Biodiversity of culicid mosquitoes in rural Neka township of Mazandaran province, northern Iran.

BACKGROUND & OBJECTIVES: This paper presents the results of a study on ecological parameters including diversity indices applied on populations of Culicidae mosquitoes (Diptera: Culicidae) from three rural areas (Darvishan, Chalmardi and Khairabad) of Neka township in Mazandaran province, northern Iran. METHODS: Adult and larval stages of mosquitoes were systematically sampled to obtain data required for measuring diversity of mosquitoes in these areas. Alfa and beta indices were analyzed to compare mosquito diversity. A total of 5270 specimens belonging to four genera and 14 different species were collected and identified. RESULTS: Evaluation of dominance structure of species showed that culicid mosquitoes of Neka rangelands include one eudominant species, two dominant species, two subdominant species, two rare species and eight subrare species when Heydemann classification was used. INTERPRETATION & CONCLUSION: Data analysis revealed a higher diversity of mosquitoes in Khairabad with a low degree of interspecific dominance, while Darvishan and Chalmardi recorded the lowest observed diversity and a high degree of interspecific dominance. The cluster analysis based on Jaccard's index indicated the relationship between the categories and indicates that Darvishan and Khairabad are the closest categories in their specific composition.

Field evaluation of phostoxin and zinc phosphide for the control of zoonotic cutaneous leishmaniasis in a hyperendemic area, central Iran.

BACKGROUND & OBJECTIVES: ZCL is a growing threat in many rural areas of Iran which involves 17 out of 31 provinces. This study was conducted from April to November 2011 for evaluation of the efficacy of phostoxin and zinc phosphide against rodents. METHODS: Rodent control operations were carried out using phostoxin and zinc phosphide. To evaluate the effect of rodent control operation on the main vector density, an entomological survey was carried out. The effects of the operation on the disease incidence were also evaluated. RESULTS: After intervention, the reduction rate of rodent burrows was 32.68% in the village treated with phostoxin and 58.14% in the village treated with zinc phosphide. The number of rodent holes in the control area showed 6.66-fold increase at the end of the study. The incidence of the disease decreased to 19.23 and 11.40 in areas treated with phostoxin and zinc phosphide, respectively. A total of 4243 adult sandflies were collected and identified. The most common and dominant species was Phlebotomus papatasi. In the village treated with phostoxin, the density of P. papatasi in outdoors was lower than indoors. Nevertheless, the density of P. papatasi in the village treated with zinc phosphide was higher in outdoors. INTERPRETATION & CONCLUSION: It is concluded that phostoxin is less effective and has low safety in comparison with zinc phosphide, so that this rodenticide can be used only in special situations such as lack or ineffective rodenticides and only in the colonies far from human and animal dwelling places in small scales.

Laboratory and field evaluation of two formulations of Bacillus thuringiensis M-H-14 against mosquito larvae in the Islamic Republic of Iran, 2012.

Due to low efficacy in the field of a local commercial product of Bacillus thuringiensis M-H-14 (Bioflash(®)), a study was designed to assess its efficacy in laboratory, glass standard aquarium, semi-field and field conditions at both target and higher dosages against immature stages of Anopheles spp. and Culex spp. In laboratory conditions, the LC50 values of wettable powder and granule formulations were 227 and 1031 ppm respectively against a susceptible strain of An. stephensi. Following application of wettable powder and granules at 56.1 mg/aquarium, the survival rates of the exposed larvae to the granule formulation were 65.6% and 54.2% on days 6 and 8 respectively. In the artificial ponds, the larval density was reduced to 38.9%, 39.3% and 65.1% at dosages of 2, 4 and 8 g/m(2) respectively. In rice fields, at a dosage of 2 kg/ha, the density of immature larvae were reduced to 33.1% and 28.6% 7-days post-treatment. Further investigations are needed for the reasons for the low efficacy of this larvicide.

First report on natural Leishmania infection of Phlebotomus sergenti due Leishmania tropica by high resolution melting curve method in South-eastern Iran.

OBJECTIVE: To identify the Leishmania species in infected sand flies by Real-time PCR coupled with HRM analysis. METHODS: Real-time PCR coupled with HRM analysis targeting the first internal transcribed spacer (ITS1) of nuclear ribosomal DNA as the genetic marker was used to identify and distinguish Leishmania species in sand flies specimens. RESULTS: Three out of 115 females of Phlebotomus sergenti (P. sergenti) (2.6%) were positive to Leishmania tropica (L. tropica). CONCLUSIONS: This is the first report on P. sergenti as the main and proven vector of anthroponitic cutaneous leishmaniasis in Dehbakri County using Real-time PCR coupled with HRM analysis. This method is rapid, sensitive and specific for diagnosing of parasites in infected Sand flies and ideal for large scale genotyping projects.

Laboratory and field evaluation of two formulations of Bacillus thuringiensis M-H-14 against mosquito larvae in the Islamic Republic of Iran, 2012

Due to low efficacy in the field of a local commercial product of Bacillus thuringiensis M-H-14 [Bioflash[registered sign], a study was designed to assess its efficacy in laboratory, glass standard aquarium, semi-field and field conditions at both target and higher dosages against immature stages of Anopheles spp.and Culex spp.In laboratory conditions, the LC[50]values of wettable powder and granule formulations were 227 and 1031 ppm respectively against a susceptible strain of An.stephensi.Following application of wettable powder and granules at 56.1 mg/aquarium, the survival rates of the exposed larvae to the granule formulation were 65.6% and 54.2% on days 6 and 8 respectively.In the artificial ponds, the larval density was reduced to 38.9%, 39.3% and 65.1% at dosages of 2, 4 and 8 g/m[2]respectively.In rice fields, at a dosage of 2 kg/ha, the density of immature larvae were reduced to 33.1% and 28.6% 7-days post-treatment.Further investigations are needed for the reasons for the low efficacy of this larvicide

في ضوء تضاؤل الكفاءة للمنتج التجاري المحلي المستحضر من العصية الثورنجية صمم الباحثون دراسة لتقييم كفاءته في المختبر ضمن حوض مائي زجاجي معياري، وفي ظرف ميدانية وشبه ميدانية لكل من الجرعات المستهدفة والجرعات الأعلى ضد المراحل غير الناضجة من أنواع الأنوفيلات وأنواع الباعضات. وفي الظروف المختبرية، كانت قيم الجرعة القاتلة للنصف من مستحضرات المسحوق المرطب جزءا بالمليون ومن الحبيبات جزءا بالمليون، ضد الذراري المستجيبة من الأنوفيلة الأسطفانية. وبعد تطبيق المسحوق المرطب والحبيبات على حوض مائي بمقدار 65.1 مغ/حوض وجد الباحثون أن معدل بقاء اليرقات على قيد الحياة بعد تعرضهن لمستحضر الحبيبات كان 65.6 % في اليوم 6، و 54.2 % في اليوم 8. أما في الأحواض الاصطناعية فإن كثافة اليرقات انخفضت إلى 38.9 % بجرعة 2 غرام/متر مربع، وإلى 39.3 بجرعة 4 ميلي غرام، وإلى 65 % بجرعة 8 غرام/متر مربع. وفي حقول زراعة الأرز فقد أدت جرعة مقدارها 2 كيلو غرام/هيكتار إلى انخفاض كثافة اليرقات غير الناضجة إلى 33.1 % و 28.6 % بعد مرور 7 أيام على المعالجة. وهناك حاجة لمزيد من الدراسات حول أسباب انخفاض كفاءة مبيدات اليرقات

En raison de la faible efficacité sur le terrain d'un produit commercial local de Bacillus thuringiensis M-H-14 [Bioflash[R], une étude a été élaborée pour évaluer son efficacité en laboratoire, en aquarium de verre standard ainsi que dans des conditions déterraient de semi-terrain à des doses cibles mais aussi à des doses supérieures contre des Anopheles spp.et des Culex spp.à des stades immatures.Aux conditions de laboratoire, les valeurs de la CL[50]pour la poudre mouillable et les formulations en granulés étaient de 227 et 1031 ppm respectivement sur une souche sensible d'An.stephensi.Après application de poudre mouillable et de granules à 56, 1 mg/aquarium, les taux de survie des larves exposées à la formulation en granules étaient de 65, 6 % et 54, 2 % aux jours 6 et 8 respectivement.Dans les plans d'eau artificiels, la densité larvaire a été réduite, passant à 38, 9 %, 39, 3 % et 65, 1 % à des doses de 2 g/m[2], 4 g/m[2]et 8 g/m[2]respectivement.Dans les rizières, à une dose de 2 kg/ha, la densité des larves immatures a été réduite, passant à 33, 1 % et 28, 6 %, sept jours après le traitement.Des recherches supplémentaires sont nécessaires pour expliquer la faible efficacité de ce larvicide

Baseline insecticide susceptibility data of Phlebotomus papatasi in Iran.

BACKGROUND & OBJECTIVES: Phlebotomine sandflies (Diptera: Psychodidae) play main role in the transmission of different forms of leishmaniasis in the world. Phlebotomus papatasi is the main vector of zoonotic cutaneous leishmaniasis (ZCL) in Iran. There are several control measures for vector control using different classes of insecticides. The aim of this study was to breed the sandflies which were collected from a hyperendemic focus of the disease in central Iran in the laboratory condition and to determine its baseline susceptibility to commonly used insecticides. METHODS: Sandflies were collected from the field and were reared in insectary. Susceptibility tests were carried out on their generation. Baseline susceptibility of sandflies to DDT and pyrethroids was evaluated based on LT50 values. A total of 1305 specimens were tested using different time intervals. The LT50 and LT90 values were measured according to the WHO standard tests. The results were plotted using probit analysis and regression lines. RESULTS: The results against female sandflies revealed the LT50 values of 1312.66, 253.66, 36.04, 9.38 and 6 sec to DDT (4%), permethrin (0.75%), deltamethrin (0.1%), cyfluthrin (0.15%) and lambda-cyhalothrin (0.05%), respectively. The figures for male sandflies were 1200.97, 310.10, 18.63, 6.08 and 0.77 sec respectively to the above insecticides. CONCLUSION: The results of this study could help to provide a clue for implementation of currently used insecticides. Furthermore, a specific guideline is needed for monitoring and evaluation of insecticide susceptibility test against sandflies.

Identification of chemical constituents and larvicidal activity of Kelussia odoratissima Mozaffarian essential oil against two mosquito vectors Anopheles stephensi and Culex pipiens (Diptera: Culicidae).

The larvicidal activity of essential oil extracted from an indigenous plant, Kelussia odoratissima Mozaffarian was evaluated against two mosquito species, Anopheles stephensi and Culex pipiens. The chemical composition of the essential oil obtained by hydrodistillation from branch tips and leaf of this plant was determined by GC and GC/MS analysis. Forty-nine constituents were identified in the oil. The main constituents of the oil were Z-ligustilide (77.73%), 2-octen-1-ol acetate (6.27%), E-ligustilide (2.27%) and butylidene phthalide (1.97%). Five different logarithmic concentrations of essential oil were evaluated against the 4th instar larvae of An. Stephensi and Cx. pipiens. The LC(50) and LC(90) values against An. stephensi larvae were 4.88 and 9.60 ppm and for Cx. pipiens were 2.69 and 7.90 ppm, respectively. These properties suggest that K. odoratissima oil has potential source of valuable larvicidal compounds for mosquito larval control. This plant which causes high mortality at lower dose could be considered as a highly active plant. In this paper a guideline suggested for larvicidal activity of plant essential oils.

Larval habitats and biodiversity of anopheline mosquitoes (Diptera: Culicidae) in a malarious area of southern Iran.

BACKGROUND & OBJECTIVES: Malaria is the most important mosquito-borne disease in Iran. It is endemic in south to southeastern part of the country. Knowledge about bio-ecology of vectors will support authorities for appropriate management of the disease. Bashagard district is one of the main endemic areas for malaria in south of Iran. This study was conducted to determine anopheline fauna, diversity and affinity in the area, characterization of larval habitats, and mapping their potential distribution across the district. METHODS: The potential aquatic habitats for Anopheles larvae were extracted from Indian Remote Sensing Satellite (IRS) image and digital elevation model of the area using GIS. Surface water bodies were sampled monthly during 2009­10 for anopheline larvae, while characteristics of their physical environment were recorded and water samples were analyzed. RESULTS: A total of 4511 Anopheles larvae were found during the year with the lowest and highest frequencies in February and April, respectively. Dominant species was Anopheles culicifacies. The Shanon diversity index ranged from 0.570­0.829 at fixed collection sites, while the affinity index was significant among some vector species. CONCLUSION: Riversides and riverbeds were the main breeding places which provided sandy, rocky, and clay beds for different species. The potential breeding places as well as distribution of collected species were mapped. Knowledge about ecology of malaria vectors provides information to health sector for effective control programs.

Field evaluation of permethrin long-lasting insecticide treated nets (Olyset(®)) for malaria control in an endemic area, southeast of Iran.

Long lasting insecticide treated nets (LLINs) have been advocated as an effective tool for prevention and control of malaria. Olyset net was the first LLINs which became commercially available and obtained WHO approval. According to the national strategic plan on evaluation of Olyset net, a field trial was conducted to determine the efficacy of these nets against malaria vectors in an endemic area in the southeast of Iran. Fourteen villages with similar topographical and epidemiological situations were selected and randomly assigned to two clusters of the study: Olyset net and untreated net. Distribution of nets was carried out to cover 100% of the population in Olyset net and untreated net cluster. Anopheline mosquitoes were collected monthly using different WHO standard methods in both areas to determine their abundance, feeding pattern and resting behaviour. Human blood index was determined using ELISA test. Additionally, Olyset nets were evaluated for their biological activity using WHO cone bioassay test by susceptible colony of Anopheles stephensi (Beech strain) and then for insecticide residues by employing high performance thin layer chromatography. Malaria incidence was measured by passive and active case detection from all study population. In total 2115 adult anopheline mosquitoes were collected and identified using morphological characters. They comprised of seven species: Anopheles dthali (Liston), A. culicifacies (Giles), A. stephensi (Liston), A. superpictus (Grassi), A.fluviatilis (James), A. moghulensis (Christophers) and A. turkhudi (Liston). A. dthali, A. culicifacies and A. stephensi were most prevalent species in both areas. In the Olyset net study area, there was a significant reduction of 41.1%, 54.4%, 59.39% and 64.1% in the indoor-resting density of A. culicifacies, A. stephensi, A. dthali and A. superpictus, respectively, with an overall reduction of 39.3% in total mosquitoes in comparison with untreated net area. A significant reduction was also observed in human blood index of vector species in the Olyset net villages. Bioefficacy test results of Olyset nets showed that the median knockdown time was 1.48 and 3.25min, while the average mortality rate was 100% and 72.3%±7.07 in baseline and after 1 year of intervention, respectively. The average permethrin content reached to 68.31% (683.1mg/m(2)) of the initial insecticide dose of 937±21.69mg/m(2) (nearly 1000mg/m(2)) at the end of intervention. Malaria incidence was reduced by 96.6% and 64.8% in the village with Olyset nets and in the villages with untreated nets, respectively. During intervention period, there was a reduction of 93.2% in malaria incidence in Olyset net area as compared to the untreated area. This study indicated that Olyset nets have a major impact on malaria vectors and disease burden; therefore it could be recommended as an effective personal protection tool for malaria control in malarious areas.

Spatial analysis and mapping of malaria risk in an endemic area, south of Iran: a GIS based decision making for planning of control.

Bashagard district is one of the important malaria endemic areas in southern Iran. From this region a total of 16,199 indigenous cases have been reported in recent years. The aim of this study was to determine the situation of the disease and provide the risk map for the area. ArcGIS9.2 was used for mapping spatial distribution of malaria incidence. Hot spots were obtained using evidence-based weighting method for transmission risk. Environmental factors including temperature, relative humidity, altitude, slope and distance to rivers were combined by weighted multi criteria evaluation for mapping malaria hazard area at the district level. Similarly, risk map was developed by overlaying weighted hazard, land use/land cover, population density, malaria incidence, development factors and intervention methods. Our results reveal that the disease mainly occurs in north and east of the study area. Consequently the district is divided into three strata. Appropriate interventions are recommended for each stratum based on national malaria policy. Malaria hazard and risk map, stratification based on relevant information and data analyzing provide a useful method preparedness and early warning system for malaria control, although regular updating is required timely.

Entomological and epidemiological attributes for malaria transmission and implementation of vector control in southern Iran.

Bashagard is an important malaria endemic area in south of Iran. An epidemiological and entomological survey was performed during 2002-2010. The aim of study was to determine malaria situation, species composition of anopheline mosquitoes and susceptibility status of main vectors to insecticides/larvicides. A total of 13,490 malaria cases were recorded, Plasmodium vivax (99.64%), P. falciparum (0.35%) and mix cases (0.01%). The highest and lowest Annual Parasite Incidence (API) were observed in 2007 (145.72/1000) and 2009 (6.29/1000), respectively. Anopheles culicifacies, An. dthali, An. stephensi, An. superpictus, An. fluviatilis, An. moghulensis, An. turkhudi and An. apoci were collected from the area. Two peak activities occur in April and October. The first five species were confirmed as malaria vectors in Iran. No indication of sporozoite in mosquitoes using molecular method was performed. Susceptibility tests using diagnostic dose of insecticides and larvicides showed only resistance of An. stephensi to DDT. Tolerance in An. stephensi to deltamethrin and bendiocarb is reported. The same phenomenon was observed in An. culicifacies to DDT, propoxur and deltamethrin, and in An. dthali to malathion and deltamethrin. Larvae of vectors were susceptible to all larvicides, except for An. stephensi that exhibited tolerance to fenthion. In conclusion it should be emphasized that malaria transmission is a complex process in Bashagard. This event is attributed to five proven vectors with different behaviors which are active in the area. Regarding tolerance of vectors to deltamethrin, resistance management is suggested by using new insecticide with novel mode of action.

Vector ecology and susceptibility in a malaria-endemic focus in southern Islamic Republic of Iran.

This study aimed to carry out a malaria situation analysis, species composition and susceptibility levels of the main malaria vector, Anopheles stephensi, to different insecticides in Bashagard. A longitudinal survey was conducted in 2 randomly selected villages in Bashagard. Malaria vectors were sampled by dipping method for the larvae and hand catch, night-biting catch, total catch, and shelter pit collection for the adults. Standard WHO susceptibility tests were used for a variety of insecticides on F1 progeny of An. stephensi reared from wild-caught females. In total, 693 adult anopheline mosquitoes and 839 third and fourth-instar larvae were collected and identified. They comprised 7 species; the most abundant adult and larvae anopheline mosquito was An. dthali (40.7% and 30.5% respectively). An. culicifacies (24.2%) and An. stephensi (16.7%) were the next most common species for adult mosquitoes. An. stephensi was fully susceptible to malathion and pyrethroid insecticides but resistant to DDT and tolerant to dieldrin.

Field efficacy of expanded polystyrene and shredded waste polystyrene beads for mosquito control in artificial pools and field trials, Islamic Republic of Iran.

Concerns about traditional chemical pesticides has led to increasing research into novel mosquito control methods. This study compared the effectiveness of 2 different types of polystyrene beads for control of mosquito larvae in south-east Islamic Republic of Iran. Simulated field trials were done in artificial pools and field trials were carried out in 2 villages in an indigenous malaria area using WHO-recommended methods. Application of expanded polystyrene beads or shredded, waste polystyrene chips to pool surfaces produced a significant difference between pre-treatment and post-treatment density of mosquitoes (86% and 78% reduction respectively 2 weeks after treatment). There was no significant difference between the efficacy of the 2 types of material. The use of polystyrene beads as a component of integrated vector management with other supportive measures could assist in the control of mosquito-borne diseases in the Islamic Republic of Iran and neighbouring countries.

Upwind responses of Anopheles stephensi to carbon dioxide and L-lactic acid: an olfactometer study.

Excretion of carbon dioxide and L-lactic acid through exhalation and perspiration provides olfactory signals to mosquitoes which allow them to find and bite humans; however, mosquito species differ in this regard. This study investigated upwind responses of Anopheles stephensi, mysorensis form, an important malaria vector in Asia, to carbon dioxide and L-lactic acid under laboratory conditions. While a minimal dose of carbon dioxide (90 ppm) activated the mosquitoes, 10 times this amount suppressed them. L-lactic acid alone did not produce a significant effect by itself, but addition of 6 microg/min of L-lactic acid to a range of 90 to 410 ppm carbon dioxide resulted in attraction. The results provide further support for the hypothesis that CO2 plays an important role in the host-seeking behaviour of zoophilic mosquitoes, and suggests that L-lactic acid might play a more critical role than CO2 in the attraction of An. stephensi.

Comparative study on the effectiveness of coumavec® and zinc phosphide in controlling zoonotic cutaneous leishmaniasis in a hyperendemic focus in central iran.

BACKGROUND: Zoonotic cutaneous leishmaniasis (ZCL) is an increasing health problems in many rural areas of Iran. The aim of this study was to introduce a new alternative rodenticide to control the reservoirs of ZCL, its effect on the vector density and the incidence of the disease in hyperendemic focus of Esfahan County, central Iran. METHODS: The study was carried out from January 2011 to January 2012. In intervention areas, rodent control operation was conducted using zinc phosphide or Coumavec®. Active case findings were done by house-to-house visits once every season during 2011-2012. To evaluate the effect of rodent control operation on the vector density, sand flies were collected twice a month using sticky traps. RESULTS: The reduction rate of rodent holes in intervention areas with Coumavec® and zinc phosphide were 48.46% and 58.15% respectively, whereas in control area results showed 6.66 folds intensification. The Incidence of ZCL significantly reduced in the treated areas. Totally, 3200 adult sand flies were collected and identified in the intervention and control areas. In the treated area with zinc phosphide, the density of Phlebotomus papatasi was higher in outdoors in contrast with the treated area by Coumavec® which the density of the sand fly was higher in indoors. CONCLUSION: Both rodenticides were effective on the incidence of ZCL and the population of the reservoirs as well. Coumavec® seems to be effective on the outdoor density of the vector. This combination of rodenticide-insecticide could be a suitable alternative for zinc phosphide while bait shyness or behavioral resistance is occurred.

Quantitative characterization of cantharidin in the false blister beetle, Oedemera podagrariae ventralis, of the southern slopes of Mount Elborz, Iran.

Cantharidin, a potent vesicant and antifeedant agent, is produced by two families of beetles, Meloidae and Oedemeridae (Coleoptera). In this study, the cantharidin content of oedemerid beetles of central Iran was investigated using the GC-MS method. Cantharidin in both sexes of Oedemera podagrariae ventralis Meïneïtrieãs (Oedemeridae) was found in an average of 3.89 µg/beetle in males and 21.68 µg/beetle in females, which are amounts sufficient to irritate human skin. The average of cantharidin in virgin and coupled beetles was 1.35 and 1.62 (µg cantharidin/mg of beetle) respectively. Females had five to six times more cantharidin in their bodies than males, but there was no significant difference between the amount of cantharidin in virgin and coupled females. The results of this study revealed the production of cantharidin in both sexes of beetle.

Field efficacy of expanded polystyrene and shredded waste polystyrene beads for mosquito control in artificial pools and field trials, Islamic Republic of Iran

Concerns about traditional chemical pesticides has led to increasing research into novel mosquito control methods. This study compared the effectiveness of 2 different types of polystyrene beads for control of mosquito larvae in south-east Islamic Republic of Iran. Simulated field trials were done in artificial pools and field trials were carried out in 2 villages in an indigenous malaria area using WHO-recommended methods. Application of expanded polystyrene beads or shredded, waste polystyrene chips to pool surfaces produced a significant difference between pre-treatment and post-treatment density of mosquitoes [86% and 78% reduction respectively 2 weeks after treatment]. There was no significant difference between the efficacy of the 2 types of material. The use of polystyrene beads as a component of integrated vector management with other supportive measures could assist in the control of mosquito-borne diseases in the Islamic Republic of Iran and neighbouring countries

Vector ecology and susceptibility in a malaria-endemic focus in southern Islamic Republic of Iran

This study aimed to carry out a malaria situation analysis, species composition and susceptibility levels of the main malaria vector, Anopheles stephensi, to different insecticides in Bashagard. A longitudinal survey was conducted in 2 randomly selected villages in Bashagard. Malaria vectors were sampled by dipping method for the larvae and hand catch, night-biting catch, total catch, and shelter pit collection for the adults. Standard WHO susceptibility tests were used for a variety of insecticides on F1 progeny of An. stephensi reared from wild-caught females. In total, 693 adult anopheline mosquitoes and 839 third and fourth-instar larvae were collected and identified. They comprised 7 species; the most abundant adult and larvae anopheline mosquito was An. Dthali [40.7% and 30.5% respectively]. An. Culicifacies[24.2%] and An. Stephensi [16.7%] were the next most common species for adult mosquitoes. An. Stephensi was fully susceptible to malathion and pyrethroid insecticides but resistant to DDT and tolerant to dieldrin

Upwind responses of Anopheles stephensi to carbon dioxide and L-lactic acid: an olfactometer study

Excretion of carbon dioxide and L-lactic acid through exhalation and perspiration provides olfactory signals to mosquitoes which allow them to find and bite humans; however, mosquito species differ in this regard. This study investigated upwind responses of Anopheles stephensi, mysorensis form, an important malaria vector in Asia, to carbon dioxide and L-lactic acid under laboratory conditions. While a minimal dose of carbon dioxide [90 ppm] activated the mosquitoes, 10 times this amount suppressed them. L-lactic acid alone did not produce a significant effect by itself, but addition of 6 microg/min of L-lactic acid to a range of 90 to 410 ppm carbon dioxide resulted in attraction. The results provide further support for the hypothesis that CO2 plays an important role in the host-seeking behaviour of zoophilic mosquitoes, and suggests that L-lactic acid might play a more critical role than CO2 in the attraction of An. stephensi

Origin, transfer and distribution of cantharidin-related compounds in the blister beetle Hycleus scabiosae

Cantharidin provides chemical protection for the coleopteran families Meloidae and Oedemeridae. In the present study, it was observed that cantharidin concentration in Hycleus scabiosae was slightly decreased from mated females (mean = 0.011 mg/mg of dry weight) to males (mean = 0.010 mg/mg) and considerably diminished in relation to virgin females (mean = 0.005 mg/mg). Significant concentrations of palasonin (21.69 ng/mg among virgins and 17.49 ng/mg in mated females) and palasoninimide (14.62 ng/mg in virgins and 9.17 ng/mg in mated females) were found in H. scabiosae. Palasonin, palasoninimide and cantharidinimide content of eggs were measured as 5.61, 7.69 and 7.80 ng/mg respectively. Surprisingly, males showed no trace of cantharidin-related compounds (CRCs); therefore CRCs in H. scabiosae could not be transferred from males to females and based on experiments employing its deuterated form, cantharidin is probably independently synthesized in females from the male nuptial transfer. An inseminated female incorporates about 38.5 ng of cantharidin (0.34 percent of the maternal content), 196.35 ng of palasonin (91.82 percent of maternal content) and 269.15 ng of palasoninimide (96.70 percent maternal content) into each egg mass during oviposition. It seems that eggs of this meloid species exploit a different array of protective chemicals by increasing the ratio of CRCs versus cantharidin. CRCs are less toxic than cantharidin; therefore, such compounds might have been deposited in eggs as a safer substitute for cantharidin to provide effective protection, but does not simultaneously harm the susceptible embryo.(AU)