• Animal cells and systems
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• v.1 no.1
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• pp.53-61
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• 1997

Seasonal variation of the population structure and the reproductive pattern of the Korean striped field mouse, Apodemus agrarius, were investigated. High capture ratios in juveniles, young adult, and old adult mice were found during the period from October to November, from November to March, and from May to September, respectively, and extremely low capture ratios of old adults during the period from November to February were characteristic. It seemed that the young adults that survived during the winter might become older by summer and have been counted as the old adults. The breeding in the mice began earlier in males (from mid February or early March to late October) than in females (from mid March to late October), having a peak in August and September, and both the male and female mice weighing more than 20 g generally reached sexual maturation in general. In the breeding season, both young and old adult males had large testes with enlarged seminiferous tubules filled with numerous germ and Sertoli cells, and expanded caudal epididymides with a vast number of spermatozoa; the females had many Graafian follicles and corpora lutea in large ovaries, and developed uterine glands in the thick endometria. The lower ratios of the testis weight to the body weight in July and August in 1994 compared to 1995 seemed due to the extreme drought and considerably higher temperature in 1994, but the decrease in the ratio in mid-summer, only in the old mice, in both years might be explained partially by aging.

• Biomedical Science Letters
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• v.17 no.4
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• pp.367-370
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• 2011

Studies on the relative abundance of potential vectors of scrub typhus was conducted from April to October 2009 at the Jangseong of Jeonnam Province, Korea. Among the total 62 field rodents collected by the Sherman collapsible traps, 56 rodents were $Apodemus$ $agrarius$ (90.3%), 4 were $Crocidura$ $lasiura$ (6.4%) and 2 were $Cricetulus$ $triton$ $nester$ (3.2%). Out of the 62 field rodents, 39 were parasitized by chiggers, showing 62.9% of the infestation rate and 80.0 of the chigger index. Chigger index of $A.$ $agrarius$ and $C.$ $triton$ $nester$ were 79.9, 82.0, respectively. But chigger mite was not collected from $C.$ $lasiura$. From the trapped field rodents, 3,120 chiggers were collected and identified with 6 species of 2 genera. $Leptotrombidium$ $scutellare$, the vector species of tsutsugamushi disease, was the dominant species, showing 2,276 chiggers (72.9%). $L.$ $pallidum$ was the second dominant species showing 346 chiggers (11.0%). The distribution of chigger mites was showed the different dominant species according to seasons. $L.$ $pallidum$ was the predominant chigger collected in April (34.8%), May (77.8%) and Jun (39.3%), whereas $L.$ $scutellare$ was the predominant chigger collected in September (78.78%) and October (76.8%).

• Journal of Radiation Protection and Research
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• v.40 no.3
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• pp.168-173
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• 2015

The present investigation was planned to estimate potential possibility of striped field mice, Apodemus agrarius coreae (A. a. coreae), as a biological dosimeter in radio-environmental ecology. We bred captured wild A. a. coreae at laboratory and classified taxonomically based on external, cranial and tooth characters. Organ weights and splenocytic apoptosis were observed in order to establish a basic data on radiation biology of A. a. coreae (male, 40 weeks old). The biological effects was observed at 24hrs following irradiation (doses : 0, 0.5, 1, 2 Gy, dose rate : $0.8Gymin^{-1}$, $^{137}Cs$). Only thymus weights was significantly decreased. Splenocytic apoptosis was increased after irradiation. But splenocytic apoptosis was decreased in 0.5 Gy ${\gamma}$-irradiated mice compared to those of 0, 1, 2 Gy (P < 0.05). These data suggested that events in thymus and spleen of Korean dark-striped field mice, A. a. coreae THOMAS, could be a potential radio-biological indicator in human environments.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.241-249
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• 2004

As a part of epidemiologic investigation of tsutsugamushi disease, the wild rodents which were captured in Gyeongnam area were diagnosed with indirect immunofluorescent antibody assay (IFA) and Polymerase Chain Reaction (PCR) to find if they have an antibody against Orientia tsutsugamushi. The conclusion was drawn as followings. (1) The captured 58 wild rodents showed that the subspecies distribution of Apodemus agrarius was 86.2%, Microtus fortis was 8.6% and Crocidura lasiura was 5.2%. (2) The antibody positive rate of O. tsutsugamushi Gilliam, Karp, Karto and Boryong by IFA method was 32.0% in Apodemus agrarius among 50 wild rodents and 40.0% in Microtus fortis among 5 wild rodents, respectively. It was negative in the case of all the 3 Crocidura lasiura. (3) The antibody titers on Apodemus agrarius, Microtus fortis and Crocidura lasiura against Gilliam, Karp, Karto and Boryong were measured between 1:20 and 1:640. The antibody titer against each antigen was in the order Boryong>Gilliam>Karp. (4) O. tsutsugamushi was detected from the blood, spleen and kidney from the artificially infected mice by IFA and PCR. IFA showed the positive response between 3 and 18 days after inoculation. On the other hand, positive response was found from all the samples by PCR. (5) From PCR of the genomic DNA extracted from the blood, spleen and kidney samples of the captured wild rodents, Boryong-specific amplification product with size of 210 bp, which is particular in Boryong, was detected from spleen and kidney samples, but not detected in the blood. (6) Boryong-specific amplification product was detected from spleen and kidney samples which were obtained at 3, 6, 12, 18 and 24 days after the infection with Boryong. But, it wasn't detected from the uninfected samples. (7) From PCR of spleen and kidney samples of the captured wild rodents, it was found that positive rate of O. tsutsugamushi in Apodemus agrarius and Microtus fortis were 25.0% (4/16) and 20.0% (1/5), respectively. From the above results, it can be concluded that Apodemus agrarius resided in Gyeongnam area carried O. tsutsugamushi and PCR method might be a simple, precise, rapid and useful diagnostic tool than IFA for the diagnosis of O. tsutsugamushi.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.1
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• pp.25-32
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• 2006

This study examined the possibility of using dark-striped field mice as a biological indicator for the environmental radio-surveillance. For this study, dark-striped field mice were caught from five areas of Kyonggi, Kyongsang, Chungchong and Cholla provinces. The external morphological characteristics and isoenzymic types of dark-striped field mice were studied after they were captured. Among the external morphological characteristics, the dark-brown coat, dark back stripe, head-to-tail length, tail length, and ear length matched the taxonomical characteristics of dark-striped field mice. The analyses on L-lactate dehydrogenase, aspartate aminotransferase, and malate dehydrogenese revealed that one species of dark-striped field mice, called Apodemus agrarius, was inhabitated throughout a wide range of Korea. On the other hand, the frequency of micronuclei in peripheral polychromatic erythrocytes to survived mice after irradiation also analyzed. The LD50/30 of A. cgrarius and ICR mice were approximately 5 Gy and 7.9Gy, respectively. The results of the study reveal that wild A. asrarius have a high potential as a biological monitoring system to determine the impact of radiation in areas such as those within the vicinity of nuclear power plants.

• Parasites, Hosts and Diseases
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• v.48 no.3
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• pp.237-243
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• 2010

Comprehensive quarterly serosurveillance on scrub typhus in small mammals collected from military training sites located near the Demilitarized Zone (DMZ), northern Gyeonggi-do (Province), ROK was conducted to determine the potential rodent-borne and associated ectoparasite disease risks to military personnel. A total of 1,196 rodents and insectivores representing 8 species, Apodemus agrarius (87.3%, n = 1,044), Mus musculus (5.4%, n = 65), Crocidura lasiura (3.3%, n = 40), Microtus fortis (2.6%, n = 31), Micromys minutus (0.3%, n = 4), Tscherskia triton (0.3%, n = 4), Rattus norvegicus (0.3%, n = 4), and Myodes regulus (0.3%, n = 4) were assayed for the presence of antibodies to Orientia tsutsugamushi. O. tsutsugamushi antibodies were detected in 6 of 8 species and seroprevalence determined; A. agrarius (45.6%), M. musculus (23.1%), M. fortis (48.4%), M. minutus (50.0%), T. triton (50.0%), and R. norvegicus (25.0%). A total of 31,184 chigger mites collected from 508 rodents and insectivores were slide-mounted and 10 species belonging to 4 genera were identified. Leptotrombidium pallidum (53.4%) was the most frequently collected, followed by L. pal pale (15.7%), Neotrombicula tam/yai (14.3%), L. orientate (10.7%), L. zetum (3.1%), Walchia fragilis (2.1%), and L. gemiticutum (0.8%), while the remaining 3 species, L subintennedium, N. gardellai, and Euschoengastia koreaensis were rarely observed (prevalence < 10%). In contrast to previous surveys, higher chigger indices of the primary scrub typhus vectors, L. pallidum (165.4), L. orientale (45.0), and L. palpate (21.4), were observed during the spring season.

• Journal of Ecology and Environment
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• v.41 no.3
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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.

• Parasites, Hosts and Diseases
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• v.27 no.2
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• pp.141-144
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• 1989

During October-December 1987, chigger mites infested on the striped field mice (Apodemus agrarius cereae) collected at Pochun-gun, Gyeonggi Province and Chinhae city, Kyongnam Province were identified. . 1. Of 171 back-striped mice collected, chigger mites wire found from 58 mice, showing 33.9% of infestation rate. 2. Total 865 chigger mites collected were classified into seven species; Leptotrombidium pallidum (4.3%), L. palpate(23.0%), L. orienpalis(20.2%), L. xetum(19.0%), Neotrombicula tamiyai(32.9%), JV. japonica(0.25%) and Euschongastia koreaensis(0.3%). Though the most dominant species in number was N. tamiyai(32.9% of the total), this species was collected at very limited locality and for a short period. Therefore, most common species in Korea seems to be L. palpale which was found at all localities throughout the whole survey period. L. pallidum which is known as the vector species of tsutsugamushi disease in Korea was collected in a very low number(4.3% of the total chiggers collected). 3. The number of chigger mites infested on a host animal showed great variations from one chigger up to 207 chiggers. The present study has shown that there may be other Leptotrombidium species mite(s) for the vector and host of tsutsugamushi disease in Korea.

• Korean Journal of Veterinary Service
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• v.26 no.3
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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.

• Journal of Korean Society of Forest Science
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• v.99 no.4
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• pp.553-558
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• 2010

This study was conducted to clarify the differences in rodents population densities between natural restored and red pine silvicultured forests after forest fire in Samcheok, Gangwon Province, Korea from March to December 2008. One ha size of 3 study plots were set up in each natural restored and silvicultured stand. We trapped the small rodents during 4 consecutive nights every 2 months in each stand. Understory coverage and number of shrub stems were higher in silvicultured stand than in natural restored stand. Coverage of overstory, suboverstory and midstory, number of tree stem, woody seedling stems and dead wood, and amount of coarse woody debris were higher in natural restored stand than in silvicultured stand. Six hundred eighty eight individuals of four species, such as Apodemus agrarius, A. peninsulae, Eothenomys regulus and Tamias sibiricus were captured in our study. Number of captured small rodents were higher in natural restored stand than in silvicultured stand. Also, species compositions were differed in both stands. The captured number of A. agrarius and A. peninsulae were most highest in April and December. E. regulus were shown higher number of captured in April and June, and T. sibiricus were in June and October. Removal of coarse woody debris and silvicultural practice would not be good for the inhabitation of small rodents. For the conservation of small rodents diversity, management of understory and canopy would be needed in forest fired area.