Chigger Mite (Acari: Trombiculidae) Survey of Rodents in Shandong Province, Northern China.

Chigger mites are parasites of rodents and other vertebrates, invertebrates, and other arthropods, and are the only vectors of scrub typhus, in addition to other zoonoses. Therefore, investigating their distribution, diversity, and seasonal abundance is important for public health. Rodent surveillance was conducted at 6 districts in Shandong Province, northern China (114-112°E, 34-38°N), from January to December 2011. Overall, 225/286 (78.7%) rodents captured were infested with chigger mites. A total of 451 chigger mites were identified as belonging to 5 most commonly collected species and 3 genera in 1 family. Leptotrombidium scutellare and Leptotrombidium intermedia were the most commonly collected chigger mites. L. scutellare (66.2%, 36.7%, and 49.0%) was the most frequently collected chigger mite from Apodemus agrarius, Rattus norvegicus, and Microtus fortis, respectively, whereas L. intermedia (61.5% and 63.2%) was the most frequently collected chigger mite from Cricetulus triton and Mus musculus, respectively. This study demonstrated a relatively high prevalence of chigger mites that varied seasonally in Shandong Province, China.

Epidemiological analysis of 133 malaria cases in Shanxian county, Shandong Province, China.

OBJECTIVE: To conduct an analysis of the epidemiological changes in malaria that have occurred in Shanxian county from 2002 to 2016. METHODS: A retrospective study was conducted and data were collected from web-based reporting system to explore the epidemiological characteristics in Shanxian county from 2002 to 2016. All individual case information was obtained from village malaria servicers organized by the local Shandong Institute of Parasitic Diseases. RESULTS: A total of 133 cases were identified as malaria in Shanxian county during this period, including 124 indigenous cases (93.2%) and 9 imported cases (6.8%). The 124 indigenous malaria cases were infected with Plasmodium vivax (P. vivax), whereas 7 of the 9 confirmed imported cases were infected with Plasmodium falciparum (P. falciparum), 1 was infected with Plasmodium ovale (P. ovale) and 1 patient was infected with P. falciparum mixed with P. vivax. The total number of malaria cases included 86 males (64.7%) and 47 females (35.3%). Age of the patients ranged from 1 to 83 years, although most (64.7%) infections occurred in the 21-to 60-year-old age group. Remarkably, 117 of the total malaria cases (98.0%) were reported from 2006 to 2011. The epidemic season was from June to October, with the peak occurring yearly from July to September. The most common occupation of the infected patients was farmer. In total, 58.1% of the cases occurred in 3 townships, namely, Fugang, Huanggang and Caozhuang. CONCLUSIONS: In Shanxian county, the local malaria incidence experienced an emerge-peak-control-eliminate status. However, due to the numbers of migrant labourers returning from Africa, imported cases were continuous and presented an increasing annual trend, which became a non-negligible and a significant impediment for malaria elimination. Therefore, the need to eliminate instances of malaria reintroduction to receptive malaria-free areas should drive strategies to align with the epidemiological changes.

[Cloning, prokaryotic expression and immunological identification of Toxoplasma surface antigen IMP1].

OBJECTIVE: To subelone, express and identify the immune mapped protein 1 (IMP1) which encodes a surface antigen of Toxoplasma gondii. METHODS: The cDNA of T. gondii RH strain was synthesized by reverse transcription PCR, the IMP1 open reading frame (ORF) was amplified by PCR using the T. gondii RH strain cDNA as template, the PCR products were identified by TA-cloning and sequencing, then the IMPI ORF was subcloned into the Nde I and Xho I sites of the vector pET28b, and the positive recombinant pET28b-IMP1 was identified by double-digesting and sequencing. The protein of 6 x His tagged IMP1 was inducibly expressed in E. coli strain BL21 (DE3) with isopropyl ß-D-1-thiogalactopyranoside (IPTG), and the induction time, concentration of IPTG and temperature gradients to optimize protein expression conditions were determined. After the cells carried IMP1 were induced by the optimized conditions and harvested, the resulting bacteria were suspended in resuspension buffer and lysed by sonication, and the supernatants were loaded onto the Ni2+ Chelating Sepharose Fast Flow column for affinity chromatography of the N-terminal 6 x His tagged IMP1 protein. Finally, the fusion IMP1 proteins were identified by Western blotting. RESULTS: The ORF sequence of IMP1 was successfully subcloned from the cDNA of Toxoplasma Gondii RH strain, and the amplified product was sequenced and identified, based on which the IMP1 ORF gene was inserted into the prokaryotic expression vector pET28b, and the recombinant pET28b-IMP1 was constructed successfully. The double-digesting and sequencing results indicated the validity of the recombinant vector. And the optimized conditions for the expression of IMP1 was determined, namely 0.3 mmol/L IPTG induction for 9 h at 20 °C. Furthermore, IMP1 protein was expressed solubly and chelated on Ni2 sepharose beads with high affinity, thus this protein could be purified efficiently by affinity chromatography. The pure fusion protein was confirmed with fine immunocompetence by SDS-PAGE and Western blotting. CONCLUSIONS: IMP1 protein can be high efficiently expressed by the E. coli prokaryotic expression systems, the protein of IMP1 is soluble and has stable characters. The study may lay a useful foundation for the following works including in vivo expression of IMP1, crystal structure study of IMP1 and anti-toxoplasmosis subunit vaccine development.

[Study on biological characteristics of cypermethrin-resistant and -susceptible strains of Aedes albopictus at different temperatures].

OBJECTIVE: To study the biological characteristics of cypermethrin-resistance strain and -susceptible strain of Aedes albopictus under different controlled temperatures in the laboratory. METHODS: The two strains were raised at three different temperatures, 20, 25 degrees C and 28 degrees C respectively, and the biological characteristics of the two mosquito strains, such as reproduction, development and life expectancy, were observed and recorded in the laboratory. RESULTS: The life expectancy of both strains became shorter as the temperature raised, and the resistant strain(69.37% ± 0.01%, 77.04% ± 0.07%) lived shorter than the susceptible strain(85.24% ± 0.03%, 88.23% ± 0.05%)in average. Under 25 degrees C, the hatching rate of resistant strain decreased by 25.88%, and the pupation rate decreased by 11.18%. In the three temperatures, all the life expectancy expanded as the temperature went up, the periods for the susceptible strain were 19.75 ± 0.10, 23.65 ± 0.07 d and 25.08 ± 0.08 d under 28, 25 degrees C and 20 degrees C. While life expectancy for the resistant strain decreased to 17.21 ± 0.09, 20.95 ± 0.09, 22.58 ± 0.10 d. Under the same temperature, the development timing of the resistance strain was longer than that of the susceptible strain, and the period was the longest under 28 degrees C (156.2 h, 137.1 h). In the three temperatures, all the development periods expanded as the temperature went up, the susceptible and resistant larvae developed 137.1 d and 163.3 d, 247.7 d and 156.2 d, 182.3 d and 263.2 d under 28, 25 degrees C and 20 degrees C. The differences show statistic significance (P < 0.05). CONCLUSION: The resistance of A. albopictus to cypermethrin results in the decrease of adaptability to the environment change and the disadvantage of reproduction at different temperatures.