Community Structure And Dynamics Of Fleas In Microtus Fuscus Nature Plague Foci In Shiqu Of China’s Sichuan

Shiqu county of Sichuan province is Microtus fuscus Nature Plague Foci inQinghai-Tibet Plateau, where Y. pestis is usually transmitted in mammals by infected fleasand produces plague that can threaten public health, development of stockbreeding, andeven human life. Fleas community structure and dynamic play an important role forPersistence of Y. pestis, and it is also the major indicator of early stage of the plagueepidemics. Here, we investigated the community structure and dynamic of ectoparasiticflea and nest flea assemblages of M. fuscus, with the objectives of understanding thedynamic laws and developing trends of fleas, preventing flea pest outbreak, and ultimatelycontrolling plague in Shiqu county.Regular monthly surveys were conducted on ectoparasitic flea and nest fleaassemblages of M. fuscus according to the plague monitoring scheme of china from May toSeptember in2011and2012. And then, we calculated the flea-carrying rate, flea index,diversity index, evenness index and dominance index, and this approach allows tests forthe community structure and dynamic of fleas. The results as follow:1. A total of3715individuals from87rat nests were collected, which wereidentified to8species. The collected flea species in Qingchuan County were Callopsyllsparsilis, Amphalius clarus clarus, Amphipsylla tuta tuta, Amphalius qinghaiensis,Amphalius primaris primaris, Rhadinopsylla li, Rhadinopsylla dives, Rhadinopsylladahurica vicina. The proportion of the population of C. sparsilis and A. tuta tuta reached to60.32%and38.33%respectively, and it was less than1.00%for the population of otherflea species. Thus, C. sparsilis and A. tuta tuta were two dominant species in rat nest.Morisita-Horn index (Cmh) ranged from0.942to1.000, with the average value of0.987,indicating that the composing proportion of nest flea species remained relatively stableduring the investigations. All the87rat nests were infected with fleas, flea-carrying rate ofrat nests was100%. Nest flea index ranged from22.83to65.20, and it had the averagevalue of41.59. Nest flea index, index of C. sparsilis and A. tuta tuta varied from month tomonth significantly (p<0.05): nest flea index presented a descend trend from May to August in2011, and then rised to58in September2011. Nest flea index was only22.83inMay2012, and it presented a rising trend from May to September in2012. Nest flea index,index of C. sparsilis and A. tuta tuta were significant lower in2012than those in2011(p<0.05).2. There are no-significant months and annual difference of communitydiversity index and dominance index for nest fleas (p>0.05). Species number of nest fleawas lower in2012than it in2011significantly (Mann-Whitney Test：U=0.500，p<0.01).Nest flea community evenness index was significantly bigger in2012than it in2011(t=-3.796，p<0.05). Nest flea community evenness declined from August to September in2011, and then varied periodically with high values from May to September in2012.3. A total of1595individuals from1482Microtus fuscus were collected, whichwere identified to5species. The collected flea species in Qingchuan County were C.sparsilis, A. tuta tuta, A. qinghaiensis, R. li, R. dahurica vicina. The proportion of thepopulation of C. sparsilis and A. tuta tuta reached to58.62%and41.07%respectively, andit was less than1.00%for the population of other species. Thus, C. sparsilis and A. tutatuta were two dominant species in rat nest. There are817M. fuscus were infected withfleas, flea-carrying rate on rat body ranged from40.70%to71.43%, and it had the averagevalue of55.22%; body flea index ranged from0.75to2.37, and it had the average value of1.12. Body flea index, flea-carrying rate on rat body, index of C. sparsilis and A. tuta tutavaried from month to month significantly (Kruskal-Wallis Test：p<0.05): flea-carrying rateon rat body, body flea index and C. sparsilis index presented a descend trend from May toSeptember in2011, while a a rising trend from from May to September in2012. A. tutatuta index were biggest in May of each yeas respectively. There are no-significant annualdeference of body flea index, flea-carrying rate on rat body, index of C. sparsilis and A.tuta tuta (p>0.05).4. There are no-significant months and annual difference of communitydiversity index, dominance index, dominance index, and species number for ectoparasiticfleas(p>0.05).Above all, we think that:1、Both flea-carrying rate of rat nests(100%) and nest flea index (41.59) were large with the dominant species of C. sparsilis and A. tuta tuta. Nestflea index, index of C. sparsilis and A. tuta tuta were significant lower in2012than thosein2011. Species number and community evenness index was significantly differencebetween2012and2011, nest community changed in different years.2、Body flea index,flea-carrying rate on rat body, index of C. sparsilis and A. tuta tuta varied significantly indifferent months, but no-significant in different years.3、Nest flea index and the populationof dominant species changed after the snowstorms happened on January,2012.Snowstorms had a large impact on nest flea community, while it seems to have less impactfor body fleas community structure. Therefore, we hypothesized that killing fleas in springhas good efficacy for nest flea control; and deratization has good efficacy for body fleacontrol.4、 Long-term monitoring of flea community and dynamic, especially thepopulation of C. sparsilis and A. tuta tuta, will likely need to be carried out in Shiqucounty.