Intestinal Canthariasis Due to Tenebrio molitor

Abstract

Canthariasis (Osler's scoleciasis), or accidental parasitism by coleopteran (beetle) larvae in man, is a rather rare and poorly known entity. The disease is to be distinguished from myiasis and scholeciasis, infection by dipteran (fly) and lepidopteran (moth) larvae, respectively. The r6ole played by several species of beetle larvae as intermediate hosts for the tapeworm HyInenolepis dininitta has aroused more interest than the primary larval infection itself. That canthariasis can be a disturbing and persistent illness is illustrated by the case herein reported. Beetle larvae have been recovered from several parts of the human body. Hinman and Faust (1932), who have summarized the early literature on the subject, report a case of infection of the tonsils by Tenebrio molitor larvae, discovered at tonsillectomy. Three centuries ago Tulpius (1652) told of the recovery of beetle larvae from a patient's nose and from another patient's urinary bladder. Bateman (1811) added a case of infection of the umbilicus. The gastrointestinal tract, however, is the usual habitat of parasitizing beetle larvae (Brumpt, 1927; Hinman and Faust, 1932). Senior-White (1920) reports that in India intestinal infection with larvae of Onthophagus bifasciatus (SCARABEIDAE) is common enough to have a vernacular name. Nevertheless the phenomenon of canthariasis is accidental, there being no obligate coleopteran parasite of man. Beetle larvae in the bowel are in a wholly unnatural environment, and, although they can continue to thrive and develop here temporarily, they must eventually be passed out. Since pedogenesis is not known to occur in these beetle larvae, there is probably no multiplication within the bowel. Although several species are involved, the beetle usually responsible for gastrointestinal canthariasis is Tenebrio molitor, the dark mealworm, which is commonly found in grains, milled cereals, flour, bran, meals, bread, and meat scrap. The life cycle is completed in one year in this medium (Cotton, 1940), and any stage may be accidentally ingested. Although beetle larvae are considerably more resistant to deleterious influences than are larvae of other types of food-infesting insects, it must be assumed that the usual cereal cooking processes regularly kill them. The danger lies in breakfast foods and precooked cereals. is uncertain whether gastrointestinal canthariasis ordinarily follows the ingestion of the insects in the egg or in the larval form. Senior-White (I.c.) makes the statement, It is probable that whilst in the intestine the larvae are faecal feeders, but how, and at what stage, they get there . . . is unknown. seems likely that unmasticated larvae may survive, to be passed eventually by rectum. That latestage larvae can be present as high in the gastrointestinal tract as the stomach without any known method of maintaining their position there while developing from the egg, is well known from vomitus and post-mortem examinations (Pickells, 1824; Riley and Howard, 1889). On the other hand, when infants pass large numbers of larvae, as in the case here presented, the phenomenon is best explained by the previous ingestion of eggs.