The author’s long research career on noxious arthropods has been focused on clarifying the onset mechanism of dermatitis caused by arthropods and investigating the current situation of arthropod-related cutaneous disorders. This report presents four findings from the author’s research. First, dermatitis caused by Arna pseudoconspersa larvae is the result of an immediate or delayed allergic reaction to toxic substances in the venomous spicules. Second, when feeding on a host’s blood, bed bugs use their mouthpart to pierce the host’s skin in several locations, so patients with bed bug bites present with a characteristic, irregularly patterned rash. Third, a study on tick bites in Hyogo Prefecture showed that about 80% of bites were due to Amblyomma testudinarium. The study also found that tick-associated rash illness manifesting in erythema with diameters of at least 50 mm is seen in about 14% of patients with tick bites, and this illness is considered to be caused by an allergic reaction to salivary gland substances of the tick. Fourth, a study by the author revealed that the prevalence of Japanese spotted fever has been increasing in the Rokko Mountain area in recent years and that some ticks from this mountain range carry Rickettsia japonica infection.

Tick-borne diseases are a serious concern in Japan, and it is important to clarify the factors determining the distribution of hard ticks (Acari: Ixodida: Ixodidae). To investigate how the presence of sika deer ( Cervus nippon Temminck, 1838) affects the distribution of hard ticks, hard ticks were collected from 28 sites in Tottori Prefecture, western Japan, in early summer (June) and autumn (October) of 2019. In addition, data on fecal pellets of sika deer were recorded in October of 2019 and April of 2020. A total of 14,490 ticks of four genera and nine species were collected. Two species of Haemaphysalis, H. megaspinosa Saito, 1969, and H. longicornis Neumann, 1901, accounted for 94% of the total individuals. A generalized linear model revealed that the number of fecal pellets was positively related to the abundance of the dominant species, H. megaspinosa, while the total number of hard ticks and the abundances of two dominant species, H. longicornis and H. flava Neumann, 1897, showed no relationship to the number of fecal pellets. The present study suggested that sika deer might affect the population density of a hard tick species, but the relationship was complex.

During the 3-year period (2020–2022), 49 cases of tick bites were presented to the Japanese Red Cross Ashikaga Hospital in Tochigi Prefecture, Japan. More than 60% of all tick bites between March and September occurred within two months (May and June). Amblyomma testudinarium was responsible for 40 cases among all the tick bite cases. Specifically, 41 individuals of this species (39 nymphs/2 adult females) were linked (The point estimate was 0.79 with a 95% confidence interval of 0.67–1.00). There were 38 cases of tick bites in Ashikaga City, and 23 of which occurred in the vicinity of the patients’ houses (gardens and fields). Suspected cases of Tick-associated rash illness (TARI) were first recorded in the Japanese Red Cross Ashikaga Hospital in May 2020, in a total of five cases ( i.e., the patients were aged 50 years or older). TARI is indicative of repeated tick bites, which points to the permanent settlement of the A. testudinarium in and around Ashikaga City. Therefore, we believe that greater efforts should be implemented towards the detection of tick-associated infections in this area, including Severe fever with thrombocytopenia syndrome virus for which A. testudinarium is considered as a major vector.

To prepare for an epidemic of mosquito-borne diseases, such as dengue, we conducted a training of experienced and inexperienced insecticide sprayer for the control of Aedes albopictus at Shinjuku Gyoen National Garden in 2022. Insecticide spraying areas were done by experienced and inexperienced sprayers. After insecticide treatment, no mosquitoes were found in both areas treated by experienced and inexperienced sprayers. Thus, the effectiveness of insecticide application on the basis of mosquito density did not differ between experienced and inexperienced sprayers. However, the experienced sprayers completed spraying faster than the inexperienced sprayers. These results suggest the importance of spray training and handling spray devices during normal times.