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Rodents Role in Maintaining the Tick-Borne Disease “Relapsing Fever” in Nature


Issue

Relapsing fever is a zoonotic disease described across the world in which human cases typically present as an undulating fever with many non-specific symptoms including headache, myalgia, and arthralgia. In the USA, tick-borne relapsing fever occurs throughout the mountainous west and southwestern deserts because of infection by spirochete bacteria found in soft tick, the transmission vector. Human infection risk is associated with rodent infestation of a home or cabin, especially after seasonal periods of vacancy. This study surveyed wild rodents infected with spirochetes (B. hermsii) around Big Bear Lake, southern California, identifying and genotyping the species of bacteria found in the hosts from this region.

What has been done

In 2014, 284 chipmunks from the Eastern Sierra Nevada Mountains had microsatellites sequenced at 11 diploid loci. The resulting data split into two simulations, one where only site locations was used, and one where the locations were separated on the habitat type nested with each site. Simulations were put through analysis of subpopulation structure through the program STRUCTURE, and Structure harvester. Model selection was then preformed within and between simulations and a single model was chosen to represent the results.

Impact

Since the tick vectors for relapse fever stay at their nest or birthplace for a long time after birth, these locations may act as the focal point from which infection spreads to the surrounding areas. This could be the most important finding of this analysis due to its implications with public heath, and mitigation strategies to curb, or prevent spillover events from the wild population.

In Big Bear and Twin Lakes, California homeowner association meetings now invite NAES scientists to give annual updates on the prevalence of the disease in their area and ask questions on prevention. Through these meeting, a program was developed for homeowners that spells out what needs to be done when opening up homes and cabins after a winter closure. Since these efforts, outbreaks of the disease in these area have dropped to zero over the past year.

CONTACT INFORMATION

Mike Teglas

Department of Agriculture, Veterinary & Rangeland Sciences

1664 North Virginia Street

Reno, Nevada   89557

 

Phone: (775) 784-1002

Email: mteglas@cabnr.unr.edu

Personal Web Site: