[Studies on the experimental transmission of Rattus-borne Hantavirus by Ornithonyssus bacoti]

To demonstrate the role of rat mite (Ornithonyssus bacoti) in the transmission of Rattus-borne hemorrhagic fever with renal syndrome (HFRS).

In the transmission experiments, about 100 O. bacoti per pool were isolated and placed in a jar, unfed for 4 d at 23 +/- 1 degrees C. Suckling Wistar rats inoculated with Hantavirus strain Z45 or Seoul virus strain UR were placed in each jar for free attack by the mites for 12 hours. After 14 d the normal suckling Wistar rats were bitten by the mites. Fifteen days later, the lung tissues and sera of the infected rats were collected and detected for Hantaviral antigen by indirect fluorescent antibody technique (IFAT). For demonstration of the infection of O. bacti with Rattus-borne Hantavirus PCR technique was applied to detect Rattus-borne Hantaviral RNA.

Sukling Wistar rats inoculted Hantavirus strain Z45 or Seoul virus strain UR were bitten by O. bacoti and then these mites were fed on 4 and 5 of normal suckling rats in each jar, respectively. The antigens of Hantavirus strain Z45 were positive in all the lungs of the normal rats bitten by the mites, the sera titers of the rats were from 1:10 to 1:40. The antigens were positive in 3 of the 4 rats, the sera titers were from 1:20 to 1:40. Both of the viruses could be maintained in O. bacoti for 22 days. The blocking test showed when 1:30 Hantavirus immunosera were exposed to the lung samples and then reacted with the sera from the patients with HFRS, all the specific fluorescence reactions of the samples were blocked, whereas the control group including the normal rat lung tissues and sera were all negative (Fig. 1).

O. bacoti might play a role as the vector of HFRS and a reservoir host as well.