Detection of a Novel Rickettsia From Leptotrombidium scutellare Mites (Acari: Trombiculidae) From Shandong of China.

Leptotrombidium scutellare mites, the vector of Orientia tsutsugamushi, have rarely been reported to associate with Rickettsia species. Three hundred nineteen chiggers were collected from the ears of 32 rodents captured in Huangdao District of Qingdao City, China, in October 2015. The chigger samples were tested for Rickettsia, severe fever with thrombocytopenia syndrome virus, and hantavirus by PCR or RT-PCR amplification. All mites were classified morphologically and molecularly as L. scutellare chiggers. Rickettsial DNA sequences were amplified for four genes including 16S rRNA, ompB, gltA, and 17 kD protein genes. The minimum infection rate (MIR; number of positive pools/total specimens tested) of the Rickettsia species in the chiggers were 2.8% (9/319). Phylogenetic analysis indicated that individual genes were closely related to different Rickettsia species including R. felis (with 16S rRNA gene), R. australis (with gltA gene), an unnamed Rickettsia sp. TwKM02 (with ompB gene), and Rickettsia endosymbiont of soft tick Ornithodoros erraticus (with 17 kD protein gene). Phylogenic analysis of the concatenated sequence of 16S rRNA, gltA, ompB, and 17 kD protein genes indicated that the Rickettsia species from L. scutellare chigger was most closely related to R. australis and R. akari. These results indicated that the Rickettsia species in chiggers was unique; it was named Candidatus Rickettsia leptotrombidium. Severe fever with thrombocytopenia syndrome virus and hantavirus were not amplified from the chiggers, suggesting lack of infection of these pathogens in the chiggers. A unique Rickettsia species was detected in L. scutellare, which expanded the knowledge on the vector distribution of Rickettsia.

The role of mites in the transmission and maintenance of Hantaan virus (Hantavirus: Bunyaviridae).

This review examines the evidence indicating a role for parasitic mites in the transmission and maintenance of Hantaan virus in nature. The available data, much of it from recent studies in China, indicate that both trombiculid and gamasid mites are naturally infected with Hantaan virus and that infected mites can transmit the virus by bite to laboratory mice and transovarially (vertically) through eggs to their offspring. Collectively, these findings challenge the current paradigm of hantavirus transmission, namely, that rodents serve as the reservoir of human pathogenic hantaviruses in nature and that humans are infected with these viruses by inhalation of aerosols of infectious rodent excreta. Further research is needed to confirm the mite-hantavirus association and to determine if parasitic mites are in fact the major source and principal vectors of human pathogenic hantaviruses, such as Hantaan. If the mite hypothesis is correct, then it will significantly alter current concepts about the epidemiology, prevention, and control of human hantavirus infection.

Hantavirus transmission: potential role of ectoparasites.

Hantavirus pulmonary syndrome is an often-fatal disease thought to be transmitted exclusively by rodents. We report the first evidence of hantavirus-specific RNA (Bayou) from two trombiculid mites (chiggers) and an ixodid tick parasitizing wild-caught rodents at a field site in Texas and also from a trombiculid mite in the free-living predatory stage of the chigger life cycle collected from the same site.

[Detection and proliferation of hemorrhagic fever virus in chigger mites].

OBJECTIVE: To study the impact of Leptotromhidium scutellaris as a vector in transmission of hemorrhagic fever. METHODS: Reverse transcription-polymerase chain reaction (PCR) and in situ hybridization technique were used to detect RNA of hemorrhagic fever with renal syndrome virus (HFRSV). TCID(50)/ml of HFRSV were titrated for larva and nymph of chigger mites periodically. RESULTS: RNA of HFRSV was detected in the tissues of chigger mites, such as ovary cells, etc. by PCR and in situ hybridization. Titration of TCID(50)/ml showed that HFRSV could be transmitted transstadially and proliferated in chigger mites. CONCLUSION: It provides direct evidence at molecular level for the role of chigger mite as a vector in transmission of HFRSV with theoretical and practical importance in prevention of HFRS.

[Preliminary studies on proliferation of hemorrhagic fever with renal syndrome virus in Leptotrombidium (L.) Scutellare].

In order to observe further the proliferation and kinetic changes of hemorrhagic fever with renal syndrome virus (HFRSV) in Leptotrombidium (L.) Scutellare infected with HFRSV, the raised Leptotrombidium (L.) Scutellare which were at larve stage or at nymph stage were grinded and sterilized by filtration at interval of 20 days, each batch of the filtrate was inoculated separately to Vero-E6 cells and the titre (TCID50/ml) of HFRSV was measured. The results confirmed: HFRSV were isolated from each batch of larve besides the batch at the 60th days, and the titre of HFRSV was -10(-1)-10(-4); HFRSV were also isolated from two batches of nymph. The isolated HFRSV were amplified by PCR technique and the HFRSV RNA were positive. The above results give rise to evidence that Leptotrombidium (L.) Scutellare might be the transmission vector of HFRSV.