High Prevalence of Rickettsia raoultii and Associated Pathogens in Canine Ticks, South Korea

We studied the prevalence of tickborne pathogens in canine ticks, South Korea, during 2010–2015. Results revealed a high prevalence of the emerging pathogen Rickettsia raoultii. Dog ticks may be maintenance hosts for tickborne pathogens, suggesting the need to continually evaluate the potential public health threat posed by R. raoultii–infected ticks.

ticks were found in 201 (48.9%), Haemaphysalis spp. ticks in 130 (31.6%), H. flava ticks in 71 (17.3%), and I. nipponensis ticks in 7 (1.7%) of 411 dogs (4). A previous study of H. longicornis tick prevalence proposed that, rather than rodents as previously thought, larger mammals, including dogs, might be the hosts for this tick species (5). Additional surveys are needed to assess the natural hosts of H. longicornis ticks.
Several tickborne pathogens were then screened by using primer sets specific to each pathogen (Appendix). The 16S rRNA genes of R. raoultii were found in 149 (40.9%), R. monacensis in 1 (0.3%), and Candidatus Rickettsia principis in 2 (0.6%) of 364 tick pools ( Figure; Appendix Table 1). R. raoultii was detected in 100 nymph and 49 adult H. longicornis ticks in South Korea. R. raoultii-positive ticks were collected from 25 (24.5%) of 102 dogs, a relatively high proportion of those observed in this study.
R. monacensis causes spotted fever-like disease and has been found in multiple hard tick species in several European countries (2). It was detected in 16 (55.2%) of 29 pools of I. nipponensis ticks from small mammals in South Korea (6). In this study, however, R. monacensis was found in only 1 (0.3%) of 364 tick pools, in an adult I. nipponensis tick. One spotted fever group rickettsiae with Candidatus status was also identified in ticks in this study; Candidatus R. principis was identified in 2 (3.0%) of 67 H. japonica douglasii ticks in Russia in 2006 (7). In this study, Candidatus R. principis (0.6%) was detected in 1 H. longicornis nymph and 1 H. flava nymph. Additional tickborne pathogens were detected (Appendix Table 1 Increased seasonal tick populations and activity in the summer and autumn impact the transmission of tickborne pathogens (8). In this study, we collected ticks from May to September, and found that tick abundance and distribution patterns were similar to those in a previous study in South Korea (8), which showed that both ticks and tickborne pathogens were more prevalent in southern regions and during the summer. South Korea is also steadily shifting to a subtropical climate due to global warming (9), which may influence this seasonal effect, as well. In another previous study in South Korea (4), ticks were collected from stray or pet dogs, but no ticks were found on military working dogs. These military dogs received routine veterinary care for preventive ectoparasite treatments. Therefore, tick prevention measures We studied the prevalence of tickborne pathogens in canine ticks, South Korea, during 2010-2015. Results revealed a high prevalence of the emerging pathogen Rickettsia raoultii. Dog ticks may be maintenance hosts for tickborne pathogens, suggesting the need to continually evaluate the potential public health threat posed by R. raoultii-infected ticks.

RESEARCH LETTERS
should be effective in endemic areas with known tick seasons, when infestations are higher.
Our findings indicate the zoonotic potential of dog ticks in South Korea. Physicians and public health officers therefore need to be aware of the high potential and clinical complexity of infection with R. raoultii and other tickborne pathogens in order to confirm suitable testing and treatment needs in endemic areas (10). Therefore, we strongly recommend continuous evaluation of the potential public health threat posed by infected ticks to humans in South Korea. A better understanding of local tick species, including H. longicornis, and a more thorough characterization of TBP agents, such as R. raoultii, are critical.  (COVID-19); the patients were treated with steroids and tocilizumab. We have observed a transient elevation of d-dimer in patients after tocilizumab treatment, which leads to an interesting discussion about whether the pulmonary embolism observed in these COVID-19 patients was due to a persistent hypercoagulable state in the late phase of the disease or a transient one related to tocilizumab.
Tocilizumab is a humanized antihuman interleukin-6 (IL-6) receptor monoclonal antibody that inhibits IL-6 signaling. Use of tocilizumab in the COVID-19 pandemic has been growing. It