The control of schistosomiasis in man : chemotherapy, vaccination, or both ?

Abstract EN

As is the case of other helminth parasites in their definitive hosts, adult sehistosomes do not replicate in man.

The extent of disease, which depends directly on the num-bers of eggs deposited in the tissues by the female worms, therefore also depends on the actual numbers of worms that mature within the host, and the length of time that they are present, that is, on the intensity and duration of infection, rather than simply on its presence.

In communities living in endemic areas, the distribution of intensity of schistosome infection is highly overdispersed a small number of individuals har-bour most of the worms, and these are the ones who will go on to develop severe dis-ease.

The implication of this is that, for a control measure to be useful in reducing morbidity, it does not have to be totally effective in preventing transmission: any measure that even partially reduccs the establishment of the adult worms can have a great impact on morbidity, by markedly reducing the proportion of individuals who carry heavy worm burdens and therefore high tissue egg loads.

In other words, the aim of schistosomiasis control at the public health level can be the reduction of trans-mission, rather than its complete elimination.

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