The capacity of the third-stage larvae of Oesophagostomum bifurcum to survive adverse conditions

Human infections with the intestinal nematode Oesophagostomum bifurcum are commonly found in the Sudan savannah of northern Togo and Ghana. Apparently , the long and hot dry season in this region does not prevent transmission, which is believed to take place through ingestion of the infective, third- stage larvae (L-3) Oesophagostomum L-3 cultured from human stools, unlike t he larvae of Necator americanus, were shown to survive desiccation. In addi tion, 93% of the O. bifurcum L-3 frozen for 24 h at -15 degrees C regained motility when brought back into ambient temperatures. The L-3 also survived the acidity of an artificial mixture made to resemble the gastric juices o f humans. Desiccated larvae could even be rehydrated in this mixture, indic ating the possibility of dust-borne infections. The sturdiness of the L-3 i s likely to contribute to the high transmission intensity in northern Togo and Ghana.