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At least 1,531 records · Page 85Linked to original sources
PubMed1995

Short report: diminished susceptibility to praziquantel in a Senegal isolate of Schistosoma mansoni.

There is a recent report of low efficacy of praziquantel (PZQ) treatment of human schistosomiasis in a new Schistosoma mansoni focus in northern Senegal. Biomphalaria pfeifferi snails with patent infections were collected from the area of the focus and transported to the United Kingdom. Groups of mice were infected with cercariae from this Senegalese isolate, or with laboratory-maintained Kenyan or Puerto Rican isolates. In two separate experiments, PZQ was less effective against the parasite from Senegal than against the two other geographic isolates. The reduced susceptibility of S. mansoni to PZQ in infected human populations has important implications for current schistosomiasis control programs.

Animals↗
PubMed1995

Comparative infectivity and survival of first-stage larvae of Angiostrongylus cantonensis and Angiostrongylus malaysiensis.

Angiostrongylus malaysiensis was isolated from wild rats Rattus norvegicus in a seaport area of Kitakyushu City, Kyushu, Japan in 1990. The infectivity and survival capacities of first-stage larvae of A. malaysiensis and Angiostrongylus cantonensis were compared under various conditions. Infectivity of first-stage larvae of the former in Biomphalaria glabrata was much lower than that of the latter. In an exposure at various pHs, and with various proteases and tissue homogenates of B. glabrata, the survival of first-stage larvae of A. malaysiensis was also lower than that of A. cantonensis. This lower survival was compared to that of A. cantonensis in response to desiccation of rat feces and high water temperature. First-stage larvae of A. malaysiensis thus appear to be influenced by conditions in the host's feces, specifically temperature and desiccation, and also show a greater sensitivity to pH and component proteases in the snail body than A. cantonensis.

Angiostrongylus↗
PubMed1994

Urinary and intestinal schistosomiasis in the Tono Irrigation Scheme, Kassena/Nankana District, upper east region, Ghana.

Human- and snail-related aspects of transmission of urinary and intestinal schistosomiasis were studied in the Tono Irrigation Scheme in northern Ghana. The scheme became operational in 1977. In some schools, prevalences and intensities of both Schistosoma mansoni and S. haematobium infection were alarmingly high, pointing to human schistosomiasis being at least focally a health problem of major public health concern. Positive correlations between intensity of schistosome infection, as measured by egg output, with frequency of visible haematuria and history of haematuria point to opportunities for community-based assessment of morbidity and identification of high risk population subgroups. Bulinus globosus is the most important snail host for S. haematobium while Biomphalaria pfeifferi serves as host for S. mansoni. While transmission of S. mansoni is taking place only in the main canal, transmission of S. haematobium takes place in all parts of the irrigation system (lateral canal, night storage dam, main reservoir). Transmission of both S. mansoni and S. haematobium is rather focal and a seasonal pattern of transmission is indicated with peak transmission taking place during the beginning of the dry season. The high endemicity and the transmission patterns described in this study call for an integrated approach to schistosomiasis morbidity control in the area.

Adolescent↗
PubMed1994

Studies on transmission and schistosome interactions in Senegal, Mali and Zambia.

The transmission and interaction of schistosomes in the Senegal River Basin in Mali and Zambia are reviewed and some preliminary field data are presented. In the Senegal River Basin four species of schistosomes are prevalent: Schistosoma mansoni, S. haematobium, S. bovis and S. curassoni as well as the following potential intermediate hosts: Biomphalaria pfeifferi, Bulinus globosus, B. umbilicatus, B. truncatus, B. senegalensis and B. forskalii. The role of each of these species in the transmission of schistosomes in man and domestic stock is discussed. Recent ecological changes caused by the construction of dams at Diama and Mananatali on the Senegal River, such as reduction in salinity, more stable water flow, creation of irrigation canals and development and extension of rice culture, have contributed towards the occurrence of new outbreaks of both intestinal and urinary schistosomiasis in the Senegal River Basin. In Mali, the four main areas of high prevalence of S. haematobium are Office du Niger (irrigation areas), Bandiagara (small dams), Selingué (dam areas) and Baguineda (irrigation areas). Apart from the Office du Niger, S. mansoni infections are rare. Surveys were carried out in the Dogon Country (Bandiagara District) in an attempt to confirm the recent independent reports of the presence of S. intercalatum. Data based on egg morphology and Ziehl Neelsen staining of egg shells suggested the possible occurrence of S. haematobium x S. intercalatum hybrids. Potential factors affecting the focal endemicity of S. haematobium in Mali are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Intestinal helminthic infections in the southern Rift Valley of Ethiopia with special reference to schistosomiasis.

Nineteen communities located in the southern part of the Ethiopian Rift Valley were surveyed for S. mansoni infection and other helminth parasites of man. S. mansoni infected individuals were recorded in 11 communities and human prevalence reached more than 10% in 4 of them. The snail intermediate hosts were Biomphalaria pfeifferi in the lower Omo River basin and B. sudanica in the Rift Valley lakes. Other parasites encountered included A. lumbricoides (11.2%), T. trichiura (10.3%), hookworms (25.3%), Taenia sp. (8.1%), Strongyloides sp. (2.9%), H. nana (0.8%), Trichostrongylus sp (0.3%) F. hepatica (0.1%) and E. vermicularis (0.1%). In some communities the prevalence of hookworms, A. lumbricoides and T. trichiura reached 70%, 66.6% and 60%, respectively. A strong association (r = 0.9) was observed between altitude and parasite prevalence and burden. In nine communities located below 1200 metres, infected individuals harboured nearly two or less the number of parasite species while in 10 communities located at altitude above 1200 metres, multiple infection with three or more parasites reached as high as 53.2%. Similarly, the average parasite species per infected person ranged from 0 to 1.4 in the nine communities located at lower altitudes and from 1% to 2.6% in the 10 communities located at higher altitudes. By ages, both prevalence and multiparasitism are significantly in favour of those below 20 years of age (P < 0.005) although hookworms are prevalent in a wider age range. The widespread occurrence of intestinal schistosomiasis in the southern Rift Valley and the epidemiological pattern of other intestinal helminth parasites of man in this section of the Valley are discussed.

Adolescent↗
PubMed1994

The status of Schistosoma mansoni and snail hosts in Tigray and northern Wello regions, northern Ethiopia.

A survey of Schistosoma mansoni infection and snail hosts was carried out in 1992 in six accessible schools and 11 water bodies respectively. Five to ten per cent of the students were randomly selected for stool examination by the Ritichie's method. In Adwa town, however, stools of 100 students out of the 199 selected were re-examined by Kato's method to assess intensity of infection. Results of stools examined by Ritichie's method showed that S. mansoni positive patients were present in four out of six (66.7%) schools, the prevalence for school ranging from 1% in Maychew to 61.8% in Adwa. In all the localities, there was significant male preponderance in the prevalence of infection (p < 0.05). Among those whose stools were examined by the Kato's method in Adwa town, both prevalence and geometric mean egg count per gram of faeces (EPG) were highest in the 10 to 14 years age group reaching 68% and 597 followed by 64% and 591 respectively in the 15 to 19 years of age. Of the S. mansoni positive students in Adwa, 86% excreted 200 or more EPG, 84% of those in the 10 to 14 years of age excreted as high as 1,600 EPG. Sexwise, no significant difference was observed in EPG (p > 0.05). Biomphalaria pfeifferi, the principal snail host of S. mansoni in Ethiopia, were collected from five out of the 11 waterbodies and were found shedding human schistosome cercariae in two of them, their infection rate reaching 0.7%. The ecological characteristics observed were found suitable for snail propagation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Schistosomiasis in the southern region of Oman: vector snails and serological identification of patients in several locations.

The snail Biomphalaria arabica is apparently ubiquitous in the south of Oman (Dhofar province). Snails bred in the laboratory were susceptible to infection with miracidia of Schistosoma mansoni (Puerto Rican strain). The snail Bulinus wrighti, a potential intermediate host of S. haematobium, was found for the first time in Dhofar. Human sera from five localities had antibodies against adult worm antigens and in particular against Sm31/32. The prevalence of seropositive patients was 28% of 47 farm workers, 12% of 99 out-patients from a clinic and 1% of 389 children from four localities. Autochthonous transmission of schistosomiasis in Dhofar is discussed.

Adolescent↗
PubMed1994

Laboratory study on the molluscicidal effect of Earth Tec: an environmentally responsible copper sulfate product.

Studies were carried out, under laboratory conditions to evaluate the molluscicidal activity of Earth Tec on Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni. Earth Tec is an environmentally responsible copper sulfate product manufactured and marketed as an algicide/bactericide with an active ingredient form of copper ion (Cu++). A single application, of 1 ppm of copper equivalent, for 24 hours caused 100% mortality rate of the snails. Exposure for 48 hours to 1 ppm and 2 weeks to 0.25 ppm caused mortality rates of 84% and 100% respectively. It was concluded that this chemical compound is a promising molluscicide. Field studies are ongoing and will be published in due time.

Animals↗
PubMed1993

Kinetic potentials of certain scavenger enzymes in fresh water snails susceptible and non-susceptible to Schistosoma infection.

The activities of catalase (H2O2-oxidoreductase EC 1.11.1.6)- and glutathione reductase (EC 1.6.4.2) as two important scavenger enzymes, were measured in tissue homogenates of Biomphalaria alexandrina and Bulinus truncatus, the snail vectors of Schistosomiasis. A parallel study was done on Lymnea truncatula snails which are not susceptible to Schistosoma infection. The apparent Michaelis constant (Km) for both anzymes were determined in tissue homogenates of the three studied species. The results obtained showed that both susceptible species have higher affinity to hydrogen peroxide (H2O2) and oxidized glutathione (GSSG) than the non-susceptible one.

Animals↗
PubMed1993

Toxicity of aqueous bark extract of the tree Balanites aegyptiaca on the fish Oreochromis niloticus.

The toxicity of an aqueous extract of Balanites aegyptiaca on Oreochromis niloticus was investigated. Fry of the fish were exposed to acute and sublethal concentrations of the extract in 96-h and 56-d static bioassays, respectively. Susceptibility of the extract on freshwater snail, Biomphalaria pfeifferi, was tested. The LC50 of the lethal concentrations of the extract on the fish and the snails were 1.12 mg/l-1 and 2.0 mg/l-1 respectively, while the effects of the sublethal concentrations on the growth rate and haematocrit percentage of the fish were determined. Signs of toxicosis such as air gulping, reduction in tailfin beating rate and overturning were observed in the fish before death occurred. The toxicant also reduced the growth rate and haematocrit percentage of the fish. The mode of action of the toxicant seems to be haemolytic or an impairment of osmoregulation in the blood leading to an over-dilution of the blood.

Animals↗
PubMed1993

Toxicity of Azadirachta indica to freshwater snails and fish, with reference to the physicochemical factor effect on potency.

A preliminary crude screening of plants in Jos Metropolis showed that at a concentration of 100 mg/l-1 the stem bark extract of the Neem plant Azadirachta indica caused a 100 percent mortality when tested against three common snail intermediate host species, Biomphalaria pfeifferi, Bulinus truncatus, and Lymnaea natalensis after 24 hours exposure. Toxicity test with freeze-dried aqueous extract of the plant gave 96 hours LC50 values of 19.00 mg/l-1 (p > 0.05), 10.96 mg/l-1 (p > 0.05) and 15.13 mg/l-1 (p > 0.05) against B. pfeifferi, B. truncatus and L. natalensis, respectively. When a similar test was carried out on fish, Aphyosemon giardneri a 96 hour LC50 of 15.1 mg/l-1 was recorded. Extraction with alcohol, increase in temperature within the optimal range, increase in acidity of aquatic medium and cold storage improved the potency of the extract while boiling and room storage reduced it.

Animals↗
PubMed1995

A method for immunoisolation of sporocysts of Schistosoma mansoni in nonsusceptible snails.

A technique is described for immunoisolation of sporocysts of Schistosoma mansoni in nonsusceptible Biomphalaria glabrata by microencapsulation in agarose. Based on histological evidence, all 11 microencapsulated sporocysts implanted into 3 schistosome-resistant 13-16-R1 snails were alive at 72 hr postimplantation, although in a developmentally retarded condition. However, among 146 sporocysts derived from miracidia that had penetrated 5 snails, 96% were dead by 72 hr. These results suggest that hemocyte contact is necessary for rapid sporocyst death in vivo.

Animals↗
PubMed1977

In vitro development of Schistosoma mansoni cercariae.

Early cercarial embryos of Schistosoma mansoni developed to swimming cercariae within seven days in vitro, via the same sequence of stages as reported in vivo. The presence of living Biomphalaria glabrata cells (Bge line) was indispensable for proper development. Cultured cercariae were water-sensitive, gave no cercarienhüllen reaction, and appeared to lack the surface glycocalyx. Further development was not detected in mice or hamsters.

Animals↗
PubMed1996

Prevalence of Schistosomiasis and dynamics of its distribution in some villages in Qalyoubia Governorate.

A total of 1535 persons of different age, sex and occupation from 5 villages (Tanan, El-Sad, Sandiun, Kalama and Taha-nob) in Qalyoubia Governorate in Nile Delta were subjected to clinical, stool, urine and intradermal tests accompanied by a questionnaire for 500 of them. Snail vectors of Schistosome parasites were collected from 2 villages (El-Sad and Taha-nob) and snail densities in the waterways as well as the prevalence rate of infection with schistosomal cercariae were recorded. The results revealed that the average prevalence rate of Schistosoma haematobium in the 5 cillages was 4.9% (range 2.3% - 7.1%) and that of S. mansoni was 13.3% (range 11.4-14.4%). The overall prevalence of both types was 18.2% (range 13.7-21.4%). The average density of Biomphalaria alexandrina in the 2 village was 16.47% and that of Bulinus truncatus was 7.5%, the ratio was 2:1. The infectivity with schistosomal cercariae was very low with an average of 2.5% in B. Alexandrina and 1.5% in B. truncatus. Factors responsible for the decreased rates of schistosomiasis and snail infectivity were discussed.

Adolescent↗
PubMed1996

Cercariometry in the study of Schistosoma mansoni transmission in Egypt.

The recovery of Schistosoma mansoni cercariae was studied in experimental ditches and natural irrigation canals using a continuous operating centrifuge and a water suction sampling technique. Recovery of cercariae from static water in the ditches where caged infected Biomphalaria alexandrina snails were placed showed that cercariae recovered were more with increase of infected snails and decrease of water volume and were most abundant in the proximity of the snails which produced them. Shade or heavy vegetation cover reduced the recovery of cercariae. Results suggest also strong seasonal differences in diurnal patterns of cercarial recovery. An early morning peak with large number of cercariae occurred during hot weather while in cooler seasons cercariae appear in fewer numbers but persist for most of the day. Obtained information, beside contributing to knowledge of cercarial behaviour, should help to optimize taking water sample and consequently to increase efficiency of cercariometry techniques. In the natural irrigation system, cercariometry was significantly more sensitive in detecting transmission foci than snail sampling by a dip net.

Animals↗
PubMed1977

The molluscicidal properties of some Bayluscide homologues.

The molluscicidal properties of 5-nitro- and 3-nitro2',4'-dichloro salicylanilides and their mixture 5.5 : 1 were investigated against the intermediate hosts of schistosomes Bulinus truncatus and Biomphalaria alexandrina. Unlike Bayluscide, the activity of the new mulluscicides is not affected by strong sun radiation or by acidic pH. Their activity is resistant to storage, river-bed mud and lower temperature.

Animals↗
PubMed1996

Newly identified endemic areas of Schistosomiasis mansoni in Tigray, northern Ethiopia.

A survey of Schistosomiasis mansoni and Snail hosts was conducted in 1992-93 in Tigray Region. Forty accessible communities were selected at random and a total of 4786 children from elementary and junior high schools were examined for Schistosomiasis mansoni infection. Schistosomiasis mansoni positive children were found in 32 (80%) communities with prevalences ranging from 1% to 66% and an overall prevalence of 18.4%. Human prevalences of 5% and above were observed in 25 communities of which 19 are newly identified endemic foci. Significantly more males than females were infected with Schistosomiasis mansoni (P < 0.05). The age group of 10-19 years was most affected (P < 0.001). Biomphalaria pfeifferi were collected in 20 (58.8%) habitats of the total of 34 water bodies surveyed covering 18 communities. Infected snails were recovered from 12 (60%) of the 18 communities surveyed and six of these were newly identified transmission foci. The distribution of intestinal schistosomiasis in Tigray and the possible factors contributing to its spread are discussed and possible tactics of control suggested.

Adolescent↗