A worm in the toilet bowl! What does it tell us about the challenges in the identification of supposed human parasites in practical parasitology?


  • Hudson A. Pinto Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
  • João Rodrigo Campos Laboratório Lustosa, Belo Horizonte, Minas Gerais, Brazil
  • Larissa C. M. Gomes Laboratório Lustosa, Belo Horizonte, Minas Gerais, Brazil
  • Vinícius S. Costa Laboratório Lustosa, Belo Horizonte, Minas Gerais, Brazil
  • Hyllo B. Marcello Junior Laboratório Lustosa, Belo Horizonte, Minas Gerais, Brazil
  • Vitor Luís Tenório Mati Departamento de Medicina, Universidade Federal de Lavras, Lavras, Minas Gerais, Brazil


annelid, diagnosis, helminths, misidentification, pseudoparasitism, epistemology


Non-parasitic vermiform organisms can circumstantially be associated with humans and their identification can be challenging for medical professionals. The present report describes the finding of a worm in the toilet bowl by a patient from Brazil, who thought he had expelled it in his feces. The gross analyses in a clinical laboratory reveal the worm was different from other macroscopic organisms routinely identified, and the laboratory staff requested assistance in an academic laboratory specialized in helminthology. After preliminary analysis in a stereomicroscope, the supposed human worm was identified as an oligochaete annelid (earthworm). The patient was contacted to investigate a possible case of pseudoparasitism. However, we were informed that the organism had been collected in a toilet bowl from a rural environment where the untreated water comes from a cistern indicating our finding was circumstantial. The methodology revisited herein allowed a quick microscopic analysis of easy-to-view morphological structures, which are useful to separate oligochaete annelids from helminths and can prevent misdiagnosis in similar situations. We discuss the overly restricted view on human parasites by health professionals in collecting clinical history and laboratory analysis, providing some epistemological insights on the necessary interdisciplinarity between parasitology and other basic knowledge with health practice.


Little M. 1991. Laboratory diagnosis of worms and miscellaneous specimens. Clinics in Laboratory Medicine 11(4): 1041–1050. https://doi.org/10.1016/S0272-2712(18)30534-1

Margery J., Niang A. 2011. Adult Ascaris worm passing from the mouth. American Journal of Tropical Medicine and Hygiene 85: 395. https://doi.org/10.4269/jtmh.2011.11-0258

Kobayashi Y., Tsuyuzaki J. 2018. Ascaris lumbricoides discharge from the mouth. Case Reports in Gastroenterology 12(1): 153–157. https://doi.org/10.1159/000488524

Shah J., Shahidullah A. 2018. Ascaris lumbricoides: a startling discovery during screening colonoscopy. Case Reports in Gastroenterology 12(2): 224–229. https://doi.org/10.1159/000489486

Purohit G., Mohanty S., Tirkey R., Sasmal P.K. 2019. Inadvertent detection of massive Enterobius vermicularis infection in an asymptomatic adult with rectal blowout following barotrauma. Annals of Parasitology 65(1): 103–105. https://doi.org/10.17420/ap6501.189

Muller R., Wakelin D. 2002. Worms and human disease, 2nd ed. CABI International, Wallingford.

Roberts L.S., Janovy-Jr J., Nadler S. Gerald D. 2002. Schmidt & Larry S. Roberts’ Foundations of Parasitology, 9th ed. McGraw Hill, New York.

De N.V., Le T.H. 2011. Human infections of fish- borne trematodes in Vietnam: prevalence and molecular specific identification at an endemic commune in Nam Dinh province. Experimental Parasitology 129(4): 355–361. https://doi.org/10.1016/j.exppara.2011.09.005

Mwape K.E., Gabriël S. 2014. The parasitological, immunological, and molecular diagnosis of human taeniasis with special emphasis on Taenia solium taeniasis. Current Tropical Medicine Reports 1: 173–180. https://doi.org/10.1007/s40475-014-0028-5

Dao T.T., Bui T.V., Abatih E.N., Gabriël S., Nguyen T.T., Huynh Q.H., Nguyen C.V., Dorny P. 2016. Opisthorchis viverrini infections and associated risk factors in a lowland area of Binh Dinh Province, Central Vietnam. Acta Tropica 157: 151–157. https://doi.org/10.1016/j.actatropica.2016.01.029

Mathison B.A., Pritt B.S. 2018. A systematic overview of zoonotic helminth infections in North America. Laboratory Medicine 49(4): e61–e93. https://doi.org/10.1093/labmed/lmy029

Otranto D., Deplazes P. 2019. Zoonotic nematodes of wild carnivores. International Journal for Parasitology: Parasites and Wildlife 9: 370–383. https://doi.org/10.1016/j.ijppaw.2018.12.011

Podhorský. M. 2011. [Laboratory diagnosis of pseudoparasites, artifacts and parasitic delusions]. Klinicka Mikrobiologie a Infekcni Lekarstvi 17(3): 100–102.

Khuroo M.S. 1996. Ascaris. Gastroenterology Clinics of North America 25(3): 553–577. https://doi.org/10.1016/s0889-8553(05)70263-6

Grove D. 1990. Ascaris lumbricoides y ascariasis. In: A history of human helminthology (Ed. D. Grove). CABI International, Wallingford: 469–497.

Bethony J., Brooker S., Albonico M., Geiger S.M., Loukas A., Diemert D., Hotez P.J. 2006. Soil- transmitted helminth infections: ascariasis, trichuriasis, and hookworm. Lancet 367(9521): 1521–1532. https://doi.org/10.1016/S0140-6736(06)68653-4

Plisko J.D, Nxele T.C. 2015. An annotated key separating foreign earthworm species from the indigenous South African taxa (Oligochaeta: Acanthodrilidae, Eudrilidae, Glossoscolecidae, Lumbricidae, Megascolecidae, Microchaetidae, Ocnerodrilidae and Tritogeniidae). African Invertebrates 56(3): 663–708. https://doi.org/10.5733/afin.056.0312

Blakemore R.J., Lee W., Ryu J.S., Ahn M.H., Kim S.R. 2012. Accidental vaginal parasitism by oligochaete worms (Annelida: Oligochaeta). Opuscula Zoologica (Budapest) 43(2): 197–201.

Liu H., Zhang Z., Huang G., Gu X., Wang C., Wang Y., Lu Z. 2017. Infection of oligochaetes, Limnodrilus hoffmeisteri (Annelida: Oligochaeta), in the nasal cavity of a Chinese man. Korean Journal of Parasitology 55(1): 77–79. https://doi.org/10.3347/kjp.2017.55.1.77

Dexter R.W. 1964. Oligochaetes as pseudoparasites of man. Ohio State Medical Journal 60: 473–474.

Walton B.C., Yokogawa M. 1972. Terrestrial turbellarians (Tricladida: Bipaliidae) as pseudo- parasites of man. Journal of Parasitology 58(3): 444–446. https://doi.org/10.2307/3278185

Ali-Khan F.E., Ali-Khan Z. 1977. Paragordius varius (Leidy) (Nematomorpha) infection in man: a case report from Quebec (Canada). Journal of Parasitology 63(1): 174–176. https://doi.org/10.2307/3280141

Yamada M., Tegoshi T., Abe N., Urabe M. 2012. Two human cases infected by the horsehair worm, Parachordodes sp. (Nematomorpha: Chordodidae), in Japan. Korean Journal of Parasitology 50(3): 263–267. https://doi.org/10.3347/kjp.2012.50.3.263

Mathison B.A., Pritt B.S. 2014. Laboratory identification of arthropod ectoparasites. Clinical Microbiology Reviews 27(1): 48–67. https://doi.org/10.1128/CMR.00008-13

Edwards C.A., Lofty R. 1977. The Biology of Earthworms. Chapman & Hall, London.

Govedich F.R., Bain B.A., Moser W.E., Gelder S.R., Davies R.W., Brinkhurst R.O. 2010. Annelida (Clitellata): Oligochaeta, Branchiobdellida, Hirudi- nida, and Acanthobdellida. In: Ecology and classification of North American freshwater invertebrates (Eds. J.H. Thorp, A.P. Covich), 3rd ed. Elsevier and Academic Press, San Diego: 385–436.

Yılmaz H., Türkdoğan M.K., Akdeniz H., Katı İ., Demiröz A.P. 1998. Ascaris lumbricoides in the oral cavity: a case report. Eastern Journal of Medicine 3(2): 75–76.

Holland C. 2013. Ascaris: the neglected parasite. Elsevier and Academic Press, London.

Asaolu S.O., Ofoezie I.E. 2018. Ascaris spp. In: Water and sanitation for the 21st Century: Health and microbiological aspects of excreta and wastewater management (Global Water Pathogen Project (Eds. J.B. Rose, B. Jiménez-Cisneros). (Part 3: Specific excreted pathogens: Environmental and epidemio- logy aspects – Section 4: Helminths, Ed. L Robertson). UNESCO and Michigan State University, East Lansing. https://doi.org/10.14321/waterpathogens.41

Neira P., Pino G., Munoz N., Tobar P. 2011. Eliminación de estadios juveniles de Ascaris lumbricoides (Linneo, 1758) por via oral: reporte de un caso y algunas consideraciones epidemiológicas. Revista Chilena de Infectología 28(5): 479–483 (in Spanish with summary in English). https://doi.org/10.4067/S0716-10182011000600014

Ruscio K.P. 1986. Bridging specializations: reflections from biology and political science. Review of Higher Education 10(1): 29–45. https://doi.org/10.1353/rhe.1986.0010

Pielke-Jr R.A., Byerly R. 1998. Beyond basic and applied. Physics Today 51(2): 42–46. https://doi.org/10.1063/1.882370

Frodeman R. 2011. Interdisciplinary research and academic sustainability: managing knowledge in an age of accountability. Environmental Conservation 38(2): 105–112. https://doi.org/10.1017/S0376892911000038




How to Cite

Pinto, H. A., Campos, J. R., Gomes, L. C. M., Costa, V. S., Marcello Junior, H. B., & Tenório Mati, V. L. (2023). A worm in the toilet bowl! What does it tell us about the challenges in the identification of supposed human parasites in practical parasitology?. Annals of Parasitology, 69(1), 31–36. Retrieved from https://annals-parasitology.eu/index.php/AoP/article/view/21



Case reports