ZOOS AS EXPERIMENT ENVIRONMENTS: BIOLOGY OF LARVAL AND ADULT MOSQUITOES (DIPTERA: CULICIDAE)

Zoos are a unique environment where humans and animals are in close daily contact, potential mosquito habitats exist, exotic plants and animals are introduced regularly, and wild animals roam. Studies of mosquito behaviors in zoos will lead to a better understanding, both within and outside zoos, of disease transmission routes and mosquito biology. To investigate whether the unique assemblage of habitats in zoos affects mosquito behavior, I sampled larvae and adults in the Greenville Zoo and the Riverbanks Zoo, South Carolina, USA, from March 2008 to January 2011. The objectives of my study were to investigate mosquito oviposition behavior, blood-host usage, and transmission of the causative agent of dog heartworm (Dirofilaria immitis); document the structure of the mosquito pyloric armature; and provide zoos with suggestions for mosquito control. My results underscore the medical and veterinary importance of studying mosquito blood feeding ecology in zoos, and the experimental utility of zoos for studying mosquito behavior. A total of 1,630 larvae and 4,349 adults representing 16 species was collected and identified. The most common species were Aedes albopictus, Ae. triseriatus, Culex erraticus, Cx. restuans, and Cx. pipiens complex. Principal components and multiple logistic regression analyses showed that across both zoos the overall larval mosquito presence (regardless of species) was predicted by ambient and site temperature, precipitation, dissolved oxygen, presence of natural habitats, and absence of aquatic vegetation. Pairwise species associations indicated significant habitat-based relationships between larvae of Ae. albopictus and Ae. triseriatus, and Cx. pipiens complex and Cx. restuans. Recommendations to zoo personnel, regarding larval mosquito habitat management, were to reduce or eliminate artificial containers and shade sources greater than or equal to 2 m above standing water, use mosquito larvicides when source reduction is not possible, and receive training in recognizing and mitigating larval mosquito habitats. Mosquitoes fed on captive animals, humans, and wild animals, and took mixed bloodmeals. Blood hosts included 1 amphibian species, 16 bird species, 10 mammal species (including humans), and 2 reptile species. Minimum flight distances (dispersal) from host locations ranged from 15.5 m to 327.0 m, with a mean of 94.1 m ± 13.4 m. No mosquitoes tested (n = 45) were positive for D. immitis. The pyloric spines of Ae. albopictus, Ae. j. japonicus, Ae. triseriatus, An. punctipennis, Cx. pipiens complex, Cx. restuans, Or. signifera, and Tx. rutilus were photographed and measured. Differences exist in qualitative and quantitative spine structure, with Aedes spp. forming one general group, Culex spp. another, and An. punctipennis and Or. signifera a third. The one specimen of Toxorhynchites rutilus examined was most like Culex spp. mosquitoes. Larval mosquito-habitat, adult mosquito-host associations, and pyloric armature and spine structures generally conformed to previously published accounts, indicating that mosquito biology inside zoos represents mosquito biology outside zoos. Therefore, zoos can be used for experiments not feasible in the field. However, novel variation (e.g., new, exotic host records) recorded in mosquito species warrants further investigation in zoos. My study demonstrates that zoos can be used as experiment environments to study mosquito behaviors (e.g., oviposition cues, innate versus learned host preferences, mosquito dispersal, and home range memory), and that findings can be extrapolated to non-zoo areas, while also providing medical and veterinary benefits to zoo animals, visitors, and the public

Recently Evolved Francisella-Like Endosymbiont Outcompetes an Ancient and Evolutionarily Associated Coxiella-Like Endosymbiont In the Lone Star Tick (\u3ci\u3eAmblyomma americanum\u3c/i\u3e) Linked to the Alpha-Gal Syndrome

Background: Ticks are hematophagous arthropods that transmit various bacterial, viral, and protozoan pathogens of public health significance. The lone star tick (Amblyomma americanum) is an aggressive human-biting tick that transmits bacterial and viral pathogens, and its bites are suspected of eliciting the alpha-gal syndrome, a newly emerged delayed hypersensitivity following consumption of red meat in the United States. While ongoing studies have attempted to investigate the contribution of different tick-inherent factors to the induction of alpha-gal syndrome, an otherwise understudied aspect is the contribution of the tick microbiome and specifically obligate endosymbionts to the establishment of the alpha-gal syndrome in humans. Materials and Methods: Here we utilized a high-throughput metagenomic sequencing approach to cataloging the entire microbial communities residing within different developmental stages and tissues of unfed and blood-fed ticks from laboratory-maintained ticks and three new geographical locations in the United States. The Quantitative Insights Into Microbial Ecology (QIIME2) pipeline was used to perform data analysis and taxonomic classification. Moreover, using a SparCC (Sparse Correlations for Compositional data) network construction model, we investigated potential interactions between members of the microbial communities from laboratory-maintained and field-collected ticks. Results: Overall, Francisellaceae was the most dominant bacteria identified in the microbiome of both laboratory-raised and field-collected Am. americanum across all tissues and developmental stages. Likewise, microbial diversity was seen to be significantly higher in field-collected ticks compared with laboratory-maintained ticks as seen with a higher number of both Operational Taxonomic Units and measures of species richness. Several potential positive and negative correlations were identified from our network analysis. We observed a strong positive correlation between Francisellaceae, Rickettsiaceae, and Midichloriaceae in both developmental stages and tissues from laboratory-maintained ticks, whereas ovarian tissues had a strong positive correlation of bacteria in the family Xanthobacteraceae and Rhizobiaceae. A negative interaction was observed between Coxiellaceae and Francisellaceae in Illinois, and all the bacteria detected from ticks from Delaware were negatively correlated. Conclusion: This study is the first to catalog the microbiome of Am. americanum throughout its developmental stages and different tissue niches and report the potential replacement of Coxiellaceae by Francisellaceae across developmental stages and tissues tested except in ovarian tissues. These unique and significant findings advance our knowledge and open a new avenue of research to further understand the role of tick microbiome in tick-borne diseases and develop a holistic strategy to control alpha-gal syndrome

Effects of pyriproxifen on aedes japonicus development and its auto-dissemination by gravid females in laboratory trials

In a series of laboratory experiments, we investigated the effects of the juvenile-hormone analog pyriproxyfen on the inhibition of Aedes japonicus adult emergence after exposure of late-stage (3rd/4th) larvae (either field-collected or lab-reared from field-collected eggs) to pyriproxyfen. Emergence inhibition was 74%, 83%, 86%, and 92% at 0.01, 0.5, 2.5, and 5 μg/liter, respectively. Additionally, following a 1-day exposure of larvae to pyriproxyfen-containing water (5 μg/liter), and for a separate cohort exposed to that same water 10 days later, significantly more pupae died resulting in fewer adults emerged in the treatment versus control group. In 4 tent trials, gravid adult females were able to auto-disseminate a 5% pyriproxyfen powder to larval development habitats at high enough concentrations to cause a significant increase in inhibition of adult emergence. Therefore, we conclude that pyriproxyfen has a great potential for use in controlling this invasive cryptic breeder

Environmental Drivers of Gulf Coast Tick (Acari: Ixodidae) Range Expansion in the United States

Abstract In the United States, the Gulf Coast tick (Amblyomma maculatum Koch) is a species of growing medical and veterinary significance, serving as the primary vector of the pathogenic bacterium, Rickettsia parkeri (Rickettsiales: Rickettsiaceae), in humans and the apicomplexan parasite, Hepatozoon americanum, in canines. Ongoing reports of A. maculatum from locations outside its historically reported distribution in the southeastern United States suggest the possibility of current and continuing range expansion. Using an ecological niche modeling approach, we combined new occurrence records with high-resolution climate and land cover data to investigate environmental drivers of the current distribution of A. maculatum in the United States. We found that environmental suitability for A. maculatum varied regionally and was primarily driven by climatic factors such as annual temperature variation and seasonality of precipitation. We also found that presence of A. maculatum was associated with open habitat with minimal canopy cover. Our model predicts large areas beyond the current distribution of A. maculatum to be environmentally suitable, suggesting the possibility of future northward and westward range expansion. These predictions of environmental suitability may be used to identify areas at potential risk for establishment and to guide future surveillance of A. maculatum in the United States.</jats:p