Spatial-Temporal Distribution of Hantavirus Rodent-Borne Infection by <i>Oligoryzomys fulvescens</i> in the Agua Buena Region - Panama

<div><p>Background</p><p>Hotspot detection and characterization has played an increasing role in understanding the maintenance and transmission of zoonotic pathogens. Identifying the specific environmental factors (or their correlates) that influence reservoir host abundance help increase understanding of how pathogens are maintained in natural systems and are crucial to identifying disease risk. However, most recent studies are performed at macro-scale and describe broad temporal patterns of population abundances. Few have been conducted at a microscale over short time periods that better capture the dynamical patterns of key populations. These finer resolution studies may better define the likelihood of local pathogen persistence. This study characterizes the landscape distribution and spatio-temporal dynamics of <i>Oligoryzomys fulvescens</i> (<i>O</i>. <i>fulvescens</i>), an important mammalian reservoir in Central America.</p><p>Methods</p><p>Information collected in a longitudinal study of rodent populations in the community of Agua Buena in Tonosí, Panama, between April 2006 and December 2009 was analyzed using non-spatial analyses (box plots) and explicit spatial statistical tests (correlograms, SADIE and LISA). A 90 node grid was built (raster format) to design a base map. The area between the nodes was 0.09 km² and the total study area was 6.43 km² (2.39 x 2.69 km). The temporal assessment dataset was divided into four periods for each year studied: the dry season, rainy season, and two months-long transitions between seasons (the months of April and December).</p><p>Results</p><p>There were heterogeneous patterns in the population densities and degrees of dispersion of <i>O</i>. <i>fulvescens</i> that varied across seasons and among years. The species typically was locally absent during the late transitional months of the season, and re-established locally in subsequent years. These populations re-occurred in the same area during the first three years but subsequently re-established further south in the final year of the study. Spatial autocorrelation analyses indicated local populations encompassed approximately 300–600 m. The borders between suitable and unsuitable habitats were sharply demarcated over short distances.</p><p>Conclusion</p><p><i>Oligoryzomys fulvescens</i> showed a well-defined spatial pattern that evolved over time, and led to a pattern of changing aggregation. Thus, hot spots of abundance showed a general shifting pattern that helps explain the intermittent risk from pathogens transmitted by this species. This variation was associated with seasonality, as well as anthropogenic pressures that occurred with agricultural activities. These factors help define the characteristics of the occurrence, timing, intensity and duration of synanthropic populations affected by human populations and, consequently, possible exposure that local human populations experience.</p></div

Summary of SADIE analyses, in Agua Buena, Panamá, 2006–2009.

<p>Summary of SADIE analyses, in Agua Buena, Panamá, 2006–2009.</p

Map of study area in Agua Buena, Tonosí.

<p>Map of study area in Agua Buena, Tonosí.</p

LISA distribution of <i>Oligoryzomys fulvescens</i> by season, in Agua Buena, Panama, 2006–2009.

<p>LISA distribution of <i>Oligoryzomys fulvescens</i> by season, in Agua Buena, Panama, 2006–2009.</p

Moran’s I correlograms of <i>Oligoryzomys fulvescens</i> by season, in Agua Buena, Panama, April, 2006–December, 2009.

<p>Moran’s I correlograms of <i>Oligoryzomys fulvescens</i> by season, in Agua Buena, Panama, April, 2006–December, 2009.</p

Map of the spatial distribution of <i>Oligoryzomys fulvescens</i> by season, in Agua Buena, Panama, 2006–2009.

<p>Map of the spatial distribution of <i>Oligoryzomys fulvescens</i> by season, in Agua Buena, Panama, 2006–2009.</p

Efficiency of Household Reactive Case Detection for Malaria in Rural Southern Zambia: Simulations Based on Cross-Sectional Surveys from Two Epidemiological Settings

<div><p>Background</p><p>Case detection and treatment are critical to malaria control and elimination as infected individuals who do not seek medical care can serve as persistent reservoirs for transmission.</p><p>Methods</p><p>Household malaria surveys were conducted in two study areas within Southern Province, Zambia in 2007 and 2008. Cross-sectional surveys were conducted approximately five times throughout the year in each of the two study areas. During study visits, adults and caretakers of children were administered a questionnaire and a blood sample was obtained for a rapid diagnostic test (RDT) for malaria. These data were used to estimate the proportions of individuals with malaria potentially identified through passive case detection at health care facilities and those potentially identified through reactive case finding. Simulations were performed to extrapolate data from sampled to non-sampled households. Radii of increasing size surrounding households with an index case were examined to determine the proportion of households with an infected individual that would be identified through reactive case detection.</p><p>Results</p><p>In the 2007 high transmission setting, with a parasite prevalence of 23%, screening neighboring households within 500 meters of an index case could have identified 89% of all households with an RDT positive resident and 90% of all RDT positive individuals. In the 2008 low transmission setting, with a parasite prevalence of 8%, screening neighboring households within 500 meters of a household with an index case could have identified 77% of all households with an RDT positive resident and 76% of all RDT positive individuals.</p><p>Conclusions</p><p>Testing and treating individuals residing within a defined radius from an index case has the potential to be an effective strategy to identify and treat a large proportion of infected individuals who do not seek medical care, although the efficiency of this strategy is likely to decrease with declining parasite prevalence.</p></div

Study flow diagram for 2007 and 2008/2009.

<p>HH: household.</p

Participant characteristics at the initial study visit by year.

<p>ITN: insecticide-treated net.</p>a<p>Symptoms included fever, chills, headache, diarrhea, cough, nausea/vomiting.</p>b<p>Comparison of cross-sectional and longitudinal participants using the chi-square test for binary characteristics and the Wilcoxon ranksum test for continuous characteristics.</p

<i>Oligoryzomys fulvescens</i> distribution by season (Dry, rainy, and transitional) and year using Box-Plot in Agua Buena, Panama, April 2006-December 2009.

<p><i>Oligoryzomys fulvescens</i> distribution by season (Dry, rainy, and transitional) and year using Box-Plot in Agua Buena, Panama, April 2006-December 2009.</p