Snail Infection Rates Research Articles

Ecosystem links: Anthropogenic activities, environmental variables, and macrophytes structure snail preferences in man-made waterbodies

Freshwater snails act as obligate intermediate hosts for trematode parasites that cause trematodiases threatening public and veterinary health, and biodiversity conservation. While interest in snail control for trematodiases has re-emerged, their ecology remains poorly understood. We examined the relationship between ecosystem indicators – such as environmental variables, macroinvertebrates, macrophytes, and land use – and their correlation with snail abundance, diversity, and infection prevalence in 19 man-made ponds in eastern Zimbabwe. In total, 926 freshwater snails from 10 species were collected, with 547 individuals belonging to five schistosome-competent species: Bulinus tropicus, Bulinus truncatus, Bulinus globosus, Bulinus forskalii, and Biomphalaria pfeifferi. The remaining 379 snails comprised Radix natalensis, Gyraulus sp., and the exotic invasive species Melanoides tuberculata, Pseudosuccinea columella, and Physella acuta. Six cercarial types – mammalian schistosomes, avian schistosomes, longifurcate pharyngeates, echinostomes, amphistomes, and xiphidiocercariae – were isolated from 104 out of 926 snails (11.2 %). PCR revealed a significantly higher infection rate, with 70.2 % of snails testing positive for trematodes. Snail taxon diversity and infection rate significantly varied across land use types, with the lowest values observed in the commercial tobacco farm section, highlighting the potential adverse effects of agriculture on biodiversity. Ponds with extensive Lagarosiphon major (oxygen weed) coverage appeared to facilitate the presence and abundance of P. acuta and P. columella. Schistosome-competent snails such as B. truncatus and B. tropicus seemed to favor shallow water depths and more eutrophic sites characterized by high levels of nitrates, phytoplankton biomass, turbidity, and phycocyanin. These ponds were predominantly associated with the emergent macrophyte Cladium mariscus, revealing a potential association with important intermediate snail hosts. In conclusion, our study emphasizes the complex interplay among environmental factors, macrophyte composition, land use, and the abundance, diversity, and infection prevalence of freshwater snails, offering insights into potential strategies for targeted snail control and disease management in man-made waterbodies.

Evaluation of the Effects of Papain on Schistosoma mansoni: Miracidial Infection Capacity, Infection Prevalence, Cercarial Shedding and Molecular Changes in Biomphalaria alexandrina.

The aim of the present study is to assess the molluscicidal, larvicidal and genotoxicological activities of papain and how it can affect the host-parasite interactions. Toxicity of papain on snails by making series of concentrations to calculate LC50, and then study its larvicide effect on the free larval stages of S. mansoni and infection rate of snails. Papain has a molluscicidal activity on adult snails of Biomphalaria alexandrina with a lethal concentration LC50 equals to 43.1mg/L. In addition, it has activity on miracidia with half Lethal time (LT50) of 16.11min., and on cercariae with 12.1min. compared to control ones. The sub lethal concentration LC10 and LC25 (6.9 or 24.1mg/L, respectively) decreased the survival rate of snails at the first cercarial shedding, the rate of infection, the average total number of cercariae per snail, the shedding period and the life span of snails, while the prepatent period was significantly increased than the control ones. The morphological alterations in cercariae after exposure to papain were occurred where the cercariae lacked motility and some had a dark tail with complete detachment of head and tail. Compared to the control group, the levels of cytochrome oxidase subunit I (COI) and (ND1) genes significantly decreased in snails after exposure to papain. Papain could be used as a potential molluscicide for elimination of schistosomiasis and decrease its transmission and deterioration of host-parasite interaction.

Spatial Cluster Change of Schistosoma japonicum Transmission Foci in Indonesia During the Schistosomiasis Elimination Program.

The Government of Indonesia committed to eliminating schistosomiasis by 2025. Collaboratively snail control became one of the crucial strategies to ensure that the prevalence ofSchistosoma japonicuminOncomelania hupensis lindoensisreaches zero by the end of the program. This research investigated the spatial cluster change ofS. japonicumtransmission foci in Indonesia between 2017 and 2021. We mapped the snail foci, collected the snails, and calculated the snail density. We also conducted laboratory tests to detect the existence of cercariae in the snails. Identified infected snails were used to calculate the infection rate (IR) or snails' prevalence of schistosome cercariae among freshwater snails. We then analysed the spatial cluster using the Getis-Ord Gi* statistic to identify the hot and cold spots. The 5-year schistosomiasis elimination program successfully declined 18.84% of the snail foci and reduced 40.37% of the infected snail foci. Local spatial autocorrelation of snail density and infection rate identified that in 2017 and 2021, the number of cold spots decreased by 53.91% and 0%, while hot spots increased by 2.63% and 56.1%. The presence of more hotspots suggests a rise in the number of foci with high snail density and infection rates. The implementation of snail control was not optimal, and the parasite transmission through domestic animals still existed, causing the spatial cluster of hot spots to change during this period. Most hotspots have been observed near settlements, primarily in cocoa plantations, developed and deserted rice fields, grassland, and bush wetlands. During the schistosomiasis elimination program, the number of hot spots increased while cold spots decreased, and there were notable changes in the geographical distribution of hot spots, indicating a shift in the clustering pattern of schistosomiasis cases. The findings become essential for policymakers, particularly in selecting priority areas for intervention. In the Discussion section, we demonstrated the selection process based on the existence of hot and cold spots. Furthermore, we proposed that enhancing cross-sector integration is crucial, particularly in connection with the management of S. japonicum transmission through domestic animals.

Prevalence of Cercariae Infection in Snails From the Lymnaeidae and Physidae Families in Aquatic Regions of Guilan Province, Northern Iran, and the Effect of Some Physicochemical Parameters of Water on Snail Abundance and Infection Rate

Background: Some freshwater snails are as intermediate hosts of human and animal parasitic trematode. Study on freshwater snails’ fauna and cercariae infection play important role to detect sources of infection. Objective: The aim of the present study was to determine diversity and cercariae infection of Lymnaeidae and Physidae freshwater snails and effects of physicochemical parameters of water on their abundance and distribution in Guilan province, North of Iran. Methods: Over one year, a total of 117 regions in Guilan province were investigated for Lymnaeidae and Physidae freshwater snails and identified. Water samples of each region was also collected for physicochemical analyses. Identified snails were examined for cercariae infection by shedding method. Results: Of 39,486 collected snails, three species of two genera including 19,726 Lymnaea auricularia (49.96%), 4911 L. palustris (12.44%), and 14849 Physa acuta (37.6%) were identified. Cercariae infection rate was 2.36%. Identified cercariae were xiphidiocercariae (0.94%), echinostome (0.8%), furcocercous (0.44%), lophocercous (0.16%), and gymnocephalous (0.02%). The highest infection rate was in spring (3.37%). Temperature and pH had inverse effect and salinity and water electrical conductivity had direct effects on snails’ density. Conclusion: Two genera of Lymnaea and Physa exist in examined aquatic habitats of Guilan province, North of Iran in different seasons of a year. The physicochemical parameters of water had effects on distribution and snails’ density and also abundance of cercariae infection in them.

Spatial and seasonal distribution of human schistosomiasis intermediate host snails and their interactions with other freshwater snails in 7 districts of KwaZulu-Natal province, South Africa

The spatial and seasonal distribution, abundance, and infection rates of human schistosomiasis intermediate host snails and interactions with other freshwater snails, water physicochemical parameters, and climatic factors was determined in this study. A longitudinal malacology survey was conducted at seventy-nine sites in seven districts in KwaZulu-Natal province between September 2020 and August 2021. Snail sampling was done simultaneously by two trained personnel for fifteen minutes, once in three months. A total of 15,756 snails were collected during the study period. Eight freshwater snails were found: Bulinus globosus (n = 1396), Biomphalaria pfeifferi (n = 1130), Lymnaea natalensis (n = 1195), Bulinus tropicus (n = 1722), Bulinus forskalii (n = 195), Tarebia granifera (n = 8078), Physa acuta (n = 1579), and Bivalves (n = 461). The infection rates of B. globosus and B. pfeifferi are 3.5% and 0.9%, respectively. In our study, rainfall, pH, type of habitats, other freshwater snails and seasons influenced the distribution, abundance, and infection rates of human schistosomiasis intermediate host snails (p-value < 0.05). Our findings provide useful information which can be adopted in designing and implementing snail control strategies as part of schistosomiasis control in the study area.

Oncomelania hupensis Distribution and Schistosomiasis Transmission Risk in Different Environments under Field Conditions.

The goal of schistosomiasis prevention and control in China is shifting from transmission interruption to elimination. However, the area inhabited by the intermediate host, the snail Oncomelania hupensis, has not changed much in recent years. Different environmental types have different impacts on snail breeding, and understanding these differences is conducive to improving the efficiency of snail monitoring and control and to saving resources. Based on previous epidemiological data, we selected 199 villages in 2020 and 269 villages in 2021 from transmission control, transmission interruption, and elimination areas of snail breeding. Snail surveys were conducted in selected villages using systematic sampling and/or environmental sampling methods in six types of snail-breeding environments (canals, ponds, paddy fields, dry lands, bottomlands, and undefined environments). All live snails collected from the field were evaluated for Schistosoma japonicum infection using the microscopic dissection method, and a subsample of snails was subjected to loop-mediated isothermal amplification (LAMP) to assess the presence of S. japonicum infection. Snail distribution data and infection rate and nucleic acid positive rate of schistosomes in snails were calculated and analyzed. The 2-year survey covered 29,493 ha of the environment, in which 12,313 ha of snail habitats were detected. In total, 51.16 ha of new snail habitats and 107.76 ha of re-emergent snail habitats were identified during the survey. The occurrence rate of snails in canals (10.04%, 95% CI: 9.88-10.20%) and undefined environments (20.66%, 95% CI: 19.64-21.67%) was relatively high in 2020, and the density of snails in bottomlands (0.39, 95% CI: 0.28-0.50) and undefined environments (0.43, 95% CI: 0.14-1.60) was relatively high in 2021. Of the 227,355 live snails collected in this study, none were S. japonicum-positive as determined by microscopy. Of the 20,131 pooled samples, however, 5 were S. japonicum-positive based on LAMP analysis, and they were distributed in three environmental types: 3 in bottomland, 1 in dry land, and 1 in a canal. The bottomland environment has a high risk of schistosomiasis transmission because it contains a large area of newly emerging and re-emerging snail habitats, and it also had the most breeding snails infected with S. japonicum. Thus, this habitat type should be the key target for snail monitoring and early warning and for the prevention and control of schistosomiasis.

Urogenital Schistosomiasis Transmission and Human Water Contact Activities in Owena Reservoir/Dam, Ondo East Local Government Area, Ondo State, Nigeria

<i>Background</i>: This study on urogenital schistosomiasis transmission and the roles played by human water contact activities was carried out in selected three communities viz Owena, Kajola and Baiken, bordering Owena Reservoir/Dam in Ondo East Local Government Area, Ondo State, Nigeria for a period of twenty four months. <i>Objective</i>: To ascertain the effects of human water contact activities on urogenital schistosomiasis transmission. <i>Materials and Methods</i>: Each site was observed for water contact activities once every month for twenty-four months. Observation was made at each site in February (dry season), May (early rainy season), August (rainy season) and November (early dry season). During this period, records were taken about individuals entering and leaving the water. Various types of human water contact activities were grouped on the basis of general purpose of contact. With regards to degree of body exposure and mean duration of contacts; using canoe, fetching water, washing household utensils, sorting fish and washing exposed limbs, all involved exposure of only parts of the lower limbs (foot and leg) and or the upper limbs (hand and forearm) for a brief period of time grouped as partial contact activities. Water contact activities consist of washing clothes and fish nets, processing food products (such as cassava and palm oil) may involve exposure of most parts of the lower and/or the upper limbs for a longer period. Swimming and bathing commonly involve total exposure for a very long time and were designated as complete contacts. <i>Results</i>: General pattern of human water contact activities in the study revealed 34,686 (61.6%) domestic, 15,897 (28.2%) economic, 5,732 (10.2%) recreational and 15 (0.03%) religious activities. Frequency of these activities varied significantly (p<0.05) among stations and seasons but comparable from one year to the other. School children (5-19 years age group) spent more time on exposure than adults who spent more time on partial and limited exposure. As a result, the exposure index was significantly (p<0.001) age dependent and followed the same pattern as duration of contact. Site containing most infected <i>Bulinus globosus </i>snails was site 4 (KAJ 1) at Kajola community with snail infection rate of 9.2% and the same site 4 (KAJ 1) had the highest relative index of exposure (15,063.80) as well as level of total duration (14,215) of contact in minutes. <i>Conclusion</i>: Site 4 (KAJ 1) at Kajola community was the transmission site in Owena Reservoir/Dam, Ondo East Local Government Area, Ondo State, Nigeria.

Spatial distribution, abundance, and infection rates of human schistosome-transmitting snails and related physicochemical parameters in KwaZulu-Natal (KZN) province, South Africa

This study investigated the spatial distribution, abundance, and infection rates of human schistosome-transmitting snails and related physicochemical parameters and environmental factors in 11 districts in KwaZulu-Natal (KZN) province, South Africa, from December 2020–February 2021. Snail sampling was carried out in 128 sites by two people for 15 min using scooping and handpicking methods. Geographical information system (GIS) was used to map surveyed sites. In situ measurements of physicochemical parameters were recorded, while remote sensing was used to obtain measurements for climatic factors required to achieve the study's objective. Cercarial shedding and snail-crushing methods were used to detect snail infections. Kruskal-Wallis test was used to test the differences in snail abundance among snail species, districts, and habitat types. A negative binomial generalized linear mixed model was used to identify the physicochemical parameters and environmental factors influencing the abundance of snail species. A total of 734 human schistosome-transmitting snails were collected. Bu. globosus were significantly more abundant (n = 488) and widely distributed (found in 27 sites) compared to B. pfeifferi (n = 246) found in 8 sites. Bu. globosus and B. pfeifferi had infection rates of 3.89% and 2.44%, respectively. Dissolved oxygen and normalized difference vegetation index showed a statistically positive relationship, while normalized difference wetness index showed a statistically negative relationship with the abundance of Bu. globosus. However, there was no statistically significant relationship between B. pfeifferi abundance, physicochemical parameters, and climatic factors. Our study described the current distribution, abundance, and infection status of human schistosome-transmitting snails in KZN province, which will contribute to informing control measure policies for schistosomiasis.

Seasonal dynamics of Fasciola gigantica transmission in Prafi district, Manokwari Regency, West Papua, Indonesia.

Indonesia's farming practices are a perfect setting for establishing an infection with Fasciola gigantica which can result in economically detrimental. The objectives of the current study were to describe and analyze the transmission dynamics of fasciolosis (F. gigantica) in Prafi District, to provide information on effective control strategies and to identify risk factors associated with fasciolosis in cattle. Fecal samples were purposively collected from the rectum of 60 beef cattle in Prafi District, Manokwari Regency, West Papua Province, Indonesia. The samples were collected once a month for 8 months from April 2019 to November 2019. Furthermore, the samples were taken from two rearing system groups: 30 stall cattle and 30 cattle in a palm oil garden. The presence of F. gigantica eggs in the fecal samples was examined using a modified Danish Bilharziasis Laboratory technique-sedimentation. Meanwhile, the antigenic diagnosis of Fasciola in the fecal samples was analyzed using an enzyme-linked immunosorbent assay kit to perform an indirect sandwich assay on feces. Snails were collected from an irrigation canal, rice field, and palm oil garden canal around Prafi District. These snails were examined for infection with cercariae larvae of F. gigantica by cercarial shedding and crushing techniques. The peak occurrence of F. gigantica infection was identified in August (65.00%) and the lowest in June (35.00%). The highest prevalence of fasciolosis in cattle was recorded in August and November (90.00%) and the lowest was in May (40.00%). Moreover, the highest prevalence of fasciolosis in cattle exposed to the palm oil garden was recorded in April (53.33%) and the lowest prevalence of F. gigantica infection was recorded in June (23.33%). In total, 2046 snails were screened by the cercarial shedding and crushing method; of these, 426 (20.82%) were found to be positive for trematode cercariae. The prevalence of F. gigantica infection in Lymnaea spp. snails was highest in November (47.46%) and lowest in April (9.28%). The current study shows that beef cattle grown in two types of rearing systems in Prafi District were infected with F. gigantica during the dry and rainy season. It was revealed that Lymnaea spp. are common snails found in and around Prafi District, and can act as intermediate hosts with an infective stage of trematode. The transmission to cattle was highly effective, despite the short activity period, the low infection rate of snails, and the incidental anthelminthic treatment.

Systematic Review and Meta-Analysis on the Infection Rates of Schistosome Transmitting Snails in Southern Africa

Efforts to interrupt and eliminate schistosomiasis as a public health problem have increased in several Southern African countries. A systematic review was carried out on the infection rates of snails that cause schistosomiasis in humans. The searches were conducted in PubMed, Web of Science, and Scopus databases, using the PRISMA guidelines from inception to 24 February 2022. The study quality was assessed by using the Joanna Briggs Institute prevalence critical appraisal checklist. Pooled infection rates were estimated by using an inverse variance heterogeneity model, while heterogeneity was determined by using Cochran’s Q test and Higgins i2 statistics. A total of 572 articles were screened, but only 28 studies were eligible for inclusion based on predetermined criteria. In the selected studies, 82,471 Bulinus spp. and 16,784 Biomphalaria spp. snails were screened for cercariae. The pooled infectivity of schistosome intermediate host snails, Biomphalaria spp., and Bulinus spp. were 1%, 2%, and 1%, respectively. Snail infection rates were higher in the 1900s compared to the 2000s. A Luis Furuya–Kanamori index of 3.16 indicated publication bias, and a high level of heterogeneity was observed. Although snail infectivity in Southern Africa is relatively low, it falls within the interval of common snail infection rates, thus indicating the need for suitable snail control programs that could interrupt transmission and achieve elimination.

Efforts to eliminate schistosomiasis in Hubei province, China: 2005–2018

BackgroundThe Hubei province is one of the most schistosomiasis-epidemic-prone provinces in China. A series of strategies were adopted by the government to curb the rebound schistosomiasis endemic status that has prevailed since the early 2000s. This study aimed to elucidate the trends of schistosomiasis transmission and to appraise the effectiveness of the integrated control strategy in lake and marshland areas. MethodsSurveillance data of schistosomiasis in the Hubei province between 2005 and 2018 were analyzed, including conventional health control measures, integrated strategies, and measures that focused on the infection source. According to the local annual plan for schistosomiasis control in endemic counties, previous measures were human and snail control and surveillance. Residents aged 6–65 years were screened by an immunological detection method called indirect hemagglutination assay (IHA) after the transmission season each year. All residents who tested positive were then asked to provide a fecal sample for examination by the miracidium hatching technique (MHT) to detect the presence of schistosomes. Moreover, systematic snail surveys were conducted as a part of the combined environmental sampling method. The latter included integrated strategies and measures that focused on the infection source. Bovine stool samples were also collected and concurrently assessed using the MHT by the agriculture department, river-hardening slope protection was constructed by the water conservancy department, and forestation promotion was conducted by the forest department. The effectiveness of the integrated control strategy was assessed using two indicators of resident and livestock infection rates and three indicators of snail epidemics across all endemic areas. ResultsFrom 2005 to 2018, a total of 28. 46 million and 2. 05 million residents were assessed by immunological (IHA) and etiological (MHT) detection techniques, respectively. Snail surveys and molluscicide application were performed in 2. 26 hectares and 0. 37 hectares, respectively. Moreover, 2. 60 million bovines were assessed by etiological detection techniques (MHT). The river-hardening slope protection project was implemented in 503 places, and 46 thousand hectares in endemic areas underwent environmental modification. Forestation was implemented at an area of 0. 15 million hectares. Between 2005 and 2018, the epidemic indicators, including resident and livestock infection rates and the infested areas and infection rate of snails, all presented downward trends. The resident infection rate decreased from 3. 78% in 2005 to 0% in 2016, which persisted through 2018. The livestock infection rate decreased from 5. 63% in 2005 to 0% in 2013, which also persisted through 2018. From 2005 to 2018, the snail-inhabited area was slightly reduced, but the area of infected snails decreased to 0 in 2012; this persisted through 2018. All counties met the goal for schistosomiasis infection control, transmission control, and disruption of schistosomiasis activity in 2008, 2013, and 2018 separately. That means the goal has been achieved in each stage. ConclusionsThe decline of the schistosomiasis epidemic rate demonstrates that the Chinese government was successful in meeting its public health goal in Hubei province. In the next decade, precision interventions must be implemented in endemic counties with a relatively low epidemic status to achieve the goals of the Outline of the Healthy China 2030 Plan. A similar strategy can be applied in other countries to eliminate schistosomiasis globally.

Trematode Infections in Freshwater Snails and Seasonal Variations in Iringa and Arumeru Districts, Tanzania

Understanding of the larval trematode infections in snail intermediate hosts is essential in designing appropriate control measures. The current study was designed to determine larval trematode infection and seasonal variations in freshwater intermediate host snails Iringa and Arumeru Districts where trematode infections in cattle are endemic. A repeated cross-sectional study was adopted whereby Snails were collected three times a year (dry, early wet and mid wet). The selection of water bodies for sampling was based on random sampling and snails were collected by scooping method. The collected snails were identified based on the published morphological keys. A total of 2,016 snails were collected and 134 (6.6%) were found to be infected with trematode larvae. Six species of snails were identified that were Radix natalensis, Bulinus africanus group snails, Bulinus tropicus group snails, Bulinus forskalli group snails, Biomphalaria pfeifferi and Ceratophallous natalensis. Five morphologically different types of cercariae were identified that included gymnocephalous, amphistomes, mammalian Schistosoma, avian Schistosoma and Xiphidiocercariae. The findings on overall seasonal snail infection rates indicated low rate during the wet season while peak of infections were in the dry and early wet seasons. It is concluded that domesticated ruminants in the study areas are at high risk of getting infected with the trematodes (Fasciola and amphistomes) during dry and early wet seasons. Therefore, deworming of domesticated ruminants with an effective flukicide is recommended at the end of the wet season and followed by a treatment in mid dry season and the last treatment in early wet season.

Population Dynamics of Intermediate-Host Snails in the White Nile River, Sudan: A Year-Round Observational Descriptive Study.

We aimed to explore the population dynamics of snail in 3 sites of the White Nile in Sudan. More specifically, we aimed to investigate the annual patterns of snail populations that act as intermediate hosts of schistosomes and monthly snail infection rates and ecological characteristics presumably related to snail populations. We collected snails for 1 year monthly at 3 different shore sites in the vicinity of El Shajara along the White Nile river in Khartoum State, Sudan. In addition, we measured air and water temperatures, water turbidities, vegetation coverages, and water depths and current speeds. Most of the collected snails were Biomphalaria pfeifferi and Bulinus truncatus. The population densities of snails and their infection rates varied across survey sites. The collected snails liberated S. mansoni and S. haematobium cercariae as well as Amphistome and Echinostome cercariae. Infected snails were found during March–June. The ecological characteristics found to be associated with the absence of snails population were: high turbidity, deep water, low vegetation coverage (near absence of vegetation), high water temperature, and high current speed. To our knowledge, this is the first longitudinal study of the snail population and ecological characteristics in the main basin of the White Nile river.

Association between Schistosoma mansoni Infection Rates in Humans and in Biomphalaria pfeifferi snails in Akwanga, Nasarawa State, Nigeria

Schistosomiasis is a neglected tropical disease of medical importance. Intestinal schistosomiasis caused by Schistosoma mansoni is less wide spread than urinary schistosomiasis in Nigeria. A study was carried out in Akwanga, Nasarawa State to determine the association between S. mansoni infection rates (prevalence) in humans and infection rates in Biomphalaria pfeifferi snails in Akwanga, Nasarawa State, Nigeria. The study was carried out in two communities: Gwanje community and MadaHills community in Akwanga. For infection rates in humans, four hundred (400) urine samples were tested for S. mansoni antigen using point of care circulating cathode antigen (POC-CCA) test kit. Infection rates in snails were determined by S. mansoni cercarial shedding by snails. Biomphalaria pfeifferi snails were more abundant and had significantly higher (p&lt;0.05) infection rates in dry season than rainy season in both Gwanje and MadaHills. There was a positive correlation between infection rates in humans in Gwanje and MadaHills (21.5%) and (14%) and infection rates in snails in Gwanje and MadaHills (13.9%) and (9.6%) respectively. Snails collected close to portions of the river that community residents earmarked for open defecation within freshwater bodies had significantly higher (p&lt;0.05) infection rates (15.8%) than snails collected from across river banks, (7.1%) and snail infection rates in areas designated for fetching water for drinking and domestic use was (12.7%) . Health education, improved sanitation practices and annual chemotherapy with praziquantel could help interrupt disease transmission and bring about schistosomiasis control in both Gwanje and MadaHills communities.

The Prevalence of Bovine and Ovine Fasciolosis and the Associated Economic Loss Due to Liver Condemnation in and around Debire Birhan, Ethiopia

CA cross-sectional survey was conducted from October 2013 up to March 2014 to assess the prevalence, risk factors and direct economic loss of bovine and ovine fasciolosis in and around Debire Birhan, a town of North shoa Amhara Regional state. In the present study coprology, postmortem examination, questionnaire survey and an abattoir retrospective data were retrieved and analyzed. Seven Kebeles were purposively selected for coprological examination by considering the number of cattle and sheep population of the area and proximity to parasitological laboratories. Coprological examination of fecal samples randomly collected from 300 cattle and 280 sheep revealed an overall prevalence of 62.3% in cattle and 60.7% in sheep whereas 450 (300 cattle and 150 sheep) animals were randomly selected from Debire Birhan Municipal Abattoir for post mortem examination and revealed a total prevalence of 58.6% and 56.0% in cattle and sheep, respectively. This study shows that risk factors such as locality, species and age didn’t show significant effect on the prevalence of infections in both cattle and sheep (P&gt;0.05). However, season, sex, and body condition revealed significant difference (P&lt; 0.05) as higher degree of infections were detected in Autumn, female and in poor body conditioned, respectively. Species identification revealed that F. hepatica was highly abundant (43.8%) as compared to Fasciola gigantica (10.2%) in cattle. Likewise sheep livers also harbored F. hepatica (44.0%) and F.gigantica (15.5%). Certain proportion of mixed and unidentified immature fluke infection also common in both species. The economic loss incurred due to condemned liver as a result of bovine and ovine fasciolosis was estimated to be 59,387ETB (2969USD) per annum. In conclusion, fasciolosis was proved to be widely distributed disease with higher prevalence and great impact on the economy. Therefore integrated vector and parasite control approaches should be involved so as to reduce the snail burn and infection rate. Key words: Abattoir, Bovine, Ovine, Coprology, Economic significance, Fasciolosis, Prevalence. Debire Birhan.

Modelling local areas of exposure to Schistosoma japonicum in a limited survey data environment

BackgroundSpatial modelling studies of schistosomiasis (SCH) are now commonplace. Covariate values are commonly extracted at survey locations, where infection does not always take place, resulting in an unknown positional exposure mismatch. The present research aims to: (i) describe the nature of the positional exposure mismatch in modelling SCH helminth infections; (ii) delineate exposure areas to correct for such positional mismatch; and (iii) validate exposure areas using human positive cases.MethodsTo delineate exposure areas to Schistosoma japonicum, a spatial Bayesian network (sBN) was constructed. It uses data on exposure risk factors such as: potential sites for snails’ accessibility, geographical distribution of snail infection rate, and cost of the community to access nearby water bodies. Prior and conditional probabilities were obtained from the literature and inserted as weights based on their relative contribution to exposure; these probabilities were then used to calculate joint probabilities of exposure within the sBN.ResultsHigh values of probability of S. japonicum exposure correspond to polygons where snails could potentially be present, for instance in wet soils and areas with low slopes, but also where people can easily access water bodies. Low correlation (R2 = 0.3) was found between the percentage of human cases and the delineated probabilities of exposure when validation buffers are generated over the human cases.ConclusionsThe utility of a probabilistic method for the identification of exposure areas for S. japonicum, with wider application for other water-borne infections, was demonstrated. From a public health perspective, the schistosomiasis exposure sBN developed in this study could be used to guide local schistosomiasis control teams to specific potential areas of exposure, and improve efficiency of mass drug administration campaigns in places where people are likely to be exposed to the infection.

Biomphalaria camerunensis as a viable alternative intermediate host for Schistosoma mansoni in southern Cameroon

BackgroundIntestinal schistosomiasis due to Schistosoma mansoni was mapped in Cameroon in the 1990s and preventive chemotherapy launched since 2005. A situation analysis conducted in 2011 revealed an increase in schistosomiasis transmission, especially in the equatorial part of the country, despite the fact that Biomphalaria pfeifferi, the main intermediate host of this parasite, is now scarce in many foci. Biomphalaria camerunensis, restricted to the equatorial part of the country, is considered as a less suitable host for S. mansoni due to it resistance to the parasite, although exhibiting a better survival than B. pfeifferi. In a context where human migration is quite frequent as a consequence of terrorism, war in neighboring countries, as well as development of hydraulic projects, it seems appropriate to evaluate the current epidemiological role of B. camerunensis to estimate the risk of extension of S. mansoni distribution in Cameroon. To do this, the susceptibility of three B. pfeifferi and five B. camerunensis populations to a strain of S. mansoni was assessed. Juvenile snails (G1) of each population were infected with S. mansoni miracidia, and prepatent period, infection and survival rates of infected snails, as well as cercarial production were recorded and compared between snail species and populations.ResultsCompatibility tests were performed on a total of 827 snails: 344 B. pfeifferi and 483 B. camerunensis. Infection rates were quite heterogeneous, higher in B. pfeifferi (61.5%) as compared to B. camerunensis (7.8%) (Chi-square test: χ2 = 258.88, df = 1, P < 0.0001). All the three B. pfeifferi-infected populations were susceptible to S. mansoni. However, among the five B. camerunensis populations tested, four were susceptible to S. mansoni, with 21.9% as the highest infection rate. The prepatent period was, on average, shorter in B. pfeifferi than in B. camerunensis (P < 0.0001), but the cercarial production was significantly higher in B. camerunensis as compared to B. pfeifferi (P < 0.001).ConclusionThese findings indicate that B. camerunensis populations might substantially contribute to S. mansoni transmission and dissemination in Cameroon, their low susceptibility being compensated by their high cercariae production. More attention and surveillance towards this species are required to achieve intestinal schistosomiasis elimination in Cameroon.

Interrupting seasonal transmission of Schistosoma haematobium and control of soil-transmitted helminthiasis in northern and central C\xf4te d\u2019Ivoire: a SCORE study protocol

BackgroundTo achieve a world free of schistosomiasis, the objective is to scale up control and elimination efforts in all endemic countries. Where interruption of transmission is considered feasible, countries are encouraged to implement a comprehensive intervention package, including preventive chemotherapy, information, education and communication (IEC), water, sanitation and hygiene (WASH), and snail control. In northern and central Côte d’Ivoire, transmission of Schistosoma haematobium is seasonal and elimination might be achieved. In a cluster-randomised trial, we will assess different treatment schemes to interrupt S. haematobium transmission and control soil-transmitted helminthiasis over a 3-year period. We will compare the impact of (i) arm A: annual mass drug administration (MDA) with praziquantel and albendazole before the peak schistosomiasis transmission season; (ii) arm B: annual MDA after the peak schistosomiasis transmission season; (iii) arm C: two yearly treatments before and after peak schistosomiasis transmission; and (iv) arm D: annual MDA before peak schistosomiasis transmission, coupled with chemical snail control using niclosamide.Methods/designThe prevalence and intensity of S. haematobium and soil-transmitted helminth infections will be assessed using urine filtration and Kato-Katz thick smears, respectively, in six administrative regions in northern and central parts of Côte d’Ivoire. Once a year, urine and stool samples will be collected and examined from 50 children aged 5–8 years, 100 children aged 9–12 years and 50 adults aged 20–55 years in each of 60 selected villages. Changes in S. haematobium and soil-transmitted helminth prevalence and intensity will be assessed between years and stratified by intervention arm. In the 15 villages randomly assigned to intervention arm D, intermediate host snails will be collected three times per year, before niclosamide is applied to the selected freshwater bodies. The snail abundance and infection rates over time will allow drawing inference on the force of transmission.DiscussionThis cluster-randomised intervention trial will elucidate whether in an area with seasonal transmission, the four different treatment schemes can interrupt S. haematobium transmission and control soil-transmitted helminthiasis. Lessons learned will help to guide schistosomiasis control and elimination programmes elsewhere in Africa.Trial registrationISRCTNISRCTN10926858. Registered 21 December 2016. Retrospectively registered.

Study on Oncomelania hupensis snails infected with Schistosoma japonicum miracidia under different conditions in snail-existent non-endemic areas of schistosomiasis in Nantong City

To understand the forming cause of the Oncomelania hupensis snail-existent non-endemic areas of schistosomiasis (SENEAS), and to verify the conclusion of previous studies, so as to provide the evidence for schistosomiasis monitoring in such areas in Nantong City, Jiangsu Province. The controlled field tests were carried out to observe the O. hupensis snails artificially infected by schistosome miracidia in SENEAS. The influence of the soil from SENEAS and the endemic areas on O. hupensis snails artificially infected by miracidia were observed. All the experimental snails could be infected by schistosome miracidia except the smooth-shell snails from Tangyuan Village in the controlled field test environment of SENEAS or the endemic areas. The infection rates of the smooth-shell snails were lower than those of the ribbed-shell snails, but there were no statistically significant differences. The mortality rates of the smooth-shell snails were higher than those of the ribbed - shell snails, which were statistically significant (χ2Xindian = 135.118, χ2Shuangdian = 122.836, χ2Baipu =154.436, χ2Dingyan = 138.288, χ2Control = 151.923, all P < 0.01). There were no significant differences in the infection rates of snails between each test group of the soil from SENEAS and the endemic areas (χ2Rugao = 0.071, χ2Rudong = 0.216, both P > 0.05). Also there was no significant difference between each test group and the control group without soil (χ2 = 7.148, P > 0.05). It is likely to form the spread of schistosomiasis in SENEAS in Nantong City with sufficient amount of infection source of schistosomiasis imported. It is still necessary to implement the surveillance of schistosomiasis and O. hupensis snails in Nantong City.

Black spot infection in juvenile steelhead trout increases with stream temperature in northern California

Climate change will increase water temperature in rivers and streams that provide critical habitat for imperiled species. Warmer water temperatures will influence the intensity and nature of biotic interactions, including parasitism. To better understand the factors influencing a neascus-type parasitic infection known as black spot disease, we examined the relationship between infection rate in juvenile steelhead trout (Oncorhynchus mykiss), abundance of another intermediate host (ramshorn snail, Planorbella trivolvis), and water temperature. We quantified infection patterns of trout at seven sites within the South Fork Eel River in northern California, visiting each site on three different occasions across the summer, and recording water temperature at each site. We also quantified infection patterns in trout captured from two tributaries to the South Fork Eel River. Overall, trout infection rates were highest in sites with the warmest temperatures. The abundance of ramshorn snails was positively related to both water temperature and black spot infection rates in juvenile trout. Both snail abundance and infection rates increased rapidly above a 23 °C daily maximum, suggesting a threshold effect at this temperature. We suggest that warmer temperatures are associated with environmental and biotic conditions that increase black spot disease prevalence in threatened steelhead trout. A comparison of our results with similar data collected from a more northern latitude suggests that salmonids in California may be warm-adapted in terms of their parasite susceptibility.