| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 99 === Bartonellae are gram negative, fastidious, rod-shaped bacteria. As the bacterium with the characteristic of infecting erythrocytes and endothelial cells to escape immune responses in hosts, most of Bartonella spp. are arthropod-borne zoonotic agent. Various species of mammals have been shown to be reservoirs of Bartonella. In recent years, even the no-mammalian host, loggerhead sea turtle (Caretta caretta) has been suspected to be a reservoir host. The objectives of this study were: (1) to determine prevalence of Bartonella infection in small mammals and their infested arthropods; (2) to explore the potential transmission from mammals to reptiles through common vectors. The study area is located in the forest of Linnei town, Yunlin County, where populations of turtles and rodents are prevalent and co-exist. The total of 52 spiny country rats (Niviventer coninga) and 80 yellow margin turtles (Cyclemys flavomarginata) were humanely captured for this investigation. Through direct blood culture, it was identified that the prevalence of Bartonella bacteremia in the animals tested was 59.6% (31/52). Among rodents, after further analysis of epidemiological data, the results indicated that the age factor was a significant determinant of Bartonella bacteremia (p<0.05). The prevalence in the adult rodents was significant higher than that in the juvenile rodents (69.4% v.s 37.5%). After sequencing analysis of the gltA gene for these isolates, B. coopersplainsensis and B. queenslandensis were identified. B. coopersplansensis was thus to be the first report of isolation in Taiwan, and 3.8% (2/51) rodents were show to be co-infected with these two species of Bartonella.
The ectoparasites infested on spiny country rats were found to be mites and hard ticks, Ixodes granulatus. A total of 81 tick DNA extracts were tested using PCR of the gltA gene for Bartonella. It was found that 6.2% (5/81) samples of ticks were PCR-positive; the sequences were identified to be B. queenslandensis. As the two PCR-positive tick samples were collected from the same rodent, a total of 4 rodents were parasitized by PCR positive ticks, with a prevalence of 7.69% (4/52). The prevalence of PCR-positive ticks in Bartonella bacteremia rodents was 6.4% (2/31), and was 9.5% (2/21) in no-bacteremia rodents. No significant association was found between animals with bacteremia and animals parasitied by PCR positive ticks.
Furthermore, none of the turtles were cultured or PCR positive for Bartonella. Ticks infested on the turtles were all Amblyomma geoemydae. Therefore, there was no identical tick species identified between small mammals and reptiles in the study area.
In conclusion, high prevalence of Bartonella bacteremia was identified in 31 Niviventer coninga in Yunlin County. This is the first report of Bartonella isolated in this rodent species. Although molecular data suggest that hard ticks could be potential vectors for Bartonella transmission in these animals, further biological transmission model needs to be established to show that they are competent vectors. Finally, no cross-transmission of Bartonella were found between small mammals and reptiles.
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