Repellency of 20 plant essential oils to malaria main vector in the Republic of Korea (ROK), Anopheles kleini, was evaluated using skin direct contact bioassay. Anopheles kleini showed the highest repellency to Pelargonium graveolens with EC50 value of 0.244 mg/cm2, followed by Pinus sylvestris and Cinnamomum camphora with EC50 values of 0.484 mg/cm2 and 0.862 mg/cm2. The lowest repellency of An. kleini was revealed from Clary sage oil with EC50 value of 4.665 mg/cm2. Anopheles kleini did not demonstrated any repellency to Lemon, Orange, Neem, Coconut and Olive oil over 20 mg/cm2. Major repellent constituents of Geranium, Pine and Camphora oil were analyzed and identified using Mass-data, GC and GC-Mass. Major constituent of Geranium were β-citronellol (37.0%) and Camphora, 1,8-cineole (35.8%) and Pine, α-terpineol (39.5%). Anopheles kleini showed higher repellency to β-citronellol and 1,8-cineole than to DEET and IR3535 and did not showed any repellency to sabinene and γ-eudesmol over 20 mg/cm2. Residual repellent time of 1,8-cineole and β-citronellol were 26 and 41 min, respectively and DEET, 84 min and IR3535, 102 min. In the light of global efforts to reduce the level of highly toxic synthetic repellents, the three essential oils and their major constituents described merit further study as potential biorepellents for the control of An. kleini populations

An assessment was made of the toxicity of 12 insecticides, three essential oils and Bacillus thuringiensis var. israelensis (Bti) alone or in combination with the oil major constituents, (E)-anethole (AN), (E)-cinnamaldehyde (CA) and eugenol (EU), to third instars from bamboo forest collected Aedes albopictus and rice paddy field collected Anopheles sinensis resistant to various groups of insecticides. The toxicity of the test insecticides, essential oils and binary mixtures of Bti and the oil constituents (1:1 ratio) was evaluated using a direct-contact mortality bioassay. Binary mixtures of B.t.i. and CA, AN or EU were significantly more toxic against Ae. albopictus larvae (LC50, 0.0084, 0.0134 and 0.0237 mg/l) and An. sinensis larvae (0.0159, 0.0388 and 0.0541 mg/l) than either B.t.i. (1.7884 and 2.1681 mg/l) or CA (11.46 and 19.43 mg/l), AN (16.66 and 25.11 mg/l) or EU (24.60 and 32.14 mg/l) alone. Based on the co-toxicity coefficient (CC) and synergistic factor (SF), the three binary mixtures operated in a synergy pattern (CC, 140.7–368.3 and SF, 76–213 for Ae. albopictus CC, 75.1–245.3 and SF, 40–136 for An. sinensis).The binary mixtures of Bti and essential oil constituents described, particularly (E)-cinnamaldehyde, merit further study as potential mosquito larvicides for the control of malaria vector mosquito populations in light of global efforts to reduce the level of highly toxic synthetic insecticides in the aquatic environment.

Field-collected populations of mayflies, Ephemera orientalis were tested for susceptibility to 10 different insecticides using a direct-contact mortality bioassay. Ephemera orientalis subimagoes were susceptible to the insecticides chlorpyrifos, fenitrothion and chlorfenapyr with LD50 values of 69.7, 78.8 and 81.9μg/♀, and adults had LD50 values of 71.9, 78.8 and 85.4μg/♀, respectively. Susceptibility ratios(SRs) of subimagoes and adults of E. orientalis to the 10 insecticides were 1.0 to1.2 folds. The mayflies showed higher susceptibility to organophosphates than to pyrethroids. The SRs of Anopheles sinensis to E. orientalis were 514 to 1,438 fold higher for organophosphates (LD50 values of 0.05 to 0.23μg/♀) and 62 to 1,155 fold higher forpyrethroids (LD50 values of 0.13 to 2.41μg/♀). The SRs of Culex pipiens to E. orientalis were 606 to 3,595 fold higher for organophosphates with LD50 values of 0.02-0.17μg/♀ and 81 to 1,365 fold higher for pyrethroids with LD50 values of 0.11- 1.83μg/♀. These results indicate that the use of ineffective insecticides will result in unsatisfactory control against field populations of the subimagoes and adults of E. orientalis. This work was supported by a research grant from the National Vector Control and Surveillance work performed by the Korean National Institute of Health.

Density of malaria vector mosquitoes, Anopheles mosquitoes, and infection of Plamodium vivax from the vector mosquitoes were monitored at 9 surveillance points in Incheonsi, 12 in Gyeonggi province and 7 in Gangwon province in the Republic of Korea (ROK) from April to October of 2010. The seasonal numbers of Anopheles mosquitoes collected weekly showed a high degree of variability. A total of 4,435 mosquitoes were captured using black light traps. Members of the Anopheles mosquito group were the most abundant species and accounted for 71.8% of the mosquitoes collected. The majority of this species were collected from Incheonsi (86.2%), particularly from Ganghwagun (84.8%). During June, populations of this species steadily increased and peak at second week of July. Thereafter, populations of this species decreased by the second week of August and increased by the third week of August, again. Anopheles mosquitoes steadily decreased from the fourth week of August. First Anopheles mosquitoes were reported in Wolgotri (15th weeks/year), Ganghwagun, Incheonsi, followed by Tanhyundong (16th weeks/year), Pajusi, Gyeonggi Province and Daemari (17th weeks/year), Cheolwongun, Gangwon Province. In Ganghwagun in which the most abundant malaria patients (102 patients) were reported, Anopheles mosquitoes demonstrated the highest species portion (over 70%) among collected mosquito species from July to September. Infection rate of P. vivax from the Anopheles mosquitoes also was the highest in Ganghwagun. In Gangwon and Gyeonggi provinces, collection rate of Anopheles mosquitoes and infection rate of P. vivax were relatively lower than those of Ganghwagun. Reported malaria patient cases in Gangwon and Gyeonggi provinces also were relatively lower than those of Ganghwagun. However, detailed results showed that there were some sites in which any correlation between malaria patients and vector mosquitoes were not. This may be resulted from size of surveillance area. Smaller size of surveillance area was, higher accuracy of analysis on correlation between vector mosquitoes and patients was. Further studies on relationship between malaria vector and patients may need for more accurate analysis, such as increase of collection site and so on.

Mosquito-borne viral pathogens infect millions of people worldwide, often resulting in fatal infections. Our research interests in mosquito vector biology focuses on understanding of the molecular and genetic basis of mosquito resistance to arbovirus infections. Unlike mammalian cells including humans, for instance, mosquito cells do not show pathologic symptoms when infected by arboviruses. This observation led us to embarking a microarray study to investigate mosquito-virus interactions using Anopheles gambiae and o’nyong-nyong virus (ONNV) as a model system. As a result, we found that transcription of the hsc70B gene is increased about 2.6-fold in ONNV-infected An. gambiae compared to non-infected controls. Subsequently, in vivo RNAi silencing of the hsc70B transcript caused enhanced ONNV replication in female mosquitoes. Therefore, these results suggest that the hsc70B protein has an inhibitory effect on ONNV replication. A promoter analysis of the hsc70B locus further demonstrated that the hsc70B promoter is able to induce transcription of hsc70B in response to ONNV infection. In addition, hsc70B transcription was also induced by West Nile or La Crosse virus infection. Collectively, our findings indicate that hsc70B plays a role in suppressing virus replication as a general antiviral mechanism. Implications of hsc70B research and our other research endeavors toward the control of mosquito-borne infectious diseases will be discussed.

Bacillus thuringiensis는 포자형성기 동안에 위생해충이나 농업해충에 독성을 보이는 내독소 단백질을 생성한다. 내독소 단백질의 모기 유충 방제효과를 높이기 위해, 광합성에 관여하는 psbA promoter로 모기 살충성 cry11Aa유전자를 발현하는 pSyn4D벡터를 제작하고, 모기 유충이 먹이로 이용하는 Synechocystis PCC6803에 형질 전환시켰다. 형질 전환체들은 kanamycin이 포함된 배지에서 선발되었으며, 정상적인 생물검정을 통해 형질 전환체 Tr2C를 선발하였다. cry11Aa 유전자는 형질전환체의 genomic DNA에 안정적으로 결합되어 있는 것을 PCR을 이용하여 확인하였다. 형질전환체 Tr2C는 약 72-kDa크기의 Cry11Aa 단백질을 발현하였으며, 작은빨간집모기(Culex tritaeniorhynchus) 3령 유충과 중국얼룩날개모기(Anopheles sinensis) 3령 유충에 75%가 넘는 살충력을 보였다. 모기 유충에 대한 형질전환체의 반수치사시간(LT)은 작은빨간집모기 유충과 중국얼룩날개모기 유충에 대해 각각 2.1일과 0.7일이었다. 이상의 결과들은 형질전환체 Tr2C가 모기 유충방제에 유용하게 이용될 수 있음을 보여준다.