Population density of chigger mites, the vector of tsutsugamushi disease in Chollanam-do, Korea

Abstract

The geographical distribution and population density of rodents and chigger mites at six localities of Chollanam-do were investigated from October to December in 1993. Among total 142 field rodents collected by the modified Chemla wooden traps, 131 rodents were Apodemus agrarius (92.3%) and 11 were Crocidura lasiura (7.7%). Out of 142 field rodents, 92 were parasitized by chiggers, showing 69.0% of the infestation rate and 74.2 of the chigger index. Infestation rate and chigger index of A. agrarius and C. lasiura were 73.3%, 80.4 and 18.2%, 0.5, respectively. From the trapped field rodents, 10,532 chiggers were collected and identified with 11 species of 4 genera. Leptotrombidium pallidum, the vector species of tsutsugamushi disease, was the dominant species, showing 8,038 chiggers (76.3%). L. scutellare was the second dominant species showing 1,359 chiggers (12.9%). The distribution of chigger mites was clearly localized by the species, showing the different dominant species according to localities. The predominant species was L. scutellare (100%) in Changhung-gun, L. scutellare (41.5%) in Posong-gun, L. pallidum (88.8%) in Hwasun-gun, L. pallidum (59.2%) in Koksong-gun, L. zetum (77.3%) in Hampyong-gun, and L. palpale (63.4%) in Tamyang-gun. Regarding to the geographical distribution of chigger population density, the infestation rate and chigger index was most high in Hwasun-gun as 62.4% and 216.2 respectively, and next high in Koksong-gun as 22.4% and 77.7% respectively.

Seasonal prevalence and species composition of mosquitoes and chigger mites collected from Daegu, Gunwi and Sangju in South Korea, 2014

“…Since it requires animal tissue fluids to grow to adulthood, chigger mites are mostly parasitic on wild rodents. Apodemus agrarius is the most prevalent species in South Korea (Song et al 1996, Ree et al 1991b, which is in agreement with the present study results. Specifically, Apodemus agrarius was the dominant species in Gunwi, while Apodemus agrarius and Crocidura suaveolens were similarly common in Sangju.…”

“…Therefore, it is thought that Mus musculus 1 0 0 0 0 scrub typhus is one of the most common diseases spread via chigger mites of wild rodents. Apodemus agrarius had 81.8% and 80% chigger-mite infection rates in Gunwi and Sangju, respectively, which are similar to the results of previous studies by Ree et al (1991c) and Song et al (1996). Crocidura suaveolens had a similar infection rate as well.…”

“…Crocidura suaveolens had a similar infection rate as well. On the other hand, the chigger index was 70.8 and 52.0 in Gunwi and Sangju, respectively; these results were also similar to the numbers of chigger mites reported in the studies of Ree et al (1991c) and Song et al (1996) of 43.6 and 80.4, respectively. In these previous studies, in agreement with our results, Crocidura suaveolens had a low chigger index.…”

“…These two species have different distribution characteristics. In the studies of Shim et al (1989), Ree et al (1991c), Lee, et al (1993aLee, et al ( , 1993b, and Song et al (1996), Leptotrombidium pallidum was the dominant species in wild rodents. In contrast, Lee et al (1993a), Ree et al (1992), and Ree et al (1995) reported that Leptotrombidium scutellare was a dominant species.…”

“…In contrast, Lee et al (1993a), Ree et al (1992), and Ree et al (1995) reported that Leptotrombidium scutellare was a dominant species. Song et al (1996) addressed this discrepancy by showing that Leptotrombidium pallidum has a higher population density in the north while Leptotrombidium scutellare is more common in the south. In central regions, these two species coexist, although Leptotrombidium scutellare is less common (Lee, Ree, et al 1993a, Ree et al 1995.…”