Intestinal nematodes from small mammals captured near the demilitarized zone, Gyeonggi province, Republic of Korea

A total of 1,708 small mammals (1,617 rodents and 91 soricomorphs), including Apodemus agrarius (n = 1,400), Microtus fortis (167), Crocidura lasiura (91), Mus musculus (32), Myodes (= Eothenomys) regulus (9), Micromys minutus (6), and Tscherskia (= Cricetulus) triton (3), were live-trapped at US/Republic of Korea (ROK) military training sites near the demilitarized zone (DMZ) of Paju, Pocheon, and Yeoncheon, Gyeonggi Province from December 2004 to December 2009. Small mammals were examined for their intestinal nematodes by necropsy. A total of 1,617 rodents (100%) and 91 (100%) soricomorphs were infected with at least 1 nematode species, including Nippostrongylus brasiliensis, Heligmosomoides polygyrus, Syphacia obvelata, Heterakis spumosa, Protospirura muris, Capillaria spp., Trichuris muris, Rictularia affinis, and an unidentified species. N. brasiliensis was the most common species infecting small mammals (1,060; 62.1%) followed by H. polygyrus (617; 36.1%), S. obvelata (370; 21.7%), H. spumosa (314; 18.4%), P. muris (123; 7.2%), and Capillaria spp. (59; 3.5%). Low infection rates (0.1-0.8%) were observed for T. muris, R. affinis, and an unidentified species. The number of recovered worms was highest for N. brasiliensis (21,623 worms; mean 20.4 worms/infected specimen) followed by S. obvelata (9,235; 25.0 worms), H. polygyrus (4,122; 6.7 worms), and H. spumosa (1,160; 3.7 worms). A. agrarius demonstrated the highest prevalence for N. brasiliensis (70.9%), followed by M. minutus (50.0%), T. triton (33.3%), M. fortis (28.1%), M. musculus (15.6%), C. lasiura (13.2%), and M. regulus (0%). This is the first report of nematode infections in small mammals captured near the DMZ in ROK.

Ecological surveillance of small mammals at Firing Points 10 and 60, Gyeonggi Province, Republic of Korea, 2001-2005

Throughout Korea, small mammals are hosts to a number of disease-causing agents that pose a health threat to U.S. and Korean military forces while they conduct field-training exercises. A seasonal rodent-borne disease surveillance program was established at two firing points (FP), FP-10, and FP-60, and conducted over five years from 2001 through 2005 in response to hantavirus cases among U.S. soldiers. The ecology of these sites consisted primarily of tall grasses associated with semi-permanent and temporary water sources (drainage ditches and a small stream) and dry-land agriculture farming. Eight species of rodents and one species of insectivore were collected, including Apodemus agrarius, Micromys minutus, Mus musculus, Rattus norvegicus, Tscherskia triton, Microtus fortis, Myodes regulus, and Crocidura lasiura. The striped field mouse, A. agrarius, (primary reservoir for Hantaan virus, the causative agent of Korean hemorrhagic fever), was the most frequently collected, representing 90.6% of the 1,288 small mammals captured at both sites. Reported herein are the ecological parameters, seasonal population densities, and seasonal population characteristics associated with small mammals collected at two military training sites in the Republic of Korea.

Seroepidemiological Survey of Rodents Collected at a U.S. Military Installation, Yongsan Garrison, Seoul, Republic of Korea

A seroepidemiological study of selected rodent-borne diseases (hantavirus [Seoul [SEO] virus], scrub typhus [Orientia tsutsugamushi], murine typhus [Rickettsia typhi], and leptospirosis [Leptospira interrogans]), as part of the U.S. military rodent surveillance and control program, was conducted from 2001 through 2005 at Yongsan Garrison, Seoul, Republic of Korea. Rodents were collected to determine the prevalence of rodent-borne diseases at a U.S. military installation in an urban environment. A total of 1,750 rodents representing three species was collected by using baited live traps (Tomahawk), glue boards, and poison baits (dead rodents observed but not assayed). The Norway rat, Rattus norvegicus (99.8%), accounted for nearly all of the rodents captured/observed. Only three roof rats, Rattus rattus (0.2%), and one house mouse, Mus musculus (<0.1%), were collected. R. norvegicus rats were the only rodents that were serologically positive for SEO virus (9.6%), scrub typhus (2.8%), murine typhus (3.8%), and leptospirosis (4.6%). One of six rodents that were positive for SEO virus by immunofluorescent antibody test was positive for SEO virus antigen by reverse transcriptase-polymerase chain reaction. Infection rates for SEO virus, scrub typhus, murine typhus, and leptospirosis varied annually. Rodents were captured from 228 (20.7%) of 1,104 total buildings in Yongsan Garrison. The Yongsan commissary had the highest annual infestation rate (22 rodents per year), followed by Commisky's Club (18 rodents per year). Annual infestation rates were high for food service facilities, which often store perishable food products outdoors for short periods of time, attracting rodent populations; refuse from these facilities provides harborage and food for rodents. The effect of rodent populations outside the boundary of Yongsan Garrison was not determined.

Tick-borne rickettsial pathogens in ticks and small mammals in Korea

In order to investigate the prevalence of tick-borne infectious agents among ticks, ticks comprising five species from two genera (Hemaphysalis spp. and Ixodes spp.) were screened using molecular techniques. Ticks (3,135) were collected from small wild-caught mammals or by dragging/flagging in the Republic of Korea (ROK) and were pooled into a total of 1,638 samples (1 to 27 ticks per pool). From the 1,638 tick samples, species-specific fragments of Anaplasma phagocytophilum (1 sample), Anaplasma platys (52 samples), Ehrlichia chaffeensis (29 samples), Ehrlichia ewingii (2 samples), Ehrlichia canis (18 samples), and Rickettsia rickettsii (28 samples) were amplified by PCR assay. Twenty-one pooled and individual tick samples had mixed infections of two (15 samples) or three (6 samples) pathogens. In addition, 424 spleen samples from small captured mammals (389 rodents, 33 insectivores, and 2 weasels) were screened for selected zoonotic pathogens. Species-specific DNA fragments of A. phagocytophilum (110 samples), A. platys (68 samples), E. chaffeensis (8 samples), E. ewingii (26 samples), E. canis (51 samples), and Rickettsia sp. (22 samples) were amplified by PCR assay. One hundred thirty small mammals had single infections, while 4, 14, and 21 striped field mice (Apodemus agrarius) had mixed infections of four, three, and two pathogens, respectively. Phylogenetic analysis based on nucleotide sequence comparison also revealed that Korean strains of E. chaffeensis clustered closely with those from China and the United States, while the Rickettsia (rOmpA) sequences clustered within a clade together with a Chinese strain. These results suggest that these agents should be considered in differential diagnosis while examining cases of acute febrile illnesses in humans as well as animals in the ROK.

In vivo characterization of the integrin beta3 as a receptor for Hantaan virus cellular entry

Binding of viruses to cell surface molecules is an essential step in viral infection. In vitro studies suggested that the alpha(v)beta(3) integrin receptor is the epithelial cell receptor for Hantaan virus (HTNV). Whether beta(3) is in vivo the only or central cellular receptor for HTNV infection is not known. To investigate the role of beta(3) integrin for cellular entry of HTNV, we established an HTNV infection model in newborn murine pups. Infected pups died at an average age of 14.2 +/- 1.1 days with high levels of viral antigen detected in their brain, lung, and kidney. Pre-injection of blocking monoclonal antibodies (mAb) specific for either beta(3) or av prolonged survival significantly to a maximal average survival of 19.7 +/- 1.5 days (P <0.01) and 18.4 +/- 0.9 days (P < 0.01), respectively. XT-199, a chemical blocker of the alpha(v)beta(3) receptor also prolonged survival to 19.5 +/- 1.3 days (P < 0.01). In contrast to these receptor blockades, anti-HTNV antibody was not only able to prolong survival, but 20% of infected pups achieved long-term survival. An anti-murine beta(1) antibody comparatively prolonged survival (19.0 +/- 1.2 days), suggesting that HTNV infection is partly mediated through integrin beta(1) receptors as well as through beta(3) receptors in vivo. Our data demonstrate that the beta(3) receptor is important for HTNV infection in vivo, but also suggest that HTNV may utilize additional receptors beyond beta(3) for cellular entry within an organism.

Upregulation of class II beta-tubulin expression in differentiating keratinocytes

The diverse functions of microtubules (MT) in different cells and tissues may be facilitated by compositional changes in tubulin isotypes. We obtained partial cDNA clones of class II beta-tubulin from a library of differentiating normal human epidermal keratinocytes (NHEK) cells, whereas screening via subtractive hybridization for genes involved in calcium-induced keratinocyte differentiation. Analysis of the isotypic composition of beta-tubulin from NHEK cells revealed elevations in class II beta-tubulin concentrations at both protein and message levels during cell differentiation, resulting in increased rates of incorporation of class II beta-tubulin into MT. Immunohistochemistry of normal and pathologic skin tissues showed that class II beta-tubulin occurred in the granular layer of the epidermis and in differentiated areas of carcinomas. Class II beta-tubulin was, however, not observed in the uppermost granular and cornified layers of normal epidermis. Further experiments showed that MT were likely to decay in the final stage of terminal differentiation during formation of the cornified envelope. Our results suggest that there is differential modulation of MT composition and stability during keratinocyte differentiation.

A dominant antigenic region of the hantaan virus nucleocapsid protein is located within a amino-terminal short stretch of hydrophilic residues

The nucleocapsid (N) protein of the Hantaan virus (HTNV) is a major viral antigen that induces a strong antibody response during the acute phase of infection. By immunoblot analyses of the recombinant N proteins using human sera of the hemorrhagic fever with renal syndrome (HFRS), we have confirmed previous finding by other investigators of the presence of a highly antigenic region near the amino terminus of the HTNV N protein. We have further located the antigenic region within a short stretch of hydrophilic sequences between the 26 and the 46th amino acid residues. The recombinant glutathione S-transferase fusion proteins containing this region was expressed as a soluble form in a large quantity in Escherichia coli, and purified by a single-step affinity chromatography. The recombinant antigen also showed a similar, but a weaker reactivity with human antisera to Seoul virus (SEOV), the virus most closely related to HTNV.

Molecular genetic analysis of reovirus isolated in Korea

Reovirus isolates from human, striped-field mouse (Apodemus agrarius) and Korean field mouse (A. peninsulae) in Korea showed extensive variability in the patterns of electrophoretic migration of the double-stranded RNA (dsRNA) genome segments. Hemagglutination inhibition (HI) test was performed for serotype determination of 12 reovirus isolates. To clarify genetic diversity and molecular phylogeny of Korean reoviruses, L1, S3 and S4 genomic segments of reoviruses were amplified by RT-PCR and directly sequenced. Among 12 reovirus strains, 9 strains were type 3 and 3 strains were type 2. The L1 was highly conserved showing 91.5-100%, 94.7-100% similarities among Korean isolates, and 77.5-97.9%, 92.6-96.8% similarities compared to other reference strains of each genotypes at nucleotide and amino acid levels, respectively. In S3 and S4 segments, 84.4-99.3%, 72.3-99% nucleotide sequence similarities and 92-99.3%, 89.1-98.4% amino acid sequence similarities among Korean isolates were observed, and 70.8-93.9%, 72.3-98.7% nucleotide sequence similarities and 81.8-100%, 88.3-97.7% amino acid sequence similarities compared with other reference strains of each genotype were observed, respectively. Phylogenetic analyses based on the S3 and S4 nucleotide sequences indicate that genotypes of reovirus are more related with geographic differences rather than host species or date of isolation.

Molecular epidemiology of hepatitis A virus in Korea

BACKGROUND

The prevalence of antibodies for hepatitis A virus (anti-HAV) in adolescents and young adults has decreased remarkably following the economic growth in Korea. As a result, this age group has a high risk for HAV infection paradoxically, and over 1500 cases of clinically overt hepatitis A occurred in 1998. Human isolates of hepatitis A virus (HAV) are categorized within four genotypes (I, II, III, and VII). In some geographic regions, closely related isolates cluster, suggesting endemic spread of the virus, while in other regions multiple genotypes circulate. Virtually no data are available with regard to the genetic relatedness of Korean strains of HAV.

METHODS AND RESULTS

A 168 base pair segment encompassing the putative VP1/2A junction of the HAV genome was amplified by RT-PCR and sequenced in sera of 18 Korean patients with a sporadic form of acute hepatitis A. Pairwise comparisons of the nucleic acid and amino acid sequences of 18 Korean isolates with one another revealed that the Korean isolates showed > 94.6% and > 96.4% identity, respectively. All of the 18 Korean isolates clustered within genotype IA, irrespective of the geographic locations and the time that hepatitis occurred. Unique amino acid sequence changes that had never been reported in genotype IA were found in nine of the 18 isolates. These changes were Gln-->Ser and Lys-->Arg in 2A-19 and 2A-10 amino acid positions.

CONCLUSION

The presence of single genotype and unique mutations may be related with the circulation of endemic HAV over a long period of time in Korea.

Genetic diversity of Apodemus agrarius-borne hantaan virus in Korea

Hantaan (HTN) virus, the etiologic agent of clinically severe hemorrhagic fever with renal syndrome (HFRS), was first isolated in 1976 from lung tissues of striped field mice (Apodemus agrarius) captured in Songnae-ri, Kyungki-do, Korea. To clarify the genetic diversity and phylogenetic relationship among Korean strains of HTN virus, viral sequences of the partial S and M segments were amplified from lung tissues of 24 seropositive striped field mice captured between 1989 and 1998 at 11 sites in South Korea. The 771-nucleotide (nt) S segment sequences (coordinates 432 to 1202) of HTN virus strains from Yangju-kun differed by 10 to 40 nt (1.3 to 5.2%) from virus strains from Pocheon-kun, Songnae-ri and Nonsan-kun. Similar degrees of genetic variation were found in the G1 and G2 glycoprotein-encoding M segment. Phylogenetic trees, based on the partial S and M segments and generated by the maximum parsimony and neighbor-joining methods, demonstrated that virus strains from various geographic regions in South Korea showed a tendency to form two phylogenetic subgroups and were evolutionarily distinct from HTN virus strains from the People's Republic of China.

Phylogenetic analysis of the small hydrophobic (SH) gene of mumps virus in Korea: identification of a new genotype

Viral RNAs extracted from fifteen mumps virus isolated from throat swab, saliva, blood, urine or CSF during mumps epidemics between 1997-1998 in Korea were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and compared by nucleotide sequencing of the small hydrophobic (SH) gene. The deduced amino acid sequences of the SH gene were aligned with the published sequences of mumps virus isolated in different geographic areas. A comparison of the SH gene of mumps viruses in Korea indicated 96.2-100% and 91.2-100% similarity at the nucleotide and amino acid levels, respectively. Phylogenetic analysis, using the neighbor-joining method, showed that Korean mumps virus strains formed a genetically distinct monophyletic group from previously reported genotypes based on the 315-bp length nucleotide and 57 deduced amino acid sequences of the SH gene, and possibly be designated as a new genotype (I).

Infection rate of Leptospira interrogans in the field rodent, Apodemus agrarius, in Korea

Leptospirosis has significantly decreased in Korea since 1988, following the leptospiral vaccination programme initiated in 1988. Whether this wholly explains the decreased incidence is uncertain. As an initial step to answer this question, infection rates of Leptospira interrogans in field rodents, Apodemis agrarius, were examined and compared with previous data. Two hundred and twenty-two A. agrarius were captured during October-December 1996. Spirochaetes were isolated from 22 (9.9%) and leptospiral DNA was detected in an additional 6 rodents (12.6%). Subsequent microscopic agglutination tests (MAT) classified all these isolates as L. interrogans serogroup Icterohaemorrhagiae serovar lai. The above data did not significantly differ from previous surveys in 1984-7. There was no significant change of L. interrogans infection in field rodents following the introduction of the vaccination programme in Korea. Further studies are needed to determine the role of human vaccination in reducing incidence.

Genetic and phylogenetic analyses of hantaviral sequences amplified from archival tissues of deer mice (Peromyscus maniculatus nubiterrae) captured in the eastern United States

The S and M segments of a hantavirus, enzymatically amplified from tissues of Cloudland deer mice (Peromyscus maniculatus nubiterrae) captured during 1985 in West Virginia, diverged from strains of Four Corners virus from the southwestern United States by more than 16% and 6% at the nucleotide and amino acid levels, respectively. Phylogenetic analysis suggested that this virus strain (designated Monongahela) forms a possible evolutionary link between the Four Corners and New York hantaviruses.

Sequence analysis of the complete S genomic segment of a newly identified hantavirus isolated from the white-footed mouse (Peromyscus leucopus): phylogenetic relationship with other sigmodontine rodent-borne hantaviruses

Four Corners (FC) or Sin Nombre virus, a hantavirus harbored by the deer mouse (Peromyscus maniculatus), is the principal etiologic agent of hantavirus pulmonary syndrome (HPS). Recently, a hantavirus, designated New York (NY) virus, isolated from a white-footed mouse (Peromyscus leucopus) captured on Shelter Island, New York, was molecularly linked to a fatal case of HPS occurring in the northeastern United States. To clarify the genetic and phylogenetic relationship between NY and FC viruses and other sigmodontine rodent-borne hantaviruses, we amplified and sequenced the entire S genomic segment of NY virus. The S segment of NY virus was 2078 nucleotides long, with an open reading frame of 1284 nucleotides in the virus complementary strand, capable of encoding a protein of 428 amino acids, and with a 752-nucleotide long 3'-noncoding region, comprised of numerous imperfect repeats. Pairwise analysis indicated that NY virus was more similar to FC virus than to other sigmodontine rodent-borne hantaviruses, differing from strains of FC virus by 16.6-17.8% and 7.0-8.2% at the nucleotide and amino acid levels, respectively. As determined by the maximum parsimony and neighbor-joining methods, NY virus formed a separate lineage from FC virus and was phylogenetically distinct from hantaviruses harbored by other sigmodontine rodents. Whether or not NY and FC viruses represent distinct viral species is unclear. Further analyses of hantaviruses harbored by white-footed mice are needed to clarify the genetic diversity and evolution of Peromyscus-borne hantaviruses.

Comparison of nucleotide sequences among hantaviruses belonging to the same serotype: an analysis of amplified DNA by thermal cycle sequencing

The hantavirus genus, belonging to the bunyaviridae family, is comprised of at least four serologically distinct types: Hantaan, Seoul, Puumala and Prospect Hill. Previously, we reported the use of the polymerase chain reaction (PCR) for grouping hantavirus isolates by using four sets of primers specific to each serotype. Our PCR typing results agreed with those of serological typing. The present study makes use of thermal cycle sequencing to sequence PCR-amplified DNA products in order to determine the level of similarity among members of the same serotype. We show that members of Hantaan and Seoul serotypes are over 92% homologous, irrespective of their host and geographical origin. Puumala sequences show a degree of homology ranging from 80 to 98%. Despite the variation in sequence at the nucleotide level, amino acids show an even higher level of conservation.

Identification of Hantaan virus-related structures in kidneys of cadavers with haemorrhagic fever with renal syndrome

The etiologic agent of haemorrhagic fever with renal syndrome (HFRS), Hantaan virus, was first isolated in 1976. Since then numerous Hantaan-like viruses have been isolated and five serotypes of Hantavirus have been recognized. Serological studies indicate that these viruses are globally distributed, with each serotype occurring in specific areas. Hantaan virus has been intensively studied antigenically, biochemically, and genetically. However there is still a paucity of information on the pathogenesis of Hantaan virus in the human host. In this paper, we report the detection by thin section immune electron microscopy of the occurrence of numerous dense precipitates, typical inclusion bodies, a surface antigen layer, as well as Hantaan virion-like structures in the kidneys of patients that died during the acute phase of HFRS. These findings may shed some light on understanding the pathogenesis of HFRS in target organs most affected by the disease, such as the kidneys.

[Trombiculid mites (Acarina: Trombiculidae) from Apodemus agrarius coreae caught at Pochun-gun, Gyeonggi Province and Chinhae-City, Kyongnam Province]

During October-December 1987, chigger mites infested on the striped field mice (Apodemus agrarius coreae) collected at Pochun-gun, Gyeonggi Province and Chinhae city, Kyongnam Province were identified. 1. Of 171 back-striped mice collected, chigger mites were 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. palpale(23.0%), L. orientalis(20.2), L. zetum(19.0%). Neotrombicula tamiyai(32.9), N. japonica(0.2%) 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.

Leakey virus: a new hantavirus isolated from Mus musculus in the United States

A hantavirus, designated Leakey virus, was isolated from a Mus musculus captured in Real County, Texas, U.S.A. in August 1986. Virus-specific fluorescence was first detected 13 days after inoculation of Vero-E6 cells with spleen tissue from the seropositive M. musculus. Ultrastructurally, the new isolate resembled other hantaviruses. Leakey virus induced a fatal meningoencephalitis in infant Fischer rats, with viral antigen detectable in brain, lung, liver, kidney and spleen. Serum dilution, plaque reduction neutralization tests indicated that Leakey virus was antigenically distinct from Hantaan, Seoul, Puumala and Prospect Hill viruses, and therefore constitutes a new serotype.

Serological survey of Prospect Hill virus infection in indigenous wild rodents in the USA

We found serological evidence of infection with Prospect Hill virus, a Hantaan-like virus isolated from meadow voles (Microtus pennsylvanicus), in microtine and cricetid rodents trapped in Maryland, West Virginia, Minnesota and California, USA. Fluorescent antibodies were detected in sera from M. pennsylvanicus (74/277), M. californicus (39/185), Clethrionomys gapperi (5/51), Peromyscus maniculatus (4/22) and P. truei (1/11). Sera from seropositive P. maniculatus contained neutralizing antibodies against Prospect Hill virus, confirming that infection with Prospect Hill virus or antigenically related viruses is not restricted to microtine rodents in the USA. Despite the widespread distribution of Prospect Hill virus in indigenous rodents, the recent demonstration that American mammalogists are only rarely infected supports the view that the overall risk of Prospect Hill virus infection in man is low.

Positive serological evidence that Hantaan virus, the etiologic agent of hemorrhagic fever with renal syndrome, is endemic in Canada

Hemorrhagic fever with renal syndrome is endemic in most parts of the world. The etiological agent in known as Hantaan virus. More than 2000 Canadian sera from all age groups and provinces were tested for the presence of antibody to this virus by the indirect immunofluorescent antibody technique. The frequency of seropositivity ranged from 0.3 to 4.0%, with the national average being 1.4%. Newfoundland and New Brunswick in the Atlantic region had the highest positivity, being higher than hyperendemic areas in Korea. The inland provinces of Ontario, Manitoba, and Alberta had only 0.5% positives to Hantaan virus. In contrast, approximately 1.5% of sera from Saskatchewan, Quebec, and British Columbia were positive. No correlation in positivity was found between geography or sex, but positivity did increase with age. The highest titres were found in the group aged 65 to 93 years.

Isolation of Hantaan virus, the etiologic agent of Korean hemorrhagic fever, from wild urban rats

Urban rats captured in Seoul and four nearby Korean cities were found to have immunofluorescent antibodies reactive with Hantaan virus, the etiologic agent of Korean hemorrhagic fever (KHF). Serum antibodies were detected in 13% from 477 Rattus norvegicus and 11% of 47 Rattus rattus. Hantaan viral antigen was found in pulmonary tissues of 42 animals, and Hantaan virus was recovered from 23 rats, all but two of which were R. norvegicus. Wistar rats were qualitatively much more sensitive than Apodemus agrarius rodents for isolation of virus from tissues of wild rats. Wistar rats inoculated with one of these strains had virus in lung and spleen for at least 75 days. These results document the existence of an urban cycle for Hantaan virus, which had been suspected on the basis of the occurrence of sporadic urban cases in humans of KHF, and suggest that Rattus-borne Hantaan virus may be widely distributed in urban centers.

Intraspecific transmission of Hantaan virus, etiologic agent of Korean hemorrhagic fever, in the rodent Apodemus agrarius

Experimental parameters of infection and intraspecific transmission of Hantaan virus, the etiologic agent of Korean hemorrhagic fever, in Apodemus agrarius rodents were determined. Mice inoculated by the intramuscular route experienced viremia for about 1 week beginning on day 7. After 3 weeks, immunofluorescent and neutralizing antibodies were present and no mouse ever developed signs of acute illness. Virus was recovered from lung, kidney, salivary gland, and liver, and virus excretion in urine, saliva, and feces occurred from about day 10 through day 360 (urine) post-inoculation. Antigen, but not infectious virus, was persistent in lung tissue for as long as 1 year. Horizontal contact infection occurred among cage-mates regardless of sexual pairing up to 360 days after infection and no evidence for participation of ectoparasitic arthropods in such transmission was obtained.

Observations on natural and laboratory infection of rodents with the etiologic agent of Korean hemorrhagic fever

Studies were conducted to define the natural host range of the Korean hemorrhagic fever (KHF) agent in South Korea, and to identify colonized rodents susceptible to this infection. Eight species of field rodents were captured in areas of Korea endemic for KHF and their tissues were examined by immunofluorescence for the presence of KHF antigen. One hundred and fourteen of 817 Apodemus agrarius coreae captured between 1974 and 1978 had one or more positive organs. No positive organ was found in 239 rodents of the other seven species examined. Two hundred and thirty-eight specimens of Apodemus agrarius jejuensis captured on Jeju Island, an area thought to be free of disease, were also negative. Attempted laboratory infection of nine species of rodents captured in the field but maintained in the laboratory was successful only in the two subspecies of Apodemus. The 46 specimens of A. a. jejunesis tested in this manner were all uniformly susceptible to infection as determined by immunofluorescence. Serial sacrifice of experimentally infected A. a. jejuensis revealed viremia of short duration terminating on day 10 postinfection. In contrast, other tissues of this animal, including lung, kidney, liver and parotid gland were positive on day 10 and remained so through the 100-day observation period. When 12 species of colonized laboratory rodents were inoculated with KHF agent five were found to develop KHF antibody by indirect immunofluorescence and two, Calomys callosus and Apodemus agrarious ningpoensis, developed detectable KHF antigen in their tissues.