Prevalence of Severe Febrile and Thrombocytopenic Syndrome Virus, Anaplasma spp. and Babesia microti in Hard Ticks (Acari: Ixodidae) from Jiaodong Peninsula, Shandong Province.

The presence of tick-borne pathogens and their possible coinfections were evaluated among host-seeking ticks in seven cities from Jiaodong peninsula, Shandong Province, with specific PCR or reverse transcription-PCR tests. Among 2107 ticks collected, four species of three genera were identified with Haemaphysalis longicornis as predominant species, and total of 63 H. longicornis and 10 Rhicephalus microplus were confirmed infected with tick-borne pathogens. These pathogens were consequently identified as severe febrile and thrombocytopenic syndrome virus (SFTSV), Anaplasma capra, Anaplasma phygocytophilum, and Babesia microti, respectively, with high phylogenetic scores on some fragments of species-specific genes. The infection rates of the pathogens in H. longicornis were presented as 1.03%, 0.84%, 0.58%, and 1.66%, respectively, close related to its field density and clump distribution pattern. Furthermore, coinfection of A. capra and SFTSV was also discovered from two female H. longicornis in Pingdu city. These results indicated that the potential human pathogens other than severe febrile and thrombocytopenic syndrome might be transmitted by hard ticks separately or in combination, and more reliable differential diagnosis, proper administrations, rational prevention, and control measures should be developed with the support of precision laboratory tests.

Comparison of pyrethroid resistance in adults and larvae of Culex pipiens pallens (Diptera: Culicidae) from four field populations in China.

The susceptibility of adults and larvae from four field populations of Culex pipiens pallens (Coguillett) (Diptera: Culicidae) in China to deltamethrin, beta-cypermethrin, and permethrin was investigated using the World Health Organization standard susceptibility test methods. One to 2 d old nonblood fed female mosquitoes emerged from pupae resulting from wild-caught larvae (F1 laboratory reared adults) were exposed to various doses of the pyrethroids. The larval bioassay was conducted using a range of concentrations to determine the LC50 values. Using allele-specific polymerase chain reaction, the frequency of the kdr resistance gene was determined in each population. The bioassay data indicated that deltamethrin was the most active larvicide in all four populations with resistance ratios (RR) of 1.6-3.9-fold. This was followed by beta-cypermethrin with RR of 1.1-3.3-fold, while larvae from three mosquito populations from Beijing, Jinan, and Kaifeng had developed resistance to permethrin with RR of 12.6-, 24.0-, and 18.8-fold, respectively. The overall RR of larvae for all insecticides in ascending order was Changchun < Beijing < Kaifeng < Jinan; and ranking of the adult mortality was Changchun < Jinan = Kaifeng < Beijing. For the three pyrethroids tested, the correlation coefficient among the three test methods on the four populations and one lab strain was quite weak. The R value was 0.113-0.320 when we compared kdr detection for kdr% with LC50, -0.565 to -0.793 when kdr% versus adult mortality test, and -0.750 to 0.505 for LC50 versus adult mortality. Permethrin showed the best correlation (R = -0.793) between kdr frequency and adult mortality. This indicates that levels of susceptibility changes to an insecticide should not be based on a single method of assessment.