Rapport final du séminaire de modellisation apliquée pour l'optimisation des prises de décisions et du suivi des programmes de contrôle de la maladie du sommeil

714 ard, only slightly patchy and with few oddities. The summary of chagasic heart disease and the treatment of its symptoms is particularly good, although information on the management of mega-syndromesis more superficial. The distinction between Trvbanosoma rangeli and T. cruzi could have been dealt with-in more det&.‘It is strange that biphasic culture medium is not recommended as it still seemsto be the most sensitive and practical medium for the isolation of T. cruzi strains. Table 1 summarizes social risk factors for T. crwi infection from agricultural practices, land ownership and low income to the presence of roads, many of which factors are immutable in the context of immediate diseasecontrol strategies. On serology the report sits firmly on the fence, presenting too many tests and largely leaving the reader to decide which to use. More references would have been helpful. Of the Annexes, the first is a valuable summary of the recommendations of a WHO meeting in Panama (1985) on the nomenclature and identification of T. cr&i iso: lates. Annex 2 is a slightly idiosyncratic list of triatomine bug species: indications of the domestic, peridomestic or silvatic habitats and inclusion, in parentheses, of the few non-American species would have made this more complete. Annex 4 lists recorded mammalian hosts of T. cruzi and Annex 5 is a useful reminder that T. crwi is a laboratory hazard (emphasis on the safe handling of ‘sharps’the source of many laboratory infections-would have been helpful). Despite the value of this book it is likely to have little direct impact on the control of Chagas disease. The report does not claim to be a control manual but in attempting to hit all targets the focal point on control is elusive among indecisiveness and an overwhelming number of generalities. Not until page 60 do we get the clear statement that ‘an integrated control strategy contains one or more of the following four components: vector control, combined with sanitation of the peridomicilium; medical surveillance and control of transmission by blood transfusion; housing improvement; health education and community involvement.’ The crucial operational phases of vector control by insecticides appear briefly on page 61. Indeed so many cryptic options are given that this book could lead to despair among those concerned with the implementation of Chagas disease control. Could most of the background information at the beginning of the report have been assignedto Appendices? Could clear statements on control strategies, and then the methods, have been given earlier and separately for the politician, physician, community and research scientist? Towards the end the report falls into the trap of selfjustification with a bland reiteration of WHO research priorities. The recommendations are sensible but few are specific: ‘A national programme for the control and nrevention of Chaaas disease should be formulated and hplemented.. . N&ional programmes for control and prevention should focus on vector control, prevention of transmission via blood transfusion. . . the attack phase should consist of the wide-scale application of insecticides.. . make serological screening of blood donors legally mandatory when and where the risk of infected donors exists... T. crwi infection in mothers should not be a contra-indication to breast feeding.’ (Do resources really allow the systematic referral of ‘all persons found seropositive during seroepidemiological surveys, by blood transfusion services, or during pregnancy to a medical centre for a complete clinical examination for possible lesions due to Chagasdisease’?). In conclusion, this is an indispensable background text on Chagas disease: a book by experts, for experts, but perhaps better entitled ‘Chagas disease’ than ‘Control of ChagasDisease’. [Since this meeting there has been a WHO-sponsored international initiative on the co-ordination of strategies for the control of Chagas disease in the ‘southern cone’ countries of South America (see Schofield, C. J., 1992: Annales de la Sock%6Belge de Mkdecine Tropicale, 72, sup-

plement 1, 69-70; Miles, M. A., 1992: Parasitology Today, 8,221-222.1

M. A. Miles

Rapport final du skminaire de modellisation apliquke DOUTI’ootimisation des arises de dkisions et du suivi des probammes de co&rble de la maladie du sommeil. I. D. F. Habbema & A. De Muvnck (editors). Rot-

terdam: Universite Erasmus & CEC, 1992. Report no MGZ.9208. 218 pp. Price not stated. ISBN: 90-72245 06-7. There are 2 kinds of human African trypanosomiasis (HAT), the distinction between them being not only due to the causal agent, Trypanosoma brucei gambiense and T. b. rhodesiense, as the tropical medicine text-books state. It is rather that between the trypanosomiasis of international conferences and the one still afflicting the peoples of many rural areasin Africa, whose political importance is too small to deserve the attention of governments and health policy makers. Without prompt and effective treatment the fatality rate is nearly loo%, curtailing not onlv the individual lives of those infected but also hindering the social and economic development of the affected communities. This is one of the messagesthat comes acrossin this publication, clearly stated in the contribution by Van Nieuwenhove. The book consists of a collection of the papers presented at a seminar on applied modelling of sleeping sickness due to T. b. gambienseheld in Cote d’Ivoire during October 1991. It is structured in 4 chapters: (i) Introduction and objectives of the meeting, (ii) Natural history of sleeping sickness, (iii) Control policies and (iv) Modelling. Chapters 2 and 3 summarize the local history and experience of HAT control in several countries: Angola (Josenando), Congo (Ngampo), Equatorial Guinea (Simarro et al.), CBte d’Ivoire (Meda et al.), Uganda (Mbulamberi) and Zaire (Ekwanzala), and underline the disruption of relatively well established classical control programmes as a result of political and social unrest. The low sensitivity of the standard approach (case detection and treatment of the suspectsthrough lymph node palpation and demonstration of parasitesin blood, lymph node aspirates and cerebrospinal fluid) was compensated for by a wide population coverage through mobile teams (Van Nieuwenhove). This strategy managed to reduce the prevalence in the human host and it is claimed to have contributed to lower transmission rates even in the absenceof anti-vector measures.The rapid return to precontrol levels and the resulting epidemic proportions attained by the diseasein some areasafter the interruption of these activities is mentioned in many parts of the papers. The advantages of serological methods in community surveys (card agglutination trypanosomiasis test [CATT] on blood and serum, immunofluorescence), especially if used concomitantly with clinical diagnosis and more sensitive parasitological techniques (haematocrit centrifuge concentration, anion exchange column) is discussed (Molisho). The importance of an appropriate decision-making procedure in order to reach a correct diagnosis includes the question of whether or not to treat every putative case, due to the dangers associated with using the drug of choice especially for the phase of the disease involving the central nervous system (Jannin, Doua). The indispensable elements for the maintenance of control programmes (demand for them by the population, political will, human and financial resources, results and evaluation) are presented in a general context (Cattand) and more specifically in relation to campaigns against the vector (Laveissiere & Meda). Lancien points out the necessity of undertaking cost-effectiveness studies whilst Makubalo highlights the importance of socio-economicconsiderations. It is not very clear how these presentations lead to the fourth and final chapter on modelling which, according to the title, should be the core of the book. Perhaps the fact that this is not the caseis a reflection of the present status of sleeping sickness modelling. As a consequence, these proceedings are not (and do not pretend to be) an

715 authoritative account of the subject but rather the product of a preliminary concerted effort by the affected countries in the hope of developing a useful tool for research and control activities. It becomesobvious that the precise form of the relationship between the severity of transmission by the glossinid vectors and the associated prevalence in the human population is practically unknown (Mentens). Without it, accounts and expectations about lowering the intensity of transmission by passive and active case detection and treatment (reducing the human reservoir) and by vector control will remain emnirical. The notential role that animal reservoirs mav play in the e$demiology of gambiense sleeping sickness should be considered (Kaeeruka). Habbema describes‘su&inctly the concepts of mathematical modelling in medical sciencesand epidemiology, explaining the different types of approach and their objectives (deterministic and stochastic models, static and dynamic. analyses, analytical and numerical solutions, simulation techmques). His paper emphasizes microsimulation as a way to mirror individual host life-histories. A detailed explanation of ONCHOSIM (simulation model for human onchocerciasis designed within the Onchocerciasis Control Programme in West Africa) is given (Soumbey Alley), and efforts towards the development of the equivalent TRYPANOSIM are justified (Habbema & De Muynck). Finally, the definition, procedures, scope and limitations of the so-called ‘causal models’ are illustrated as a conceptual framework for potential use in the multidisciplinary and multivariate study of infectious disease epidemiology in general and of HAT in particular (De Muvnck et al.). The book is useful for workers in sleeping sickness, especially applied researchersand health officers and planners, since it provides a good and up to date summary of exoerience in the field: it contains verv little bioloeical noielty. However, the section on modelling is of int&est to those working in mathematical epidemiology, although no equation or formal expression should be expected. Instead, the arena for a much needed quantitative approach is prepared, without forgetting that even this will be useless in the absenceof political awareness of the problem and social commitment. Maria-Gloria

Bastiirez

The Control of Schistosomiasis. Second Report of the WHO Exert Committee. Geneva: World Health Or-

ganization, 1993. vii+86 pp. Price SW.fr. 12, US$ 10.80 (SW. fr. 8.40 in develonina countries). ISBN 92-4i20830-9. The first report of this committee was published in 1985. A quick comparison of the 2 reports (not an easy task as neither has an index, merely a Table of contents) suggeststhat there have been radical developments in the last 7 vears. The number of sections has grown from 7 to 22 plus references, acknowledgements and an annex giving indices for use in control programmes, though there are actually fewer pages. However, closer scrutiny shows that many of the new sections are merely upgraded subsections from the original report, presented in a different order. Three introductory sections outline the public health im ortance of schistosomiasis and the strategy for its contra P, based on the previous report. Briefly, this relied heavily on various forms of community chemotherapy using praziquantel (or oxamniquine and metrifonate for Schisioioma t%ansoniand S. hahatobium respectively) to reduce morbiditv to nublic health insignificance. Possible bonuses included at least tempo&y transmission control and even elimination of the parasites. Such bonuses were unlikely, though, without public health education and supplementary measuresto control transmission directly. Integration with horizontal primary health care (PHC) was perceived as a way of minimizing costs. The next 10 sections of the current report cover various aspectsof the strategy of control, from current status, selection of strategies and adaptation to meet local requirements, to data management, global monitoring and policy conclusions. Another 6 sections deal with _

I

technical issues involving disease manifestations, the parasites, the snails, water supplies, sanitation and chemotherapy. The final group of 3 sections reviews progress (sometimes, but not always, since 1985) in control in 24 countries, and includes a summary of conclusions and a list of 11 recommendations. But what is new in this second report? Well, some lessons have been learned from active control nrogrammes, although there is some disparity between those& China; Egypt -- _ and Brazil covering wnulations of millions at risk. and those in Indonesia and southern Morocco involving only a few thousand people. This does emphasize the nredictable diversity of nroblems faced bv different countries where schistosoiniasis is endemic-There has also been a tacit redefinition of PHC which now appears to mean the lowest echelon of the existing, conventional health services rather than (voluntary) workers recruited from within a community. Devolvement of responsibility for control to regional and local centres is urged, plus integration with other agencies, especially those concerned with water and agriculture development problems, to increasethe probability of success.Paradoxically, the most successful programmes reported had a strong central or vertical component to co-ordinate, support and service local activities. The need for long-term commitment is stressed?especially after the successwhich usually follows an mitial chemotherapy programme: rarely, if ever, has schistosomaisis been controlled by one or 2 simple treatment programmes. Greater emphasis is now placed on programmes to control S. haematobium, partly because it is now considered that subjects needing treatment can be identified by simple, non-invasive methods, possibly even by questionnaires. Control programmes aimed at schoolchildren are also recommended. The greatest technical development is the introduction of portable ultrasound scanners suitable for non-invasive field screening of communities for pathological conditions and changes after treatment. However, interpretation of ultrasound findings is not always straightforward and there is a danger that the detection of additional lesions, which may not be of great significance, could create a-demand for action in &den& countries unable to afford it. Costs remain one of the limitincr factors affecting the introduction of control program&es. A glaring omission from the list of recommendations is a plea for the development of antigen detection in urine to produce a simple, specific, non-invasive immunodiagnostic test suitable for field use. Overall. then. this is a useful. well-nroduced summarv of the current status and concebts of how schistosomiasis control should proceed, of some of the difficulties likely to be encountered, and how attemnts may be made to solve them. The report is clearly printed and presented, although there is some repetition in different sections. The list of references is distinctly limited: reports from or commissioned by various international bodies are interspersedwith a somewhat idiosyncratic selection of primary sources. Unfortunately, a number of interesting and sometimescontentious statements in the text have no reference attached. Nevertheless, anyone with any interest in schistosomiasis will find much of value in this report. R. F. Sturrock Lymphatic

Filariasis:

the Disease

and its Control.

Fifth Report of the WHO Expert Committee on Filariasis. Geneva: World Health Organization, 1992. Technical Report series, no. 821. vi+71 pp. Price SW. fr. 10, US $9 (in developing countries, SW. fr. 7). ISBN 92-4120-821-X. [Available in English; French and Spanish versions in preparation.] Resplendent in its new attractive format, this report of a World Health Organization Expert Committee, which met in October 1991, gives an excellent introduction for the newcomer to lymphatic filariasis and its control and a useful broad update for those already interested in this fascinating disease.Despite being rather short, the report covers the epidemiology, diagnosis, clinical, socio-econ-