Culicid Mosquitoes Research Articles

Prediction and validation of potential transmission risk of Dirofilaria spp. infection in Serbia and its projection to 2080.

Animal and human dirofilariosis is a vector-borne zoonotic disease, being one of the most important diseases in Europe. In Serbia, there are extensive studies reporting the presence of Dirofilaria immitis and D. repens, mainly in the north of the country, where the human population is concentrated and where there is a presence of culicid mosquitoes that transmit the disease. Ecological niche modeling (ENM) has proven to be a very good tool to predict the appearance of parasitosis in very diverse areas, with distant orography and climatologies at a local, continental, and global level. Taking these factors into account, the objective of this study was to develop an environmental model for Serbia that reflects the suitability of the ecological niche for the risk of infection with Dirofilaria spp. with which the predictive power of existing studies is improved. A wide set of variables related to the transmission of the parasite were used. The potential number of generations of D. immitis and the ecological niche modeling method (ENM) were used to estimate the potential distribution of suitable habitats for Culex pipiens. The highest probability of infection risk was located in the north of the country, and the lowest in the southern regions, where there is more orographic relief and less human activity. The model was corroborated with the location of D. immitis-infected dogs, with 89.28% of the country having a high probability of infection. In addition, it was observed that the percentage of territory with optimal habitat for Culex spp. will increase significantly between now and 2080. This new model can be used as a tool in the control and prevention of heartworm disease in Serbia, due to its high predictive power, and will serve to alert veterinary and health personnel of the presence of the disease in the animal and human population, respectively.

Ecological niche modeling analysis (Cx. pipiens), potential risk and projection of Dirofilaria spp. infection in Greece

Vector-borne diseases continue to increase worldwide. Dirofilariosis is one of the most common vector-borne zoonotic diseases, mainly caused by Dirofilaria spp. (D. immitis and D. repens) and spread by culicid mosquitoes of different species. Greece is one of the countries in southern Europe where it is traditionally endemic, and its distribution is not homogeneous. The aim of this study was to develop an environmental model for Greece that reflects the suitability of the ecological niche for Dirofilaria spp. infection risk and its projection until 2080. For this purpose, we used the potential distribution of suitable habitats for Culex pipiens calculated using an ecological niche model (ENM) and the potential number of generations of Dirofilaria spp. The ecological niche model of Cx. pipiens in Greece showed good predictive power (AUC=0.897) with the parasite at a resolution of 1 km2. The variables that contributed most to the model were mean annual temperature, rivers and human footprint. The highest risk of infection was found in coastal areas and in riverside areas of the main river basins, as well as in irrigated areas of the mainland and peninsular regions and in the whole territory of island areas, and the lowest risk was found in areas of higher altitude. A positive relationship was found between the risk of dirofilariosis and the location of infected dogs, with 86.65% located in very high and high risk areas. In 2080, the percentage of territory gained by Cx. pipiens will increase by 261.52%. This model provides a high predictive value, predicted presence, and risk of Dirofilaria spp. infection and can serve as a tool for the management and control of this disease.

Diversity patterns along ecological succession in tropical dry forests: a multi‐taxonomic approach

Evaluating the diversity of multiple taxa is fundamental to understand community assembly and to assess the integrity and functionality of tropical secondary forests. In this study, we analyzed the natural regeneration of tropical dry forests (TDFs) in three regions of Brazil using Hill–Simpson diversity, abundance and β‐diversity of trees and five groups of insects (herbivores, fruit‐feeding butterflies, ants, culicid mosquitoes and dung beetles). Sampling was conducted in 39 0.1 ha plots using a chronosequence approach (13 plots in early, intermediate and old‐growth forests). We evaluated the contribution of three different levels to γ‐diversity: α (within plots), β1 (among plots) and β2 (among successional stages), and further determined the relative importance of turnover (species replacement) and nestedness (differences in species number among sites) to β2. Our results showed that, unexpectedly, the Hill–Simpson diversity was consistently higher in early than old‐growth stages for all regions, but varied more widely in the intermediate stages. For each group separately, the same trend was observed for butterflies, ants, dung beetles and herbivores and did not differ among stages for mosquitoes. Successional differences in abundance were only detected for trees (increasing along the gradient) and for mosquitoes (decreasing). According to our expectations, the additive partitioning analysis showed that β2‐diversity contributed more to γ‐diversity than β1‐diversity, when all taxa were considered together and for most of them separately (except for butterflies and dung beetles). Most of the β2‐diversity was due to species turnover, but this contribution varied among groups and regions, with the highest turnover for herbivores and the lowest for dung beetles. Our results suggest that the Hill–Simpson diversity and changes in species composition (as given by β2‐diversity) are better indicators of forest natural regeneration than raw species richness, corroborating previous studies with plants and animals.

Current Risk of Dirofilariosis Transmission in the Iberian Peninsula (Spain and Portugal) and the Balearic Islands (Spain) and Its Future Projection under Climate Change Scenarios.

Dirofilariosis is a vector-borne zoonotic disease whose distribution is linked to the presence of culicid mosquitoes. Spain and Portugal are considered endemic countries; however, the distribution of dirofilariosis is not uniform. Our aim was to develop a more accurate risk model of dirofilariosis transmission for the Iberian Peninsula (Spain and Portugal) and the Balearic Islands (Spain). To do this, we used a set of key variables related to parasite transmission: the potential distribution of suitable habitats for Culex pipiens calculated via an ecological niche model (ENM) and the potential number of Dirofilaria spp. generations. The resulting model was validated with the prevalence and geolocation of D. immitis-infected dogs from all provinces and districts. In addition, the impact of possible future climatic conditions was estimated. A quantitative estimate of the risk of infection by Dirofilaria spp. was obtained at a resolution of 1 km2. The entire analyzed territory was susceptible to contact with the parasite. The highest risk of infection was found throughout the eastern coastal strip and the south of the Iberian Peninsula and the Balearic Islands, as well as in the areas surrounding the basins of the main rivers, and the lowest risk was located in the higher-altitude areas. We found a robust and positive relationship between the risk of dirofilariosis and the observed prevalence of infested dogs in the study area (β ± SE = 3.32 ± 1.43 p < 0.05). In 2080, the percentage of territory gain for Cx. pipiens will increase to 49.98%, which will increase the risk of infection. This new model provides a high predictive value for the current and predicted presence and risk and can serve as a tool for the management and control of dirofilariosis.

Optimization of adult mosquito trap settings to monitor populations of Aedes and Culex mosquitoes, vectors of arboviruses in La Reunion

Competent arbovirus vectors are found in the culicid mosquito fauna of south-west Indian Ocean (SWIO) islands. In La Reunion, Aedes albopictus and Aedes aegypti mosquitoes are known vectors of dengue and chikungunya viruses. Culex quinquefasciatus is a potential vector of Rift Valley fever and West Nile viruses. To prepare a vector-control field trial against Ae. aegypti, this study aimed at identifying the best trapping strategy to catch adult Ae. aegypti, using BG-Sentinel traps (Biogents, Germany). It was implemented in two sites in southern La Reunion. Catches of Ae. albopictus and Cx. quinquefasciatus mosquitoes were also recorded. A Latin square design was used to estimate the detection probability and the apparent daily density—according to the BG-Sentinel trapping strategy: none, carbon dioxide (CO2), a commercial attractant—BG-Lure (Biogents, Germany), or both. The use of CO2 alone was associated with a higher detection probability for Ae. aegypti and Cx. quinquefasciatus mosquitoes, as well as a large increase in their apparent density. Traps with BG-Lure—alone or in combination with CO2, did not improve the detection probability of Ae. aegypti and Cx. quinquefasciatus mosquitoes. The same result was found for male Ae. albopictus. For females, baiting BG-Sentinel traps with CO2 or BG-Lure had no significant effect. The same apparent densities were found for Ae. aegypti and Ae. albopictus mosquitoes in both study sites—where Ae. aegypti mosquitoes were found at very low densities during previous surveys.

PREDATORY EFFECT AND SELECTIVITY OF PREY OF NOTONECTA PERUVIANA (HEMIPTERA: NOTONECTIDAE) ON THE LARVAL CONTROL OF MOSQUITOES (DIPTERA: CULICIDAE)

The larval stage of culicid mosquitoes are the main food resource of notonectides in aquatic systems. Prey alternation and abundance can significantly affect predator-prey interaction and functional response (FR). We evaluated the effect of predation and prey selectivity of Notonecta peruviana in fourth-stage larvae (F1) of Aedes aegypti and Culex quinquefasciatus at different densities and two test systems: one prey and the combination of both (ratio 1: 1). We used the FR protocol to measure predation and the Manly preference index () to evaluate the selectivity of prey, in a CRD experimental design. N. peruviana generated type II RF (“concave model”) of greater impact in larvae of Ae. aegypti (p ≤ 0.01). Predation capacity was similar in both of the prey, 17 ± 4 larvae / day in Cx. quinquefasciatus and 21 ± 4 in Ae. aegypti. The attack coefficient (a), turned out to be similar for both prey species in both test systems and the handling time (Th) was lower for Ae. aegypti than for Culex. Notonecta peruviana demonstrated selectivity for larvae of Ae. aegypti especially at the highest densities (≥ 0.5), attributed to the inefficient anti depredation response, active mobility and smaller size compared to those of Cx. quinquefasciatus. The FR demonstrated the success of N. peruviana in the larval control of culicid mosquitoes, prioritizing the type of prey; thus, promoting the need for its applicability in the field.

A chorus for a feast

Frog-biting midges (Corethrella sp) and culicid mosquitoes were observed feeding on a hylid frog (Boana caiapo; top) in northern Mato Grosso, Brazil. Although in popular folklore flies and their relatives are commonly preyed upon by frogs and toads, several dipterans – including corethrellid midges – are specialized anuran parasites. The female midges track frog calls to locate potential hosts, from which they feed and ingest a blood meal (note the blood-filled abdomens of some individuals surrounding the frog’s eyes and nostrils). Corethrellid midges may also transmit trypanosomes (parasitic protozoa) to anurans, and variations in midge abundance caused by environmental changes warrant further research, as they may have important consequences for amphibian conservation. Phonotaxis (movement cued by sound) practiced by midges is directly related to the prevalence of bites on anterior portions of frogs, whereas the more generalist culicid mosquitoes, which are attracted to their hosts by CO2, often bite opportunistically over a frog’s body. Circular pale marks commonly observed on frogs of the Boana geographica species group (such as these on what resembles B semilineata but may be another Boana species; bottom) are typically caused by mosquito bites. The broader ecological implications of relationships between anurans and dipterans remain largely unknown.

Species Variety of the Calf and Human-Attracted Mosquitoes in Southwest Iran.

Background:Any mosquito control methods requires precise information about population dynamics, variety, biology and mosquito habitat. This research assessed Culicid mosquitoes’ attraction to a human host and a calf to better understand their behavior.Methods:Adult mosquitoes were sampled in 22 weeks in southwestern Iran’s Nur Ali Village from May to October 2015. The mosquitoes were drawn to the person and calf as bait, while the unbaited trap was also used. A substantial statistical difference between attracted mosquitoes to the hosts was determined in the T-test.Results:Within 22 weeks, 29821 mosquitoes were captured. Only 9% were collected from the human baited net trap, 89.1% from the calf baited net trap, and 1.9% from the unbaited net trap. The number of collected female mosquitoes was statistically significantly higher using the calf baited net trap of the total mosquitoes, 916 were randomly identified at the species level by local identification keys. Of these, 63 were Anopheles stephensi (human: 16%, calf: 75% and unbaited: 9%), 83 An. pulcherrimus (human: 27%, calf: 60% and unbaited: 13%), 118 Aedes caspius (human: 24%, calf: 69% and unbaited: 7%), 493 Culex tritaeniorhynchus (human: 52%, calf: 37% and unbaited: 11%), 153 Cx. quinquefasciatus (human: 44%, calf: 47% and unbaited: 9%), and 6 Cx. theileri (human: 33%, calf: 50% and unbaited: 17%).Conclusion:The obtained results here provide useful insights into the mosquito population and the possibility of using this information as an essential part of integrated vector management regarding the reemergence of malaria or other mosquito-borne.

In vivo Evaluation of the Repellency Effects of Nanoemulsion of Mentha piperita and Eucalyptus globulus Essential Oils against mosquitoes

Introduction: The present study aimed to prepare Nanoemulsions of Mentha piperita and Eucalyptus globulus essential oils and comparison of the repellant activity of them with normal essential oils and DEET in the field conditions. Methods: To determine the protection and failure time of the essential oils and DEET in the field condition against natural population of night biting culicid mosquitoes, 4 human volunteers participated in night biting test. GC-MS was used to determine the essential oil components and the Dynamic Light Scattering device was used to measure droplet size and zeta potential. Results: The relative abundance of more common species captured in this study was 40.09% and 31.65% for Anopheles superpictus, and Culex pipiens, respectively. Based on the results, the protection time of nanoemulsions of M. piperita 50% against night biting mosquitoes was 4.96±0.21 h. Also, the protection for nanoemulsions essential oil 50% of E. globulus was 6.06±0.20 h. Comparison of the results showed that the protection time of nanoemulsions of M. piperita and E. globulus was significantly higher than of their normal essential oils (P˂0.01). Also, the protection time of DEET (as a gold standard) was significantly higher than of normal essential oil and nanoemulsions of M. piperita (P˂0.01), but there is no significant difference between DEET and nanoemulsions of E. globulus (P˃0.01). Conclusion: Due to the safety and biocompatibility of the nanoessential oils, and also relatively adequate and acceptable protection time, nanoemulsions of E. globulus and probably M. piperita can be considered as good repellents. It is recommended to do more research on these nanoemulsion repellents, as they may be good alternatives to DEET.

Molecular characterization of ocular dirofilariasis: a case report of Dirofilaria immitis in south-eastern Iran

BackgroundDirofilariasis is a zoonotic parasitic infection transmitted from animals to humans by culicid mosquitoes. Although the disease can be caused by Dirofilaria spp. including Dirofilaria immitis and Dirofilaria repens, human ocular dirofilariasis due to D. immitis is relatively rare in the world. This study was aimed to present a case of ocular dirofilariasis caused by D. immitis in southeastern Iran.Case presentationA nematode extracted from the right eye of a 69-year-old man referred with clinical symptoms including itching and redness was examined. After the morphometric analysis, Dirofilaria parasite was detected. Afterwards, a piece of worm body was cut and DNA was extracted and a 680-bp gene fragment amplification and nucleotide sequencing were performed. Phylogenetic analysis revealed a D. immitis roundworm as the causative agent of infection. The patient was treated with antibiotics and corticosteroid and followed up for 1 month.ConclusionThe present study provides the second report on ocular dirofilariasis caused by D. immitis isolated from a human in southeast Iran. Based on the available evidence, dirofilariasis in dogs has significantly increased in endemic areas such as Iran. Therefore, physicians should be aware of such zoonotic nematodes so as to take proper and timely action and treatment against the disease.

Short Communication: Species diversity, habitat and abundance of Culicid mosquitoes in Bushehr Province, South of Iran

Abstract. Khoobdel M, Keshavarzi D, Sobat H, Akbari M. 2020. Short Communication: Species diversity, habitat and abundance of Culicid mosquitoes in Bushehr Province, South of Iran. Biodiversitas 21: 1401-1406. Culicid-borne diseases are causes of substantial illness worldwide. Effective culicid control depends on up-to-date knowledge of ecology and dispersal of species. Hence, this entomological study was conducted from January - December 2017 to provide baseline data on the distribution and ecology of mosquitoes in the Southwest of Iran. In total, 2530 specimens belonging to 14 different species were collected and identified, as follows: Culex hortensis, Cx. laticinctus, Cx. mimeticus, Cx. perexiguus, Cx. pipiens, Cx. modestus, Cx. sinaiticus, Cx. theileri, Cx. torrentium, Cx. tritaeniorhynchus, Anopheles stephensi, An. superpictus, An.dthali, and An.subpictus. Diversity analysis indicated higher species richness for uninhabited areas (Margalef 1/86). The average of Shannon diversity index ranged from 1.98 to 2.10. Differences between urban and uninhabited areas were significant according to the diversity t-test (P = 0.024, t = 2.26). The analysis of beta biodiversity showed that rural and uninhabited areas were the closest environments in their specific composition (Whittaker index = 0.130). These findings could be useful in vector control program.

The use of wing shape for characterising macroevolution in mosquitoes (Diptera: Culicidae)

The wing form of culicid mosquitoes shows considerable variation among groups: this phenomenon has been addressed by several studies through space-time analyses in mosquito populations, species, and genera. The observed variation results from a combination of two distinct factors: heredity and phenotypic plasticity. The first is usually related to wing shape, a complex character that may serve as a taxonomic marker in specific cases. We hypothesized that wing shape might be phylogenetically meaningful in Culicidae. In this study, we applied a geometric morphometrical approach based on 18 landmarks in 81 species of mosquitoes, representing 19 different genera, to investigate whether wing shape can help retrieve macroevolutionary patterns or identify any phylogenetic signals. We observed that wing shape differed considerably among groups, especially between Anophelinae and Culicinae subfamilies; thus, some wing shape elements may be synapomorphic. Comparisons among wing consensus after Procrustes superimposition revealed that landmark #1, located between the veins RS and R1, was the most variable. Sabethini tribe was distinguished from other taxa owing to a strong phylogenetic signal of its wings, whereas other culicids presented weaker signals and were not that distinguishable. Evolutionary forces such as natural selection, evolutionary limitation/constraint, or canalization mechanisms might drive the evolution of wing phenotype. These findings suggest that the wing undergoes evolution over long periods, but is not neutral enough to reconstruct the phylogenetic history of these insects. Gene-based studies should be performed to understand the driving forces in wing evolution.

Use of anthropophilic culicid-based xenosurveillance as a proxy for Plasmodium vivax malaria burden and transmission hotspots identification.

Vector-borne diseases account for more than 17% of all infectious diseases, causing more than one million deaths annually. Malaria remains one of the most important public health problems worldwide. These vectors are bloodsucking insects, which can transmit disease-producing microorganisms during a blood meal. The contact of culicids with human populations living in malaria-endemic areas suggests that the identification of Plasmodium genetic material in the blood present in the gut of these mosquitoes may be possible. The process of assessing the blood meal for the presence of pathogens is termed ‘xenosurveillance’. In view of this, the present work investigated the relationship between the frequency with which Plasmodium DNA is found in culicids and the frequency with which individuals are found to be carrying malaria parasites. A cross-sectional study was performed in a peri-urban area of Manaus, in the Western Brazilian Amazon, by simultaneously collecting human blood samples and trapping culicids from households. A total of 875 individuals were included in the study and a total of 13,374mosquito specimens were captured. Malaria prevalence in the study area was 7.7%. The frequency of households with at least one culicid specimen carrying Plasmodium DNA was 6.4%. Plasmodium infection incidence was significantly related to whether any Plasmodium positive blood-fed culicid was found in the same household [IRR 3.49 (CI95% 1.38–8.84); p = 0.008] and for indoor-collected culicids [IRR 4.07 (CI95%1.25–13.24); p = 0.020]. Furthermore, the number of infected people in the house at the time of mosquito collection was related to whether there were any positive blood-fed culicid mosquitoes in that household for collection methods combined [IRR 4.48 (CI95%2.22–9.05); p<0.001] or only for indoor-collected culicids [IRR 4.88 (CI95%2.01–11.82); p<0.001]. Our results suggest that xenosurveillance can be used in endemic tropical regions in order to estimate the malaria burden and identify transmission foci in areas where Plasmodium vivax is predominant.

A dipteran larva-pitcher plant digestive mutualism is dependent on prey resource digestibility.

Positive species interactions tend to be context dependent. However, it is difficult to predict how benefit in a mutualism changes in response to changing contexts. Nepenthes pitcher plants trap animal prey using leaf pitfall traps known as pitchers. Many specialized inquiline organisms inhibit these pitchers, and are known to facilitate the digestion of prey carcasses in them. Nepenthes gracilis traps diverse arthropod prey taxa, which are likely to differ greatly in the ease with which they may be digested, independently of inquilines, by plant enzymes. In this study, we used in vitro experiments to compare the nutritional benefit provided by phorid (scuttle fly) and culicid (mosquito) dipteran larvae to their host, N. gracilis, and to each other. The effects of phorids on N. gracilis nutrient sequestration were very variable, being positive for large prey which have low digestibility, but negative for small prey which are highly digestible. However, the effect of culicids on N. gracilis and the effects of culicids and phorids on each other were not significantly altered by prey type. These results show that a digestive mutualism is highly dependent on the digestibility of the resource-a context dependency that conforms well to the predictions of the stress-gradient hypothesis in facilitation research. Our findings have significant implications for many other digestive mutualisms, and also suggest that greater insights may be gained from the synthesis of concepts between the fields of mutualism and facilitation research.

Dirofilaria immitis Microfilariae and Third-Stage Larvae Induce Canine NETosis Resulting in Different Types of Neutrophil Extracellular Traps.

Heartworm disease is a zoonotic vector-borne disease caused by Dirofilaria immitis mainly affecting canids. Infectious third-stage larvae (L3) are transmitted to the definitive hosts via culicid mosquitoes; adult nematodes reside in the pulmonary arteries and in the right heart releasing unsheathed first-stage larvae (microfilariae) into the bloodstream leading to chronic and sometimes fatal disease. So far, early innate immune reactions triggered by these different D. immitis stages in the canine host have scarcely been investigated. Therefore, D. immitis microfilariae and L3 were analyzed for their capacity to induce neutrophil extracellular traps (NETs) in canine polymorphonuclear neutrophils (PMN). Overall, scanning electron microscopy analysis revealed both larval stages as strong inducers of canine NETosis. Co-localization of PMN-derived extracellular DNA with granulocytic histones, neutrophil elastase, or myeloperoxidase in parasite-entrapping structures confirmed the classical characteristics of NETosis. Quantitative analyses showed that both larval stages triggered canine NETs in a time-dependent but dose-independent manner. Moreover, parasite-induced NET formation was not influenced by the parasites viability since heat-inactivated microfilariae and L3 also induced NETs. In addition, parasite/PMN confrontation promoted significant entrapment but not killing of microfilariae and L3. Both, NETosis and larval entrapment was significantly reversed via DNase I treatments while treatments with the NADPH oxidase inhibitor diphenyleneiodonium failed to significantly influence these reactions. Interestingly, different types of NETs were induced by microfilariae and L3 since microfilarial stages merely induced spread and diffuse NETs while the larger L3 additionally triggered aggregated NET formation.

AN UPDATED CHECKLIST OF THE MOSQUITOES FROM SOUTH SUMATRA PROVINCE WITH A NEW RECORD OF AEDES (DOWNSIOMYIA) PEXUS COLLESS, 1958 (DIPTERA: CULICIDAE) IN INDONESIA

Data of mosquito fauna is important to be known as basic effort in vector mosquito control. It is necessary to update the data from time to time. The effort of updating the mosquito fauna was started from South Sumatra Province. Amount of 2,784 mosquito specimens were examined. The result showed there are 62 species of mosquitoes from South Sumatra Province and they belong to 10 genera. One species of culicid mosquito were recorded for the first time from Indonesia, namely Aedes (Downsiomyia) pexus and six other species were first recorded on Sumatra Island. These species are now included in the Sumatran Culicidae checklist.

&lt;b&gt;Pupal shape and size dimorphism in &lt;I&gt;Aedes albopictus&lt;/I&gt; (Skuse, 1894) (Diptera: Culicidae)&lt;/b&gt;

Aedes albopictus (Skuse, 1894) is a culicid mosquito associated with the transmission of pathogens causative for dengue, yellow fever, chikungunya, Mayaro and other diseases. Several recent studies have proposed that demographic surveys of dengue vector pupae are more useful than traditional larval indices for estimating populations. Geometric morphometrics is a tool for describing phenotypic variation that has been validated for characterizing sexual dimorphism. We undertook to apply this method to describe sexual and morphological dimorphism in A. albopictus pupae. Two-dimensional co-ordinates were digitalized from 60 specimens in two stages using 10 landmarks in pupae and 14 in wings. Configuration matrices were aligned by generalized procrustes analysis to extract matrix configurations and centroid size (CS). A discriminant analysis (DA) was used to test group (female or male) membership significance, and non-parametric ANOVA was used for CS differences. We found significant differences (Kruskal-Wallis P &lt; 0.01) among pupal cephalothorax CS and adult wings; female pupae and adults were larger than males. The DA for cephalothorax and wing specimens showed significant differences (Hotelling P &lt; 0.0001) between females and males. Through cross-validation, females and males were correctly classified with greater than 90% accuracy using the conformation characteristics described. Our study is the first description of phenotypic variation of pupal shape and size in A. albopictus laboratory colonies, and the results can be used as an additional tool in dengue entomological survey programs. More studies are necessary to confirm the variation between natural and laboratory populations.

The Complexity of Zoonotic Filariasis Episystem and Its Consequences: A Multidisciplinary View.

Vector-borne transmitted helminthic zoonosis affects the health and economy of both developing and developed countries. The concept of episystem includes the set of biological, environmental, and epidemiological elements of these diseases in defined geographic and temporal scales. Dirofilariasis caused by different species of the genus Dirofilaria is a disease affecting domestic and wild canines and felines and man, transmitted by different species of culicid mosquitoes. This complexity is increased because Dirofilaria species harbor intracellular symbiont Wolbachia bacteriae, which play a key role in the embryogenesis and development of dirofilariae and in the inflammatory pathology of the disease. In addition, the vector transmission makes the dirofilariasis susceptible to the influence of the climate and its variations. The present review addresses the analysis of dirofilariasis from the point of view of the episystem, analyzing the complex network of interactions established between biological components, climate, and factors related to human activity, as well as the different problems they pose. The progress of knowledge on human and animal dirofilariasis is largely due to the multidisciplinary approach. Nevertheless, different aspects of the disease need to continue being investigated and cooperation between countries and specialists involved should be intensified.

A Mixture of Bacillus thuringiensis subsp. israelensis With Xenorhabdus nematophila -Cultured Broth Enhances Toxicity Against Mosquitoes Aedes albopictus and Culex pipiens pallens (Diptera: Culicidae).

Xenorhabdus and Photorhabdus spp. (Enterobacteriaceae) can synthesize and release secondary metabolites that play crucial roles in their pathogenicity by suppressing the immunity of target insects. The insect immunity contributes to defense against the pathogenicity of Bacillus thuringiensis (Bt). This study tested a hypothesis that bacterial immunosuppresants could enhance the susceptibility of mosquitoes ( Aedes albopictus and Culex pipiens pallens ) to Bt. Three symbiotic bacteria [ X. nematophila (Xn), X. hominickii (Xh), and P. temperata temperata (Ptt)] were cultured in nutrient broth to allow them to produce secondary metabolites. Bacillus thuringiensis israelensis (BtI) was highly toxic to both culicid mosquitoes with median lethal concentration (LC 50 , spores/ml) of 2.9 × 10 5 and 2.2 × 10 5 at 16 h after treatment, respectively. Addition of each bacteria-cultured broth enhanced BtI toxicity to these mosquito larvae. The LC 50 values of BtI to Ae. albopictus larvae were reduced to 1.5 × 10 5 in Xn mixture, 1.7 × 10 5 in Xh mixture, and 1.9 × 10 5 in Ptt mixture. The LC 50 values of BtI to Cx. pipiens pallens larvae were also reduced to 1.2 × 10 5 in Xn mixture, 1.3 × 10 5 in Xh mixture, and 1.5 × 10 5 in Ptt mixture. Adding benzylideneacetone or oxindole produced from Xn and Ptt also enhanced BtI toxicities to these mosquito larvae. Based on these results, we developed a new mosquitocidal Bt formulation called "Dip-Kill" consisting of 80% Xn-cultured broth, 10% BtI (10 10 spores/ml), and 10% preservative. Dip-Kill at 1,000 ppm was superior to a commercial BtI product at its recommended dose.

Association of vectors and environmental conditions during the emergence of Peruvian horse sickness orbivirus and Yunnan orbivirus in northern Peru.

Since 1983, cases of diseased donkeys and horses with symptoms similar to those produced by alphaviruses were identified in two departments in northern Peru; however serological testing ruled out the presence of those viruses and attempts to isolate an agent were also unproductive. In 1997, also in northern Peru, two new orbiviruses were discovered, each recognized as a causative agent of neurological diseases in livestock and domestic animals and, at the same time, mosquitoes were found to be infected with these viruses. Peruvian horse sickness virus (PHSV) was isolated from pools of culicid mosquitoes, Aedes serratus and Psorophora ferox, and Yunnan virus (YUOV) was isolated from Aedes scapularis in the subtropical jungle (upper jungle) located on the slope between the east side of the Andes and the Amazonian basin in the Department of San Martín. Both viruses later were recovered from mosquitoes collected above the slope between the west side of the Andes and the coast (Department of Piura) in humid subtropical areas associated with the Piura River basin. In this region, PHSV was isolated from Anopheles albimanus and YUOV was isolated from Ae. scapularis. We discuss the ecology of vector mosquitoes during the outbreaks in the areas where these mosquitoes were found.