Long-term trends and spatial patterns of West Nile Virus emergence in California, 2004-2021

AIMS

West Nile Virus (WNV) has remained a persistent source of vector-borne disease risk in California since first being identified in the state in 2003. The geographic distribution of WNV activity is relatively widespread, but varies considerably across different regions within the state. Spatial variation in human WNV infection depends upon social-ecological factors that influence mosquito populations and virus transmission dynamics. Measuring changes in spatial patterns over time is necessary for uncovering the underlying regional drivers of disease risk.

METHODS AND RESULTS

In this study, we utilized statewide surveillance data to quantify temporal changes and spatial patterns of WNV activity in California. We obtained annual WNV mosquito surveillance data from 2004 through 2021 from the California Arbovirus Surveillance Program. Geographic coordinates for mosquito pools were analysed using a suite of spatial statistics to identify and classify patterns in WNV activity over time.

CONCLUSIONS

We detected clear patterns of non-random WNV risk during the study period, including emerging hot spots in the Central Valley and non-random periods of oscillating WNV risk in Southern and Northern California subregions. Our findings offer new insights into 18 years of spatio-temporal variation in WNV activity across California, which may be used for targeted surveillance efforts and public health interventions.

Synergistic Repellent and Irritant Effects of a Mixture of β-Caryophyllene Oxide and Vetiver Oil against Mosquito Vectors

Repellents play a major role in reducing the risk of mosquito-borne diseases by preventing mosquito bites. The present study evaluated the mosquito-repellent activity of β-caryophyllene oxide 1% (BCO), vetiver oil 2.5% (VO), and their binary mixtures (BCO + VO (1:1), BCO + VO (2:1), BCO + VO (1:2)) against four laboratory-colonized mosquito species, Aedes aegypti (L.), Aedes albopictus (Skuse), Anopheles minimus Theobald, and Culex quinquefasciatus Say, using an excito-repellency assay system. In general, the compound mixtures produced a much stronger response in the mosquitoes than single compounds, regardless of the test conditions or species. The greatest synergetic effect was achieved with the combination of BCO + VO (1:2) in both contact and noncontact trials with An. minimus (74.07-78.18%) and Cx. quinquefasciatus (55.36-83.64%). Knockdown responses to the binary mixture of BCO + VO were observed for Ae. albopictus, An. minimus, and Cx. quinquefasciatus, in the range of 18.18-33.33%. The synergistic repellent activity of BCO and VO used in this study may support increased opportunities to develop safer alternatives to synthetic repellents for personal protection against mosquitoes.

Modelling the transmission of dengue, zika and chikungunya: a scoping review protocol

INTRODUCTION

Aedes mosquitoes are the primary vectors for the spread of viruses like dengue (DENV), zika (ZIKV) and chikungunya (CHIKV), all of which affect humans. Those diseases contribute to global public health issues because of their great dispersion in rural and urban areas. Mathematical and statistical models have become helpful in understanding these diseases' epidemiological dynamics. However, modelling the complexity of a real phenomenon, such as a viral disease, should consider several factors. This scoping review aims to document, identify and classify the most important factors as well as the modelling strategies for the spread of DENV, ZIKV and CHIKV.

METHODS AND ANALYSIS

We will conduct searches in electronic bibliographic databases such as PubMed, MathSciNet and the Web of Science for full-text peer-reviewed articles written in English, French and Spanish. These articles should use mathematical and statistical modelling frameworks to study dengue, zika and chikungunya, and their cocirculation/coinfection with other diseases, with a publication date between 1 January 2011 and 31 July 2023. Eligible studies should employ deterministic, stochastic or statistical modelling approaches, consider control measures and incorporate parameters' estimation or considering calibration/validation approaches. We will exclude articles focusing on clinical/laboratory experiments or theoretical articles that do not include any case study. Two reviewers specialised in zoonotic diseases and mathematical/statistical modelling will independently screen and retain relevant studies. Data extraction will be performed using a structured form, and the findings of the study will be summarised through classification and descriptive analysis. Three scoping reviews will be published, each focusing on one disease and its cocirculation/co-infection with other diseases.

ETHICS AND DISSEMINATION

This protocol is exempt from ethics approval because it is carried out on published manuscripts and without the participation of humans and/or animals. The results will be disseminated through peer-reviewed publications and presentations in conferences.

Topical repellents for malaria prevention

BACKGROUND

Insecticide-based interventions, such as long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS), remain the backbone of malaria vector control. These interventions target mosquitoes that prefer to feed and rest indoors, but have limited capacity to prevent transmission that occurs outdoors or outside regular sleeping hours. In low-endemicity areas, malaria elimination will require that these control gaps are addressed, and complementary tools are found. The use of topical repellents may be particularly useful for populations who may not benefit from programmatic malaria control measures, such as refugees, the military, or forest goers. This Cochrane Review aims to measure the effectiveness of topical repellents to prevent malaria infection among high- and non-high-risk populations living in malaria-endemic regions.

OBJECTIVES

To assess the effect of topical repellents alone or in combination with other background interventions (long-lasting insecticide-treated nets, or indoor residual spraying, or both) for reducing the incidence of malaria in high- and non-high-risk populations living in endemic areas.

SEARCH METHODS

We searched the following databases up to 11 January 2023: the Cochrane Infectious Diseases Group Specialised Register; CENTRAL (in the Cochrane Library); MEDLINE; Embase; CAB Abstracts; and LILACS. We also searched trial registration platforms and conference proceedings; and contacted organizations and companies for ongoing and unpublished trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and cluster-randomized controlled trials (cRCTs) of topical repellents proven to repel mosquitoes. We also included non-randomized studies that complied with pre-specified inclusion criteria: controlled before-after studies (CBA), controlled interrupted time series (ITS), and controlled cross-over trials.

DATA COLLECTION AND ANALYSIS

Four review authors independently assessed trials for inclusion, and extracted the data. Two authors independently assessed the risk of bias (RoB) using the Cochrane RoB 2 tool. A fifth review author resolved any disagreements. We analysed data by conducting a meta-analysis, stratified by whether studies included populations considered to be at high-risk of developing malaria infection (for example, refugees, forest goers, or deployed military troops). We combined results from cRCTs with RCTs by adjusting for clustering and presented results using forest plots. We used the GRADE framework to assess the certainty of the evidence. We only included data on Plasmodium falciparum infections in the meta-analysis.

MAIN RESULTS

Thirteen articles relating to eight trials met the inclusion criteria and were qualitatively described. We included six trials in the meta-analysis (five cRCTs and one RCT). Effect on malaria incidence Topical repellents may slightly reduce P falciparum infection and clinical incidence when both outcomes are considered together (incidence rate ratio (IRR) 0.74, 95% confidence interval (CI) 0.56 to 0.98; 3 cRCTs and 1 RCT, 61,651 participants; low-certainty evidence); but not when these two outcomes were considered independently. Two cRCTs and one RCT (12,813 participants) evaluated the effect of topical repellents on infection incidence (IRR 0.76, 95% CI 0.56 to 1.02; low-certainty evidence). One cRCT (48,838 participants) evaluated their effect on clinical case incidence (IRR 0.66, 95% CI 0.32 to 1.36; low-certainty evidence). Three studies (2 cRCTs and 1 RCT) included participants belonging to groups considered at high-risk of being infected, while only one cRCT did not include participants at high risk. Adverse events Topical repellents are considered safe. The prevalence of adverse events among participants who used topical repellents was very low (0.6%, 283/47,515) and limited to mild skin reactions. Effect on malaria prevalence Topical repellents may slightly reduce P falciparum prevalence (odds ratio (OR) 0.81, 95% CI 0.67 to 0.97; 3 cRCTs and 1 RCT; 55,366 participants; low-certainty evidence). Two of these studies (1 cRCT and 1 RCT) were carried out in refugee camps, and included exclusively high-risk populations that were not receiving any other background vector control intervention.

AUTHORS' CONCLUSIONS

There is insufficient evidence to conclude that topical repellents can prevent malaria in settings where other vector control interventions are in place. We found the certainty of evidence for all outcomes to be low, primarily due to the risk of bias. A protective effect was suggested among high-risk populations, specially refugees, who might not have access to other standard vector control measures. More adequately powered clinical trials carried out in refugee camps could provide further information on the potential benefit of topical repellents in this setting. Individually randomized studies are also likely necessary to understand whether topical repellents have an effect on personal protection, and the degree to which diversion to non-protected participants affects overall transmission dynamics. Despite this, the potential additional benefits of topical repellents are most likely limited in contexts where other interventions are available.

Interactions of Equine Viruses with the Host Kinase Machinery and Implications for One Health and Human Disease

Zoonotic pathogens that are vector-transmitted have and continue to contribute to several emerging infections globally. In recent years, spillover events of such zoonotic pathogens have increased in frequency as a result of direct contact with livestock, wildlife, and urbanization, forcing animals from their natural habitats. Equines serve as reservoir hosts for vector-transmitted zoonotic viruses that are also capable of infecting humans and causing disease. From a One Health perspective, equine viruses, therefore, pose major concerns for periodic outbreaks globally. Several equine viruses have spread out of their indigenous regions, such as West Nile virus (WNV) and equine encephalitis viruses (EEVs), making them of paramount concern to public health. Viruses have evolved many mechanisms to support the establishment of productive infection and to avoid host defense mechanisms, including promoting or decreasing inflammatory responses and regulating host machinery for protein synthesis. Viral interactions with the host enzymatic machinery, specifically kinases, can support the viral infectious process and downplay innate immune mechanisms, cumulatively leading to a more severe course of the disease. In this review, we will focus on how select equine viruses interact with host kinases to support viral multiplication.

Tree canopy cover affects basal resources and nutrient profiles of Aedes and Culex larvae in cemetery vases in New Orleans, Louisiana, United States

Cemetery vases are important habitat for vector mosquito production, yet there is limited understanding on their food web dynamics and how they vary across environmental gradients. Tree cover is one factor that varies widely across cemeteries, and influence food webs by means of detrital inputs, temperature mediation, and light availability. Such information can be important for determining mosquito adult body size, fecundity, and competition outcomes, all of which may influence mosquito population and disease risk. This study evaluates the relationship between tree canopy cover and indicators of basal resources for Aede aegypti (L.), Aedes albopictuss (Skuse), and Culex quinquefasciatus (Say) larvae, such as stable isotopes (δ13C and δ15N) and nutrient stoichiometry in cemeteries of New Orleans, Louisiana (USA). Stable isotope values suggest that larvae feed directly on the Particulate Organic Matter (POM) suspended in the vase's water, and that POM composition influence the nutrient profiles of mosquito larvae. The POM of open canopy vases had higher δ13C values, than that of closed canopy vases indicating differences in relative proportion of basal carbon sources, with open canopy POM having a lower proportion of allochthonous carbon, and a higher proportion of authoctonous carbon. Accordingly, mosquito larvae collected from open canopy vases had higher δ13C values, and higher C:N than larvae from closed canopy vases. The results of this study show a shift in food web dynamics driven by canopy cover in cemetery vases that directly influence the nutrient profiles of mosquito larvae. The implications for mosquito ecology, and vector management are discussed.

Characterisation of human exposure to nocturnal biting by malaria and arbovirus vectors in a rural community in Chókwè district, southern Mozambique

Background: Understanding the magnitude of human exposure to mosquito biting is fundamental to reduce pathogen transmission. Here we report on a study quantifying the levels of mosquitoes attacking humans throughout the night in a rural area of Southern Mozambique. Methods: Surveys were carried out in Massavasse village, southern Mozambique. The abundance and composition of host-seeking mosquito communities at night were assessed by human-landing catches (HLC) at one-hour intervals. Periods when people were located predominantly outdoors or indoors were used to estimate the amount of residents' exposure to mosquito bites in either location, to explore the potential impact a bed net could have had in reducing biting by each vector species. Results: A total of 69,758 host-seeking female mosquitoes comprising 23 species in four genera were collected. The exposure to biting by virtually all vector species was consistently high outdoors, typically at early evening and morning, with exception of An. gambiae s.l which was likely of biting a person with nearly same intensity indoors and outdoors throughout the night. Bed nets use could have reduced biting by An. gambiae s.l (dominated by An. arabiensis), Ma. africana, Ma. uniformis, Cx. pipiens, Cx. antennatus, and Cx. poicilipes by 53%, 47%, 46%, 38%, 31%, and 28% respectively, compared to non-users. Conversely, a bed net user would have had little protection against An. pharoensis, An. ziemanni, An. tenebrosus, and Cx. tritaeniorhynchus biting exposures. Conclusions: This study showed that Massavasse residents were exposed to high levels of outdoor biting by malaria and arbovirus vectors that abound in the village. The findings help to identify entomological drivers of persistent malaria transmission in Mozambique and identify a wide range of arbovirus vectors nocturnally active in rural areas, many with outbreak potential. The study highlights the need for a surveillance system for monitoring arboviral diseases vectors in Mozambique.

The Promise and Challenge of Genetic Biocontrol Approaches for Malaria Elimination

Malaria remains an ongoing public health challenge, with over 600,000 deaths in 2021, of which approximately 96% occurred in Africa. Despite concerted efforts, the goal of global malaria elimination has stalled in recent years. This has resulted in widespread calls for new control methods. Genetic biocontrol approaches, including those focused on gene-drive-modified mosquitoes (GDMMs), aim to prevent malaria transmission by either reducing the population size of malaria-transmitting mosquitoes or making the mosquitoes less competent to transmit the malaria parasite. The development of both strategies has advanced considerably in recent years, with successful field trials of several biocontrol methods employing live mosquito products and demonstration of the efficacy of GDMMs in insectary-based studies. Live mosquito biocontrol products aim to achieve area-wide control with characteristics that differ substantially from current insecticide-based vector control methods, resulting in some different considerations for approval and implementation. The successful field application of current biocontrol technologies against other pests provides evidence for the promise of these approaches and insights into the development pathway for new malaria control agents. The status of technical development as well as current thinking on the implementation requirements for genetic biocontrol approaches are reviewed, and remaining challenges for public health application in malaria prevention are discussed.

Role of the Microbiome in Aedes spp. Vector Competence: What Do We Know?

Aedes aegypti and Aedes albopictus are the vectors of important arboviruses: dengue fever, chikungunya, Zika, and yellow fever. Female mosquitoes acquire arboviruses by feeding on the infected host blood, thus being able to transmit it to their offspring. The intrinsic ability of a vector to infect itself and transmit a pathogen is known as vector competence. Several factors influence the susceptibility of these females to be infected by these arboviruses, such as the activation of the innate immune system through the Toll, immunodeficiency (Imd), JAK-STAT pathways, and the interference of specific antiviral response pathways of RNAi. It is also believed that the presence of non-pathogenic microorganisms in the microbiota of these arthropods could influence this immune response, as it provides a baseline activation of the innate immune system, which may generate resistance against arboviruses. In addition, this microbiome has direct action against arboviruses, mainly due to the ability of Wolbachia spp. to block viral genome replication, added to the competition for resources within the mosquito organism. Despite major advances in the area, studies are still needed to evaluate the microbiota profiles of Aedes spp. and their vector competence, as well as further exploration of the individual roles of microbiome components in activating the innate immune system.

Evolutionary dynamics of Usutu virus: Worldwide dispersal patterns and transmission dynamics in Europe

Background

Usutu virus (USUV) is an emerging mosquito-borne Flavivirus, with birds as the main zoonotic reservoir. Humans are accidental hosts and mostly develop mild or even asymptomatic infections, although severe complications such as encephalitis can also arise. Detailed characterization of the pathogen's phylogenetics may offer valuable insights into the prediction and prevention of potential epidemics; however, lack of uniformity and the number of available USUV sequences worldwide hamper comprehensive investigation.

Aim

The study aimed to investigate USUV spatio-temporal dispersal inter- and intracontinentally and to estimate the dynamics of viral spread within Europe.

Methods

Phylogeographic and phylodynamic analyses were done using advanced phylogenetic methods implemented in Beast 1.10.4 and Beast 2.6.4 software packages.

Results

Herein, we report on a new USUV isolate from Culex pipiens collected in 2019 from Serbia. The results of this research revealed two newly described intercontinental migration events of USUV from Africa to Germany in the 1970s and from Africa to the Middle East (Israel) in the late 90s. Finally, phylodynamic analysis substantiated the ongoing active expansion of USUV in Europe.

Conclusion

The data would imply a high potential for further USUV expansion in Europe. Detailed phylogenetic characterization of the pathogen may offer valuable insights into prediction and prevention of potential epidemics; however, lack of uniformity and number of available USUV sequences worldwide hampers comprehensive investigation. This study draws attention to the need for upscaling USUV surveillance.

Epidemiological investigation of equine hindlimb ataxia with Setaria digitata in South Korea

Background

Since 2013, the number of requests for diagnosis for horses based on neurological symptoms has increased rapidly in South Korea. The affected horses have commonly exhibited symptoms of acute seasonal hindlimb ataxia. A previous study from 2015–2016 identified Setaria digitata as the causative agent.

Objectives

This study is an epidemiological investigation to find out risk factors related to the rapid increase in hindlimb ataxia of horses due to aberrant parasites in South Korea.

Methods

An epidemiological investigation was conducted on 155 cohabiting horses in 41 horse ranches where the disease occurred. The surrounding environment was investigated at the disease-causing horse ranches (n = 41) and 20, randomly selected, non-infected ranches.

Results

Hindlimb ataxia was confirmed in nine cohabiting horses; this was presumed to be caused by ectopic parasitism. Environments that mosquitoes inhabit, such as paddy fields within 2 km and less than 0.5 km from a river, had the greatest association with disease occurrence.

Conclusions

Most horse ranches in South Korea are situated in favorable environments for mosquitoes. Moreover, the number of mosquitoes in the country has increased since 2013 due to climate change. Additional research is required; however, these data show that it is necessary to establish guidelines for the use of anthelmintic agents based on local factors in South Korea and disinfection of the environment to prevent disease outbreaks.

Behavioral avoidance and biological safety of vetiver oil and its constituents against Aedes aegypti (L.), Aedes albopictus (Skuse) and Culex quinquefasciatus Say

Numerous plant-based repellents are widely used for personal protection against host-seeking mosquitoes. Vitiveria zizanioides (L.) Nash essential oil and its constituents have demonstrated various mosquito repellent activities. In this study, three chemical actions of vetiver oil and five constituents (terpinen-4-ol, α-terpineol, valencene, vetiverol and vetivone) were characterized against Aedes aegypti, Aedes albopictus and Culex quinquefasciatus by using the high-throughput screening assay system (HITSS). Significant contact escape responses in Ae. aegypti and Ae. albopictus to all test compounds at concentrations between 2.5 and 5% were observed. Spatial repellency responses were also observed in some tested mosquito populations depending upon concentrations. The most significant toxic response on mosquitoes was found at the highest concentration, except for vetivone which had no toxic effect on Ae. aegypti and Ae. albopictus. Results on phototoxic and genotoxic hazard revealed that vetiver oil and their constituents showed no phototoxic potential or any significant genotoxic response. In conclusion, vetiver oil and two constituents, valencene and vetiverol, are potentials as active ingredients for mosquito repellency and present no toxicity.

Entomological Surveillance of Aedes Mosquitoes: Comparison of Different Collection Methods in an Endemic Area in RIO de Janeiro, Brazil

Using collection methods for Aedes adults as surveillance tools provides reliable indices and arbovirus detection possibilities. This study compared the effectiveness of different methods for collecting Ae. aegypti and Ae. albopictus and detecting arboviruses circulating in field-caught female specimens. Collection sites were defined in urban, peri-urban, and rural landscapes in two Brazilian cities. Collections were performed using Adultraps (ADT), BG-Sentinel (BGS), CDC-like traps (CDC), and indoor (ASP-I) and outdoor (ASP-O) aspiration during the rainy and dry seasons of 2015 and 2016. Generalized linear mixed models were used to model the effectiveness of each collection method. A total of 434 Ae. aegypti and 393 Ae. albopictus were collected. In total, 64 Ae. aegypti and sixteen Ae. albopictus female pools were tested for DENV, CHIKV, ZIKV, or YFV; none were positive. Positivity and density were linear at low densities (<1 specimen); thereafter, the relationship became non-linear. For Ae. aegypti, ADT and CDC were less effective, and ASP-I and ASP-O were as effective as BGS. For Ae. albopictus, all collection methods were less effective than BGS. This study highlights the need for an integrated surveillance method as an effective tool for monitoring Aedes vectors.

Interaction of Haemagogus leucocelaenus (Diptera: Culicidae) and Other Mosquito Vectors in a Forested Area, Rio de Janeiro, Brazil

The yellow fever (YF) virus has been detected throughout Brazil, with the occurrence of human cases, cyclic epizootics, and its isolation from Haemagogus janthinomys and Hg. leucocelaenus. We assessed the seasonal occurrence, egg abundancy, and oviposition interaction of mosquito vector species captured at a Private Natural Heritage Reserve in the Atlantic Forest biome. A total of 2943 eggs and 1538 mosquito larvae were collected from which 1231 belonged to entomologically important species. Ovitraps were used to collect immature mosquitoes from September 2019 to January 2021. The Mann–Whitney test was used to assess the differences in the abundance of eggs between rainy and dry seasons. Kruskal–Wallis and Dunn’s post hoc tests were used to evaluate the significance of the differences in the number of individuals from vector species. The highest percentage of mosquito vector eggs were collected during the rainy season, from December to February. Most eggs recovered from ovitraps belonged to the species Hg. leucocelaenus, representing 85% of all mosquito eggs identified. The other species had lower abundances and percentages: Aedes terrens (7%), Haemagogus janthinomys (5%) and Aedes albopictus (3%). The species that shared breeding sites with a higher frequency were Hg. leucocelaenus and Hg. janthinomys, with a statistically positive correlation (ρ = 0.74). This finding suggests that maybe the presence of Hg. leucocelaenus eggs acted as an attractant for Hg. janthinomys or vice versa. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control approaches directed against specific pathogen vectors of medical and veterinary importance.

Mosquito (Diptera: Culicidae) diversity and medical importance in Koh Kong mangrove forests, Cambodia

Background

Mangroves are an ecosystem interface between land and sea, forming distinctive shallow-water marine communities in tropical and subtropical waters. The mangrove forest surface in Cambodia is being reduced due to deforestation. Because the mangrove type of ecosystem generally hosts a great diversity of mosquitoes, the urbanization of these ecosystems will increase interactions between humans and wild mosquitoes, and might thus serve as a potential source of new infectious diseases. Understanding mosquito diversity and analyzing their virome is critical to estimate the risk of emergence or future outbreaks of mosquito-borne diseases.

Objective

To understand the mosquito diversity of mangrove forests of Koh Kong province (Cambodia).

Methods

In 2019, the mosquito fauna was sampled for 3 consecutive days using BG-Sentinel and light traps, in 3 locations in the mangrove forests of Koh Kong province (Cambodia) during both dry and rainy seasons.

Results

A total of 3107 samples were collected, belonging to 10 genera for 34 species. The Culex genus was the most diverse, accounting for 10 species. One species, Culex sitiens, represented over 60% of all collected mosquitoes. A total of 12 medically important species were recorded, 2 species, Aedes (Stegomyia) albopictus and Culex vishnui, were collected in all sites and during both the dry and rainy seasons, highlighting a potential risk of these species acting as bridge vectors.

Conclusions

If new arboviruses were to be recorded in this peculiar area, it would indicate that the mosquito species found have the potential to act as a bridge between sylvatic and anthropogenic arboviruses.

Predicting the response of disease vectors to global change: The importance of allometric scaling

The distribution of disease vectors such as mosquitoes is changing. Climate change, invasions and vector control strategies all alter the distribution and abundance of mosquitoes. When disease vectors undergo a range shift, so do disease burdens. Predicting such shifts is a priority to adequately prepare for disease control. Accurate predictions of distributional changes depend on how factors such as temperature and competition affect mosquito life-history traits, particularly body size and reproduction. Direct estimates of both body size and reproduction in mosquitoes are logistically challenging and time-consuming, so the field has long relied upon linear (isometric) conversions between wing length (a convenient proxy of size) and reproductive output. These linear transformations underlie most models projecting species' distributions and competitive interactions between native and invasive disease vectors. Using a series of meta-analyses, we show that the relationship between wing length and fecundity are nonlinear (hyperallometric) for most mosquito species. We show that whilst most models ignore reproductive hyperallometry (with respect to wing length), doing so introduces systematic biases into estimates of population growth. In particular, failing to account for reproductive hyperallometry overestimates the effects of temperature and underestimates the effects of competition. Assuming isometry also increases the potential to misestimate the efficacy of vector control strategies by underestimating the contribution of larger females in population replenishment. Finally, failing to account for reproductive hyperallometry and variation in body size can lead to qualitative errors via the counter-intuitive effects of Jensen's inequality. For example, if mean sizes decrease, but variance increases, then reproductive outputs may actually increase. We suggest that future disease vector models incorporate hyperallometric relationships to more accurately predict changes in mosquito distribution in response to global change.

First Evidence of West Nile Virus Overwintering in Mosquitoes in Germany

Mosquitoes collected from mid-December 2020 to early March 2021 from hibernacula in northeastern Germany, a region of West Nile virus (WNV) activity since 2018, were examined for WNV-RNA. Among the 6101 mosquitoes tested in 722 pools of up to 12 specimens, one pool of 10 Culex pipiens complex mosquitoes collected in early March 2021 in the cellar of a medieval castle in Rosslau, federal state of Saxony-Anhalt, tested positive. Subsequent mosquito DNA analysis produced Culex pipiens biotype pipiens. The pool homogenate remaining after nucleic acid extraction failed to grow the virus on Vero and C6/36 cells. Sequencing of the viral NS2B-NS3 coding region, however, demonstrated high homology with virus strains previously collected in Germany, e.g., from humans, birds, and mosquitoes, which have been designated the East German WNV clade. The finding confirms the expectation that WNV can overwinter in mosquitoes in Germany, facilitating an early start to the natural transmission season in the subsequent year. On the other hand, the calculated low infection prevalence of 0.016–0.20%, depending on whether one or twelve of the mosquitoes in the positive pool was/were infected, indicates a slow epidemic progress and mirrors the still-hypoendemic situation in Germany. In any case, local overwintering of the virus in mosquitoes suggests its long-term persistence and an enduring public health issue.

Knockdown times in a simple assay determination of insecticide resistance in malaria vectors

BACKGROUND

Determining the insecticide resistance status of malaria vectors, particularly to insecticides used on mosquito nets, is important but is limited to a relatively small number of locations. We describe a simple assay that enables this information to be obtained over a much wider area.

METHODS

The time to knockdown of mosquitoes in an insecticide-treated netting-covered metal frame cage were recorded. The shape of the curve of the proportion of knocked down mosquitoes provides information on resistance status.

RESULTS

Resistant Anopheles funestus took significantly longer for knockdown than did susceptible Anopheles arabiensis.

CONCLUSIONS

This simple technique will enable a wide range of locations to be sampled, enhancing our understanding of the spread of resistance to pyrethroids.

Cannibalism and Necrophagy Promote a Resource Loop and Benefit Larval Development in Insects of Temporary Waters

Temporary aquatic habitats are contingent on the allochthonous inputs of plant and animal detritus, whose quality and availability can significantly affect the species developing in these habitats. Although animal detritus (i.e., invertebrate carcasses) is a high-quality food, it is an unpredictable and variable resource. On the contrary, conspecific individuals (dead or alive) are a nutritionally high-quality food source that is always available. In this context, conspecifics consumption, by cannibalism or necrophagy, can be a good strategy to overcome nutrient limitation and allow individual maintenance and development. Here, we tested this hypothesis by using the tiger mosquito Aedes albopictus. By carrying out laboratory and semi-field experiments, we first estimated the relative rate of cannibalism and necrophagy, under different larval densities. Then, we analyzed the effects of cannibalism and necrophagy on larval survival and adult yield. Consistent with our hypothesis, we found that cannibalism and necrophagy occurred under all experimental conditions, and that conspecific consumption had positive effects on individual development, as it significantly increased the rate of adult emergence and larval survival. Interestingly, about 50% of the initial cohort was consumed by conspecifics, suggesting that cannibalism and necrophagy can drive an important resources loop in temporary aquatic habitats.

Detection of Aedes (Stegomyia) albopictus (Skuse) in ovitraps of Mérida city, México

Introduction: The vector-borne diseases program in México has an established network of ovitraps for entomological surveillance of Aedes spp. In response to reports of Aedes albopictus in the periphery of Mérida, the state capital of Yucatán, the Ministry of Health increased the specificity of this surveillance. Objective: To describe the presence and distribution of Ae. albopictus in Mérida and its relative abundance compared to Aedes aegypti in ovitraps of the vector control program. Materials and methods: During October, 2019, 91 ovitraps were randomly selected from 31 neighborhoods of Mérida. Mosquitoes were reared at the insectary of the Collaborative Unit for Entomological Bioassays of the Autonomous University of Yucatán from eggs collected in the field. Relative abundance was determined for adult individuals of each identified species and neighborhood. Results: 32 % of the neighborhoods were positive for Ae. albopictus and 100 % for Ae. aegypti. A total of 28 adults of Ae. albopictus (10 females and 18 males) were obtained from ovitraps. No correlation was observed between the abundance of Ae. aegypti and Ae. albopictus for both adults and females (p>0.05) at the neighborhood level. Conclusions: The results confirm that Ae. albopictus coexisted with Ae. aegypti in Mérida at the time of the study. The low relative abundance suggests that Ae. albopictus was in the initial phase of invasion.

Impact of 1.5 oC and 2 oC global warming scenarios on malaria transmission in East Africa

Background: Malaria remains a global challenge with approximately 228 million cases and 405,000 malaria-related deaths reported in 2018 alone; 93% of which were in sub-Saharan Africa. Aware of the critical role than environmental factors play in malaria transmission, this study aimed at assessing the relationship between precipitation, temperature, and clinical malaria cases in East Africa and how the relationship may change under 1.5 ^oC and 2.0 ^oC global warming levels (hereinafter GWL1.5 and GWL2.0, respectively).

Methods: A correlation analysis was done to establish the current relationship between annual precipitation, mean temperature, and clinical malaria cases. Differences between annual precipitation and mean temperature value projections for periods 2008-2037 and 2023-2052 (corresponding to GWL1.5 and GWL2.0, respectively), relative to the control period (1977-2005), were computed to determine how malaria transmission may change under the two global warming scenarios.

Results: A predominantly positive/negative correlation between clinical malaria cases and temperature/precipitation was observed. Relative to the control period, no major significant changes in precipitation were shown in both warming scenarios. However, an increase in temperature of between 0.5 ^oC and 1.5 ^oC and 1.0 ^oC to 2.0 ^oC under GWL1.5 and GWL2.0, respectively, was recorded. Hence, more areas in East Africa are likely to be exposed to temperature thresholds favourable for increased malaria vector abundance and, hence, potentially intensify malaria transmission in the region.

Conclusions: GWL1.5 and GWL2.0 scenarios are likely to intensify malaria transmission in East Africa. Ongoing interventions should, therefore, be intensified to sustain the gains made towards malaria elimination in East Africa in a warming climate.

Impact of 1.5 oC and 2 oC global warming scenarios on malaria transmission in East Africa

Background: Malaria remains a global challenge with approximately 228 million cases and 405,000 malaria-related deaths reported in 2018 alone; 93% of which were in sub-Saharan Africa. Aware of the critical role than environmental factors play in malaria transmission, this study aimed at assessing the relationship between precipitation, temperature, and clinical malaria cases in East Africa and how the relationship may change under 1.5 oC and 2.0 oC global warming levels (hereinafter GWL1.5 and GWL2.0, respectively). Methods: A correlation analysis was done to establish the current relationship between annual precipitation, mean temperature, and clinical malaria cases. Differences between annual precipitation and mean temperature value projections for periods 2008-2037 and 2023-2052 (corresponding to GWL1.5 and GWL2.0, respectively), relative to the control period (1977-2005), were computed to determine how malaria transmission may change under the two global warming scenarios. Results: A predominantly positive/negative correlation between clinical malaria cases and temperature/precipitation was observed. Relative to the control period, no major significant changes in precipitation were shown in both warming scenarios. However, an increase in temperature of between 0.5 oC and 1.5 oC and 1.0 oC to 2.0 oC under GWL1.5 and GWL2.0, respectively, was recorded. Hence, more areas in East Africa are likely to be exposed to temperature thresholds favourable for increased malaria vector abundance and, hence, potentially intensify malaria transmission in the region. Conclusions: GWL1.5 and GWL2.0 scenarios are likely to intensify malaria transmission in East Africa. Ongoing interventions should, therefore, be intensified to sustain the gains made towards malaria elimination in East Africa in a warming climate.

Aircraft disinsection: what is the usefulness as a public health measure?

RATIONALE FOR REVIEW

Insecticide treatments in aircraft (termed 'aircraft disinsection') aim to support the containment of potentially disease-carrying vector insects. The introduction of non-endemic mosquito species is of concern as some mosquitoes can act as vectors of many serious human diseases. Expansion of vectors to previously non-endemic regions, extended flight networks and mosquito resistance to insecticides pose challenges to contemporary vector-control approaches. Despite established efficacy of aircraft disinsection in trials, there is increasing concern over its effectiveness and feasibility in flight operations, and its usefulness as a public health measure.

KEY FINDINGS

We explored the literature on disinsection through a narrative approach to obtain a pragmatic assessment of existing and future implementation challenges. We describe the shortcomings that hinder evaluation of the success of aircraft disinsection. These shortcomings include operational constraints that may impact effective treatment outcomes, lack of longitudinal data on pesticide exposure scenarios, lack of compliance mechanisms, pesticide resistance in mosquitoes, and limited evidence of the extent and type of mosquito species potentially transported via aircraft.

CONCLUSIONS AND RECOMMENDATIONS

Concerns about the introduction of non-endemic mosquito vectors reinforce the need for effective preventive measures. Import of disease vectors is likely to occur in the future under changing environmental and operational conditions. Optimal impact from disinsection requires appropriate deployment, commitment and use. The current system of evaluation is inadequate for producing the evidence needed for informed policy decisions. While utilizing the results of research into environmentally sustainable vector-control methods for use in aircraft, future approaches to aircraft disinsection require improved evidence of anticipated benefits and harms, reliable monitoring data on insecticide resistance, and must be supported by strong vector control at airports.

Mosquito-Borne Viruses and Non-Human Vertebrates in Australia: A Review

Mosquito-borne viruses are well recognized as a global public health burden amongst humans, but the effects on non-human vertebrates is rarely reported. Australia, houses a number of endemic mosquito-borne viruses, such as Ross River virus, Barmah Forest virus, and Murray Valley encephalitis virus. In this review, we synthesize the current state of mosquito-borne viruses impacting non-human vertebrates in Australia, including diseases that could be introduced due to local mosquito distribution. Given the unique island biogeography of Australia and the endemism of vertebrate species (including macropods and monotremes), Australia is highly susceptible to foreign mosquito species becoming established, and mosquito-borne viruses becoming endemic alongside novel reservoirs. For each virus, we summarize the known geographic distribution, mosquito vectors, vertebrate hosts, clinical signs and treatments, and highlight the importance of including non-human vertebrates in the assessment of future disease outbreaks. The mosquito-borne viruses discussed can impact wildlife, livestock, and companion animals, causing significant changes to Australian ecology and economy. The complex nature of mosquito-borne disease, and challenges in assessing the impacts to non-human vertebrate species, makes this an important topic to periodically review.

Mosquito Vector Production across Socio-Economic Divides in Baton Rouge, Louisiana

We investigated the role of socio-economic factors in the proliferation of mosquito vectors in two adjacent but socio-economically contrasting neighborhoods in Baton Rouge, LA, USA. We surveyed mosquito larvae habitat, mosquito larvae, and adult mosquitoes during the summer of 2020. We also evaluated the number of requests for mosquito abatement services in the years preceding the study for each area. While we did not find differences in terms of the most abundant species, Culex quinquefasicatus (F_1,30 = 0.329, p = 0.57), we did find a higher abundance of mosquito habitats, particularly discarded tires, as well as larvae (z = 13.83, p < 0.001) and adults (F_1,30 = 4.207, p = 0.049) of the species Aedes albopictus in the low-income neighborhood. In contrast, mosquito abatement requests were significantly higher in the high socio-economic neighborhood (z = −8.561, p < 0.001). This study shows how factors such as adjudicated properties, discarded tires and pest abatement requests can influence the abundance of mosquito vectors, disproportionately affecting low-income groups. This study also highlights how Aedes spp. may be better indicators than Culex spp. of socio-economic differences between nearby neighborhoods, due to their short flight range and habitat preferences, and this should be considered in future studies attempting to detect such disparities in the future.

High-Throughput Method for Detection of Arbovirus Infection of Saliva in Mosquitoes Aedes aegypti and Ae. albopictus

Vector competence refers to the ability of a vector to acquire, maintain, and transmit a pathogen. Collecting mosquito saliva in medium-filled capillary tubes has become the standard for approximating arbovirus transmission. However, this method is time-consuming and labor-intensive. Here we compare the capillary tube method to an alternative high-throughput detection method the collection of saliva on paper cards saturated with honey, with (FTA card) and without (filter paper) reagents for the preservation of nucleic acid for Aedes aegypti and Aedes albopictus mosquitoes infected with two emerging genotypes of the chikungunya virus (CHIKV). Model results showed that the Asian genotype CHIKV dissemination in the harvested legs of both Ae. aegypti and Ae. albopictus increased the odds of females having a positive salivary infection and higher salivary viral titers, while for the IOL genotype the same effect was observed only for Ae. aegypti. Of the three tested detection methods, the FTA card was significantly more effective at detecting infected saliva of Ae. aegypti and Ae. albopictus females than the capillary tube and filter paper was as effective as the capillary tube for the Asian genotype. We did not find significant effects of the detection method in detecting higher viral titer for both Asian and IOL genotypes. Our results are discussed in light of the limitations of the different tested detection methods.

West Nile Virus Mosquito Vectors (Diptera: Culicidae) in Germany

In 2018, West Nile virus (WNV) broke out for the first time in Germany, with continuation of the epidemic in 2019, involving birds, horses and humans. To identify vectors and characterize the virus, mosquitoes were collected in both years in zoological gardens and on a horse meadow immediately following the diagnosis of disease cases in birds and horses. Mosquitoes were identified and screened for WNV by qRT-PCR, with virus-positive samples being sequenced for the viral envelope protein gene. While no positive mosquitoes were found in 2018, seven mosquito pools tested positive for WNV in 2019 in the Tierpark (Wildlife Park) Berlin. The pools consisted of Cx. pipiens biotype pipiens (n = 5), and a mixture of Cx. p. biotype pipiens and Cx. p. biotype molestus (n = 2), or hybrids of these, and were collected between 13 August and 24 September 2019. The virus strain turned out to be nearly identical to two WNV strains isolated from birds diseased in 2018 in eastern Germany. The findings represent the first demonstration of WNV in mosquitoes in Germany and include the possibility of local overwintering of the virus.

Vector competence of Culex mosquitoes (Diptera: Culicidae) in Zika virus transmission: an integrative review

OBJECTIVE

To identify studies on the competence of Culex mosquitoes as vectors for the transmission of Zika virus (ZIKV) around the globe.

METHODS

We performed an integrative review to identify relevant articles on specific experiments to determine whether Culex mosquitoes are vectors for ZIKV. The sources we used for our research were the Brazilian Periódicos CAPES electronic portal (MEDLINE/PubMed, ScienceDirect Journals, Nature Publishing Group, SciELO, Springer Link, and 250 other databases) and gray literature.

RESULTS

We identified 344 studies, of which 36 were considered for this review. In 8 studies, infection in salivary glands of Culex quinquefasciatus, Culex restuans, Culex tarsalis, and Culex coronator was detected. Cx. quinquefasciatus was the most studied among those confirmed as potential ZIKV vectors, and only strains of Asian lineages (THA/2014/SV0127-14; SZ01 (2016)) and American lineages (BRPE243 (2015); PRVABC59 (2015)) can infect the salivary glands of Culex mosquitoes. The tested African strains (MR766 and DAK AR 41525) were unable to infect salivary glands.

CONCLUSIONS

There is still a lack of compelling evidence that indicates Culex spp. are a competent ZIKV vector, but they should remain a target for further monitoring studies, especially regarding ZIKV transmission to other species. Furthermore, studies should not be limited to studying whether their salivary glands are infected.

Comparison Between Larval Survey Index and Positive Ovitrap Index in the Evaluation of Populations of Aedes (Stegomyia) aegypti (Linnaeus, 1762) North of Paraná, Brazil

Aedes (Stegomyia) aegypti (Linnaeus, 1762) is one of the world's most widely distributed mosquitoes and is the vector of the dengue virus, one of the most important reemerging diseases. Besides dengue, A. aegypti can also transmit urban yellow fever, chikungunya, and Zika virus, making it of great medical importance. Thus, it is of extreme importance to find reliable methods to evaluate the presence of A. aegypti in urban areas. In Brazil, rapid index surveys of Aedes aegypti by means of larval survey (LIRAa) is the official method to estimate the Breteau (BI) and property infestation (PII) indexes, which indicates how many infested containers with larvae of A. aegypti were found by the total number of properties surveyed and the proportion of houses infested, respectively. As the LIRAa requires access to private residences and trained personal to find breeding sites and do not reveal the mosquito's presence when in low density, it has not demonstrated efficacy in determining the presence of A. aegypti. To evaluate an alternative method, the LIRAa method was compared with an oviposition trap, made with hay infusion and a hardboard pallet, to evaluate the BI and the PII. The 2 methods were carried out simultaneously through 4 surveys, sampling 60 homes per survey. To evaluate the best configuration of ovitraps for surveillance of A. aegypti, the ovitraps were installed in intradomicile and peridomicile areas, with 1 to 5 traps per residence and with 1 to 3 pallets per trap, and these different configurations were compared using the positive ovitrap index (POI) and egg density index (EDI). The ovitraps showed greater sensitivity for detecting the presence of A. aegypti, with a BI of 72.5% and PII of 54.2%, whereas the LIRAa revealed only 2.1% for the BI and 1.3% for the PII. Therefore, the use of sentinel traps can provide information in a more rapid and precise manner. As there were no differences in the ovitraps distributions patterns, the ovitraps can be installed in the peridomicile area, with 2 traps per surveillance point and 1 pallet per trap, making their installation easier and more cost-efficient, facilitating the work of health agents in future surveillances complementing LIRAa's actions for efficient monitoring.

Leptolegnia chapmanii como alternativa biológica para el control de Aedes aegypti

Leptolegnia chapmanii is a facultative pathogen of many species of mosquitoes, among which species of the genus Aedes, Culex and Anopheles stand out for their medical and sanitary importance. The potential of L. chapmanii as an alternative to control lies in its virulence, pathogenicity and specificity against the larval stages of mosquitoes, and because of its harmlessness to non-target species such as fish and amphibians, among others. The natural presence of L. chapmanii had been reported in Argentina, Brazil and the United States. Its presence is possible in other countries throughout the American continent. The development of protocols to produce, formulate, store and apply products based on this microorganism is one of the objectives proposed for the group of Entomopathogenic Fungi at the Centro de Estudios Parasitológicos y de Vectores, Universidad Nacional de La Plata. The efficacy of L. chapmanii as controller is affected by external factors such as temperature, pH, salinity and radiation among others. The process of transfer from the research centers to industry implies many phases. In this way, our project with L. chapmanii is in an initial phase, where we are working on a laboratory scale in proof of concept. We hope to begin soon with the efficacy, efficiency, stability and ecotoxicological safety tests, at the laboratory, semi-field and field scale.

First report of Aedes (Stegomyia) albopictus (Skuse) in Orinoquia region of Colombia

Introducción.

Aedes albopictus es vector de arbovirus, como Flavivirus, Alphavirus, Bunyavirus, Phlebovirus, Orbivirus y Picornavirus. Muchos son agentes etiológicos de enfermedades en humanos. Actualmente, A. albopictus se encuentra en expansión geográfica por su adaptación a diversos ambientes y tipos de criaderos. En Colombia, este mosquito fue reportado por primera vez en 1998 y, hasta el momento, se ha registrado en 10 departamentos.

Objetivo.

Determinar la presencia de A. albopictus en Yopal, Casanare.

Materiales y métodos.

En una búsqueda activa de larvas de A. aegypti en la zona industrial de Yopal, se observaron por primera vez mosquitos adultos de A. albopictus. Por lo anterior, se realizó la inspección en el intradomicilio y el peridomicilio de las viviendas en ocho localidades del municipio, en la cual se recolectaron larvas y pupas al inspeccionar hábitats larvarios, y hembras adultas, mediante capturas sobre atrayente humano protegido.

Resultados.

Se identificaron 755 larvas de mosquitos, 71,5 % de A. aegypti, 24,8 % de A.albopictus, 3,2 % de Culex quinquefasciatus y 0,8 % de C. coronator y C. nigripalpus. Se capturaron 37 mosquitos adultos de A. albopictus. Los depósitos con mayor abundancia de este vector fueron las llantas.

Conclusión.

Ante la presencia de A. albopictus se sugiere intensificar el sistema de vigilancia entomológica para detectar nuevas poblaciones dentro del departamento y en las áreas cercanas. Se debe poner atención a los criaderos artificiales de las zonas cercanas a los parqueaderos de vehículos de transporte de alimentos, insumos y maquinaria, procedentes de áreas con presencia del vector.

Mosquito vectors of arboviruses in French Polynesia

The circulation of arthropod-borne viruses (arboviruses) throughout the Pacific is no exception in French Polynesia (FP). We review here the mosquito vectors involved or potentially involved in the transmission of arboviruses in FP. We highlight Aedes aegypti and Aedes polynesiensis; species that are widely distributed in FP and whose ability to transmit dengue, zika and chikungunya viruses is well known. In addition, we discuss the contribution of those species and the abundant Culex annulirostris to the silent circulation of Ross River virus in FP. As these mosquito species and others present in FP are known to be vectors of a large panel of arboviruses, there is a high risk for new emergences.

Comparative Analysis of Mosquito Trap Counts In the Peruvian Amazon: Effect of Trap Type and Other Covariates On Counts and Diversity

Efficient detection of multiple species of adult mosquitoes in various habitats using effective traps is a crucial 1st step in any disease prevention program. Novel trap types that target tropical vectors of human diseases require field testing in the habitat of the vector-disease system in question. This paper analyzes a series of mosquito trapping studies conducted at Mapacocha, San Juan Bautista District, Loreto, Peru, during August-September 2013 and April-May 2014. Six trap configurations were evaluated in forest and rural locations. Adult mosquito counts were analyzed using full Bayesian inference of multilevel generalized linear models and posterior probability point estimates of the difference of means of the combined trap catch by trap type comparisons of all species. Light traps (Centers for Disease Control and Prevention [CDC] incandescent, white light-emitting diode [LED], and ultraviolet LED) caught greater numbers of mosquitoes compared with traps baited with yeast-generated CO₂ and Biogents Sentinel^™ traps (battery powered traps without light and passive box traps). However, diversity measures (species richness, evenness, and similarity) were consistently nearly equal among trap types. Arbovirus vectors were more common in forest locations, while malaria vectors were more common near human habitations. Location had a significant effect on trap effectiveness and mosquito diversity, with traps from forest locations having greater numbers and greater species richness, compared with traps set near human habitations. The results of this study will inform mosquito surveillance trap choices in remote regions of central South America, including regions with emerging tropical diseases, such and dengue and Zika virus.

Transgenic Mosquitoes - Fact or Fiction?

Technologies for controlling mosquito vectors based on genetic manipulation and the release of genetically modified mosquitoes (GMMs) are gaining ground. However, concrete epidemiological evidence of their effectiveness, sustainability, and impact on the environment and nontarget species is lacking; no reliable ecological evidence on the potential interactions among GMMs, target populations, and other mosquito species populations exists; and no GMM technology has yet been approved by the WHO Vector Control Advisory Group. Our opinion is that, although GMMs may be considered a promising control tool, more studies are needed to assess their true effectiveness, risks, and benefits. Overall, several lines of evidence must be provided before GMM-based control strategies can be used under the integrated vector management framework.

Patchy DNA forms of the Zika virus RNA genome are generated following infection in mosquito cell cultures and in mosquitoes

Zika virus (ZIKV) is a mosquito-borne flavivirus and has historically been reported to cause mild symptomatic diseases during human infections. More recently, the explosion of microcephaly among infants born to ZIKV-infected women has made ZIKV a global public health concern. While ZIKV causes acute human diseases, infections of vector mosquitoes are basically non-pathogenic, allowing persistent infections and conferring lifelong ability to transmit the virus. Recent studies have revealed that DNA forms of arboviral RNA genomes play a significant role in viral persistence in mosquitoes. We have initiated experiments to determine whether ZIKV generates viral DNA (vDNA) forms following infection in mosquitoes. Here we show that vDNAs are generated following ZIKV infection both in mosquito cell cultures and in its primary vector Aedes aegypti. vDNA formation is more extensive in RNA interference (RNAi)-deficient Aedes albopictus-derived C6/36 cells compared to RNAi-proficient mosquito cells. In addition, vDNAs are generated via multiple template-switching events.

Anomalous High Rainfall and Soil Saturation as Combined Risk Indicator of Rift Valley Fever Outbreaks, South Africa, 2008-2011

Rift Valley fever (RVF), a zoonotic vectorborne viral disease, causes loss of life among humans and livestock and an adverse effect on the economy of affected countries. Vaccination is the most effective way to protect livestock; however, during protracted interepidemic periods, farmers discontinue vaccination, which leads to loss of herd immunity and heavy losses of livestock when subsequent outbreaks occur. Retrospective analysis of the 2008-2011 RVF epidemics in South Africa revealed a pattern of continuous and widespread seasonal rainfall causing substantial soil saturation followed by explicit rainfall events that flooded dambos (seasonally flooded depressions), triggering outbreaks of disease. Incorporation of rainfall and soil saturation data into a prediction model for major outbreaks of RVF resulted in the correctly identified risk in nearly 90% of instances at least 1 month before outbreaks occurred; all indications are that irrigation is of major importance in the remaining 10% of outbreaks.

Neem cake as a promising larvicide and adulticide against the rural malaria vector Anopheles culicifacies (Diptera: Culicidae): a HPTLC fingerprinting approach

Mosquitoes are insects of huge public health importance, since they act as vectors for important pathogens and parasites. Here, we focused on the possibility of using the neem cake in the fight against mosquito vectors. The neem cake chemical composition significantly changes among producers, as evidenced by our HPTLC (High performance thin layer chromatography) analyses of different marketed products. Neem cake extracts were tested to evaluate the ovicidal, larvicidal and adulticidal activity against the rural malaria vector Anopheles culicifacies. Ovicidal activity of both types of extracts was statistically significant, and 150 ppm completely inhibited egg hatching. LC₅₀ values were extremely low against fourth instar larvae, ranging from 1.321 (NM1) to 1.818 ppm (NA2). Adulticidal activity was also high, with LC₅₀ ranging from 3.015 (NM1) to 3.637 ppm (NM2). This study pointed out the utility of neem cake as a source of eco-friendly mosquitocides in Anopheline vector control programmes.

Dosage Compensation in the African Malaria Mosquito Anopheles gambiae

Dosage compensation is the fundamental process by which gene expression from the male monosomic X chromosome and from the diploid set of autosomes is equalized. Various molecular mechanisms have evolved in different organisms to achieve this task. In Drosophila, genes on the male X chromosome are upregulated to the levels of expression from the two X chromosomes in females. To test whether a similar mechanism is operating in immature stages of Anopheles mosquitoes, we analyzed global gene expression in the Anopheles gambiae fourth instar larvae and pupae using high-coverage RNA-seq data. In pupae of both sexes, the median expression ratios of X-linked to autosomal genes (X:A) were close to 1.0, and within the ranges of expression ratios between the autosomal pairs, consistent with complete compensation. Gene-by-gene comparisons of expression in males and females revealed mild female bias, likely attributable to a deficit of male-biased X-linked genes. In larvae, male to female ratios of the X chromosome expression levels were more female biased than in pupae, suggesting that compensation may not be complete. No compensation mechanism appears to operate in male germline of early pupae. Confirmation of the existence of dosage compensation in A. gambiae lays the foundation for research into the components of dosage compensation machinery in this important vector species.

A rapid qPCR method to investigate the circulation of the yeast Wickerhamomyces anomalus in humans

The yeast Wickerhamomyces anomalus has been proposed for many biotechnological applications in the food industry. However, a number of opportunistic pathogenic strains have been reported as causative agents of nosocomial fungemia. Recognition of potentially pathogenic isolates is an important challenge for the future commercialization of this yeast. The isolation of W. anomalus from different matrices and, recently, from mosquitoes, requires further investigations into its circulation in humans. Here we present a qPCR protocol for the detection of W. anomalus in human blood samples and the results of a screening of 525 donors, including different classes of patients and healthy people.

Bionomic aspects of the Anopheles subpictus species complex in Sri Lanka

Anopheles subpictus Grassi s.l. (Diptera: Culicidae) functions as a secondary malaria vector to Anopheles culicifacies Giles s.l. (Diptera: Culicidae) in Sri Lanka. The taxon A. subpictus is reported to exist as a species complex comprising four sibling species (A-D) that can be differentiated through polytene chromosome banding patterns and stage-specific morphometric traits in India. Based on the morphological characteristics described for the Indian Subpictus Complex, the presence of all four sibling species has been described in Sri Lanka. As sibling species show distinct bio-ecological characteristics that are important for devising appropriate vector control measures, a study was carried out in six districts in the dry zone of Sri Lanka. The results confirm the presence of all four sibling species, with species C predominating in inland areas and species B in coastal areas. Species C and D were indoor-resting and indoor-feeding, while species B was outdoor-resting with no significant preference for indoor- or outdoor-resting. Species B showed distinct morphological variation in the ornamentation of wings and palpi. Blood meal analysis revealed that species B, C, and D can feed on humans as well as cattle. The differential bio-ecological traits shown by the members of the Subpictus Complex are important for developing appropriate vector control measures in Sri Lanka.

Improvised microinjection technique for mosquito vectors

BACKGROUND & OBJECTIVES

Bio-manipulation technique is of primary importance during the development of transgenic mosquitoes. The study describes the variable factors that influence the viability of medically important mosquito vectors during microinjection.

METHODS

Three mosquito vectors belonging to the genus Aedes, Anopheles and Culex were microinjected at different developmental stages of their life cycle viz., egg, larvae, pupae and adult.

RESULTS

The improvisations revealed an increased survivability of biomanipulated mosquitoes during the embryonic and adult microinjection. The study of injecting larvae and pupae resulted in poor survivability.

INTERPRETATION & CONCLUSIONS

The microinjection protocol was successfully tested on three important mosquito vectors. The critical period after biomanipulation which contributes heavily for the survivability factor was evaluated. The results provide a common protocol for biomanipulation of three mosquito vectors with enhanced survivability.

Key factors influencing canine heartworm, Dirofilaria immitis, in the United States

An examination of the Companion Animal Parasite Council's (CAPC) canine heartworm data to clarify the spatial prevalence of heartworm in the United States. Factors thought to influence the spatial risk of disease, as identified in a recent CAPC workshop, are discussed.