Ecological study of hantavirus infection in wild rodents in an endemic area in Brazil
Graphical abstract
The present paper reports a 3-year population dynamic study of the hantavirus rodents’ reservoirs in an endemic area of hantavirus pulmonary syndrome, Southern Brazil.
Introduction
The genus Hantavirus (family Bunyaviridae), a group of rodent/insectivore-borne RNA viruses, is widely distributed in the world and includes a variety of strains recognized as human pathogens (Hjelle and Torres-Pérez, 2010, Jonsson et al., 2010, Schmaljohn and Hjelle, 1997). Rodents of the families Muridae and Cricetidae were described as the primary zoonotic reservoirs of these viruses, but distinct hantaviruses have also been discovered in several species of shrews and moles (Arai et al., 2007, Kang et al., 2009, Klempa et al., 2007, Yadav et al., 2007). Transmission is assumed to occur through human inhalation of aerosolized virus from rodents’ urine and/or feces, direct (agonistic encounters), or indirect (contaminated food or environment) contact among rodents (Sauvage et al., 2003).
Hantavirus cardiopulmonary syndrome (HCPS) is considered as one of the major emerging diseases in Brazil, mainly owing to its high mortality rate (∼40%). Since 1993, over 1600 cases of HCPS have been reported and at present, there are eight hantavirus described in Brazil related to Sigmodontinae rodents: Juquitiba/Araucaria, Araraquara, Castelo dos Sonhos, Anajatuba, Laguna Negra, Rio Mearim, Jabora, and Rio Mamore viruses carried by Oligoryzomys nigripes, Necromys lasiurus, Oligoryzomys utiaritensis, Oligoryzomys fornesi, Calomys callidus, Holochilus sciureus, Akodon montensis, and Oligoryzomys microtis, respectively (Oliveira et al., 2011, Firth et al., 2012, Johnson et al., 1999, Raboni et al., 2009, Raboni et al., 2005, Rosa et al., 2005, Suzuki et al., 2004, Travassos Da Rosa et al., 2012, Travassos da Rosa et al., 2011, Travassos da Rosa et al., 2010), the latest three were not described as causing human HCPS.
Outbreaks of different genotypes of Hantavirus in Brazil have often been related to periods of high population sizes of sigmodontine rodents that are commonly associated to agricultural and peridomestic rural environments (Mills and Childs, 1998, Suzuki et al., 2004). These rodents have predominantly granivorous feeding habits and opportunistic reproductive strategies (Gentile et al., 2000). These features allow them to reach high population sizes in certain periods, mainly in productive cropland areas responding quickly to environmental changes. Both the abundance of hantavirus reservoir species and the serostatus within the reservoir population are associated with a suite of biotic and abiotic environmental variables, such as precipitation, habitat quality, and food availability (Mills, 2005).
Ecological studies of hantaviruses are still lacking in Brazil. Little is known about the ecology and temporal dynamics of hantavirus infection in host populations, since most of the studies were punctual in space and time (Oliveira et al., 2009, Raboni et al., 2009, Suzuki et al., 2004, Travassos da Rosa et al., 2010). In the Municipality of Jaborá, an endemic area of HCPS in Southern Brazil, we observed the co-circulation of Juquitiba and Jabora viruses in O. nigripes and A. montensis and recently described the genetic characterization of these two hantaviruses in this region (Oliveira et al., 2011). The present paper reports a population dynamic study of the hantavirus rodents’ reservoirs in this area, investigating the factors related to the hantavirus infection and transmission in the rodent populations during three years.
Section snippets
Study area and sampling
An ecological study of small mammals was carried out in the municipality of Jaborá located in the mid-western region of Santa Catarina State, in Southern Brazil (Fig. 1). Jaborá has 4041 inhabitants (IBGE – Brazilian Institute of Geography and Statistics) and most of them (60.28%) live in rural areas. The economic development of this region is based on farming and cattle raising (agricultural activities). The study area presents a mixed ombrophilous forest that is a vegetation type in the
Population dynamics
From March 2004 to December 2006, we captured 994 individuals of 14 rodent species: A. montensis (n = 323), Akodon paranaensis (n = 39), Brucepattersonius iheringi (n = 18), Delomys dorsalis (n = 1), N. lasiurus (n = 8), Nectomys squamipes (n = 17), O. nigripes (n = 437), Oxymycterus judex (n = 21), Sooretamys angouya (n = 12), Thaptomys nigrita (n = 89) (Rodentia, Sigmodontinae), Mus musculus (n = 15), Rattus rattus (n = 10) (Rodentia, Murinae), Euryzygomatomys spinosus (n = 3) (Rodentia, Echimyidae), Cavia aperea (n =
Discussion
More than 18 years have passed since HCPS was first described in the American continent. Since then, hantavirus studies, predominantly ecological studies on wild reservoirs, were conducted in many regions (Mills et al., 2010, Palma et al., 2012). In Brazil, most of the studies concerning hantavirus reservoirs were either virus descriptions or short-term local investigations (Oliveira et al., 2009, Raboni et al., 2009, Suzuki et al., 2004, Travassos da Rosa et al., 2010). In this study, we thus
Conflict of interest statement
No competing financial interests exist.
Acknowledgments
We thank the Jaborá Municipal Health Secretary, the Santa Catarina Health Secretary, and the Secretary of Health Surveillance for assistance during the development of our studies in Jaborá. We are grateful to the field team of the Laboratory of Biology and Parasitology of Wild Mammal Reservoirs, IOC/FIOCRUZ, who participated in the Jaborá expeditions. We thank Dr. Helena Bergallo (UERJ/RJ) and Dr. Sotiris Missailidis for time spent on reviewing the manuscript. We thank Raphael Gomes for
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