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  1. Rickettsial diseases of the Far East: new perspectives
    Rapmund G
    J Infect Dis, 1984 Mar;149(3):330-8.
    PMID: 6425420
    The rickettsial disease of man found only in Asia is mite-borne (scrub) typhus, caused by Rickettsia tsutsugamushi. Unique to southern Japan is a little-known human mononucleosis-like disease caused by Rickettsia sennetsu. In 1981 and 1982, there was a remarkable resurgence in the number of reported cases of mite-borne typhus in Japan after some years of virtual absence. Recent studies of R sennetsu have resulted in its reclassification to the genus Ehrlichia, members of which until now have been exclusively pathogens of animals. The historical background of ecologic investigations, in Malaysia and elsewhere, of these two developments suggest directions for future research.
    Matched MeSH terms: Ehrlichia/classification
  2. Characterization of the SF agent, an Ehrlichia sp. isolated from the fluke Stellantchasmus falcatus, by 16S rRNA base sequence, serological, and morphological analyses
    Wen B, Rikihisa Y, Yamamoto S, Kawabata N, Fuerst PA
    Int. J. Syst. Bacteriol., 1996 Jan;46(1):149-54.
    PMID: 8573488
    The organism designated the SF agent was originally isolated in Japan in 1962 from Stellantchasmus falcatus metacercaria parasitic on gray mullet fish. The SF agent resembles members of the genus Ehrlichia morphologically and exhibits weak antigenic cross-reactivity with Ehrlichia sennetsu. This organism causes mild clinical signs in dogs, but severe splenomegaly and lymphadenopathy in mice. This suggests that the SF agent may be similar to either Neorickettsia helminthoeca, an intracellular parasite of a fluke and the cause of salmon poisoning disease in dogs, or E. sennetsu, the causative agent of human sennetsu ehrlichiosis in Japan and Malaysia. In order to determine the phylogenetic relationship between the SF agent and other ehrlichial species, the 16S rRNA gene was amplified by the PCR and sequenced. The SF agent sequence was most closely related to the sequences of Ehrlichia risticii (level of sequence similarity, 99.1%), the causative agent of Potomac horse fever, and E. sennetsu (level of sequence similarity, 98.7%). The next most similar sequence was that of N. helminthoeca, but the level of sequence similarity was only 93.7%. E. sennetsu, E. risticii, the SF agent, and N. helminthoeca formed a distinct cluster that was separated from all other ehrlichial species. As determined by immunofluorescence labeling, antiserum against the SF agent cross-reacted strongly with E. sennetsu, E. risticii, and N. helminthoeca. When three genetically distinct ehrlichial isolates obtained from horses with Potomac horse fever were compared with the SF agent, we found that the SF agent was most closely related to Ohio isolate 081, followed by IllinoisT (T = type strain) and a Kentucky isolate. We observed strong antigenic cross-reactivities and similarities in Western blot (immunoblot) reaction profiles when we compared the SF agent, E. risticii, and E. sennetsu; however, weaker antigenic cross-reactivity was observed when the SF agent and N. helminthoeca were compared. Our results indicate that the SF agent is antigenically more closely related to E. risticii and E. sennetsu than to N. helminthoeca. The biological and antigenic characteristics and the 16S rRNA sequence data suggest that the SF agent is a new species that belongs to the genus Ehrlichia.
    Matched MeSH terms: Ehrlichia/classification*
  3. Fulltext Molecular detection of pathogens in ticks and fleas collected from companion dogs and cats in East and Southeast Asia
    Nguyen VL, Colella V, Greco G, Fang F, Nurcahyo W, Hadi UK, et al.
    Parasit Vectors, 2020 Aug 15;13(1):420.
    PMID: 32799914 DOI: 10.1186/s13071-020-04288-8
    BACKGROUND: Ticks and fleas are considered amongst the most important arthropod vectors of medical and veterinary concern due to their ability to transmit pathogens to a range of animal species including dogs, cats and humans. By sharing a common environment with humans, companion animal-associated parasitic arthropods may potentially transmit zoonotic vector-borne pathogens (VBPs). This study aimed to molecularly detect pathogens from ticks and fleas from companion dogs and cats in East and Southeast Asia.

    METHODS: A total of 392 ticks and 248 fleas were collected from 401 infested animals (i.e. 271 dogs and 130 cats) from China, Taiwan, Indonesia, Malaysia, Singapore, Thailand, the Philippines and Vietnam, and molecularly screened for the presence of pathogens. Ticks were tested for Rickettsia spp., Anaplasma spp., Ehrlichia spp., Babesia spp. and Hepatozoon spp. while fleas were screened for the presence of Rickettsia spp. and Bartonella spp.

    RESULT: Of the 392 ticks tested, 37 (9.4%) scored positive for at least one pathogen with Hepatozoon canis being the most prevalent (5.4%), followed by Ehrlichia canis (1.8%), Babesia vogeli (1%), Anaplasma platys (0.8%) and Rickettsia spp. (1%) [including Rickettsia sp. (0.5%), Rickettsia asembonensis (0.3%) and Rickettsia felis (0.3%)]. Out of 248 fleas tested, 106 (42.7%) were harboring at least one pathogen with R. felis being the most common (19.4%), followed by Bartonella spp. (16.5%), Rickettsia asembonensis (10.9%) and "Candidatus Rickettsia senegalensis" (0.4%). Furthermore, 35 Rhipicephalus sanguineus ticks were subjected to phylogenetic analysis, of which 34 ticks belonged to the tropical and only one belonged to the temperate lineage (Rh. sanguineus (sensu stricto)).

    CONCLUSION: Our data reveals the circulation of different VBPs in ticks and fleas of dogs and cats from Asia, including zoonotic agents, which may represent a potential risk to animal and human health.

    Matched MeSH terms: Ehrlichia/classification
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