Three anopheline mosquitoes in Korea were studied for their abilities as vectors for Plasmodium vivax. The female mosquitoes of Anopheles lesteri, An. pullus and An. sinensis were allowed to suck malaria patient blood until fully fed, and they were then bred for 2 weeks to develop from malaria parasites to sporozoites. The result from the above confirmed the sporozoites in one An. lesteri of one individual and five An. sinensis of six individuals. We also reconfirmed that An. sinensis was the main vector to transmit malaria and An. lesteri as well as An. sinensis were able to carry Korean malaria parasites. Therefore, we propose that diversified study is needed to manage malaria projects.
Adult ; Animals ; Culicidae/*parasitology/*physiology ; Female ; Humans ; *Insect Vectors ; Korea ; Malaria/parasitology/transmission ; Male ; *Plasmodium vivax

To evaluate the factors that determine the transmission level of vivax malaria using vectorial capacity, entomological surveys were conducted from June to August, 2000. From 6 nights of human-bait collection in Paju, the human biting rate (ma) was counted as 87.5 bites/man/night. The parity of Anopheles sinensis from human baiting collections fluctuated from 41% to 71% (average 48.8%) of which the rate gradually increased as time passed on: 35.2% in Jun.; 55.0% in July; 66.2% in Aug. From this proportion of parous, we could estimate the probability of daily survival rate of An. sinensis to be 0.79 assumed with 3 days gonotrophic cycle and the expectancy of infective life through 11 days could be defined as 0.073. Blood meal analysis was performed using ELISA to determine the blood meal source. Only 0.8% of blood meals were from human hosts. We could conclude that An. sinensis is highly zoophilic (cow 61.8%). Malaria is highly unstable (stability index < 0.5) in this area. From these data, vectorial capacity (VC) was determined to be 0.081. In spite of a high human biting rate (ma), malaria transmission potential is very low due to a low human blood index. Therefore, we could conclude that malaria transmission by An. sinensis is resulted by high population density, not by high transmission potential. For this reason, we need more effort to decrease vector population and vector-human contact to eradicate malaria in Korea.
Animals ; Anopheles/*parasitology ; Human ; Insect Vectors ; Korea ; Malaria, Vivax/parasitology/*transmission ; Parity ; Plasmodium vivax/*pathogenicity/physiology ; Population Density

Introduction of double-stranded RNA (dsRNA) into some cells or organisms results in degradation of its homologous mRNA, a process called RNA interference (RNAi). The dsRNAs are processed into short interfering RNAs (siRNAs) that subsequently bind to the RNA-induced silencing complex (RISC), causing degradation of target mRNAs. Because of this sequence-specific ability to silence target genes, RNAi has been extensively used to study gene functions and has the potential to control disease pathogens or vectors. With this promise of RNAi to control pathogens and vectors, this paper reviews the current status of RNAi in protozoans, animal parasitic helminths and disease-transmitting vectors, such as insects. Many pathogens and vectors cause severe parasitic diseases in tropical regions and it is difficult to control once the host has been invaded. Intracellularly, RNAi can be highly effective in impeding parasitic development and proliferation within the host. To fully realize its potential as a means to control tropical diseases, appropriate delivery methods for RNAi should be developed, and possible off-target effects should be minimized for specific gene suppression. RNAi can also be utilized to reduce vector competence to interfere with disease transmission, as genes critical for pathogenesis of tropical diseases are knockdowned via RNAi.
Animals ; Communicable Diseases/*genetics/*parasitology ; Helminths/*genetics/metabolism ; Humans ; Insect Vectors/*genetics/metabolism ; Protozoa/*genetics/physiology ; *RNA Interference ; *Tropical Climate

Introduction of double-stranded RNA (dsRNA) into some cells or organisms results in degradation of its homologous mRNA, a process called RNA interference (RNAi). The dsRNAs are processed into short interfering RNAs (siRNAs) that subsequently bind to the RNA-induced silencing complex (RISC), causing degradation of target mRNAs. Because of this sequence-specific ability to silence target genes, RNAi has been extensively used to study gene functions and has the potential to control disease pathogens or vectors. With this promise of RNAi to control pathogens and vectors, this paper reviews the current status of RNAi in protozoans, animal parasitic helminths and disease-transmitting vectors, such as insects. Many pathogens and vectors cause severe parasitic diseases in tropical regions and it is difficult to control once the host has been invaded. Intracellularly, RNAi can be highly effective in impeding parasitic development and proliferation within the host. To fully realize its potential as a means to control tropical diseases, appropriate delivery methods for RNAi should be developed, and possible off-target effects should be minimized for specific gene suppression. RNAi can also be utilized to reduce vector competence to interfere with disease transmission, as genes critical for pathogenesis of tropical diseases are knockdowned via RNAi.
Animals ; Communicable Diseases/*genetics/*parasitology ; Helminths/*genetics/metabolism ; Humans ; Insect Vectors/*genetics/metabolism ; Protozoa/*genetics/physiology ; *RNA Interference ; *Tropical Climate

Extensive previous studies on taxonomy, behavior/bionomics and control of Anopheles sinensis are reviewed and summarized. Recent molecular identification revealed that the population of An. sinensis complex includes An. sinensis, An. pullus, An. lesteri and at least two new species, and An. yatsushiroensis is synonmy of An. pullus. An. sinensis is the main vector specie of vivax malaria in Korea. Larvae of An. sinensis breed in wide range of habitats which are naturally-made clean water, stagnant or flowing; main habitats include rice fields, ditches, streams, irrigation cannals, marshes, ponds, ground pools, etc. Their host preferences are highly zoophilic. Human blood rate is very low (0.7-1.7%) ; nevertheless An. sinensis readily feeds on man when domestic animals are not found near by. They feed on hosts throughout the night from dusk to dawn with a peak period of 02: 00-04: 00 hours; they are slightly more exophagic (biting outdoors) ; much larger numbers come into the room when light is on. Main resting places are outdoors such as grasses, vegetable fields and rice fields. A mark-release-recapture study resulted that 37.1% was recaptured within 1 km, 29.4% at 1-3 km, 21.1% at 3-6 km, 10.3% at 6-9 km and 2.1% at 9-12 km distance. An. sinensis hibernate outdoors (mostly under part of dense grasses) during October-March. At the end of the hibernation period (March-April) they feed on cows at daytime. Until today any single measure to effectively control An. sinensis population has not been found. Indoor residual spray with a long-lasting insecticide can not reduce vector population densities, but shorten their life spans in some degree, so contributes to malaria control.
Animals ; Animals, Domestic/parasitology ; Anopheles/parasitology/*physiology ; Bites and Stings ; *Ecosystem ; Feeding Behavior ; Humans ; *Insect Vectors ; Korea ; Larva/physiology ; *Malaria, Vivax ; Mosquito Control ; Plasmodium vivax ; Population Density ; Seasons

Anthropophilic Culicoides were investigated in a rural community endemic for Mansonella perstans in Ijebu North area of western Nigeria between December 2003 and October 2004. Three hundred and fifty-nine adults of Culicoides fulvithorax collected by human bait in the morning were dissected for Mansonella perstans larvae, and 1.95% of infection rate was found. Seasonal abundance of C. fulvithorax was investigated by monthly biting rates, and showed that higher prevalence was observed in rainy season, with peak in September. Culicoides prevalence was positively correlated with rainfall and relative humidity, but not temperature. Human perceptions on the behavior of these biting midges were determined by interviewing 854 self-selected villagers, of which 86.5% of the interviewees confessed having experienced Culicoides bites. Between 76.5 and 99.1% of the various age groups complained body reactions to Culicoides bites. Itching was the most frequent body reaction. No interviewees associated Culicoides with transmission of any parasitic infections. The results showed need to adequately control Culicoides in the community.
Seasons ; Rural Health ; Rain ; Questionnaires ; Perception ; Nigeria/epidemiology ; Middle Aged ; Mansonelliasis/*transmission ; *Mansonella/isolation & purification ; Insect Vectors/parasitology/*physiology ; Insect Bites and Stings/*epidemiology ; Humidity ; Humans ; Cross-Sectional Studies ; Child ; Chi-Square Distribution ; Ceratopogonidae/parasitology/*physiology ; Animals ; Adult ; Adolescent

It is important to understand the dynamics of malaria vectors in implementing malaria control strategies. Six villages were selected from different sections in the Three Gorges Reservoir for exploring the relationship between the climatic factors and its malaria vector density from 1997 to 2007 using the auto-regressive linear model regression method. The result indicated that both temperature and precipitation were better modeled as quadratic rather than linearly related to the density of Anopheles sinensis.
Animals ; China ; Climate ; Culicidae ; physiology ; Insect Vectors ; physiology ; Lakes ; Linear Models ; Malaria ; parasitology ; transmission ; Models, Biological ; Plasmodium ; physiology ; Population Density ; Population Dynamics ; Rain ; Seasons ; Temperature

OBJECTIVETo verify houseflies Musca spp. as the intermediate host of Thelazia callipaeda and reveal epidemiological situation of thelaziasis in Hubei province.

METHODSDogs eyes infected with T. callipaeda, 400 houseflies Musca and 259 fruitflies Amiota okadai in the city of Laohekou city (previously named as Guanghua county) of Hubei province had been investigated since September 2000. The newborn larvae of T. callipaeda from Laohekou suburbs were fed to houseflies Musca and A. okadai. Larvae used for the study were isolated from female T. callipaeda in laboratory and the susceptibility to houseflies Musca and A. okadai was observed.

RESULTSTwenty-one dogs from Laohekou, the original epidemic areas of thelaziasis were examined and 7 positive dogs in 21 (33.3%) and 11 T. callipaeda (9 females and 2 males) were identified. From 1975 to 2000, no thelaziasis cases were found through retrospective surveys. These 200 houseflies Musca and 135 A. okadai were dissected for examination but showed all negative with the infection. However, newborn larvae of T. callipaeda were used to experimentally infect 112 houseflies Musca and 84 A. okadai and all infected flies were examined on the 20th day after inoculation. As a consequence, houseflies Musca failed to be infected but 9 in 84 (10.7%) A. okadai were positive. 26 infective larvae of T. callipaeda were obtained and 21 of them were inoculated into right eye of one rabbit. The female worm began to produce newborn larvae in 37 days after infection and 3 adult T. callipaeda (two females and one male) were obtained.

CONCLUSIONSFruitflies A. okadai from Hubei province were susceptible to T. callipaeda, which was similar to the result of experimental studies in Anhui province. This survey further confirmed that A. okadai was the intermediate host of T. callipaeda but not houseflies Musca. Infective resources (adult dogs, for instance) had been under controlled thus human thelaziasis had been eradicated in this rural area.

Animals ; Conjunctivitis ; parasitology ; Disease Reservoirs ; Dog Diseases ; parasitology ; Dogs ; Drosophila ; parasitology ; Eye Infections, Parasitic ; epidemiology ; transmission ; veterinary ; Female ; Host-Parasite Interactions ; Houseflies ; parasitology ; Humans ; Insect Vectors ; parasitology ; Longitudinal Studies ; Male ; Spirurida Infections ; epidemiology ; transmission ; veterinary ; Thelazioidea ; isolation & purification ; physiology

In Nigeria, malaria causes up to 11% of maternal mortality. Our main aim was to find out the most common mosquito control measures employed by the pregnant women in Lagos and their effects on malaria infection. The study was carried out over a period of 6 months during which trained interviewers administered questionnaires to 400 pregnant women. The prevalence of malaria was 8.4%. There was no significant association between the prevalence of malaria and age, level of education, or occupation of the participants. Pregnant women in the age range 26-30 had the mean parasite density (409.9+/-196.80). Insecticide spray (32.8%), mosquito coil (27.5%), and insecticide-treated nets (ITN) (15.5%) were the major mosquito control measures employed by the participants while the prevalence of infection among them were 2.3%, 6.2%, and 3.2%, respectively (P<0.05). Only 18.3% of the women had taken more than one dose of intermittent preventive treatment (IPT), while another 11.8% had taken a single dose. The infection rate among them was 4.1% and 6.4%, respectively. Malaria prevalence was highest among those who had not received any dose of IPT (10%). This study showed that the use of ITN and IPT among the pregnant women were still unacceptably low. It also showed that the use of insecticide spray which was the most common malaria control measure adopted by the participants was effective despite the fact that it is not a National Malaria Control Policy. We recommend that a sustained integrated mosquito management and public education should be strengthened in Nigeria.
Adolescent ; Adult ; Animals ; *Culicidae/parasitology ; Female ; Health Knowledge, Attitudes, Practice ; Humans ; *Insect Vectors/parasitology ; Insecticides ; Malaria/epidemiology/*prevention & control ; Mosquito Control/*methods ; Nigeria/epidemiology ; Plasmodium/*physiology ; Pregnancy ; Pregnancy Complications, Parasitic/epidemiology/*prevention & control ; Prenatal Care ; Prevalence ; Public Health ; Questionnaires ; Young Adult