The epidemiology of human hookworm infections in the southern region of Mali

Two surveys of hookworm (Necator americanus) infections, conducted three years apart (December 1994 and January 1998) in a village in the Sikasso region of Mall, revealed that overall prevalence of infection was 68.7% and 53%, respectively. In both years there was a highly significant difference between the sexes in the prevalence and abundance of infection, with male subjects carrying heavier infections than females. Both prevalence and abundance of infection increased with age, although in 1998 there was a strong interaction between sex and age, arising from the declining egg counts among 16-20-year-old females and the continuing increase among males, reinforced by the subsequent reduction among the older males (greater than or equal to 61 years) and concomitant increase among females. After controlling for the effects of age, sex and their interaction, a highly significant positive relationship was detected between faecal egg counts of individuals who were examined in both 1994 and 1998 (n = 134), indicating predisposition to infection. This relationship remained significant in each of 4 age classes spanning 7-79 years. The members of some family compounds were shown to carry heavier infections than expected whilst others were less infected, suggesting compound-related clustering of hookworm infections. The use of footwear increased with age but there was no significant relationship between the extent of use of footwear and the abundance of hookworm infection. Eyesight deteriorated with age and impaired vision was particularly prominent among the older sectors of the community, a legacy from the time when onchocerciasis was widely prevalent in the region, Although men with partially damaged eyes carried lower infections than expected for their age, no overall significant relationship was found between quality of Vision and hookworm infections. These results are discussed in relation to hookworm epidemiology in general and in Mali in particular.