The influence of environmental management and animal shelters in vector control of Culicoides (Diptera, Ceratopogonidae) in northeastern Brazil

Influence of meteorological and seasonal parameters on the activity of Culicoides paraensis (Diptera: Ceratopogonidae), an annoying anthropophilic biting midge and putative vector of Oropouche Virus in Rondônia, Brazilian Amazon

Biting midges of the genus Culicoides are insects of proven medical and veterinary importance, because of their role in the transmission of viruses, bacteria, protozoa and nematodes. Culicoides paraensis has been considered the main vector of the Oropouche Virus (OROV) in the urban cycle of the disease in the neotropics. Due to the great abundance of Culicoides spp. in the State of Rondônia and its epidemiological history of OROV, we investigated the biting activity in humans, the abundance as a function of meteorological parameters and seasonality, and the detection of OROV. Entomological collections occurred in three municipalities from Brazilian State of Rondônia: Porto Velho, Ariquemes, and Ouro Preto do Oeste. GLMM's were used to determine if Culicoides spp. abundance was predicted by seasonal, diurnal, and meteorological factors. Total RNA was extracted from insects and viral RNA detection was performed using the S segment as the target region of OROV via RT-qPCR. In total, 7,315 individuals were captured and identified as C. paraensis. In the dry season, 1,488 individuals (24.5%) were recorded, 4,591 (75.5%) in the rainy season, with peaks of biting activity between 4pm and 6pm. All variables showed a significative effect on the midge abundance. The rainy season, temperature between 30°C and 32°C and relative air humidity between 75% and 85% were the main predictive parameters for capturing the highest average number of insects. Our results confirm diurnal activity of C. paraensis and its greatest abundance in rainy periods. No sample was positive for the OROV, which could be explained by the virus absence in local human populations, C. paraensis as a minor vector species in the sampled localities, and probable low rate of infection of biting midges. Our findings on hourly and seasonal biting activities can provide support to intervention actions regarding vector control and surveillance of this species. This was the first study to collect and analyze biting midges in a region where human OROV cases had already been detected, but without previous information on entomovirological surveillance.

Diversity of Culicoides (Diptera: Ceratopogonidae) in Rural Settlements and Degraded Seasonal Deciduous Forests

Biting midges are widespread in Brazilian natural ecosystems. However, deforestation and other activities that impact the environment are reducing natural habitats where biting midges proliferate. The objective of this study was to verify whether there is variation in the composition, richness, abundance, and seasonality of biting midges between wild and rural environments, in a forest area with intense deforestation. Biting midges were captured using 6 traps installed at an average height of 1.5 m in the peridomicile, intradomicile, and deciduous seasonal forests, once a month from May 2012 to April 2013. In total, 2,182 specimens of 13 species of the genus Culicoides were captured. Species richness was similar in the intradomicile (13 species), forest (12), and peridomicile (11), but species diversity was greater in the peridomicile (H' = 0.803) compared with the intradomicile (H' = 0.717) and forest (H' = 0.687). The order of species dominance varied between the forest (Culicoides paucienfuscatus Barbosa > Culicoides leopodoi Ortiz > Culicoides foxi Ortiz > Culicoides ignacioi Forattini) and peridomicile + intradomicile habitats (C. paucienfuscatus > C. foxi > C. filariferus Hoffman > C. ignacioi). The activity of these dipterans was strongly influenced by meteorological variables, as biting midges are predominant in the rainy season (80.7% of specimens), when higher rainfall, relative humidity, and lower temperatures prevail. The abundance of biting midges was higher in the peridomicile + intradomicile (83.7% of specimens) compared with the degraded forest (16.3%), a result that reflects the loss of forest habitat due to intense and progressive deforestation.

Observational Characterization of the Ecological and Environmental Features Associated with the Presence of Oropouche Virus and the Primary Vector Culicoides paraenesis: Data Synthesis and Systematic Review

Oropouche virus (OROV), a member of the Orthobunyavirus genus, is an arthropod-borne virus (arbovirus) and is the etiologic agent of human and animal disease. The primary vector of OROV is presumed to be the biting midge, Culicoides paraenesis, though Culex quinquefasciatus, Cq. venezuelensis, and Aedes serratus mosquitoes are considered secondary vectors. The objective of this systematic review is to characterize locations where OROV and/or its primary vector have been detected. Synthesis of known data through review of published literature regarding OROV and vectors was carried out through two independent searches: one search targeted to OROV, and another targeted towards the primary vector. A total of 911 records were returned, but only 90 (9.9%) articles satisfied all inclusion criteria. When locations were characterized, some common features were noted more frequently than others, though no one characteristic was significantly associated with presence of OROV using a logistic classification model. In a separate correlation analysis, vector presence was significantly correlated only with the presence of restingas. The lack of significant relationships is likely due to the paucity of data regarding OROV and its eco-epidemiology and highlights the importance of continued focus on characterizing this and other neglected tropical diseases.

Cryptic Wolbachia (Rickettsiales: Rickettsiaceae) Detection and Prevalence in Culicoides (Diptera: Ceratopogonidae) Midge Populations in the United States

Culicoides midges vector numerous veterinary and human pathogens. Many of these diseases lack effective therapeutic treatments or vaccines to limit transmission. The only effective approach to limit disease transmission is vector control. However, current vector control for Culicoides midges is complicated by the biology of many Culicoides species and is not always effective at reducing midge populations and impacting disease transmission. The endosymbiont Wolbachia pipientis Hertig may offer an alternative control approach to limit disease transmission and affect Culicoides populations. Here the detection of Wolbachia infections in nine species of Culicoides midges is reported. Infections were detected at low densities using qPCR. Wolbachia infections were confirmed with the sequencing of a partial region of the 16S gene. Fluorescence in situ hybridization of Culicoides sonorensis Wirth and Jones adults and dissected ovaries confirm the presence of Wolbachia infections in an important vector of Bluetongue and Epizootic hemorrhagic disease viruses. The presence of Wolbachia in Culicoides populations in the United States suggests the need for further investigation of Wolbachia as a strategy to limit transmission of diseases vectored by Culicoides midges.

Effect of vertebrate feces on the attraction of Culicoides (Diptera: Ceratopogonidae) in an Amazonian mangrove

Biting midges are of interest to public health because they play an important role as vectors of disease-causing pathogens, as well as being a biting nuisance to humans and domestic animals. Although these insects are common in mangrove areas, they have not yet been studied in this ecosystem in the state of Maranhão (MA), Brazil. The objective of this study was to characterize the Culicoides community structure found in a mangrove swamp and verify if the use of vertebrate feces as bait interferes with their composition, richness, abundance, or seasonality. CDC light traps with vertebrate (chicken, ox, control, donkey, capuchin monkey and pig) feces baits were used to capture biting midges in a mangrove area of the Island of São Luís, MA. A total of 4,087 individuals representing 22 species of Culicoides were captured, the most abundant being C. (Oecacta) furens Poey (23.46%), C. (gr. Fluviatilis) leopoldoi Ortiz (21.58%), C. (Hoffmania) ignacioi Forattini (16.98%), C. (Hoffmania) maruim Lutz (13.85%), C. (Diphaomyia) iriartei Fox (10.57%), C. (Hoffmania) insignis Lutz (7.07%), and C. (gr. Limai) limai Barreto (3.03%). Species richness and abundance were higher when baits of capuchin monkey (15 species; 26.84% of the individuals) and pig (15; 25.3%) feces were used. The least attractive baits were donkey (12 species; 9.3%) and ox (nine species; 11.52%) feces. Biting midges were more abundant in the rainy season (67%), but richness was higher in the dry season (19 species). These results show that vertebrate feces may serve as olfactory cues and increase the attraction of biting midges to traps.

Effects of forest degradation on the sand fly communities of northeast Brazil

The richness and abundance of sand fly species were studied in northeastern Brazil in areas of leishmaniasis transmission. The study was carried out in two forest areas with different deforestation times for agricultural and livestock activities: one modified by long-term settlement (more than 50 years of occupation) and another less impacted by short-term settlement (10 years). The sand flies were captured with CDC light traps from 18:00 to 06:00 for three consecutive nights, once a month, from May, 2012 to April, 2014. The study captured 21,708 specimens and also 33 species of Lutzomyia and two of Brumptomyia. Species richness and abundance were higher in the more conserved area of short-term occupation (31 species; 61.7%) than in the more degraded area with long-term occupation (17 species; 38.3%). In the most conserved area, the species richness was higher in the forest fragment than in the rural settlement, whereas in the degraded area the richness was higher in the peri-domicile than in the forest. The diversity was higher in the degraded area forest. There were significant statistical differences when comparing the means of total abundance with the intra-domicile, peri-domicile, and forest environments. The average abundance was statistically higher in the peri-domicile compared to the forest (p = 0.009), but there were no statistically significant differences between intra-domicile-peri-domicile (p = 0.11) and forest-intra-domicile (p = 0.87). In conclusion, a change in vegetation cover negatively affects the richness and abundance of sand flies in the natural environment.

Transfection of Culicoides sonorensis biting midge cell lines with Wolbachia pipientis

Background

Biting midges of the genus Culicoides vector multiple veterinary pathogens and are difficult to control. Endosymbionts particularly Wolbachia pipientis may offer an alternative to control populations of Culicoides and/or impact disease transmission in the form of population suppression or replacement strategies.

Methods

Culicoides sonorensis cell lines were transfected with a Wolbachia infection using a modified shell vial technique. Infections were confirmed using PCR and cell localization using fluorescent in situ hybridization (FISH). The stability of Wolbachia infections and density was determined by qPCR. qPCR was also used to examine immune genes in the IMD, Toll and JACK/STAT pathways to determine if Wolbachia were associated with an immune response in infected cells.

Results

Here we have transfected two Culicoides sonorensis cell lines (W3 and W8) with a Wolbachia infection (walbB) from donor Aedes albopictus Aa23 cells. PCR and FISH showed the presence of Wolbachia infections in both C. sonorensis cell lines. Infection densities were higher in the W8 cell lines when compared to W3. In stably infected cells, genes in the immune Toll, IMD and JAK/STAT pathways were upregulated, along with Attacin and an Attacin-like anti-microbial peptides.

Conclusions

The successful introduction of Wolbachia infections in C. sonorensis cell lines and the upregulation of immune genes, suggest the utility of using Wolbachia for a population replacement and/or population suppression approach to limit the transmission of C. sonorensis vectored diseases. Results support the further investigation of Wolbachia induced pathogen inhibitory effects in Wolbachia-infected C. sonorensis cell lines and the introduction of Wolbachia into C. sonorensis adults via embryonic microinjection to examine for reproductive phenotypes and host fitness effects of a novel Wolbachia infection.

Bluetongue disease in sheep: a review

ABSTRACT The present review aims to show the main aspects related to bluetongue virus (BTV) infection in sheep. The bluetongue (BT) is a viral, infectious, and non-contagious disease caused by a virus (BTV) of the Orbivirus genus, transmited by a hematophagous vector of the Culicoides genus, to domestic and wild ruminants, mainly to sheep, the most susceptible species. It is caused by the association of endemic with climate conditions, with high temperatures and humidity. Economic loss is directly linked to death, abortion, weight loss, loss of milk, and meat production, and, indirectly, to the restriction on the export of animals and their by-products. The study concludes that the BTV is worldwidely spread, and probably persists due to the warm and humid climate that leads to the proliferation of Culicoides sp., being necessary to adopt measures that reduce the risk factors associated to the BTV infection.

Projected economic losses due to vector and vector-borne parasitic diseases in livestock of India and its significance in implementing the concept of integrated practices for vector management

Broadly, species of arthropods infesting livestock are grouped into flies (biting and non-biting), fleas, lice (biting and sucking), ticks (soft and hard), and mites (burrowing, non-burrowing, and follicular). Among which, biting and non-biting flies and ticks are the potent vectors for many bacterial, viral, rickettsial, and protozoan diseases. Vectors of livestock are having economic significance on three points (1) direct losses from their bite and annoyance, worries, and psychological disturbances produced during the act of biting and feeding, (2) diseases they transmit, and (3) expenditure incurred for their control. Flies such as Culicoides spp. and Musca spp. and various species of hard ticks play important role in disease transmission in addition to their direct effects. For control of vectors, recent concept of integrated pest management (IPM) provides the best solution and also addresses the problems related to acaricide resistance and environmental protection from hazardous chemicals. However, to successfully implement the concept of IPM, for each vector species, estimation of two monitory benchmarks, i.e., economic injury level (EIL) and economic threshold level (ETL) is essential prerequisite. For many vector species and under several circumstances, estimation of EIL and ETL appears to be difficult. Under such scenario, although may not be exact, an approximate estimate can be accrued by taking into account several criteria such as percent prevalence of vectors in a geographical area, percent losses produced, total livestock population, and current prices of livestock products such as milk, meat, and wool. Method for approximate estimation is first time described and elaborated in the present review article.