The Effect of Sigmodon Hispidus on Spatial and Temporal Activity of Microtus Ochrogaster: Evidence for Competition

Spatial and temporal activities of cotton rats, Sigmodon hispidus, and prairie voles, Microtus ochrogaster, in an old-field habitat in northeast Kansas, USA were studied for 39 mo. During a major portion of the S. hispidus reproductive season the species were spatially segregated but co-occurred the rest of the year. Following a local extinction of cotton rats, prairie voles established a resident population in habitats formerly occupied by cotton rats that was greater than or equal to the vole population in areas which had never been occupied by cotton rats. Comparison of vole population size before and after the loss of cotton rats indicated that cotton rats produced a negative effect on vole population size during the period of spatial segregation but not during the period of spatial co-occurrence. Comparison of vole activity patterns indicated that, with the loss of cotton rats, voles shifted their activity during times when the species had co-occurred but not during periods when they were spatially segregated. Studies of behavioral interactions in a large (4 m x 4 m) arena with varying densities of vertical wires indicated that during single species tests voles and cotton rats preferred the densest areas. Their diel activity patterns were broadly overlapping. In the presence of nonreproductive cotton rats, voles continued to use the same areas as during the control tests but shifted their temporal activity reducing overlap with cotton rats. Interspecific encounters resujted in voles avoiding cotton rats even in the absence of overt aggression. In the presence of reproductive cotton rats, voles shifted their arena usage toward areas least used by cotton rats. Total nocturnal activity by voles was the same as during the control tests but was restricted to hours when cotton rats were least active. Reproductive cotton rats showed higher levels of interspecific aggression than did nonreproductive cotton rats. Voles in the presence of reproductive cotton rats showed increased frequency of serious wounds and deaths, and decreased mass when compared to voles in the presence of nonreproductive cotton rats. We conclude that cotton rats produce a negative effect on prairie vole populations but that the interaction is restricted to the cotton rats' reproductive season. Coexistence of the species appears to rely on the seasonality of the interaction, habitat heterogeneity, and the wider habitat tolerance of prairie voles

High-resolution spatiotemporal weather models for climate studies

<p>Abstract</p> <p>Background</p> <p>Climate may exert a strong influence on health, in particular on vector-borne infectious diseases whose vectors are intrinsically dependent on their environment. Although critical, linking climate variability to health outcomes is a difficult task. For some diseases in some areas, spatially and temporally explicit surveillance data are available, but comparable climate data usually are not. We utilize spatial models and limited weather observations in Puerto Rico to predict weather throughout the island on a scale compatible with the local dengue surveillance system.</p> <p>Results</p> <p>We predicted monthly mean maximum temperature, mean minimum temperature, and cumulative precipitation at a resolution of 1,000 meters. Average root mean squared error in cross-validation was 1.24°C for maximum temperature, 1.69°C for minimum temperature, and 62.2 millimeters for precipitation.</p> <p>Conclusion</p> <p>We present a methodology for efficient extrapolation of minimal weather observation data to a more meaningful geographical scale. This analysis will feed downstream studies of climatic effects on dengue transmission in Puerto Rico. Additionally, we utilize conditional simulation so that model error may be robustly passed to future analyses.</p

Induction of Winter Breeding in Small Mammals by 6-MBOA

A plant-derived cyclic carbamate, 6-methoxybenzoxazolinone (6-MBOA), is known to initiate reproductive activity in Microtus montanus. We studied overwintering populations of four other rodent species, and observed increased reproduction in experimental populations of two herbivorous species, Microtus pennsylvanicus and Sigmodon hispidus, but not in two omnivorous species, Oryzomys palustris and Mus musculus. These results suggest that low concentrations of 6-MBOA may trigger seasonal breeding primarily in herbivorous small mammals

Identifying malaria vector breeding habitats with remote sensing data and terrain-based landscape indices in Zambia

<p>Abstract</p> <p>Background</p> <p>Malaria, caused by the parasite <it>Plasmodium falciparum</it>, is a significant source of morbidity and mortality in southern Zambia. In the Mapanza Chiefdom, where transmission is seasonal, <it>Anopheles arabiensis </it>is the dominant malaria vector. The ability to predict larval habitats can help focus control measures.</p> <p>Methods</p> <p>A survey was conducted in March-April 2007, at the end of the rainy season, to identify and map locations of water pooling and the occurrence anopheline larval habitats; this was repeated in October 2007 at the end of the dry season and in March-April 2008 during the next rainy season. Logistic regression and generalized linear mixed modeling were applied to assess the predictive value of terrain-based landscape indices along with LandSat imagery to identify aquatic habitats and, especially, those with anopheline mosquito larvae.</p> <p>Results</p> <p>Approximately two hundred aquatic habitat sites were identified with 69 percent positive for anopheline mosquitoes. Nine species of anopheline mosquitoes were identified, of which, 19% were <it>An. arabiensis</it>. Terrain-based landscape indices combined with LandSat predicted sites with water, sites with anopheline mosquitoes and sites specifically with <it>An. arabiensis</it>. These models were especially successful at ruling out potential locations, but had limited ability in predicting which anopheline species inhabited aquatic sites. Terrain indices derived from 90 meter Shuttle Radar Topography Mission (SRTM) digital elevation data (DEM) were better at predicting water drainage patterns and characterizing the landscape than those derived from 30 m Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEM.</p> <p>Conclusions</p> <p>The low number of aquatic habitats available and the ability to locate the limited number of aquatic habitat locations for surveillance, especially those containing anopheline larvae, suggest that larval control maybe a cost-effective control measure in the fight against malaria in Zambia and other regions with seasonal transmission. This work shows that, in areas of seasonal malaria transmission, incorporating terrain-based landscape models to the planning stages of vector control allows for the exclusion of significant portions of landscape that would be unsuitable for water to accumulate and for mosquito larvae occupation. With increasing free availability of satellite imagery such as SRTM and LandSat, the development of satellite imagery-based prediction models is becoming more accessible to vector management coordinators.</p

Determining Matrilines by Antibody Response to Exotic Antigens

The antibody responses of female Microtuspennsylvanicus inoculated with a series of antigens not normally encountered under field conditions were examined, and the kinetics of maternally acquired antibody loss in their offspring were determined. The initial antibody response in adults was rapid, peaking in 4-9 weeks, and long-lasting, with a half life of 4-5 months. Antibody levels in females were unaffected by parity, and more than one antigen could be given without affecting circulating-antibody titers. Antibody titers could be enhanced with additional inoculations. Maternal antibody in offspring increased until weaning at 3 weeks then declined exponentially. Minimal detectable titers were reached at 7-11 weeks. In many instances, maternal antibody remained detectable even after offspring reached adult (35 g) size. Examination of uninoculated wild-caught voles showed only one of 130 tests produced a false positive response. The exotic-antigen technique may be generally applicable for determining maternity in small, secretive mammals

Dietary Habits of the Common Rodents in an Agrecosystem in Argentina

Dietary habits of five common rodents in agroecosystems on the central Argentine Pampa were studied for 15 months using microhistological analysis of stomach contents. All five rodent species were omnivorous, but proportions of major dietary items (arthropods, dicot leaves and seeds, monocot leaves and seeds) varied among species and seasons. Akodon azarae largely was entomophagous; arthropods formed 41-62% of the diet in all seasons. The other four species (Calomys musculinus, Calomys laucha, Bolomys obscurus, and Oligoryzomys flavescens) consumed most diet items throughout the year, but relative proportions varied among seasons. Leaves formed a relatively minor proportion of the diet (12- 16% overall for all species) throughout the year. All species except A. azarae consumed higher quantities of seeds (50-73% of stomach volume) than arthropods (15-35%) during autumn and winter but switched to higher quantities of arthropods (30-53%) in spring and summer. Diet breadth was narrower and overlap generally highest during winter when all species were forced to subsist on a reduced set of available resources. Of 28 plant species with \u3e2% cover in the environment, 25 were identified in stomachs of one or more of the five rodent species. The most important plant species in the diet were corn and soybeans (mostly grain), seed of Johnson grass (Sorghum halepense), chickweed (Stellaria media), and Amaranthus. High consumption of arthropods, especially by A. azarae, contraindicates the broad-scale use of rodenticides until the role of that rodent species in the control of pest insects can be ascertained

Dietary Habits of the Common Rodents in an Agrecosystem in Argentina

Dietary habits of five common rodents in agroecosystems on the central Argentine Pampa were studied for 15 months using microhistological analysis of stomach contents. All five rodent species were omnivorous, but proportions of major dietary items (arthropods, dicot leaves and seeds, monocot leaves and seeds) varied among species and seasons. Akodon azarae largely was entomophagous; arthropods formed 41-62% of the diet in all seasons. The other four species (Calomys musculinus, Calomys laucha, Bolomys obscurus, and Oligoryzomys flavescens) consumed most diet items throughout the year, but relative proportions varied among seasons. Leaves formed a relatively minor proportion of the diet (12- 16% overall for all species) throughout the year. All species except A. azarae consumed higher quantities of seeds (50-73% of stomach volume) than arthropods (15-35%) during autumn and winter but switched to higher quantities of arthropods (30-53%) in spring and summer. Diet breadth was narrower and overlap generally highest during winter when all species were forced to subsist on a reduced set of available resources. Of 28 plant species with \u3e2% cover in the environment, 25 were identified in stomachs of one or more of the five rodent species. The most important plant species in the diet were corn and soybeans (mostly grain), seed of Johnson grass (Sorghum halepense), chickweed (Stellaria media), and Amaranthus. High consumption of arthropods, especially by A. azarae, contraindicates the broad-scale use of rodenticides until the role of that rodent species in the control of pest insects can be ascertained

Progress and challenges to control malaria in a remote area of Chittagong hill tracts, Bangladesh

<p>Abstract</p> <p>Background</p> <p>Malaria is endemic in 13 eastern districts where the overall infection prevalence is 3.97%. In 2006, Bangladesh received US$ 36.9 million from the Global Fund to Fight AIDS, Tuberculosis and Malaria (GFATM) to support the national malaria control programme of Bangladesh.</p> <p>Objectives</p> <p>The objective of this study was to i) clarify factors associated with treatment seeking behaviours of malaria ii) distribution of LLIN, and iii) re-treatment of ITN in remote area of a CHT district of Bangladesh two years after implementation of national control programme.</p> <p>Methods</p> <p>All households of Rajasthali sub-district of Rangamati district (households about 5,322, population about 24,097), all BRAC health workers (n = 15), health facilities and drug vendors' locations were mapped. Distances from households to health facilities, BRAC health workers and drug vendors were calculated. Logistic regression analysis was performed to assess the associations between the choice of the treatment and the distance to various treatment sources, education, occupation and ethnicity. SaTScan was used to detect clustering of treatment-seeking approaches.</p> <p>Findings</p> <p>LLIN distribution and the re-treatment of ITN exceeded target goals. The most common treatment facility for malaria-associated fever was malaria control programme led by BRAC and government (66.6%) followed by the drug vendor (48.8%).</p> <p>Conclusion</p> <p>Closeness to health facilities run by the malaria control programme and drug vendors were significantly associated with the choice of treatment. A high proportion of people preferred drug vendors without having a proper diagnosis. Drug vendors are highly patronized and thus there is a need to improve their services for public health good. Otherwise it may cause incomplete treatment, misuse of anti-malarial drugs that will contribute to the risk of drug resistance and jeopardize the present malaria control efforts in Bangladesh.</p