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

Abstract

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 (L₃). Oesophagostomum L₃ cultured from human stools, unlike the larvae of Necator americanus, were shown to survive desiccation. In addition, 93% of the O. bifurcum L₃ frozen for 24 h at -15°C regained motility when brought back into ambient temperatures. The L₃ also survived the acidity of an artificial mixture made to resemble the gastric juices of humans. Desiccated larvae could even be rehydrated in this mixture, indicating the possibility of dust-borne infections. The sturdiness of the L₃ is likely to contribute to the high transmission intensity in northern Togo and Ghana.