Detection and Establishment of Aedes notoscriptus (Diptera: Culicidae) Mosquitoes in Southern California, United States.

Aedes notoscriptus (Skuse), the Australian backyard mosquito, is a pestiferous daytime-biting species native to Australia and the surrounding southwestern Pacific region. It is suspected to play a role in the transmission of several arboviruses and is considered a competent vector of dog heartworm, Dirofilaria immitis (Leidy). This highly adaptable mosquito thrives in natural and artificial water-holding containers in both forested and urbanized areas, from tropical to temperate climates, and has benefitted from a close association with humans, increasing in abundance within its native range. It invaded and successfully established in New Zealand as well as in previously unoccupied temperate and arid regions of Australia. Ae. notoscriptus was discovered in Los Angeles County, CA, in 2014, marking the first time this species had been found outside the southwestern Pacific region. By the end of 2019, immature and adult mosquitoes had been collected from 364 unique locations within 44 cities spanning three southern California counties. The discovery, establishment, and rapid spread of this species in urban areas may signal the global movement and advent of a new invasive container-inhabiting species. The biting nuisance, public health, and veterinary health implications associated with the invasion of southern California by this mosquito are discussed.

Infection risk varies within urbanized landscapes: the case of coyotes and heartworm.

BACKGROUND: Urbanization can have profound effects on ecological interactions. For host-pathogen interactions, differences have been detected between urban and non-urban landscapes. However, host-pathogen interactions may also differ within highly heterogeneous, urbanized landscapes. METHODS: We investigated differences in infection risk (i.e., probability of infection) within urbanized landscapes using the coyote (Canis latrans) and mosquito-borne nematode, Dirofilaria immitis (the causative agent for canine heartworm), as a case study. We focused on a coyote population in Chicago for which extensive behavioral and heartworm infection data has been collected between 2001 and 2016. Our objectives were to: (i) determine how onset and duration of the heartworm transmission season varied over the 16-year period and across the urban-suburban gradient; and (ii) investigate how heartworm infection risk in coyotes varied over the years, across the urban-suburban gradient, by coyote characteristics (e.g., age, sex, resident status), and coyote use of the urbanized landscape (e.g., use of urban areas, mosquito habitats). RESULTS: While onset of the heartworm transmission season differed neither by year nor across the urban-suburban gradient, it was longer closer to the core of Chicago. Of the 315 coyotes sampled, 31.1% were infected with D. immitis. Older coyotes and coyotes sampled in later years (i.e., 2012-2016) were more likely to have heartworm. While coyote location in the urban-suburban gradient was not a significant predictor of infection, the proportion of urban land in coyote home ranges was. Importantly, the size and direction of this association varied by age class. For adults and pups, infection risk declined with urbanization, whereas for subadults it increased. Further, models had a higher predictive power when focusing on resident coyotes (and excluding transient coyotes). The proportion of mosquito habitat in coyote home ranges was not a significant predictor of infection. CONCLUSIONS: Our findings suggest that urbanization may affect host exposure to vectors of D. immitis, that risk of infection can vary within urbanized landscapes, and that urbanization-wildlife infection associations may only be detected for animals with certain characteristics (e.g., age class and resident status).

Dirofilaria immitis and Dirofilaria repens in mosquitoes from Corsica Island, France.

BACKGROUND: Dirofilaria immitis and Dirofilaria repens are the main causative agents of heartworm disease and subcutaneous dirofilariasis in domestic and wild canids, respectively. Both pathogens have zoonotic potential and are transmitted by mosquitoes. The present study aimed to determine the transmission period, prevalence and diversity of Dirofilaria spp. vectors from endemic areas of Corsica (France). METHODS: A monthly point data model based on average temperature recorded by four meteorological stations during 2017 was used to calculate the Dirofilaria transmission period. From June to September 2017, female mosquitoes (n = 1802) were captured using Biogents® Sentinel 2 traps lured with carbon dioxide and BG-Lure™ or octanol. Mosquitoes were identified to species level, pooled accordingly, and screened using multiplex real-time qPCR to detect D. immitis and D. repens. RESULTS: The monthly point data model showed the possible transmission of Dirofilaria spp. from the third week in May to the last week in October in the studied area. Mosquitoes were identified as Ochlerotatus caspius (n = 1432), Aedes albopictus (n = 199), Culex pipiens sensu lato (n = 165) and Aedes vexans (n = 6) and were grouped into 109 pools (from 1 to 27 specimens, mean 11.4 ± 0.7), of which 16 scored positive for Dirofilaria spp. (i.e., n = 13; estimated infection rate [EIR] = 1.1% for D. immitis and n = 3; EIR = 0.2% for D. repens). Specifically, 6 (i.e., EIR = 3.8%) of 15 pools of Ae. albopictus were positive for D. immitis, 2 of 14 of Cx. pipiens s.l. were positive for D. immitis and D. repens, respectively, and 8 of 77 pools of Oc. caspius were positive for D. immitis (i.e., n = 6; EIR = 0.4%) and D. repens (i.e., 2; EIR = 0.1%). The highest mosquito infection rate was recorded in July (EIR = 2.5%), then in June (EIR = 1.3%) and September (EIR = 0.6%). CONCLUSIONS: The data suggest that both Dirofilaria species are endemic and occur possibly in sympatry in the studied area in Corsica, highlighting the need to implement preventive chemoprophylaxis and vector control strategies to reduce the risk of these filarioids in dog and human populations.

Efficacy of afoxolaner (NexGard®) in preventing the transmission of Leishmania infantum and Dirofilaria immitis to sheltered dogs in a highly endemic area.

BACKGROUND: Leishmania infantum and Dirofilaria immitis are among the most important canine vector-borne pathogens (CVBPs) of zoonotic concern in Europe. In endemic areas for both of these CVBPs, the use of systemic ectoparasiticides, such as afoxolaner (NexGard®; Boehringer Ingelheim Animal Health), may have the potential for controlling these infections. The aim of this study was to assess, for the first time, the insecticidal efficacy of NexGard® in decreasing the transmission of D. immitis and L. infantum to sheltered dogs living in a hyperendemic area, compared to the year before treatment, as well as its impact on the abundance of mosquito and sand fly populations. METHODS: All dogs (n = 179) enrolled in the study were divided into two groups based on their infection status at enrollment: a non-infected group (G1) and an infected group (G2; infected with D. immitis, L. infantum or both). The study was conducted from March 2020 to March 2021. In order to exclude all animals infected with L. infantum and D. immitis before March 2020 (sampling time: T0), dogs in G1 were sampled in June (T1; i.e. T0 + 90 days) and in October 2020 (T2; i.e. T0 + 210 days). From March to September 2020, all animals (G1 and G2) were weighed and treated monthly with NexGard®. Animals in G1 were tested for the last time in March 2021 (T3; i.e. T0 + 330 days) for assessing post-treatment incidence rate of infection and prevention efficacy. RESULTS: The post-treatment incidence of D. immitis was 3.7% (1/27; 95% confidence interval [CI]: 0.2-18.1) and that of L. infantum was 3.6% (3/83; 95% CI: 1.0-10.1). Considering the annual incidence in 2019 and 2020, the protective efficacy against D. immitis and L. infantum infections was 94.2 and 64%, respectively. Of the female mosquitoes collected (n = 146), only one pool out of 50 tested positive for D. immitis DNA, whereas out of 1252 female Sergentomya minuta specimens collected, only four tested positive for L. infantum (0.3%). CONCLUSIONS: Afoxolaner is efficacious in decreasing the rate of transmission of both D. immitis and L. infantum; however, comparison of the pre- and post-treatment period demonstrated that there was a significant difference only in the seasonal incidences of D. immitis infection. Preventive measures are recommended throughout the year in endemic areas to reduce the risk of pathogen transmission to animals and humans.

Human dirofilariosis in Austria: the past, the present, the future.

BACKGROUND: Dirofilariosis is a vector-borne parasitosis caused by filarial nematodes of the genus Dirofilaria. In humans, who represent accidental hosts, dirofilariosis is mostly caused by Dirofilaria repens and Dirofilaria immitis. In Austria, the first reported case occurred in 1978. Since then, several (case) reports have been published. METHODS: A systematic and retrospective review of collected published cases and new, unpublished confirmed cases of human dirofilariosis occurring in Austria was performed. A nematode was extracted from the eyelid of a previously unreported case and subsequently characterized histologically and using molecular biology techniques. RESULTS: Data on a total of 39 cases of human dirofilariosis in Austria occurring between 1978 and 2020 are summarized. Over the past four decades the incidence has markedly increased, in particular after 1998. Of the 39 patients, men and women were equally affected, and the mean age was 47.1 years. The area most frequently affected was the head (38.5% of cases). Confined ocular involvement was observed in 23.1% of cases, and nematodes were isolated from the neck/trunk, extremities and the genito-inguinal area in 25.6, 15.4 and 15.4% of patients, respectively. Microfilariae were detected in two cases. Of the 39 patients, only 73.9% tested positive for anti-filarial antibodies and 56.3% for eosinophilia, despite successful isolation of a nematode; consequently, these measures did not represent reliable markers for dirofilariosis. Most patients had a travel history to countries endemic for Dirofilaria species. One patient who had not traveled abroad represented the only autochthonous case recorded to date. Dirofilaria repens was the predominant species, identified in 89.7% of cases. In the newly reported case of subcutaneous dirofilariosis, a live non-gravid Dirofilaria repens adult female of 12 cm length was isolated from the eyelid of the patient, and a video of the extraction is provided. CONCLUSIONS: The incidence of human dirofilariosis cases has increased strikingly over the last four decades in Austria. More cases can be expected in the foreseeable future due to changes in human behavior and (travel) activities as well as climate changes and the associated alterations in the availability of the natural reservoir, the vectors and the intrinsic characteristics of the parasite.

Occurrence of the Mosquito Aedes triseriatus (Diptera: Culicidae) Beyond Its Most Northwestern Range Limits in Manitoba, Canada.

Native to the Eastern United States and Eastern Canada, Aedes triseriatus (eastern tree hole mosquito) is an important vector of La Crosse virus and dog heartworm. Although its range has been well characterized in the United States, few studies have surveyed its distribution within Canada. In this study, mosquitoes were collected from a variety of urban and rural communities throughout Manitoba, Canada between the years of 2018 and 2020. Aedes triseriatus was identified and confirmed molecularly to be present in 13 communities. This includes localities that expand the species known distribution to new northern and western areas, and suggests that past surveillance efforts have not been comprehensive or environmental factors have caused this mosquito species to be present in areas in which it was not found previously. As Canada is showing signs of a changing climate, this may be driving the broader occurrence of Ae. triseriatus.

A novel assay to isolate and quantify third-stage Dirofilaria immitis and Brugia malayi larvae emerging from individual Aedes aegypti.

BACKGROUND: Mosquitoes transmit filarial nematodes to both human and animal hosts, with worldwide health and economic consequences. Transmission to a vertebrate host requires that ingested microfilariae develop into infective third-stage larvae capable of emerging from the mosquito proboscis onto the skin of the host during blood-feeding. Determining the number of microfilariae that successfully develop to infective third-stage larvae in the mosquito host is key to understanding parasite transmission potential and to developing new strategies to block these worms in their vector. METHODS: We developed a novel method to efficiently assess the number of infective third-stage filarial larvae that emerge from experimentally infected mosquitoes. Following infection, individual mosquitoes were placed in wells of a multi-well culture plate and warmed to 37 °C to stimulate parasite emergence. Aedes aegypti infected with Dirofilaria immitis were used to determine infection conditions and assay timing. The assay was also tested with Brugia malayi-infected Ae. aegypti. RESULTS: Approximately 30% of Ae. aegypti infected with D. immitis and 50% of those infected with B. malayi produced emerging third-stage larvae. Once D. immitis third-stage larvae emerged at 13 days post infection, the proportion of mosquitoes producing them and the number produced per mosquito remained stable until at least day 21. The prevalence and intensity of emerging third-stage B. malayi were similar on days 12-14 post infection. Increased uptake of D. immitis microfilariae increased the fitness cost to the mosquito but did not increase the number of emerging third-stage larvae. CONCLUSIONS: We provide a new assay with an associated set of infection conditions that will facilitate assessment of the filarial transmission potential of mosquito vectors and promote preparation of uniformly infectious third-stage larvae for functional assays. The ability to quantify infection outcome will facilitate analyses of molecular interactions between vectors and filariae, ultimately allowing for the establishment of novel methods to block disease transmission.

Collection and DNA Detection of Dirofilaria immitis (Rhabditida Onchocercidae), Using a Novel Primer Set, in Wild-Caught Mosquitoes From Gainesville, FL.

Dirofilaria immitis, the causative agent of dog heartworm disease, is an important cause of canine morbidity and mortality, expensive to treat, and severe infections are often fatal. Much is known about the pathogen in the canine host, yet little is known on the basic ecology of the nematode in the mosquito vector. Thus, to evaluate the effectiveness of collection techniques on ability to capture dog heartworm-infected mosquitoes (Diptera Culicidae), we conducted a field study spanning 111 wk. Four methods were used: two aspirators types, sweep netting, and a CDC trap. All sites had canines present in either residential yards (n = 4) or dog kennel facilities (n = 3). Collected mosquitoes were sorted by site, trap, species, and date, then pooled into groups of up to 25 individuals. Mosquito head and thorax pools were extracted for DNA, that was screened using currently available protocols. These protocols were found unreliable; thus, we developed a novel qPCR primer and probe set. Using this method, the original samples were re-assayed and provided 494 positive pools. Approximately 10% of positive samples were confirmed by Sanger sequencing. Twenty-two mosquito species tested positive for dog heartworm DNA, including a new association with Wyeomyia mitchellii (Theobald). Although Aedes atlanticus (Dyar and Knab), Anopheles crucians Wiedemann, and Culiseta melanura (Coquillett) composed nearly 36% of the total collection, these species represented 42% of the qPCR positive pools. Infection rates within commonly collected mosquitoes ranged up to 2.5%, with more rarely collected species ranging up to 14%. The CDC trap was the most effective collection method at trapping infected mosquitoes.

Potential Mosquito Vectors of Dirofilaria immitis and Dirofilaira repens (Spirurida: Onchocercidae) in Aras Valley, Turkey.

Dirofilaria immitis (Leidy, 1856) and Dirofilaria repens (Railliet & Henry, 1911) are mosquito-borne filarial nematodes that primarily affect dogs, causing heartworm disease and subcutaneous dirofilariosis. The canine heartworm is reported in different provinces in Turkey. However, studies about the transmitting mosquito species are limited. Hence, this study aimed to investigate potential vectors of D. immitis and D. repens in Aras Valley, Turkey. In total, 17,995 female mosquitoes were collected from eight villages during three mosquito seasons (2012-2014) in Aras Valley, located in north-eastern Turkey. A total of 1,054 DNA pools (527 abdomen and 527 head-thorax) were tested with Dirofilaria primers by multiplex-polymerase chain reaction (PCR). Aedes caspius was the most abundant species in collection sites with 90%; this was followed by Culex theileri Theobald, 1903 (Diptera: Culicidae) (7.31%), Anopheles maculipennis Meigen 1818 (Diptera: Culicidae) (1.28%), Culex pipiens Linnaeus, 1758 (Diptera: Culicidae) (0.43%), (Anopheles) hyrcanus (Pallas, 1771) (Diptera: Culicidae) (0.37%), Aedes vexans (Meigen, 1830) (Diptera: Culicidae) (0.25%), and Culiseta annulata Schrank, 1776 (Diptera:Culicidae) (0.02%). Dirofilaria immitis and D. repens were detected in mosquito pools from five villages. The total Dirofilaria spp. estimated infection rate was 1.33%. The highest estimated infection rate was found in Ae. vexans (6.66%) and the lowest was in Ae. caspius (1.26%). The results show that An. maculipennis sl, Ae. caspius, Ae. vexans, Cx. theileri and Cx. pipiens are potential vectors of D. immitis and D. repens with DNA in head-thorax pools; An. hyrcanus is also a likely vector, but Dirofilaria DNA was found only in abdomen pools for the study area. This study revealed new potential vector species for D. immitis. Mosquitoes with natural infections of D. repens were reported for the first time in Turkey.

Dirofilaria immitis proteins recognized by antibodies from individuals living with microfilaremic dogs.

INTRODUCTION: Dirofilaria immitis is a nematode that affects human health in several countries of the world. This study was conducted to examine whether serum samples from the owners of microfilaremic dogs present immunoreactivity to parasite proteins. METHODOLOGY: Eight serum samples from the owners of microfilaremic dogs were examined. Total proteins were extracted from adult worms and 12% SDS-PAGE was performed. The gel was electroblotted to a nitrocellulose membrane, and a Western blot (WB) was performed. Reactive bands of 22, 33, 39, 49, and 63 kDa in WB were excised from the gel and analyzed by mass spectrometry (MS). RESULTS: The MS results showed the presence of 10 different proteins of D. immitis recognized by the human serum samples. CONCLUSIONS: These results indicate that in endemic areas of D. immitis, owners of infected dogs recognize specific proteins of the parasite, suggesting a possible infection.

Molecular detection of Dirofilaria spp. and host blood-meal identification in the Simulium turgaicum complex (Diptera: Simuliidae) in the Aras River Basin, northwestern Iran.

BACKGROUND: Blackflies (Diptera: Simuliidae) are known as effective vectors of human and animal pathogens, worldwide. We have already indicated that some individuals in the Simulium turgaicum complex are annoying pests of humans and livestock in the Aras River Basin, Iran. However, there is no evidence of host preference and their possible vectorial role in the region. This study was conducted to capture the S. turgaicum (s.l.), to identify their host blood-meals, and to examine their potential involvement in the circulation of zoonotic microfilariae in the study areas. METHODS: Adult blackflies of the S. turgaicum complex were bimonthly trapped with insect net in four ecotopes (humans/animals outdoors, irrigation canals, lands along the river, as well as rice and alfalfa farms) of ten villages (Gholibaiglou, Gungormaz, Hamrahlou, Hasanlou, Khetay, Khomarlou, Larijan, Mohammad Salehlou, Parvizkhanlou and Qarloujeh) of the Aras River Basin. A highly sensitive and specific nested PCR assay was used for detection of filarial nematodes in S. turgaicum (s.l.), using nuclear 18S rDNA-ITS1 markers. The sources of blood meals of engorged specimens were determined using multiplex and conventional cytb PCR assays. RESULTS: A total of 2754 females of S. turgaicum (s.l.) were collected. The DNA of filarial parasites was detected in 6 (0.62%) of 960 randomly examined individuals. Sequence analysis of 420 base pairs of 18S rDNA-ITS1 genes identified Dirofilaria spp. including 5 D. immitis and 1 D. repens. Importantly, all filarial positive specimens have been captured from humans and animals outdoors. Cytb-PCR assays showed that in all ecotypes studied, members of the S. turgaicum complex had preferably fed on humans, dogs, bovids, and birds, respectively. CONCLUSIONS: To the best of our knowledge, this is the first report of D. immitis/D. repens detection in blackflies. Results showed that S. turgaicum (s.l.) was the most abundant (97%) and anthropophilic (45%) blackfly in all studied ecotypes/villages and that DNA of Dirofilaria spp. was detected in the flies taken from six villages. Dirofilariasis is a common zoonosis between humans and carnivores, with mosquitoes (Culicidae) as the principal vectors. Further investigations are needed to demonstrate that blackflies are actual vectors of Dirofilaria in the studied region.

Human seroprevalence data indicate other factors than climatic conditions influencing dirofilariosis transmission in the Russian Federation.

The species of the genus Dirofilaria are filarial parasites causing zoonotic infections in humans with an increasing incidence in temperate and tropical areas of the world. Due to its classification as a vector-borne disease, the most important factors influencing dirofilariosis transmission are those related to climate, such as temperature and humidity. However, other factors linked with human behaviour can influence the distribution of the parasite. Although the Russian Federation could be considered as a non-suitable area for Dirofilaria spp. transmission due to its climatic conditions, one third of the human cases of dirofilariosis have been declared in this country. Here, seroepidemiological data on human dirofilariosis for five different regions distributed throughout the Russian Federation (Rostov, Moscow, Ekaterinburg, Yakutia and Khabarovsk) were obtained. A total of 940 serum samples from totally random donors living in these areas were analysed by enzyme-linked immunosorbent assay for the detection of anti-Dirofilaria immitis immunoglobulin G antibodies. Similar seroprevalence data ranging from 3.41% in Yakutia to 6.95% in Khabarovsk, with no significant correlation with climatic data of yearly average temperature and rainfall from these regions were found. These results suggest that other factors probably related to human behaviour, and not only climatic conditions, might be facilitating the spread of human dirofilariosis in these areas.

Laboratory colonization by Dirofilaria immitis alters the microbiome of female Aedes aegypti mosquitoes.

BACKGROUND: The ability of blood-feeding arthropods to successfully acquire and transmit pathogens of medical and veterinary importance has been shown to be interfered with, or enhanced by, the arthropod's native microbiome. Mosquitoes transmit viruses, protozoan and filarial nematodes, the majority of which contribute to the 17% of infectious disease cases worldwide. Dirofilaria immitis, a mosquito-transmitted filarial nematodes of dogs and cats, is vectored by several mosquito species including Aedes aegypti. METHODS: In this study, we investigated the impact of D. immitis colonization on the microbiome of laboratory reared female Ae. aegypti. Metagenomic analysis of the V3-V4 variable region of the microbial 16S RNA gene was used for identification of the microbial differences down to species level. RESULTS: We generated a total of 1068 OTUs representing 16 phyla, 181 genera and 271 bacterial species. Overall, in order of abundance, Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes were the most represented phylum with D. immitis-infected mosquitoes having more of Proteobacteria (71%) than uninfected mosquitoes (56.9%). An interesting finding in this study is the detection of Klebsiella oxytoca in relatively similar abundance in infected and uninfected mosquitoes, suggesting a possible endosymbiotic relationship, and has been previously shown to indirectly compete for nutrients with fungi on domestic housefly eggs and larvae. While D. immitis colonization has no effect on the overall species richness, we identified significant differences in the composition of selected bacterial genera and phyla between the two groups. We also reported distinct compositional and phylogenetic differences in the individual bacterial species when commonly identified bacteria were compared. CONCLUSIONS: To the best of our knowledge, this is the first study to understand the impact of a filarial infection on the microbiome of its mosquito vector. Further studies are required to identify bacteria species that could play an important role in the mosquito biology. While the microbiome composition of Ae. aegypti mosquito have been previously reported, our study shows that in an effort to establish itself, a filarial nematode modifies and alters the overall microbial diversity within its mosquito host.

Overview on Dirofilaria immitis in the Americas, with notes on other filarial worms infecting dogs.

Canine dirofilariosis in the Americas is primarily caused by Dirofilaria immitis, a mosquito-borne filarial worm infecting dogs, which may also infect and cause disease in other mammalian hosts, including humans. Morphological and molecular evidence gathered in the past decades suggest that other Dirofilaria spp. may infect dogs in the American continent, though the actual taxonomic identity of them still needs to be elucidated. In addition, filarial worms belonging to distinct genera have also been reported in dogs in this part of the world, including Acanthocheilonema reconditum, Cercopithifilaria bainae, and Onchocerca lupi. Among these, O. lupi is a species of major clinical significance, which has been reported not only in dogs, but also in cats and humans in North America. The present article provides a current overview on canine dirofilariosis in the Americas, with notes on other filarial worms infecting dogs. It also provides some insights into outstanding research questions that should be responded to fill some of the several knowledge gaps related to this group of parasites in this continent.

Dirofilaria hongkongensis infection presenting as recurrent shoulder mass.

In 2012, a novel canine Dirofilaria species, D. hongkongensis was identified in Hong Kong that caused human diseases and subsequently reported in an Austrian traveller returning from the Indian subcontinent. Here we present a case of human infection by D. hongkongensis manifested as recurrent shoulder mass. Diagnosis was achieved by cox1 gene sequencing of the excised specimen. The case illustrated that parasitic infection represents an important differential diagnosis for musculoskeletal lesions.

Current trends in canine dirofilariosis in Austria-do we face a pre-endemic status?

A retrospective study based on cases of canine dirofilariosis presented to the University of Veterinary Medicine, Vienna or diagnosed by private practitioners throughout Austria, from 1998 to 2018 was conducted to investigate the long-term development and current state of canine dirofilarial infections in Austria. Included in this study were 146 dogs which were tested positive for D. immitis and/or D. repens. The most commonly used diagnostic methods and the probable geographical origins of the infections were evaluated and the treatment protocols applied were compared with each other and with the literature. The results show that most infections were found due to screening for common travel infections using antigen-ELISA or PCR-testing, or by the incidental finding of microfilariae. Remarkably, only 24.3% of all cases presented showed clinical signs indicating canine dirofilariosis. Regarding the origin and travel history of the dogs, thirteen different countries could be identified. The three treatment protocols used showed a similar outcome after 8 months of treatment and minor side effects, which is consistent with the literature. An alarming increase in reported infections with both D. immitis and D. repens in Austria was noted since 2014. The number of documented cases had almost tripled by 2018, raising severe concerns about the threat of it becoming endemic in Austria. Therefore, the existing recommendations in current guidelines regarding canine dirofilariosis should be widely publicised and more strictly enforced. Prophylactic measures for dogs travelling abroad and diagnostic and therapeutic strategies for dogs imported from endemic countries should be obligatorily established throughout Europe, to reduce the risk of further spread of canine filarial infections to non-endemic regions.

Mosquito diversity and dog heartworm prevalence in suburban areas.

BACKGROUND: Urbanization is occurring rapidly on a global scale and is altering mosquito communities, creating assemblages that are characteristically less diverse. Despite high rates of urbanization and ample examples of vector-borne diseases transmitted by multiple species, the effects of urbanization-driven mosquito diversity losses on disease transmission has not been well explored. We investigated this question using the dog heartworm, a filarial parasite vectored by numerous mosquito species. METHODS: We trapped host-seeking mosquitoes in undeveloped areas and neighborhoods of different ages in Wake County, North Carolina, USA, analyzing captured mosquitoes for heartworm DNA. We compared within-mosquito heartworm infection across land-use types by Kruskal-Wallis and likelihood ratio tests. Using zip code level data acquired from dogs in a local shelter, we performed linear regressions of within-host heartworm prevalence by within-mosquito heartworm prevalence as well as by three mosquito diversity measures. We also determined the best predictor of host-level prevalence among models including within-mosquito infection, mosquito diversity and abundance, and socioeconomic status as variables. RESULTS: Suburban areas had lower within-mosquito heartworm prevalence and lower likelihood of heartworm-positive mosquitoes than did undeveloped field sites, although no differences were seen between suburban and undeveloped wooded sites. No relationships were noted between within-mosquito and within-host heartworm prevalence. However, mosquito diversity metrics were positively correlated with host heartworm prevalence. Model selection revealed within-host prevalence was best predicted by a positive relationship with mosquito Shannon-Wiener diversity and a negative relationship with household income. CONCLUSIONS: Our results demonstrate that decreases in mosquito diversity due to urbanization alter vector-borne disease risk. With regard to dog heartworm disease, this loss of mosquito diversity is associated with decreased heartworm prevalence within both the vector and the host. Although the response is likely different for diseases transmitted by one or few species, mosquito diversity losses leading to decreased transmission could be generalizable to other pathogens with multiple vectors. This study contributes to better understanding of the effects of urbanization and the role of vector diversity in multi-vectored pathosystems.

Seroprevalence of viral and vector-borne bacterial pathogens in domestic dogs (Canis familiaris) in northern Botswana.

BACKGROUND: Domestic dogs (Canis familiaris) have the potential to act as disease reservoirs for wildlife and are important sentinels for common circulating pathogens. Therefore, the infectious disease seroprevalence among domestic dogs in northern Botswana may be indicative of pathogen exposure of various wildlife species. The objective of this study was to assess the seroprevalence of Ehrlichia spp., Borrelia burgdorferi, Anaplasma spp., Dirofilaria immitis, canine adenovirus, canine parvovirus, and canine distemper virus in domestic dogs as proxies of disease prevalence in the local wildlife in the Okavango Delta region of Botswana. Statistical analysis assessed crude and factor-specific seroprevalence proportions in relation to age, sex, and geographical location as predictors of seropositivity. Logistic regression was used to identify adjusted predictors of seropositivity for each of the pathogens of interest. RESULTS: Samples from 233 dogs in a total of seven locations in Maun, Botswana, and surrounding villages were collected and serologically analyzed. No dogs were seropositive for B. burgdorferi, while low seroprevalence proportions were observed for Anaplasma spp. (2.2%) and D. immitis (0.9%). Higher seroprevalence proportions were observed for the tick-borne pathogen Ehrlichia spp. (21.0%), and 19.7% were seropositive for canine adenovirus (hepatitis). The highest seroprevalence proportions were for canine parvovirus (70.0%) and canine distemper virus (44.8%). The predictors of seropositivity revealed that adults were more likely to be seropositive for canine adenovirus, canine distemper virus, and canine parvovirus than juveniles, and location was a risk factor for canine adenovirus, canine distemper virus, canine parvovirus, and Ehrlichia spp. CONCLUSIONS: Results indicate that increasing tick control and vaccination campaigns for domestic dogs may improve the health of domestic animals, and potentially wildlife and humans in the Okavango Delta since viral and vector-borne bacterial pathogens can be transmitted between them.

Comparative Vector Efficiency of Two Prevalent Mosquito Species for Dog Heartworm in North Carolina.

The dog heartworm, Dirofilaria immitis (Leidy) (Spirurida: Onchocercidae), is a devastating parasite of domestic and wild canines vectored by a multitude of mosquito species. Although many species are implicated as vectors, not all contribute equally to disease transmission, with demonstrated variation in vector efficiency between and within species. We investigated the vector efficiency of mosquitoes derived from wild-caught North Carolina populations of two known heartworm vectors: a native species, Aedes triseriatus (Say) (Diptera: Culicidae), and an invasive species, Aedes albopictus (Skuse). We compared the parasite developmental times within the mosquito, mosquito longevity and fecundity, and the vector efficiency index between the two species. We found that the tested composite North Carolina population of Ae. triseriatus was an efficient vector of D. immitis under laboratory conditions, whereas the local composite population of Ae. albopictus was a competent but relatively poor vector. Compared with Ae. triseriatus, Ae. albopictus showed a longer time for parasite development, lower infection rates, and lower vector efficiency. Additionally, Ae. albopictus was the sole species to exhibit significant parasite-induced mortality. These results are in contrast to prior studies of populations of Ae. albopictus from locations outside of North Carolina, which have implicated the species as a highly competent heartworm vector. The variation seen for different strains of the same species emphasizes the heritable nature of D. immitis vector competence and highlights the need for local infection studies for accurate transmission risk assessment in a particular locale.

Gonotrophic discordance in Culex quinquefasciatus (Diptera: Culicidae) in the city of São Paulo, Brazil

Abstract INTRODUCTION: This study aimed to assess the occurrence of gonotrophic discordance in females of Culex quinquefasciatus in São Paulo, Brazil. METHODS: Resting females were collected monthly for 8 months. Females of Cx. quinquefasciatus were identified, and their midgut and ovaries were dissected. RESULTS: Two hundred females were dissected, out of which, 27.5% were nulliparous and 57% were parous. Most females had no blood in the midgut, but gonotrophic discordance was found in 21% females. CONCLUSIONS: Females of Cx. quinquefasciatus showed a high parity rate and gonotrophic discordance, which could favor the vector capacity of this species.