Differential Tick-Infestation Rate between Rattus norvegicus and R. rattus, with the First Records of the Ixodid Tick Ixodes granulatus and Its Infestation in Rodents, Free-Ranging Cats, and Humans from Mikura-Shima Island, Japan

Abstract

Relatively few studies have investigated host-tick relationships in island environments. To assess the relationships, we captured a total of 51 rodents (Norway rat, n = 29; black rat, n = 22) from which a total of 56 ticks were collected to assess host-tick relationships on Mikura-shima Island, Izu Islands, Japan. We also collected two ticks from a free-ranging cat and a tick from a human resident on the island. The 53 morphologically identifiable ticks were Ixodes granulatus, whose distribution on Mikura-shima Island was not previously reported. Interestingly, the tick infestation rates significantly differed between two rodent species: 44.8% (n = 29) in the Norway rats and 4.5% (n = 22) in the black rat. This insight prompts consideration of the mechanisms behind the differential tick-infestation rate in wildlife hosts and infectious disease transmission in rodent-dominated ecosystems. This study is also the first record of this ixodid infesting domestic cats and a human from the Izu Islands and is the second case of this ixodid biting a human in Japan. Future work should characterize the tick fauna of the island environment and the potential risks of tick-borne diseases.

Host, season, habitat and climatic factors as drivers of Asian rodent tick (Ixodes granulatus) (Acari: Ixodidae) occurrence and abundance in Southeast Asia

“…Human infestation by I. granulatus has been recorded in numerous countries including Singapore (Paperna, 2006), Malaysia (Audy et al, 1960), Thailand (Tanskul et al, 1983), Vietnam (Grokhovskaya and Nguyen, 1968), South Korea (Yun et al, 2014), and Japan (Doi et al, 2022). Adult female I. granulatus are most commonly encountered either crawling on, or attached to, humans (e.g., Guglielmone and Robbins, 2018;Kwak, 2020;Doi et al, 2022), though infestations caused by larvae have also been described (Paperna, 2006). Infestations by I. granulatus reportedly cause lesions at the site of the bite, though no other impacts have yet been reported (Paperna, 2006).…”