Will an untreated pinworm infestation go away on its own? Does a pinworm infection result in lasting immunity that protects against future infection? The answer to the first question is yes, under ideal circumstances. The answer to the second question is no.
The human immune response to helminths
The way that the human immune system responds to parasitic worms (helminths) has been extensively studied. There is no question that the immune system responds to these infections; however, that response, in general, tends not to eradicate the infection. In simple terms, this is probably because any immune attack powerful enough to eradicate these relatively large organisms (even a tiny pinworm is very large compared to a bacterium or a virus) would also do serious damage to host tissues.
Thus, our bodies tend to tolerate helminths rather than eradicate them (Roberts and Janovy). Chronic infection, accompanied by a moderated immune response over the long term results in some of the most devastating parasitic diseases known, such as schistosomiasis and river blindness. Typically, untreated helminth infestations end when the worms die of old age, or the host dies for any reason.
Enterobius vermicularis is an heirloom parasite
Adauto et al explain how both archaeological and genetic evidence support the theory that pinworm is one of our heirloom parasites: it has been a human parasite and evolved with the human host over hundreds of thousands of years. This parasite, because its eggs are infective almost immediately, and because it is passed directly from person to person, can survive easily in human populations even in harsh climatic conditions. Pinworm easily traveled with migrating early humans and now infects people of every culture.
Groups of early migrants were small of course, and no infectious organism can be successful in a small group of people unless it can continually find new susceptible hosts, or reinfect those who have already suffered a bout of infection.
Immunity to pinworm infection
Pinworm’s ability to reinfect people who have already had it is, in fact, well documented. Gale points out that, for this helminth, “Each bout is self-limiting because the worms cannot reproduce within the gut, and Enterobius has a short lifespan relative to other helminths. It therefore adopts a strategy that makes reinfestation highly likely.” The same strategy makes it highly likely that others will become infected as well.
The study reported by Lohiya and colleagues describes the difficulty of eradicating E. vermicularis: “although effective medications have been available for decades, control of enterobiasis has been difficult because of reinfection, incomplete cure of infected people, and its ready transmissibility.”
Although some people may have more resistance to pinworm infection than others, in general we do not become immune to this parasite.
Treatment of pinworm infection
Will an untreated pinworm infestation go away on its own? Yes, probably, and presumably this occurs in many asymptomatic infections. It’s likely the immune system has some short term ability to destroy new larvae and the adult worms will eventually simply die out. However, in order to avoid reinfection, personal hygiene of all potentially infected individuals, and all those at risk, must be exemplary.
Does a pinworm infection result in lasting immunity that protects against future infection? No, and experience suggests that reinfection often occurs within a very short time period.
The standard medical response to enterobiasis is to treat with antihelminthic drugs, and employ rigorous standards of cleanliness and hygiene in the home to try to prevent spread and reinfection. Despite the difficulty of eradicating the parasite, treatment may be unavoidable in the symptomatic patient because, in the words of Roberts and Janovy, “the subsequent vicious circle of bleeding, bacterial infection, and intensified itching can lead to a nightmare of discomfort.”
Sources:
Araújo, Adauto, Luiz F. Ferreira, Karl J. Reinhard, and Scott L. Gardner. 2008 “Parasites as Probes for Prehistoric Human Migrations? (galley proofs) Natural Resources, School of Papers in Natural Resources, University of Nebraska – Lincoln.
Gale, E. A. M. “A missing link in the hygiene hypothesis? Diabetologia 2002: 45.
Lohiya, Ghan-Shyam, Lilia Tan-Figueroa, Francis M Crinella etal. “Epidemiology and control of enterobiasis in a developmental center.” West J. Med, 2000: 175(2).
Maizels, Rick M, Edward J. Pearce, David Artis et al. “Regulation of pathogenisis and immunity in helminth infections. JEM, 2009: 206(10)
Roberts, Larry S. and John Janovy Jr. Foundations of Parasitology 6th Ed. Boston: McGraw Hill, 2000.
Rosemary Drisdelle - Rosemary Drisdelle has been published many times as a nonfiction writer and several times as a poet. Her first book, Parasites: Tales of ...
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