Investigation on the Xenopsylla cheopis Distribution in Shenzhen Suburb

Objective To investigate the distribution of Xenopsylla cheopis in different months and species of rat,to provide the guide on prevention of Plague epidemic in Shenzhen.Methods To survey The flea index,the infection rate of flea on rats and the rat density.monthly,15 to 20 rats were entrapped by cages placed in the Bantian Street, Longgang District from January to December 2007.The significant difference of infection rate of flea among species of rat was compared by x2 test.Results One hundred and eighty five rats entrapped belonged to two species.in which 170 rats were R.norvegicus and the other 15 were R.flavipectus.The average rat density was 12%.The sex ratio(F:M) of rats was1:1.20,and the ratio of adult to young rats was 2.2:1.Two hundred and ninety eight fleas collected from the 185 live rats were identified to one species,Xenopisylla cheopis.The sex ratio(F:M) of fleas was1:0.95.The infection rate of flea on R.norvegicus and R.flavipectus was 41.12% and 26.67% respectively.The difference was significant(x2=17.370,p0.001).The average infection rate of flea on rats in 2007 was 40%,varying from 19% in June to 63% in April.The flea index varied from 0.25 in June to 4.20 in March,with the average value of 1.61.The flea index of R.norvegicus and R.flavipectus was 1.67 and 0.93 respectively.Conclusion Xenopisylla cheopis propagated continuously in Shenzhen suburb.The density of flea fluctuated with seasons with the peak in spring.R.norvegicus was more important than R.flavipectus as the host of Xenopisylla cheopis.