Wild-caught Rodents Research Articles

Use of a Novel Detection Tool to Survey Orthohantaviruses in Wild-Caught Rodent Populations.

Orthohantaviruses are negative-stranded RNA viruses with trisegmented genomes that can cause severe disease in humans and are carried by several host reservoirs throughout the world. Old World orthohantaviruses are primarily located throughout Europe and Asia, causing hemorrhagic fever with renal syndrome, and New World orthohantaviruses are found in North, Central, and South America, causing hantavirus cardiopulmonary syndrome (HCPS). In the United States, Sin Nombre orthohantavirus (SNV) is the primary cause of HCPS with a fatality rate of ~36%. The primary SNV host reservoir is thought to be the North American deer mouse, Peromyscus maniculatus. However, it has been shown that other species of Peromyscus can carry different orthohantaviruses. Few studies have systemically surveyed which orthohantaviruses may exist in wild-caught rodents or monitored spillover events into additional rodent reservoirs. A method for the rapid detection of orthohantaviruses is needed to screen large collections of rodent samples. Here, we report a pan-orthohantavirus, two-step reverse-transcription quantitative real-time PCR (RT-qPCR) tool designed to detect both Old and New World pathogenic orthohantavirus sequences of the S segment of the genome and validated them using plasmids and authentic viruses. We then performed a screening of wild-caught rodents and identified orthohantaviruses in lung tissue, and we confirmed the findings by Sanger sequencing. Furthermore, we identified new rodent reservoirs that have not been previously reported as orthohantavirus carriers. This novel tool can be used for the efficient and rapid detection of various orthohantaviruses, while uncovering potential new orthohantaviruses and host reservoirs that may otherwise go undetected.

Tracing Transmission of Sin Nombre Virus and Discovery of Infection in Multiple Rodent Species.

Sin Nombre orthohantavirus (SNV), a negative-sense, single-stranded RNA virus that is carried and transmitted by the North American deer mouse Peromyscus maniculatus, can cause infection in humans through inhalation of aerosolized excreta from infected rodents. This infection can lead to hantavirus cardiopulmonary syndrome (HCPS), which has an ∼36% case-fatality rate. We used reverse transcriptase quantitative PCR (RT-qPCR) to confirm SNV infection in a patient and identified SNV in lung tissues in wild-caught rodents from potential sites of exposure. Using viral whole-genome sequencing (WGS), we identified the likely site of transmission and discovered SNV in multiple rodent species not previously known to carry the virus. Here, we report, for the first time, the use of SNV WGS to pinpoint a likely site of human infection and identify SNV simultaneously in multiple rodent species in an area of known host-to-human transmission. These results will impact epidemiology and infection control for hantaviruses by tracing zoonotic transmission and investigating possible novel host reservoirs. IMPORTANCE Orthohantaviruses cause severe disease in humans and can be lethal in up to 40% of cases. Sin Nombre orthohantavirus (SNV) is the main cause of hantavirus disease in North America. In this study, we sequenced SNV from an infected patient and wild-caught rodents to trace the location of infection. We also discovered SNV in rodent species not previously known to carry SNV. These studies demonstrate for the first time the use of virus sequencing to trace the transmission of SNV and describe infection in novel rodent species.

Browning of subcutaneous adipose tissue in wild-caught rodents of Siberia

The physiological role of uncoupling protein 1 in white fat depot is not yet fully understood. Analysis of adipose tissues of animals from natural populations may be an informative addition to the laboratory experiment in the study of this problem. The paper presents the first case of the detection of uncoupling protein 1 in inguinal white fat depot of short-tailed field voles (Microtus agrestis) and Korean field mice (Apodemus peninsulae). The animals were caught in West Sayan in the summer of 2015. Their inguinal fat was of non-typical dark-pink color with the brown colored inclusions, increased content of total protein in comparison with these parameters of laboratory mice. Immunoreactive UCP1 was identified in this white fat pad of about two-thirds of the animals. The interscapular brown fat weight, morphology, biochemical properties were typical. We assumed the inguinal fat with uncoupling protein 1 to be responsible for heating the low limb muscles and triggering their high activity at low summer night temperatures in West Sayan.

Detection of Anaplasma spp. and Bartonella spp. from wild-caught rodents and their ectoparasites in Nakhon Ratchasima Province, Thailand.

The objective of this study was to investigate evidence of emerging anaplasmosis and bartonellosis in rodents from endemic areas of Nakhon Ratchasima, Thailand. Rodent trapping was undertaken in 13 sub-districts of Muang District. The live-capture traps were set up in three locations of selected scrub typhus patient houses for three consecutive nights. Wild-caught rodent whole blood samples and associated ticks and fleas were collected and tested for Anaplasma spp. and Bartonella spp. In addition, heat maps using GIS software were used to determine the density of infection of positive wild-caught rodents. A total of 347 wild-caught rodents of nine species was captured. Rattus rattus (38.6%) was the dominant species. A total of 1,518 Heamaphysalis bandicota ticks and 57 Xenopsylla cheopis fleas was removed. Twenty-two of the 347 tested blood samples (6.3%) were Anaplasma bovis-positive and 121 blood samples and five out of 27 pools of X. cheopis fleas were Bartonella queenslandensis-positive. Of these infected rodents, dual-infections between A. bovis and B. queenslandensis were found in three B. indica rodents. Our results offer new information concerning the infections of A. bovis and B. queenslandensis in both rodents and their ectoparasites collected in high-risk areas of rodent-borne diseases in Thailand.

Isolation and Characterization of Akhmeta Virus from Wild-Caught Rodents (Apodemus spp.) in Georgia.

In 2013, a novel orthopoxvirus was detected in skin lesions of two cattle herders from the Kakheti region of Georgia (country); this virus was named Akhmeta virus. Subsequent investigation of these cases revealed that small mammals in the area had serological evidence of orthopoxvirus infections, suggesting their involvement in the maintenance of these viruses in nature. In October 2015, we began a longitudinal study assessing the natural history of orthopoxviruses in Georgia. As part of this effort, we trapped small mammals near Akhmeta (n = 176) and Gudauri (n = 110). Here, we describe the isolation and molecular characterization of Akhmeta virus from lesion material and pooled heart and lung samples collected from five wood mice (Apodemus uralensis and Apodemus flavicollis) in these two locations. The genomes of Akhmeta virus obtained from rodents group into 2 clades: one clade represented by viruses isolated from A. uralensis samples, and one clade represented by viruses isolated from A. flavicollis samples. These genomes also display several presumptive recombination events for which gene truncation and identity have been examined.IMPORTANCE Akhmeta virus is a unique Orthopoxvirus that was described in 2013 from the country of Georgia. This paper presents the first isolation of this virus from small mammal (Rodentia; Apodemus spp.) samples and the molecular characterization of those isolates. The identification of the virus in small mammals is an essential component to understanding the natural history of this virus and its transmission to human populations and could guide public health interventions in Georgia. Akhmeta virus genomes harbor evidence suggestive of recombination with a variety of other orthopoxviruses; this has implications for the evolution of orthopoxviruses, their ability to infect mammalian hosts, and their ability to adapt to novel host species.

Seroprevalence for the tick-borne relapsing fever spirochete Borrelia turicatae among small and medium sized mammals of Texas.

BackgroundIn low elevation arid regions throughout the southern United States, Borrelia turicatae is the principal agent of tick-borne relapsing fever. However, endemic foci and the vertebrate hosts involved in the ecology of B. turicatae remain undefined. Experimental infection studies suggest that small and medium sized mammals likely maintain B. turicatae in nature, while the tick vector is a long-lived reservoir.Methodology/principal findingsSerum samples from wild caught rodents, raccoons, and wild and domestic canids from 23 counties in Texas were screened for prior exposure to B. turicatae. Serological assays were performed using B. turicatae protein lysates and recombinant Borrelia immunogenic protein A (rBipA), a diagnostic protein that is unique to RF spirochetes and may be a species-specific antigen.Conclusions/significanceSerological responses to B. turicatae were detected from 24 coyotes, one gray fox, two raccoons, and one rodent from six counties in Texas. These studies indicate that wild canids and raccoons were exposed to B. turicatae and are likely involved in the pathogen’s ecology. Additionally, more work should focus on evaluating rodent exposure to B. turicatae and the role of these small mammals in the pathogen’s maintenance in nature.

Potentially zoonotic helminthiases of murid rodents from the Indo-Chinese peninsula: impact of habitat and the risk of human infection.

In this study, we report the potential rodent-borne zoonotic helminths in wild-caught murid rodents from four categorized habitats-forest, nonflooded land, irrigated land, and human settlement in seven localities of Thailand, Cambodia, and Lao PDR. Out of 2478 rodent samples, 735 (29.7%) were infected by at least one of the following zoonotic helminth species: Echinostoma malayanum, Echinostoma ilocanum, Plagiorchis muris, Raillietina spp., Hymenolepis diminuta, Hymenolepis nana, Cyclodontostomum purivisi, and Moniliformis moniliformis. Raillietina spp. showed the highest prevalence (13.8%), followed by H. diminuta (8.6%), H. nana (6.7%), and C. purvisi (1.0%). Habitat affected the intensity of helminth infection in murid rodent hosts. Specific habitats favoring each zoonotic helminth species are discussed in relation to the risk of human infection. Season and host maturity influenced intensity of total zoonotic helminths, but there was no influence of host gender. However, in terms of individual helminth species, female rodents were more infected by E. malayanum, E. ilocanum, and C. purvisi than males. Among the rodent species, Rattus tanezumi seems to play the most important role as a reservoir by hosting seven zoonotic heminth species. This rat is ubiquitously found in all types of the habitats, suggesting that it can act as an important bridge species, carrying parasites across different habitats.

Inflammation in response to phytohemagglutinin injection in the Talas tuco-tuco (Ctenomystalarum): implications for the estimation of immunocompetence in natural populations of wild rodents

The immunological variation in wild populations and its relation to life-history traits has recently become a central topic in the field of evolutionary biology, considering the critical contribution of immunity to an individual’s fitness. A common technique used by ecologists to estimate immunocompetence in wild populations is the phytohemagglutinin (PHA) – skin test. In this test, the degree of local swelling triggered by PHA is usually considered an estimate of T-lymphocyte activity, although there is an ongoing debate regarding this interpretation. Here, we coupled the PHA–skin test with a histological analysis to examine the temporal development of the cell-mediated response in the subterranean rodent Talas tuco-tuco (Ctenomys talarum Thomas, 1898). The inflammation response involved lymphocytes, neutrophils, eosinophils, and macrophages at the site of injection, achieving an increase of total leukocytes from 12 to 48 h after injection. However, the abundance of any of the leukocytes observed did not correlate with the degree of swelling at any time studied, suggesting that caution should be taken when interpreting the results of the PHA-induced swelling response. Particularly, the magnitude of macroscopic swelling should not be considered a priori as indicative of T-lymphocyte activity in wild-caught rodents. Our results highlight the importance of avoiding oversimplified approaches to measuring immunocompetence.

Maripa hantavirus in French Guiana: phylogenetic position and predicted spatial distribution of rodent hosts.

A molecular screening of wild-caught rodents was conducted in French Guiana, South America to identify hosts of the hantavirus Maripa described in 2008 in a hantavirus pulmonary syndrome (HPS) case. Over a 9-year period, 418 echimyids and murids were captured. Viral RNA was detected in two sigmodontine rodents, Oligoryzomys fulvescens and Zygodontomys brevicauda, trapped close to the house of a second HPS case that occurred in 2009 and an O. fulvescens close to the fourth HPS case identified in 2013. Sequences from the rodents had 96% and 97% nucleotide identity (fragment of S and M segments, respectively) with the sequence of the first human HPS case. Phylogenetic reconstructions based on the complete sequence of the S segment show that Maripa virus is closely related to Rio Mamore hantavirus. Using environmental descriptors of trapping sites, including vegetation, landscape units, rain, and human disturbance, a maximal entropy-based species distribution model allowed for identification of areas of higher predicted occurrence of the two rodents, where emergence risks of Maripa virus are expected to be higher.

Genetic Typing, Based on the 56-Kilodalton Type-Specific Antigen Gene, of Orientia tsutsugamushi Strains Isolated from Chiggers Collected from Wild-Caught Rodents in Taiwan

Orientia tsutsugamushi is the etiological agent of scrub typhus, a mite-borne, febrile illness that occurs in the Asia-Pacific region. We conducted strain characterization of O. tsutsugamushi isolates from chiggers obtained from rodents based the nucleotide sequence of the 56-kDa outer membrane protein gene. With the use of PCR, a total of 68 DNA sequences of 56-kDa antigen genes were amplified. Phylogenetic analysis revealed that there were at least six definable clusters among the 68 isolates: 37% Karp-related strains (25/68), 27% TA763 strains (18/68), 12% JG-related strains (8/68), 19% Kato-related strains (13/68), 4% divergent strains (3/68), and 1% representing a Gilliam prototype strain (1/68). Overall, the O. tsutsugamushi genotypes exhibited a high degree of diversity, similar to that seen in strains from the rest of the areas where scrub typhus is endemic. Moreover, the 56-kDa protein sequence similarity between O. tsutsugamushi isolates from mites and those from human patients (H. Y. Lu et al., Am. J. Trop. Med. Hyg. 83:658-663, 2010) were striking, thus highlighting potential risk factors for this emerging zoonotic disease.

Detection ofBartonella tamiaeDNA in Ectoparasites from Rodents in Thailand and Their Sequence Similarity with Bacterial Cultures from Thai Patients

Ectoparasites, including chigger mites (genera Leptotrombidium, Schoengastia, and Blankarrtia) and one tick (genus Haemaphysalis) collected from wild-caught rodents in Thailand, were assessed for the presence of Bartonella DNA by using a polymerase chain reaction assay targeting the 16S-23S intergenic spacer region and citrate synthase gene (gltA). Of the 41 pooled samples tested, 34 were positive for Bartonella DNA. Sequence analysis demonstrated that DNA detected in 33 chigger mite pools and one tick pool was similar to Bartonella tamiae sequences previously isolated from three patients in Thailand. This is the first report of the detection of B. tamiae DNA in chigger mites; additional field and experimental investigations are required to determine the role of chigger mites as potential vectors of B. tamiae.

First Report of Leishmania tropica from a Classical Focus of L. major in North-Sinai, Egypt

Cutaneous leishmaniasis (CL) is prevalent in the Egyptian Sinai Peninsula and previous research has consistently documented the etiologic agent to be Leishmania major. We report the first isolation of Leishmania tropica from human cases of CL in a Northern Sinai community bordering Palestine. Parasite culturing, real-time polymerase chain reaction (PCR), gene sequencing, and restriction fragment length polymorphism (RFLP) analyses indicate CL cases in this community were caused by either L. major or L. tropica (three cases each). Two wild-caught rodents (Gerbillus pyramidum floweri) were infected with L. tropica. Phlebotomus papatasi sand flies were found harboring L. major, however only non-infected individuals of Phlebotomus sergenti, a vector for L. tropica, were caught. Patients with L. tropica had not traveled from the region in over a year, suggesting these cases are autochthonous. This scenario is consistent with an incursion of L. tropica from bordering countries and raises concerns about expansion of this parasite further into Egypt.

What is the role of small rodents in the transmission cycle of Trypanosoma cruzi and Trypanosoma evansi (Kinetoplastida Trypanosomatidae)? A study case in the Brazilian Pantanal

Determining the reservoir hosts for parasites is crucial for designing control measures, but it is often difficult to identify the role that each host species plays in maintaining the cycle of infection in the wild. One way to identify potential maintenance hosts is to estimate key parameters associated with transmission and pathogenicity. Here we assess the potential for three native rodent species of the Brazilian Pantanal ( Clyomys laticeps, Thrichomys pachyurus and Oecomys mamorae) to act as reservoir or maintenance hosts of Trypanosoma evansi, an important parasite of domestic livestock. By analyzing blood parameters of naturally infected wild-caught rodents of these species, we compared their levels of parasitemia and anemia due to T. evansi infection with literature values for other host species infected by this parasite. We also analyzed levels of these blood parameters relative to infection by Trypanosoma cruzi, the causative agent of Chagas disease in humans, for which wild rodents are already thought to be important reservoir species. All three species showed low impacts of the two trypanosomes on their blood parameters compared to other species, suggesting that they experience a low virulence of trypanosome infection under natural conditions in the Pantanal and might act as maintenance hosts of trypanosome infections. The low parasitemia of trypanosome infections suggests that these rodents play a secondary role in the transmission cycle compared to other species, especially compared to the capybara ( Hydrochaeris hydrochaeris) which also experiences low pathogenicity due to infection despite much higher levels of parasitemia.

Surveys of rodent‐borne disease in Thailand with a focus on scrub typhus assessment

The epidemiology of many rodent-borne diseases in South-East Asia remains ill-defined. Scrub typhus and lep-tospirosis are common and medically significant, while other zoonotic diseases, such as spotted fever group Rickettsiae have been identified, but their overall medical significance is unknown. Rodent surveillance was conducted from June 2002 to July 2004 in 18 provinces from Thailand. Traps were set up for one to three nights. Blood and serum samples and animal tissue samples (liver, spleen, kidney and urinary bladder) were collected. Chiggermites, ticks and fleas were removed from captured rodents. A total of 4536 wild-caught rodents from 27 species were captured over two years of animal trapping. Rattus rattus was the dominant species, followed by Rattus exulans and Bandicota indica. Almost 43 000 ectoparasites were removed from the captured animals. Approximately 98% of the ectoparasites were chigger-mites, of which 46% belonged to the genus Leptotrombidium (scrub typhus vector). Other genera included Schoengastia and Blankaartia. Tick and flea specimens together comprised less than 1% of the sample. Among the five species of ticks collected, Haemaphysalis bandicota was the predominant species caught, followed by Ixodes granulatus other Haemaphysalis spp., Rhipicephalus spp. and Dermacentor spp. Only two species of fleas were collected and Xenopsylla cheopis (rat flea) was the predominant species. Using both commercial diagnostic kits and in-house molecular assays, animal tissue samples were examined and screened for zoonotic diseases. Seven zoonotic diseases were detected: scrub typhus, leptospirosis, murine typhus, tick typhus, bartonella, babesiosis and trypanosomiasis. Most samples were positive for scrub typhus. Other zoonotic diseases still under investigation include borrelosis, ehrlichiosis, the plague, and other rickettsial diseases. Using geographic information systems, global positioning systems and remote sensing technology, epidemiological and environmental data were combined to assess the relative risk in different biotopes within highly endemic areas of scrub typhus in Thailand.

Serologic evidence of a Rickettsia akari-like infection among wild-caught rodents in Orange County and humans in Los Angeles County, California

We detected antibodies reactive with Rickettsia akari, the etiologic agent of rickettsialpox in humans and in 83 of 359 (23%) rodents belonging to several species, collected in Orange County, CA. Reciprocal antibody titers >1:16 to R. akari were detected in native mice and rats (Peromyscus maniculatus, P. eremicus, and Neotoma fuscipes) and in Old World mice and rats (Mus musculus, Rattus rattus, and R. norvegicus), representing the first time that antibodies reactive with this agent have been detected in four of these species and the first report of these antibodies in rodents and humans west of the Mississippi River. We then tested serum samples from individuals who used a free clinic in downtown Los Angeles and found that 25 of 299 (8%) of these individuals had antibody titers >1:64 to R. akari. Serologic evidence suggested that R. akari or a closely related rickettsia is prevalent among several rodent species at these localities and that infection spills over into certain segments of the human population. Isolation or molecular confirmation of the agent is needed to conclusively state that R. akari is the etiologic agent infecting these rodents.

Characterization of Orientia tsutsugamushi isolated from wild-caught rodents and chiggers in northern Thailand.

We previously reported Orientia tsutsugamushi detection from tissue samples (kidney, liver, spleen, and whole blood) of 12 wild-caught rodents from Chiangrai Province, northern Thailand. Of the 30 chiggers individually removed from scrub typhus-infected rodents, 2 were found positive for O. tsutsugamushi. We further characterized the O. tsutsugamushi detected from these rodents and chiggers by RFLP using three different enzyme digestions. All 14 O. tsutsugamushi samples (12 from tissue samples and 2 from chiggers) showed different digestion patterns when compared to those of reference strains (Karp, Kato, and Gilliam). Interestingly, nine RFLP profiles were observed from these 14 samples suggesting the presence of high genetic diversity of O. tsutsugamushi in this area. Furthermore, one sample displayed the same RFLP pattern as that of O. tsutsugamushi mild resistant strain previously isolated from scrub typhus patient in Chiangrai. Of the two samples from positive chiggers, only one was found to have a similar RFLP pattern to that of its host rodent. DNA sequencing of the entire 56 kDa genome of these O. tsutsugamushi samples is in progress.

B16 タイ北部のチャングライ地方で捕獲した野鼠の諸臓器および寄生ツツガムシからの PCR によるツツガムシ病リケッチアの検出

B16 タイ北部のチャングライ地方で捕獲した野鼠の諸臓器および寄生ツツガムシからの PCR によるツツガムシ病リケッチアの検出

Hantavirus transmission: potential role of ectoparasites.

Hantavirus pulmonary syndrome is an often-fatal disease thought to be transmitted exclusively by rodents. We report the first evidence of hantavirus-specific RNA (Bayou) from two trombiculid mites (chiggers) and an ixodid tick parasitizing wild-caught rodents at a field site in Texas and also from a trombiculid mite in the free-living predatory stage of the chigger life cycle collected from the same site.

Plasma Testosterone Levels Are Related to Various Aspects of Locomotor Activity in Wild-Caught Male Meadow Voles ( Microtus pennsylvanicus)

PERROT-SINAL, T. S., D. INNES, M. KAVALIERS AND K.-P. OSSENKOPP. Plasma testosterone levels are related to various aspects of locomotor activity in wild-caught male meadow voles (Microtus pennsylvanicus). Physiol Behav 64(1) 31–36, 1998. The relationship between plasma testosterone levels and locomotor activity in wild-caught sexually mature male meadow voles ( Microtus pennsylvanicus) was assessed in the laboratory. Several aspects of locomotor activity were monitored for 1 h on two consecutive days using the automated Digiscan activity monitoring system. Plasma testosterone levels were determined immediately following the second day of activity monitoring. Significant Pearson correlations were obtained between plasma testosterone levels and total distance traveled [ r(10) = 0.55, p < 0.05] and amount of time spent in movement [ r(10) = 0.55, p < 0.05] on the second day. The wild voles showed a reduction in activity levels from the first to the second day of activity monitoring, which is indicative of habituation to a novel environment. This study provides direct evidence for a significant correlation between laboratory measures of behavioral activity and plasma testosterone levels in a wild-caught rodent. These findings indicate that previous assessments of hormone–behavior relationships in laboratory-bred rodents are consistent with the relationship between hormones and behavior in wild rodents.

Distribution, diversity, and host specificity of Bartonella in rodents from the Southeastern United States.

A number of Bartonella isolates were obtained from seven species of rodents sampled from 12 geographic sites representing the major biotic communities of the southeastern United States. Bartonella were isolated from the blood of 42.2% of 279 tested rodents. The highest prevalence of infection typically occurred among the most commonly captured species in the rodent community. Four phylogenetic groups, uniting 14 genotypic variants of Bartonella, were identified by sequence analysis of the citrate synthase gene. The level of sequence homology between genotypic groups varied from 88.8% to 96.4%, and the degree of homology among variants within groups was > or = 97%. Cotton rats (Sigmodon hispidus) harbored up to three phylogenetic groups of Bartonella at a single site, and Bartonella of two phylogenetic groups were isolated from a single rodent. All the Bartonella isolated from three species of Peromyscus clustered in a single distinct phylogenetic group, suggesting some host specificity may occur. Mouse ascitic fluids produced in BALB/c mice inoculated with Bartonella of three phylogenetic groups demonstrated high indirect fluorescent antibody (IFA) titers to homologous antigens. However, use of eight Bartonella antigens in an IFA test with sera from 394 wild-caught rodents resulted in either little or extremely low titers of antibody.