hamer lab
host preference & parasite manipulation
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Imagine you are hanging out after a long day in your backyard with your dogs and your chickens. As the sun sets the kissing bugs crawl out of their burrows driven by their hunger for blood. Will the kissing bugs be more attracted to your dogs, chickens, or you? What about if they are infected with Trypanosoma cruzi, the protozoan parasite that causes Chagas disease in humans and dogs. Does their host preference change or does the kissing bugs foraging behaviors change? To understand if kissing bugs have a preference towards common blood meal hosts, and how T. cruzi influences preference, we created a dual-choice olfactometer to allow infected and uninfected kissing bugs to choose between dogs, chickens, or humans. We found that triatomines do have a preference towards dogs over humans and chickens when uninfected with T. cruzi, but when infected all preference disappears. This work identifies that host-targeted interventions could be useful when applied to dogs, but may not be enough in habitats with a high prevalence of Trypanosoma cruzi. Moreover this work illustrates that T. cruzi manipulates kissing bug behaviors in the presence of blood meal host cues.
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vector and pathogen Phenology and vector-host associations
In order to appropriately deploy any management strategies or public health messaging, we need to understand some foundational vector and pathogen patterns. When are vectors most active (vector phenology), when are pathogens circulating in host populations vs in vector populations (pathogen phenology), which pathogens are circulating in sylvatic cycles (pathogen surveillance), and which hosts are vectors interacting with (vector-host associations); are all questions I addressed with a year-long field study set in East Texas.
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Dogs as sentinels for tick-borne diseases
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Various tick species are more tightly associated with specific hosts, but can spillover to feed on incidental hosts. Identifying what pathogens are circulating in these specialized tick species is critical to monitor, especially when they are dependent on human habitats. Rhipicephalus sanguineus have a global distribution but since they are predominantly found on dogs, they are concentrated in human dominant landscapes. They are known to prefer to blood feed on humans over dogs when the temperatures are warmer, in addition to transmitting human pathogenic Rickettsia species. There are on-going outbreaks of spotted-fever rickettsioses in Northern Mexico, however sustainable surveillance of pathogens in vectors is limited. In a bi-national collaboration with Centro de Biotecnología Genómica, we sampled privately owned dogs of Reynosa, Tamaulipas, Mexico to collect blood and ticks to survey for Rickettsia species. All 2,000 plus ticks removed from less than 100 dogs were R. sanguineus sensu lato. One tick was positive for Rickettsia rickettsii a causative agent of spotted fever rickettsioses in humans, in addition to a few Rickettsia amblyommatis postive ticks. This study brings attention to the need for routine surveillance and dogs would be an efficient sentinel for sustainable surviellence.
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Swei lab
trophic interactions of zoonotic parasites in slyvatic cycles
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Some hosts are loaded with parasites, while sympatric conspecifics may be clean. This dynamic is referred to as the 80-20 rule in parasitology, where about 20% of the host population is burdened with 80% of the parasite population. Enamored by this dynamic, I wanted to understand what community level parameters may be associated within wild rodent populations and their attached ticks in fragmented habitats of California Bay Area. We found that across sites, Neotoma fuscipes hosted the majority of the Ixodes pacificus among sympatric rodents and the higher the tick burden the more likely the host was positive for Borrelia burgdorferi sensu lato. Furthermore, we were able to show an association between predator diversity and tick burdens. Where in habitats with a less diverse predator community, the rodents had decreased tick burdens. These sampling sites were across a spectrum of fragmentation so not only is there the risk of human or domestic animal exposure to these tick-borne pathogens, but understanding how they are maintained in these sylvatic cycles is critical for public health messaging and city planning.
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These same rodent populations are not just parasitized by ticks and tick-borne pathogens, but an assortment of other ecto-, endo-, macro-, and micro-parasites. Viewing the individual host as an isolated habitat, these parasites are interacting and sometimes influencing transmission. We described the helminth, tick, and Borrelia assortment among rodent populations to see if co-infections or increased parasite abundance were associated with Borrelia infections. Even though we found co-infections in rodents, we did not find any association between multiparasitic infections and Borrelia infections. Additionally we found woodrats (Neotoma fuscipes) to be burdened the most by these parasites.
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