Preliminary assessment of the genetic population structure of the enigmatic species Laonastes aenigmamus (Rodentia: Diatomyidae)

Described in 2005, Laonastes aenigmamus is the only species of Diatomyidae. The known distribution of this rodent encompasses only the rugged mountains of the Khammouan karst in central Lao People's Democratic Republic. We used a sample of 52 specimens to survey population structure by sequencing 887 base pairs of the cytochrome-b gene. The overall haplotype diversity was low (0.789 ± 0.039 SD), with 14 haplotypes identified, whereas the nucleotide diversity was high (0.015 ± 0.008 SD). Phylogenetic and haplotypic network reconstructions revealed 3 well-supported and rather divergent lineages with mutational steps ranging from 28 to 32. Identified haplotype groups correspond to localities, suggesting that populations of L. aenigmamus are geographically structured. Mismatch distributions suggest population stability. An exact test for population differentiation confirms a significant level of differentiation. Taking into account human pressure increasingly threatening this ecosystem, we provide preliminary insights on the genetically discrete population structure of this enigmatic mammal species. © American 2011 Society of Mammalogists

Preliminary assessment of the genetic population structure of the enigmatic species Laonastes aenigmamus (Rodentia : Diatomyidae)

peer reviewedDescribed in 2005, Laonastes aenigmamus is the only species of Diatomyidae. The known distribution of this rodent encompasses only the rugged mountains of the Khammouan karst in central Lao People's Democratic Republic. We used a sample of 52 specimens to survey population structure by sequencing 887 base pairs of the cytochrome-b gene. The overall haplotype diversity was low (0.789 ± 0.039 SD), with 14 haplotypes identified, whereas the nucleotide diversity was high (0.015 ± 0.008 SD). Phylogenetic and haplotypic network reconstructions revealed 3 well-supported and rather divergent lineages with mutational steps ranging from 28 to 32. Identified haplotype groups correspond to localities, suggesting that populations of L. aenigmamus are geographically structured. Mismatch distributions suggest population stability. An exact test for population differentiation confirms a significant level of differentiation. Taking into account human pressure increasingly threatening this ecosystem, we provide preliminary insights on the genetically discrete population structure of this enigmatic mammal species. © American 2011 Society of Mammalogists

Molecular demonstration of Trypanosoma evansi and Trypanosoma lewisi DNA in wild rodents from Cambodia, Lao PDR and Thailand

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. (Résumé d'auteur

Helminth communities in murid rodents from southern and northern localities in Lao PDR: the role of habitat and season

International audienceThe helminth communities of wild murid rodents were investigated in Luang Prabang and Champasak province, Lao PDR. Thirteen species of rodents (404 individuals) were infected by 19 species of parasites (2 trematode, 3 cestode, 14 nematode species). Four of the recorded helminth species (Echinostoma malayanum, Raillietina sp., Hymenolepis diminuta and H. nana) are known to cause potential zoonotic helminthiases of medical importance in the South-East Asian region. Individual helminth infection was significantly higher in the wet season. Habitat significantly influenced individual helminth species richness and individual helminth abudance, with a decrease of individual helminth species richness and individual helminth abundance from forest habitat to agricultural and human settlement habitats. The reduction of helminth diversity and abundance is discussed in relation to the ongoing increase of human influence on habitats in Lao PDR

Rodent-borne hantaviruses in Cambodia, Lao PDR and Thailand

In order to evaluate the circulation of hantaviruses present in southeast Asia, a large scale survey of small mammal species was carried out at seven main sites in the region (Cambodia, Lao People's Democratic Republic, and Thailand). Small scale opportunistic trapping was also performed at an eighth site (Cambodia). Using a standard IFA test, IgG antibodies reacting to Hantaan virus antigens were detected at six sites. Antibody prevalence at each site varied from 0 to 5.6% with antibodies detected in several rodent species (Bandicota indica, B. savilei, Maxomys surifer, Mus caroli, M. cookii, Rattus exulans, R. nitidius, R. norvegicus, and R. tanezumi). When site seroprevalence was compared with site species richness, seropositive animals were found more frequently at sites with lower species richness. In order to confirm which hantavirus species were present, a subset of samples was also subjected to RT-PCR. Hantaviral RNA was detected at a single site from each country. Sequencing confirmed the presence of two hantavirus species, Thailand and Seoul viruses, including one sample (from Lao PDR) representing a highly divergent strain of Seoul virus. This is the first molecular evidence of hantavirus in Lao PDR and the first reported L segment sequence data for Thailand virus. (Résumé d'auteur