Implications of Earlier Emergence of Lone Star Ticks

In the Literature

McClung KL, Sundstrom KD, Lineberry MW, Grant AN, Little SE. Seasonality of Amblyomma americanum (Acari: Ixodidae) activity and prevalence of infection with tick-borne disease agents in north central Oklahoma. Vector Borne Zoonotic Dis. 2023;23(11):561-567. doi:10.1089/vbz.2023.0009

The Research …

Ticks can harbor pathogens that lead to morbidity and mortality in mammals; therefore, knowledge of tick seasonality and potential pathogen transmission is crucial. In the southern United States, Amblyomma americanum (ie, lone star tick) is the species most commonly isolated from humans, domestic animals, wildlife, and the environment.^1-5 A americanum can transmit Ehrlichia chaffeensis, E ewingii, Borrelia lonestari (cause of southern tick-associated rash illness and relapsing fever), Rickettsia spp, and other organisms.

In this study, A americanum (n = 7,990) were collected from forested and grassland habitats in north central Oklahoma twice monthly from September 2020 to August 2022. Researchers collected 941 adults, 2,767 nymphs, and 4,282 larvae. Ticks of all life stages were more common in forested habitats.

At least 100 adults collected during each peak activity month and all adults from nonpeak months were processed for molecular detection of selected pathogens, including E chaffeensis, E ewingii, B lonestari, and Rickettsia spp in the spotted fever group. Rickettsia spp were detected in 26.4% of adult ticks. E chaffeensis and E ewingii were detected in 6.1% and 2.5% of adult ticks, respectively. B lonestari was detected in 1.1% of adult ticks. Coinfections with combinations of Ehrlichia spp, B lonestari, and/or Rickettsia spp were found in 13 ticks.

… The Takeaways

Key pearls to put into practice:

• Pathogens were detected via PCR in 33.7% of adult A americanum; the percentage of these ticks positive for Rickettsia spp was similar to previous reports.^6-8 Nearly 90% of Rickettsia spp were R amblyommatis; the level of morbidity associated with this species is unclear.

• Adult populations of A americanum have historically peaked most often in late May through early June in the study area.⁹ Although females in this study were significantly more active in May, males were significantly more active in March.

• Results of this study indicate adult A americanum are emerging earlier than historic records and a large proportion harbor pathogens that may affect humans and animals, emphasizing the need for year-round tick prevention and pet owner education about risks of tick-borne diseases.