Epidemiology of Necator americanus hookworm infections in Xiulongkan Village, Hainan Province, China: high prevalence and intensity among middle-aged and elderly residents.

Hookworm is highly endemic to Hainan Province, an island located in the South China Sea. To investigate the prevalence and intensity of infection in the area, the village of Xiulongkan was surveyed between April and July 1998. A cross-sectional study was conducted in which fecal samples of 80% of the village residents (631 individuals) were tested for the presence of helminth eggs. Hookworm was the predominant intestinal helminth in Xiulongkan, where it was determined that 60% of those tested were infected. Necator americanus was the predominant species of hookworm in this population. The prevalence of hookworm increased with age, and then leveled to a plateau for ages 41 yr and up. This observation was in contrast to infections with Ascaris lumbricoides, where the highest prevalences occurred among school-aged children. Women had a significantly higher prevalence of hookworm than men and this difference emerged in early adulthood. The intensity of hookworm infection also significantly increased with age, with the highest intensity infections occurring among middle-aged and elderly residents. Females were more likely to have moderate or heavy infections, whereas males were more likely to have light infections. The rates of hookworm transmission are particularly high among the middle-aged and elderly residents of Xiulongkan.

Experimental approaches to the development of a recombinant hookworm vaccine.

Hookworm infection is a major parasitic cause of morbidity in the developing nations of the tropics. Development of a genetically engineered vaccine would be a useful tool in the control of this infection in highly endemic areas. Recombinant polypeptides belonging to the Ancylostoma secreted protein (ASP)-1 family have shown promise for reducing hookworm burdens after larval challenge infections in mice. Typically, these polypeptides are expressed in Escherichia coli and administered as an alum precipitate. Vaccine protection is antibody dependent. It is anticipated that a cocktail of different recombinant hookworm antigens may be required in order to effectively prevent heavy hookworm infections and disease. The progress of this work has been hampered by the absence of both a convenient laboratory animal with which to study hookworm infections resembling human infection, as well as the lack of easy availability of native hookworm antigens. In addition, useful human serologic correlates of antihookworm immunity are still poorly defined.