AUTHOR=Weaver Genevieve V. , Anderson Neil , Garrett Kayla , Thompson Alec T. , Yabsley Michael J. 

TITLE=Ticks and Tick-Borne Pathogens in Domestic Animals, Wild Pigs, and Off-Host Environmental Sampling in Guam, USA

JOURNAL=Frontiers in Veterinary Science

VOLUME=8

YEAR=2022

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.803424

DOI=10.3389/fvets.2021.803424

ISSN=2297-1769

ABSTRACT=<p><bold>Background:</bold> Guam, a United States of America (USA) island territory in the Pacific Ocean, is known to have large populations of ticks; however, it is unclear what the risk is to wildlife and humans living on the island. Dog (<italic>Canis familiaris</italic>), cat (<italic>Felis catus</italic>), and wild pig (<italic>Sus scrofa</italic>) sentinels were examined for ticks, and environmental sampling was conducted to determine the ticks present in Guam and the prevalence of tick-borne pathogens in hosts.</p><p><bold>Methods and Results:</bold> From March 2019-November 2020, ticks were collected from environmental sampling, dogs, cats, and wild pigs. Blood samples were also taken from a subset of animals. A total of 99 ticks were collected from 27 environmental samples and all were <italic>Rhipicephalus sanguineus</italic>, the brown dog tick. Most ticks were collected during the dry season with an overall sampling success rate of 63% (95% CI: 42.4–80.6). 6,614 dogs were examined, and 12.6% (95% CI: 11.8–13.4) were infested with at least one tick. One thousand one hundred twelve cats were examined, and six (0.54%; 95% CI: 0.20–1.1) were found with ticks. Sixty-four wild pigs were examined and 17.2% (95% CI: 9.5–27.8) had ticks. In total, 1,956 ticks were collected and 97.4% of ticks were <italic>R. sanguineus</italic>. A subset of <italic>R. sanguineus</italic> were determined to be the tropical lineage. The other tick species found were <italic>Rhipicephalus microplus</italic> (0.77%), <italic>Amblyomma breviscutatum</italic> (0.77 %), and a <italic>Haemaphysalis</italic> sp. (0.51%). Blood samples from 136 dogs, four cats, and 64 wild pigs were tested using polymerase chain reaction (PCR) and DNA sequencing methods. Five different tick-borne pathogens with the following prevalences were found in dogs: <italic>Anaplasma phagocytophilum</italic> 5.9% (95% CI: 2.6–11.3); <italic>Anaplasma platys</italic> 19.1% (95% CI: 12.9–26.7); <italic>Babesia canis vogeli</italic> 8.8% (95% CI: 4.6–14.9); <italic>Ehrlichia canis</italic> 12.5% (95% CI: 7.5–19.3); <italic>Hepatozoon canis</italic> 14.7% (95% CI: 9.2–28.8). <italic>E. canis</italic> was detected in one cat, and no tick-borne pathogens were detected in wild pigs. Overall, 43.4% (95% CI: 34.9–52.1) of dogs had at least one tick-borne pathogen. Serological testing for antibodies against <italic>Ehrlichia</italic> spp. and <italic>Anaplasma</italic> spp. showed prevalences of 14.7% (95% CI: 9.2–28.8) and 31.6% (95% CI: 23.9–40), respectively.</p><p><bold>Conclusion:</bold> Four different tick species were found in Guam to include a <italic>Haemaphysalis</italic> sp., which is a previously unreported genus for Guam. Dogs with ticks have a high prevalence of tick-borne pathogens which makes them useful sentinels.</p>