BackgroundThe freshwater snail Indoplanorbis exustus is found across India, Southeast Asia, central Asia (Afghanistan), Arabia and Africa. Indoplanorbis is of economic importance in that it is responsible for the transmission of several species of the genus Schistosoma which infect cattle and cause reduced livestock productivity. The snail is also of medical importance as a source of cercarial dermatitis among rural workers, particularly in India. In spite of its long history and wide geographical range, it is thought that Indoplanorbis includes only a single species. The aims of the present study were to date the radiation of Indoplanorbis across Asia so that the factors involved in its dispersal in the region could be tested, to reveal potential historical biogeographical events shaping the phylogeny of the snail, and to look for signs that I. exustus might be polyphyletic.ResultsThe results indicated a radiation beginning in the late Miocene with a divergence of an ancestral bulinine lineage into Assam and peninsular India clades. A Southeast Asian clade diverged from the peninsular India clade late-Pliocene; this clade then radiated at a much more rapid pace to colonize all of the sampled range of Indoplanorbis in the mid-Pleistocene.ConclusionsThe phylogenetic depth of divergences between the Indian clades and Southeast Asian clades, together with habitat and parasitological differences suggest that I. exustus may comprise more than one species. The timescale estimated for the radiation suggests that the dispersal to Arabia and to Southeast Asia was facilitated by palaeogeographical events and climate change, and did not require human involvement. Further samples from Afghanistan, Africa and western India are required to refine the phylogeographical hypothesis and to include the African Recent dispersal.

Partial (DNA) sequences were collected for 2 mitochondrial loci (Srrna and Lrrna, the rrnS and rrnL rRNA genes respectively) for Schistosoma indicum group species from 4 Southeast Asian countries. The samples included 7 populations, 4 of which were previously unstudied. In 11 cases the combination of locus and population was new. The aim of the study was to provide a phylogeny based on new independent data and multiple populations (earlier studies had mostly used a common set of field samples or laboratory lines) and to examine interrelationships and phylogeography within this species group. Paraphyly of the S. indicum group was confirmed, as was the basal position of Schistosoma incognitum in the Schistosoma phylogeny. Southeast Asian Schistosoma spindale and S. incognitum populations were shown to fall into their respective con-specific cohesive groupings. Estimated divergence times for these taxa were shown to be related to Pleistocene changes in sea level and the radiation of definitive host groups. A revised phylogeographical model is proposed in the light of these findings.

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To determine the prevalence of ectoparasitic infestation of cattle in and around the Bhawal forest area in Gazipur district in Bangladesh, an epidemiological investigation was carried out during the period from November 2008 to October 2009. Of 206 cattle examined, 132 (64.07%) were found to be infested with several species of ticks and lice. The prevalence rate was highest in case of Boophilus microplus (45.63%) followed by Rhipicephalus sanguineus (36.89%), Linognathus vituli ((23.30%), Haematopinus euysternus (17.96%), Hemaphysalis bispinosa (16.50%), and Damalinia bovis (8.25%). Results revealed that, older cattle aged > 8 years are more (71.11%) susceptible than that of adults aged > 2-8 years (67.74%), and young aged ≤2 years (47.05%). In females, prevalence of ectoparasitic infestation was observed significantly (p< 0.005) higher than that of male. Prevalence of ectoparasitic infestation was significantly (p<0.005) higher in animal reared under free range system than that of semi-intensive system and cattle with malnourished and poor health status were found to be significantly more vulnerable to such parasitic infestation than normal healthy cattle. Seasonal prevalence showed that, significantly (p<0.001) higher prevalence occurred in summer season (78.46%), followed by winter (62.85%) and rainy season (52.11%). Mean parasitic burden were 1.49±0.80 per square inches of heavily infected area.

To study the distribution, host-preference and population density of ixodid ticks in Bangladesh, an attempt was made to collect adult ticks from various host animals in three distinct topographic zones, viz. flood plains, hills and steppe 'Barind'. Five species of ixodid ticks were recorded, namely, Boophilus microplus (56.3%), Haemaphysalis bispinosa (11.3%), Rhipicephalus sanguineus (14.7%), Hyalomma anatolicum anatolicum (15.0%) and Amblyomma testudinarium (2.8%). The data showed that B. microplus occurred predominantly on cattle (42.4%). The other hosts involved were buffaloes (12.5%), goats (25.5%) and pigs (8.2%). H. bispinosa mostly parasitized goats (31.5%) rather than cattle (12.0%) and buffaloes (10.8%). R. sanguineus was principally a dog tick (27.4%) but also parasitized cattle (10.8%) and goats (6.8%). H. a. anatolicum was restricted to cattle (19.2%) and A. testudinarium was found on both cattle (4.4%) and pigs (2.3%). These results indicate that ixodid ticks are not strictly host-specific except for H. a. anatolicum. The population density of these ticks was significantly (p < 0.01) influenced by the changing of seasons. B. microplus, H. bispinosa and R. sanguineus were by far the most widely distributed species; the distribution of H. a. anatolicum was restricted to the steppe 'Barind tract' and A. testudinarium was found in the hilly regions only.