• Parasites, Hosts and Diseases
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• 제52권2호
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• pp.225-229
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• 2014

A total of 9,281 larval chigger mites were collected from small mammals captured at Hwaseong-gun, Gyeonggi-do (Province) (2,754 mites from 30 small mammals), Asan city, Chungcheongnam-do (3,358 mites from 48 mammals), and Jangseong-gun, Jeollanam-do (3,169 for 62 mammals) from April-November 2009 in the Republic of Korea (= Korea) and were identified to species. Leptotrombidium pallidum was the predominant species in Hwaseong (95.8%) and Asan (61.2%), while Leptotrombidium scutellare was the predominant species collected from Jangseong (80.1%). Overall, larval chigger mite indices decreased from April (27.3) to June (4.9), then increased in September (95.2) and to a high level in November (169.3). These data suggest that L. pallidum and L. scutellare are the primary vectors of scrub typhus throughout their range in Korea. While other species of larval chigger mites were also collected with some implications in the transmission of Orientia tsutsugamushi, they only accounted for 11.2% of all larval chigger mites collected from small mammals.

• Parasites, Hosts and Diseases
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• 제61권3호
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• pp.263-271
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• 2023

The present study aimed to survey the prevalence of chigger mites and Orientia tsutsugamushi (O. tsutsugamushi) infection in the northern regions of Gangwon-do, Korea. From early February to early June 2015, a total of 17,050 chiggers were collected from striped field mice, Apodemus agrarius, in Cheorwon-gun, Hwacheon-gun, Yanggu-gun, and Goseong-gun, which are well-known endemic areas of scrub typhus in Korea. The chiggers were analyzed using molecular genomic methods, as previously described. Among the 7,964 identified chiggers, the predominant species was Leptotrombidium pallidum (76.9%), followed by L. zetum (16.4%), L. orientale (4.3%), L. palpale (0.3%), L. tectum (0.2%), and Neotrombicula tamiyai (1.8%). The chigger index (CI) was highest in Hwacheon (115.58), followed by Cheorwon (97.02), Yanggu (76.88), and Goseong (54.68). Out of the 79 O. tsutsugamushi-positive chigger pools, 67 (84.8%) were identified as the Boryong strain, 10 (12.7%) as the Youngworl strain, and only 2 were the Jecheon strain. Based on the high infestation of chiggers in striped field rodents and the high rate of O. tsutsugamushi infection in chigger mites, Hwacheon-gun and Cheorwon-gun are presumed to be high-risk areas for scrub typhus. Furthermore, L. pallidum, a major vector of scrub typhus, and the dominant O. tsutsugamushi serotype, the Boryong strain, were found in the northern regions of Gangwon-do, Korea.

• Journal of Ecology and Environment
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• 제41권3호
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• pp.107-113
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• 2017

Background: As the habitat changes in Korea due to climate change, the emergence of disease-mediated vectors is increasing rapidly. Thus for the surveillance of mosquito- and chigger mite-borne disease, their seasonal prevalence and species composition were investigated at seven locations in Daegu, Gunwi and Sangju. Methods: Mosquitoes were collected twice every month from five collection sites using a black light and BG sentinel traps in Daegu and Gunwi from April through November. Chigger mites were investigated twice per month from wild rodents caught with Sherman live traps in Gunwi and Sangju from April through May and September through November. Results: A total of 2,361 female mosquitoes were collected. Cowshed (626 individuals, Trap index (TI) 44.7) and Kyungpook National University campus (846 individuals, TI 60.4) in Daegu had the highest number of mosquitoes in the black light and BG sentinel trap, respectively. The mosquitoes were collected more by BG sentinel trap than the black light trap. Nine mosquito species were trapped, and the Culex pipiens complex was the most commonly mosquito (1,397 individuals, 59.2%), followed by Anopheles sinensis (554 individuals, 23.5%). Anopheles sinensis (531 individuals, 51.9%) and Culex pipiens complex (1,142 individuals, 85.4%) were the most mosquitoes from black light and BG sentinel trap, respectively. In terms of seasonal prevalence, the highest abundance was in July, with 824 individuals collected. In chigger mites, eighty-one wild rodents of five species that are hosts of chigger mites were collected; among them, 53 and 25 individuals of Apodemus agrarius and Crocidura suaveolens, respectively were trapped. Leptotrombidium pallidum was a dominant species, with 2,467 individuals collected (67.8%). Conclusions: The mosquito was the dominant species in Culex pipiens complex and the highest in July and August. Apodemus agrarius was most abundant in wild rats and Leptotrombidium pallidum was dominant in the collected chigger mites.

• 한국동물위생학회지
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• 제26권3호
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• pp.203-214
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• 2003

Scrub typhus and murine typhus are common endemic febrile illness in the fall in Korea. Scrub typhus is caused by Orientia tsutsugomushi, murine typhus is caused by Rickettsia typhi. Trombiculid mites are known as both the vector and the reservoir host of O tsutsugamushi, the mites which transmit O tsutsugomushi have been reported to be Leptotrombidium pallidum and L scutellare. The author carried out an epidemiological study of scrub typhus and murine typhus in Kyodong-Myeon, Kanghwa-Gun, Incheon in relation to the residents and the host rodents, such as their distribution, seroepidemiology, and population density of chigger mites. 1. Out of 900 residents, 33(3.7%) showed positive reaction to O tsutsugamushi, 24(2.7%) to R typhi. 2. In the seropositives to O tsutsugamushi or R typhi, between the sixties and the seventies of the age were dominant. 3. In the seropositives to O tsutsugamushi serotypically Gilliam was dominant. 4. Among the total 42 field rodents trapped by the sherman traps, 18 rodents were Apodemus agrarius(42.9%), 13 rodents were Crocidura lasiura(31.0%), 5 rodents were Musmusculus(11.9%), 2 rodents(4.8%) were Crocidura suaveolens, Rattus norvegicus, Tscherskia triton, respectively. 5. Out of 42 field rodents, 25 were parasitized by 4,419 chigger mites, showing 59.5% of the infestation rate and 98.8 of the chigger index. L pallidum parasitized in A agrarius, C lasiura, M musculus, R norvegicus and T triton, and L scutellare parasitized only C lasiura. 6. Antibodies in the sera of field rodents against O tsutsugamushi and R typhi were investigated by indirect immunofluorescent antibody technique. Positive rate of antibody against O tsutsugamushi were 11.9(5 of 42) and all of the positive is A agrarius. Antibody against R typhi was not detected. These results might provide the basic information for the management of scrub typhus and murine typhus in Kyodong-myeon, where the epidemiological studies on scrub typhus and murine typhus was not carried out enough.

• Parasites, Hosts and Diseases
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• 제29권2호
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• pp.181-188
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• 1991

최근 전국적으로 높은 이환률을 보이고 있는 쭈쭈가무시병에 대한 방제 대책이 시급한 현실에 반해 본 질병에 대한 연구가 거의 이루어져 있지 않기 때문에 저자들은 1989년 7월부터 1950년 9월까지 9개 지역에서 숙주동물에 대한 역학적 조사를 실시하여 다음과 같은 결과를 얻었다. 1. 모두 794개의 Sherman식 live trap을 설치하여 111마리의 들쥐로 포획하여 trapping rate가 평균 14.0%이었다. 계절별로 보면 봄, 여름, 가을에 각각 11.7%, 11.2%, 12.8%이었고 겨울에는 24.0%로 가장 높았다. 포획한 111마리 중 103마리가 등줄쥐 (Apodemus agrarius)로 92.8%를 차지하여 우점종이었고, 땃쥐 (Crocidura Zasiura)가 7마리로 6.3%이었으며. 갈밭쥐 (Microtns fortis)는 1마리가 채집되어 0.9%이었다. 들쥐의 털진드기 기생률을 보면, 등줄쥐의 경우 103마리 중 84마리로 81.6%이었고, 땃쥐의 경우 7마리 중 2마리로 28.6%이었다. Chigger index는 등줄쥐의 경우 43.0개체였고 만취는 0.9개체였다. 2. 등줄쥐 혈청의 Rickettsia tsutsugamushi 항체 양성률을 보면 평균 41.8%이었는데, 조사 지역에 따라 큰 차이가 있어 고양군 도래 5리 54.9%, 고양군 고양리 20%, 고양군 원홍 2리 28.6%, 청인군 시목리 40%이었고 고양군 행신 1리, 파주군 광탄 3리 와 예산군 덕산리에서는 모두 음성이었다. 땃쥐의 경우는 7마리 모두 음성이었다. 동일 장소에서의 등줄쥐 혈청의 R. tsutsugamushi 항체 양성률의 계절적 변동은 11월부터 3웜까지는 평균 75.8%이었는데 4일에는 30.3%로 감소하였고 5월부터 8월에 걸쳐 평균 13.3%로 크게 감소하였다. 조사한 모든 양성 혈청의 항체가를 보면 Karp, Gilliam및 Kato 주에 대해 서로 교차반응을 나타냈는데 Karp주와 Kato 주 간에 보다 강한 교차반응을 보였다. 3. 총 94마리의 등줄쥐로부터 마우스 복강접종법과 간접 면역형광법으로 R. tsutsugamushl치 분리를 시도한 바 3마리에서 분리되어 감염률은 3.2%이었다.

• Parasites, Hosts and Diseases
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• 제33권1호
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• pp.27-36
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• 1995

쭈쭈가무시병 환자의 유병률이 가장 높은 남해안 연안지역과 유병률이 낮은 동해안 연안 지역에서 매개 진드기 및 들쥐와 연관되는 제반 역학적 비교조사를 1993년 10월에 실시하였다 채집된 6 종의 들쥐(187개체) 중 등줄쥐(Apodemugrwin)가 양지역에서 모두 절대 우점종이었고 개체군 밀도에 있어서도 차이가 없었다(트랩 채집률 각각 20.4%, 19.4%). 국내 매개종으로 확인된 Leptotrombidiumpalldum과 L. sueuare는 모두 채집된 6종의 들쥐중 등줄쥐에 주로 기생하였는데, 두당 각각 59마리와 69마리가 기생하고 있었다 등줄쥐의 Rickettsia tsutsugamushi, 병원체에 대한 항체 양성률은 남해안 43.2% 동해안 63.6%로 동해안 지역에서 약간 높게 나타나 환자 발생과는 다른 양상을 보였다. 지역에 관계없이 등줄쥐의 감염률(항체 양성률)과 매개종인 L. suteuure와 L. poninw의 개체군 밀도간에 높은 상관관계를 보였다(r : 0.87). 이와같은 사실은 들쥐에 대한 양종의 매개 효율성(vectorefacacy)이 똑같이 높다는 것을 의미한다. 양지역간의 가장 중요한 역학적 차이는 매개종으로. 남해안 지역에서는 L. sueuore가 절대 우점종(74.9%)인 반면 에 동해안 지역에서는 L. pallidum이 절대 우점종(60.4%)이었다. 두종의 개체군 밀도에는 큰 차이가 없었다. 조사지역이 불충분하여 확실하게 결론지을 수는 없지만 L. sueuqre의 개체군 밀도가 높을수록 환자 유병률도 높게 나타나 L. sueuare가 인체에 대한 매개효율성(vectorefacacy)이 L. pallidum보다 월등하게 높은 중요한 매개종이라 생각된다.