Pathogenesis and immunity in hookworm infection

The species of hookworm that parasitize man and his dog can be segregated according to whether or not the adult hookworms induce intestinal haemorrhage. By radioisotope tracer techniques, it has been shown that the 3 hookworms which infect man (Ancylostoma duodenale, Necator americanus and Ancylostoma ceylanicum) and 1 (Ancylostoma caninum) of the 3 in dogs, are prodigious blood-suckers. The haematophagous appetites of these 4 hookworms constitute the primary pathogenic mechanism of ancylostomiasis. Since it appears that whole blood is lost into the intestine, the strain on protein, particularly albumin, metabolism must not be overlooked. The other 2 hookworms that infect dogs (Ancylostoma braziliense and Uncinaria stenocephala) do not appear to cause significant haemorrhage although hypoproteinaemia ensues as a consequence of loss of plasma protein into the intestine. Some aspects of the development of a polyvalent X-irradiated vaccine for hookworm disease of dogs are reviewed, with particular emphasis on the mechanisms by which vaccinated dogs resist the potential pathogenesis of challenge infections. Circumstantial evidence, which suggests that man also develops immunity to reinfection with hookworms, is discussed in the light of the findings from experiments with vaccinated dogs, and with reference to the hypothetical benefits that might be conferred on children by vaccination.