The Predominance of Single-Brood Infections in Human Ascariasis

Ascariasis is acquired by the ingestion of soil containing infective eggs of Ascaris lumbricoides. In the United States the infection is primarily a childhood disease, Cort, et al., 1930, Headlee, 1936, Beaver, 1952). It therefore appears probable that between the ages of 1 and 4 years. This is apparently due to the geophagous habit of children of this age rather than to the acquisition of an immunity as the child grows older, since adults are commonly infected in areas where the opportunity for ingestion of eggs exists. Not only can a history of dirt-eating be elicited in the case of most Ascaris infections but frequently the eggs of Ascaris can be recovered from the soil of the area in which the child is known to play (Brown, 1927, Cort, et al., 1930, Headlee, 1936, Beaver, 1952). It therefore appears probable that during favorable seasons these children may ingest numbers of infective eggs almost daily. It is a matter of some interest, whether a large percentage of these eggs can develop on successive occasions and thus massive infections can be acquired, or whether massive infections result only from the ingestion of a large number of eggs at once or during a short period. For convenience worms derived from eggs ingested at about the same time will be referred to as a brood. Observations by Dr. Paul C. Beaver since 1947 and by the writer since 1948 on the pediatric wards of Charity Hospital, where there is about 20 percent prevaence of ascariasis, have suggested that with few exceptions infection with a single brood of Ascaris is the rule. The present report is intended to call attention to this fact, which, though probably recognized by many parasitologists and physicians, appears not to have been placed on record. Ascaris lumbricoides were obtained from a total of 7 patients with massive infection either by medical treatment, or at surgery for removal of worms causing intestinal obstruction, or at autopsy. The worms were measured and their sexes determined.