The hookworms, Ancylostoma and Necator, draw a plug of intestinal mucosa into their buccal capsule. The tissue is broken down and blood is rapidly pumped through the intestine of the nematode so that most of it goes undigested.
The hookworms, Necator americanus and Ancylostoma duodenale, hatch as 1st-stage juveniles within the soil and develop to an infective 3rd-stage juvenile. Infection occurs by direct penetration through the skin of the host. Although the two species differ, they are both susceptible to environmental hazards such as desiccation (Hoagland and Schad, 1978). This limits their distribution to warm, wet climates such as the tropics. The 3rd-stage juvenile is also the infective stage of trichostrongyle nematodes, including those infecting sheep and cattle. Both the 1st-stage juvenile within the egg and the ensheathed infective juvenile are resistant to desiccation, chemicals and low temperatures (Wharton, 1982c; Wharton et al., 1984) and the infective juvenile can survive on pasture for several months before infecting a host.
Anderson (1982) suggests that the most appropriate control measures for hookworms and ascariasis are to concentrate chemotherapy on heavily infected individuals (taking advantage of overdispersion) and to improve sanitation to reduce the rate of transmission.