Oligoryzomys Longicaudatus Research Articles

A 19 Year Analysis of Small Mammals Associated with Human Hantavirus Cases in Chile.

Small mammals present in areas where hantavirus cardiopulmonary syndrome (HCPS) cases had occurred in central and southern Chile were captured and analyzed to evaluate the abundance of rodents and seroprevalence rates of antibodies to Andes orthohantavirus (ANDV). Sampling areas ranged from the Coquimbo to Aysén regions (30–45° S approx.) regions. Ninety-two sites in peridomestic and countryside areas were evaluated in 19 years of sampling. An antibody against ANDV was detected by strip immunoassay in 58 of 1847 specimens captured using Sherman traps. Of the eleven species of rodents sampled, Abrothrix olivacea, Oligoryzomys longicaudatus and Abrothrix hirta were the most frequently trapped. O. longicaudatus had the highest seropositivity rate, and by logistic regression analysis, O. longicaudatus of at least 60 g had 80% or higher probability to be seropositive. Sex, age and wounds were significantly related to seropositivity only for O. longicaudatus. Across administrative regions, the highest seropositivity was found in the El Maule region (34.8–36.2° S), and the highest number of HCPS cases was registered in the Aysén region. Our results highlight the importance of long term and geographically extended studies, particularly for highly fluctuating pathogens and their reservoirs, to understand the implications of the dynamics and transmission of zoonotic diseases in human populations.

1471. Case Report: Andes Virus Hantavirus Pulmonary Syndrome in a Traveler Returning to the United States

BackgroundAndes virus (ANDV), a New World hantavirus, is transmitted to humans via contact with the long-tailed pygmy rice rat (Oligoryzomys longicaudatus) in Chile and Argentina. Unlike other hantaviruses, ANDV can be transmitted person-to-person. It has a case mortality rate of approximately 30%. Here we describe the first known, imported case of ANDV to the United States.MethodsOn January 9, 2018, a 29-year-old female with no significant past medical history returned to the United States from a 3-week group trip to Chile and Argentina. She did not receive vaccines or take prophylaxis. She visited Central California before returning to Delaware. January 19 she presented with fevers, vomiting, and extreme fatigue. Examination was remarkable for hypotension requiring fluid resuscitation and O2 saturation of 89% on room air. She described chest tightness. Influenza, community acquired pneumonia, and PE were considered. Sputum influenza A/B and RSV PCR were negative. Laboratories revealed hypoalbuminemia at 2.2 g/dL, thrombocytopenia at 61,000, and transaminitis with AST 342 and ALT 302. WBC was within normal range with maximum of 11,000. Computerized tomography (CT) of chest revealed bilateral lower lobe ground-glass opacities, pleural effusions, and pulmonary edema. She was started on antibiotics. Her symptoms continued. She developed blurred vision and peri-orbital edema. She required 3 L O2 nasal cannula. Headaches, sweats, peripheral edema, and rales developed. Lyme, Ehrlichia, malaria studies, and blood cultures were negative. Acute EBV, CMV, HIV, hepatitis, and dengue serologies were also negative. Hantavirus serologies were obtained Day 4 of admission. She was discharged Day 6 after resolution of fever, hypoxia and thrombocytopenia.ResultsHantavirus ELISA IgG and IgM were reported positive 4 days after discharge and testing at the CDC confirmed ANDV infection.ConclusionHantavirus is prevalent in certain South American locales. It should be considered in all patients returning from Chile and Argentina with fever, shortness of breath, and thrombocytopenia. Early recognition of symptoms and hallmark laboratories can identify patients that may require advanced supportive measures to decrease overall mortality.Disclosures All authors: No reported disclosures.

Distributional ecology of Andes hantavirus: a macroecological approach

BackgroundHantavirus pulmonary syndrome (HPS) is an infection endemic in Chile and Argentina, caused by Andes hantavirus (ANDV). The rodent Oligoryzomys longicaudatus is suggested as the main reservoir, although several other species of Sigmodontinae are known hosts of ANDV. Here, we explore potential ANDV transmission risk to humans in southern South America, based on eco-epidemiological associations among: six rodent host species, seropositive rodents, and human HPS cases.MethodsWe used ecological niche modeling and macroecological approaches to determine potential geographic distributions and assess environmental similarity among rodents and human HPS cases.ResultsHighest numbers of rodent species (five) were in Chile between 35° and 41°S latitude. Background similarity tests showed niche similarity in 14 of the 56 possible comparisons: similarity between human HPS cases and the background of all species and seropositive rodents was supported (except for Abrothrix sanborni). Of interest among the results is the likely role of O. longicaudatus, Loxodontomys micropus, Abrothrix olivaceus, and Abrothrix longipilis in HPS transmission to humans.ConclusionsOur results support a role of rodent species’ distributions as a risk factor for human HPS at coarse scales, and suggest that the role of the main reservoir (O. longicaudatus) may be supported by the broader rodent host community in some areas.

Space Use and Social Mating System of the Hantavirus Host, Oligoryzomys longicaudatus.

The long-tailed mouse, Oligoryzomys longicaudatus (Cricetidae: Sigmodontinae), is the major host of Andes hantavirus, the etiological agent of hantavirus pulmonary syndrome in the south of Argentina and Chile. Studying the ecology of this species is necessary to understand how Andes hantavirus is maintained in nature. In this study, we examine the home range size and intra- and intersexual overlap degree of male and female O. longicaudatus in order to elucidate the mating system of this species. To our knowledge, this research provides the first documentation, obtained from a specific design, of spacing and mating systems in this species in Argentina. The study was conducted seasonally from April (autumn) 2012 to October (spring) 2013 in a shrubland habitat of Cholila, Andean region, Argentina. We studied spacing patterns using 59 and 51 home ranges established by adult males and females, respectively, in two 3.24ha capture-marked and recapture grids. Significant differences between sexes in home range size and overlap degree were found. Male home ranges were always larger than those of females. We observed exclusive space use both among males and females (13.15±18.67, and 3.60±3.43%, respectively). Considering only those males that get access to receptive females (40%), average intersexual overlap value was about 30.82±19.73%. Sexual differences in home range sizes and the spatial avoidance between breeding males, that would reflect intrasexual competition for receptive females, allows us to propose a polygynous mating system for O. longicaudatus.

Factors associated with hantavirus infection in a wild host rodent from Cholila, Chubut Province, Argentina

Andes virus (ANDV) is a hantavirus hosted by the sigmodontine rodent Oligoryzomys longicaudatus in southern Argentina, where it is responsible for most cases of hantavirus pulmonary syndrome (HPS). The purpose of this study is to elucidate the biological and ecological characteristics of the host that increase the probability of ANDV infection in a O. longicaudatus population. The study was performed from spring 2003 to winter 2008 at Cholila, Chubut Province, Argentina. Rodent populations were sampled in four habitat types. Species, sex, body measurements (mass, body and tail length) and presence of wounds were recorded and blood samples for seroprevalence determination were obtained from the retroorbital sinus. Logistic regression models were applied to identify variables associated with the probability of infection of an individual. The most parsimonious model included sex, mass, body size and wounds as explanatory variables. Our results suggest that population structure and composition (age and sex) of O. longicaudatus should be considered as fundamental indicators to model the probability that infection with ANDV appears and/or persists in a population. A high Odds ratio value also showed the presence of wounds as an important feature in the infection model.

Movimientos de roedores intra- e inter-ambiente y riesgo de exposición al Hantavirus "Andes" en Patagonia norte, Argentina

Se estudiaron algunos aspectos de la ecologia espacial de tres especies de roedores sigmodontinos (Oligoryzomys longicaudatus, Abrothrix olivacea y Abrothrix hirta) en el Paraje El Contra del Parque Nacional Lanin (Provincia de Neuquen, Argentina). Los resultados se analizaron en el marco del riesgo de exposicion humana al Hantavirus Andes, agente causal del Sindrome Pulmonar por Hantavirus. El trabajo se realizo en dos tipos de ambiente: silvestre y domestico. Los roedores fueron capturados mensualmente con la metodologia de captura-marcado-recaptura. De esta manera se estimaron y compararon los movimientos dentro y entre ambos ambientes y los tamanos de areas de accion. Oligoryzomys longicaudatus, principal reservorio del Hantavirus Andes en Patagonia, presento el mayor numero de capturas en ambos ambientes y mas de lo esperado por azar dentro de los ambientes domesticos. Ademas, mostro las areas de accion con menor tamano promedio y movimientos intra-ambiente estadisticamente significativos. Los ambientes domesticos rurales resultaron ser potencialmente los mas riesgosos en terminos de exposicion y transmision de Hantavirus a humanos. Como resultado de las capturas y movimientos dispersivos de O. longicaudatus, se discuten otras contribuciones de este trabajo a la salud humana.https://doi.org/10.25260/EA.17.27.2.0.427

Feeding habits and people’s perception of the Barn Owl ( Tyto alba tuidara , J.E.Gray 1829) in urban settings of Southern Chile: Implications for conservation

People’s perception on birds of prey is heavily influenced by its intrinsic value, utility, myths and superstitions. In particular, negative perceptions may encourage poaching and persecution of these birds, affecting their conservation status. One nocturnal raptor species widely distributed across the world is the Barn Owl (Tyto alba, Tytonidae). In Chile, this species has been recorded and studied exclusively in rural and sub-urban areas. However, in the city of Valdivia Barn owls exist within the city boundaries. In this study we documented the feeding habits of Barn owls nesting in urban settings of Valdivia, and we analyze the opinions of local neighbors toward the owls. To characterize the diet of owls, we collected all pellets found around their nesting tree on a monthly basis between August 2010 and August 2011. We interviewed the neighbors using a questionnaire that included questions about the utility, ethical or aesthetic value of the owl and the tree where they nested. Our results indicate that the main prey of the Barn Owl was the Long-tailed Colilargo (Oligoryzomys longicaudatus). The neighbors’ perception was favorable to the Barn Owl primarily for aesthetic and ethical reasons, and not utilitarian reasons. Our results suggest that people perception in urban areas is different than in rural areas, where previous studies showed the prevalence of utilitarian values. This positive perception represents a great potential to promote conservation and environmental education in the city, creating a link between people and the natural elements they have in their environment.

Ecological consequences of an unusual simultaneous masting of Araucaria araucana and Chusquea culeou in North‐West Patagonia, Argentina

AbstractA simultaneous masting of two abundant species in the temperate forests of North‐West Argentinean Patagonia occurred in 2013 for the first time ever recorded: the semelparous bamboo grass Chusquea culeou (colihue), dominating the understory, flowered and set seed across 1100 km2 while pehuén (Araucaria araucana), an endemic conifer co‐dominating the tree layer had the highest regionally synchronized mast event in the last 30 years. Strong trophic effects were expected as a consequence of this extraordinary amount of seed, such as rodent outbreaks (ratadas) that followed previous Chusquea spp. mast events and included Oligoryzomys longicaudatus, the main reservoir of the Andes virus causing the Hantavirus Pulmonar Syndrome. From March 2013 to May 2014, we sampled relative abundance and activity of seed‐eaters and carnivores at four study sites with different proportions of both masting species. Surprisingly, total rodent capture rates never exceeded 14% in wild habitats and 8% in peridomestic areas showing low overall density in spite of some heavy O. longicaudatus males extending their reproductive activity into winter. Total abundance and relative proportion of granivorous birds peaked at the four sites in winter or spring, when they are usually scarce. Other surveyed organisms (native and exotic seed‐eaters, ungulates and carnivores) showed moderate responses at most, probably through aggregation from surrounding areas rather than reproduction. Seed removal from experimental seed stations varied in time and space though never peaked. The clearest pattern of community responses, though much subtler than expected, occurred at the site where colihue was abundant and pehuén scarce. This is the first systematic study that reports such a simultaneous double masting and our surveys revealed no widespread community consequences. We propose that either contingent events, such as an unprecedented drought, or permanent environmental features or contextual characteristics may explain the lack of a rodent outbreak in this area.

Knowledge, attitudes, and practices regarding hantavirus disease and acceptance of a vaccine trial in rural communities of southern Chile

ABSTRACT Andes hantavirus cardiopulmonary syndrome, transmitted by Oligoryzomys longicaudatus, has no approved treatment, a case fatality rate of 35%, and documented person-to-person transmission. An Andes vaccine, highly needed for prevention, is in development. We aimed to evaluate knowledge, attitudes and practices (KAP) regarding hantavirus disease and willingness to participate in a future Andes vaccine trials through a cross sectional face-to-face oral survey of a randomly selected adult sample from 2 rural communes in southern Chile. Human subjects approval was obtained from our institutional IRBs, and participants signed informed consent. We enrolled 319 subjects from Corral and 321 from Curarrehue; 98% had heard about hantavirus disease and its reservoir but only half knew about transmission, symptoms and prevention. Participants fear the disease but are only partially aware of their own risk. One third of participants reported presence of rodents inside their homes. Despite moderate confidence in their health system, most subjects perceived vaccines as beneficial, and 93% would accept an approved hantavirus vaccine. Half would agree to participate in a vaccine trial and 29% would allow their children to participate. Motivations to participate were mainly altruistic, while risk perception was the main reason for declining. Knowledge about hantavirus disease and prevention practices require reinforcement, and a vaccine trial seems feasible in these populations.

Trophic ecology of two raptors, Barn Owl (Tyto alba) and White-tailed Kite (Elanus leucurus), and possible implications for biological control of Hantavirus reservoir in Chile

ABSTRACT Raptors are important predators of various species of small mammals, which renders them of economic importance since their prey may be either disease vectors or reservoirs which represent health problems, or economically important through the damage they cause to crops and stocks. The long-tailed rice rat Oligoryzomys longicaudatus is a reservoir and vector of Hantavirus, a disease of increasing importance in various Latin American countries. The nocturnal Barn Owl (Tyto alba) and the diurnal White-tailed Kite (Elanus leucurus) appear to be the most significant predators of this species. Here, we characterize the diet of these two raptors and analyze their trophic specialization and dietary selectivity using published information, pellet analysis, and field abundances of small mammals. Both raptor species positively selected O. longicaudatus in their diets to suggest that they could be potential controllers of the Hantavirus reservoir in Chile, both in natural and agricultural ecosystems. Predati...

Native forest replacement by exotic plantations triggers changes in prey selection of mesocarnivores

ABSTRACT Replacement of native forests by forest plantations may change the composition and abundance of small mammals, thus influencing the foraging behavior of mesocarnivores in these human-created habitats. We assessed how differences in prey abundance between native forests and exotic plantations in southern Chile may explain the prey selection of four mesocarnivores, as analyzed from their scats. Using a spatial zero-inflated Poisson model, we determined that the abundance of most small mammals was lower in plantations than native forests, except for three common species, which had similar or larger abundances in exotic plantations. We assessed mesocarnivores' prey selection by assessing the coefficients and log-ratios of use and availability of a Bayesian Resource Selection Function. We determined that in native forest, the preferences of kodkod ( Leopardus guigna ) for arboreal prey was stronger, whereas chilla fox ( Pseudalopex griseus ) and Darwin's fox ( Pseudalopex fulvipes ) exhibited a selective preference for ground prey. Darwin's fox also exhibited a habitat-dependent changes in their selection for Darwin's leaf-eared mouse ( Phyllotis darwini ), from a positive log ratio in native forest to a negative ratio in exotic plantations. Conversely, culpeo fox ( Pseudalopex culpaeus ) selected long-tailed colilargo ( Oligoryzomys longicaudatus ) and Chilean climbing mouse ( Irenomys tarsalis ) in plantations only, even though these prey were more abundant in native forests. Although mature commercial forest plantations may provide feeding grounds for mesocarnivores, depending on their species-specific ability to capture available prey, the decline of small mammal availability in plantations may modify the prey selection of mesocarnivores.

Transcriptome markers of viral persistence in naturally-infected Andes Hantavirus (Bunyaviridae) seropositive rice rats

The long-tailed pygmy rice rat ( Oligoryzomys longicaudatus ) is the reservoir host of Andes (ANDV) and Oran hantaviruses ( Bunyaviridae ). To examine transcriptome features of persistently infected rice rats, spleens from ANDV sero-positive wild-caught rice rats were assessed. RNA-seq analysis, de novo reference-independent assembly and stringent orthology assignments produced 17,756 unique coding and non-coding RNAs. Differential expression analysis of persistently-infected seropositive rice rat spleens revealed 18 differentially expressed transcripts from 16 unique genes. A three-pronged effect on the immune response were observed in 1) suppression of the JAK-STAT pathway at Stat5b and Ccnot1, as well as 2) a bias toward a TH2 response in the enrichment of caspase-1 and 3) stimulation of RIG-I pathway factors Ppp1cc and MFF. Two of these differentially expressed transcripts, caspase-1 and STAT5b, code for proteins expected to stimulate T helper follicular (T FH ) cell development, a phenomenon that has also been described for hantavirus-infected P. maniculatus . Differential expression of a single seropositive rice rat with a higher viral load revealed a robust response of 243 differentially expressed transcripts, suggesting an acute infection. Together, these data help define the fundamental features of the immune response in a hantavirus reservoir host.

Transcriptome markers of viral persistence in naturally-infected andes virus (bunyaviridae) seropositive long-tailed pygmy rice rats.

Long-tailed pygmy rice rats (Oligoryzomys longicaudatus) are principal reservoir hosts of Andes virus (ANDV) (Bunyaviridae), which causes most hantavirus cardiopulmonary syndrome cases in the Americas. To develop tools for the study of the ANDV-host interactions, we used RNA-Seq to generate a de novo transcriptome assembly. Splenic RNA from five rice rats captured in Chile, three of which were ANDV-infected, was used to generate an assembly of 66,173 annotated transcripts, including noncoding RNAs. Phylogenetic analysis of selected predicted proteins showed similarities to those of the North American deer mouse (Peromyscus maniculatus), the principal reservoir of Sin Nombre virus (SNV). One of the infected rice rats had about 50-fold more viral burden than the others, suggesting acute infection, whereas the remaining two had levels consistent with persistence. Differential expression analysis revealed distinct signatures among the infected rodents. The differences could be due to 1) variations in viral load, 2) dimorphic or reproductive differences in splenic homing of immune cells, or 3) factors of unknown etiology. In the two persistently infected rice rats, suppression of the JAK-STAT pathway at Stat5b and Ccnot1, elevation of Casp1, RIG-I pathway factors Ppp1cc and Mff, and increased FC receptor-like transcripts occurred. Caspase-1 and Stat5b activation pathways have been shown to stimulate T helper follicular cell (TFH) development in other species. These data are also consistent with reports suggestive of TFH stimulation in deer mice experimentally infected with hantaviruses. In the remaining acutely infected rice rat, the apoptotic pathway marker Cox6a1 was elevated, and putative anti-viral factors Abcb1a, Fam46c, Spp1, Rxra, Rxrb, Trmp2 and Trim58 were modulated. Transcripts for preproenkephalin (Prenk) were reduced, which may be predictive of an increased T cell activation threshold. Taken together, this transcriptome dataset will permit rigorous examination of rice rat-ANDV interactions and may lead to better understanding of virus ecology.

Temporal fine‐scale genetic variation in the zoonosis‐carrying long‐tailed pygmy rice rat in Patagonia, Argentina

AbstractFactors modeling the population genetic structure are of major importance when species involved in the transmission of zoonoses are considered. The long‐tailed pygmy rice rat or ‘colilargo’ Oligoryzomys longicaudatus is a highly vagile rodent species which acts as the reservoir of the Andes hantavirus in southern Argentina and Chile. To contribute to the knowledge of the processes determining the microgeographical genetic structure of populations of this species, we used 10 microsatellite loci to estimate the levels of polymorphism, individual relatedness and the population effective sizes through time and to explore if the effective size correlated with density. Individuals were sampled seasonally during a 25‐month period in a population from the Argentinean Patagonia located in the endemic area of Hantavirus Pulmonary Syndrome. We detected three genetic clusters. An important temporal change in cluster prevalence was detected after a population bottleneck. Individuals of the same period presented higher mean relatedness values than between consecutive periods. Density and effective population size estimations were correlated. All analyses performed in this study are in line with the conclusion that high levels of gene flow encompassing different habitats would be a major process producing fine‐scale temporal changes in the genetic composition of the studied population.

First record of Litomosoides pardinasi (Nematoda: Onchocercidae) in native and exotic rodents from Chile

We report the first record of Litomosoides pardinasi in native and exotic rodents from Chile. Litomosoides pardinasi, described in the Argentine Patagonia parasitizing Phyllotis xanthopygus and Oligoryzomys longicaudatus, was found in Chile parasitizing the peritoneal and thoracic cavities of O. longicaudatus (prevalence (P)= 18.9%, mean intensity (MI)= 57.3) and Phyllotis darwini (P=4.2%, MI=10), and in the peritoneal cavity of Rattus rattus (P=1.24%; MI=22.5). Total P in native rodents from Chile was significantly lower than in Argentina, while the total MI was higher. Prevalence and MI of L. pardinasi in O. longicaudatus from Chile and Argentina showed non-significant differences; prevalence in P. darwini from Chile was significantly lower than in P. xanthopygus from Argentina and than in Chilean O. longicaudatus. Our results, together with those from Argentina, support the hypothesis that L. pardinasi is well established in O. longicaudatus, but seems to be recently acquired by P. darwini and the exotic R. rattus. Considering the known host distribution of Litomosoides species among the sigmodontines, our results also support the hypothesis that L. pardinasi first colonized the Oryzomyini tribe and later, by different phenomena of host-switching, colonized the Phyllotini tribe and the exotic R. rattus.

Micromamíferos, cambio climático e impacto antrópico: ¿Cuánto han cambiado las comunidades del sur de América del Sur en los últimos 500 años?

Introduction: The last 500 years of the historical era, an interval that corresponds to the concerted dispersal of European explorers, traders, and colonists around the globe, has witnessed the global disappearance of ~90 mammal species. Besides the known cases of biological extinctions, this time period was also characterized by the regional extirpations of specialized taxa and by the expansion and population growth of some opportunistic species. Several lines of evidence suggest that the current configuration of small mammal communities - i. e . richness (number of species) and diversity (distribution of species abundance)- in southern South America would have been generated in the period after the arrival of Europeans ca . 1500 AD. In this study, we reviewed the fossil record for small rodents and marsupials during the last 500 years, with emphasis on the Pampean and Patagonian regions. Based on these findings, we offer some considerations concerning the biogeography and conservation of these species. Methods: Micromammals from archaeological and paleontological sites have provided considerable information on environmental conditions during the Quaternary in South America. In this work, we reviewed several micromammal fossil samples, mostly generated by the trophic activity of owls. The use of this kind of data involves some extrinsic and intrinsic biases that must be considered at the time to study the diversity of past communities, such as the bird involved on the accumulations, its hunting techniques, the time of the year, the size and behavior of the prey species, etc. For this work, we compared the fossil samples with more than 700 owl pellet assemblages of the same geographical areas. Results: Richness and diversity of small mammal communities was higher prior to the deepest human impact (> 0.5 ka), showing a pronounced drop in both parameters to the present. The regional extinction of some cricetid rodents and small marsupials was recorded, both in the Pampean ( e. g. Bibimys torresi , Pseudoryzomys simplex ) and in the Patagonian regions ( e . g . Euneomys mordax, Lestodelphys halli, Tympanoctomys kirchnerorum ), as well as the biological extinctions of the bat Desmodus cf. D . draculae and the cavy Galea tixiensis in the Pampas. At this same time, opportunistic species ( e. g. Calomys spp., Oligoryzomys longicaudatus ) showed a dramatic increase of their populations, especially in the most extensively disturbed areas. Discussion and conclusions: In the last 500 years, significant variations occurred in the micromammal assemblages of southern South America. These changes included the dispersion and increase (in some cases extensive) of some specialized species and the regional extinctions of others, involving hundreds to thousands of kilometers of distributional extent. We suggest that the changes produced by livestock and agriculture have caused extensive habitat uniformity which was beneficial for some opportunistic taxa ( e. g . Calomys spp., Oligoryzomys longicaudatus ), facilitating their dispersion and allowing the increase of their populations. Anthropic disturbances also include the extensive use of fire, urbanization, and introduction of exotic forbs and grasses. Of about 46 species rodents considered as Least Concern by the IUCN and with fossil record for the last 500 years, 23 (50 %) have experienced drastic reductions in their range or abundance during the Late Holocene. At least nine taxa are completely extinct, including one marsupial, one bat and seven rodents. Similar phenomena are recorded in other areas of the Southern Hemisphere, both in continental and island contexts. This evaluation of the fossil record highlights the need to evaluate more carefully the status of some species with supposedly stable populations, but which are likely to be affected by future extensive changes in their environments ( e. g . mining, expansion of the agricultural frontier). Key words: Argentina, Didelphimorphia, extinctions, small mammals, Rodentia, Sigmodontinae.

Modeling to predict cases of hantavirus pulmonary syndrome in Chile.

BackgroundHantavirus pulmonary syndrome (HPS) is a life threatening disease transmitted by the rodent Oligoryzomys longicaudatus in Chile. Hantavirus outbreaks are typically small and geographically confined. Several studies have estimated risk based on spatial and temporal distribution of cases in relation to climate and environmental variables, but few have considered climatological modeling of HPS incidence for monitoring and forecasting purposes.MethodologyMonthly counts of confirmed HPS cases were obtained from the Chilean Ministry of Health for 2001–2012. There were an estimated 667 confirmed HPS cases. The data suggested a seasonal trend, which appeared to correlate with changes in climatological variables such as temperature, precipitation, and humidity. We considered several Auto Regressive Integrated Moving Average (ARIMA) time-series models and regression models with ARIMA errors with one or a combination of these climate variables as covariates. We adopted an information-theoretic approach to model ranking and selection. Data from 2001–2009 were used in fitting and data from January 2010 to December 2012 were used for one-step-ahead predictions.ResultsWe focused on six models. In a baseline model, future HPS cases were forecasted from previous incidence; the other models included climate variables as covariates. The baseline model had a Corrected Akaike Information Criterion (AICc) of 444.98, and the top ranked model, which included precipitation, had an AICc of 437.62. Although the AICc of the top ranked model only provided a 1.65% improvement to the baseline AICc, the empirical support was 39 times stronger relative to the baseline model.ConclusionsInstead of choosing a single model, we present a set of candidate models that can be used in modeling and forecasting confirmed HPS cases in Chile. The models can be improved by using data at the regional level and easily extended to other countries with seasonal incidence of HPS.

Estimating Hantavirus Risk in Southern Argentina: A GIS-Based Approach Combining Human Cases and Host Distribution

We use a Species Distribution Modeling (SDM) approach along with Geographic Information Systems (GIS) techniques to examine the potential distribution of hantavirus pulmonary syndrome (HPS) caused by Andes virus (ANDV) in southern Argentina and, more precisely, define and estimate the area with the highest infection probability for humans, through the combination with the distribution map for the competent rodent host (Oligoryzomys longicaudatus). Sites with confirmed cases of HPS in the period 1995–2009 were mostly concentrated in a narrow strip (~90 km × 900 km) along the Andes range from northern Neuquén to central Chubut province. This area is characterized by high mean annual precipitation (~1,000 mm on average), but dry summers (less than 100 mm), very low percentages of bare soil (~10% on average) and low temperatures in the coldest month (minimum average temperature −1.5 °C), as compared to the HPS-free areas, features that coincide with sub-Antarctic forests and shrublands (especially those dominated by the invasive plant Rosa rubiginosa), where rodent host abundances and ANDV prevalences are known to be the highest. Through the combination of predictive distribution maps of the reservoir host and disease cases, we found that the area with the highest probability for HPS to occur overlaps only 28% with the most suitable habitat for O. longicaudatus. With this approach, we made a step forward in the understanding of the risk factors that need to be considered in the forecasting and mapping of risk at the regional/national scale. We propose the implementation and use of thematic maps, such as the one built here, as a basic tool allowing public health authorities to focus surveillance efforts and normally scarce resources for prevention and control actions in vast areas like southern Argentina.

Borrelia chilensis, a new member of theBorrelia burgdorferisensu lato complex that extends the range of this genospecies in theSouthernHemisphere

Borrelia burgdorferi sensu lato (s.l.), transmitted by Ixodes spp. ticks, is the causative agent of Lyme disease. Although Ixodes spp. ticks are distributed in both Northern and Southern Hemispheres, evidence for the presence of B. burgdorferi s.l. in South America apart from Uruguay is lacking. We now report the presence of culturable spirochetes with flat-wave morphology and borrelial DNA in endemic Ixodes stilesi ticks collected in Chile from environmental vegetation and long-tailed rice rats (Oligoryzomys longicaudatus). Cultured spirochetes and borrelial DNA in ticks were characterized by multilocus sequence typing and by sequencing five other loci (16S and 23S ribosomal genes, 5S-23S intergenic spacer, flaB, ospC). Phylogenetic analysis placed this spirochete as a new genospecies within the Lyme borreliosis group. Its plasmid profile determined by polymerase chain reaction and pulsed-field gel electrophoresis differed from that of B. burgdorferi B31A3. We propose naming this new South American member of the Lyme borreliosis group B. chilensis VA1 in honor of its country of origin.

Predominant Th2 cytokine gene expression in lymph node cell cultures from Andes virus-infected deer mice (Peromyscus maniculatus) (P6316)

Abstract Deer mice (Peromyscus maniculatus) are the principal reservoir hosts of Sin Nombre virus (SNV), while long-tailed pygmy rice rats (Oligoryzomys longicaudatus) are the principal reservoir hosts of Andes virus (ANDV). These viruses cause the great majority of hantavirus cardiopulmonary syndrome cases in North and South America. The disease in humans is principally an inflammatory immunopathology that results in a pronounced capillary leak syndrome with a 36% fatality rate due to cardiogenic shock. In contrast, infection of rodent reservoirs with their hantaviruses results in life-long persistence, without signs of disease, that appears to be mediated by regulatory T cells. Deer mice are experimentally susceptible to ANDV; however, they clear infection within 56 days. We infected deer mice with SNV or ANDV for 14 days and examined the immune responses to each virus. Lymph node cells from infected deer mice were harvested and cultured with viral antigens to examine expression of 94 immune-related genes by real-time PCR. We found that most of the same genes were expressed in both SNV- and ANDV-infected deer mice; however, the magnitude of gene expression, particularly Th2 genes, were significantly greater in lymph node cells from ANDV-infected deer mice. Together, these results suggest a quantitative effect occurs in the host response to a reservoir hantavirus (SNV) compared to a nonreservoir hantavirus (ANDV) and is associated with persistence or clearance.