Enterobius vermicularis
NB. The human helminth, Enterobius vermicularis (EV), is known as 'pinworm' in the US, and 'threadworm' in the UK and Australia, and should not be confused with Strongyloides stercoralis, the roundworm that causes strongyloidiasis and is known as 'pinworm' in the UK and 'threadworm' in the US.
Fossil evidence suggests that the pinworm lineage extends at least as far back as 240 million years, at which point it infected primitive proto-mammals that were the ancestors of modern vertebrates including humans and other primates. [1] Today, EV is distributed worldwide, and is arguably the most successful helminth of the Western world, remaining the most common helminth infection in the US, Western Europe and Oceania.
Disadvantages and potential risks
EV will never qualify as a therapeutic helminth because of a number of disadvantages:
- its numbers are not controllable
- it spreads very easily to other people
- it can cause uncomfortable anal itching
- it may be a vector for the intestinal protozoan Dientamoeba fragilis [2]
- it can cause acute appendicitis [3] and appendiceal colic [4]
- it can rarely cause colonic obstruction [5]
- it can migrate to organs beyond the intestine (e.g., kidney, male urinary tract and female genital tract/uterus [6]
- it can cause urinary tract infections and vaginitis [7]
- it can, in extremely rare cases, cause Mesenteric Lymphadenopathy [8]
- it has even manifested post traumatic stress disorder-like symptoms [9]
The possible therapeutic benefits of hosting E. vermicularis
Although the authors of one study, using a population-based analysis, concluded that EV does not reduce the risk for asthma, type 1 diabetes, arthritis or inflammatory bowel disease, [10] there is evidence that this species can in fact provide therapeutic benefits.
One study found that, in atopic children infected with EV, there was not only a lack of any symptoms as a result of the infection, but that, “there seemed to be some indication of immunosuppression in those children with a positive history of allergic disease.” [11]
Therapeutic benefits have also been reported anecdotally by several people who have hosted EV.
Prevention and control of E. vermicularis
For approaches to prevent and control EV, see the following page on the CDC website.
Special care needs to be taken with the handling of bed linen and the clothing of infected individuals because EV eggs attach to dust which can become airborne and, if inhaled, can cause reinfection.
Control of E. vermicularis in those who are hosting therapeutic helminths
The use of an anthelmintic drug to eradicate EV would also kill at least some of a colony of therapeutic helminths. So, faced with this dilemma, one self-treater experimented with control options and reported that a low sugar, low refined carbohydrate, high fibre diet significantly reduced EV numbers - judging by the severity of anal itch - and that drinking kefir provided approximately a month's relief.
In many parts of the world, garlic has been traditionally considered to be an effective treatment for helminth infections and, although very large amounts would need to be consumed to kill hookworms, (see here) it has been suggested that using a clove of garlic as a suppository might act locally in the rectum to provide effective control of EV. [16]
Hosts of NA who wish to totally eradicate an EV infection could try using an anthelmintic that is known to be more effective against EV but less effective against NA, such as pyrantel pamoate. One self treater who tried using Combantrin (pyrantel pamoate) to terminate his NA colony found that it wasn't very effective against this species, and he was only able to kill all his hookworms by taking albendazole. Another anthelmintic that is recommended for the treatment of EV but which may be less effective against NA is pyrvinium. [17]