Guide to Human Helminths

Three hundred and forty one species of helminth, which have been found in association with humans, are listed in this book. "Helminth" is usually used to describe a worm having an obligatory requirement for a relationship with a living host of a different species. The book covers both rare and common infections and provides summaries for each species of helminth and includes information on classifiction, nomenclature, host range, life history, geographical distribution, mode of transmission to humans and contribution to disease. Many of the species of worm listed here undoubtedly deserve the status of parasite; "Ascaris lumbricoides" and "Schistosoma haematobium" are highly prevalent, widely distributed and are recognized in all forms of parasitological literature as parasites of humans. Other species of worm that have occasionally been observed in contact with human tissue may eventually be discarded from this list. For example, a single specimen of "Nybelinia surmenicola" was found attached to a tonsil some hours after the patient had eaten raw squid. A critical discussion of the strength and specificity of different associations between helminths and their hosts has been presented by Prudhoe and Bray (1982). The theme taken by Norman Stoll for his presidential address to the American Society of Parasitologists, meeting in Boston in December 1946, was to ask and attempt to answer the question "just how much human helminthiasis is there in the world?" (Stoll, 1947). Estimates of numbers of millions of cases for what Stoll judged to be the common species of helminth parasite of humans are reproduced in Table 1. The values shown in the table have often been derived from data which was not always obtained under ideal conditions. Counting cases relies on appropriate and standardized sampling methods and diagnostic techniques leading to comparable results. Extension of the results from epidemiological surveys to cover an entire country must be based on accurate knowledge of the helminth's distribution in that country. "Ascaris lumbricoides" clearly has an uneven or patchy distribution in many regions (Crompton and Tulley, 1987; Crompton, 1988).