Oviposition Site Selection by the Dengue Vector Aedes aegypti and Its Implications for Dengue Control

Controlling the mosquito Aedes aegypti is of public health importance because, at present, it is the only means to stop dengue virus transmission. Implementing successful mosquito control programs requires understanding what factors regulate population abundance, as well as anticipating how mosquitoes may adapt to control measures. In some species of mosquitoes, females choose egg-laying sites to improve the survival and growth of their offspring, a behavior that ultimately influences population distribution and abundance. In the current study, we tested whether Ae. aegypti actively choose the containers in which they lay their eggs and determined what cues are most relevant to that process. We also explored whether females select containers that provide the most food for their larval progeny. Surprisingly, egg-laying females were most attracted to sites containing other immature Ae. aegypti, rather than to sites containing the most food. We propose that this behavior may contribute to density-dependent competition for food among larvae and play a larger role than previously thought in regulating Ae. aegypti populations. We recommend that accounting for, and even taking advantage of, this natural behavior will lead to more effective strategies for dengue prevention

Risk Factors for Tungiasis in Nigeria: Identification of Targets for Effective Intervention

Tungiasis is a parasitic skin disease caused by the sand flea Tunga penetrans. After penetration into the skin, the flea grows and reaches the size of a pea. The disease is a neglected public health problem in endemic areas in Latin America, the Caribbean and Africa, and causes considerable morbidity in the affected communities. We performed a study in a rural community in Nigeria to detect factors associated with tungiasis. People were examined for the presence of sand flea lesions, and a questionnaire was applied. Of the 643 individuals examined, 252 (42.5%) had tungiasis. The most important factors independently associated with the disease were: presence of pigs on the compound (adjusted odds ratio [OR] = 17.98), sand or clay floor inside house (OR = 9.33), and having the common resting place outside the house (OR = 7.14). The regular use of closed footwear (OR = 0.34) and the use of insecticides indoors (OR = 0.2) were protective factors. Our data show that tungiasis in this community is determined to an important extent by some variables that may be a target for interventions

Control of Tungiasis through Intermittent Application of a Plant-Based Repellent: An Intervention Study in a Resource-Poor Community in Brazil

Tungiasis is a parasitic skin disease caused by the female sand flea Tunga penetrans. The disease is frequent in resource-poor communities in South America and sub-Saharan Africa and affects the poorest of the poor. Sand flea disease is associated with a considerable morbidity and may lead to tetanus in non-vaccinated individuals. The degree of morbidity depends on the intensity of infestation, i.e., the number of embedded sand fleas a person has. Since tungiasis is a zoonosis involving a host of animal reservoirs, and because an effective treatment is not at hand, in resource-poor settings elimination is not feasible. Preventing morbidity to develop is therefore the only means to protect exposed individuals from sand flea disease. Similar to other arthropods, sand fleas can be repelled before they penetrate into the skin. In this study we show that the intermittent application of a plant-based repellent, of which the major component is coconut oil, reduces the intensity of infestation dramatically during the whole transmission season and prevents tungiasis-associated morbidity from developing. The prevention can be performed at the household level by the affected individuals themselves with minimal input from the health sector

Controlling Tungiasis in an Impoverished Community: An Intervention Study

Tungiasis is a disease caused by the sand flea Tunga penetrans, a parasite prevalent in many impoverished communities in developing countries. The female sand flea penetrates into the skin of animals and humans where it grows rapidly in size, feeds on the host's blood, produces eggs which are expelled into the environment, and eventually dies in situ. The lesions become frequently superinfected and the infestation is associated with considerable morbidity. Clearly, tungiasis is a neglected disease of neglected populations. We investigated the impact of a package of intervention measures targeted against on-host and off-host stages of T. penetrans in a fishing community in Northeast Brazil. These measures decreased disease occurrence only temporarily, but had a sustained effect on the intensity of the infestation. Since infestation intensity and morbidity are correlated, presumably the intervention also lowered tungiasis-associated morbidity. Control measures similar to the ones used in this study may help to effectively control tungiasis in impoverished communities

Determinants of FDI flows to developing economies: evidence from Malaysia

The paper reviews the literature identifying the determinants of the FDI flows to developing countries and attempts to lay bare the theories that underlie them.Asimple regression model is set up to assess the role of the identified determinants in the case of Malsysia.Causality tests indicate that over the range of regression rate of exchange, exports, Infrastructure expansion and rate of growth have been significant factors in that order. All have led the FDI flows; the reverse is not true