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Temperate zones of North America are significantly affected by ixodid tick species that are able to transmit viruses, bacteria and protozoa of high medical and veterinary importance. The most widespread ticks in this context belong to the genera Ixodes and Dermacentor, but (unlike in the temperate zones of Europe) Amblyomma species are also indigenous. Although tick infestation of pet animals and the significance of tick-borne pathogens has long been studied in the USA, this epidemiological scenario should be continuously monitored, especially in such states which were underrepresented in previous research. The aim of this work is to provide new data on mitochondrial genetic markers (haplotypes) and tick-borne bacteria, parasites in two northeastern US states. For this, ixodid ticks were analyzed morphologically and molecularly. These were collected between 2019-2024 randomly from pet animals (dogs, cats, horses) and humans at two veterinary clinics (in Strongsville, Ohio and in Earlysville, Virginia).

In total, 111 ticks were collected, 88 in Ohio and 23 in Virginia. The majority of ticks were Dermacentor variabilis (n=76), followed by Ixodes scapularis (n=16), Amblyomma americanum (n=18) and Amblyomma maculatum (n=1). Considering their host-related distribution, A. americanum was the only tick species collected from all four sampled host species, followed by D. variablilis which was the predominant tick species on dogs, cats as well as humans. Interestingly, I. scapularis nymphs were only found to infest cats.

Molecular analysis of the cytochrome c oxidase subunit I (cox1) and 16S rRNA genes revealed that the relative frequency of haplotypes was lower among D. variabilis specimens than among I. scapularis. While A. americanum haplotypes from Virginia were closely related to those reported from Florida, A. maculatum from Ohio had 100% 16S rRNA sequence identity to the so-called morphotype-III reported from Arizona and Mexico.

Regarding tick-borne pathogens, in I. scapularis, from both Ohio and Virginia, an unnamed Rickettsia sp. closely related to Rickettsia monacensis was identified. In D. variabilis, Rickettsia bellii was shown to be present in Ohio, and Rickettsia montanensis in Virginia. Another sequence from the DNA extract of the leg of the male A. maculatum (Ohio) showed 99.7% identity to the type strain of Rickettsia parkeri. Finally, Rickettsia conorii subsp. raoultii was detected in three A. americanum, all from Virginia. Considering piroplasms, Babesia odocoilei occurred in I. scapularis from Ohio, and Theileria cervi, two unnamed Babesia sp. and Babesia sp. Coco in A. americanum from Virginia.

Here, new data are provided in the case of tick species from Ohio and Virginia, in the contexts of their morphology, mitochondrial genetic markers, geographic relationships as well as their potential role in the transmission of pathogens.