Vector-borne disease systems are inherently complex and community-driven due to the complex species and trophic interactions involved in their maintenance and transmission. Research in the Swei Lab employs interdisciplinary approaches to understand the factors that determine the distribution and prevalence of Lyme disease and other tick-borne diseases. Ticks vector a large proportion of zoonotic diseases in the United States. Research in the Swei lab focuses on several different tick-borne disease systems such as Lyme disease, babesiosis, and Borrelia miyamotoi. Work on Lyme disease includes ecological studies that examine the role of disturbance, habitat fragmentation, and biodiversity on Lyme disease ecology and implements quantitative models to better understand and predict pathogen risk and distribution. In addition, current research projects focus on climate change impacts, pathogen genomics and pathogenesis, and the influence of the vector microbiome on pathogen transmission and vector competency.
Community ecology and habitat disturbance
Habitat fragmentation changes community structure and diversity in many biological systems. These same changes can also affect the maintenance and transmission dynamics of zoonotic diseases including vector-borne ones such as Lyme disease. Ongoing research in the Swei lab is investigating the impact of habitat fragmentation on vertebrate, invertebrate, and microbial species communities.
Lilly, M.; Amaya-Mejia, W.; Pavan, L.; Peng, C.; Crews, A.; Tran, N.; Sehgal, R.; Swei, A. 2022. Local Community Composition Drives Avian Borrelia burgdorferi Infection and Tick Infestation. Vet. Sci. 9, 55.
Salomon, J., Crews, A., Lawrence, A., Swei, A. 2021 Host infection and community composition predict vector burden. Oecologia,
Sambado, S., Salomon, J., Crews, A., Swei, A. 2020. Mixed transmission modes promote persistence of an emerging tick-borne pathogen. Ecosphere 11(6): e03171. https://doi.org/10.1002/ecs2.3171
Lawrence, A.M., O'Connor, K.E., Swei, A. 2018. Patterns of diversity along a habitat size gradient in a biodiversity hotspot. Ecosphere 9 (4): e02183. Open Access Link; https://doi.org/10.1002/ecs2.2183
MacDonald, A., Hyon, D.W., Brewington, J.B., O'Connor, K., Swei, A., Briggs, C. 2017. Lyme disease risk in southern California: abiotic and environmental drivers of Ixodes pacificus (Acari: Ixodidae) density and infection prevalence with Borrelia burgdorferi. Parasites and Vectors.. 10: 7.
MacDonald, A.J., Hyon, D.W., McDaniels, A., O'Connor, K.E., Swei, A., Briggs, C.J. 2018. Risk of vector tick exposure initially increases then declines through time in response to wildfire in California. Ecosphere 9(5):e02227.
CDC Center of Excellence
New Funding! CDC Center of Excellence in Vector borne Diseases for the Pacific Southwest region (PacVec) has been renewed for another 5 years of funding! As part of the leadership team, PI Swei will lead studies to mitigate the risk of tick-borne diseases using community ecology informed approached to vector management and reservoir host control. Trials are underway to test the efficacy of host-targeted vaccines to reduce the density of infected, host-seeking ticks in the wild.
Tick microbial communities
Ticks are the most important disease vector in the Northern hemisphere and transmit Lyme disease in addition to other pathogens. Ongoing research in the lab includes investigating the role of the tick microbiome in pathogen transmission and vector-competency. With the use of next generation deep sequencing, we have been exploring the microbial community of several species of ticks such as the Lyme disease vector, Ixodes pacificus, as well as other species: Dermacentor occidentalis, Ixodes angustus, Haemaphysalis leporispalustris.
Investigations of the tick microbiome has revealed surprising patterns governing the development of the tick microbiome and potential impacts on pathogen transmission. One key finding is that blood meal host identity plays a significant role in structuring the microbiome Ixodes pacificus. These impacts on microbiome composition and structure appears to influence the vector competency of I. pacificus for B. burgdorferi.
Couper, L.I., Kwan, J.Y., Ma, J., Swei, A. 2019. Drivers and patterns of microbial community assembly in a Lyme disease vector. Ecology and Evolution, 9(2): 7768-7779. DOI: 10.1002/ece3.5361
Couper, L.I. and Swei, A. 2018. Tick microbiome characterization by next-generation 16S rRNA amplicon sequencing. Journal of Visualized Experiments 138: e58239. DOI: 10.3791/58239.
Kwan, J., Griggs, R., Chicana, B., Miller, C., Swei, A. 2017. Vertical versus horizontal transmission of the microbiome in a key disease vector. Molecular Ecology. 26 (23): 6599-6761. DOI: 10.1111/mec.14391
Swei, A. and J. Kwan. 2017. Tick microbiome and pathogen acquisition altered by host blood meal. The International Society for Microbial Ecology. 11: 813-816
Bouquet, J., Melgar, M., Swei, A., Delwart, E., Lane, R.S. and Chiu, C.Y. 2017. Metagenomics of the Pacific Coast tick, Dermacentor occidentalis, in northwestern California, 2011-2014. Nature Scientific Reports. 7: 12234.
Emerging vector diseases
Vector-borne zoonotic diseases (VBZD) are emerging globally. Swei lab and collaborators conducted a meta-analysis of patterns, drivers, and evolutionary contexts for this group of diseases. We found that hard ticks (Ixodidae) and mosquitoes (Culicidae) are responsible for vectoring the vast majority of emerging VBZD. (Swei et al., in review)
In addition to the Lyme disease pathogen, ticks transmit many other pathogens. Detailed epidemiological studies of tick vectors and their animal reservoirs are essential to better characterize and prevent these diseases, many of which are emerging.
One emerging disease that we are working to better characterize is babesiosis. The vector and reservoir hosts of this potentially fatal and blood-transfusion transmitted disease are unknown. In collaboration with the California Department of Public Health and the California Department of Fish and Wildlife, we recently published epidemiological studies to identify the vector and reservoir of the etiological cause of babesiosis in the western United States, Babesia duncani. Current research in the lab also uses spatial modeling approaches to help identify hotspots of risk for emerging tick-borne diseases and to predict likely pathogen reservoirs for zoonotic diseases like Rickettsia 364D.
Paddock, C.D., Slater, K., Swei, A., Zambrano, M.L., Kleinjan, J.E., Padgett, K.A., Saunders, M.E.M., Andrews, E.S., Trent, E., Zhong, J., Sambado, S., Goldsmith, C.S., Pascoe, E.L., Foley, J., Lane, R.S., Karpathy, S.E. 2022. Detection and isolation of Rickettsia tillamookensis (Rickettsiales: Rickettsiaceae) from Ixodes pacificus (Acari: Ixodidae) from multiple regions of California. Journal of Medical Entomology. 59 (4): 1404-1412
Schmeller, D.S., Cheng, T., Shelton, J. Lin, C.F., Alvarado, A.C., Bernardo-Cravo, A., Zoccarato, L. Ding, T.S., Yu, A., Lin, Y.P., Swei, A. Fisher, M, C., Vredenburg, V.T., Loyau, A. 2022. Environment is associated with chytrid infection and skin microbiome richness in an amphibian biodiversity hotspot. Scientific Reports, 12; 16456.
Swei, A., Couper, L.I., Coffey, L.L., Kapan, D., Bennett, S. 2020. Patterns, drivers, and challenges of vector-borne zoonotic disease emergence. Vector Borne Zoonotic Diseases.
Swei, A., O'Connor, K.E.†, Couper, L. †, Conrad, P., Padgett, K., Burns, J., Yoshimizu, M.H., Ben Mamoun, C., Lane, R., Kjemtrup, A. 2019. Evidence for transmission of the zoonotic apicomplexan parasite Babesia duncani. International Journal for Parasitology. https://doi.org/10.1016/j.ijpara.2018.07.002
O'Connor, K.E., Kjemtrup, A., Conrad, P., Swei, A. 2018. A highly sensitive, diagnostic protocol to detect the blood-borne pathogen, Babesia duncani. Journal of Parasitology. https://doi.org/10.1645/17-155
Swei A, Bowie VC, Bowie RCK. 2015. Comparative genetic diversity of Lyme disease bacteria in Northern Californian ticks and their vertebrate hosts. Ticks and Tick-borne Diseases. 6: 414-23.
Swei A, Russell BJ, Naccache SN, Kabre B, Veeraraghavan N, Pilgard, M.A., Johnson, B.J.B., Chiu, C.Y. 2013. The genome sequence of Lone Star Virus, a highly divergent bunyavirus found in the Amblyomma americanum tick. PLoS ONE 8(4): e62083. doi:10.1371/journal.pone.0062083
Swei, A., J.J.L. Rowley, D. Rödder, M. L. L. Diesmos, A. C. Diesmos, C. J. Briggs, R. Brown, T. T. Cao, T. L. Cheng, R. A. Chong, B. Han, J.-M. Hero, H. D. Hoang, M. D. Kusrini, D. T. T. Le, J. A. McGuire, M. Meegaskumbura, M. S. Min, D. G. Mulcahy, T. Neang, S. Phimmachak, D.Q. Rao, N. M. Reeder, S. D. Schoville, N. Sivongxay, N. Srei, M. Stöck, B. L. Stuart, L. S. Torres, D. T. A. Tran, , T. S. Tunstall, D. Vieites, V. T. Vredenburg. Vredenburg. 2011. Is chytridiomycosis an emerging infectious disease in Asia? PLoS ONE 6(8): e23179.
Grants and Funding
Bay Area Lyme
(Active awards in bold text)
National Science Foundation
CAREER award #175037, 2018-2023 (PI Swei)
NSF DEB Population and Community Ecology Cluster #1900534, 2019-2022 (coPI Swei)
EAGER award #1745411, 2017-2020 (PI Swei)
NSF Major Research Instrumentation Award #1427772, 2015-2019 (coPI Swei)
Ecology and Evolution of Infectious Diseases
NSF Graduate Research Fellowship (A. Swei, Marie Lilly)
Centers for Disease Control
Pacific Southwest Centers of Excellence PacVec Leadership team 2022-2027 https://pacvec.us/meet-our-team
Pacific Southwest Centers of Excellence PacVec Training Award, 2021-2022 (Trainee: Grace Shaw; PI Swei)
Pacific Southwest Centers of Excellence PacVec Training Award, 2020-2021 (Trainee: Marie Lilly and Vincent Mai PI Swei)
Pacific Southwest Centers of Excellence PacVec Training Award, 2019-2020 (Trainee: Kacie Ring; PI Swei)
Pacific Southwest Centers of Excellence PacVec Training Award, 2018-2019 (Trainee: Samantha Sambado; PI Swei)
National Institutes of Health
NIH MARC T34-GM008574
NIH MBRS-RISE: R25-GM059298
NIH MS/PhD Bridge: R25-GM048972
Kirschstein Postdoctoral Fellowship
Department of Defense
Instrumentation grant, 2019-2021 (PI Swei)
CSUPERB New Investigator Award
Center for Computing and Life Sciences
SFSU Office of Sponsored Projects Grant
Bay Area Lyme Foundation