Abstract: BACKGROUND: Predicting habitats prone to favor disease transmission is challenging due to confounding information on habitats, reservoirs, and diseases. Comparative analysis, which aims at investigating ecological and evolutionary patterns among species, is a tool that may help. The emergence of zoonotic pathogens is a major health concern and is closely linked to habitat modifications by human activities. Risk assessment requires a better knowledge of the interactions between hosts, parasites, and the landscape. METHODS: We used information from a field spatial study that investigated the distribution of murid rodents, in various habitats of three countries in Southeast Asia, in combination with their status of infection by 10 taxa of microparasites obtained from the literature. Microparasite species richness was calculated by rodent species on 20,272 rodents of 13 species. Regression tree models and generalized linear models were used to explain microparasite diversity by the average distance between the trapping site and five categories of land cover: forest, steep agriculture land, flat agriculture land, water, and built-up surfaces. Another variable taken into account was the slope. RESULTS: We found that microparasite diversity was positively associated with flat agriculture land, in this context mainly rice fields, and negatively associated with slope. Microparasite diversity decreased sharply a 100 m or less from flat agriculture land. CONCLUSION: We conclude that there is high microparasite circulation in rodents of flooded farmlands, meaning possibly a higher risk of disease for human inhabitants. Key words: comparative analysis; landscape; rodent-borne diseases; transmission ecology DOI: 10.3402/iee.v3i0.20178 |
Abstract: In this study, we investigated the molecular evidence of Trypanosoma evansi in wild rodents from Cambodia, Lao PDR and Thailand. Between November 2007 and June 2009, 1664 rodents were trapped at eight sites representative of various ecological habitats. Of those animals, 94 were tested by direct microscopic blood examination, 633 using the Card Agglutination Test for Trypanosomes (CATT/T. evansi ) and 145 by Polymerase Chain Reaction (PCR) with two sets of primers: TRYP1 (amplifying ITS1 of ribosomal DNA of all trypanosomes) and TBR (amplifying satellite genomic DNA of Trypanozoon parasites). Using TRYP1, based on the size of the PCR products, 15 samples from the three countries were positive for Trypanosoma lewisi (two were confirmed by sequencing), and three were positive for Trypanozoon (one was confirmed by sequencing and three by TBR primers); the specificity of the primers failed as rodent DNA was amplified in some cases. Using TBR, six samples were positive for Trypanozoon (one was confirmed by sequencing); as T. evansi is the only species of the Trypanozoon sub-genus possibly present in Asian rodents, these results confirmed its presence in rodents from Thailand (Rattus tanezumi ) and Cambodia (R. tanezumi , Niviventer fulvescens & Maxomys surifer ). Further investigations are necessary to establish the situation in Lao PDR. None of the 16 samples most strongly positive to the CATT proved to be positive for Trypanozoon by PCR. The merits of the CATT for such studies were not confirmed. Studying the urban and rural circulation of these parasites in rodents will enable an evaluation of human exposure and infection risk, as human infections by T. evansi were recently described in India and by T. lewisi in India and Thailand. As sequencing PCR products is expensive, the development of new molecular and serological tools for rodents would be very useful.
Key words: Trypanosoma evansi , Trypanosoma lewisi, PCR, rodents, Cambodia, Lao PDR, Thailand
DOI: 10.1111/j.1865-1682.2012.01314.x
Abstract: Black rats are major invasive vertebrate pests with severe ecological, economic and health impacts. Remarkably, their evolutionary history has received little attention, and there is no firm agreement on how many species should be recognized within the black rat complex. This species complex is native to India and Southeast Asia. According to current taxonomic classification, there are three taxa living in sympatry in several parts of Thailand, Cambodia and Lao People’s Democratic Republic, where this study was conducted: two accepted species (Rattus tanezumi , Rattus sakeratensis ) and an additional mitochondrial lineage of unclear taxonomic status referred to here as ‘Rattus R3’. We used extensive sampling, morphological data and diverse genetic markers differing in rates of evolution and parental inheritance (two mitochondrial DNA genes, one nuclear gene and eight microsatellite loci) to assess the reproductive isolation of these three taxa. Two close Asian relatives, Rattus argentiventer and Rattus exulans , were also included in the genetic analyses. Genetic analyses revealed discordance between the mitochondrial and nuclear data. Mitochondrial phylogeny studies identified three reciprocally monophyletic clades in the black rat complex. However, studies of the phylogeny of the nuclear exon interphotoreceptor retinoid-binding protein gene and clustering and assignation analyses with eight microsatellites failed to separate R. tanezumi and R3. Morphometric analyses were consistent with nuclear data. The incongruence between mitochondrial and nuclear (and morphological) data rendered R. tanezumi /R3 paraphyletic for mitochondrial lineages with respect to R. sak- eratensis . Various evolutionary processes, such as shared ancestral polymorphism and incomplete lineage sorting or hybridization with massive mitochondrial introgression between species, may account for this unusual genetic pattern in mammals.
Key words : incomplete lineage sorting, introgression, paraphyly, Rattus , recent speciation, species complex
DOI: 10.1111/mec.12149
Abstract: The helminth communities of wild murid rodents wereinvestigated in Luang Prabang and Champasak province, Lao PDR. Thirteen speciesof rodents (404 individuals) were infected by 19 species of parasites (2trematode, 3 cestode, 14 nematode species). Four of the recorded helminthspecies (Echinostoma malayanum , Raillietina sp., Hymenolepis diminuta and H.nana ) are known to cause potential zoonotic helminthiases of medicalimportance in the South-East Asian region. Individual helminth infection wassignificantly higher in the wet season. Habitat significantly influencedindividual helminth species richness and individual helminth abudance, with adecrease of individual helminth species richness and individual helminthabundance from forest habitat to agricultural and human settlement habitats.The reduction of helminth diversity and abundance is discussed in relation tothe ongoing increase of human influence on habitats in Lao PDR.
Key words: helminths, parasite species richness, murid rodents, habitat, anthropization, Lao PDR
DOI: 10.1017/S0022149X13000187
Abstract – During a study of the helminth fauna of 1,643 rodents trapped along the Mekong River (Thailand, Lao People’s Democratic Republic and Cambodia) in 2008–2011, the spirurid nematode Physaloptera ngoci Le-Van-Hoa,1961 was recovered with an overall prevalence of 2.8%. Based on the original description, it was identified in nine of 23 different Murinae host species and is here reported for the first time from these three countries. A scanning electron microscopy study provides additional morphological data.
Key words: Helminths / Physaloptera ngoci / Rodents / Thailand / Lao People’s Democratic Republic / Cambodia.
DOI http://dx.doi.org/10.1051/parasite/2013023
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