Vkorc1 gene polymorphisms confer resistance to anticoagulant rodenticide in Turkish rats

Mutations in Exon 1, 2 and 3 of the vitamin K epoxide reductase complex subunit 1 (Vkorc1) gene are known to lead to anticoagulant rodenticide resistance. In order to investigate their putative resistance in rodenticides, we studied the genetic profile of the Vkorc1 gene in Turkish black rats (Rattus rattus) and brown rats (Rattus norvegicus). In this context, previously recorded Ala21Thr mutation (R. rattus) in Exon 1 region, Ile90Leu mutation (R. rattus, R. norvegicus) in Exon 2 region and Leu120Gln mutation (R. norvegicus) in Exon 3 region were identified as "missense mutations" causing amino acid changes. Ala21Thr mutation was first detected in one specimen of Turkish black rat despite the uncertainty of its relevance to resistance. Ile90Leu mutation accepted as neutral variant was detected in most of black rat specimens. Leu120Gln mutation related to anticoagulant rodenticide resistance was found in only one brown rat specimen. Furthermore, Ser74Asn, Gln77Pro (black rat) and Ser79Pro (brown rat) mutations that cause amino acid changes in the Exon 2 region but unclear whether they cause resistance were identified. In addition, "silent mutations" which do not cause amino acid changes were also defined; these mutations were Arg12Arg mutation in Exon 1 region, His68His, Ser81Ser, Ile82Ile and Leu94Leu mutations in Exon 2 region and Ile107Ile, Thr137Thr, Ala143Ala and Gln152Gln mutations in Exon 3 region. These silent mutations were found in both species except for Ser81Ser which was determined in only brown rats.

Morphological and molecular description of Sarcocystis ratti n. sp. from the black rat (Rattus rattus) in Latvia

Rodents have been widely studied as intermediate hosts of Sarcocystis; however, only a few reports on these parasites in the black rat (Rattus rattus) are known. Having examined 13 black rats captured in Latvia, sarcocysts were found in skeletal muscles of two mammals and were described as Sarcocystis ratti n. sp. Under a light microscope, sarcocysts were ribbon-shaped, 0.9-1.3 × 0.09-0.14 mm in size and had a thin (0.8-1.3 μm) and smooth cyst wall. The lancet-shaped bradyzoites were 8.3 × 4.3 (7.5-9.3 × 3.9-4.8) μm. Under a transmission electron microscope, the cyst wall was up to 1.3 μm thick, wavy, the ground substance appeared smooth, type 1a-like. Morphologically, sarcocysts of S. ratti were somewhat similar to those of S. cymruensis, S. rodentifelis, and S. dispersa-like previously identified in the brown rat (Rattus norvegicus). On the basis of 18S rDNA, 28S rDNA, and cox1, significant genetic differences (at least 2.3, 4.5, and 5.8%, respectively) were observed when comparing S. ratti with other Sarcocystis species using rodents as intermediate hosts. While ITS1 sequences of S. ratti were highly distinct from other Sarcocystis species available in GenBank. Phylogenetic and ecological data suggest that predatory mammals living near households are definitive hosts of S. ratti.

Patterns of helminth infections in Rattus rattus and Mus musculus from two Mayan communities in Mexico

The black rat Rattus rattus and the house mouse Mus musculus are two commensal rodent species that harbour and shed zoonotic pathogens, including helminths. The aim of this survey was to study the helminth community and the patterns of infections in R. rattus and M. musculus from two Mayan communities in Mexico. Gastrointestinal helminths were isolated from 322 M. musculus and 124 R. rattus, including Gongylonema neoplasticum, Hassalstrongylus aduncus, Hassalstrongylus musculi, Hydatigera taeniaeformis metacestode, Hymenolepis diminuta, Nippostrongylus brasiliensis, Oligacanthorhynchidae gen. sp., Syphacia muris, Syphacia obvelata, Rodentolepis microstoma and Trichuris muris. The overall richness of helminths was seven in R. rattus and six in M. musculus. The results of generalized linear models showed that juvenile rodents had lower probabilities of being infected with G. neoplasticum, H. taeniaeformis and H. musculi than adult rodents. A positive association between the prevalence of S. muris and rat abundance was found. The intensity of infection with S. muris was higher in the rainy season than in the dry season; the opposite result was found for H. musculi infection. Male R. rattus harboured more S. muris specimens. The intensity of infection with T. muris was inversely associated with mouse abundance. The presence of the zoonotic H. diminuta, as well as H. taeniaeformis and R. microstoma in rodent populations indicates that there is risk of transmission, and that their entire life cycle occurs in the study area.

Detection of rat hepatitis E virus in wild Norway rats (Rattus norvegicus) and Black rats (Rattus rattus) from 11 European countries

Rat hepatitis E virus (HEV) is genetically only distantly related to hepeviruses found in other mammalian reservoirs and in humans. It was initially detected in Norway rats (Rattus norvegicus) from Germany, and subsequently in rats from Vietnam, the USA, Indonesia, China, Denmark and France. Here, we report on a molecular survey of Norway rats and Black rats (Rattus rattus) from 12 European countries for ratHEV and human pathogenic hepeviruses. RatHEV-specific real-time and conventional RT-PCR investigations revealed the presence of ratHEV in 63 of 508 (12.4%) rats at the majority of sites in 11 of 12 countries. In contrast, a real-time RT-PCR specific for human pathogenic HEV genotypes 1-4 and a nested broad-spectrum (NBS) RT-PCR with subsequent sequence determination did not detect any infections with these genotypes. Only in a single Norway rat from Belgium a rabbit HEV-like genotype 3 sequence was detected. Phylogenetic analysis indicated a clustering of all other novel Norway and Black rat-derived sequences with ratHEV sequences from Europe, the USA and a Black rat-derived sequence from Indonesia within the proposed ratHEV genotype 1. No difference in infection status was detected related to age, sex, rat species or density of human settlements and zoological gardens. In conclusion, our investigation shows a broad geographical distribution of ratHEV in Norway and Black rats from Europe and its presence in all settlement types investigated.

Emergence of Wesselsbron virus among black rat and humans in Eastern Senegal in 2013

Wesselsbron disease is a neglected mosquito transmitted Flavivirus infection that causes abortions and has teratogenic effects on sheep and cattle in Africa. Human can also be infected. The detection of human or animal cases is complicated by the non-specific symptoms close to Rift Valley Fever (RVF) in domestic livestock species or Dengue like syndrome in humans. Then, these detections are usually made during RVF investigations in sheep. These domestic animals should take a role in the life cycle of the virus but some evidences of Wesselsbron virus (WSLV) presence in wild animals suggest that the latter may be involved in the virus maintenance in nature. However, the reservoir status of wild vertebrate in general and rodents particularly for WSLV is only based on an isolation from a Cape short-eared gerbil in southern Africa. Most of WSLV isolations are from southern parts of Africa even if it has been found in western and central Africa or Madagascar. In Senegal, there are serological evidences of WSLV circulation in human since the 1970s and some isolations, the last one of which dates back in 1992. Despite the detection of the virus on mosquitoes until the 2000s in different parts of the country, no new human case has been noted. In this paper, we report the WSLV re-emergence in eastern Senegal in 2013 with 2 human cases and its first isolation from a black rat Rattus rattus. Sequencing analyses show the circulation of the same strain between these humans and the commensal rodent. The putative impact on WSLV transmission to human populations could be more important if the reservoir status of the black rat is confirmed. Focused survey in human populations, specific entomological and mammalogical investigations would permit a better understanding of the life cycle of the virus and its impact on public health.

Tooth wear patterns in black rats (Rattus rattus) of Madagascar differ more in relation to human impact than to differences in natural habitats

Dietary characteristics and environmental variables are important selective factors directing ecological diversification in rodents. On Madagascar, the introductions and spread of the commensal black rat (Rattus rattus) can be seen as example cases to study dietary niche occupation and dietary adaptation in an insular environment. We investigate how tooth wear as a measure of dietary adaptation of black rats differs between four distinct habitats (village, manioc fields, spiny forest, and rainforest) with different dietary resources. We use the 3D surface texture analysis (3DST, using 30 parameters according to ISO 25178) as a measure of dietary abrasiveness. 3DST is applied on the occlusal surface of the upper first molar of 37 black rat specimens. The rainforest sample displays less rough and less voluminous surface textures compared to the village samples as indicated by smaller values for height parameters (Sa, Sp, Sq), inverse areal material ratio (Smc), and volume parameters (Vm, Vmc, Vmp, Vv, and Vvc). We therefore rank sampling areas from highest to lowest abrasiveness (village>manioc fields/spiny forest>rainforest). The rats from villages and rainforest differ to such an extent that one could have interpreted them to belong to different species. This indicates a high degree of variability in terms of ingesta abrasiveness. Furthermore, the pronounced difference between rats from human habitations compared to rats from associated fields or natural vegetation is interpreted to clearly indicate shifts in dietary niche occupation in relation to human impact.

Capillaria hepatica in wild Norway rats (Rattus norvegicus) from Vancouver, Canada

Capillaria hepatica is a parasitic nematode that infects the liver of rats (Rattus spp.), and occasionally other mammalian species, including humans. Despite its broad geographic distribution and host range, the ecology of this parasite remains poorly understood. We characterized the ecology of C. hepatica in urban Norway rats (Rattus norvegicus) in Vancouver, Canada. The overall prevalence of C. hepatica among Norway rats was 36% (241/671); however, there was significant variation in prevalence among city blocks. Using a generalized linear mixed model to control for clustering by block (where OR is odds ratio and CI is confidence interval), we found C. hepatica infection was negatively associated with season (spring [OR=0.14, 95% CI=0.05-0.39]; summer [OR=0.14, 95% CI=0.03-0.61]; winter [OR=0.34, 95% CI=0.13-0.84], compared to fall) and positively associated with sexual maturity (OR: 7.29, 95% CI=3.98-13.36) and presence of cutaneous bite wounds (OR=1.87, 95% CI=1.11-3.16). Our understanding of the ecology of C. hepatica in rats is hindered by a paucity of data regarding the main mechanisms of transmission (e.g., environmental exposure vs. active cannibalism). However, associations among infection, season, maturity, and bite wounds could suggest that social interactions, possibly including cannibalism, may be important in transmission.

Epidemiology of Leishmania infantum, Toxoplasma gondii, and Neospora caninum in Rattus rattus in absence of domestic reservoir and definitive hosts

Isolated environments are privileged settings to study transmission of infection. Montecristo is a small island where no wild or domestic carnivores are present. Invasive Black rats Rattus rattus (n=78) were captured and tested by PCR for Leishmania infantum, Toxoplasma gondii and Neospora caninum. We wanted to test, for these parasites, the existence of a sylvatic cycle independent of reservoir or definitive hosts. None of the rats tested positive by PCR for either T. gondii or N. caninum. We recorded a 15.5% prevalence (CI95% 8-26%) of L. infantum in the rats and Phlebotomus mascittii was captured in Montecristo, leading us to identify it as possible vector of the parasite.