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Evaluation of pilot control trial of intestinal schistosomiasis in the Finchaa Sugar Estate, Ethiopia.

Intestinal schistosomiasis is undergoing a rapid increase in magnitude in Finchaa Sugar Estate in Ethiopia. A pilot control trial of intestinal schistosomiasis was instituted in 1995 to reduce the magnitude of the disease and introduce sustainable schistosomiasis control approaches in the Sugar Estate. Following initial parasitological survey of all the camps in the Sugar Project area in 1995 using Kato method, mass chemotherapy of the heavily infected residents of Camp 7 and selective treatment of lightly infected residents of other camps were made using praziquantel. Endod (type 44) was applied to transmission sites along Fekerie stream in Camp 7 on quarterly basis whenever Biomphalaria pfeifferi was detected. Other inputs to the project as parts of capacity building included transplantation of Endod cuttings (type 44), training and health education. Cross sectional parasitological surveys were made in 1998 to assess the impact of the pilot control trial. The results of stool examination showed that the prevalence of schistosomiasis was reduced from 30% in 1995 to 26% in 1998 among residents of Camp 7 and the intensity of infection from 198 eggs per gram of feces (EPG) in 1995 to 85 EPG in 1998. Similarly, the prevalence of infection among children in Finchaa Valley Elementary School was reduced from 78% in 1994 to 56% in 1998 and the reduction in respective intensity of infection was from 283 EPG to 114 EPG. Although significant reduction in the magnitude of the disease was not achieved, the control activities were taken over by the Sugar Project Polyclinic to ensure sustainability. In addition to chemotherapy and snail control using Endod, other disease non-specific methods such as health education should be used to get maximum benefit from such facilities as latrines, and ensure participation of the community in order to sustain the control activities.

Adolescent↗

Succinate-DCPIP and NADH-fumarate oxidoreductases in fresh water snails susceptible and non susceptible to schistosoma infection.

The activities of succinate-DCPIP oxidoreductase (SO) and NADH-fumarate oxidoreductase (FR) were determined in tissue homogenate of Biomphalaria alexandrina and Bulinus truncatus, the snail vectors of Schistosomiasia. A parallel study was done on Lymnea truncatula snails which are not susceptible to Schistosoma infection. The Michaelis constant (Km) and maximum velocities (Vmax) for fumarate reduction and succinate oxidation by the tissue homogenates from the three species were determined. The results obtained showed that both susceptible species are aerobic and lactate is the sole end product of anaerobic glycolysis. Lymnea truncatula snails are facultative anaerobic producing succinate as a major end product in the glycolytic pathway.

Animals↗

Spot light survey on fresh-water snails of medical importance in Al Fayoum Governorate, Egypt.

In a survey carried out during Summer and Autumn of 2004, for snails of medical importance, nine species were recovered. These were Biomphalaria alexandrina, B. glabrata, B. pfeifferi, Bulinus truncatus, B. forskalii, Lymnaea natalensis, Bellamya (=Vivipara) unicolor, Physa acuta and Hydrobia musaensis. Parasitological examination revealed that B. alexandrina, B. glabrata and L. natalensis harboured immature stages of their concerned trematode parasites. Moreover, P. acuta harboured the immature stage of the nematode parasite Parastrongylus cantonensis.

Angiostrongylus cantonensis↗

[Development of the partenitae infrapopulation of Echinostoma caproni (Digenea: Echinostomatidae)].

The first generation of Echinostoma caproni partenitae is represented maternal sporocysts developing in the cardium of the Biomphalaria mollusk. During all their life, they produce rediae of maternal generation. Rediae of Echinostoma caproni of all generations are similar. The first generation consists of maternal rediae forming only redoid embryos. Due to this process, the number of partenitae increases very fast. The next generations are represented by daughter rediae. In the beginning of their life they produce redoid embryos but later begin forming cercariae. The number of rediae produced before this shift of production depends on the population density. Further, the partenitae retain their potential ability to form rediae but realize it in exceptional cases. Generative organs of all generations are germinal masses. Proliferation of generative elements and beginning stages of redia and cercaria development take place within these masses. The infrapopulation of E. caproni belongs to the "prolonged type", because it is a complete microhemipopulations; its existence is limited by a lifespan of the mollusk host.

Animals↗

Modeling the distribution of Schistosoma mansoni and host snails in Uganda using satellite sensor data and Geographical Information Systems.

The potential value of MODIS satellite sensor data on Normalized Difference Vegetation Index (NDVI) and land surface temperatures (LST) for describing the distribution of the Schistosoma mansoni-"Biomphalaria pfeifferi"/Biomphalaria sudanica parasite-snail system in inland Uganda, were tested by developing annual and seasonal composite models, and iteratively analysing for their relationship with parasite and snail distribution. The dry season composite model predicted an endemic area that produced the best fit with the distribution of schools with > or =5% prevalence. NDVI values of 151-174, day temperatures of 26-36 degrees C, and night temperatures of 15-20 degrees C were used as criteria for the prediction model. Using the same approach with host snail data indicated that most of Uganda is suitable "B. pfeifferi"/B. sudanica habitat, except for possibly the north-eastern region of the country. The parasite, however, appears to be restricted in its distribution in both the north-eastern and the south-western regions of Uganda. The absence of disease in the south-west can not be attributed to the absence of snail hosts. Results suggest a combination of satellite sensor data on temperature and standard climate data on precipitation, as the best ecological determinants of the S. mansoni-"B. pfeifferi"/B. sudanica system. Satellite composite models and logistic regression analysis, suggest low night time temperature as one of the significant factors inhibiting S. mansoni transmission in the south-western highland areas of Uganda. The developed models are, however, unique, representing species-specific ecologic preferences of the S. mansoni-"B. Pfeifferi"/B. sudanica system in inland Uganda. Further validation studies are needed to test the value of the model in other countries in East Africa.

Animals↗

Activity of some hydrolytic enzymes in tissue homogenates and haemolymph of fresh water snails, intermediate hosts in schistosomiasis.

The activities of 5-nucleotidase (Ec.3.1.3.5), alkaline phosphatase (Ec.3.1.3.1), glucose-6-phosphatase (Ec.3.1.3.9), and ribonuclease (Ec.3.1.13) had been measured in tissue homogenate and in haemolymph of Biomphalaria alexandrina, the specific intermediate host for the parasitic disease schistosomiasis, induced by the parasite Schistosoma mansoni.

Alkaline Phosphatase↗

Infectivity of Echinostoma friedi miracidia to different snail species under experimental conditions.

The infectivity of Echinostoma friedi (Trematoda: Echinostomatidae) miracidia was studied experimentally in a range of laboratory-reared snails that coexist in the same natural locality, namely Radix peregra, Lymnaea fuscus, L. truncatula (Lymnaeidae), Gyraulus chinensis, Helisoma duryi (Planorbidae) and Physella acuta (Physidae), and snails from different geographical origins acting naturally or experimentally as intermediate hosts of Schistosoma spp., namely Planorbarius metidjensis (from Málaga, Spain), Biomphalaria glabrata (Guadeloupe), B. alexandrina (Egypt) (Planorbidae), Bulinus cernicus (Mauritius), B. globosus (Zambia), B. natalensis (South Africa) and B. truncatus (Niger) (Bulinidae). Six species of snails were found to be susceptible, with the rate of infection ranging from 0 to 36.7%. The highest infection was detected in R. peregra. The low host specificity of E. friedi might have an epidemiological significance as a requisite for a recent establishment in a new geographical area.

Animals↗

Miracidia of Schistosoma japonicum: approach and attachment to the snail host.

Schistosoma japonicum miracidia swim directed along a chemical gradient toward the snails Oncomelania hupensis and Biomphalaria glabrata, and they turn back when the concentration of attractive chemicals decreases. The host signal for this chemotactic response has a molecular weight of more than 30,000. When swimming miracidia encounter the surface of O. hupensis or agar containing O. hupensis snail-conditioned water (SCW) they perform the host-specific responses "contact with return," "repeated investigation," and "attachment," but they do not exhibit such behavior when encountering B. glabrata surface or agar containing B. glabrata SCW. Thus S. japonicum miracidia respond to different host signals when they approach snails than when they attach to snails.

Animals↗

Experimental observations on the specificity of Strigea falconispalumbi (Trematoda: Strigeidae) toward planorbid first intermediate hosts.

Planorbis planorbis, Planorbarius corneus and Biomphalaria alexandrina (Egyptian strain) were ascertained as new experimental first intermediate hosts, thus bringing the total number of planorbid experimental first intermediate hosts to eight. The highest degree of compatibility was exhibited with P. planorbis (infection prevalence 80%) followed by P. corneus (46.6%), whereas B. alexandrina (as snail species not occurring in the geographical range of S. falconispalumbi) showed the lowest degree of compatibility (23.3%).

Animals↗

Transmission of intestinal schistosomiasis in Bahir Dar, northwest Ethiopia.

Parasitological, malacological and transmission studies were made for a period of one year in the town of Bahir Dar, northwest Ethiopia. The overall prevalence of schistosomiasis mansoni in residents of Kebeles 8, 9 and 10 was 12%. The prevalence in Sertse Dengel school children was 45% and that in Dil Chibo school children was 32%. The peak prevalence in both sexes in school and non-school populations occurred in the age group 10-14 years. Intensity of infection showed a similar pattern of age variation as prevalence. Biomphalaria pfeifferi snail density peaked towards the end of the rainy season (September) in Lake Tana and around the middle of the dry season (January) on the shore of the River Abay. In September, infected snails were recovered from all collection sites. Of mice immersed in four water contact sites in September, schistosome infections developed in those immersed in three sites. Parasitological findings suggested that schistosomiasis infection rates depended on age and sex of individuals and geographical location of the place from the potentially infective water bodies. Snail population density and associated schistosomal infection in a human population depended on rainfall and associated ecological changes such as fluctuation in water level and vegetation density. As malacological findings and sentinel mouse immersion results indicated, it appeared that the main transmission season in Lake Tana region is towards the end of the rainy season although low level intermittent transmission may take place throughout the year.

Adolescent↗

The molluscicidal properties of Apodytes dimidiata subsp. dimidiata (Icacinaceae).

The molluscicidal and piscicidal activity of extracts from the leaves, berries and bark of the tree Apodytes dimidiata were evaluated experimentally. The leaves were highly toxic to both Bulinus africanus and Biomphalaria pfeifferi, the intermediate host snails of Schistosoma spp. B. pfeifferi profusely exuded mucus which appeared to render some protection against the toxic substance(s) of the plant but did not prevent their eventual demise. The LC10 after one-hour exposures of fish (Oreochromis mossambicus) was within molluscicidal levels.

Animals↗

A parasitological and malacological survey of schistosomiasis mansoni in the Beles Valley, northwestern Ethiopia.

A survey of schistosomiasis mansoni infection was conducted in an area of northwestern Ethiopia which has been targeted for an irrigation project. The proximity of settlements to water-bodies infested with Biomphalaria pfeifferi, and used extensively for bathing and domestic purposes, indicated that the potential for transmission is high. Snails shedding S. mansoni cercariae were found in two localities. Stool specimens from a total of 7517 persons were examined, including specimens from 4915 children age 7-14 years in 29 localities, as well as from the total population of four of the more heavily infected localities. The 10-14 year age group had the highest transmission potential, in terms of prevalence (overall 25%), intensity of infection, and absolute numbers of infected individuals, suggesting that screening and chemotherapy would be most cost-effective in that age group.

Adolescent↗

Outbreak of intestinal schistosomiasis in the Senegal River Basin.

Intestinal schistosomiasis has never been reported in the delta of the Senegal River Basin. A year and a half after the Diama dam became operational, a first case of Schistosoma mansoni infection was detected at Richard-Toll. In 1988 and 1989, 1,935 stool examinations out of a sample of 3,926 were found positive for S. mansoni. The progression of positive stool samples is rapid in all neighbourhoods of Richard-Toll: 1.9% positive examinations in 1988 compared to 71.5% in the last quarter of 1989. One thousand nine hundred and sixty nine Biomphalaria pfeifferi were collected during several malacological surveys carried out from February 1989 to December 1989 at three observation points. An emission of S. mansoni furcocercariae was determined in 44 out of 926 B. pfeifferi (4.75%) examined during this same period. Intestinal schistosomiasis is new in this area and spreading quickly. Rapid intervention measures are required immediately.

Adolescent↗

A laboratory study of the toxicity of the butanol extract of endod (Phytolacca dodecandra) on two species of freshwater fish and two species of aquatic snails.

The purpose of this study was to evaluate the toxicity of the butanol extract of Endod (Phytolacca dodecandra) on 4 species of aquatic animals. Groups of 10 mosquito fish (Gambusia affinis) and 8 bluegill (Lepomis macrochirus) were exposed to the butanol extract of Endod in 300 ml of water at concentrations of 0.0, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2 or 2.0 ppm. Groups of 10 tropical snails (Biomphalaria glabrata) and 10 pond snails (Physa spp) were also exposed to the crude extract in 50 ml of water at concentrations of 0.0, 1.0, 1.5, 2.0, 2.2, 2.5, 3.0, 4.0 or 5.0 ppm. Following a 24-h exposure period, the test subjects were transferred to extract-free water and observed for an additional 24 h. The number of dead animals was determined after the total 48-h concentration was plotted on logarithmic (probit) graph paper and the concentration of Endod which killed 50% of the test subjects (LC50) was determined. The butanol extract of Endod was lethal to 50% of the fish and snails at relatively low concentrations (less than 3.0 ppm). The results also indicated that fish were approximately 2 to 4 times more sensitive to Endod than snails.

Animals↗

On the effects of ivermectin on freshwater snails of medical and veterinary importance.

Ivermectin is lethal to Bulinus (Physopsis) globosus, Biomphalaria pfeifferi, and Lymnaea natalensis at concentrations of 0.08 micrograms/ml and above. Studies show that these snails will not recover from a 24 h exposure to 2.00 micrograms/ml of Ivermectin in the laboratory at 28 +/- 2 degrees C. A time dependent toxicity to snails was recorded and an exposure of adult snails to sub lethal concentrations significantly reduced the number of eggs laid (r = -0.08, t = 2.64, P less than 0.05).

Animals↗

The molluscicidal properties of natural products from Ambrosia maritima.

The molluscicidal properties of Damsin "I", Ambrosin "II", and tribromodamsin "III" were investigated against the intermediate hosts of schistosomiasis Biomphalaria alexandrina and Bulinus truncatus. Although Damsin was to some extent more toxic against B. alexandrina than the other two compounds, it was less toxic than them against B. truncatus after 24 hr exposure periods. There is a flex relationship between concentration of Damsin and exposure period to prodce 100% mortality. The molluscicidal potency of Damsin remained stable over a wide range of pH values, but was affected by storage, sunlight and river bed-mud. Structure-activity relationship is included.

Animals↗

[Preliminary study of the molluscacide properties of guayacil: a raw extract of Guayacum officinale].

This paper reports the results of a preliminary study of the mollusk-killing properties of guayacil, a raw extract of the plant Guayacum officinalis, on Biomphalaria glabrata. Mollusks are exposed to several concentrations of the substance for periods ranging from 1, 6, and 24 hours and then were allowed to recover, according to the recommendations of the World Health Organization. The results indicate that guayacil has molusk-killing properties with an LC50 of 0.45 ppm and an LC90 of 0.95 ppm at 24 degrees C. Larger concentrations of 1 ppm resulted in 100% death rate, while 0.1 ppm did not prove lethal. All parts of the plant contain the active ingredient. Concentrations lower than 1 ppm are not lethal for flora or fauna.

Animals↗

Helminth and snail survey in Harerge region of Ethiopia with special reference to schistosomiasis.

2300 persons from 25 communities in Harerge Administrative Region were examined for intestinal helminths. The overall prevalence rates were: Schistosoma mansoni 19.4%, Ascaris lumbricoides 13.4%, Trichuris trichiura 7.9%, and Taenia species 5.8%. Other parasites found in less than 3% included: Hymenolepis nana, Hymenolepis diminuta, Enterobius vermicularis, Strongyloides stercoralis and hookworms. Three age groups, 5-9, 10-14, and 15-19 years, had approximately similar prevalence (34.9-38.8%), but younger children had heavier egg loads (geometric mean egg output per gram of feces (EPG) of 347, 340 and 248, respectively). Boys had a higher prevalence of egg load than girls (42.4%, 395 EPG vs 26.5%, 277 EPG). Infection rates among Moslems were higher than Christians (45.5 vs 23.7%), but they had smaller egg output (333 vs 412 EPG). The frequency of light, moderate and heavy infections showed a normal distribution at 27, 46 and 27%. Biomphalaria pfeifferi was found to be infected with S. mansoni in Hirna (42/250), Esakly (6/80) and Genda Adem (20/200), the latter two in the Erer valley. Urine samples from 8 localities were negative for S. haematobium infection. The need for further study in several river valleys with agricultural potential is suggested.

Adolescent↗