The dynamics of helminth infections, with special reference to schistosomes

Long-term outcomes of school-based treatment for control of urinary schistosomiasis: a review of experience in Coast Province, Kenya

“…This strategy grew out of earlier observations on the local distribution of S. haematobium infection and disease in Coast Province (Warren et al 1979, King et al 1988, and more general considerations of the dynamics of parasite transmission and of the known heterogeneity of infectious burden and of parasite transmission potential (Anderson & May 1982, Warren 1982, Jordan 1985. In particular, consideration was given to the possibility that broad treatment coverage amongst the most heavily infected segment of the population (i.e., schoolchildren) might, in fact, reduce overall community transmission by sufficiently suppressing parasite worm burden to a transmission 'break point', below which successful parasite mating could no longer efficiently occur (MacDonald 1965).…”

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): I. Efficiency of diagnostic and treatment procedures

“…Although the impact of chemotherapy on egg counts has not been immediately evident, a reduction of the number of eggs discharged into water bodies will eventually result. As remarked by MacDonald (1965), a small number of S. mansoni eggs discharged into the environment will sustain the transmission of this parasite. That is why the stress on proper sanitation can not be overestimated.…”

Modelling Parasite Transmission and Control

“…McDonald's use of the early malaria models to show that killing adult mosquitoes would be particularly effective in reducing infection transmission was a major advance in demonstrating the usefulness of theoretical analysis and population dynamics modelling in particular for guiding parasite control programmes, and since then parasite transmission models have also been used to guide the onchocerciasis control programme in Africa (Habbema et al, 1992), as well as for investigating best strategies for controlling a host of other parasites, including tuberculosis, trachoma and lately helminth infections, such as schistosomiasis and filariasis (Chan et al, 1995;Laing et al, 2007;Michael et al, 2004). The importance of this work is highlighted by greater understanding of threshold phenomena in transmission dynamics leading to the concept that natural "breakpoints" occur below which parasite systems will go extinct to the roles that worm mating behaviour and infection aggregation can play in both helminth transmission and control (Hairston, 1962;Macdonald, 1961Macdonald, , 1965. The emerging trend from this work is thus the increasing use of understanding parasite transmission dynamics via the construction and analysis of mathematical models for use in guiding the development of informed parasite control strategies, so much so that this twin objective, viz improving understanding of parasite transmission dynamics and applying models to guide parasite control, has almost become a de facto goal of most recent work in parasite transmission modelling.…”