Spatially clustered count data provide more efficient search strategies in invasion biology and disease control.

Geographic profiling, a mathematical model originally developed in criminology, is increasingly being used in ecology and epidemiology. Geographic profiling boasts a wide range of applications, such as finding source populations of invasive species or breeding sites of vectors of infectious disease. The model provides a cost-effective approach for prioritising search strategies for source locations and does so via simple data in the form of the positions of each observation, such as individual sightings of invasive species or cases of a disease. In doing so, however, classic geographic profiling approaches fail to make the distinction between those areas containing observed absences and those areas where no data were recorded. Absence data are generated via spatial sampling protocols but are often discarded during the inference process. Here we construct a geographic profiling model that resolves these issues by making inferences via count data - analysing a set of discrete sentinel locations at which the number of encounters has been recorded. Crucially, in our model this number can be zero. We verify the ability of this new model to estimate source locations and other parameters of practical interest via a Bayesian power analysis. We also measure model performance via real-world data in which the model infers breeding locations of mosquitoes in bromeliads in Miami-Dade County, Florida. In both cases, our novel model produces more efficient search strategies by shifting focus from those areas containing observed absences to those with no data, an improvement over existing models that treat these areas equally. Our model makes important improvements upon classic geographic profiling methods, which will significantly enhance real-world efforts to develop conservation management plans and targeted interventions

Mosquito Abundance, Bed net Coverage and Other Factors Associated with Variations in Sporozoite Infectivity Rates in Four Villages of Rural Tanzania.

Entomological surveys are of great importance in decision-making processes regarding malaria control strategies because they help to identify associations between vector abundance both species-specific ecology and disease intervention factors associated with malaria transmission. Sporozoite infectivity rates, mosquito host blood meal source, bed net coverage and mosquito abundance were assessed in this study. A longitudinal survey was conducted in four villages in two regions of Tanzania. Malaria vectors were sampled using the CDC light trap and pyrethrum spray catch methods. In each village, ten paired houses were selected for mosquitoes sampling. Sampling was done in fortnight case and study was undertaken for six months in both Kilimanjaro (Northern Tanzania) and Dodoma (Central Tanzania) regions. A total of 6,883 mosquitoes were collected including: 5,628 (81.8%) Anopheles arabiensis, 1,100 (15.9%) Culex quinquefasciatus, 89 (1.4%) Anopheles funestus, and 66 (0.9%) Anopheles gambiae s.s. Of the total mosquitoes collected 3,861 were captured by CDC light trap and 3,022 by the pyrethrum spray catch method. The overall light trap: spray catch ratio was 1.3:1. Mosquito densities per room were 96.5 and 75.5 for light trap and pyrethrum spray catch respectively. Mosquito infectivity rates between villages that have high proportion of bed net owners and those without bed nets was significant (P < 0.001) and there was a significant difference in sporozoite rates between households with and without bed nets in these four villages (P < 0.001). Malaria remains a major problem in the study areas characterized as low transmission sites. Further studies are required to establish the annual entomological inoculation rates and to observe the annual parasitaemia dynamics in these communities. Outdoor mosquitoes collection should also be considered

Comparative Field Evaluation of Combinations of Long-Lasting Insecticide Treated Nets and Indoor Residual Spraying, Relative to Either Method Alone, for Malaria Prevention in an Area where the main Vector is Anopheles Arabiensis.

Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are commonly used together in the same households to improve malaria control despite inconsistent evidence on whether such combinations actually offer better protection than nets alone or IRS alone. Comparative tests were conducted using experimental huts fitted with LLINs, untreated nets, IRS plus untreated nets, or combinations of LLINs and IRS, in an area where Anopheles arabiensis is the predominant malaria vector species. Three LLIN types, Olyset®, PermaNet 2.0® and Icon Life® nets and three IRS treatments, pirimiphos-methyl, DDT, and lambda cyhalothrin, were used singly or in combinations. We compared, number of mosquitoes entering huts, proportion and number killed, proportions prevented from blood-feeding, time when mosquitoes exited the huts, and proportions caught exiting. The tests were done for four months in dry season and another six months in wet season, each time using new intact nets. All the net types, used with or without IRS, prevented >99% of indoor mosquito bites. Adding PermaNet 2.0® and Icon Life®, but not Olyset® nets into huts with any IRS increased mortality of malaria vectors relative to IRS alone. However, of all IRS treatments, only pirimiphos-methyl significantly increased vector mortality relative to LLINs alone, though this increase was modest. Overall, median mortality of An. arabiensis caught in huts with any of the treatments did not exceed 29%. No treatment reduced entry of the vectors into huts, except for marginal reductions due to PermaNet 2.0® nets and DDT. More than 95% of all mosquitoes were caught in exit traps rather than inside huts. Where the main malaria vector is An. arabiensis, adding IRS into houses with intact pyrethroid LLINs does not enhance house-hold level protection except where the IRS employs non-pyrethroid insecticides such as pirimiphos-methyl, which can confer modest enhancements. In contrast, adding intact bednets onto IRS enhances protection by preventing mosquito blood-feeding (even if the nets are non-insecticidal) and by slightly increasing mosquito mortality (in case of LLINs). The primary mode of action of intact LLINs against An. arabiensis is clearly bite prevention rather than insecticidal activity. Therefore, where resources are limited, priority should be to ensure that everyone at risk consistently uses LLINs and that the nets are regularly replaced before being excessively torn. Measures that maximize bite prevention (e.g. proper net sizes to effectively cover sleeping spaces, stronger net fibres that resist tears and burns and net use practices that preserve net longevity), should be emphasized

False positive circumsporozoite protein ELISA: a challenge for the estimation of the entomological inoculation rate of malaria and for vector incrimination

<p>Abstract</p> <p>Background</p> <p>The entomological inoculation rate (EIR) is an important indicator in estimating malaria transmission and the impact of vector control. To assess the EIR, the enzyme-linked immunosorbent assay (ELISA) to detect the circumsporozoite protein (CSP) is increasingly used. However, several studies have reported false positive results in this ELISA. The false positive results could lead to an overestimation of the EIR. The aim of present study was to estimate the level of false positivity among different anopheline species in Cambodia and Vietnam and to check for the presence of other parasites that might interact with the anti-CSP monoclonal antibodies.</p> <p>Methods</p> <p>Mosquitoes collected in Cambodia and Vietnam were identified and tested for the presence of sporozoites in head and thorax by using CSP-ELISA. ELISA positive samples were confirmed by a <it>Plasmodium </it>specific PCR. False positive mosquitoes were checked by PCR for the presence of parasites belonging to the Haemosporidia, Trypanosomatidae, Piroplasmida, and Haemogregarines. The heat-stability and the presence of the cross-reacting antigen in the abdomen of the mosquitoes were also checked.</p> <p>Results</p> <p>Specimens (N = 16,160) of seven anopheline species were tested by CSP-ELISA for <it>Plasmodium falciparum </it>and <it>Plasmodium vivax </it>(Pv210 and Pv247). Two new vector species were identified for the region: <it>Anopheles pampanai </it>(<it>P. vivax</it>) and <it>Anopheles barbirostris </it>(<it>Plasmodium malariae</it>). In 88% (155/176) of the mosquitoes found positive with the <it>P. falciparum </it>CSP-ELISA, the presence of <it>Plasmodium </it>sporozoites could not be confirmed by PCR. This percentage was much lower (28% or 5/18) for <it>P. vivax </it>CSP-ELISAs. False positive CSP-ELISA results were associated with zoophilic mosquito species. None of the targeted parasites could be detected in these CSP-ELISA false positive mosquitoes. The ELISA reacting antigen of <it>P. falciparum </it>was heat-stable in CSP-ELISA true positive specimens, but not in the false positives. The heat-unstable cross-reacting antigen is mainly present in head and thorax and almost absent in the abdomens (4 out of 147) of the false positive specimens.</p> <p>Conclusion</p> <p>The CSP-ELISA can considerably overestimate the EIR, particularly for <it>P. falciparum </it>and for zoophilic species. The heat-unstable cross-reacting antigen in false positives remains unknown. Therefore it is highly recommended to confirm all positive CSP-ELISA results, either by re-analysing the heated ELISA lysate (100°C, 10 min), or by performing <it>Plasmodium </it>specific PCR followed if possible by sequencing of the amplicons for <it>Plasmodium </it>species determination.</p

Plasmodium falciparum transmission and aridity: a Kenyan experience from the dry lands of Baringo and its implications for Anopheles arabiensis control

<p>Abstract</p> <p>Background</p> <p>The ecology of malaria vectors particularly in semi-arid areas of Africa is poorly understood. Accurate knowledge on this subject will boost current efforts to reduce the burden of malaria in sub-Saharan Africa. The objective of this study was to describe the dynamics of malaria transmission in two model semi-arid sites (Kamarimar and Tirion) in Baringo in Kenya.</p> <p>Methods</p> <p>Adult mosquitoes were collected indoors by pyrethrum spray collections (PSC) and outdoors by Centers for Disease Control (CDC) light traps and identified to species by morphological characteristics. Sibling species of <it>Anopheles gambiae </it>complex were further characterized by rDNA. PCR and enzyme-linked immuno-sorbent assays (ELISA) were used to test for <it>Plasmodium falciparum </it>circumsporozoite proteins and host blood meal sources respectively.</p> <p>Results</p> <p><it>Anopheles arabiensis </it>was not only the most dominant mosquito species in both study sites but also the only sibling species of <it>An. gambiae s.l. </it>present in the area. Other species identified in the study area were <it>Anopheles funestus</it>, <it>Anopheles pharoensis </it>and <it>Anopheles coustani</it>. For Kamarimar but not Tirion, the human blood index (HBI) for light trap samples was significantly higher than for PSC samples (Kamarimar, 0.63 and 0.11, Tirion, 0.48 and 0.43). The HBI for light trap samples was significantly higher in Kamarimar than in Tirion while that of PSC samples was significantly higher in Tirion than in Kamarimar. Entomological inoculation rates (EIR) were only detected for one month in Kamarimar and 3 months in Tirion. The number of houses in a homestead, number of people sleeping in the house, quality of the house, presence or absence of domestic animals, and distance to the animal shelter and the nearest larval habitat were significant predictors of <it>An. arabiensis </it>occurrence.</p> <p>Conclusion</p> <p>Malaria transmission in the study area is seasonal with <it>An. arabiensis </it>as the dominant vector. The fact this species feeds readily on humans and domestic animals suggest that zooprophylaxis may be a plausible malaria control strategy in semi-arid areas of Africa. The results also suggest that certain household characteristics may increase the risk of malaria transmission.</p

The impact of low erythrocyte density in human blood on the fitness and energetic reserves of the African malaria vector Anopheles gambiae

Background Anaemia is a common health problem in the developing world. This condition is characterized by a reduction in erythrocyte density, primarily from malnutrition and/or infectious diseases such as malaria. As red blood cells are the primary source of protein for haematophagous mosquitoes, any reduction could impede the ability of mosquito vectors to transmit malaria by influencing their fitness or that of the parasites they transmit. The aim of this study was to determine the impact of differences in the density of red blood cells in human blood on malaria vector (Anopheles gambiae sensu stricto) fitness. The hypotheses tested are that mosquito vector energetic reserves and fitness are negatively influenced by reductions in the red cell density of host human blood meals commensurate with those expected from severe anaemia. Methods Mosquitoes (An. gambiae s.s.) were offered blood meals of different packed cell volume(PCV) of human blood consistent with those arising from severe anaemia (15%) and normalPCV (50%). Associations between mosquito energetic reserves (lipid, glucose and glycogen)and fitness measures (reproduction and survival) and blood meal PCV were investigated. Results The amount of protein that malaria vectors acquired from blood feeding (indexed by haematin excretion) was significantly reduced at low blood PCV. However, mosquitoes feeding on blood of low PCV had the same oviposition rates as those feeding on blood of normal PCV, and showed an increase in egg production of around 15%. The long-term survival of An. gambiae s.s was reduced after feeding on low PCV blood, but PCV had no significant impact on the proportion of mosquitoes surviving through the minimal period required to develop and transmit malaria parasites (estimated as 14 days post-blood feeding). The impact of blood PCV on the energetic reserves of mosquitoes was relatively minor. Conclusions These results suggest that feeding on human hosts whose PCV has been depleted due to severe anaemia does not significantly reduce the fitness or transmission potential of malaria vectors, and indicates that mosquitoes may be able exploit resources for reproduction more efficiently from blood of low rather than normal PCV

Prevalence of anopheline species and their Plasmodium infection status in epidemic-prone border areas of Bangladesh

<p>Abstract</p> <p>Background</p> <p>Information related to malaria vectors is very limited in Bangladesh. In the changing environment and various <it>Anopheles </it>species may be incriminated and play role in the transmission cycle. This study was designed with an intention to identify anopheline species and possible malaria vectors in the border belt areas, where the malaria is endemic in Bangladesh.</p> <p>Methods</p> <p><it>Anopheles </it>mosquitoes were collected from three border belt areas (Lengura, Deorgachh and Matiranga) during the peak malaria transmission season (May to August). Three different methods were used: human landing catches, resting collecting by mouth aspirator and CDC light traps. Enzyme-linked immunosorbent assay (ELISA) was done to detect <it>Plasmodium falciparum</it>, <it>Plasmodium vivax</it>-210 and <it>Plasmodium vivax</it>-247 circumsporozoite proteins (CSP) from the collected female species.</p> <p>Results</p> <p>A total of 634 female <it>Anopheles </it>mosquitoes belonging to 17 species were collected. <it>Anopheles vagus </it>(was the dominant species (18.6%) followed by <it>Anopheles nigerrimus </it>(14.5%) and <it>Anopheles philippinensis </it>(11.0%). Infection rate was found 2.6% within 622 mosquitoes tested with CSP-ELISA. Eight (1.3%) mosquitoes belonging to five species were positive for <it>P. falciparum</it>, seven (1.1%) mosquitoes belonging to five species were positive for <it>P. vivax </it>-210 and a single mosquito (0.2%) identified as <it>Anopheles maculatus </it>was positive for <it>P. vivax</it>-247. No mixed infection was found. Highest infection rate was found in <it>Anopheles karwari </it>(22.2%) followed by <it>An. maculatus </it>(14.3%) and <it>Anopheles barbirostris </it>(9.5%). Other positive species were <it>An. nigerrimus </it>(4.4%), <it>An. vagus </it>(4.3%), <it>Anopheles subpictus </it>(1.5%) and <it>An. philippinensis </it>(1.4%). <it>Anopheles vagus </it>and <it>An. philippinensis </it>were previously incriminated as malaria vector in Bangladesh. In contrast, <it>An. karwari</it>, <it>An. maculatus</it>, <it>An. barbirostris</it>, <it>An. nigerrimus </it>and <it>An. subpictus </it>had never previously been incriminated in Bangladesh.</p> <p>Conclusion</p> <p>Findings of this study suggested that in absence of major malaria vectors there is a possibility that other <it>Anopheles </it>species may have been playing role in malaria transmission in Bangladesh. Therefore, further studies are required with the positive mosquito species found in this study to investigate their possible role in malaria transmission in Bangladesh.</p

Cosmogenic neutron production at the Sudbury Neutrino Observatory

Neutrons produced in nuclear interactions initiated by cosmic-ray muons present an irreducible background to many rare-event searches, even in detectors located deep underground. Models for the production of these neutrons have been tested against previous experimental data, but the extrapolation to deeper sites is not well understood. Here we report results from an analysis of cosmogenically produced neutrons at the Sudbury Neutrino Observatory. A specific set of observables are presented, which can be used to benchmark the validity of geant4 physics models. In addition, the cosmogenic neutron yield, in units of 10-4 cm2/(g·μ), is measured to be 7.28±0.09(stat)-1.12+1.59(syst) in pure heavy water and 7.30±0.07(stat)-1.02+1.40(syst) in NaCl-loaded heavy water. These results provide unique insights into this potential background source for experiments at SNOLAB

Comparison of two different models for pile thermal response test interpretation

Thermal response tests (TRTs) are regularly used to characterise the thermal resistance of borehole heat exchangers and to assess the thermal conductivity of the surrounding ground. It is becoming common to apply the same in situ testing technique to pile heat exchangers, despite international guidance suggesting that TRTs should be limited to hole diameters of 152 mm (6 in.). This size restriction arises from the increased thermal inertia of larger diameter heat exchangers, which invalidates the assumption of a steady state within the concrete needed to interpret the test data by traditional line source analysis techniques. However, new methods of analysis for pile heat exchangers have recently been developed that take account of the transient behaviour of the pile concrete. This paper applies these new methods to data from a multi-stage TRT conducted on a small diameter test pile. The thermal conductivity and thermal resistance determined using this method are then compared with those from traditional analytical approaches based on a line source analysis. Differences between the approaches are discussed, along with the observation that the thermal resistance may not be constant over the different test stages