PREVALENCE OF EHRLICHIA AND ANAPLASMA SPP. IN TICKS COLLECTED FROM CATTLE AND DEER IN ARKANSAS, USA.

Bovine anaplasmosis, caused by Anaplasma marginale, is widespread in cattle in the southeast United States. The pathogen is biologically transmitted by Dermacentor spp. ticks, and mechanically transmitted by biting flies and via fomites. Despite high reported regional seroprevalence, Dermacentor spp. are rare on cattle in the southeast. To identify other putative An. marginale vectors, and to characterize cattle exposure to other tick-borne pathogens, we collected ticks from Arkansas cattle herds in 2020-2022. Recognizing that deer are important hosts for some of the same tick species that parasitize cattle, we also collected ticks from hunter-killed deer in the fall and winter of 2021. Ticks were screened for bacteria in the family Anaplasmataceae using qPCR. Positive samples were further amplified using a PCR assay targeting the groEL gene, and the resulting amplicons were sequenced for identification. A total of 3,794 ticks were collected, the majority of which were Amblyomma americanum. Amblyomma americanum was the most common species on cattle, and Ixodes scapularis was most common on deer. No ticks were positive for An. marginale, though Anaplasma phagocytophilum was detected in deer-collected I. scapularis, as well as in a single engorged Am. americanum from cattle. Amblyomma americanum from cattle were infected with Ehrlichia ewingii, Ehrilichia chaffeensis, and Panola Mountain Ehrlichia. Cattle in Arkansas are exposed to several ehrlichial pathogens and may also be exposed to An. phagocytophilum. The importance of these pathogens, particularly Panola Mountain Ehrlichia, in causing cattle disease in Arkansas deserves further study, as does the importance of mechanical transmission of An. marginale in bovine anaplasmosis epidemiology.

Utilization of a zoo for mosquito (Diptera: Culicidae) diversity analysis, arboviral surveillance, and blood feeding patterns.

Zoos provide a unique opportunity to study mosquito feeding ecology as they represent areas where exotic animals, free-roaming native animals, humans, and mosquito habitats overlap. Therefore, these locations are a concern for arbovirus transmission to both valuable zoo animals and human visitors. We sampled mosquitoes in and around The Nashville Zoo at Grassmere in Tennessee, USA, over 4 months in 2020 using 4 mosquito trap methods and 12 sampling locations. Mosquitoes were identified to species, Culex mosquitoes were analyzed for arboviruses, and all engorged mosquitoes were preserved for host usage analysis. We captured over 9,000 mosquitoes representing 27 different species, including a new species record for Davidson County, TN (Culex nigripalpus Theobald). Minimum infection rates for West Nile virus (WNV) (Flaviviridae: Flavivirus), St. Louis encephalitis virus (Flaviviridae: Flavivirus), and Flanders virus (Hapavirus: Rhabdoviridae) were 0.79, 0, and 4.17, respectively. The collection of 100 engorged mosquitoes was dominated by Culex pipiens pipiens Linnaeus (38%), Culex erraticus Dyar and Knab (23%), and Culex pipiens pipiens-Culex pipiens quinquefasciatus hybrids (10%). Host DNA from 84 engorged mosquitoes was successfully matched to a variety of host species (n = 23), with just 8 species belonging to the zoo. Wild birds were the most frequently fed upon host, in particular northern cardinals (Cardinalis cardinalis L. Passeriformes: Cardinalidae), which are competent WNV reservoirs. Taken together, our results demonstrate the utility of zoos as sentinels for emerging pathogens, for studying wildlife and human risk of zoonotic diseases, and for assessing vector diversity.

Co-occurrence of Culicoides guttipennis (Coquillett) with tree hole mosquito species, including Aedes albopictus Skuse, in container habitats in northwest Arkansas, U.S.A.

Natural and artificial water-filled containers serve as development sites for several larval Dipterans, including medically important mosquito species and Culicoides biting midges. Containers are discrete habitats with limited carrying capacity and high levels of both intra- and interspecific competition. While the outcomes of the interactions between mosquito species, particularly native and introduced Aedes, have been well described, competition between mosquitoes and other taxa, including Culicoides, is largely unstudied. To determine the extent of shared resource use between container-inhabiting mosquito and biting midge species, we surveyed water-filled natural and artificial container habitats in Washington County, AR. Larvae were collected from containers in the field and reared in the laboratory until the adult stage, where they were identified to species. Culicoides guttipennis, the only Culicoides species identified, co-occurred with four mosquito species, including the invasive Aedes albopictus. Culicoides larvae were more common in natural than artificial containers. Natural container samples from which Ae. albopictus emerged were significantly less likely to harbor Culicoides larvae than samples where that mosquito species was absent, suggesting the possibility that Ae. albopictus competes either directly or indirectly with other native taxa beyond congeners. Further research is needed on the nature of the interactions between Ae. albopictus and native Culicoides spp.

Host Bloodmeal Identification in Cave-Dwelling Ornithodoros turicata Dugès (Ixodida: Argasidae), Texas, USA.

Tick-host bloodmeal associations are important factors when characterizing risks of associated pathogen transmission and applying appropriate management strategies. Despite their biological importance, comparatively little is known about soft tick (Argasidae) host associations in the United States compared to hard ticks (Ixodidae). In this study, we evaluated a PCR and direct Sanger sequencing method for identifying the bloodmeal hosts of soft ticks. We collected 381 cave-associated Ornithodoros turicata near San Antonio, Texas, USA, and also utilized eight colony-reared specimens fed artificially on known host blood sources over 1.5 years ago. We correctly identified the vertebrate host bloodmeals of two colony-reared ticks (chicken and pig) up to 1,105 days post-feeding, and identified bloodmeal hosts from 19 out of 168 field-collected soft ticks, including raccoon (78.9%), black vulture (10.5%), Texas black rattlesnake (5.3%), and human (5.3%). Our results confirm the retention of vertebrate blood DNA in soft ticks and advance the knowledge of argasid host associations in cave-dwelling O. turicata.

Cell fusing agent virus (Flavivirus) infection in Aedes aegypti in Texas: seasonality, comparison by trap type, and individual viral loads.

South Texas has experienced local transmission of Zika virus and of other mosquito-borne viruses such as chikungunya virus and dengue virus in the last decades. Using a mosquito surveillance program in the Lower Rio Grande Valley (LRGV) and San Antonio, TX, from 2016 to 2018, we detected the presence of an insect-specific virus, cell fusing agent virus (CFAV), in the Aedes aegypti mosquito population. We tested 6,326 females and 1,249 males from the LRGV and 659 females from San Antonio for CFAV by RT-PCR using specific primers. Infection rates varied from 0 to 261 per 1,000 mosquitoes in the LRGV and 115 to 208 per 1,000 in San Antonio depending on the month of collection. Infection rates per 1,000 individuals appeared higher in females collected from BG Sentinel 2 traps compared to Autocidal Gravid Ovitraps, but the ratio of the percentage of infected pools did not differ by trap type. The natural viral load in individual males ranged from 1.25 x 102 to 5.50 x 106 RNA copies and in unfed females from 5.42 x 103 to 8.70 x 106 RNA copies. Gravid females were found to harbor fewer viral particles than males and unfed females.