Biological Control Of Vectors Research Articles

Occurrence of Salmonellae in Chickens from some Selected Poultry Farms in Kano, Nigeria

Study’s Excerpt/Novelty This study provides a novel investigation into the prevalence of Salmonella species in poultry from selected farms in Kano, Nigeria, using comprehensive random sampling techniques across multiple local government areas. The findings reveal a notably low prevalence of asymptomatic Salmonella infections (1.54%) among chickens, potentially attributable to effective hygiene practices, biosecurity measures, and biological control of vectors. This research contributes valuable baseline data for the epidemiological understanding and management of Salmonella in poultry farms within the region. Full Abstract Infections with bacteria of the genus Salmonella are responsible for a variety of acute and chronic diseases in poultry. This study was carried out to determine the prevalence of Salmonella species in chickens from some selected poultry farms in Kano, Nigeria. Random sampling method was used in the study. One (1) farm was chosen from each of the eight (8) selected Local Government areas of the State. Thirteen (13) samples each from cloacae, egg, dust, drag and boots which is (65) from each farm) were collected from apparently healthy chickens (layers), transported immediately to the laboratory for analyses. The colonies were subsequently subjected to Gram-staining and microscopy. Eight Salmonella isolates were determined, three (3) were isolated from boot swabs, two (2) from cloacal swabs and one (1) each from egg, dust and drag swabs. All the isolates were confirmed by serological test; using Salmonella “O” antigen; group A-S (Oxoid). Asymptomatic Salmonella infection among chickens in the sampled farms is low with (1.54%). The low occurrence could be attributed to proper hygienic practices, biosecurity measure as well as application of biological control of rodents and other vehicles of Salmonella.

TOXICITY OF LEAF AND ROOT EXTRACT OF ANTING-ANTING (Acalypha indica L.) ON MORTALITY OF AEDES AEGYPTI

Dengue Hemorrhagic Fever (DHF) is still one of the main public health problems and often has the status of an Extraordinary Event (KLB) with a high number of cases in a number of regions in Indonesia. Mosquito control with active chemical compounds can be difficult to decompose in nature and cause mosquitoes to become resistant to the next generation. As a substitute, the anting plant (Acalypha indica L.), which has been considered a weed, has bioactive compounds that can be used as natural insecticides. Biological control of vectors by using natural insecticides, a mixture of leaf and root extracts of the anting plant. The study used a mixture of leaf and root extracts of the anting plant using 7 treatments consisting of 5 serial concentrations of 250ppm, 500ppm, 750ppm, 800ppm, and 1000ppm, one positive control group using Aedes and one more negative control using Abate. The concentration that can kill 50% of Aedes aegypti larvae or (LC50) within 24 hours of exposure is 766,000 ppm. The plants contain secondary metabolites such as alkaloids, flavonoids, triterpenoids, and steroids which are toxic to the larvae of the Aedes aegypti mosquito.
 Keywords: Acalypha indica L., Aedes aeypti; Toxicity

Evolution of knockdown resistance (kdr) mutations of Aedes aegypti and Aedes albopictus in Hainan Island and Leizhou Peninsula, China.

Aedes aegypti and Aedes albopictus are important vectors of human arboviruses, transmitting arboviral diseases such as yellow fever, dengue, chikungunya and Zika. These two mosquitoes coexist on Hainan Island and the Leizhou Peninsula in China. Over the past 40 years, the distribution of Ae. albopictus has gradually expanded in these areas, while the distribution of Ae. aegypti has declined dramatically mainly due to the ecological changes and some other factors such as heavy use of insecticide indoor based on endophagic bloodfeeding of the species. This study focused on the knockdown resistance (kdr) genes of both mosquitoes, investigated their mutations, and analyzed their haplotype and evolutionary diversity combined with population genetic features based on the ND4/ND5 genes to further elucidate the molecular mechanisms underlying the development of insecticide resistance in both mosquitoes. Three mutations, S989P, V1016G and F1534C, were found to be present in Ae. aegypti populations, and the three mutations occurred synergistically. Multiple mutation types (F1534C/S/L/W) of the F1534 locus are found in Ae. albopictus populations, with the three common mutations F1534C, F1534S and F1534L all having multiple independent origins. The F1534W (TTC/TGG) mutation is thought to have evolved from the F1534L (TTC/TTG) mutation. The F1534S (TTC/TCG) mutation has evolved from the F1534S (TTC/TCC) mutation. The most common form of mutation at the F1534 locus found in this study was S1534C, accounting for 20.97%, which may have evolved from the F1534C mutation. In addition, a new non-synonymous mutation M1524I and 28 synonymous mutations were identified in Ae. albopictus populations. Correlation analysis showed that the genetic diversity of Ae. aegypti and Ae. albopictus populations did not correlate with their kdr haplotype diversity (P>0.05), but strong gene flow between populations may have contributed to the evolution of the kdr gene. The study of kdr gene evolution in the two mosquito species may help to identify the evolutionary trend of insecticide resistance at an early stage and provide a theoretical basis for improving the efficiency of biological vector control and subsequent research into new insecticides.

Can biological control be a strategy to control vector-borne plant viruses?

Plant viruses transmitted by vector pests are one of the most important worldwide threats to global food production and security. Biological control strategies to enhance natural enemies (parasitoids and predators) have mainly focused on their ability to reduce pest density. In contrast, few studies have examined how natural enemies affect the spread and the incidence of viruses in a crop, although those results could be used as levers for a more sustainable management of viral diseases. Vector-borne plant viruses can be classified in three categories based on their transmission mode: non-persistently transmitted viruses, semi-persistently transmitted viruses and persistently transmitted viruses, whereas vector density, fitness and movement were identified as main drivers of virus spread in a crop, their relative contributions to virus epidemiology may also depend on both the transmission mode and the presence of natural enemies. The first part of the review focuses on virus transmission dynamics in relation to vector activity and density. Because we identify different patterns for each type of plant viruses, control strategies that lead to changes in vector traits, should be adapted to the targeted virus. However, biological control of insect vectors has been rarely adapted to the mode of transmission of the target virus. Thus, the last part of the review explores the conditions required for natural enemies (parasitoids and predators) to prevent epidemics outbreaks of each type of plant viruses. Briefly, if combined with other practices, biological control of vectors to keep virus incidence below the economic threshold is a promising approach for persistently transmitted viruses but might be more difficult to achieve with non-persistently transmitted viruses and semi-persistently transmitted viruses.

New self-sexing Aedes aegypti strain eliminates barriers to scalable and sustainable vector control for governments and communities in dengue-prone environments.

For more than 60years, efforts to develop mating-based mosquito control technologies have largely failed to produce solutions that are both effective and scalable, keeping them out of reach of most governments and communities in disease-impacted regions globally. High pest suppression levels in trials have yet to fully translate into broad and effective Aedes aegypti control solutions. Two primary challenges to date-the need for complex sex-sorting to prevent female releases, and cumbersome processes for rearing and releasing male adult mosquitoes-present significant barriers for existing methods. As the host range of Aedes aegypti continues to advance into new geographies due to increasing globalisation and climate change, traditional chemical-based approaches are under mounting pressure from both more stringent regulatory processes and the ongoing development of insecticide resistance. It is no exaggeration to state that new tools, which are equal parts effective and scalable, are needed now more than ever. This paper describes the development and field evaluation of a new self-sexing strain of Aedes aegypti that has been designed to combine targeted vector suppression, operational simplicity, and cost-effectiveness for use in disease-prone regions. This conditional, self-limiting trait uses the sex-determination gene doublesex linked to the tetracycline-off genetic switch to cause complete female lethality in early larval development. With no female progeny survival, sex sorting is no longer required, eliminating the need for large-scale mosquito production facilities or physical sex-separation. In deployment operations, this translates to the ability to generate multiple generations of suppression for each mosquito released, while being entirely self-limiting. To evaluate these potential benefits, a field trial was carried out in densely-populated urban, dengue-prone neighbourhoods in Brazil, wherein the strain was able to suppress wild mosquito populations by up to 96%, demonstrating the utility of this self-sexing approach for biological vector control. In doing so, it has shown that such strains offer the critical components necessary to make these tools highly accessible, and thus they harbour the potential to transition mating-based approaches to effective and sustainable vector control tools that are within reach of governments and at-risk communities who may have only limited resources.

Efficacy of native cyclopoid copepods in biological vector control with regard to their predatory behavior against the Asian tiger mosquito, Aedes albopictus

BackgroundThe control of the Asian tiger mosquito Aedes albopictus (Diptera: Culicidae) is crucial owing to its high vector competence for more than 20 arboviruses—the most important being dengue, chikungunya and Zika virus. Aedes albopictus has an enormous adaptive potential, and its invasive spreading across urban and suburban environments poses challenges for its control. Therefore, all suitable, cost-effective and eco-friendly control tools should be put into practice. In this context, cyclopoid copepods are already known as effective predators of mosquito larvae. This study reports an essential preliminary step towards the integration of copepods into the vector control strategy in Germany, in order to provide a sustainable tool in an integrated control strategy based on the elimination or sanitation of breeding sites, the use of formulations based on Bacillus thuringiensis israelensis (Bti.) and the sterile insect technique (SIT).MethodsThe predatory potential of native cyclopoid copepods, namely the field-derived species Megacyclops viridis (Crustacea: Cyclopidae), was examined against the larvae of Ae. albopictus, and for comparison, against the larvae of the common house mosquito, Culex pipiens sensu lato (Diptera: Culicidae). The use of different larval instars as prey, and various predator-to-prey ratios, were examined under laboratory and semi-field conditions. The compatibility of Bti. applications along with the use of copepods was assessed in the laboratory.ResultsHigh predation efficiency of M. viridis upon first-instar larvae of Ae. albopictus was observed under laboratory (up to 96%) and semi-field conditions (65.7%). The copepods did not prey upon stages further developed than the first instars, and in comparison with Ae. albopictus, the predation rates on the larvae of Cx. pipiens s.l. were significantly lower.ConclusionsThe results indicate a high predation potential of M. viridis against Ae. albopictus larvae, even though strong larval stage and mosquito species preferences were implicated. The integration of copepods as a promising biocontrol agent to the vector control strategy in Germany is therefore highly recommended, especially because of the excellent compatibility of copepods with the use of Bti. However, further research is required, concerning all the probable parameters that may impact the copepod performance under natural conditions.Graphical

Viruses of cucurbit crops: current status in the Mediterranean Region

Cucurbits are among the most cultivated crops, and the most economically important species are melon (Cucumis melo L.), cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus Thumb.), squash (Cucurbita pepo L.), and pumpkin (Cucurbita spp.). These crops have become important income sources providing export and local consumption commodities in many Mediterranean countries. Increased area of cucurbits has led to the emergence of several viral diseases, which can have impacts on crop production and threaten agricultural sustainability. An overview of the most damaging cucurbit viruses in the Mediterranean area is provided to improve understanding of the diseases they cause and to emphasize effective disease management strategies. An updating of the geographical distribution of these viruses, the symptoms they cause and their means of transmission is also provided. Disease management methods and measures by farmers and phytosanitary authorities to address the virus outbreaks are outlined, including diagnostics, use of tolerant cultivars, and chemical and biological vector control. Mediterranean region farmers have learned many lessons from the damaging pandemics caused by cucurbit viruses, through the extensive published research, and this review provides a basis for managing future outbreaks of newly emerging virus infections.

Kajian Predasi Catfish terhadap Larva Nyamuk Aedes aegypti Sebagai Upaya Pencegahan Penyebaran Demam Berdarah Dengue

Aedes aegypti acts as a primary vector of the dengue virus which causes Indonesia to become a dengue-endemic country. Chemical and physical vector control methods to prevent the spread of DHF are considered less effective so that additional biological vector control is needed. The purpose of this paper is to examine the potential ability of catfish predation as Ae. aegypti vector controller. This paper was prepared by reviewing eight Indonesian research journals, eight international research journals, reports and regulations of the Ministry of Health of the Republic of Indonesia, the website of the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), the University of Florida Entomology and Nematology, and one textbook. The results showed that the predation ability of African sharptooth catfish (Clarias garipenus) was 80.3% greater on average than Cyprinus carpio, Ctenopharyngodon idella, and Oreochromis niloticus as well as the predation ability of Walking catfish (Clarias batrachus) with an average of 79.6%. larger than Anabas testudineus, Oreochromis niloticus, and Poecilia reticulata. Further experimental research to deepen scientific information on the predation ability of various catfish species against Ae. aegypti mosquito larvae are still needed. Cooperation between fields and communities is also needed to prevent the spread of dengue disease properly. Mosquito larvae eating fish belonging to catfish species, namely African sharptooth catfish (Clarias garipenus) and walking catfish (Clarias batrachus) have the potential to be a new biological vector controller because they have very high predation power compared to other mosquito larvae eating fish.

Field Efficacy of Larvivorous Fish and Pyriproxyfen Combined with Community Engagement on Dengue Vectors in Cambodia: A Randomized Controlled Trial.

ABSTRACT.Evidence on the effectiveness of low-cost, sustainable biological vector control tools for Aedes mosquitoes is limited. Therefore, the purpose of this trial was to estimate the impact of guppy fish in combination with the larvicide pyriproxyfen (PPF) (Sumilarv® 2MR) and communication for behavioral impact (COMBI) activities to reduce entomological indices in Cambodia. In this cluster randomized, controlled superiority trial, 30 clusters comprised of one or more villages each was allocated in a 1:1:1 ratio to receive either 1) all three interventions (guppies, PPF, and COMBI), 2) two interventions (guppies and COMBI), or 3) control (standard vector control). Entomological surveys among 40 randomly selected households per cluster were carried out quarterly. The primary outcome was the population abundance of adult female Aedes mosquitoes trapped using adult resting collections. In the primary analysis, adult female Aedes abundance and mosquito infection rates was aggregated over follow-up time points to give a single rate per cluster. These data were analyzed by negative binomial regression, yielding abundance ratios (ARs). The number of Aedes females was reduced roughly by half compared with the control in both the guppy, PPF, and COMBI arm (AR = 0.54; 95% CI, 0.34–0.85; P = 0.0073); and the guppy and COMBI arm (AR = 0.49; 95% CI, 0.31–0.77; P = 0.0021). The effectiveness demonstrated and extremely low cost of including fish rearing in community-based health structures suggest they should be considered as a vector control tool as long as the benefits outweigh any potential environmental concerns. Sumilarv® 2MR was also highly accepted and preferred over current vector control tools used in Cambodia.

A feedback control perspective on biological control of dengue vectors by Wolbachia infection

Controlling diseases such as dengue fever, chikungunya and zika fever by introduction of the intracellular parasitic bacterium Wolbachia in mosquito populations which are their vectors, is presently quite a promising tool to reduce their spread. While description of the conditions of such experiments has received ample attention from biologists, entomologists and applied mathematicians, the issue of effective scheduling of the releases remains an interesting problem. Having in mind the important uncertainties present in the dynamics of the two populations in interaction, we attempt here to identify general ideas for building feedback-based release strategies, enforceable to a variety of models and situations. These principles are exemplified by several feedback control laws whose stabilizing properties are demonstrated, illustrated numerically and compared, when applied to a model retrieved from [P.-A. Bliman et al., Ensuring successful introduction of Wolbachia in natural populations of Aedes aegypti by means of feedback control. J. of Math. Bio. 76(5):1269–1300, 2018]. The contribution is believed to be also of potential interest to tackle other important issues related to the biological control of vectors and pests. A crucial use of the theory of monotone dynamical systems is made in the derivations.

A novel intervention on the inhibiting effects of Catunaregam spinosa induced free radical formation and DNA damage in Aedes aegypti (Diptera: Culicidae): a verdict for new perspectives on microorganism targeted vector control approach

Plant extracts prompting free radical formation causing DNA damage among especially symbiotic microorganisms of Aedes aegypti has not been extensively examined in previous studies. Here, investigated whether: (1) it was possible to reduce the vectorial capacity by eliminating the microbial consortia of Aedes aegypti larvae, (2) the excess formation of free radical could induce damages of genomic DNA and alter the morphological appearance of Aedes aegypti larvae, and (3) which are the probable mechanisms driving the death of mosquitoes that has been treated with phytochemicals. The toxicity of Catunaregam spinosa seed extracts on the microbial community of Aedes aegypti larvae was determined as previously described. The formation of free radicals was confirmed using the ammonium molybdate method. While the GCMS method was used to assess the phytochemical analysis and the DNA lysing potential. The petroleum ether, ethanol, acetone and water extracts of Catunaregam spinosa has exhibited potent toxicity towards Aedes aegypti larvea’s gut bacterial microbiota, including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Klebsiella pneumonia, and Proteus mirabilis with strong MIC values ranging from 0.07 mg/ml to 5.9 mg/ml. Plant extract induced free radical formations and oxidative damage to DNA. The presence of the bioactive element squalene justifies the insecticidal proprieties of Catunaregam spinosa extract. This study reflects the probable mechanisms underlying the lethal effect of Catunaregam spinosa extract on Aedes aegypti, and it potential as a novel biological vector control approach.

Study on the Fauna of Aquatic Insects in Northwestern Iran

Background:Aquatic insects include groups of arthropods which at least one step of their life happens in water. Some of these insects play an important role in the transmission of various diseases to human and animals. Because there is a little information about the fauna of aquatic insects in Iran, this study was aimed to collect and identify aquatic insects in northwestern Iran.Methods:A descriptive cross sectional study was performed in July 2017 in Rivers of three villages of Osku County of East Azerbaijan Province, northwestern Iran. The specimens were collected using different methods including D frame net-collector, standard mosquito dipper, Sweep Netting and plastic pipette. The collected specimens were identified based on the systematic keys of aquatic insects.Results:Totally 285 samples were collected. Four orders including Diptera, Hemiptera, Ephemeroptera and Coleoptera were identified. Collected samples belonged to seven families of Tipulidae, Chironomidae, Corixidae, Culicidae, Hydrophilidae, Baetidae and Dytiscidae. The most predominant family was Culicidae belonging to order Diptera. Culiseta longiareolata was the most frequent species collected in the study area.Conclusion:Aquatic insects usually play an important role in the food chain of animals and some species of them act as predators and play an important role in the biological control of vectors. Therefore, more studies are required to carry out in the field of aquatic insects.

EVALUASI PELAKSANAAN PROGRAM ELIMINASI MALARIA DI KABUPATEN ACEH SINGKIL TAHUN 2018

The success of the malaria elimination program in Kabuupaten Aceh Singkil, the Annual Parasite Incident (API) per 1000 population will reach 0%. Nowadays, the frequency of implementing the program has decreased so that it is suspected that it can cause people to suffer from malaria. The purpose of the study was to analyze the evaluation of the implementation of the malaria elimination program. This type of research is qualitative. The informants consisted of 5 key informants namely the person in charge of P2P, malaria management officers, village midwives and 4 main informants namely the head of the puskesmas and village head and 6 additional informants namely the community, pregnant women, cadres. Data were analyzed by interactive methods through the stages of data reduction, presentation and drawing conclusions. The results showed that blood tests were not carried out unless the community had a fever. Distribution of delivery nets, screening for pregnant women is reduced, and biological vector control is not monitored. Epidemiological surveillance and epidemic prevention are not carried out because there are no outbreaks so monitors are made in the form of monthly reports. Educational activities in the form of outreach continue to the present and responsibilities are more focused on village midwives/cadres. Training and guidance activities for officers have never been done. The percentage of API reaches 0% in 2018. It is recommended that health workers remain vigilant and prioritize programs supporting malaria elimination programs along with other health programs through community empowerment today.

Características clínicas-epidemiológicas y conocimiento sobre la leishmaniosis tegumentaria americana en una población de Carabobo. Venezuela

De leishmaniosis tegumentaria americana se registran 1,5 millones de nuevos casos, está presente en 88 países, esto hace que ocupe el sexto lugar entre las enfermedades importantes del mundo y el segundo entre las enfermedades parasitarias únicamente detrás del paludismo, pero en América Latina son escasos los trabajos sobre conocimientos de leishmaniosis tegumentaria americana como sustento de los programas sanitarios de control la mayoría únicamente se enfocan en aspectos tales como: control químico y biológico de vectores, estudio de reservorios, seroprevalencia en áreas endémicas, tratamiento farmacológico e inmunoterapia. El objetivo determinar las características clínico-epidemiológicas y conocimiento sobre leishmaniosis tegumentaria americana. Estudio descriptivo con diseño de investigación documental y de campo, con base en la revisión de registro epidemiológico y aplicación de un cuestionario. La mayoría de los afectados son adultos jóvenes (20-59 años) (66,3%) del género masculino, obreros (27,4%) con lesiones en miembro superior (40,5%), generalmente únicas (53,4%) y tratadas (86,3%). 80% conoce la enfermedad y 83% al transmisor, y 38% conoce el tratamiento farmacológico. Se concluye que los afectados con LTA son principalmente hombres, en edad económicamente productiva, obreros y agricultores, con niveles educativos no superiores a medio diversificado, ubicados en pobreza relativa como estrato socio-económico, con lesiones de piel únicas en regiones expuestas del cuerpo y tratadas farmacológicamente; que la población conoce la historia natural de la enfermedad y el transmisor, pero desconocen aspectos de la biología del insecto; y que conocen y prefieren el tratamiento médico-farmacológico del sistema médico-científico y del servicio curativo público.

Current status and future prospects of bacilli-based vector control

Mosquito-borne diseases such as malaria, filariasis, dengue, chikungunya, Japanese encephalitis, yellow fever and Zika contribute significantly to health problems of developing as well as developed nations. Vector control is central to control of vector borne diseases. In the last four-five decades, biological control methods have been inducted in the integrated vector management strategy, advocated nationally as well as globally by the World Health Organization. Currently, biological control of vectors is globally acknowledged as the best available strategy in the wake of growing concerns about vector resistance as well as adverse effects of insecticides on the environment and non-target fauna co-inhabiting the same ecological niches as vectors. In India and elsewhere, efforts are ongoing to screen newer isolates to bring forth new biolarvicidal products of public health importance. In this review, by carrying out extensive literature survey, we discuss advances thus far and the prospects of bacilli-based control of vectors and vector borne diseases.

The Influence of Digestive Tract Length of Larvivorous Fish Related to Predation Potential on Aedes aegypti Larvae

Biological vector control by using larvivorous fish will be beneficial in reducing Aedes aegypti population, hence reducing risk of dengue virus transmission. It is important to select the larvivorous fish according to its digestive organ.Current study aimed to investigate the predation potential among the fish species and to identify the influence of the digestive tract length of the fish related to their predation potential. The research was an analytical observational study with post-test only design. Third stage larvae of Aedes aegypti were used as preys for tilapia (Oreochromis niloticus), common carper (Cyprinus carpio), and guppy (Poecillia reticulata). In association with their digestive tract length, predation potential of tilapia, common carper, and guppy showed statistical differences (P<0.05). Tilapia demonstrated highest predation of the larvae, followed by common carper and guppy. There are associations between difference in shapes of mouth and intestines, mouth width, intestinal length, and predation potential of these fish species. Current study results showed possible associations between digestive tract length of tilapia, common carper and guppy and predation potential on Aedes aegypti larvae, allowing these fish species to be used inbiological control of Aedes aegypti.

Resistance Status of Aedes aegypti to Deltamethrin, Malathion, and Temephos in Ecuador.

In Ecuador, the status of insecticide resistance for Aedes aegypti, the principal arboviral vector in the country, has not been previously evaluated. The aim of this research was to describe the resistance status of Ae. aegypti to the principal insecticides used for vector control in provinces with high reports of arboviral clinical cases. This was a descriptive study performed on Ae. aegypti collected from 2016 to 2017 in 14 localities of Ecuador. The larvae were reared and tested using bioassays applying the adulticides malathion and deltamethrin, and the larvicide temephos. The lethal concentrations were obtained for field-collected specimens and compared to the susceptible reference strain ROCK, MRA-734. Mosquitoes from all the localities showed resistance to deltamethrin and susceptibility to malathion. On the other hand, mosquitoes demonstrated resistance to the larvicide temephos in 5 of the 14 localities analyzed. The results obtained in this research may be used by healthcare decision-makers to improve vector control in Ecuador. Rotation of insecticides and alternative biological vector control strategies should be considered to manage the resistance observed in Ae. aegypti to deltamethrin and temephos. New strategies to use insecticides should also be aimed to prevent selective pressure with malathion.

Prevalence of kdr mutations and insecticide susceptibility among natural population of Aedes aegypti in West Bengal.

BackgroundAedes albopictus and Aedes aegypti are the major vectors of arboviral diseases. As effective vaccines are not available for most of the arboviral diseases, vector control by using insecticides play the key role to reduce the disease transmission. The emergence and spread of resistance to different classes of insecticides by the vectors is a major obstacle to control the disease transmission. Information about vector susceptibility to different insecticides and their mechanisms are very important for formulating proper vector control measures. The present study was designed to assess the susceptibility of Ae. aegypti against three different classes of adulticides, one larvicidal agent available and polymorphisms in the voltage-gated sodium channel (VGSC) gene related to insecticide resistance.MethodsImmature stages of Ae. aegypti were collected from three dengue endemic municipal areas of West Bengal and reared in the laboratory. Larvae and adults (F1 progeny) were used for insecticide bioassay as per WHO protocols. Knock down resistance gene (kdr) mutations were assessed by direct sequencing of PCR products.ResultsThe Ae. aegypti population was found to be susceptible to type II pyrethroids and malathion but highly resistant to DDT. A high rate of polymorphisms in the VGSC gene was observed among the collected mosquitoes. A double mutant V1016G + F1534C was found to be associated with DDT resistance but neither V1016G nor F1534C alone showed the same association. Association between the kdr mutations and the susceptibility status of pyrethroids could not be established due to very small sample size. A low to moderate level of resistance was noticed against temephos among the larval population based on WHO criteria.ConclusionThe replacement of DDT by type II pyrethroids for the management of dengue vectors is an appropriate decision taken by the national program which is supported by the findings of a higher level of resistance to DDT. Persistence of polymorphisms in the VGSC gene might be an indication of emergence of resistance against pyrethroid insecticides that should be monitored at a regular interval. Attempts should be made to determine the effectiveness of other larvicides for replacement of temephos if needed in future. Along with the chemical insecticides different biological vector control methods as well as biopesticides should also be used in vector control programmes.

A systematic review of individual and community mitigation measures for prevention and control of chikungunya virus.

BackgroundChikungunya is a mosquito-borne virus transmitted by mosquitoes from the Aedes genus. The virus, endemic to parts of Asia and Africa, has recently undergone an emergence in other parts of the world where it was previously not found including Indian Ocean Islands, Europe, the Western Pacific and the Americas. There is no vaccine against chikungunya virus, which means that prevention and mitigation rely on personal protective measures and community level interventions including vector control.Methodology/Principal findingsA systematic review (SR) was conducted to summarize the literature on individual and community mitigation and control measures and their effectiveness. From a scoping review of the global literature on chikungunya, there were 91 articles that investigated mitigation or control strategies identified at the individual or community level. Of these, 81 were confirmed as relevant and included in this SR. The majority of the research was published since 2010 (76.5%) and was conducted in Asia (39.5%). Cross sectional studies were the most common study design (36.6%). Mitigation measures were placed into six categories: behavioural protective measures, insecticide use, public education, control of blood and blood products, biological vector control and quarantine of infected individuals. The effectiveness of various mitigation measures was rarely evaluated and outcomes were rarely quantitative, making it difficult to summarize results across studies and between mitigation strategies. Meta-analysis of the proportion of individuals engaging in various mitigation measures indicates habitat removal is the most common measure used, which may demonstrate the effectiveness of public education campaigns aimed at reducing standing water.Conclusions/SignificanceFurther research with appropriate and consistent outcome measurements are required in order to determine which mitigation measures, or combination of mitigation measures, are the most effective at protecting against exposure to chikungunya virus.

Sobre la biología del Telenomus fariai Lima, 1927 (Hymenoptera: Scelionidae), parásito endófago de huevos de algunos Triatominae

A study is presented of the,outstanding aspects of the biology of Central American Telenomus fariai, an endophagolis parasite on eggs or certain Tria­tominae, found on eggs of Triatoma phyllosoma in the laboratory by Dr. Luis M, Penalver of El Salvador. The little wasp was found capable of parasitizing under experimental conditions eggs of T. dimidiata of Costa Rica, of T. phyllosoma of Mexico, of Panstrongylus chinai of Ecuador, and of P. megistus of Brasil. It proved unable to attack eggs of T. infestans of Chile, of Rhodnius prolixus of El Salvador, and of R. pallescens of Panama. The fact that it does not attack eggs of T. infestans is the only difference observed from Telenomus fariai described in Brazil by Costa Lima, other than an apparently inferior capacity for laying and shorter mean duration of life. Infestation may or may not follow the attack on eggs of hemipterae in advanced stages of development; in the negative case, death results occasionally from mechanical injury. Several counts were made of the little wasps developing within the eggs of T. phyllosoma, T. dimidiata, and P. chinai, noting the total number of insects, the number of each sex and the mean number of wasps per egg. The relation­ ship of the latter figures with the size of the host eggs was investigated, and a close relationship was found between the two values: each Telenomus requires from 0.00019 to 0.00025 gm. and from 0.178 to 0.193 mm3. With a variable temperature incubator the influence of temperature on development of Telenomus was demonstrated. At 30° C. complete development was obtained in 19 days on P. chinai and in 20 days in T. phyllosoma. At room temperature development was completed in from 32 to 42 days. Host eggs were dissected just before the parasites left them and groups of females were separated after periods of various length. It was shown that females separated after up to 1 hr. of initial contact with the male gave parth­ enogenetic progeny; fertilization, therefore, occurs after that periodo Measurements were made on females and on both types of males of Telenomus; parthenogenetic males were found to be larger than normal males, and females to be larger than either. Remarks are made on the possibility of biological control of vectors of Chagas disease.