My research is on the evolution and ecology of host-pathogen interactions, especially population genetics of invertebrate hosts of Chagas' disease and whirling disease.
The overall questions driving my research center on understanding the ecological and genetic factors contributing to variation in infection and virulence. My studies includes a rich assortment of topics, including host-pathogen population dynamics, vector feeding and host specificity, the evolution of virulence, and the costs of resistance and defense. These investigationsuse molecular ecology, population genetics, and complex systems modeling.
Chagas Disease: Chagas disease, caused by Trypanosoma cruzi, afflicts up to 11 million people in Latin America and causes potentially life-threatening disease in up to one third of those infected. Reducing new infections of Chagas disease ultimately depends on vector control. Knowledge of vector population structure, sources of infesting insects and vector feeding habits are vital to the success of vector control strategies. We are working to develop a basic understanding of these topics in endemic areas of Guatemala using genomics approaches.
The work is done in collaboration with Juan Carlos Pizarro, Universidad de San Francisco Xavier, Sucre, Bolivia, Patricia Dorn Loyola University, New Orleans and Carlota Monroy, Universidad de San Carlos de Guatemala. My graduate students Judith Keller and Raquel Lima are also working on Chagas disease.
Whirling Disease: In collaboration with Billie L. Kerans (Montana State University), and Donna M. Rizzo (University of Vermont), I am helping to characterize Oligocheate communities to monitor Myxobolus cerebralis infection on the Madison River, MT.
In the 1950's, the fish parasite, Myxobolus cerebralis invaded the US from Europe. Although M. cerebralis has been detected in watersheds throughout much of the US, the distribution and severity of whirling disease is both regionally and locally variable.
Myxobolus cerebralis has a two-host life cycle alternating between salmonid fish and the oligochaete worm, Tubifex tubifex. We are examining how the introduced parasite affects genetic variation in the invertebrate host, disease incidence in the vertebrate host and ultimately community dynamics.
Lodh, N., D. Rizzo, B. Kerans, S. McGinnis and L. Stevens. 2015. If you’ve seen one worm, have you seen them all? Spatial community and population genetic structure of three tubificid taxa in Montana watersheds. Freshwater Science.
Stevens, L., M. C. Monroy, A. G. Rodas, R. M. Hicks, D. E. Lucero, L. A. Lyons and P. L. Dorn. 2015. Migration and Gene Flow Among Domestic Populations of the Chagas Insect Vector Triatoma dimidiata (Hemiptera: Reduviidae) Detected by Microsatellite Loci.. J Med Entomol 52(3): 419-428.
Lucero, D. E., W. Ribera, J. C. Pizarro, C. Plaza, L. W. Gordon, R. Pena, L. A. Morrissey, D. M. Rizzo and L. Stevens. 2014. Sources of Blood Meals of Sylvatic Triatoma guasayana near Zurima, Bolivia, Assayed with qPCR and 12S Cloning. PLoS Neglected Tropical Diseases 8: ARTN e3365 DOI 10.1371/journal.pntd.0003365
Klotz, S. A., J. O. Schmidt, P. L. Dorn, C. Ivanyi, K. R. Sullivan, and L. Stevens. 2014. Free-roaming Kissing Bugs, Vectors of Chagas Disease, Feed Often on Humans in the Southwest. The American journal of medicine.
de la Rua, N. M., D. M. Bustamante, M. Menes, L. Stevens, C. Monroy, C. W. Kilpatrick, D. Rizzo, S. A. Klotz, J. Schmidt, H. J. Axen, and P. L. Dorn. 2014. Towards a phylogenetic approach to the composition of species complexes in the North and Central American Triatoma, vectors of Chagas disease. Infect Genet Evol 24: 157-166.
Stevens, L., D. M. Rizzo, D. E. Lucero, and J. C. Pizarro. 2013. Household model of Chagas disease vectors (Hemiptera: Reduviidae) considering domestic, peridomestic, and sylvatic vector populations. J Med Entomol 50: 907-915.
Fytilis N, Rizzo DM, Lamb RD, Kerans BL, and S. L. 2013. Using real-time PCR and Bayesian analysis to distinguish susceptible tubificid taxa important in the transmission of Myxobolus cerebralis, the cause of salmonid whirling disease. Int J Parasitol 43: 493-501.
Lucero, D. E., L. A. Morrissey, D. M. Rizzo, A. Rodas, R. Garnica, L. Stevens, D. M. Bustamante, and M. Carlota Monroy. 2013. Ecohealth Interventions Limit Triatomine Reinfestation following Insecticide Spraying in La Brea, Guatemala. American Journal of Tropical Medicine and Hygiene 88: 630-637.
Stevens, L., P. L. Dorn, J. Hobson, N. M. de la Rua, D. E. Lucero, J. H. Klotz, J. O. Schmidt, and S. A. Klotz. 2012. Vector blood meals and Chagas disease transmission potential, United States. Emerging Infectious Diseases 18: 646-649.
Lodh, N., B. L. Kerans, and L. Stevens. 2012. The Parasite that Causes Whirling Disease, Myxobolus cerebralis, is Genetically Variable Within and Across Spatial Scales. Journal of Eukaryotic Microbiology 59: 80-87.
Lodh, N., L. Stevens, and B. Kerans. 2011. Prevalence of Myxobolus cerebralis Infections Among Genetic Lineages of Tubifex tubifex at Three Locations in the Madison River, Montana. Journal of Parasitology 97: 531-534.
Stevens, L., P. L. Dorn, J. O. Schmidt, J. H. Klotz, D. Lucero, and S. A. Klotz. 2011. Kissing Bugs. The Vectors of Chagas. Adv Parasit 75: 169-192.
de la Rua, N., L. Stevens, and P. L. Dorn. 2011. High genetic diversity in a single population of Triatoma sanguisuga (LeConte, 1855) inferred from two mitochondrial markers: Cytochrome b and 16S ribosomal DNA. Infect Genet Evol 11: 671-677.
Klotz, J. H., P. L. Dorn, J. L. Logan, L. Stevens, J. L. Pinnas, J. O. Schmidt, and S. A. Klotz. 2010. "Kissing Bugs": Potential Disease Vectors and Cause of Anaphylaxis. Clinical Infectious Diseases 50: 1629-1634.
Pizarro, J. C., and L. Stevens. 2008. A new method for forensic DNA analysis of the blood meal in chagas disease vectors demonstrated using Triatoma infestans from Chuquisaca, Bolivia. PLoS One 3: e3585.
Pizarro, J. C., L. M. Gilligan, and L. Stevens. 2008. Microsatellites reveal a high population structure in Triatoma infestans from Chuquisaca, Bolivia. PLoS Negl Trop Dis 2: e202.
Rigby, M. C., R. F. Hechinger, and L. Stevens. 2002. Why should parasite resistance be costly? Trends in parasitology 18: 116-120.
Stevens, L., R. Giordano, and R. F. Fialho. 2001. Male-killing,nematode infections, bacteriophage infection, and virulence of cytoplasmic bacteria in the genus Wolbachia. Annual Review of Ecology and Systematics 32: 519-545.
Fialho, R. F., and L. Stevens. 2000. Male-killing Wolbachia in a flour beetle. P Roy Soc B-Biol Sci 267: 1469-1473.