Diffusion and Home Range Parameters from Rodent Population Measurements in Panama

Simple random walk considerations are used to interpret rodent population data collected in Hantavirus-related investigations in Panama regarding the short-tailed cane mouse, \emph{Zygodontomys brevicauda}. The diffusion constant of mice is evaluated to be of the order of (and larger than) 200 meters squared per day. The investigation also shows that the rodent mean square displacement saturates in time, indicating the existence of a spatial scale which could, in principle, be the home range of the rodents. This home range is concluded to be of the order of 70 meters. Theoretical analysis is provided for interpreting animal movement data in terms of an interplay of the home ranges, the diffusion constant, and the size of the grid used to monitor the movement. The study gives impetus to a substantial modification of existing theory of the spread of the Hantavirus epidemic which has been based on simple diffusive motion of the rodents, and additionally emphasizes the importance for developing more accurate techniques for the measurement of rodent movement.Comment: 18 pages, 5 figure

Ecologically-Based Management of Rodent Pests

Farm Management,

Geographical distribution and relative risk of Anjozorobe virus (Thailand orthohantavirus) infection in black rats (Rattus rattus) in Madagascar

Acknowledgements We thank those who facilitated the survey: householders, heads of fokontany, local administration and health authorities from Ministry of Health. We would like to express our gratitude to the staff of the Plague Central Laboratory Unit, Institut Pasteur de Madagascar: Dr. Minoarisoa Rajerison who facilitated this study; Corinne Rahaingosoamamitiana and Soanandrasana Rahelinirina for helping to conduct and organize the field work. We would also like to thank Dr. Fanjasoa Rakotomanana and Dr. Lalaina Arivony Nomenjanahary assistance in the field trips and technical and field support. Funding This work was supported by the Institut Pasteur de Madagascar (Internal Project through ZORA: Zoonoses, Rodent and Arboviruses) and Wellcome Trust Fellowships to ST (#081705, #095171). VR was also supported though Girard’s fellowship undergraduate program from the Institut Pasteur de Madagascar. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Sin Nombre Virus and Rodent Species Diversity: A Test of the Dilution and Amplification Hypotheses

BACKGROUND:Species diversity is proposed to greatly impact the prevalence of pathogens. Two predominant hypotheses, the "Dilution Effect" and the "Amplification Effect", predict divergent outcomes with respect to the impact of species diversity. The Dilution Effect predicts that pathogen prevalence will be negatively correlated with increased species diversity, while the Amplification Effect predicts that pathogen prevalence will be positively correlated with diversity. For many host-pathogen systems, the relationship between diversity and pathogen prevalence has not be empirically examined. METHODOLOGY/PRINCIPAL FINDINGS:We tested the Dilution and Amplification Effect hypotheses by examining the prevalence of Sin Nombre virus (SNV) with respect to diversity of the nocturnal rodent community. SNV is directly transmitted primarily between deer mice (Peromyscus maniculatus). Using mark-recapture sampling in the Spring and Fall of 2003-2005, we measured SNV prevalence in deer mice at 16 landscape level sites (3.1 hectares each) that varied in rodent species diversity. We explored several mechanisms by which species diversity may affect SNV prevalence, including reduced host density, reduced host persistence, the presence of secondary reservoirs and community composition. We found a negative relationship between species diversity and SNV prevalence in deer mice, thereby supporting the Dilution Effect hypothesis. Deer mouse density and persistence were lower at sites with greater species diversity; however, only deer mouse persistence was positively correlated with SNV prevalence. Pinyon mice (P. truei) may serve as dilution agents, having a negative effect on prevalence, while kangaroo rats (Dipodomys ordii), may have a positive effect on the prevalence of SNV, perhaps through effects on deer mouse behavior. CONCLUSIONS/SIGNIFICANCE:While previous studies on host-pathogen systems have found patterns of diversity consistent with either the Dilution or Amplification Effects, the mechanisms by which species diversity influences prevalence have not been investigated. Our study indicates that changes in host persistence, coupled with interspecific interactions, are important mechanisms through which diversity may influence patterns of pathogens. Our results reveal the complexity of rodent community interactions with respect to SNV dynamics

First Evidence of Akodon-Borne Orthohantavirus in Northeastern Argentina

Orthohantaviruses (genus Orthohantavirus, family Hantaviridae) are the etiologic agents of Hantavirus Pulmonary Syndrome in the Americas. In South America, orthohantaviruses are highly diverse and are hosted by sigmodontine rodents (subfamiliy Sigmodontinae, family Cricetidae), an also diverse group of rodents. The aims of this work were to (1) identify orthohantavirus hosts and (2) to study the spatial and temporal variations in the prevalence of infection and their associations with community, environmental and individual characteristics, in different environments of Misiones province, northeastern Argentina. Live-capture sessions were carried out during two years in different land uses, with a trapping effort of 31,653 trap nights. We captured 719 individuals from the species Akodon montensis, Rattus rattus, Mus musculus, Calomys tener, Thaptomys nigrita, Oligoryzomys nigripes, Euryoryzomys russatus, Oligoryzomys flavescens, Brucepattersonius sp., and Juliomys pictipes. Antibodies against orthohantavirus were detected in Akodon montensis in one natural protected and one periurban areas, and it was the most abundant species in almost every study sites. We observed the presence of spatial focality of orthohantavirus infection and a positive association with host abundance suggesting the existence of a threshold density. At the individual level, large, reproductively active, and male individuals were more likely to have antibodies against orthohantavirus. This is the first record of orthohantavirus infection in A. montensis in Argentina, which shows the importance of investigations about emerging diseases.Fil: Burgos, Eliana Florencia. Administracion Nacional de Laboratorios E Institutos de Salud "dr. Carlos G. Malbran". Instituto Nacional de Medicina Tropical.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vadell, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Administracion Nacional de Laboratorios E Institutos de Salud "dr. Carlos G. Malbran". Instituto Nacional de Medicina Tropical.; ArgentinaFil: Bellomo, Carla María. Dirección Nacional de Instituto de Investigación. Adm.nacional de Laboratorio E Instituto de Salud "dr.c.g.malbran". Instituto Nacional de Enfermedades Infecciosas. Departamento de Virologia; ArgentinaFil: Martinez, Valeria Paula. Dirección Nacional de Instituto de Investigación. Adm.nacional de Laboratorio E Instituto de Salud "dr.c.g.malbran". Instituto Nacional de Enfermedades Infecciosas. Departamento de Virologia; ArgentinaFil: Salomón, Oscar Daniel. Administracion Nacional de Laboratorios E Institutos de Salud "dr. Carlos G. Malbran". Instituto Nacional de Medicina Tropical.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gomez Villafañe, Isabel Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

A Newly Identified Hantavirus: The Development of Immunologic Diagnostic Assays and Phylogenetic Analysis for Detection and Characterization

Hantaviruses are the etiologic agents of hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia and hantavirus cardiopulmonary syndrome (HCPS) in the Americas. As of July 2005, 396 HCPS cases in 30 U.S. states with a 36% mortality rate have been confirmed since reporting began in 1993. The primary rodent host of numerous U.S. hantaviruses in Peromyscus maniculatus (deer mouse) although other strains have been found in association with a district rodent host and geographical region. Reservoir hosts are asymptomatically, persistently infected and shed virus particles intermittently in urine, saliva and feces. Thus, the primary transmission route for hantavirus from infected small mammals to humans is inhalation of aerosolized excreta. Between September 13, 2000 and December 1, 2000; November 28 and 29, 2001; May 27, 2002 through July 24, 2002; and May 1, 2004 through May 8, 2004 trapping was conducted in the Great Smoky Mountains National Park (GSMNP). A total of 310 rodents and 35 insectivores (a total of 345 animals) were captured. Blood samples were obtained from 305 animals and subsequently tested for anti-hantavirus antibodies with enzyme linked immunosorbent assays (ELISAs) and immunofluorescent assay (IFA). We performed RT-PCR, PCR and sequencing analysis encoding the immunodominant region of the nucleocapsid (N) protein contained within the S gene. A 59 amino acid peptide was synthesized based on the deduced amino acid sequence of the 59 residue epitope region of the N protein. This 59-mer was applied as a serodiagnostic antigen in an ELISA for the detection of anti-hantavirus antibody in rodent and insectivore sera. The sensitivity and specificity of the ELISA were comparable to those of an IFA using virus infected cells. The only seropositive animals detected were deer mice and white-footed mice (Peromyscus leucopus). The overall estimated seroprevalance in GSMNP was 8.9% (27/305). In our study, we also developed a one-step real-time detection-PCR (RTD-PCR) assay based on Superscript III reverse-transcriptase-Platinum Taq polymerase enzyme mixture. PCR amplicons were detected in real time with the use of a 5’hybridization probe. Results were compared to RT-PCR/nested PCR amplification products. We dectected our target genome sequence in one Sorex fumeus (smoky shrew), one Clethrionomys gapperi (Southern red-backed vole) and 16 mice of Peromyscus spp. by RTD-PCR. The overall estimated viral prevalence in GSMNP was 5.2% (18/345). Sequence analysis of the amplicon detected in the smoky shrew was identical to that previously taken from a deer mouse. This is the first reported case of a New World hantavirus being detected in a shrew and the first evidence of a hantavirus detected in a Clethrionomys spp. Lastly, we sequenced G1 and G2 segments of the M gene and performed phylogenetic analysis with these segments and the N segment. We have designated this hantavirus strain Newfound Gap virus (NGV). The G1 and G2 segments demonstrated homology to New York virus, a pathogenic strain maintained in white-footed mice while the N segment demonstrated greater homology to Monongahela and Sin Nombre viruses, also pathogenic strains maintained in deer mice. The incongruous homologies of the NGV S and M segments to other closely related hantaviruses suggest that genetic reassortment resulting in a hybrid virus may have occurred. NGV possesses unique characteristics and is closely related to pathogenic strains that have resulted in HCPS case fatalities in this region

Climate change and sugarcane expansion increase Hantavirus infection risk

Hantavirus Cardiopulmonary Syndrome (HCPS) is a disease caused by Hantavirus, which is highly virulent for humans. High temperatures and conversion of native vegetation to agriculture, particularly sugarcane cultivation can alter abundance of rodent generalist species that serve as the principal reservoir host for HCPS, but our understanding of the compound effects of land use and climate on HCPS incidence remains limited, particularly in tropical regions. Here we rely on a Bayesian model to fill this research gap and to predict the effects of sugarcane expansion and expected changes in temperature on Hantavirus infection risk in the state of São Paulo, Brazil. The sugarcane expansion scenario was based on historical data between 2000 and 2010 combined with an agro-environment zoning guideline for the sugar and ethanol industry. Future evolution of temperature anomalies was derived using 32 general circulation models from scenarios RCP4.5 and RCP8.5 (Representative greenhouse gases Concentration Pathways adopted by IPCC). Currently, the state of São Paulo has an average Hantavirus risk of 1.3%, with 6% of the 645 municipalities of the state being classified as high risk (HCPS risk ≥ 5%). Our results indicate that sugarcane expansion alone will increase average HCPS risk to 1.5%, placing 20% more people at HCPS risk. Temperature anomalies alone increase HCPS risk even more (1.6% for RCP4.5 and 1.7%, for RCP8.5), and place 31% and 34% more people at risk. Combined sugarcane and temperature increases led to the same predictions as scenarios that only included temperature. Our results demonstrate that climate change effects are likely to be more severe than those from sugarcane expansion. Forecasting disease is critical for the timely and efficient planning of operational control programs that can address the expected effects of sugarcane expansion and climate change on HCPS infection risk. The predicted spatial location of HCPS infection risks obtained here can be used to prioritize management actions and develop educational campaigns

Spatiotemporal Dynamics of Hantavirus Cardiopulmonary Syndrome Transmission Risk in Brazil

Background: Hantavirus disease in humans is rare but frequently lethal in the Neotropics. Several abundant and widely distributed Sigmodontinae rodents are the primary hosts of Orthohantavirus and, in combination with other factors, these rodents can shape hantavirus disease. Here, we assessed the influence of host diversity, climate, social vulnerability and land use change on the risk of hantavirus disease in Brazil over 24 years. Methods: Landscape variables (native forest, forestry, sugarcane, maize and pasture), climate (temperature and precipitation), and host biodiversity (derived through niche models) were used in spatiotemporal models, using the 5570 Brazilian municipalities as units of analysis. Results: Amounts of native forest and sugarcane, combined with temperature, were the most important factors influencing the increase of disease risk. Population at risk (rural workers) and rodent host diversity also had a positive effect on disease risk. Conclusions: Land use change—especially the conversion of native areas to sugarcane fields—can have a significant impact on hantavirus disease risk, likely by promoting the interaction between the people and the infected rodents. Our results demonstrate the importance of understanding the interactions between landscape change, rodent diversity, and hantavirus disease incidence, and suggest that land use policy should consider disease risk. Meanwhile, our risk map can be used to help allocate preventive measures to avoid disease.publishedVersio

Doctor of Philosophy

dissertationSin Nombre virus (SNV), a strain of hantavirus, causes hantavirus pulmonary syndrome (HPS) in humans, a deadly disease with high mortality rate (>50%). The primary virus host is deer mice, and greater deer mice abundance has been shown to increase the human risk of HPS. There is a great need in understanding the nature of the virus host, its temporal and spatial dynamics, and its relation to the human population with the purpose of predicting human risk of the disease. This research studies SNV dynamics in deer mice in the Great Basin Desert of central Utah, USA using multiyear field data and integrated geospatial approaches including remote sensing, Geographic Information System (GIS), and a spatially explicit agent-based model. The goal is to advance our understanding of the important ecological and demographic factors that affect the dynamics of deer mouse population and SNV prevalence. The primary research question is how climate, habitat disturbance, and deer mouse demographics affect deer mouse population density, its movement, and SNV prevalence in the sagebrush habitat. The results show that the normalized difference vegetation index (NDVI) and the enhanced vegetation index (EVI) can be good predictors of deer mouse density and the number of infected deer mice with a time lag of 1.0 to 1.3 years. This information can be very useful in predicting mouse abundance and SNV risk

Ecologic studies of rodent reservoirs: their relevance for human health.

Within the past few years, the number of "new" human diseases associated with small-mammal reservoirs has increased dramatically, stimulating renewed interest in reservoir ecology research. A consistent, integrative approach to such research allows direct comparisons between studies, contributes to the efficient use of resources and data, and increases investigator safety. We outline steps directed toward understanding vertebrate host ecology as it relates to human disease and illustrate the relevance of each step by using examples from studies of hosts associated with rodent-borne hemorrhagic fever viruses