Background: Healthcare providers commonly encounter patients who present with a clinical syndrome resembling a “tick borne illness.” Powassan/Deer Tick virus (POWV/DTV) is closely related to tick-borne encephalitis virus (TBEV), a viral infection in Europe causing severe neurologic disease in 20-30% of infected patients. The studies described here reveal the prevalence and geographic distribution of Wisconsin ticks carrying POWV/DTV, and the high frequency of ticks co-infected with both POWV/DTV and Borrelia, the causative agent of Lyme disease.
Methods: The Wisconsin DNR and participating civilians supplied over 2000 ticks collected during geographic surveys. Total nucleic acid was extracted from single ticks or tick pools. DNA PCR testing was performed for conserved genomic segments from the 16S rDNA of Borrelia as well as RT-PCR for the NS5 gene of POWV/DTV.
Harvest 1 Tick Distribution Harvest 2 Tick Distribution Harvest 3 Tick Distribution
Results: Harvest 1 showed that of 112 ticks analyzed, 8% harbored more than one infectious agent, and bacteria from the genus Borrelia were present in all cases of co-infection. POWV/DTV was detected in 6.8% of the ticks. Harvest 2 ticks pools had an overall Borrelia prevalence of 11%, and POWV/DTV was detected at close to 6% with distribution across the state. Harvest 3 ticks collected from a localized, hyper-endemic area supports the concept of localized “hot spots” in which ticks with an abnormally high frequency of one or more pathogens may be encountered. Of the 19 ticks tested, ten were found positive for Borrelia (52.6%) and two of the Borrelia positive ticks were co-infected with POWV/DTV (11%).
Conclusion: Viral co-infections in ticks provide an alternative hypothesis as to why the causative agent of chronic “tick borne illness” symptoms may go undiagnosed, and why antibiotic treatment regimens fail in up to 20% of patients. This survey also broadens the geographical representation of tick-borne arboviruses and enhances awareness that these agents represent a public health concern. Finally, while researchers and physicians may be aware of the clinical implications of TBEV infection, they may not be knowledgeable that POWV/DTV can cause similar disease in the U.S.
Y. Harrington, None
D. Baewer, None
D. Carrigan, None