Abstract: Dengue fever (DF)/dengue haemorrhagic fever (DHF) is one of the most important human arbo-virus infectious diseases in tropical and subtropical areas with increasing numbers of patients and the expansion of epidemic areas. Understanding the mechanisms of its infection and spread is the foundation for effective surveillance and control of this disease and its mosquito vector. The saliva secreted by feeding mosquitoes is not only the liquid vector of virus transmission, but can also enhance virus infection through immuno-modulation of its vertebrate host.This paper reports experiments that sought to determine if the DEN-2 virus infection in Balb/C laboratory mice could be enhanced by the vector mosquito Aedes aegypti. After being bitten by a number of mosquitoes, mice were injected intravenously with defined titers of the DEN-2 virus. The differences in viremia, the titers of DEN-2 antibodies and the infection rates of macrophages in the abdominal cavities of these mice were observed and compared with those of mice that had only been injected with the DEN-2 virus. The results showed mice that had been bitten by vector mosquitoes were more easier infected with the DEN-2 virus; periods of viremia were extended from 1-2 days to 4 days, antibody titres dropped from 1∶64, 1∶96 to 1∶16 and 1∶32 respectively in the 4th and 7th days after injection while infection rates of macrophages varied over the first 7 days. These results indicate that vector mosquito bites can enhance the infection of mice with the DEN-2 virus.

Key words: Aedes aegypti, siliva, DEN-2 virus, Balb/C mice, infection, enhancement