Recently the researches on acari-borne infectious diseases including emerging and re-emerging diseases in Japan are very progressive. Surveillance of these diseases is important and necessary from the point of view of geopathology inside and neighboring areas of Japan. Here I considered various factors of geopathology, especially distributional patterns of vector acari in association with prevalences of pathogens and human cases.

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It is known that, Orientia tsutsugamushi (Ot), the causative agent of tsutsugamushi disease, shows the diversity of serotype and genotype. Recent studies, such as the rediscovery of classical tsutsugamushi disease in Akita Prefecture, and several reports of Shimokoshi type in Tohoku district, revealed the antigenic variation of Ot. The antigen needs to be selected according to the distribution of Ot, which affects sensitivity of serological diagnosis. Therefore, it is necessary to accumulate the information of antigenic diversity and the geographical distribution of mite vectors in each region.

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Recently, ticks, which live in Japan, have been reported to possess various types of rickettsial agents. Case reports on Japanese spotted fever casing by Rickettsia japonica, which was found by Mahara in 1984, are continuing to increase. Until now, R. japonica has isolated and/or detected from Haemaphysalis hystricis and other various ixodids. And recent year, a patient of Far Eastern spotted fever by R. heilongjiangensis was identified in Japan, also its vector H. concinna, and its natural cycle were confirmed. Moreover, spotted fever cases by R. helvetica and R. tamurae have been reported. Most of anthropod-borne infectious diseases have known to have specific correlation between species of vector and pathogen. However, rickettsial agents and ticks might have interesting diversity in their relationship. In this report, we summarized the relationship among spotted fever group Rickettsia, vector ticks and human cases.

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Anaplasmosis and Ehrlichiosis are tick-borne and emerging infectious diseases caused by the obligatory intracellular bacteria Anaplasma phagocytophilum and Ehrlichia chaffeensis, respectively. These infectious diseases were first discovered in the United States during the 1990s. In Japan, A. phagocytophilum specific genes were recently detected from several tick species. Although the E. chaffeensis gene was detected from sika deer (Cervus nippon nippon), tick species as arthropod vectors are still unknown. Here, we summarize and introduce these two emerging infectious diseases and their potential tick vectors in Japan.

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Lyme disease and relapsing fever are arthropod-borne infectious diseases caused by the genus Borrelia. These infectious pathogens are maintained by wildlife reservoirs and are transmitted to humans by arthropod vectors. It is, therefore, impossible to eradicate these pathogens from the environment. For this reason, there is currently an international trend toward focusing on understanding the mechanisms of pathogen transmission in order to ultimately prevent disease by interrupting the route of transmission. It is the intent of this review to detail the most recent understanding of the mechanisms by which Borrelia spp. are transmitted by hard-bodied ticks.

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Human dermatitis caused by the bite of the larval trombiculid mite, Leptotrombidium scutellare, was observed by exposing a larva to the skin of a volunteer. Twenty four hours after the bite, a small erythematous macule with itching developed and expanded by 72 hours. The skin lesion gradually improved and had almost disappeared 2 weeks later. Histopathological study of the erythematous macule 48 hours after the bite showed inflammatory infiltrates consisted of lymphocytes in the upper dermis. Immunohistochemically, most lymphocytes in the upper dermis were CD3-positive and CD20-negative. These results suggest that the dermatitis caused by the bite of larval Leptotrombidium scutellare was induced by delayed-type hypersensitivity to saliva substances.

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Since 1993, no cases infected with high pathogenic Kato type of Orientia tsutsugamushi (O.tsutsugamushi) had occurred. However, in August, 2008, we found a patient with tsutsugamushi disease (scrub typhus) who had the antibody against Kato serotype antigen the titer of which was raised at the level of the convalescent phase. The patient resided along Omono river, Daisen city, Akita Prefecture, Japan. We surveyed the vector mites and the field mice as hosts around the endemic locality, from spring to autumn, 2009. We found out Leptotronbidium akamushi (L. akamushi) and succeeded to isolate the Kato type of O. tsutsugamushi from the field mice at the endemic locality. L. akamushi were also found at the famous place for national fireworks in Daisen city, not so distant from the endemic locality. In order to avoid additional latent infections among the local residents or tourists, it is necessary to enlighten that there is risk of infection with this disease along Omono river in summer.

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We observed the prognosis of clinical symptoms and histopathological alternations of human dermatitis in a 61-year-old man, who had been bitten by the unfed larval trombiculid mites Leptotrombidium akamushi (Brumpt, 1910), during a field survey of trombiculid mites at the hot spot of Tsutsugamushi disease on the river side of the Omonogawa River, Omagari, Akita prefecture. The victim first noticed bites by the L. akamushi larvae on 12 sites comprised thin or tender areas in the neck, elbow folds, armpits, and around the nipples approximately 12 hours’ post-infestation. The average mite-feeding period was 59.3 hours. The pain persisted for 24–96 hours after each larva detached. The small erythematous macules lasted for several days to 1 week and then subsided gradually, leaving residual pigmentation for approximately 1–2 weeks. Histopathological examinations of the victim’s skin at 30, 40, and 54 hours’ post-infestation revealed that the larvae had formed mesenchymal stylostomes that penetrated through the epidermis into the dermis. Inflammatory cells such as histiocytes, lymphocytes, and neutrophils were observed around the stylostomes, but few eosinophilic leukocytes were seen. This report differs from those of animal experiments because it clarifies the natural infestation time of L. akamushi larvae on the human body.

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We devised enzyme linked immunosorbent assay (ELISA) and Dot-ELISA for serodiagnosis of spotted fever using the alkali polysaccharides (APS) as antigens and the usefulness in carrying out in the general inspection facilities was examined. The APS extracted from some spotted fever group rickettsiae (SFGR) was sensitized in the well of Immuno Module (Nunc) and the modules were preserved at －20°C after washed. Dot-ELISA used with the cellulose membrane adsorbed by the aspiration with 2 µl of antigen and the membrane was preserved at 4°C after dehydration. The test sera were obtained from a patient with Japanese spotted fever (immunoperoxidase IgG-titer, ×1,280) and a normal human serum. The technique was done according to the approximately general ELISA procedures. The antibody titers of the patient's serum were ×1,600–3,200 in IgG-ELISA and IgG-Dot-ELISA was positive by ×200 dilution serum. The antigenicities of APS sensitized modules and cellulose membranes were stable for at least 6 months at 4°C. Therefore, the ELISA and Dot-ELISA with APS antigens could be useful tests for simple diagnosis for spotted fever group rickettsiosis.

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In a review of previous reports and our original data by the year of 2012, we confirmed three genera and 15 species of ticks, and five species of tick-borne rickettsiae in Fukushima Prefecture, Japan. Tick species were Argas japonicus, A. vespertilionis, Haemaphysalis flava, H. japonica, H. longicornis, H. megaspinosa, Ixodes angustus, I. columnae, I. monospinosus, I. nipponensis, I. ovatus, I. persulcatus, I. tanuki, I. turdus and I. vespertilionis. Tick-borne rickettsiae were ‘Candidatus Ehrlichia ovata' from I. ovatus, Rickettsia asiatica from I. ovatus, R. helvetica from I. columnae, Rickettsia sp. In56 from I. nipponensis and Rickettsia sp. LON from H. longicornis.

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Transovarial transmission rates of Orientia tsutsugamushi were analyzed in naturally infected colonies of Leptotrombidium chigger mite species by improved immunofluorescent microscopy. All 377 embryos derived from 13 infected females of L. fletcheri harbored O. tsutsugamushi. Transovarial transmission rates among L. arenicola females varied between 40 and 100% with the overall transmission rate being 92.6%. However, the transmission rate in L. pallidum markedly declined over 17 generations and infected females produced fewer eggs. These observations suggested that the interaction between Leptotrombidium and O. tsutsugamushi is variable.

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We report a case of tick bite caused by Amblyomma testudinarium with a clinical feature of erythema migrans. The patient, a 60-year-old female, went hiking in the Rokko mountains in Hyogo prefecture on June 30. An erythematous macule with mild itching and a biting tick was found on the right side of her abdomen on July 2. On the first visit (July 4), an annular erythema of 10 cm in size was recognized on the abdomen. She had no systemic symptoms and laboratory data were within normal limits. The tick was identified as a nymph of Amblyomma testudinarium. The skin rash was successfully treated with topical corticosteroids and had almost disappeared 2 weeks later without antibiotics. Serum antibody titers against Borrelia afzelii , B. burgdorferi, and B. garinii on the first visit and 1 month later were negative. These results indicate that the skin rash in this case, erythema migrans, was not associated with Lyme disease but an allergic reaction to salivary gland substances of the tick. Similarities between southern tick-associated rash illness and our case (tick-associated rash illness) are also discussed in this report.

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Here we report two cases of annular erythema caused by Ixodes persulcatus tick bites without positive results for Lyme borreliosis infection. Case 1, a 60-year-old female, hiked around Mt. Eboshidake in Nagano prefecture on July 14 and found a thumb-sized erythema with a tick on her waist on July 20. The biting tick was spontaneously removed. An annular erythema of 55×36 mm in size was recognized on July 25. She had no systemic symptoms or abnormal laboratory data. Histopathological study showed dermal inflammatory infiltrates and the degeneration of collagen fibers, which suggested a tick bite. Case 2, a 38-year-old female, hiked around Mt. Daisetsuzan in Hokkaido prefecture between July 15 and 18. She found a biting tick on her back and removed it on July 22. An annular erythema developed and expanded between July 25 and 29. Skin rashes in these cases were successfully treated with oral amoxicillin or minocycline and had almost disappeared 2 weeks later. Sera antibody titers against Borrelia afzelii, B. burgdorferi, and B. garinii were negative. These cases indicate that annular erythema associated with tick bites is not always Lyme disease, but can be due to a tick-associated rash illness.

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The author attempted to observe larval ticks and mites by low evacuated scanning electron microscopy, in order to evaluate the operating efficiency and the usefulness for morphological identification of minute acarid group. As results, this microscopy was remarkably useful to take excellent photomicrographs and to improve the manner of identification.

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