Molecular Detection of Pathogenic Bacteria in American Dog Ticks (<i>Dermacentor variabilis</i>) in Brown County, Nebraska

Ticks carry and transmit disease pathogens that cause many human illnesses. Many of these diseases in humans are accompanied by a wide variety of symptoms making tick-borne illnesses often difficult to diagnose. The rate of reported tick-borne illnesses in humans has increased during the past decades in the United States, alongside a rise in concern for public health and safety. In northern Nebraska, the American dog tick (Dermacentor variabilis) is the primary tick encountered by humans and domestic animals in the region. This species is a known vector for spotted fever group (SFG) rickettsioses and tularemia (Francisella tularensis). Both bacteria are pathogenic in humans, and prevalence rates in tick populations can provide important information on possible public health implications for an area. Our study surveyed ticks in Brown County, Nebraska, where we collected ticks from May through June in 2022. Multiplex and singleplex PCR analyses were conducted on DNA samples from individuals to screen for the six most common tick-borne pathogens in the central United States: SFG rickettsiae, Borrelia burgdorferi, F. tularensis, Ehrlichia chaffeensis, Ehrlichia ewingii, and Anaplasma phagocytophilum. We collected 291 American dog ticks during collections in Brown County, consisting of 129 males and 162 females. Five individuals tested positive for SFG rickettsiae, and 15 tested positive for tularemia. This research brings attention to possible concerns of tick-borne illness in north-central Nebraska, particularly transmission of F. tularensis from tick bites. Tularemia can be fatal, but early detection and treatment with antibiotics improves patient prognosis. Information on rates of pathogen prevalence in ticks can lead to more accurate and rapid diagnoses by healthcare providers and better educate citizens about risks of contracting tick-borne diseases while conducting outdoor activities.