Modeling potential risk areas of Orthohantavirus transmission in Northwestern Argentina using an ecological niche approach.

BACKGROUND: Hantavirus Pulmonary Syndrome (HPS) is a rodent-borne zoonosis in the Americas, with up to 50% mortality rates. In Argentina, the Northwestern endemic area presents half of the annually notified HPS cases in the country, transmitted by at least three rodent species recognized as reservoirs of Orthohantavirus. The potential distribution of reservoir species based on ecological niche models (ENM) can be a useful tool to establish risk areas for zoonotic diseases. Our main aim was to generate an Orthohantavirus risk transmission map based on ENM of the reservoir species in northwest Argentina (NWA), to compare this map with the distribution of HPS cases; and to explore the possible effect of climatic and environmental variables on the spatial variation of the infection risk. METHODS: Using the reservoir geographic occurrence data, climatic/environmental variables, and the maximum entropy method, we created models of potential geographic distribution for each reservoir in NWA. We explored the overlap of the HPS cases with the reservoir-based risk map and a deforestation map. Then, we calculated the human population at risk using a census radius layer and a comparison of the environmental variables' latitudinal variation with the distribution of HPS risk. RESULTS: We obtained a single best model for each reservoir. The temperature, rainfall, and vegetation cover contributed the most to the models. In total, 945 HPS cases were recorded, of which 97,85% were in the highest risk areas. We estimated that 18% of the NWA population was at risk and 78% of the cases occurred less than 10 km from deforestation. The highest niche overlap was between Calomys fecundus and Oligoryzomys chacoensis. CONCLUSIONS: This study identifies potential risk areas for HPS transmission based on climatic and environmental factors that determine the distribution of the reservoirs and Orthohantavirus transmission in NWA. This can be used by public health authorities as a tool to generate preventive and control measures for HPS in NWA.

Calomys callosus: An Experimental Animal Model Applied to Parasitic Diseases Investigations of Public Health Concern.

The appearance and spread of parasitic diseases around the world aroused the interest of the scientific community to discover new animal models for improving the quality and specificity of surveys. Calomys callosus is a rodent native to South America, an easy handling model, with satisfactory longevity and reproducibility. C. callosus is susceptible to toxoplasmosis and can be used as experimental model for the study the pathogenesis, treatment, vertical transmission, and ocular toxoplasmosis. C. callosus can also be used to study cutaneous and visceral leishmaniasis, as the animals present cutaneous lesions, as well as parasites in the organs. C. callosus has epidemiological importance in Chagas disease, and since it is a Trypanosoma cruzi natural host in which rodents show high parasitemia and lethality, they are also effective as a model of congenital transmission. In the study of schistosomiasis, Schistosoma mansoni was proven to be a C. callosus natural host; thus, this rodent is a great model for fibrosis, hepatic granulomatous reaction, and celloma associated with lymphomyeloid tissue (CALT) during S. mansoni infection. In this review, we summarize the leading studies of parasitic diseases that used C. callosus as a rodent experimental model, describing the main uses and characteristics that led them to be considered an effective model.

Multimarker approach to assess the exposure of the wild rodent Calomys laucha to a simulated crude oil spill.

A mysterious oil spill occurred in the ocean near Brazil in 2019, which affected coastal areas in northeastern Brazil. When oil pollution occurs in coastal zones, organisms such as small mammals can suffer deleterious effects to their health. This study aimed to evaluate the effects of exposure to contaminated sandy soil with different crude oil concentrations in males of the species Calomys laucha. The exposure to crude oil resulted in multiple health issues for the subjects in the very first days of exposure. Furthermore, the exposure resulted in mutagenic damage to bone marrow blood cells and behavioral and morphological alterations, which were almost always in a dose-dependent form. The present study demonstrates the sensibility of the biomarkers used and highlights that small wild mammals such as C. laucha are useful for predicting environmental damage caused by the exposure to crude oil.

Life cycle of Ixodes schulzei (Acari: Ixodidae) in the laboratory, and demonstration of reproduction by parthenogenesis.

Ixodes schulzei is an ixodid tick that parasitizes Cricetidae rodents, chiefly the South American water rat, Nectomys squamipes, in Brazil and Argentina. In the present study, we evaluated the life cycle of I. schulzei by exposing larvae and nymphs to feed on two rodent species, N. squamipes and Calomys callosus (large vesper mouse),while adult ticks were exposed to feed on N. squamipes. Off-host developmental periods were observed in an incubator at 27 °C, 95% relative humidity, and 0:24 (light:dark) regimen. Larvae and nymphs successfully fed on either C. callosus or N. squamipes. Mean larval and nymphal feeding periods were 8.8 and 8.7 days on N. squamipes and 8.5 and 9.7 days on C. callosus. The majority of engorged larvae (79.0-80.8%) and nymphs (67.0-86.0%) successfully molted to nymphs and adults, respectively. Mean premolt periods were 11.5-11.7 days for engorged larvae and 22.5-23.7 days for engorged nymphs. Only adult females emerged from engorged nymphs, regardless of host species, i.e., none of 120 engorged nymphs molted to male. Around 18% of the unfed females presented teratologies compatible with the metagynander type of gynandromorphism. Ixodes schulzei adult females successfully fed (mean feeding period, 9.4 days), oviposited, and presented high reproductive performance (high engorged weight, egg mass weight, and % egg mass hatching), in the absence of male ticks. Our results showed that I. schulzei successfully reproduces by parthenogenesis, and corroborate field data that indicate N. squamipes as the most important host for this tick species. The male of I. schulzei remains unknown.

A Novel Genotype and First Record of Trypanosoma lainsoni in Argentina.

Trypanosomes are a group of parasitic flagellates with medical and veterinary importance. Despite many species having been described in this genus, little is known about many of them. Here, we report a genetic and morphological characterization of trypanosomatids isolated from wild mammals from the Argentine Chaco region. Parasites were morphologically and ultrastructurally characterized by light microscopy and transmission electron microscopy. Additionally, 18s rRNA and gGAPDH genes were sequenced and analyzed using maximum likelihood and Bayesian inference. Morphological characterization showed clear characteristics associated with the Trypanosoma genus. The genetic characterization demonstrates that the studied isolates have identical sequences and a pairwise identity of 99% with Trypanosoma lainsoni, which belongs to the clade of lizards and snakes/rodents and marsupials. To date, this species had only been found in the Amazon region. Our finding represents the second report of T. lainsoni and the first record for the Chaco region. Furthermore, we ultrastructurally described for the first time the species. Finally, the host range of T. lainsoni was expanded (Leopardus geoffroyi, Carenivora, Felidae; and Calomys sp., Rodentia, Cricetidae), showing a wide host range for this species.

Atrazine exposure in gestation and breastfeeding affects Calomys laucha sperm cells.

The present study evaluated the effects of low doses of atrazine administered during gestation and breastfeeding on sperm characteristics of the wild rodent Calomys laucha. Adult females were divided into groups of 10 and administered different doses of atrazine through gavage, during gestational or breastfeeding period. At 3 months of age, the F1 adult male progeny of these females was evaluated. We observed a drastic reduction in the total and progressive motility of male sperm cells at all doses and during both the exposure periods. Moreover, the plasma membrane integrity of adult male sperm cells decreased at all doses of atrazine administered during the breastfeeding, whereas the membrane fluidity of these cells increased at all tested doses. Atrazine led to a decrease in the sperm mitochondrial functionality at all doses and during both exposure periods. The damage to the sperm DNA was higher in males exposed to the highest dose (1.0 mg/kg) during the gestation period, and in animals exposed to the lowest dose of atrazine (0.1 mg/kg) during breastfeeding period. Furthermore, the highest dose (1.0 mg/kg) of atrazine reduced the sperm concentration. Furthermore, the reduced levels of reactive oxygen species (ROS) were observed at all evaluated doses in males exposed during the gestation period. These results suggest that the administration of low doses of atrazine at critical periods of development may permanently reduce the sperm quality in C. laucha.

Cyclooxygenase (COX)-2 Inhibitors Reduce Toxoplasma gondii Infection and Upregulate the Pro-inflammatory Immune Response in Calomys callosus Rodents and Human Monocyte Cell Line.

Toxoplasma gondii is able to infect a wide range of vertebrates, including humans. Studies show that cyclooxygenase-2 (COX-2) is a modulator of immune response in multiple types of infection, such as Trypanosoma cruzi. However, the role of COX-2 during T. gondii infection is still unclear. The aim of this study was to investigate the role of COX-2 during infection by moderately or highly virulent strains of T. gondii in Calomys callosus rodents and human THP-1 cells. C. callosus were infected with 50 cysts of T. gondii (ME49), treated with COX-2 inhibitors (meloxicam or celecoxib) and evaluated to check body weight and morbidity. After 40 days, brain and serum were collected for detection of T. gondii by real-time PCR and immunohistochemistry or cytokines by CBA. Furthermore, peritoneal macrophages or THP-1 cells, infected with RH strain or uninfected, were treated with meloxicam or celecoxib to evaluate the parasite proliferation by colorimetric assay and cytokine production by ELISA. Finally, in order to verify the role of prostaglandin E2 in COX-2 mechanism, THP-1 cells were infected, treated with meloxicam or celecoxib plus PGE2, and analyzed to parasite proliferation and cytokine production. The data showed that body weight and morbidity of the animals changed after infection by T. gondii, under both treatments. Immunohistochemistry and real-time PCR showed a reduction of T. gondii in brains of animals treated with both COX-2 inhibitors. Additionally, it was observed that both COX-2 inhibitors controlled the T. gondii proliferation in peritoneal macrophages and THP-1 cells, and the treatment with PGE2 restored the parasite growth in THP-1 cells blocked to COX-2. In the serum of Calomys, upregulation of pro-inflammatory cytokines was detected, while the supernatants of peritoneal macrophages and THP-1 cells demonstrated significant production of TNF and nitrite, or TNF, nitrite and MIF, respectively, under both COX-2 inhibitors. Finally, PGE2 treatment in THP-1 cells triggered downmodulation of pro-inflammatory mediators and upregulation of IL-8 and IL-10. Thus, COX-2 is an immune mediator involved in the susceptibility to T. gondii regardless of strain or cell types, since inhibition of this enzyme induced control of infection by upregulating important pro-inflammatory mediators against Toxoplasma.

Diferencia espacial de la incidencia de fiebre hemorrágica argentina y la composición y abundancia de roedores en el ensamble / Spatial difference in the incidence of Argentine Hemorrhagic Fever and composition and abundance of rodents in the assemblage

Resumen La fiebre hemorrágica argentina (FHA) es una enfermedad zoonótica endémica en una amplia zona de la pampa húmeda de Argentina. El agente etiológico es el virus Junin que es mantenido en la naturaleza por el roedor Calomys musculinus y transmitido, principalmente, al humano a través de aerosoles generados de las secreciones y excreciones. Objetivos: Caracterizar la composición y diversidad de los ensambles de pequeños roedores, determinar la abundancia del hospedador C. musculinus y la prevalencia del virus de la FHA en las zonas epidémica, histórica y no endémica de dicha enfermedad en Argentina. Métodos: Para el muestreo de roedores en cada una de las zonas se demarcaron un área central y dos periféricas para 18 localidades de la región central de Argentina (incluyendo las provincias de Córdoba, Buenos Aires y Santa Fe) muestreadas en dos años. Se comparó la abundancia de C. musculinus entre zonas y entre las áreas dentro de cada zona y áreas cercanas entre zonas, utilizando modelos de análisis de varianza anidados. Resultados. Dentro de cada zona, el ensamble de roedores mostró diferencia espacial en la composición específica, diversidad y abundancia de C. musculinus. La zona epidémica registró mayor número de especies y mayor abundancia del hospedador. En zona histórica se capturó el menor número de especies (de roedores) y Akodon azarae fue la más abundante. En zona no endémica la composición del ensamble y la abundancia de C. musculinus variaron entre los dos años. Sólo se detectó infección por virus Junin en C. musculinus correspondientes a la zona epidémica con una prevalencia de 2,7 y 1,1% para los años 2007 y 2008, respectivamente. Conclusión: En este sistema, la abundancia del hospedador estaría afectando la dinámica espacial de este virus, más que la diversidad del ensamble o la presencia de A. azarae.

Background. The Argentine Hemorrhagic Fever (AHF) is a zoonotic disease endemic in a wide area of the humid pampa of Argentina. The etiologic agent is the Junin virus that is maintained in the wild by the rodent Calomys musculinus and transmitted to humans, mainly, through aerosols generated from secretions and excretions. Aims: To characterize and compare the assemblages of small rodent composition and diversity inside the epidemic, historic and non-endemic zone of AHF and to register C. musculinus abundance in each zone and in each area within each zone, registering the prevalence of infection in rodent populations. Method: One central and two peripheral areas were delimited to sample rodents in each zone with different incidence of AHF. Thus, 18 localities were selected to do the sampling in two years. Host abundance between zones and among areas inside each zone and among nearby areas between zones were compared applying nested ANOVA's. Results: In each zone, the rodent assemblage showed differences in composition, diversity and numeric representation of C. musculinus. The epidemic zone was the richest of the three, registering also great host abundance; meanwhile in the historic zone, A. azarae was the dominant numeric species with less number of other species. Regarding the non-endemic zone, the assemblage composition and C. musculinus abundance varied respect the sampled year. Junin virus infection was only detected in C. musculinus individuals corresponding to the epidemic zone, with a prevalence of 2.7 and 1.1% for the years 2007 and 2008, respectively. Conclusion: In this system, the abundance of C. musculinus could be impacting over the pathogen dynamic, rather than the assemblage diversity or the A. azarae presence.

Low atrazine dosages reduce sperm quality of Calomys laucha mice.

Reproductive effects caused by the exposure to environmentally relevant dosages of atrazine on wild animals are poorly understood. This study evaluated the effects of three dosages of atrazine on sperm parameters of adult Calomys laucha males. Adult mice were orally exposed to dosages of 0 (water and vehicle control), 0.1, 1, and 10 mg/kg of animal weight for a 21-day period. Following exposure, analyses were performed to determine sperm motility parameters, plasma membrane integrity and fluidity, mitochondrial functionality, acrosome integrity, DNA damage, lipid peroxidation, and production of reactive oxygen species (ROS) in the sperm samples. Total and progressive motility were reduced in all dosages in comparison to control groups. Membrane integrity and mitochondrial functionality of sperm were reduced in all dosages, and the sperm membrane fluidity increased in the higher dosages of atrazine (1 and 10 mg/kg), in comparison with the vehicle control. A decrease in the acrosome integrity was noted at 10 mg/kg of atrazine, compared to the control groups. The integrity of DNA, ROS generation, and lipid peroxidation of sperm showed no significant differences when compared with the control groups. These results suggest that exposure to low dosages of atrazine can affect sperm parameters of Calomys laucha and therefore reduce the reproductive capacity of wild rodent species.

Detection of Latino virus (Arenaviridae: Mammarenavirus) naturally infecting Calomys callidus.

Mammarenavirus species are associated with a specific rodent host species, although an increasing number of virus has been associated to more than one host, suggesting that co-evolution is less robust than initially thought. There are few eco-epidemiological studies of South America mammarenaviruses in non-endemic areas of Arenavirus Hemorrhagic Fever, affecting specially our current knowledge about animal reservoirs and virus range and host-virus relations. In Brazil, seven arenavirus species were described in seven different rodent species. Here in we describe a new rodent reservoir species in Brazil related to the previously described Latino mammarenavirus (LATV) MARU strain. Samples of 148 rodents from Mato Grosso state, Brazil were analyzed. Amplification of the glycoprotein precursor gene (GPC) was observed in six Calomys callidus rodents. According to phylogenetic inferences, is observed a well-supported monophyletic clade of LATV from C. callidus and other Clade C mammarenavirus. In addition, the phylogenetic relations of both genes showed a close relation between LATV MARU and Capão Seco strains, two distinct lineages. Additionally, the results obtained in this study point out to a change of scenario and in previously stabilized patterns in the dynamics of South American mammarenaviruses, showing that with more studies in AHF non-endemic or silent areas, more potential hosts for this virus will be discovered.

Pinhal Virus, a New Arenavirus Isolated from Calomys tener in Brazil.

Arenavirus Sabiá was originally isolated from a fatal human infection in Brazil, and after the occurrence of the second fatal human case in São Paulo state, epidemiologic and virologic studies were performed in the area where the patient lived, aiming at the identification of the Sabiá natural rodent reservoir. A broadly cross-reactive enzyme-linked immunosorbent assay (ELISA) was used to screen for antibody-positive samples. Antibodies to arenavirus were detected in two of the 55 samples of Calomys tener, and from these results, samples of rodents were analyzed by a broad RT-PCR assay. RT-PCR amplification detected arenavirus sequences in five of the 55 C. tener samples, and sequencing showed that this virus is a distinct form of Sabiá virus. Thus, we describe here the evidence for the circulation of a new arenavirus in Brazil (proposed name Pinhal virus) and its genetic characterization compared to other arenaviruses. This study also suggests C. tener as a probable rodent reservoir for this virus and associates this new virus with the lineage C of New World arenaviruses. Although we have defined some characteristics of this virus, so far, there is no evidence of its involvement in human disease.

Diet of a sigmodontine rodent assemblage in a Peruvian montane forest.

Knowledge of feeding habits of small rodents is necessary for understanding food webs, trophic structure, and plant-animal interactions in Neotropical forests. Despite several studies that have investigated community structure and feeding behavior of rodents, large gaps remain in our understanding of their guild occupancy. Our objective was to investigate the diets of 7 species of small (< 100g) sympatric sigmodontine rodents in a high (3,500 m) Andean montane rainforest in Peru. We qualitatively and quantitatively assessed diet items in fecal samples from livetrapped rodents from 2009 to 2012. Frequency data for 4 diet categories indicated that all 7 species of rodents contained 4 diet categories in fecal samples: arthropods (88%), remains of leaves and fibers from plants (61%), intact seeds (with or without fruit pulp; 50%), and mycorrhizal spores (45%). Omnivory was found to be a strategy used by all species, although contingency table analysis revealed significant differences among and within species in diet categories. Cluster analysis showed 2 main groupings: that of the Thomasomys spp. plus Calomys sorellus group which included high amounts of intact seeds and plant parts in their fecal samples, and those of the genera Akodon, Microryzomys, Oligoryzomys, which included a greater proportion of arthropods in their fecal samples, but still consumed substantial amounts of fruit and plant parts. Intact seed remains from at least 17 plant species (9 families) were found in fecal samples. We concluded that this assemblage of sigmodontine rodents is omnivorous but that they likely play an important role as frugivores and in seed dispersal in tropical montane forests in Peru. El conocimiento de los hábitos alimenticios de roedores pequeños es necesario para comprender cadenas alimenticias, estructura trófica, e interacciones planta-animal en los bosques neotropicales. A pesar de que numerosos estudios han investigado la estructura de comunidades y el comportamiento de forrajeo en roedores, aún existen grandes vacíos en nuestra comprensión de sus gremios tróficos. Nuestro objetivo fue investigar las dietas de siete especies de pequeños (< 100 g) roedores sigmodontinos simpátricos en un bosque montano andino a 3.500] m en Perú. Cualitativamente y cuantitativamente evaluamos la dieta en muestras fecales de roedores capturados entre el 2009 y el 2012. Datos de frecuencia para cuatro categorías de dieta indicaron que las siete especies de roedores consumieron cuatro categorías de dieta: artrópodos (88%), pedazos de hojas y fibras de plantas (61%), semillas intactas (con o sin pulpa de frutos; 50%), y esporas de micorrizas (45%). Omnivoría fue la estrategia utilizada por todas las especies, aunque el análisis con tablas de contingencia reveló diferencias significativas entre y dentro de especies en categorías de dieta. El análisis de agrupación presentó 2 grupos principales: el grupo Thomasomys spp. y Calomys sorellus, que incluye una gran proporción de semillas intactas, y partes de plantas en las muestras fecales y el grupo que incluye los géneros Akodon, Microryzomys y Oligoryzomys, el cual incluyó una proporción mayor de artrópodos en sus muestras fecales, pero con niveles altos de semillas intactas. Semillas intactas de al menos 17 especies de plantas (9 familias) fueron encontradas en las muestras fecales. Concluimos que este ensamble de roedores sigmodontinos es omnívoro y que probablemente las especies juegan un rol importante como frugívoros y en la dispersión de semillas en los bosques montanos tropicales en el Perú.

Sperm impairments in adult vesper mice (Calomys laucha) caused by in utero exposure to bisphenol A.

This study aimed to evaluate the effects of in utero administration of bisphenol A (BPA) on semen parameters of vesper mice. Sixty female Calomys laucha were divided into six groups and received by gavage during gestation the following substances: Water (negative control), Olive Oil (vehicle control), Diethylstilbestrol (DES - positive control - 6.5 µg kg(-1) bw) and BPA (40, 80 and 200 µg kg(-1) bw). Male offspring were euthanised at 70 days of age, and sperm parameters were analysed. BPA reduced normal sperm morphology (water = 96.1 ± 0.65; BPA200 = 96.8 ± 2.3%), sperm membrane integrity (water = 88.8 ± 1,65; BPA200 = 70.6 ± 4,15%), sperm motility (water = 87.5 ± 1.71; BPA200 = 51.3 ±9.9%) and in vitro penetration rates (water = 55.0 ± 7.14; BPA200 = 7.47 ±2.96%), but it did not affect body weight, anogenital distance, sperm DNA integrity and acrosome integrity. In conclusion, in utero exposure to BPA caused a reduction in sperm parameters of adult C. laucha. Natural mating studies should be conducted to verify the effects of BPA on fertility of the animals.

Pequenos mamiferos nao-voadores (Didelphimorphia, Rodentia) em campos litoraneos do extremo sul do Brasil

Non-volant small mammals are key elements in natural environments due its importance as food resource. This study aimed to investigate the species composition and habitat occupancy by non-volant small mammals (Didelphimorphia, Rodentia) in a coastal grassland area in southern Rio Grande do Sul coastal plain. Between April 2009 and March 2010 pitffal traps were used to capture small mammals in coastal grasslands associated to sand dunes and arbustive Restinga. We sampled 180 individuals including two marsupials (Cryptonanus guahybae and Didelphis albiventris) and seven rodent species (Calomys laucha, Cavia aperea, Ctenomys flamarioni, Deltamys kempi, Oligoryzomys flavescens, Oxymycterus nasutus and Scapteromys tumidus). Cryptonanus guahybae, D. albiventris and C. flamarioni were captured only in dunes while C. aperea and O. nasutus were recorded only in arbustive Restinga habitats. Calomys laucha, D. kempi, O. flavescens and O. nasutus were captured in both habitats. Oligoryzomys flavescens and C. laucha were the most representative species in both habitats, comprising respectively 40.7 and 38.9% of captures in dunes and 56.3 and 34.9% of captures in Restinga habitats. The species richness recorded in the sampled coastal grasslands area was lower than those previously recorded in subtropical forest coastal systems.

Pequenos mamíferos não-voadores são elementos chave em ambientes naturais devido a sua importância como recurso alimentar. Este estudo teve como objetivo investigar a composição de espécies e a ocupação de habitat por pequenos mamíferos não-voadores (Didelphimorphia, Rodentia) em uma área de campos litorâneos na região sul da planície costeira do Rio Grande do Sul. Entre abril de 2009 e março de 2010 armadilhas de interceptação e queda foram utilizadas para a captura de pequenos mamíferos em campos associados a dunas e a restinga arbustiva. Foram amostrados 180 indivíduos pertencentes a duas espécies de marsupiais (Cryptonanus guahybae e Didelphis albiventris) e sete espécies de roedores (Calomys laucha, Cavia aperea, Ctenomys flamarioni, Deltamys kempi, Oligoryzomys flavescens, Oxymycterus nasutus e Scapteromys tumidus). Cryptonanus guahybae, D. albiventris e C. flamarioni foram capturados somente em dunas, enquanto que C. aperea e O. nasutus foram registrados somente em restinga arbustiva. Calomys laucha, D. kempi, O. flavescens e O. nasutus foram capturados em ambos os ambientes. Oligoryzomys flavescens e C. laucha foram as espécies mais representativas em ambos os ambientes, compreendendo respectivamente 40,7 e 38,9% das capturas em dunas, e 56,3 e 34,9% das capturas em restinga. A riqueza de espécies registrada na área de campo litorâneo amostrada foi inferior a aquelas previamente registradas em sistemas florestais costeiros subtropicais.

Barn owl (Tyto alba) predation on small mammals and its role in the control of hantavirus natural reservoirs in a periurban area in southeastern Brazil / Predação de pequenos mamíferos por suindara (Tyto alba) e seu papel no controle de reservatórios naturais de hantavírus em uma área periurbana no Sudeste do Brasil

The aim of this study was to inventory the species of small mammals in Uberlândia, Minas Gerais, Brazil, based on regurgitated pellets of the barn owl and to compare the frequency of rodent species in the diet and in the environment. Since in the region there is a high incidence of hantavirus infection, we also evaluate the importance of the barn owl in the control of rodents that transmit the hantavirus. Data on richness and relative abundance of rodents in the municipality were provided by the Centro de Controle de Zoonoses, from three half-yearly samplings with live traps. In total, 736 food items were found from the analysis of 214 pellets and fragments. Mammals corresponded to 86.0 percent of food items and were represented by one species of marsupial (Gracilinanus agilis) and seven species of rodents, with Calomys tener (70.9 percent) and Necromys lasiurus (6.7 percent) being the most frequent. The proportion of rodent species in barn owl pellets differed from that observed in trap samplings, with Calomys expulsus, C. tener and Oligoryzomys nigripes being consumed more frequently than expected. Although restricted to a single place and based on few individuals, the present study allowed the inventory of eight species of small mammals in Uberlândia. The comparison of the relative frequencies of rodent species in the diet and in the environment indicated selectivity. The second most preyed upon species was N. lasiurus, the main hantavirus reservoir in the Cerrado biome. In this way, the barn owl might play an important role in the control of this rodent in the region, contributing to the avoidance of a higher number of cases of hantavirus infection.

O objetivo deste estudo foi inventariar as espécies de pequenos mamíferos em Uberlândia, Minas Gerais, Brasil, com base em pelotas regurgitadas de suindara e comparar a freqüência das espécies de roedores na dieta e no ambiente. Como na região ocorre grande incidência de casos de hantavirose, também se avaliou a importância da suindara no controle de roedores que transmitem o hantavírus. Os dados de riqueza e abundância relativa de roedores no município foram fornecidos pelo Centro de Controle de Zoonoses, a partir de três amostragens semestrais com armadilhas. No total, foram encontrados 736 itens alimentares a partir da análise de 214 pelotas e fragmentos de regurgitação. Os mamíferos corresponderam a 86,0 por cento dos itens alimentares e estiveram representados por uma espécie de marsupial (Gracilinanus agilis) e sete espécies de roedores, sendo os mais freqüentes Calomys tener (70,9 por cento) e Necromys lasiurus (6,7 por cento). A proporção das espécies de roedores nas pelotas da suindara diferiu daquela observada nas coletas com armadilhas, sendo que as espécies Calomys expulsus, C. tener e Oligoryzomys nigripes foram consumidas com maior freqüência do que o esperado. Apesar de restrito a um único local e baseado em poucos indivíduos, o presente estudo permitiu inventariar oito espécies de pequenos mamíferos em Uberlândia. A comparação da freqüência relativa das espécies de roedores na dieta e no ambiente indicou a existência de seletividade. A segunda espécie mais predada foi N. lasiurus, o principal reservatório de hantavírus no bioma Cerrado. Desta forma, a suindara parece desempenhar um importante papel no controle desse roedor na região, contribuindo para evitar um maior número de casos de hantavirose.

Study of the social hierarchy and territoriality of Calomys callosus Rengger, 1830 (Rodentia: Cricetidae)

The genus Calomys comprises a lot of species distributed throughout South America. The species C. callosus Rengger, 1830 occur in Brazil, been often used in laboratory experiments. This work involved a study of aggressive behavior and dominance, which are aspects related to hierarchy and territoriality, among C. callosus males kept in a laboratory. The establishment of a hierarchy was observed, with the dominant animals controlling the space, food and water, while the remaining animals were confined to a restricted space. The intensity of aggression and variations in the number of attacks declined over time as a result of the formation of the hierarchy. No wounds were observed, probably due to the ritualistic nature of the attacks.

O genêro Calomys inclui várias espécies encontradas na América do Sul. A espécie C. callosus Rengger, 1830 ocorre no Brasil, sendo freqüentemente utilizada em experimentos de laboratório. Neste trabalho foram estudados, em machos mantidos em laboratório, o comportamento agressivo e a dominância, aspectos relacionados à hierarquia e territorialidade. Foi observado o estabelecimento de hierarquia, com os animais dominantes controlando o espaço, o alimento e a água, ficando os demais confinados em um espaço restrito. A intensidade das agressões e as variações no número de ataques diminuiram com o tempo, uma conseqüência da formação de hierarquia. Não foram observados ferimentos, devido provavelmente à ritualização dos ataques.

Study of the social hierarchy and territoriality of Calomys callosus Rengger, 1830 (Rodentia: Cricetidae)

The genus Calomys comprises a lot of species distributed throughout South America. The species C. callosus Rengger, 1830 occur in Brazil, been often used in laboratory experiments. This work involved a study of aggressive behavior and dominance, which are aspects related to hierarchy and territoriality, among C. callosus males kept in a laboratory. The establishment of a hierarchy was observed, with the dominant animals controlling the space, food and water, while the remaining animals were confined to a restricted space. The intensity of aggression and variations in the number of attacks declined over time as a result of the formation of the hierarchy. No wounds were observed, probably due to the ritualistic nature of the attacks.

O genêro Calomys inclui várias espécies encontradas na América do Sul. A espécie C. callosus Rengger, 1830 ocorre no Brasil, sendo freqüentemente utilizada em experimentos de laboratório. Neste trabalho foram estudados, em machos mantidos em laboratório, o comportamento agressivo e a dominância, aspectos relacionados à hierarquia e territorialidade. Foi observado o estabelecimento de hierarquia, com os animais dominantes controlando o espaço, o alimento e a água, ficando os demais confinados em um espaço restrito. A intensidade das agressões e as variações no número de ataques diminuiram com o tempo, uma conseqüência da formação de hierarquia. Não foram observados ferimentos, devido provavelmente à ritualização dos ataques.

Morphometric and High Resolution Scanning Electron Microscopy Study of Calomys callosus Major Palatine Nerve / Estudio Morfométrico y Electrónico de Barrido de Alta Resolución del Nervio Palatino Mayor del Calomys callosus

The characteristics of Calomys callosus major palatine nerve were studied employing light, transmission and high resolution scanning electron microscopy methods. For light microscopy, the specimens were fixed in Bouin's fixative solution, processed routinely and the sections were stained with hematoxylin­eosin and Azo-Carmin to identify nerve fibers. For high resolution scanning electron microscopy the O-D-O method reported by Tanaka (1989) was used to examine nerve fiber components and to measure the myelin sheath. Thin sections were examined by transmission electron microscopy to show axoplasmic elements and adjacent structures. The results revealed nerve fiber bundles in the lamina propria of Calomys callosus palatine mucosa. Nerve fibers were enveloped by cytoplasmic lamellae of perineural cells and adjacent collagen bundles, their diameter ranged from 1 to 6 µm, and the myelin sheath ranged from 0.2 to 0.9 µm. In the nerve fibers axoplasm were seen neurofilaments, mitochondria, neurotubules and few unmyelinated fibers.

Se estudiaron las características del nervio palatino mayor del Calomys callosus, utilizando métodos de microscopía luz y electrónica de transmisión y de barrido de alta resolución. En el caso de microscopía de luz las muestras se fijaron con solución fijadora de Bouin, se trabajaron de la forma habitual y las secciones se tiñeron con hematoxilina-eosina y con azo-carmín para identificar las fibras nerviosas. En el caso de microscopía electrónica de alta resolución se utilizó el método O-D-O indicado por Tanaka (1989) para examinar los componentes de la fibra nerviosa y medir la vaina de mielina. Se examinaron secciones finas usando microscopio electrónico de transmisión para poner en evidencia los elementos axoplásmicos y las estructuras adyacentes. Los resultados demuestran la presencia de uniones de la fibra nerviosa en la lámina palatina de la mucosa de Calomys callosus. Las fibras nerviosas están envueltas en lamelas citoplasmáticas de células perineurales y uniones de colágeno adyacente y su diámetro varía de 1 a 6µm; la vaina de mielina varía de 0.2 a 0.9 µm. En el axoplasma de las fibras nerviosas se observaron neurofilamentos, mitocondrias y neurotúbulos y se encontraron unas pocas fibras sin mielina.