[Cercarial dermatitis in Europe: a new public health problem?]. / La dermatite cercarienne en Europe: un problème de santé publique nouveau?

Cercarial dermatitis is a parasitic impasse that has worldwide distribution. The condition manifests itself as a highly pruriginous skin rash and is due to penetration of the dermis by larval stages (furcocercariae) of avian trematodes. Many species may be responsible for this disease. In Europe the genus Trichobilharzia is widely represented, in particular by the species T. ocellata; the definitive host is the duck (Anas platyrhinchos); the intermediate hosts are snails of the genus Lymnea (L. ovata or L. stagnalis). In France, cases of cercarial dermatitis were reported in June and July 1994 to the health authorities of three départements in the Pays de la Loire Region (western France). The epidemiological situation, common to the three maintained ponds that were concerned, is as follows: high level of eutrophication of the sites, colonization of the ponds by L. ovata, and settlement by many duck colonies. The simultaneous occurrence of these three phenomena, combined with long hours of sunshine in the summer, is responsible for most of the foci of cercarial dermatitis recently described in Europe. Control of this condition is difficult, requiring strict maintenance of bodies of water and if necessary the use of molluscicides such as niclosamide. The use of praziquantel in baits for treating the definitive hosts appears to interrupt the natural cycle of the avian Schistosomatidae. In the light of the observations reported here and the analysis of recent publications, cercarial dermatitis may be regarded as an emerging disease. Its public health impact needs to be evaluated at the global level.

New geographical approaches to control of some parasitic zoonoses.

The advent of new technology for geographical representation and spatial analysis of databases from different sectors offers a new approach to planning and managing the control of tropical diseases. This article reviews the geographical and intersectoral aspects of the epidemiology and control of African trypanosomiasis, cutaneous and visceral leishmaniasis, Chagas disease, schistosomiasis, and foodborne trematode infections. The focal nature of their transmission, increasing recognition of the importance of animal reservoirs, and the need to understand environmental factors influencing their distribution are common to all these diseases. Geographical information systems (GIS) open a completely new perspective for intersectoral collaboration in adapting new technology to promote control of these diseases.

Enfermedades parasitarias y desarrollo hidraúlico: necesidad de una negociación intersectorial / Enfermedades parasitarias y desarrollo hidraúlico: necesidad de una negociación intersectorial / Parasitic diseases in water resources development : The need for intersectoral negociation

La explotación de los recursos hídricos es un requisito esencial para una amplia gama de actividades humanas, en particular la agricultura y la producción de energía. Sin embargo, hoy se conocen cada vez mjeor los posibles efectos negativos de ese aspecto del desarrollo, entre los que destacan el aumento de la prevalencia de ciertas parasitosis en la población de las zonas vecinas. No obstante, apenas se han tomado medidas eficaces para contrarrestar esos efectos de los proyectos hidr—licos, tanto en la fase de planificación como al aparecer los primeros signos alarmantes, y de hecho el sector sanitario tiende a estar mal preparado para hacer frente a estos problemas

En el presente volumen se examinan los efectos de los proyectos de explotación de recursos hídricos en cuatro enfermedades parasitarias: la esquistosomiases, el paludismo, la filariasis linfática y la oncocercosis, todas las cuales pueden prevenirse o combatirse actualmente con los conocimientos disponibles. A continuación se exponen algunas posibles medidas para proteger a la población en los proyectos de ese tipo, indicando las estrategias de negociación intersectorial que pueden aplicar los funcionarios de sanidad y las modalidades de preparación de un plan sanitario para un proyecto hidr—lico. A lo largo

Parasitic diseases in water resources development : The need for intersectoral negociation / Parasitic diseases in water resources development : The need for intersectoral negociation

This book reviews the effects of water resources development on four parasitic diseases- schistosomiasis, malaria, lymphatic filariasis, and onchocerciasis- stressing that, with current knowledge, these diseases are amenable to prevention or control. It then describes some possible steps towards obtaining the best possible protection for health in development projects, outlining intersectoral negotiating strategies for health officials and the preparation of a health plan for a water resources project. Throughout the analysis, the authors stress the need for the health sector to be actively involved in integrated development activities, incorporating health protection and promotion measures along with economic advancement

Liver ultrasound findings in a low prevalence area of S. japonicum in China: comparison with history, physical examination, parasitological and serological results.

The paper describes a study carried out in a community in Dongdian township, Anhui Province, People's Republic of China. Medical history and the results of a physical examination, ultrasound investigation, parasitological and serological tests for Schistosoma japonicum infection were compared in 661 persons of 169 households. A lack of correlation between parasitological and serological indicators of infection and morbidity was observed in this area of low (6.4%) prevalence and intensity of infection. The prevalence of abnormal ultrasound findings in the liver in this population was high (56%), and was significantly higher than the prevalence of S. japonicum infection. The abnormal ultrasound findings correlated with a history of schistosomiasis, and the correlation increased significantly according to the number of times treated and the time since the last treatment, which suggested that past parenteral treatment has a role in the high rate of abnormal liver ultrasound findings. The significant correlation between the qualitative and quantitative serological results and abnormal ultrasound parenchymal patterns suggests that cross-reactivity between the etiology of the parenchymal disease and these tests is occurring. The presence of HBsAg correlated with the composite presence of ultrasound abnormalities of the liver parenchyma: increased echogenicity, periportal fibrosis and/or nodules and irregular fibrosis, whereas a normal ultrasound pattern was associated with the absence of HBV antigenemia.

Selective population chemotherapy among schoolchildren in Beheira governorate: the UNICEF/Arab Republic of Egypt/WHO Schistosomiasis Control Project.

Selective population chemotherapy using a single dose of praziquantel (40 mg per kg body weight), which was offered to 29,365 schoolchildren in Abu El Matameer and 40,241 in Abo Homos districts, Beheira governorate in the Nile delta, reduced the prevalence of schistosomiasis from 75.4% to 40.9% (reduction of 45.8%) and from 80.5% to 30.8% (reduction of 61.7%), respectively. Of those with only S. mansoni infection, 10.6% before treatment and 1.7% one year later had more than 800 eggs per gram of faeces. The prevalence of S. haematobium in Abu El Matameer was reduced from 35.4% to 7.4% after a single treatment. Infections with both S. mansoni and S. haematobium were reduced by more than 90% after one year. These reductions in prevalence and intensity of schistosomiasis in the face of continuing transmission and water contact augur well for the future role of chemotherapy in control programmes.

Global schistosomiasis database: practical considerations in the design of a user-friendly database.

A computerized database for monitoring global schistosomiasis data is discussed. The potential target users include schistosomiasis program managers, Ministries of Health of endemic countries, consultants, and WHO Regional Offices. The concept behind the design of the database structure, the user interface and the query interface is addressed along with a brief description of the hardware and software used. The database, holding information on 76 schistosomiasis endemic countries around the world, has been tested in the WHO Regional Offices with positive results.

The epidemiological implications of a multiple-infection approach to the control of human helminth infections.

It has been suggested that there is economic advantage in using a single community therapy programme to deliver multiple treatments against several parasitic infections. This preliminary study estimates the occurrence of concurrent helminth infection in Africa and Brazil to determine whether such an approach is justified epidemiologically. The results indicate that the occurrence of geohelminthiasis with schistosomiasis is sufficiently frequent in some areas of both Africa and Brazil for a combined approach to control to be appropriate, but that the relatively low frequency of occurrence of onchocerciasis with other infections would justify a multi-infection approach to control at specific foci only.

International Commission for Protection Against Environmental Mutagens and Carcinogens. ICPEMC publication No. 18. Review of the genotoxicity and carcinogenicity of antischistosomal drugs; is there a case for a study of mutation epidemiology? Report of a task group on mutagenic antischistosomals.

One of the interests of ICPEMC is to identify situations in which the possible induction of inherited defects in man by mutagen exposure could actually be studied. The large-scale use of mutagenic drugs in field programmes against schistosomiasis, mainly during the 1970's, was considered a possible case. An ICPEMC task group approached the problem by (1) updating the genetic toxicology data base for antischistosomal drugs, and (2) reviewing possible study areas. Expertise was combined from genetic toxicology, mutation epidemiology and tropical medicine. It was considered that: (a) if any, hycanthone would be the most appropriate candidate drug for study; (b) it would be virtually impossible to meet the basic requirements of an appropriate mutation epidemiology study, in endemic countries; (c) as more defined genetic endpoints would be selected (e.g. sentinel phenotypes) the required large sample sizes would seem prohibitive, since documentation on past programmes is limited and local demography would render the reliable tracking of substantial numbers of offspring of treated persons an almost impossible task; (d) in most endemic countries proper diagnosis and registration of inherited defects is largely lacking; (e) the problems encountered in demonstrating inherited effects in humans after heavy or chronic exposure to established animal mutagens such as ionizing radiation and cancer chemotherapy, in combination with the ambiguous nature of the animal germ cell data with hycanthone, do not particularly warrant large expectations; (f) since non-mutagenic antischistosomal drugs are now in use, the problem is academic and of low priority in the endemic countries whose medical and research resources are often limited. Thus, studying offspring of hycanthone-treated people to demonstrate the mutagenic potential of the drug in man is not a viable enterprise.

ZOOM: a generic personal computer-based teaching program for public health and its application in schistosomiasis control.

Schistosomiasis, a group of parasitic diseases caused by Schistosoma parasites, is associated with water resources development and affects more than 200 million people in 76 countries. Depending on the species of parasite involved, disease of the liver, spleen, gastrointestinal or urinary tract, or kidneys may result. A computer-assisted teaching package has been developed by WHO for use in the training of public health workers involved in schistosomiasis control. The package consists of the software, ZOOM, and a schistosomiasis information file, Dr Schisto, and uses hypermedia technology to link pictures and text. ZOOM runs on the IBM-PC and IBM-compatible computers, is user-friendly, requires a minimal hardware configuration, and can interact with the user in English, French, Spanish or Portuguese. The information files for ZOOM can be created or modified by the instructor using a word processor, and thus can be designed to suit the need of students. No programming knowledge is required to create the stacks.

PIP: In 1989, staff at WHO headquarters in Geneva, Switzerland developed teaching software that can be used on IBM-PC and IBM-compatible computers to train public health workers in schistosomiasis. They tested in several schools of public health. They then improve it by incorporating a schistosomiasis information file (stack) in ASCII file format and a routine to organize and present data. The program allows the addition of other stacks without abandoning the user interface and the instructor can change data in the stacks as needed. In fact, any text editor such as Word-Perfect can create a stack. This software teaching program (ZOOM) organizes and presents the information (Dr. Schisto). Dr. Schisto is divided into 8 chapters: introduction, epidemiology, parasitology, diagnostics, treatment, data analysis, primary health care, and global database. Users can command ZOOM to communicate in either English, French, Spanish, or Portuguese. Basic hardware requirements include MS-DOS, 8086 microprocessor, 512 Kbytes RAM, CGA or MGA screen, and 2 floppy disc drives. ZOOM can also configured itself to adapt to the hardware available. ZOOM and Dr. Schisto are public domain software and thus be copied and distributed to others. Each information stack has chapters each of which contains slides, subslides, text, graphics, and dBASE, Lotus or EpiInfo files. ZOOM has key words and an index file to access more information. It also can do user defined searches using Boolean logic. Since ZOOM can be used with any properly formatted data, it has the potential to become the standard for global information exchange and for computer assisted teaching purposes.

Control of morbidity due to Schistosoma haematobium on Pemba Island: egg excretion and hematuria as indicators of infection.

The variability of Schistosoma haematobium egg excretion using a quantitative syringe filtration technique and the variability of hematuria detected visually and by reagent strips were studied in a population of 520 subjects from the village of Pujini (Pemba Island, Zanzibar, Tanzania) for 6 consecutive days. A high degree of day-to-day variability of egg excretion within subjects was found both in the whole population and in the 5-19 year age group. Subjects with 1 urinary egg count of greater than or equal to 50 eggs/10 ml urine were not similarly classified in 36-61% of the other 5 examinations and 4-16% of their other examinations were negative. Gross hematuria had a specificity of almost 100%, when related to a positive filtration on any day, and was closely related to egg counts of greater than or equal to 50 eggs/10 ml urine. The finding of a strongly positive reaction for hematuria on a given single day was closely associated with the subject having a high egg count (greater than or equal to 50 eggs/10 ml urine) on at least one of the 6 days of the study. At the primary health care level, single highly positive semiquantitative values for hematuria were a more useful diagnostic indicator than a single egg count to select patients with heavy infections for selective population chemotherapy.

Parasitic diseases and urban development.

The distribution and epidemiology of parasitic diseases in both urban and periurban areas of endemic countries have been changing as development progresses. The following different scenarios involving Chagas disease, lymphatic filariasis, leishmaniasis and schistosomiasis are discussed: (1) infected persons entering nonendemic urban areas without vectors; (2) infected persons entering nonendemic urban areas with vectors; (3) infected persons entering endemic urban areas; (4) non-infected persons entering endemic urban areas; (5) urbanization or domestication of natural zoonotic foci; and (6) vectors entering nonendemic urban areas. Cultural and social habits from the rural areas, such as type of house construction and domestic water usage, are adopted by migrants to urban areas and increase the risk of disease transmission which adversely affects employment in urban populations. As the urban health services must deal with the rise in parasitic diseases, appropriate control strategies for the urban setting must be developed and implemented.

Metrifonate in the control of urinary schistosomiasis in Zanzibar.

Selective population chemotherapy using three doses of metrifonate (7.5 mg/kg body weight each time) at two-week intervals was assessed in an entire community in Kinyasini district in Zanzibar, United Republic of Tanzania. The objectives of the study were to (1) reduce the prevalence of heavy infections (defined as greater than or equal to 50 S. haematobium eggs per 10 ml of urine) by 75% in two years, and (2) reduce the overall prevalence of infection by 50% in two years. A total of 4113 people were examined at least once during the two-year period. In the initial survey the highest proportion of infected individuals was in the 10-14-year age group, and in all subsequent surveys in the 5-9-year age group. The age group with the highest proportion of heavily infected individuals was 5-9 years for all surveys. The overall reduction of prevalence of infection from survey 1 to survey 4 was 52.9% and the prevalence of heavy infection was reduced by 62.2%. The conversion rates (negative to positive in two consecutive surveys) were highest in the longest interval of 12 months and the rates of reversion (positive to negative in two consecutive surveys, without a history of treatment) were highest in the shortest interval of 4 months. Some statistically significant relationships were observed between the number of doses and the egg reduction rates. However, for the egg-negative rates, no statistically significant relationship was observed. In the 4-month interval a 67.6% egg-negative rate was observed among those who took at least one dose; with the 12-month interval a 48.3% egg-negative rate was observed. Thus, selective population chemotherapy with metrifonate was shown to reduce the prevalence and intensity of infection due to S. haematobium over a 24-month period.