Reservoir host expansion of hantavirus, China.
Jiaonan County in Shandong Province is one of the high-incidence HFRS areas in China. To detect the hantavirus infection in small mammals, we trapped rodents and shrews during December 2012-November 2013 using snap-traps in Jiaonan County (longitude 119[degrees]30'-120[degrees]30', latitude 35[degrees]35'-36[degrees]08').
We captured 1,276 animals comprising 5 rodent species and 1 shrew species (Table) and analyzed serum antibody against hantavirus of each animal using an antigen sandwich ELISA Kit (Shanghai Jiahe Biotechnology, Shanghai, China). The serum was considered to contain antibodies against hantavirus when the optical density (OD)450nm of the sample was greater than the threshold. The threshold was calculated by using the equation: threshold = the average OD of the negative control + 0.15. ELISA results showed that 23.3% of animals were seropositive to hantavirus antigen (Table). The seropositive rate to hantavirus was 44.0% in Asian house shrews (Suncus murinus), 25.3% in house mice (Mus musculus), 15.4% in Chinese hamsters (Cricetulus griseus), 10.3% in brown rats, 10.1% in striped field mice (Apodemus agraius), and 3.0% in greater long-tailed hamsters (C. triton). The seropositivity rate for rodents was higher during summer (May-August) and lower during spring (March and April) and winter (October and November) but not significantly different among the months.
To determine what types of hantavirus infected the animals, we amplified viral RNA of HTNV and SEOV from animal lung samples using reverse transcription PCR with serotype-specific primers (7); 2.1% of animals had viral RNA of HTNV, and 2.1% had viral RNA of SEOV (Table). HTNV RNA was detected in striped field mice (6.3%), house mice (1.4%), and brown rats (0.6%). The hantavirus-positive animals were captured in February, April, and November for stripped field mice; November for brown rats; and April and November for house mice. SEOV was detected in brown rats (8.2%) and Asian house shrews (1.7%). These SEOV-positive animals were captured in January, March, May, June, and July for brown rats and March and November for Asian house shrews. The phylogenetic analysis of sequences amplified by reverse transcription PCR is presented in the online Technical Appendix Figure (http://wwwnc.cdc.gov/EID/article/21/1/14-0960-Techapp1.pdf). The nucleotide sequences of the PCR products have been deposited in GenBank (accession nos. KM357423-KM357452).
Hantavirus had been considered to be strictly associated with specific reservoir hosts and to have the same geographic distribution pattern as these reservoir hosts. All hantaviruses that caused human diseases had been associated with rodents, including members of Murinae, Arvicolinae, and Sigmodontinae spp. Insectivore hantaviruses were not known to cause human disease. The rodent hantavirus and the insectivorous hantaviruses were thought to have co-evolved with their specific rodent and insectivorous hosts over millions of years (8). One observed geographic clustering of hantavirus strains, and the association of hantaviruses with their reservoirs, might have been caused by an isolation-by-distance mechanism (9,10) and mixture of both host switching and co-divergence (10). Our study demonstrated that HTNV not only infects its traditional host, the striped mouse, but also infects house mice and rats; SEOV infects not only rats but also shrews, suggesting host expansion for both HTNV and SEOV in China. Our hypothesis is that the hantaviruses co-evolved with their animal hosts, such as SEOV with rats and HTNV with striped mice, but when their animal hosts expanded their territory, hantavirus had more chance to infect other susceptible rodents and expanded their animal hosts.
Both Asian house shrews and house mice are closely associated with humans by living inside and outside of human houses in China. The Asian house shrew and house mouse have been underestimated as potential animal hosts of SEOV and HTNV. To our knowledge, only 1 previous study had associated Asian house shrews with SEOV; in that study, an SEOV strain was isolated from an Asian house shrew in China (2).
We are grateful to David H. Walker for reviewing our manuscript. This study was supported by Shandong University.
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Author affiliations: School of Public Health, Shandong University, Jinan, China (L.-Z. Fang, L. Zhao, H.-L. Wen, J.-W.. Liu, S.-T. He, X.-S. Zhang, X.-j. Yu); Huangdao District Center for Disease Control and Prevention, Qingdao City, China (Z.-T. Zhang, Z.-F. Xue, D.-Q. Ma); College of Medicine and Nursing, Dezhou University, Dezhou City, China (Y. Zhang); and University of Texas Medical Branch, Galveston, Texas, USA (X.-j. Yu)
Li-Zhu Fang,  Li Zhao,  Hong-Ling Wen,  Zhen-Tang Zhang, Jian-Wei Liu, Shu-Ting He, Zai-Feng Xue, Dong-Qiang Ma, Xiao-Shuang Zhang, Yan Zhang, and Xue-jie Yu
 These authors contributed equally to this article.
Address for correspondence: Xue-jie Yu, Shandong University School of Public Health, 44 Wenhuaxilu, Jinan, Shandong Province, 250012 China; email: firstname.lastname@example.org; or Department of Pathology, University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-0609, USA; email: email@example.com
Table. Seropositive rate and RT-PCR-positive rate of hantaviruses in small mammals, Jiaonan County, China, December 2012-November 2013 * Seroprevalence of Animal species No. (%) animals hantavirus Apodemus agrarius 268 (21.0) 27 (10.1) Cricetulus griseus 156 (12.2) 24 (15.4) C. triton 135 (10.6) 4 (3.0) Mus musculus 245 (19.2) 62 (25.3) Rattus norvegicus 213 (16.7) 22 (10.3) Suncus murinus 259 (20.3) 114 (44.0) Total 1,276 (100) 253 (19.8) No. tested/no. RT-PCR positive (%) Animal species HTNV SEOV Apodemus agrarius 12/191 (6.3) 0/191 Cricetulus griseus 0/63 0/63 C. triton 0/48 0/48 Mus musculus 2/143 (1.4) 0/143 Rattus norvegicus 1/159 (0.6) 13/159 (8.2) Suncus murinus 0/121 2/121 (1.7) Total 15/725 (2.1) 15/725 (2.1) * HTNV, Hantaan virus; RT-PCR, reverse transcription PCR; SEOV, Seoul virus.
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|Author:||Fang, Li-Zhu; Zhao, Li; Wen, Hong-Ling; Zhang, Zhen-Tang; Liu, Jian-Wei; He, Shu- Ting; Xue, Zai-Fen|
|Publication:||Emerging Infectious Diseases|
|Date:||Jan 1, 2015|
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