Abstract: 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.
Key words: hantavirus, southeast Asia, rodents, serology, phylogeny, seoul virus variant
DOI: 10.1007/s10393-011-0725-7
Abstract: Parasite species loads are expected to be higher in the tropics and higher parasite species richness to have cumulative effects on host physiology or demography. Despite being regularly assumed or predicted, empirical evidence on species-latitude patterns is scarce or contradictory and studies on the impacts of concomitant infections have mainly been done at host intra-specific level. Broad generalizations are then very hard, if not spurious.
By focusing on rodent species and their non-eukaryotic microparasites (i.e. viruses and bacteria), we investigated, using a comparative approach, microparasite species richness across rodent species according to the latitude where they occur. We also explored the links between rodents' reproductive traits, latitude and microparasite species richness.
We find for the first time in rodents that virus species richness increases towards tropical latitudes, and that rodent litter size seems to decrease when microparasite species richness increases independently from the latitude. These results support the hypotheses that rodent species in the tropics effectively harbour higher parasite species loads, at least in terms of species richness for viruses, and that parasite species richness influences rodent life-history traits. Although some other factors, such as seasonality, were not taken into account due the lack of data, our study stresses the idea that chronic microparasite infections may have detrimental effects on their rodent host reservoirs, notably by affecting litter size.
Keywords: microparasite species richness, virus, bacteria, rodents, latitude, life-traits, litter size, comparative analysis.
DOI: 10.1111/j.1600-0706.2011.19314.x
Abstract: Field parasitological studies consistently demonstrate the reality of polyparasitism in natural systems. However, only recently, studies from ecological and evolutionary fields have emphasised a broad spectrum of potential multiple infections-related impacts. The main goal of our review is to reunify the different approaches on the impacts of polyparasitism, not only from laboratory or human medical studies but also from field or theoretical studies. We put forward that ecological and epidemiological determinants to explain the level of polyparasitism, which regularly affects not only host body condition, survival or reproduction but also host metabolism, genetics or immune investment. Despite inherent limitations of all these studies, multiple infections should be considered more systematically in wildlife to better appreciate the importance of parasite diversity in wildlife, cumulative effects of parasitism on the ecology and evolution of their hosts.
Keywords: Wildlife, polyparasitism, multiparasitism, coinfections, parasite diversity, life-history traits.
DOI: 10.3402/iee.v1i0.7346
Abstract: Species richness of parasite assemblages varies among host species. Earlier studies that searched for host-related determinants of parasite diversity mainly considered host traits that affect the probability of host encounter with parasites, whereas host traits related to defensibility against parasites have rarely been investigated. From the latter perspective, evolutionary investment in “expensive” tissue or organs (like testes or brain) may trade off against energetically costly anti-parasitic defences. If so, richer parasite assemblages are expected in hosts with larger testes and brains. We studied the relationships between testes and brain size and diversity of parasites (fleas, gamasid mites and helminths) in 55 rodent species using a comparative approach and application of two methods, namely the method of independent contrasts and generalized least-squares (GLS) analysis. Both phylogenetically correct methods produced similar results for flea and helminth species richness. Testes size positively correlated with flea and helminth species richness but not gamasid mite species richness. No correlation between brain size and species richness of any parasite group was found by the method of independent contrasts. However, GLS analysis indicated negative correlation between brain size and mite species richness. Our results cast doubt on the validity of the expensive tissue hypothesis, but suggest instead that larger testes are associated with higher parasite diversity via their effect on mobility and/or testosterone-mediated immunosuppression.
Keywords: Expensive tissue hypothesis, Brain, Parasites, Rodents, Species richness.
DOI: 10.1007/s00442-010-1743-9
Abstract:
At the end of the 20th century the unique taxonomically enigmatic entity called Pneumocystis carinii
was identified as a heterogeneous group of microscopic Fungi, constituted of multiple stenoxenic biological entities largely spread across ecosystems, closely adapted to, and coevolving in parallel with, mammal species. The discoveries and reasoning that led to the current conceptions about the taxonomy of Pneumocystis
at the species level are examined here. The present review also focuses on the biological, morphological and phylogenetical features of Pneumocystis jirovecii, Pneumocystis oryctolagi, Pneumocystis murina, P. carinii
and Pneumocystis wakefieldiae
, the five Pneumocystis
species described until now, mainly on the basis of the phylogenetic species concept. Interestingly, Pneumocystis
organisms exhibit a successful adaptation enabling them to dwell and replicate in the lungs of both immunocompromised and healthy mammals, which can act as infection reservoirs. The role of healthy carriers in aerial disease transmission is nowadays recognized as a major contribution to Pneumocystis
circulation, and Pneumocystis infection of nonimmunosuppressed
hosts has emerged as a public health issue. More studies need to be undertaken both on the clinical consequences of the presence of Pneumocystis
in healthy carriers and on the intricate Pneumocystis
life cycle to better define its epidemio-logy, to adapt existing therapies to each clinical context and to discover new drug targets.
Key words: Pneumocystis spp.; phylogenetic species concept; life cycle; epidemiology.
DOI: 10.1111/j.1567-1364.2010.00698.x
Abstract: Notocotylus loeiensis n. sp. (Trematoda: Notocotylidae) is described from the cecum of the lesser rice field rat (Rattus losea ), from Loei Province in Thailand with a prevalence of 9.1 % (eight of 88 rats infected). The new species differs from previously described Notocotylus species mainly by the extreme prebifurcal position of the genital pore and the number of ventral papillae. This is the first description at the species level of Notocotylus from mammals in Southeast Asia.
Keywords: Notocotylus , Trematoda, Digenea, Notocotylidae, Rattus losea , lesser rice field rat, Thailand
Accession number: ISI:000289396100004
Abstract: Trypanosoma lewisi is a mild or non-pathogenic parasite of the sub-genus Herpetosoma transmitted by fleas to rats. In a previous study we described pan-trypanosome specific primers TRYP1 which amplify the ITS1 of ribosomal DNA by hybridizing in highly conserved regions of 18S and 5.8S genes. These primers proved to be useful for detecting T. lewisi DNA in laboratory rats, but a recent large scale survey in wild rodents demonstrated a lack of specificity. In the present study, we designed and evaluated mono-specific primers LEW1S and LEW1R, for the detection and identification of T. lewisi by a single-step PCR. These primers were designed inside the highly variable region of the ITS1 sequence of T. lewisi ribosomal DNA. The product size of 220 bp is specific to T. lewisi . The sensitivity limit was estimated between 0.055 and 0.55 pg of DNA per reaction, equivalent to 1–10 organisms per reaction. All the PCR products obtained from 6 different T. lewisi isolates were more than 98% similar with each other and similar to the sequences of T. lewisi already published in Genbank. All DNA of 7 T. lewisi stocks from China gave the specific 220 bp product. We showed that LEW1S and LEW1R primers enabled sensitive detection and identification of T. lewisi infection in laboratory and wild rats. This assay is recommended for monitoring T. lewisi infections in rat colonies or for studying infections in the wild fauna. An absence of cross reaction with human DNA means that these primers can be used to investigate atypical trypanosome infections in humans. Given the risk of T. lewisi infection in human, we believe that these primers will be beneficial for public health diagnosis and rodents investigation programmes.
Key words: Trypanosoma lewisi ; PCR; ITS1; Ribosomal DNA; Primers; Rattus sp.
DOI: 10.1016/j.meegid.2011.04.030
Abstract:
Domestic and wild rodents known as the most abundant and diversified order of mammals have a key role in the ecological food chain and also in the transmission of parasites and pathogens to other animals. While foraging on the ground, they can get infected by Toxoplasma gondii, a protozoan parasite, which is the causative agent of toxoplasmosis. Therefore, they serve as intermediate hosts of T. gondii and can transmit it to their predators. To assess their role in the maintenance of T. gondii lifecycle in Thailand, we sampled rodents in a range of biotopes representative of the high biodiversity and conducted a serological survey with latex agglutination
test to detect anti-T. gondii antibodies. Overall, 21 of 461 (4.6%) rodents had diagnostically significant antibody titers (cutoff, 1:64). Every species with at least 37 individuals captured tested positive, confirming the wide range of potential mammalian hosts of toxoplasmosis. None of the ecological traits (sex, maturity, morphology,
season, or habitat) was found significant to predict the susceptibility to T. gondii both univariately and in a multivariate analysis. However, high prevalences were reported in either forested or anthropized areas. This survey constitutes the first confirmed serological investigation of T. gondii in rodents in Thailand. The rarity of both domestic and wild felids in Thailand emphasizes the importance of rodents in maintaining T. gondii, and questions the involvement of other carnivores in the life cycle.
Key words: Ecology, Murinae, Rattus, Rodent, T. gondii , Toxoplasmosis.
DOI: 10.1089/vbz.2009.0238
Abstract: Leopoldamys neilli is a threatened murine rodent species endemic to limestone karsts of Thailand. We have studied the phylogeography of L. neilli using two mitochondrial markers (cytb, COI) and one nuclear fragment (bfibr), in order to assess the influence of its endemicity to karst habitat. One hundred fifteen individuals of L. neilli were collected in 20 localities throughout the geographic range of this species in Thailand. Our study revealed strong geographic structure of the mtDNA genetic diversity: six highly differentiated, allopatric genetic lineages were observed in our dataset. They exhibit a very high degree of genetic divergence, low gene flow among lineages and low levels of haplotype and nucleotide diversities within lineages. Our results suggest that L. neilli ’s populations are highly fragmented due to the scattered distribution of its karst habitat. The most divergent lineage includes the populations from western Thailand, which have been separated from the other genetic lineages since at least the Early Pleistocene. The other lineages are more closely related and have diverged since the Middle Pleistocene. This study revealed an unexpected high level of genetic differentiation within L. neilli and highlighted the high endemicity of this species to limestone karsts. Our results enhance the importance of protecting limestone habitats to preserve not only the species but also intraspecific diversity.
Keywords: Southeast Asia, Leopoldamys neilli , Limestone karsts, Conservation, Phylogeography, Intraspecific diversity
DOI: 10.1007/s10592-011-0248-3
Abstract: Leopoldamys neilli is a threatened murine rodent species endemic to limestone karsts of Thailand. Twelve microsatellite loci were identified using the method of microsatellite-enriched libraries. Polymorphism was assessed in samples (N = 62) from four geographically distinct populations in Thailand. Number of alleles per locus ranged from 9 to 15 (average 11.6). Observed and expected heterozygosities varied from 0.28 to 1.0 and from 0.44 to 0.91, respectively. There was no evidence for linkage disequilibrium, however, four loci showed evidence of departure from Hardy–Weinberg equilibrium in one population. Presence of null alleles was not detected in all the 12 loci. These first microsatellites primers developed for L. neilli will provide information on the fine-scale genetic structure of this threatened species and will help in the development of future conservation policies.
Keywords: Leopoldamys neilli , Murine rodent, Microsatellite, Multiplex, Genetic structure, Southeast Asia
DOI: 10.1007/s12686-011-9391-x
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