The relationship between morbidity and intensity of Schistosoma japonicum infection of a community in Jiangxi Province, China.

Seven hundred and eighty-five individuals from an area endemic for Schistosoma japonicum had parasitological and physical examinations done. A morbidity questionnaire was also administered to each participant. Among those with S. japonicum infection, there was a significant increase in diarrhea, blood in the stool and weakness during the previous two weeks. The severity of the disease appears to be related to the history of schistosomiasis japonicum and these results give further justification for treatment of the infected individuals and those severe morbidity groups in community based chemotherapy programs designed to reduce morbidity in endemic areas.

Economic development and tropical disease.

Development stands for an improved quality of life through gains in health, education, living standards, and higher income. Development is based on economic growth. Although all indicators of development: GDP per capita, average life expectancy at birth, and per capita income have been rising in almost all countries, including the "developing" countries over the past decades, economic growth did not lead to the expected disappearance of infectious diseases. Economic growth is associated with severe degradation of the natural world. Though economic growth is essential for development, it is a highly imperfect proxy for it. The people who suffer from the adverse effects of economic growth are often different from those who benefit from it. Economic development shows two faces with regard to tropical diseases: it is essential for their prevention and cure and it contributes to their transmission and severity through its impact on the environment. The pivotal point is poverty. If economic growth leads to improved education and social organization, even adverse effects can be mastered by the community.

Risk factors of HIV-1 infection among female prostitutes in Khon Kaen, Northeast Thailand.

HIV infection has increased to epidemic proportions in Thailand since 1987. There have been separate epidemics among population groups at high risk of infection and significant increases in different localities. The northeast region of Thailand has been affected by the epidemic since early 1989. The purpose of this study was to identify factors associated with HIV transmission among prostitutes during an early phase of the epidemic in the regional center of Khon Kaen. Three hundred and fifty-six prostitutes known to work in the urban area of Khon Kaen (Ampur Muang) in November 1990 were included in the study. Prostitutes were divided into two groups according to the type of place where they worked: direct prostitutes (in brothels, n = 217) and indirect prostitutes (in massage parlors, n = 139). The prevalence of HIV infection was found to be 12% among direct prostitutes and 2% among indirect prostitutes. Four variables were significantly associated with HIV infection after adjusting for confounders by logistic regression analysis: previous work in an area of high HIV prevalence, working in Khon Kaen less than one month, a low price charged for sex and using injectable contraceptives. Follow-up investigations are currently being carried out to explore in detail the association between the use of injectable contraceptives and HIV infection.

PIP: HIV infection has increased to epidemic proportions in Thailand since 1987. There have been separate epidemics among population groups at high risk of infection and significant increases in different localities. The northeast region of Thailand has been affected by the epidemic since early 1989. The purpose of this study was to identify factors associated with HIV transmission among prostitutes during an early phase of the epidemic in the regional center of Khon Kaen. 356 prostitutes known to work in the urban area of Khon Kaen (Ampur Muang) in November 1990 were included in the study. Prostitutes were divided into two groups according to the type of place where they worked: direct prostitutes (in brothels, n = 217) and indirect prostitutes (in massage parlors, n = 139). The prevalence of HIV infection was found to be 12% among direct prostitutes and 2% among indirect prostitutes. Four variables were significantly associated with HIV infection after adjusting for confounders by logistic regression analysis: previous work in an area of high HIV prevalence; working in Khon Kaen less than one month; a low price charged for sex; and using injectable contraceptives. Follow-up investigations are currently being carried out to explore in detail the association between the use of injectable contraceptives and HIV infection. (author's)

The National Schistosomiasis Control Programme in Mali, objectives, organization, results.

Schistosomiasis control started regionally, in the Bandiagara district, and as a component of a dam-building project in 1978. In 1982 a national programme was created. Control was divided into three phases: Preparation, intervention and maintenance. Districts qualifyed for schistosomiasis control activities, when the prevalence for either Schistosoma haematobium or Schistosoma mansoni exceeded 20% and/or the prevalence of persons with intensive infections for either parasite exceeded 5%. Intensive infection was defined as the excretion of more than 50 eggs per 10 ml of urine or the excretion of more than 100 eggs per one gram of stool. Preparation consisted of sample surveys to identify districts that needed to be included in control operations and the training of local health personnel. Interventions were primarily mass chemotherapy, using a single dose of praziquantel (40 mg/kg), sanitation and health education. The application was still being investigated for its cost benefit. Maintenance was to be achieved through the treatment of cases at fixed centres of the basic health services. Until 1987, control activities were carried out almost entirely through a central team based in the Institut National de Recherche en Santé Publique at Bamako in a vertical fashion. The full integration into the basic health services was retarded due to the drought and famine of the years 1983 to 1985 and other factors. The programme had been active in 136 villages located in the district of Bandiagara, the Office du Niger irrigation area, the Haute Vallée Baguineda irrigation area and the Sélingué dam zone.(ABSTRACT TRUNCATED AT 250 WORDS)

An evaluation of sampling methods within communities and the validity of parasitological examination techniques in the field.

In order to enable the assessment of schistosomiasis control, it has to be monitored. The methods and techniques employed for monitoring have to be validated in turn. In the Malian National Schistosomiasis Control Programme, only samples of the village population are examined. For practical and economic reasons, the sampling procedure is not free of bias from self-selection. When rates of samples are compared with results of examining the whole population no significant difference between the rates was found. Infection rates were precise to about +/- 5%. The sensitivity and specificity of laboratory technicians put to the task of identifying and counting the eggs of Schistosoma haematobium or S. mansoni in urine or stool samples differed considerably. The lowest scores were obtained by a laboratory technician from a district health centre who accompanied the central control team for a month. The predictive values of samples read positive dropped significantly below a general prevalence of 20%. The technician from the district centre would read samples falsely positive in more than 70%. However, the same person would read only 10% of slides falsely negative, once prevalence has dropped below the threshold of 20%, when maintenance depends on the performance of basic health services. The amount of stool used for a Kato-Katz preparation is only a 25th of one gram. The distinction between light and intensive infections with S. mansoni is therefore based on counting 1 to 3 or 4 or more eggs in a preparation. In a poisson distribution with mean 1, the difference between 1 and 4 is not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Experiences with mass chemotherapy in the control of schistosomiasis in Mali.

Mass chemotherapy using praziquantel in a single dose of 40 mg/kg was the main strategy of schistosomiasis control in Mali during the intervention phase. Treatment was applied either indiscriminately to all inhabitants over the age of two years of a given village or as a case treatment to those found infected during a previous parasitological examination. In one study area, only children aged 5 to 15 were treated if they had been found infected. According to the variables: type of treatment, parasite species, interval between intervention and follow-up survey, baseline prevalence, and ecological environment, 13 groups of villages were formed, comprising a minimum of five settlements and/or 600 inhabitants. The highest reductions of general or intensive infections were found when blanket mass treatment had been used in Schistosoma haematobium and if the follow-up was after one year. A significant reduction of S. haematobium prevalence was seen even three years after age specific case- or blanket treatment in non-specific savanna villages. Control was least successful with S. mansoni infections in irrigated areas.

The costs of schistosomiasis control in a Sahelian country.

The cost of schistosomiasis control in Mali was calculated on the assumption that the programme is fully nationalized and organized using the experience gained during the past seven years. In order to expand the model and to extrapolate from actual cost that arose, activities have been standardized into preparatory, baseline and follow-up sample surveys for monitoring purposes and into blanket and case mass chemotherapy for interventions. Health education is contained in them as a component, sanitation is seen as a standard item linked at a fixed cost to the duration of the intervention phase. These activities were divided into months of action and their unit cost was calculated on the basis of requirements of field allowances, transport, drugs, expendable materials, and equipment. Fixed operational costs were calculated on a yearly basis for salaries, data processing and administrative overheads. Using these unit costs, and on the basis of present knowledge of the prevalence, epidemiology and efficiency of control, the need and quantity of activities and the probable duration of a programme to achieve the goals set in the national health plan were estimated. If a population of 180,000 persons in about 300 villages is to be included in a programme that has as target to diminish the prevalence of both, Schistosoma haematobium and S. mansoni to less than 20% and that plans to diminish the prevalence of intensive infections of both parasites to less than 5%, a total amount of DM 6.9 to 7.5 million over a period of seven to nine years are required.(ABSTRACT TRUNCATED AT 250 WORDS)

The distribution and spread of schistosomiasis in relation to water resources development in Mali.

Schistosomiasis prevalence is known to be high in water resources development projects. Data from 225 villages and 34,434 persons were used to compare areas with irrigation in agricultural development projects, villages in the vicinity of small dams, settlements around a large artificial lake, communities along the Niger river and places in savanna areas without any irrigation programmes. For ten villages the prevalence rates before and after the creation of the large lake were analysed. In irrigated areas the risk of schistosomiasis infection was found to be six times higher than in savanna villages. Even in the vicinity of natural bodies of water the prevalence of infection was three times less than in agricultural development projects employing irrigation. A pre-valence of intense infections above 5%, indicating that schistosomiasis requires specialized interventions was observed only in areas with irrigation. Therefore schistosomiasis may be considered a man-made health problem in rural Mali although the infection is endemic in the whole country.

Cost and effectiveness of different approaches to schistosomiasis control in Africa.

In order to analyze the cost-effectiveness of selected mass-chemotherapy, a model is used to compare the treatment of urinary schistosomiasis with metrifonate (3 dose regimen, fortnightly intervals) and praziquantel (one dose regimen). The model was applied to two situations. Setting I, based on experiences in the Peoples Republic of the Congo, assumes that the average distance between the project base and the area of intervention is 80 km, the other, setting II, based on the situation in Mali, assumes an average distance of 250 km. The aim of the project is defined as the reduction of a prevalence of 50% to less than 5% in the absence of reinfection. Using metrifonate, the cost per person rendered negative is calculated at DM 12.57 for the Congo and at DM 32.52 for Mali. Prevalence will be 4.2% after intervention. Using praziquantel, the costs are DM 8.36 and 11.47, respectively, and the prevalence reached at the end of the intervention will be 1.1%. The cost difference is mainly due to the high operational cost incurred by the 3 dose regimen. Once low prevalence levels are reached, operational cost further outweigh drug expenses.

The prevalence of onchocerciasis in Togo.

From largely unpublished sources the results of surveys on onchocerciasis have been compiled for 164 villages in 17 of the 19 counties of Togo. 34449 persons i.e. 1.8% of the total population were seen. A map based on these data shows the distribution of the disease in Togo.

A histological investigation of skin lesions in onchocerciasis patients from Southern Togo.

Specimens from unselected populations in an area of hyperendemic onchocerciasis were used to describe and quantify histological changes in the upper layers of the dermis and the findings were compared with the macroscopical lesions observed. 553 persons, the inhabitants of two villages in Southern Togo, were examined. 502 biopsies were processed histologically. Onchocerciasis prevalence was over 75% and macroscopical skin lesions were evident in 30--40% of the population examined. Histological changes typical for the infection existed in the dermis in 68.5%. A cellular infiltration was seen in 49%, changes in the elastic or collagenous fibrils in 28.9% of the specimen. The observations are described in detail. Signs of inflammatory as well as primary degenerative changes were seen in biopsies from all age-groups. When microscopic and macroscopic findings are compared, it can be noticed that atrophy may start at an early age without preceeding dermatitis and that inflammatory reactions may occur at all ages. After submersion in saline for 24 hours not all microfilariae had emerged from the skin snips as evidenced by the histological examination. In 12.1% of those that otherwise would have been diagnosed as negative, microfilariae were identified in the sections.

A standardization of microfilarial densities for epidemiological comparisons in periodic bancroftian filariasis.

Microfilarial density in the peripheral blood changes with time. The average concentration in a population can only be calculated if the influence of circadian periodicity is eliminated from individual measurements. A transformation of the harmonic wave formula, describing the time dependent changes in density allows to calculate the number of microfilariae at the peak of the curve from the number observed at the time of examination. The equation was tested for strains of Wuchereria bancrofti from Liberia.

Epidemiological investigations of Bancroftian filariasis in the coastal zone Liberia.

A survey in 5 study areas along the Liberian coast was conducted to gain information on the prevalence and importance of bancroftian filariasis. The examination of 2675 persons revealed prevalence rates between 2% and 37%. The median microfilarial densities (MfD50) ranged from 5 to 24 microfilariae in 20 mm3 capillary blood taken between 20.30 hours and midnight. Catalytic curves fitted to age-specific infection rates were used to estimate incidence (1% to 3%) and recovery rates. It was extrapolated from the survey results that in a population of 71,0000 there are 16,0000 to 20,0000 infected with Wuchereria bancrofti. An estimated 2500 to 40000 men suffering from hydroceles and 3700 to 40000 elephantiasis patients demonstrate that bancroftian filariasis has to be regarded a health problem in rural coastal Liberia.

The microfilarial load in the anterior segment of the eye. A parameter of intensity of onchocerciasis.

The presence of microfilariae of Onchocerca volvulus in the eye is associated with an increased risk of deterioration of existing eye lesions. An opthalmological and parasitological examination of 630 persons was carried out in a hyperendemic focus of onchocerciasis in northern Togo. The prevalence of microfilariae increased in the cornea as well as the anterior chamber up to the age of 40-50 years, then decreased. The prevalence of onchocercal punctate keratitis, on the other hand, showed a peak for the age group 10-20 years. In two-thirds of the cases microfilariae were present in the anterior chamber as well as in the cornea. The relative distribution of microfilariae between the anterior chamber and the cornea did not change with the development of severe anterior lesions but in cases with severe posterior lesions relatively more microfilariae were found in the anterior chamber than in the cornea. In all cases of severe ocular lesions the numbers of microfilariae both in the anterior chamber and in the cornea were increased. The average number of microfilariae in the eye can be used as a parameter to enumerate the severity of ocular onchocerciasis.