Plant molluscicides

Almost 40 years ago when, because my hobby was the study of non-marine molluscs, I was asked to try to name Bulinus and Biomphalaria bilharzia carriers for the Department of Insect-Borne Diseases in Nairobi, much use was made of such substances as copper sulphate and various pentachlorophenates for snail control. The disastrous ecological effects resulting from this can be imagined. I was therefore very interested when Or Teesdale in 1950 asked me to investigate the use of a plant as a potential snail-killer. My chemist friend Dr P. R. Hesse carried out an analysis and discovered saponins and rotenones. It was hoped that use of plants growing on the spot would prove a cheaper means of control and involve far less deleterious ecological consequences. Such attempts had been made with several plants eg Balanites since the mid-1930s. Snail control proved less successful than anticipated and bilharzia workers turned to curing patients combined with teaching them hygiene. Despite ever increasing activity by numerous bodies worldwide since schistosomiasis (bilharziasis) was discovered by Theodor Bilharz in 1851, enormous numbers of people are infected - estimated at present as between 200 and 300 million. Vast new irrigation schemes have of course greatly aggravated the problem.

The present work brings together papers presented at a meeting in Geneva of the Scientific Working Group on plant molluscides under the auspices of an UNDP/World Bank/WHO special programme. The first paper deals generally with the uses of molluscicidcs in control of the disease putting the history of those derived from plants in perspective with other control methods. Their mode of action is dealt with in the second paper. Much of the book is naturally taken up with detailed lists of plants with recognized or potential activity and their biochemistry and untapped sources of further information. The possibility of cultivating suitable plants is also discussed. Papers on lexicological screening, laboratory and field evaluation and work in China complete the book.

This is a series of exhaustive extremely well documented papers underlining the immense amount of work which has been accomplished mostly in the past quarter of a century. As an example of bringing together information from innumerable widely dispersed sources it is really quite masterly. The long lists of botanical names have certainly been scrutinised by someone knowledgeable and are not blighted by numerous spelling mistakes so frequent in other publications of a similar nature.