Epidemiological Characteristics of Rodents and Chiggers with Orientia Tsutsugamushi in the Republic of Korea

Abstract

A survey of rodents and chiggers associated with Orientia tsutsugamushi was conducted in a rural region of the Republic of Korea (Korea) between 2014 and 2018. Overall Apodemus agrarius 15.2% had the highest seropisitive for O. tsutsugamushi, followed by Myodes regulus 11.4%. Monthly risk factors using logistic regression analysis were not associated with O. tsutsugamushi infections in rodents. The overall prevalence rate of O. tsutsugamushi among chiggers was 0.3%. The chigger (Leptotrombidium scutellare) and monthly (October) risk factors were associated with O. tsutsugamushi human infections (P<0.05). Orientia tsutsugamushi infections are endemic in rodents in Korea and people, for example, soldiers who are active outdoors, must employ preventive measures, especially during October (P<0.05). When there are many reports of O. tsutsugamushi infections in Korea. The Boryong strain 85.7% (2/14) was the most common strain detected in chiggers, followed by the Shimokoshi 7.1% (1/14) and Karp 7.1% strains.

Orientia tsutsugamushi Infection in Wild Small Mammals in Western Yunnan Province, China

“…The Gilliam genotype was the most common strain at a rate of 35.6%, followed by the Karp and TA763 strains. This result was consistent within Guangdong, which detected that the Karp , Gilliam, and TA763 strains could be identified in small mammals, but differs from the results reported from Korea, which showed that the Boryong strain (85.7%) was the most common strain in small mammals [ 6 , 30 ]. It is known that Karp , Gilliam , and Kato were the predominant strains of Ot in Yunnan [ 18 ].…”

Nationwide Incidence of Chigger Mite Populations and Molecular Detection of Orientia tsutsugamushi in the Republic of Korea, 2020

“…We found that the MIR of O. tsutsugamushi was 0.1% in engorged chigger mites from rodents. Other studies used engorged chigger mites from rodents to identify the prevalence of O. tsutsugamushi infection in the Republic of Korea, such as those on chigger mites (MIR, 0.6%) [ 10 ], L. scutellare (0.6%), L. palpale (0.9%), and L. orientale (0.1%) [ 24 ], L. scutellare (0.6%) and L. orientale (0.4%) [ 25 ], L. scutellare (11.3%), L. pallidum (9.5), L. palpale (1.1%), L. orientale (11.4%), and E. koreaensis (11.8%) [ 26 ], L. scutellare (0.3%) and L. orientale (0.2%) [ 27 ], and L. scutellare (3.7%), L. pallidum (1.5), L. palpale (5.3%), L. orientale (3.6%), N. japonica (4.3%), and E. koreaensis (1.9%) [ 23 ].…”

“…Among these species, L. scutellare (35.3%) and L. palpale (19.9%) were the most predominant in this study. However, in other studies, different proportions of chigger mite species were reported in other regions and seasons in the Republic of Korea, including the following: (1) L. pallidum (52.6%), L. scutellare (27.1%), and L. palpale (8.2%) during spring and autumn between 2005 and 2007 throughout the country [ 9 ]; (2) L. pallidum (43.5%), L. orientale (18.9%), and L. scutellare (18.1%) over the entire year between 2006 and 2007 in the eastern and southern areas [ 10 ]; (3) L. pallidum (74.9%), L. scutellare (18.9%), and L. palpale (2.7%) from October to November in 2006 throughout the country [ 7 ]; (4) L. scutellare (44.4%), L. orientale (22.7%), and L. pallidum (15.8%) during the entire year between 2014 and 2018 in the southwestern region of the Republic of Korea [ 24 ]; (5) L. pallidum (53.9%), L. orientale (13.2%), and L. scutellare (9.5%) in April and November in 2019 throughout the country [ 5 ]. In this study, we identified only chigger mite species from sticky traps during autumn, and the incidence of L. palpale (19.9%) was higher than that of L. pallidum (11.5%).…”

Geographical Distribution and Epidemiologic Factors of Chigger Mites on Apodemus agrarius during Autumn in Korea

“…The chigger indices and seropositive rates of scrub typhus in wild rodents were highest in autumn. Because trombiculid mites lay eggs in the summer in Korea, the incidence of scrub typhus in humans peaks in the autumn months [3,[7][8][9]. The annual number of scrub typhus cases had increased to 10,365 in 2013.…”