Showing papers on "Schistosoma haematobium published in 1990"
TL;DR: 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.
Abstract: 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.
131 citations
TL;DR: The status of schistosomiasis in Cameroon was examined in a nationwide survey of 5th grade schoolchildren, and the distribution of Schistosoma haematobium and S. mansoni was highly focal and restricted to the equatorial forest and were small with low prevalences and intensities.
Abstract: The status of schistosomiasis in Cameroon was examined in a nationwide survey of 5th grade schoolchildren. Five hundred twelve schools were surveyed; 19,524 urine and 22,166 stool samples were examined. The 3 northern provinces, which comprised 29% of the population, had 87% of all urinary and 82% of all intestinal cases. These provinces have a low seasonal rainfall. The presence of temporary bodies of water and of molluscan intermediate hosts adapted to this environment permits intense transmission of schistosomiasis haematobium and mansoni. In the rest of the country, the distribution of Schistosoma haematobium and S. mansoni was highly focal. S. intercalatum endemic areas were restricted to the equatorial forest and were small with low prevalences and intensities.
91 citations
TL;DR: Treatment with either metrifonate or praziquantel may allow improved physical fitness and appetite in areas where S. haematobium and protein-energy malnutrition are highly prevalent.
Abstract: We studied physical fitness, as determined by the Harvard Step Test (HST), and appetite, as measured by the consumption of a morning snack (maize meal porridge), in primary school boys infected with Schistosoma haematobium (100% baseline prevalence) and hookworm (94-100% prevalence) who received a single dose of metrifonate (MT, 10 mg/kg body weight) or praziquantel (PR, 40 mg/kg body weight), or a placebo (PL). Five weeks after treatment, HST scores and porridge intake increased significantly in the MT and PR groups, but the PL group did not change. At the second examination, the MT group showed a significant decrease in S. haematobium egg counts (mean = 180 vs. 14 eggs/10 ml adj, P less than 0.0002, 82% egg reduction in arithmetic means) as did the PR group (mean = 198 vs. 0.1 eggs/10 ml adj, P less than 0.0002, 99.9% reduction); the egg counts in the PL group did not change. The MT group also exhibited a significant decrease in hookworm egg counts (mean = 1,550 vs. 75 eggs per gram feces [epg], P less than 0.0005, 80% reduction). Treatment with either drug may allow improved physical fitness and appetite in areas where S. haematobium and protein-energy malnutrition are highly prevalent.
71 citations
Journal Article•
TL;DR: It is revealed that cross-sectional ultrasound surveys can be used to quickly assess subsamples of populations in areas of different endemicity, in order to make decisions about sampling strategies in control programmes.
Abstract: Among the indicators of schistosomiasis morbidity currently used in control programmes, ultrasound has been found to be a safe, non-invasive and efficient technique for detecting schistosomiasis-related lesions and for assessing the effect of treatment on their resolution. Three case-studies from East Africa, in areas of different endemicity for Schistosoma haematobium, using ultrasound are described and their results related to indirect measurements of the disease (e.g., haematuria, egg counts). This review reveals that cross-sectional ultrasound surveys can be used to quickly assess subsamples of populations in areas of different endemicity, in order to make decisions about sampling strategies in control programmes. The association between the intensity of infection and urinary tract abnormalities is reviewed and evaluated. One case study provides information on the resolution of S. haematobium-related uropathy after treatment; this information is crucial in order to maintain low levels of morbidity in a community. The role of ultrasound is further discussed, particularly as a tool to complement and validate indirect morbidity control measurements. The validation of such indirect measurements for use as a basis for public health decisions is important because they can be carried out by existing health care services in many areas.
64 citations
TL;DR: Data support a casual relationship between S. haematobium infection and squamous cell carcinoma of the bladder in Zimbabwe.
Abstract: Bladder cancer is common in Zimbabwe, possibly due to the high prevalence of Schistosoma haematobium infection in some areas. We undertook a correlational study based on retrospective medical record review to see whether the number of bladder cancers could be related to geographical region and prevalence of S. haematobium infection. We also determined patient demographic characteristics and tumour histology. Of 483 patients identified (1984-1987), 69% with available histology had squamous cell carcinomas. The remainder had transitional cell carcinomas. Patients with squamous cell carcinoma were younger than patients with transitional cell carcinomas (50% vs 20% under 50 years old, P less than 0.05) and had a sex ratio of one. There was a positive geographical relationship between S. haematobium prevalence and the incidence of squamous cell carcinoma of the bladder: provinces with high prevalence of S. haematobium had more bladder cancer cases with a predominance of squamous cell carcinoma (r = 0.87, P less than 0.01). These data support a casual relationship between S. haematobium infection and squamous cell carcinoma of the bladder.
60 citations
TL;DR: 20 mg/kg of praziquantel was as effective with regard to cure rates and reversibility of morbidity as 40mg/kg, and six months after treatment, 90.4% and 88.0% parasitological cure rates were obtained.
Abstract: A study to assess the resolution of urinary tract morbidity due to Schistosoma haematobium was conducted on 2 cohorts of schoolchildren attending neighbouring schools in Kilombero District, southern Tanzania. Schoolchildren were screened for S. haematobium infection using the standard World Health Organization filtration technique and subsequently examined for urinary tract pathology using a portable 3·0 MHz sector scanner (Siemens Sonoline 1300). Treatment with praziquantel was given to all infected children. Children with observed urinary tract pathology received either 20 (n = 52) or 40 (n = 79) mg/kg body weight and were sonographically re-examined one, 2, 3 and 6 months following treatment. Geometric mean outputs of 21 and 19 eggs/ml of urine were detected in the 2 cohorts before treatment. Urinary tract pathology correlated positively with egg output (χ2, P = 0·02) and microhaematuria (P = 0·0001). Bladder (wall irregularities and polyps) and kidney (congestive changes) pathologies were found in 81% and 36%, respectively, of the group that received 20 mg/kg of praziquantel, and in 78% and 46% of the group that received 40 mg/kg. Six months after treatment, 90·4% and 88·0% parasitological cure rates were obtained using 20 or 40 mg praziquantel/kg body weight. The respective pathology clearances were 88% and 91%. 20 mg/kg of praziquantel was as effective with regard to cure rates and reversibility of morbidity as 40 mg/kg.
58 citations
TL;DR: It is concluded that the future maintenance control strategy in this project area may call for more frequent chemotherapy treatments in identified foci of high prevalence and intensity, with complementary focal mollusciciding and/or targeted treatment of schoolchildren, in order to prevent the serious consequences of infection.
Abstract: Continuing epidemiological evaluation of schistosomiasis intervention measures applied in Middle and Upper Egypt since 1985 indicate that a large measure of control of Schistosoma haematobium has been achieved in relation to both prevalence and intensity of the infection and incidence of new infections. Transmission control has, however, been inadequate in many areas, since numerous re-infections occurred in treated schoolchildren. Variable compliance rates in the chemotherapy delivery system were probably, in part, an important contributory factor, and shortcomings of the selective and/or focal mollusciciding strategy were also probably responsible for many new cases and re-infections. Chemotherapy delivery has now been improved following the introduction of single dose treatments with praziquantel and it is expected that there will be an increased demand for treatment following the introduction of a new information-education-communication campaign. In communities with geometric mean egg-output of less than 50 per 10 ml of urine, acceptable control of the potential for development of schistosomal disease can be expected. It is concluded, therefore, that the future maintenance control strategy in this project area may call for more frequent chemotherapy treatments in identified foci of high prevalence and intensity, with complementary focal mollusciciding and/or targeted treatment of schoolchildren, in order to prevent the serious consequences of infection. In 1988 the annual cost of schistosomiasis control measures per person throughout the project area (2 million irrigated feddans (c .800 000 hectares] containing 12 million people) was 0·5 Egyptian pounds (LE) (US$ 0·20), representing 5·2% of the annual expenditure per person in Egypt (LE 9·6) for all health services.
53 citations
TL;DR: It is clearly shown that temporary water bodies in the tropical zone are the principal foci of transmission of schistosomiasis in Cameroon, and these findings disagree with commonly held views aboutSchistosome transmission in Cameroon.
Abstract: A nationwide survey for snail hosts of human schistosomes was carried out in Cameroon between 1985 and 1988. In total, 668 sites at 432 locations were sampled. In the arid, northern half of the country (tropical climatic zone), where both intestinal and urinary schistosomiasis are hyperendemic, Biomphalaria pfeifferi was the only Schistosoma mansoni host and Bulinus globusus and B. senegalensis the most common S. haematobium hosts. In that region, these snails occurred almost exclusively in temporary bodies of water. Taking into account results from a companion study on the distribution of schistosomiasis in humans, our results clearly show that temporary water bodies in the tropical zone are the principal foci of transmission. These findings disagree with commonly held views about schistosome transmission in Cameroon. B. truncatus, a S. haematobium host, was also present in the tropical zone but was found principally in perennial habitats. Although some perennial habitats were important transmission sites, they represent only a small portion of the overall problem. B. truncatus is the principal S. haematobium host in the wetter southern half of the country where schistosomiasis haematobium is highly focal. Biom. camerunensis was far more common than Biom. pfeifferi in the South but did not occur where S. mansoni prevalence rates were high; thus it appears to be a poor host. B. forskalii, the sole host of S. intercalatum in Cameroon, occurs widely throughout the country; however, the schistosome is restricted to a small region in the South.
50 citations
TL;DR: Results indicated equivalent patient improvement in response to either regimen: prevalence of hematuria fell from 75% to 17% after either praziquantel or metrifonate therapy, and prevalence of proteinuria was significantly reduced after therapy.
Abstract: To determine the relative efficacy of metrifonate and praziquantel in controlling urinary tract morbidity due to Schistosoma haematobium infection, a random allocation treatment trial was performed among 1,813 school age S. haematobium-infected children from the Msambweni area of Coast Province, Kenya. Following baseline examination for infection, hematuria, proteinuria, and ultrasonographic urinary tract abnormalities, oral treatment with either metrifonate (10 mg/kg, repeated at 4 month intervals) or praziquantel (1 dose of 40 mg/kg) was given to infected subjects. Prevalence of morbidity was reassessed 12 months later for each treatment group. Results indicated equivalent patient improvement in response to either regimen: prevalence of hematuria fell from 75% to 17% after either praziquantel or metrifonate therapy. Similarly, prevalence of proteinuria was significantly reduced from 73% to 29% (metrifonate) or 27% (praziquantel) after therapy. Metrifonate and praziquantel caused similar reductions in bladder granulomata and bladder thickening; however, no reduction in hydronephrosis was noted with either drug. Analysis of outcomes in population subgroups defined by age, sex, pretreatment intensity of infection, or severity of pretreatment morbidity showed no consistent advantage for either drug. In this endemic area, both agents provide effective control of morbidity due to urinary schistosomiasis.
39 citations
TL;DR: 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.
33 citations
TL;DR: The results corroborate the genetic determinism of the cercarial emergence of schistosomes and suggest that significant differences between the hybrids and their parents in the times of cercarian emission may be of value in the epidemiological research and characterization of naturally occurring hybrids.
TL;DR: Results from this and similar studies indicate that the time of infection by a trematode in relation to reproductive maturity of the molluscan host is important in determining the subsequent effects on host growth and fecundity.
Abstract: Three species of bulinid snails were monitored to determine the effect of infection with 2 sympatric strains of Schistosoma haematobium on longevity, growth, and reproductive output, from the onset of cercarial production until death. Bulinus senegalensis was least affected by infection, with total fecundity reduced by less than 34%. Infected Bulinus truncatus showed an acceleration in growth accompanied by a 63% reduction in fecundity, although the majority of snails continued to oviposit at a low level. The longest-lived snails in this study, Bulinus globosus, showed decreased growth and survival when infected. In addition a significant proportion of infected individuals of this species failed to oviposit, and those that retained some reproductive capacity produced fewer embryos than controls. Total fecundity of B. globosus was reduced almost 90% by infection with S. haematobium, yet long-term monitoring of individuals showed that reproductive activity recovered when parasite productivity was low. Results from this and similar studies indicate that the time of infection by a trematode in relation to reproductive maturity of the molluscan host is important in determining the subsequent effects on host growth and fecundity.
TL;DR: The distribution of Schistosoma haematobium infections in a population of Bulinus globosus snails collected from a field site in Zimbabwe is described and the proportion of mixed-sex infections was higher than expected if infections were distributed at random among snails.
TL;DR: The quantitative relationship between water contact and Schistosoma haematobium infection was studied in a cohort of male school children aged 6-17 in El Ayaisha village, Upper Egypt, during a two-year study and the exposure index was used to identify the activities responsible for exposure to cercariae-infested water.
Abstract: The quantitative relationship between water contact and Schistosoma haematobium infection was studied in a cohort of male school children aged 6-17 in El Ayaisha village, Upper Egypt, during a two-year study. An exposure index (total body minutes, TBM) was used to identify the activities responsible for exposure to cercariae-infested water and to examine the relationship between water contact and infection. Results show that 65% of all contacts and 86% of all TBM were due to swimming in the Nile and canals and that swimming was the most important exposure and contamination activity. Using multivariate analysis, several sites, study periods, residence groups and mostly canal contacts were significantly correlated with egg-counts. Positive relationships could also be identified using egg-counts with water contact data from preceding study periods, indicating the influence of pre-existing infections, prepatency and seasonality of water contact and transmission. TBM were usually more significantly correlated with egg-counts than frequency and duration of contact. The relevance of the findings for control programmes and the use of school children and the exposure index for water contact studies are discussed.
Journal Article•
TL;DR: A case of cardiopulmonary bilharziasis is studied in a female, 21 years old, from Senegal, infested by Schistosoma haematobium, and with praziquantel, the patient was cured in 16 months.
Abstract: A case of cardiopulmonary bilharziasis is studied in a female, 21 years old, from Senegal, infested by Schistosoma haematobium. With praziquantel, the patient was cured in 16 months. The cardiopulmonary bilharziasis is more frequent on pathological examination than in clinical features. The diagnosis of cardiopulmonary bilharziasis is made by pulmonary biopsy which shows an occlusive angiitis with chronic inflammatory cells, and arteriolar medial hypertrophy. The prognosis is dependent upon development to schistosomal cor pulmonale and right ventricular failure. The newly developed drugs are effect in cardiopulmonary bilharziasis, in experimental studies.
TL;DR: The case illustrates a rare preventable cause of ectopic pregnancy in this population, and ova of Schistosoma haematobium were found in the submucosal and intramural parts of the tube.
TL;DR: Levels of circulating anodic antigen (CAA) in serum were investigated after differential treatment of 160 Sudanese patients with mixed Schistosoma haematobium and S. mansoni infections and clearing of CAA from the circulation seemed to take longer in patients treated with oxamniquine.
TL;DR: Le traitement par praziquantel doit remplacer l'habituelle excision chirurgicale d'apparence polypoide chez une fille de 9 ans.
Abstract: Lesion d'apparence polypoide chez une fille de 9 ans. Diagnostic au microscope optique simple. Le traitement par praziquantel doit remplacer l'habituelle excision chirurgicale
Journal Article•
TL;DR: It is suggested that morbidity due to Schistosoma haematobium infection can be reduced by annual treatment over several years in a highly endemic area without other associated interventions.
Abstract: A comparative study on the extent of urinary tract abnormalities detected by ultrasound was conducted in two villages in an irrigated area of Niger where the pretreatment prevalences were 64.3% and 58.8% respectively. Fewer bladder lesions (20% of abnormalities) and fewer renal lesions (6% of abnormalities) were observed after four consecutive years of follow-up and treatment with praziquantel in the study village as compared to the control village where 54% bladder abnormalities and 36% renal abnormalities were observed. This study suggests that morbidity due to Schistosoma haematobium infection can be reduced by annual treatment over several years in a highly endemic area without other associated interventions.
TL;DR: Enzyme electrophoresis indicated that all Schistosoma mattressheei eggs passed in the urine of humans derive from S. mattheei females in copula with S. haematobium males.
Abstract: Enzyme electrophoresis indicated that all Schistosoma mattheei eggs passed in the urine of humans derive from S. mattheei females in copula with S. haematobium males. It appears that S. mattheei males do not reach sexual maturity in man; however, S. haematobiumxS. mattheei males possibly do.
Journal Article•
TL;DR: The seasonality of infection of Bulinus (Ph.) globosus, the snail host of Schistosoma haematobium is reported and the pattern of snail infection was shown to vary with the type of habitats.
Abstract: The seasonality of infection of Bulinus (Ph.) globosus, the snail host of Schistosoma haematobium is reported. The pattern of snail infection was shown to vary with the type of habitats. The cercarial "transmission potential" was calculated based on the number of infected snails and the level of cercarial production. It is consequently assumed that the transmission pattern varies with season and habitat type. Dry season transmission potential was found to be high in running water habitats while low in stagnant water habitats. In the wet season, the reverse seems to be the case. The implication of these observations in the epidemiology of urinary schistosomiasis and in planning its control in the area is discussed.
TL;DR: High levels of total IgE already in the youngest age groups, together with low specific IgE response, indicates that mainly other antigens are involved in the IgE production, and it is suggested that repeated booster effects are needed for more potent response against these antigenic components.
Abstract: Antibody responses in schistosomiasis haematobium were studied in relation to age and infection intensity in Somalia. The area is highly endemic for Schistosoma haematobium but free of S. mansoni. Antibodies of the IgG class against particulate antigens of S. mansoni adult worms were investigated by immunofluorescence (gut and somatic associated antigens) and against soluble egg and adult worm antigens by ELISA. Total IgE levels were examined by Pharmacia IgE RIA, and specific IgE against soluble adult worm antigen by enzyme immunoassay. The IgG antibody response showed a characteristic pattern with highest reactivity against both gut associated and soluble egg antigens in the age group 10-14 years, when both prevalence and intensity of the infection were highest. Reactivity against somatic associated antigen was also high in this age group, but it increased slightly and remained at high level in the older ages. It is thought that such antigen is exposed mainly after the death of the parasite and that the antigenic stimulation may remain throughout most of the life of infected individuals. On the other hand, the IgG antibody reactivity against soluble adult worm antigen was low during childhood, but it increased significantly with age. It is suggested that repeated booster effects are needed for more potent response against these antigenic components. The finding of high levels of total IgE already in the youngest age groups, together with low specific IgE response, indicates that mainly other antigens are involved in the IgE production. The specific IgE response against soluble adult worm antigen was low but increased significantly with age.
Journal Article•
TL;DR: A difference in the transmission patterns should be considered when incorporating community-based focal plant molluscicide application in the integrated strategy for the control of schistosomiasis morbidity.
Abstract: Endemicity and seasonality of transmission of Schistosoma mansoni and S. haematobium were studied in Ile-Ife, south western Nigeria. Transmission of S. mansoni was demonstrated throughout the year in a man-made dam, whereas transmission of S. haematobium in a stream only occurred in the dry season. This difference in the transmission patterns should be considered when incorporating community-based focal plant molluscicide application in the integrated strategy for the control of schistosomiasis morbidity.
Journal Article•
TL;DR: Faecal coliform levels in the river water were unacceptably high during the Duzi Canoe Marathons and water samples taken from the river for bacteriological analysis showed a very low prevalence of S. haematobium.
Abstract: The prevalence of urinary schistosomiasis (Schistosoma haematobium) in canoeists in South Africa was estimated from examinations of urine samples taken from participants in the 1988 and 1989 Duzi Canoe Marathons on the Umsinduzi/Umgeni river in Natal. As an indicator of water quality during races, water samples were taken from the river for bacteriological analysis. Results showed a very low prevalence of S. haematobium and possible reasons for this are offered. Faecal coliform levels in the river water were unacceptably high during the races.
TL;DR: The findings suggest that the water demand index may be an important factor in the epidemiology of schistosome infections in rural communities.
Abstract: A helminthological study of stool and urine samples from 1037 people from 4 rural communities in Gumau District of Bauchi State, Nigeria, was carried out using formol-ether concentration and direct centrifugation methods respectively. 39·0% of persons examined were infected. Ova of Ascaris lumbricoides, Schistosoma haematobium and S. mansoni were the most common. Trichuris trichiura, hookworm, tape-worm and Strongyloides stercoralis were also encountered. 17·9% and 10·8% of examined persons had S. haematobium and S. mansoni infections respectively. A significant relationship was found between water demand index (number of persons per well) and infection with S. haematobium (r = 0·95) and S. mansoni (r = 0·88) (P < 0·01). Such a relationship was not found with other helminth infections. A significant association was also found between distance from a river and prevalence of S. haematobium (r = 0·94) and S. mansoni(r = 0·95) (P < 0·01), but not with the other helminth infections. These findings suggest that the water demand index may be an important factor in the epidemiology of schistosome infections in rural communities.
TL;DR: It is highly unlikely that the two species of Schistosoma mattheei and S. haematobium will evolve into a single species, neither does it seem that the virulence of the parental species will be influenced.
Abstract: A survey was conducted at a locality in the Eastern Transvaal Lowveld where the prevalence of human infection with the bovine parasite, Schistosoma mattheei, is relatively high. It was found that, when compared to the number of S. haematobium eggs released into the environment, the number of S. mattheei eggs, with enclosed hybrid miracidia, is small. The consequences of backcrossing between the hybrids and S. haematobium was considered; a mathematical model indicated that a high percentage of the S. haematobium population should contain a small proportion of S. mattheei genes. The results indicate that it is highly unlikely that the two species will evolve into a single species, neither does it seem that the virulence of the parental species will be influenced.
TL;DR: Reinfection pattern among 6- to 20-year-old subjects was studied in two Mauritanian villages of intense Schistosoma haematobium infection after a targeted chemotherapy with praziquantel and confirmed that gender, age and pretreatment level of infection were predictors of the rate of reinfection but that there was no interaction between these predictors.
Abstract: Reinfection pattern among 6- to 20-year-old subjects was studied over 24 months in two Mauritanian villages of intense Schistosoma haematobium infection after a targeted chemotherapy with praziquantel involving the whole community. Subjects received treatment according to the presence of haematuria/proteinuria and this indirect screening technique was able to identify 98–100% of the heavily infected subjects (50 + eggs/10 ml). The two villages differed with respect to their characteristics, quality of follow-up and reinfection pattern. The post-treatment 6-month cumulative incidence during the two transmission periods following the chemotherapy, estimated from a subset of 116 subjects, was 18·0% and 20·5%. Reinfection rates were higher among males (Cox-Mantel: P = 0·0015), among children 6–10 years of age than older ( P = 0·0078) and among subjects with more than 50 eggs/10 ml of urine before treatment than subjects with a lower egg output ( P = 0·009). A Cox proportional hazard regression model was fitted and confirmed that gender, age and pretreatment level of infection were predictors of the rate of reinfection but that there was no interaction between these predictors.
TL;DR: In an attempt to determine whether or not such refractory Bulinus africanus populations occur in eastern South Africa, F1 generation snails of populations from 8 different areas were exposed to miracidia hatched from eggs excreted in the urine of schoolchildren infected with Schistosoma haematobium in the Nelspruit district.
Abstract: The use of intermediate host snails of Schistosoma spp. which are insusceptible to infection has been proposed as a possible method of controlling schistosomiasis. The objective of this approach is to change the susceptibility of natural snail populations from being predominantly susceptible to a non-susceptible state, through the release of refractory snails into natural habitats. In an attempt to determine whether or not such refractory Bulinus africanus populations occur in eastern South Africa, F1 generation snails of populations from 8 different areas were exposed to miracidia hatched from eggs excreted in the urine of schoolchildren infected with Schistosoma haematobium in the Nelspruit district. The proportion of snails successfully infected ranged from 27 to 100%, which revealed considerable genetic heterogeneity amongst populations of the same snail species. One population from Natal could be regarded as partially refractory, while a laboratory population from Durban proved to be 100% susceptible. A completely refractory strain of B. africanus has not yet been identified.
TL;DR: The chaetotaxy of 84 samples or isolates of Schistosoma spp.
Abstract: The chaetotaxy of 84 samples or isolates of Schistosoma spp. from western or central Africa has been studied. Three indices were calculated for cercariae of each sample; their average value, the skewness and kurtosis of each indice was established. Each species (S. haematobium, S. curassoni, S. bovis and S. intercalatum) was discriminated with nine variables. The present work gives information to assess, specific diagnosis with simple calculations easily achieved on a small computer.
Journal Article•
TL;DR: Parasitological and malacological surveys were conducted round a fresh water lake, previously a salted lagoon, in the South of Bénin and leaded to measure prevalence of schistosomiasis, finding males were significantly more infected than females and young adults weremore infected than children or old individuals.
Abstract: Parasitological and malacological surveys were conducted round a fresh water lake, previously a salted lagoon, in the South of Benin and leaded to measure prevalence of schistosomiasis. 23 percent of population were found positive for Schistosoma haematobium and 13.4 percent for S. mansoni. Prevalences were different from locality to locality according to beach variations, but mean of parasite density was quite constant. Males were significantly more infected than females and young adults were more infected than children or old individuals. The prevalence distribution among people could be explained by behaviour and occupations. Five gastropod species were collected from which 2 are well known as intermediate host of S. haematobium (Bulinus globosus) and S. mansoni (Biomphalaria pfeifferi). A third species (Bulinus forskalii) which could be involved in S. haematobium transmission was found. Specimens of Bulinus were generally few and more represented in dry season. B. pfeifferi was more abundant especially at the end of rainy season. Populations of these 3 species were more dense by silty or swampy sides with shrub vegetation and poor oxygenated, acidic water rich in organic materials.