RESUMO
BACKGROUND: The aim of the current study was to develop a marking technique as an internal marker to mark post blood meal mosquitoes by using stable phosphate isotope (32)P and determine the optimal concentration of it. METHODS: An isotonic physiological saline solution, containing different concentration of radioactive isotope (32)P-labeled disodium phosphate (Na2H(32)PO4) was injected into rabbits via the jugular vein in the laboratory. Emerged Cx. pipiens were marked after feeding on rabbit. At the same time, the labeled conditions of emerged Cx. pipiens were also measured by placing feces of No. 6 rabbit into containers with mosquito larvae and pupae inside. RESULTS: According to the label condition of Cx. pipiens after taking blood and the effect of different dosage Na2H(32)PO4 on rabbit health, the optimal concentration of radioactive isotope was determined, that is, 0.1211 mCi/kg. By placing feces of No. 6 rabbit into containers with mosquito larvae and pupae inside, the emerged mosquitoes were also labeled. Therefore, feeding mosquitoes on the animal injected with radioactive Na2H(32)PO4 was more practical for detecting and tracing mosquitoes. CONCLUSION: The method was less time-consuming, more sensitive and safer. This marking method will facilitate post-bloodmeal studies of mosquitoes and other blood-sucking insects.
RESUMO
OBJECTIVE: To study the impact of imported filariasis cases on the elimination program in different areas of Shandong Province. METHODS: Dezhou was selected as former low endemic area and Yicheng as former high endemic area. Blood examination was carried out for both mobile population and local people for microfilariae(Mf). Mosquitoes were caught in field and dissected to count the ratio of those having laid eggs and the natural filarial infection rate. Mosquitoes reared at different temperatures were fed with Mf-positive blood and dissected after certain time period to observe the development of the larvae. The vectorial capacity and case transmission quantity were calculated and compared with those from different areas. RESULTS: The Mf positive rate of inflow population was 3.18% in average. No case was detected from 9,411 local residents after blood exam in Dezhou while 2 out of 692 local residents were found Mf positive in Yicheng. Mosquitoes natural infection rate was 3.81% but no third stage larva was found. The shortest time period needed for the larva to develop into an infective stage was 16 days in Dezhou and 11 days in Yicheng. The time period from blood meal to egg-laying on average was 4.95 days in Dezhou and 4.33 days in Yicheng. The ratio of vectorial capacity and case transmission quantity was 1:4.41 and 1:5.82 respectively in Dezhou and Yicheng. CONCLUSION: Filarial transmission seems unlikely in Dezhou for its low vectorial capacity and low transmission quantity resulted from low and evidently fluctuating temperature in the north. A low level filarial transmission may be possible in former high-endemic area such as Yicheng if there are as many imported cases as in Dezhou.
