1).We recently surveyed the prevalence of intestinal helminths among schoolchildren in 12 primary schools on Kome Island, Lake Victoria, Tanzania (Figure 1, panel A).We detected a low-grade prevalence of an apparent species of Haplorchis or Heterophyes by the recovery of eggs in fecal samples.We used molecular methods to confirm the eggs to be H. pumilio on the basis of 18S and 28S rDNA gene sequences. The StudyAn international collaborative project between South Korea and Tanzania named "Rapid assessment of schistosomiasis and soil-transmitted helminthiases on Kome Island, Buchosa District, northwestern Tanzania" was implemented during 2020-2022.This project was approved by the Ethics Committee of the Korea Association of Health Promotion, Seoul, South Korea (IRB no.130750-202009-HR-019).Fecal examinations were performed on 1,440 schoolchildren in 12 primary schools by using the Kato-Katz thick smear technique.The number of overall helminth egg-positive cases was 631/1,440 (43.8%):Schistosoma mansoni (564 [39.2%]),Trichuris trichiura (42 [2.9%]), Ancylostoma duodenale or Necator americanus (27 [1.9%]), small trematode eggs (STE) (19 [1.3%]), Enterobius vermicularis (16 [1.1%]), and others (unidentified) (7 [0.5%]).The STE were operculate, oval, yellowish-brown in color, 29.0-31.6 (mean 30.4) µm long, and 14.8-17.6(mean 16.5) µm wide (n = 6).They seemed to be the eggs of a Haplorchis or Heterophyes species (Figure 1, panels B and C).The STE-positive fecal samples were preserved in 100% ethanol for molecular analysis.We extracted DNA from 20 mg of the fecal sediment by using the DNeasy Tissue and Blood kit (QIAGEN, https://www.qiagen.com)after a modified formalinether concentration method in which formalin was replaced with water.The sediment was washed several times with distilled water.