Modelling spatial distribution of snails transmitting parasitic worms with importance to human and animal health and analysis of distributional changes in relation to climate

Abstract

Abstract. The environment, the on-going global climate change and the ecology of animal species determine the localisation of habitats and the geographical distribution of the various species in nature. The aim of this study was to explore the effects of such changes on snail species not only of interest to naturalists but also of importance to human and animal health. The spatial distribution of freshwater snail intermediate hosts involved in the transmission of schistosomiasis, fascioliasis and paramphistomiasis (i.e. Bulinus globosus, Biomphalaria pfeifferi and Lymnaea natalensis) were modelled by the use of a maximum entropy algorithm (Maxent). Two snail observation datasets from Zimbabwe, from 1988 and 2012, were compared in terms of geospatial distribution and potential distributional change over this 24-year period investigated. Climate data, from the two years were identified and used in a species distribution modelling framework to produce maps of predicted suitable snail habitats. Having both climate-and snail observation data spaced 24 years in time represent a unique opportunity to evaluate biological response of snails to changes in climate variables. The study shows that snail habitat suitability is highly variable in Zimbabwe with foci mainly in the central Highveld but also in areas to the South and West. It is further demonstrated that the spatial distribution of suitable habitats changes with variation in the climatic conditions, and that this parallels that of the predicted climate change.

Predicting the spatial distribution of Biomphalaria straminea, a potential intermediate host for Schistosoma mansoni, in China

“…MaxEnt and other SDMs have been applied to study intermediate host distribution (Scholte et al, 2012;Stensgaard et al, 2013;Pedersen et al, 2014). MaxEnt's principle for estimating the distribution of the species is through finding maximum entropy for distribution (the distribution closest to uniform) with the constraints that the expected value of each variable constraint matches its empirical average.…”

“…NDVI and day temperatures values were also found to govern B. pfeifferi and B. sudanica distribution and S. mansoni transmission in Uganda (Stensgaard et al, 2005). Moreover, Pedersen et al (2014) showed that temperature play an important role in B. pfeifferi potential distribution in Zimbabwe and indicated that climate change may significantly alter the future spatial distribution of this snail species. Also, NDVI and maximum temperature were important factors determining the spatial distribution of B. pfeifferi in Ethiopia .…”

“…Different spatial modelling techniques have been used to model Biomphalaria distribution such as maximum entropy (MaxEnt) (Scholte et al, 2012;Stensgaard et al, 2013;Pedersen et al, 2014), genetic algorithm for rule-set prediction (GARP) (Stensgaard et al, 2006), and geostatic indicator Kriging (Guimarães et al, 2009). There are also non-regression models such as the Bayesian geostatistical approach for modelling Biomphalaria spp., distribution (Raso et al, 2005;Vounatsou et al, 2009;Standley et al, 2012;Schur et al, 2013).…”

The spatial and seasonal distribution of Bulinus truncatus, Bulinus forskalii and Biomphalaria pfeifferi, the intermediate host snails of schistosomiasis, in N’Djamena, Chad

“…S. bovis poses a considerable veterinary public health problem, since it is the key species infecting livestock (Moné et al, 1999). To assess local transmission of these parasites, an appraisal of intermediate host snail distribution, climatic suitability and human water contact patterns are essential (Brooker, 2002;Pedersen et al, 2014).…”

Canine angiostrongylosis: recent advances in diagnosis, prevention, and treatment

“…Climate changes have the potential to foster the distribution of a variety of intermediate and paratenic hosts and consequent modification of vector phenology, including gastropods. 13,[33][34][35][36] As a key example, the increasing number of recent reports of mollusk-transmitted parasitoses has been suggested to result from the geographic spread of slugs and snails. 14,[37][38][39][40][41] Indeed, population dynamics and activity of different intermediate hosts, including mollusks, are sensitive to temperature and moisture, and the development of nematode larvae in invertebrates is also known to be temperature dependent.…”