Predisposition to hookworm infection in Papua New Guinea

Reinfection with hookworm (Necator americanus) following chemotherapy was s tudied over 8 years in a rural village in Madang Province, Papua New Guinea . Faecal egg counts were performed on up to 202 individuals in July 1988, A ugust: 1990 and November 1996; the study population was treated after sampl ing in 198 8 and 1990. Reinfection burdens in 1996 did not differ significa ntly from pretreatment burdens (in 1988), and were significantly higher tha n burdens in 1990. However, the prevalence of hookworm infection was signif icantly lower in 1996 than in either 1988 or 1990. There was significant pr edisposition to high or low bookworm burden between 1990 and 1996; this pre disposition was stronger in children than adults. However, there was no det ectable predisposition between 1988 and 1996 in individuals who had been tr eated 2 or more times between surveys. The mean weight of adult hookworms i n individual hosts was measured in 1988 and 1990 using worms expelled after chemotherapy. There was a significant positive correlation between mean ma le hookworm weight in the 2 years, suggesting that individual hosts are pre disposed to infection with heavy or light hookworms. These data suggest tha t differences in host susceptibility are involved in generating predisposit ion, but that longer-term variation in either exposure or susceptibility li mits the period over which significant predisposition can be detected.