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Living together the biology of animal parasitism
98
Parasitology Today, vol. 3, no. 3, 1987
and sludge are stored. Frequent emptying is required. The cesspool could then be considered as an expensive variant of the vault system. Latrines can also be designed to permit the transformation of the excreta into a form of compost which can safely be used as fertilizer. This will encourage people to empty such compost toilets regularly. The twin pit VIP latrine is a kind of compost~ng latrine. Experimemts with other types in which the composting process is accelerated (thus permitting a smaller chamber and more frequent emptying) have shown them to be unsuitable for many developing countries, although one type has found widespread application and acceptance in Vietnam and has been successfully tried in Guatemala. In the Vietnamese composting latrine there are two chambers: urine is not allowed to enter them, ash is added after each use, and each chamber is sealed for two months when it is full, after which the compost is removed and applied to the land. Obviously, latrines of this type cannot be introduced into a new area without an enormous supporting effort in communication, education and evaluation to ensure that they are being properly used. The need for such a supporting programme increases the cost of compost toilets.
they may be prepared to spend larger sums over a short period of time. The relative costs of different types of system vary widely between different countries, but there are few people ~n the world so poor that an acceptable, affordable system cannot be designed for them. High quality VIP latrines or pourflush toilets can be built for one tenth of the cost of conventional sewerage, or as little as US $30 per head. In rural areas, costs can be reduced still further by the use of local materials. We have all the tools we need for sanitation at low cost. Now it is time to get on with the job.
Sandy Cairncross is an Environmental Health Engineer at the London School of Hygiene and Tropical Medicine, Keppel Street, London WCI ETHT, UK.
iiiiiiiii~iiii!/ii~,~/ii~ ~ii~¸i
Living T o g e t h e r T h e Biology of A n i m a l Parasitism
Choosing a System
by William Trager, Plenum Press, New York 1986. US$59.50 (xii + 467 pages) ISBN 0 306 42310 3
All the recommended systems can be made to operate hygienically, so that the choice of the most suitable excreta disposal system can be made on the basis of cost, convenience and feasibility. These will depend on many factors (Table 2) but two considerations are fundamental. First, it is essential to involve the potential users in the decision from the earliest possible stage, and it is often helpful to build several pilot models for demonstration purposes. These can also be used to experiment with different construction materials and design modifications to find the version which is most suitable and most popular. There is no need to limit the choice to a single system for a whole community, and there will often be advantages in offering two or more models from which each household can choose the one they prefer. Second, there is little use in promoting an excreta disposal system which people cannot afford, so that cost should be a major consideration. In general, low-income communities will not be prepared to spend more than about 2 - 3 % of their income on excreta disposal, although
Professor Trager has written a book which captures the excitement of modern animal parasitology. The recent advances in molecular and cellular biology, together with those in immunology, have given us ideas and techniques which have made possible more detailed studies of the intricate relationship between parasite and host. The benefits of these studies to our understanding of this relationship are described clearly in this excellent book. The author reveals his wealth of knowledge of protozoal and metazoal parasites and their strategies for survival, derived from a long and distinguished career in parasitology. But that is not all. A problem solved reveals a host (perhaps an inappropriate term here) of other problems and it is a most important featu re of this book that questions are asked and areas of ignorance noted. This is not a classical parasitology textbook with a comprehensive survey of parasites -indeed this approach is restricted to a series of well-illustrated life cycles in Chapter I. Indeed the emphasis is on the parasite-host relationship and the adaptations made by parasites for the different conditions they experience
References I Cart, W.W., Otto, G.F. and Spindler, L.A. (1930)Am j. Hyg 10, 614-625 2 Feachem,R.G. et al. (.I 983) Trans. R Sac Trap. Meal. Hyg. 77, 4, 515-52 I 3 Schad,G.A. and Anderson, R. (I 985) Science 228, 1537-1540 4 Glickman, L.T et al. (1981)Am.j. Trap. Med Hyg. 30, 7~80 5 Halsted,J.A. (1968)Am.j Ctin. Nut. 2 I. 1384-
393 6 Bundy, D.A.P. (1986) Trans. R. Sac. Trap. Med Hyg 80, 706-718 7 Kalbermatten. J.M. et al. (1980)Appropriate Technologyfor Water Supplyand Sanitation(Vols I 12).The World Bank,Washington DC 8 Cairncross,S. (1986) SmallScaleSanitation(Ross Bulletin, No. 8), Ross Institute of Tropical Hygiene,London 9 Carroll, R.F. (1984) BREVAC: A mechanized methodof emptyingsanitationchambersBREInf. Paper 1/84. Building Research Establishment. Watford. UK I00kun. D.A. and Ponghis,G. (1975) Community Wastewater Collection and D~sposal 276 pp.. WHO, Geneva II Britrsh Standards Institution (1968) Sewerage BSCP2005, 124 pp.
during the various stages of complex life cycles. The book can roughly be divided into three sections. The first chapters deal with the mechanisms of invasion, the establishment of infection, the hostparasite interface, nutrition and respiration. In addition a chapter on in vitro cultivation is a delightful reminder that this approach is as much a tool for scientific investigation as a means of mass production. The biochemistry, molecular biology and genetic control of differentiation are described with characteristic luad~ty - t o o often the understanding and enjoyment of these fields for the general reader is clouded by a plethora of esoteric jargon. A second group of chapters are more concerned with the host response, and range from those d~scussing broader issues (innate immunity, the spleen) to those devoted to specific responses to, for example, trypanosomes, malaria and schistosomes. The inclusion of a chapter on invertebrate immunity is commendable. The last section is a miscellany; it includes a fascinating discussion of symbiosis and forays into chemotherapy and ecological control. All chapters are well illustrated with tables, figures and micrographs, and supplemented with a short bibliography (references into 1985). This fascinating and well written account should be read by parasitologists of all kinds. It ~s accessible to students (other than price), highly recommended for specialists moving into parasitology and should provide enjoyment (and education) to those already established in the field.
S.L Croft Wetlcome ResearchLaboratories Beckenham.KentBR3 3BS.UK
Parasitology Today, vol. 3, no. 3, 1987
and sludge are stored. Frequent emptying is required. The cesspool could then be considered as an expensive variant of the vault system. Latrines can also be designed to permit the transformation of the excreta into a form of compost which can safely be used as fertilizer. This will encourage people to empty such compost toilets regularly. The twin pit VIP latrine is a kind of compost~ng latrine. Experimemts with other types in which the composting process is accelerated (thus permitting a smaller chamber and more frequent emptying) have shown them to be unsuitable for many developing countries, although one type has found widespread application and acceptance in Vietnam and has been successfully tried in Guatemala. In the Vietnamese composting latrine there are two chambers: urine is not allowed to enter them, ash is added after each use, and each chamber is sealed for two months when it is full, after which the compost is removed and applied to the land. Obviously, latrines of this type cannot be introduced into a new area without an enormous supporting effort in communication, education and evaluation to ensure that they are being properly used. The need for such a supporting programme increases the cost of compost toilets.
they may be prepared to spend larger sums over a short period of time. The relative costs of different types of system vary widely between different countries, but there are few people ~n the world so poor that an acceptable, affordable system cannot be designed for them. High quality VIP latrines or pourflush toilets can be built for one tenth of the cost of conventional sewerage, or as little as US $30 per head. In rural areas, costs can be reduced still further by the use of local materials. We have all the tools we need for sanitation at low cost. Now it is time to get on with the job.
Sandy Cairncross is an Environmental Health Engineer at the London School of Hygiene and Tropical Medicine, Keppel Street, London WCI ETHT, UK.
iiiiiiiii~iiii!/ii~,~/ii~ ~ii~¸i
Living T o g e t h e r T h e Biology of A n i m a l Parasitism
Choosing a System
by William Trager, Plenum Press, New York 1986. US$59.50 (xii + 467 pages) ISBN 0 306 42310 3
All the recommended systems can be made to operate hygienically, so that the choice of the most suitable excreta disposal system can be made on the basis of cost, convenience and feasibility. These will depend on many factors (Table 2) but two considerations are fundamental. First, it is essential to involve the potential users in the decision from the earliest possible stage, and it is often helpful to build several pilot models for demonstration purposes. These can also be used to experiment with different construction materials and design modifications to find the version which is most suitable and most popular. There is no need to limit the choice to a single system for a whole community, and there will often be advantages in offering two or more models from which each household can choose the one they prefer. Second, there is little use in promoting an excreta disposal system which people cannot afford, so that cost should be a major consideration. In general, low-income communities will not be prepared to spend more than about 2 - 3 % of their income on excreta disposal, although
Professor Trager has written a book which captures the excitement of modern animal parasitology. The recent advances in molecular and cellular biology, together with those in immunology, have given us ideas and techniques which have made possible more detailed studies of the intricate relationship between parasite and host. The benefits of these studies to our understanding of this relationship are described clearly in this excellent book. The author reveals his wealth of knowledge of protozoal and metazoal parasites and their strategies for survival, derived from a long and distinguished career in parasitology. But that is not all. A problem solved reveals a host (perhaps an inappropriate term here) of other problems and it is a most important featu re of this book that questions are asked and areas of ignorance noted. This is not a classical parasitology textbook with a comprehensive survey of parasites -indeed this approach is restricted to a series of well-illustrated life cycles in Chapter I. Indeed the emphasis is on the parasite-host relationship and the adaptations made by parasites for the different conditions they experience
References I Cart, W.W., Otto, G.F. and Spindler, L.A. (1930)Am j. Hyg 10, 614-625 2 Feachem,R.G. et al. (.I 983) Trans. R Sac Trap. Meal. Hyg. 77, 4, 515-52 I 3 Schad,G.A. and Anderson, R. (I 985) Science 228, 1537-1540 4 Glickman, L.T et al. (1981)Am.j. Trap. Med Hyg. 30, 7~80 5 Halsted,J.A. (1968)Am.j Ctin. Nut. 2 I. 1384-
393 6 Bundy, D.A.P. (1986) Trans. R. Sac. Trap. Med Hyg 80, 706-718 7 Kalbermatten. J.M. et al. (1980)Appropriate Technologyfor Water Supplyand Sanitation(Vols I 12).The World Bank,Washington DC 8 Cairncross,S. (1986) SmallScaleSanitation(Ross Bulletin, No. 8), Ross Institute of Tropical Hygiene,London 9 Carroll, R.F. (1984) BREVAC: A mechanized methodof emptyingsanitationchambersBREInf. Paper 1/84. Building Research Establishment. Watford. UK I00kun. D.A. and Ponghis,G. (1975) Community Wastewater Collection and D~sposal 276 pp.. WHO, Geneva II Britrsh Standards Institution (1968) Sewerage BSCP2005, 124 pp.
during the various stages of complex life cycles. The book can roughly be divided into three sections. The first chapters deal with the mechanisms of invasion, the establishment of infection, the hostparasite interface, nutrition and respiration. In addition a chapter on in vitro cultivation is a delightful reminder that this approach is as much a tool for scientific investigation as a means of mass production. The biochemistry, molecular biology and genetic control of differentiation are described with characteristic luad~ty - t o o often the understanding and enjoyment of these fields for the general reader is clouded by a plethora of esoteric jargon. A second group of chapters are more concerned with the host response, and range from those d~scussing broader issues (innate immunity, the spleen) to those devoted to specific responses to, for example, trypanosomes, malaria and schistosomes. The inclusion of a chapter on invertebrate immunity is commendable. The last section is a miscellany; it includes a fascinating discussion of symbiosis and forays into chemotherapy and ecological control. All chapters are well illustrated with tables, figures and micrographs, and supplemented with a short bibliography (references into 1985). This fascinating and well written account should be read by parasitologists of all kinds. It ~s accessible to students (other than price), highly recommended for specialists moving into parasitology and should provide enjoyment (and education) to those already established in the field.
S.L Croft Wetlcome ResearchLaboratories Beckenham.KentBR3 3BS.UK