An assessment of rural women's knowledge, constraints and perceptions on cervical cancer screening: the case of two districts in Zimbabwe.

This paper gives a sociological and anthropological insight into the rural women's perceptions and understanding of cervical symptomatology, screening and cancer. Qualitative data was collected through in-depth interviews and focus group discussions with women and health personnel. Quantitative data was obtained through questionnaires administered to 356 women from Mutoko and Shurugwi districts. The study revealed that cervical cancer is a disease that is of concern among health practitioners and women. 95.78% of the interviewed women had never gone for screening and had little knowledge about the various aspects of the disease in terms of causes, prevention and treatment. The study made four recommendations: the need for national screening policy and programme to be put in place, health education to women about cervical cancer, use of VIA in low resource settings and sensitisation of women about the availability of screening facilities in the districts where programmes are in place.

Recent upturn in mortality in rural Zimbabwe: evidence for an early demographic impact of HIV-1 infection?

OBJECTIVES: To describe recent mortality trends in rural Zimbabwe and to assess the impact of HIV-1 infection. METHOD: Comparative, cross-sectional, retrospective, demographic survey with 1-year follow-up. Parallel HIV-1 surveillance. Comparison of results with 1992 national census and vital registration data and results from mathematical model-based population projections. SETTING AND PARTICIPANTS: Residents of 929 (745 revisited in 1995) households in two rural areas of Manicaland Province, Zimbabwe, with contrasting HIV-1 prevalence: Honde and Rusitu valleys. Subjects gave information on parental survival for 2320 resident children. Female residents aged 13-49 years (n = 1237) provided information on birth histories and child survival. Consenting women attending local antenatal clinics (n = 487) provided blood samples for HIV-1 screening and demographic information. MAIN OUTCOME MEASURES: HIV-1 prevalence in pregnant women; per capita death registration rates; incidence of parental death for children aged under 8 years; infant mortality and age-specific death probabilities. RESULTS: HIV-1 prevalence was high in each study area. Death registration and age-specific mortality have begun to rise. The largest increases were seen in the area of higher HIV-1 prevalence (Honde) and among younger adults, particularly men. Incidence of parental death was observed to be rising. Increases in registered deaths were concentrated among HIV-1-associated causes. CONCLUSIONS: The observed increases in mortality by age, sex and cause of death were consistent with those expected early in a severe HIV-1 epidemic, on the basis of mathematical model projections and observations elsewhere in Africa. Further rises in mortality, particularly among women and young children, and consequent increases in orphanhood, are to be expected in rural areas of Zimbabwe.

Heterogeneities in transmission rates and the epidemiology of schistosome infection.

Previous theoretical studies have suggested that heterogeneities in transmission rates can have significant effects on the epidemiology of parasite infections. However, the magnitude of these effects in practice remains uncertain because of the difficulty of quantifying such heterogeneities under natural conditions. In this paper we consider the effects of heterogeneous rates of contact with infective water bodies on the basic reproductive rate, R0, of human schistosomes. In particular, we examine the theoretical effects of differences in the distribution of contacts among individuals and among sites. We find that an individual's contribution to R0 depends not only on the net contact rate but also on how these contacts are distributed among sites--the contact pattern. Our analysis of field data suggests a substantial impact of heterogeneous contact rates on R0 in practice. Significant reductions in R0 may be possible if schistosomiasis control efforts are targeted at certain sites and, especially, certain individuals.

Contrasting cellular responses in Schistosoma haematobium infected and exposed individuals from areas of high and low transmission in Zimbabwe.

The study compared cytokine profiles of individuals from two areas with different transmission patterns for Schistosoma haematobium. One area was a high transmission (HT) while the other was a low transmission (LT) area for S. haematobium. Observations on cellular immune responses were made on stimulated peripheral blood mononuclear cells (PBMC), which were collected pre-treatment, then at 12 and 18 months post treatment. Stimulation was with schistosome worm and egg antigens and a mitogen, phaetohaemaglutinin (PHA). Observations were made on PBMC proliferation and the profiles of cytokine produced over a 5-day incubation period. The two distinct areas showed significant differences on both levels of proliferation and cytokine production for all the measured classes (IL-4, IL-5, IL-10 and IFN-gamma). PBMC from individuals from the LT area had high levels of proliferation but low cytokine production to both antigen stimulants while PBMC from individuals from the HT area showed low levels of proliferation but high cytokine production levels. Prior to treatment, individuals not excreting schistosome ova in the HT area had higher levels of proliferation to the stimulants, than the infected individuals. However, after treatment re-infected individuals showed high levels of proliferation. Before treatment, both infected and uninfected groups showed low and similar ratios, respectively, of IL-4:IFN-gamma, IL-5:IFN-gamma and IL-10:IFN-gamma, while IFN-gamma was high in the infected individuals. After treatment the non re-infected had higher levels of IL-4, IL-5 and IL-10, with the infected having high levels of IFN-gamma. Th1-like response dominated during infection with the Th2-like responses dominating post treatment and in uninfected individuals. The results indicated that the cytokine balance determines, in part, susceptibility or resistance to S. haematobium infection.

On the distribution of schistosome infections among host snails.

The distribution of Schistosoma haematobium infections in a population of Bulinus globosus snails collected from a field site in Zimbabwe is described. Cercariae of both sexes emerged from a proportion of patent infected snails, as was demonstrated by the detection of paired schistosomes in hamsters each exposed to cercariae from a single snail. These snails must have been infected by two or more miracidia. Analysis showed that the proportion of mixed-sex infections was higher than expected if infections were distributed at random among snails. An index of overdispersion was calculated. Overdispersion of infections results from heterogeneities in the exposure and/or susceptibility of snails to infection. The implications for the epidemiology and control of schistosomiasis haematobium are discussed.

Genetic structure and parasite compatibility of Bulinus globosus (Gastropoda: Planorbidae) from two areas of different endemicity of Schistosoma haematobium in Zimbabwe.

A comparative study of the genetic structure of 8 populations of B.globosus from 2 areas of different endemicity of Schistosoma haematobium was done. Five populations were from Chiweshe (high endemicity) and three were from Plumtree (low endemicity). Genetic structure, as determined by allozyme genetics, revealed high levels of genetic variability in Chiweshe populations (Ho = 0.12-0.26) and low levels in Plumtree (Ho = 0.06-0.12). Populations from Chiweshe were genetically heterogeneous whereas in Plumtree the populations were uniform. There were significant deviations from Hardy-Weinberg proportions at different loci in Chiweshe populations. The observed excess of homozygotes was probably caused by partial selfing. The compatibility studies showed variation between allopatric and sympatric combinations of snails and parasites, and the Plumtree parasite had a significant influence on the compatibility parameters. This strain had a positive correlation (P < 0.01) of its infection rate with allele frequency of Est-2(100) and a negative correlation (P < 0.05) with allele Idh100.

Age-dependency in predisposition to hookworm infection in the Burma valley area of Zimbabwe.

We examined hookworm re-infection intensities (measured as faecal egg count by the Kato technique) following anthelmintic treatment of farm workers resident on 15 large-scale commercial farms in Zimbabwe. All individuals examined were treated with albendazole (400 mg). Hookworm reinfection intensities of individuals examined, treated and reexamined were compared with the intensities of infection before treatment. Adults had higher than average infection intensities both before and after reinfection. Predisposition to hookworm infection was marked in adults, and absent from younger, less heavily infected hosts. The observations suggest that acquired immunity is unlikely to be an important determinant of hookworm infection and that behaviour may play a major role in determining the observed infection patterns in this community.

The epidemiology and control of hookworm infection in the Burma Valley area of Zimbabwe.

An integrated hookworm control programme, involving mass chemotherapy and improvements in public health, was conducted in the Burma Valley and Vumba areas of Zimbabwe between 1985 and 1990. Three sequential annual mass chemotherapy programmes were implemented. Infection status was monitored annually throughout. Initial observations indicated asymptotic age prevalence and intensity profiles, with peak infection levels in adults. Mass chemotherapy was shown to have immediate and medium term benefits for community health. Reinfection was slow to develop, and average intensity had not returned to pre-intervention levels 39 months after the cessation of chemotherapy. The results support the existence of age-dependency in reinfection. Despite a marked increase in the number of sanitation units, no relationship was found between latrine availability and reinfection intensity on individual farms. This result is consistent with observations that the effect of sanitation is slow to develop, and indicates that repeated anthelmintic intervention should be maintained until sanitation has an impact on transmission.

Field evaluation of controlled release copper glass as a molluscicide in snail control.

Limited field evaluation of a new molluscicide, copper controlled release glass (CRG), was carried out in 4 human water contact sites in shallow and slow flowing streams in the highveld region of Zimbabwe during 1984 to 1986. The results indicate that the copper CRG has great potential as an inexpensive snail control agent to reduce schistosomiasis transmission. There was a marked reduction in snail numbers in the treated sites after application of 2 forms of the copper molluscicide; a "fast" CRG with approximately 24-h solution time in water and a "slow" CRG with about 1-year solution time. Snail numbers remained depressed during the observation period while frogs and fish were not affected. Fluctuations in snail numbers in the untreated sites showed no clear pattern, being erratic and unpredictable and probably attributable to seasonal effects. Problems of the correct amounts of molluscicide to apply to a site are to an extent overcome by knowledge of the copper binding capacity of the mud substrate. The mud sediment can be saturated by the "fast" release copper glass to achieve a snail killing concentration in the water which can be sustained by the "slow" release glass. It appears that the main difficulty in maintaining desirable copper levels in the water is flow, which causes rapid removal of copper from the treated waterbody. Thus, under field conditions on the highveld region of Zimbabwe, the CRG molluscicide is likely to be effective only during the stable conditions of the dry season which is, however, the main transmission period.

The epidemiology and population biology of Necator americanus infection in a rural community in Zimbabwe.

Baseline data from an epidemiological study of hookworm infection in a rural community in Zimbabwe are presented. The infection status of an age-stratified sample of the community was assessed using anthelmintic expulsion techniques. Necator americanus was the only helminth parasite found to be present. The age-prevalence and intensity profiles rose asymptotically to an adult prevalence of about 80% and adult mean burden of 7.7 worms per host. The overall mean burden was 4.8 worms per host. The frequency distribution of N. americanus was overdispersed and well described by the negative binomial distribution with a value for the aggregation parameter, k, of 0.346. Separate estimates of k were lower in males and older hosts. The distribution patterns were difficult to reconcile with any simple process of age-dependent acquisition of an effective immune response. A significant negative correlation was recorded between per caput fecundity and worm burden, providing evidence for a density-dependent regulation of female worm fecundity. The basic reproductive rate (R0 congruent to 2) was found to be similar to estimates from other geographical areas.

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.

Control of schistosomiasis transmission in newly established smallholder irrigation schemes.

The extent to which schistosomiasis can be controlled through careful design of the irrigation works, the operation schedule, the location of villages and the provision of safe water supplies and sanitation in smallholder irrigation schemes at Mushandike in south-east Zimbabwe is reported. The schemes provide land for 400 peasant families who are monitored for schistosomiasis soon after resettlement. Between April 1986 and August 1987 there was a marked reduction in overall prevalence following treatment. For Schistosoma haematobium, the reductions in 2 schemes were 53% and 82% and for S. mansoni, 82% and 100%, in spite of transmission in settlements upstream from the schemes. In contrast, in a nearby irrigated farm where no control measures were introduced, S. haematobium prevalence declined by only 31% while that for S. mansoni increased by 22% a year following treatment. These results are supported and strengthened by measurements of snail population sizes and their infection rates, cercarial densities in the water and incidence data for the human population, and suggest that the engineering and environmental control measures introduced are significant means of controlling transmission in smallholder irrigation schemes with the lowest recurrent costs.

Population dynamics model for Bulinus globosus, intermediate host for Schistosoma haematobium, in river habitats.

A mathematical model is developed that describes the population dynamics of the freshwater snail Bulinus globosus, an intermediate host of Schistosoma haematobium. The model is developed from field data recording abundance changes, recruitment rates, and mortality rates for adult snails in river habitats in Zimbabwe. Rate of recruitment into the adult population is dependent on temperature, incorporating a time lag to allow for growth to adult size. Mortality rate is also a function of temperature. A temperature-dependent model provides a useful description of changes in abundance during the dry season. Long-term population fluctuations are greatly affected by spates (flooding) associated with heavy rainfall. An estimate is made of the frequency and effects of spates. A simulation model that allows variable annual rainfall predicts fluctuations in snail abundance over two orders of magnitude over timescales of ten or more years. The role of density-dependent factors and the long-term persistence of the population are discussed. B. globosus population dynamics can be described as 'density vague'.

Seasonal patterns in the transmission of Schistosoma haematobium, S. mattheei and S. mansoni in the highveld region of Zimbabwe.

The pattern of fluctuation in the population size of Bulinus globosus and Biomphalaria pfeifferi, in their infection rates with Schistosoma haematobium/S. mattheei and S. mansoni, respectively, and in the cercarial population size as monitored using hamster immersions, was elucidated in streams in the temperate highveld region of Zimbabwe over a 27-month period during 1982-1984. The results revealed that transmission of S. mansoni was erratic and unpredictable without a clearcut seasonal transmission pattern. In contrast, transmission of S. haematobium and S. mattheei exhibited a marked seasonal pattern, being most intensive during the hot, dry season (September-November) and markedly reduced during the cold, dry season (June-August). During the rainy (December-February) and warm, post-rainy (March-May) seasons transmission was moderate and variable, but occasionally intensive. The results also showed that rodent immersion is to be preferred to measurements of snail population size and snail infection rate in elucidating seasonality of transmission of schistosomiasis.

The use of Phytolacca dodecandra berries in the control of trematode-transmitting snails in Zimbabwe.

Phytolacca dodecandra, a plant with berries of a known molluscicidal potency, was cultivated in Chiweshe. Studies on the snail population density of Bulinus globosus and Lymnaea natalensis as well as schistosome infection rates in the former were carried out in two streams, in one of which a water extract of P. dodecandra berries was applied in late April and May 1987. Snail sampling was carried out twice a month from April 1986 to April 1988, that is for 12 months prior to and after the mollusciciding exercise. B. globosus snails obtained from both streams were examined for infection by cercarial shedding before they were returned to their sites of collection. The 8-h water extract of P. dodecandra was applied to human watercontact points. The two applications were aimed at achieving a concentration of 50 mg/l. No snails were recovered from the experimental sites for a period of 7 months after the mollusciciding exercise. Snails were recovered in the treated sites only after the onset of the rainy season.

Evaluation of the reagent strip test for haematuria in the control of Schistosoma haematobium infection in schoolchildren.

Several recent reports have indicated the potential of the reagent strip test for haematuria in the diagnosis of Schistosoma haematobium infection. Approximately 15,000 schoolchildren from a population of 40,000 people were examined for reagent strip microhaematuria on three occasions between 1986 and 1987 and treated with praziquantel 40 mg/kg if positive. The reagent strip was evaluated against a single filtration of 10 ml urine for S. haematobium eggs. Initially 65.9% of children were treated followed by 37.5% at the second examination 6 months later and 44.5% at the third examination a further 12 months later. Reagent strip sensitivity was shown to be related to the intensity of infection. The reagent strip specificity improved significantly with successive treatments indicating that haematuria was more sensitive than parasitology for light infections. The amount of S. haematobium reinfection was highest in the 7-9 year olds decreasing to the 16-20 year age group which suggested an impact of protective immunity. It was concluded that microhaematuria is a valuable indicator for the diagnosis of S. haematobium in national control programmes and can be substituted for parasitological examination with advantage but sensitivity and specificity should continue to be evaluated throughout the programme.

Optimization of the Magnetic Bead Antigen Capture Enzyme Immuno Assay for the detection of circulating anodic antigens in mixed Schistosoma infections.

In the present study, simplification and adaptation of the Magnetic Bead Antigen Capture Enzyme Immuno Assay (MBAC-EIA) technique for detection of circulating anodic antigens (CAA) under field conditions was achieved. It was shown that the assay could be performed successfully within the broad temperature range of 18-37 degrees C. The slightly lower sensitivity observed at low temperatures could be adjusted for by prolonging the incubation period. Shaking the plate by hand was as good as automatic mechanical shaking, aspiration of the supernatant before the addition of conjugate was not necessary, and the use of whole blood and serum offered similar assay sensitivity. Furthermore incubation times could be considerably shortened without loss of sensitivity. A major advantage of the MBAC-EIA was that the beads, after elution of bound components, were found to be reusable. The study also showed that the sensitivity of the MBAC-EIA technique in diagnosis of schistosomiasis in a Zimbabwean community endemic for both urinary and intestinal schistosomiasis, was 94%.

Community water-contact patterns and the transmission of Schistosoma haematobium in the highveld region of Zimbabwe.

The patterns of community water-contact, their relationships to Schistosoma haematobium infection in the human population and also in Bulinus globosus, snail host for S. haematobium and S. mattheei were carried out at 12 human water contact sites located in stream habitats in the temperate highveld region of Zimbabwe over a 27-month period during 1982-1984. It was shown that water contact was markedly heterogeneous with sex, age, type of activity and village location being the major variables affecting water-contact patterns. This heterogeneity in contact appears to be related to variations in levels of infection with S. haematobium among residents of the villages and by sex but in adults high water-contact was not associated with increased levels of infection and this discrepancy is attributed to the influence of acquired immunity in adults. An association was found between total body exposure indices and prevalence of S. haematobium in B. globosus in the cool dry and hot dry period of the year indicating that the level of input of schistosome eggs into water play an important role in determining snail infection rates, although the absence of clearcut relationships between the two parameters in the rainy and post-rainy periods suggest that other factors may be involved.

The rational use of antischistosomal drugs in schistosomiasis control.

The paper examines the available antischistosomal drugs in Zimbabwe and the use of population-based chemotherapy as an effective strategy of morbidity reduction in schistosomiasis control. The problems of poor drug efficacy and side-effects that were associated with earlier antischistosomal drugs have largely been overcome with the advent of recent, safe and effective oral drugs. The main constraints of population-based chemotherapy are the costs of drug procurement, transport and the logistics of delivery. In highly endemic areas, screening for infection may not be necessary and following pilot surveys mass chemotherapy can be carried out. Nevertheless, anecdotal and unverified reports suggest that mass chemotherapy may result in lightly infected individuals losing their residual immunity and risk heavy reinfection. To lower costs of the drugs and reduce organizational problems of delivery it may be preferable to target treatment at high risk groups. These groups include certain age classes with peak prevalence and intensity of infection and those predisposed to get heavy infections. Treatment prevents the development of overt disease in these high risk groups and also significantly reduces contamination and consequently transmission. However, chemotherapy only results in temporary relief and its impact requires to be sustained by parallel and long-lasting interventions that include improved sanitation, better water supplies and health education. Suggestions are made on how to train and utilize community and public health workers for such control programmes.

Knowledge, attitudes and practices among rural communities in Zimbabwe in relation to Phytolacca dodecandra--a plant molluscicide.

Questionnaires about schistosomiasis and Phytolacca dodecandra, a plant molluscicide with potential to control schistosomiasis transmitting snails, were administered to 271 women and 168 men in two communal areas where the plant grows naturally, and in a further two areas where no records of the plant exist. 78.9% of the respondents thought that schistosomiasis was a dangerous disease with blood in urine being the most recognised symptom. 11.8% said that snails were involved in the transmission of the disease, although their role in sustaining the life cycle of the schistosome parasite was not understood. Knowledge about P. dodecandra was restricted to people resident in areas where the plant grows naturally and to immigrants from areas where it is known to grow. The most common use of the plant was as a floor polish. Knowledge of uses of the plant were found to be related to the sex of the respondents. Seventy-seven percent of the people interviewed were prepared to cultivate the plant for self-help schistosomiasis control programmes. Of the 23% that were not willing to cultivate P. dodecandra, 47.7% cited scarcity of land as the main obstacle. Other reasons were lack of knowledge about the plant (21%), lack of confidence in the success of such self-help programmes (11.2%) and indifference due to old age (20%).