Epidemiological evidence for a differential effect of hookworm species, Ancylostoma duodenale or Necator americanus, on iron status of children

Abstract

Background: The hookworms, Ancylostoma duodenale and Necator americanus, cause significant gastrointestinal blood loss. In clinical studies, greater blood losses have been reported with A. duodenale. However, there has been no evidence that endemic A. duodenale infection has greater impact than N. americanus infection on the iron status of populations.

Methods: In a sample of 525 school children in Pemba Island, Tanzania, we compared the degree of anaemia and iron deficiency associated with the two hookworm species at the individual and community (i.e. school) levels. Multiple regression was used to control for infection intensities and other child characteristics.

Results: In the 492 children with hookworm positive faecal cultures, haemoglobin and ferritin concentrations decreased with increasing proportions of A. duodenale. Among children with only N. americanus larvae, the prevalence of anaemia was 60.5 % and the prevalence of ferritin <12 microg/l was 33.1%, while in children with > or =50% A. duodenale larvae, the respective prevalences were 80.6% and 58.9%. When children were grouped by the prevalence of A. duodenale at the school level, children from high prevalence (> or =20%) schools had significantly worse iron deficiency and anaemia than children from low prevalence schools.

Conclusions: The species of hookworm being transmitted in a community influences the burden of iron deficiency anaemia in the community, and should be considered in prioritizing and planning programmes for hookworm and anaemia control.

PIP: Hookworms infect 1.3 billion people annually. Iron-deficiency anemia caused or exacerbated by intestinal blood loss is the major feature of hookworm infection, with such loss caused by the feeding of hookworms upon the intestinal mucosa. The hookworms Ancylostoma duodenale and Necator americanus cause major gastrointestinal blood loss. While relatively greater blood loss has been reported in clinical studies due to infection with A. duodenale, there has been no evidence that endemic A. duodenale infection has a greater impact than N. americanus infection upon the iron status of populations. The authors compared the degree of anemia and iron deficiency associated with these 2 hookworm species at the individual and community levels using a sample of 525 school children in grades 1-4 in Pemba Island, Tanzania, and controlling for infection intensities and other child characteristics through multiple regression. In the 492 children with hookworm-positive fecal cultures, hemoglobin and ferritin concentrations decreased with increasing proportions of A. duodenale. Among children with only N. americanus larvae, the prevalence of anemia was 60.5% and the prevalence of ferritin under 12 mcg/l was 33.1%. In children with 50% or higher proportions of A. duodenale larvae, the respective prevalences were 80.6% and 58.9%. Children from schools with high prevalences of A. duodenale infection had significantly worse iron deficiency and anemia than did children from low prevalence schools.