Date of this Version
The prevalence of tick-borne diseases has been increasing in the United States for the past couple decades. Studies have been conducted throughout the US identifying tick-borne disease pathogens as well as their hosts and prevalence. Research was conducted in Nebraska to determine the presence of some tick-borne disease pathogens, their vectors, and their hosts, with emphasis made on Borrelia spp., Rickettsia rickettsii, and Ehrlichia chaffeensis.
Small rodents in southeast Nebraska were trapped and sampled at eight study sites using live capture traps. Captured rodents were assessed for active parasitism by ticks which were collected and placed in alcohol. Tissue samples were then taken and analyzed using PCR for Rickettsia rickettsii and Borrelia sp. spirochetes. All 504 ticks collected from the 212 various rodents were identified as either larval or nymphal American dog ticks, Dermacentor variabilis (Say). Infestation prevalence was 51% (109/212) total with highest prevalence seen in Peromyscus maniculatus (58%), Peromyscus leucopus (51%) and Mus musculus (35%). No evidence of either pathogen was identified by PCR.
Retropharyngeal lymph node samples from across Nebraska were taken from hunter-killed deer during the open rifle season and analyzed for the presence of Ehrlichia chaffeensis and Borrelia sp. spirochetes by PCR. Lymph node samples from southeast Nebraska, south-central Nebraska, and mid-central Nebraska were selected for analysis. Ehrlichia chaffeensis was identified in lymph node samples from all three study sets. Southeast Nebraska had 10 positive samples (10/49 – 20%), south-central had 14 positive samples (14/50 – 28%) and mid-central had one positive result (1/50 – 2%). The overall prevalence from all localities tested was 17% (25/149). No positive PCR samples were identified containing Borrelia sp. DNA.
This study demonstrates that lone star tick-associated pathogens are present in Nebraska wildlife. Transmission of these pathogens is probable as white-tailed deer are reservoirs for some of the pathogens demonstrated in this study. Further epidemiological and ecological studies are warranted as these organisms are of veterinary and public health importance.
Advisor: Roberto Cortinas
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