Modified technique of Wolbachia removal from Malaysian Aedes albopictus

ObjectiveTo develop an artificial and modified Wolbachia removal technique using tetracycline from naturally Wolbachia infected Aedes albopictus (Ae. albopictus) so as to be able to produce generations of Wolbachia free offsprings.MethodsIn this study, seven different tetracycline treatment methods were conducted to obtain the best removal method. Four methods focused on larvae tetracycline treatment, one method on both larvae and adult tetracycline treatment and the last two methods on adult mosquito sucrose treatment.ResultsAll larval tetracycline treatments resulted in either high larvae mortality, sterile F₀ adult mosquitoes or unsuccessful Wolbachia removal. Treatment of both larvae and adults resulted in reduced larvae mortality, successful Wolbachia removal but slow mosquito fecundity. As for the adult treatment, 1.0 mg/mL as previously published was not able to completely remove Wolbachia in F₁ generation whereas 1.25 mg/mL successfully removed Wolbachia from F₁ and F₂ mosquitoes in 2 weeks.ConclusionsThis method is different from the previously published methods as it provides an improved Wolbachia removal technique from Ae. albopictus with high egg hatchability, low larvae mortality, increased fecundity and better Wolbachia removal rate.     

Bioefficacy of crude extract of Cyperus aromaticus (Family: Cyperaceae ) cultured cells,against Aedes aegypti and Aedes albopictus mosquitoes

Objective

To evaluate the growth inhibition activity of the crude extract of Cyperus aromaticus (C. aromaticus) cultured cells against the 3rd instar larvae of Aedes aegypti (Linn.) and Aedes albopictus Skuse (Ae. albopictus) under laboratory conditions, and determine the sublethal effects (EI₅₀) of the crude extract of C. aromaticus cultured cells on some biological and morphological parameters of both Aedes mosquito species during two generations as well.

Methods

The cell suspension cultures of C. aromaticus were activated from five callus lines (P4, Pa, Z1, Z6 and Ml) derived from the root explants of in vitro plantlets. The cultured cells were extracted in chloroform and used as plant material for the present study. For detection of juvenile hormone III, the crude extracts were analyzed by HPLC. Then the crude extracts of the three C. aromaticus cultured cell lines which contained varied amounts of juvenile hormone III [high level (P4 cell line), medium level (Z1 cell line) and low level (Ml cell line)] were tested against Aedes mosquito species. Laboratory evaluation was performed against late third instar larvae of the Vector Control Research Unit strains of Ae. aegypti and Ae. albopictus using the standard WHO method. The effects of EI₅₀ of the C. aromaticus cultured P4 cells on fecundity, fertility, growth period, sex ratio, adult size and longevity of Aedes mosquitoes were assessed.

Results

Bioassay tests presented the remarkable growth inhibition activity of the crude extracts of C. aromaticus cultured cells against the two Aedes mosquitoes. Between the two mosquito species, Ae. albopictus was more susceptible to the crude extracts with lower EI₅₀ values. EI₅₀ of the crude extract of C. aromaticus cultured cells (P4) increased the sterility indices in the parental generation females in both Aedes mosquito species. A significant delay in the pupal formation and adult emergence were observed in the parental generation of the both mosquito species. The sex ratio of the adult population either parental or F1 generation of the Aedes mosquito species was not significantly affected by the EI₅₀ dosage of the crude extract of C. aromaticus cultured P4 cells. A significant decrease in the wing length of the treated adult (female and male) of Aedes aegypti as well as the treated female of Ae. albopictus were observed. Longevity of the adult female of the parental generation of both Aedes mosquitoes as well as females of F1 generation of Ae. albopictus were significantly decreased.

Conclusions

The present study revealed the potential of the crude extract of C. aromaticus cultured cells in controlling vector mosquito populations in the effort to reduce the transmission of vector borne diseases.     

Evaluation of larvicidal activity of Pongamia pinnata extracts against three mosquito vectors

Objective

To evaluate the mosquito larvicidal activity of Pongamia pinnata (P. pinnata) extracts against three mosquito vectors.

Methods

The methanol and hydroalcohol extracts of bark part of P. pinnata L were tested against fourth instar larvae of Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi. The mortality was observed 24 h and 48 h after treatment, data was subjected to probit analysis to determine lethal concentration (LC₅₀ and LC₉₀) to kill 50 and 90 percent of treated larvae of tested species.

Results

The larval mortality was found in both methanol and hydroalcohol extracts of P. pinnata against Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi with LC₅₀ values of 84.8, 118.2 and 151.7 ppm; 97.7, 128.3 and 513 ppm. The highest larval mortality was found in methanol extract of P. pinnata when comparable to the hydroalcohol extract.

Conclusions

These results suggest that both methanol and hyrdoalcohol extracts have the potential to be used as an ideal ecofriendly approach for the control of disease vectors. This could lead to isolation of novel natural larvicidal compounds.     

Larvicidal and repellent potential of Moringa oleifera against malarial vector,Anopheles stephensi Liston (Insecta: Diptera: Culicidae)

Objective

To evaluate the larvicidal and pupicidal potential of the methanolic extracts from Moringa oleifera (M. oleifera) plant seeds against malarial vector Anopheles stephensi (A. stephensi) mosquitoes at different concentrations (20, 40, 60, 80 and 100 ppm).

Methods

M. oleifera was collected from the area of around Bharathiar University, Coimbatore. The dried plant materials were powdered by an electrical blender. From each sample, 100 g of the plant material were extracted with 300 mL of methanol for 8 h in a Soxhlet apparatus. The extracts were evaporated to dryness in rotary vacuum evaporator to yield 122 mg and 110 mg of dark greenish material (residue) from Arcang amara and Ocimum basilicum, respectively. One gram of the each plant residue was dissolved separately in 100 mL of acetone (stock solution) from which different concentrations, i.e., 20, 40, 60, 80 and 100 ppm were prepared.

Results

Larvicidal activity of M. oleifera exhibited in the first to fourth instar larvae of the A. stephensi, and the LC₅₀ and LC₉₀ values were 57.79 ppm and 125.93 ppm for the first instar, 63.90 ppm and 133.07 ppm for the second instar, 72.45 ppm and 139.82 ppm for the third instar, 78.93 ppm and 143.20 ppm for the fourth instar, respectively. During the pupal stage the methanolic extract of M. oleifera showed that the LC₅₀ and LC₉₀ values were 67.77 ppm and 141.00 ppm, respectively.

Conclusions

The present study indicates that the phytochemicals derived from M. oleifera seeds extracts are effective mosquito vector control agents and the plant extracts may be used for further integrated pest management programs.     

Biological activities of Solanum pseudocapsicum (Solanaceae) against cotton bollworm,Helicoverpa armigera Hübner and armyworm,Spodoptera litura Fabricius (Lepidotera: Noctuidae)

ObjectiveTo evaluate the antifeedant, insecticidal and growth inhibition activities of Solanum pseudocapsicum (S. pseudocapsicum) seed extracts against Spodoptera litura (S. litura) and Helicoverpa armigera (H. armigera).MethodsHexane, diethyl ether, dichloromethane and ethyl acetate seed extracts were prepared and tested for antifeedant, insecticidal and growth inhibitory activities against fourth instar larvae of S. litura and H. armigera.ResultsEthyl acetate extract showed promising antifeedant and insecticidal activities against S. litura and H. armigera. Percentage of deformed larvae, pupae and adults were maximum in treatment of ethyl acetate extract. Percentage of successful adult emergence was deteriorated by seeds on extract treated larvae.ConclusionsEthyl acetate extracts of S. pseudocapsicum, showed higher efficiency of antifeedant, insecticidal and growth inhibition activities. Hence, it can be used to controll agricultural insect pests, S. litura and H. armigera.     

Larvicidal efficacy of Ethiopian ethnomedicinal plant Juniperus procera essential oil against Afrotropical malaria vector Anopheles arabiensis (Diptera: Culicidae)

ObjectiveTo screen the essential oil of Juniperus procera (J. procera) (Cupressaceae) for larvicidal activity against late third instar larvae of Anopheles arabiensis (An. arabiensis) Patton, the principle malaria vector in Ethiopia.MethodsThe essential oil of J. procera was evaluated against the larvae of An. arabiensis under the laboratory and semi-field conditions by adopting the World Health Organization standard protocols. The larval mortality was observed for 24 h of post exposure.ResultsThe essential oil of J. procera has demonstrated varying degrees of larvicidal activity against An. arabiensis. The LC₅₀ and LC₉₀ values of J. procera were 14.42 and 24.65 mg/L, respectively under the laboratory conditions, and from this data, a Chi-square value 6.662 was observed to be significant at the P=0.05 level. However, under the semi-field conditions the LC₅₀ and LC₉₀ values of J. procera were 24.51 and 34.21 mg/L, respectively and a Chi-square value 4.615 was significant at the P=0.05 level. The observations clearly showed that larval mortality rate is completely time and dose-dependent as compared with the control.ConclusionsThis investigation indicates that J. procera could serve as a potential larvicidal agent against insect vector of diseases, particularly An. arabiensis. However further studies are strongly recommended for the identification of the chemical constituents and the mode of action towards the rational design of alternative promising insecticidal agents in the near future.     

Larvicidal and irritant activities of hexane leaf extracts of Citrus sinensis against dengue vector Aedes aegypti L.

Objective

To assess the larvicidal and irritant activities of the hexane extracts of leaves of Citrus sinensis (C. sinensis) against the early fourth instars and female adults of Aedes aegypti (Ae. aegypti).

Methods

The larvicidal potential of the prepared leaf extract was evaluated against early fourth instar larvae of Ae. aegypti using WHO protocol. The mortality counts were made after 24 h and LC₅₀ and LC₉₀ values were calculated. The efficacy of extract as mosquito irritant was assessed by contact irritancy assays. Extract-impregnated paper was placed on a glass plate over which a perspex funnel with a hole on the top was kept inverted. Single female adult, 3-day old unfed/blood-fed, was released inside the funnel. After 3 min of acclimatization time, the time taken for the first take-off and total number of flights undertaken during 15 min were scored.

Results

The citrus leaf extracts from hexane possessed moderate larvicidal efficiency against dengue vector. The bioassays resulted in an LC₅₀ and LC₉₀ value of 446.84 and 1 370.96 ppm, respectively after 24 h of exposure. However, the extracts were proved to be remarkable irritant against adults Ae. aegypti, more pronounced effects being observed on blood-fed females than unfed females. The extract-impregnated paper was thus proved to be 7–11 times more irritable as compared with the control paper.

Conclusions

The hexane extracts from C. sinensis leaves are proved to be reasonably larvicidal but remarkably irritant against dengue vector. Further studies are needed to identify the possible role of extract as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the extract could help in formulating strategies for mosquito control.     

Isolation and efficacy of entomopathogenic fungus (Metarhizium anisopliae) for the control of Aedes albopictus Skuse larvae: suspected dengue vector in Pakistan

Objective

To isolate the entomopathogenic fungus Metarhizium anisopliae (M. anisopliae) in the local environment, and evaluate its efficacy against the suspected dengue vector Aedes albopictus in Pakistan.

Methods

According to the standard procedure, M. anisopliae was isolated from the dead mosquitoes which were collected from the field or dead after the collection. Bioassay was performed to determine its efficacy.

Results

The results indicated that M. anisopliae had larvicidal effect with LC₅₀ value 1.09×10⁵ and LC₉₀ value 1.90×10¹³ while it took 45.41 h to kill 50% of tested population.

Conclusions

Taking long time to kill 50% population when compare with the synthetic insecticides, is the only drawback for the use of entomopathogenic fungus but these bio-pesticides are safe for the use.     

Larvicidal efficacies and chemical composition of essential oils of Pinus sylvestris and Syzygium aromaticum against mosquitoes

Objective

To assess the chemical composition and mosquito larvicidal potentials of essential oils of locally sourced Pinus sylvestris (P. sylvestris) and Syzygium aromaticum (S. aromaticum) against Aedes aegypti (A. aegypti) and Culex quinquefasciatus (C. quinquefasciatus).

Method

The chemical composition of the essential oils of both plants was determined using GC-MS while the larvicidal bioassay was carried out using different concentrations of the oils against the larvae of A. aegypti and C. quinquefasciatus in accordance with the standard protocol.

Results

The results as determined by GC-MS showed that oil of S. aromaticum has eugenol (80.5%) as its principal constituent while P. sylvestris has 3-Cyclohexene-1-methanol, .alpha., .alpha.4-trimethyl (27.1%) as its dominant constituent. Both oils achieved over 85% larval mortality within 24 h. The larvae of A. aegypti were more susceptible to the oils [LC₅₀ (S. aromaticum)=92.56 mg/L, LC₅₀(P. sylvestris)=100.39 mg/L] than C. quinquefasciatus [LC₅₀(S. aromaticum)=124.42 mg/L; LC₅₀(P. sylvestris)=128.00 mg/L]. S. aromaticum oil was more toxic to the mosquito larvae than oil of P. sylvestris but the difference in lethal concentrations was insignificant (P>0.05).

Conclusion

The results justify the larvicidal potentials of both essential oils and the need to incorporate them in vector management and control.     

Ovicidal activity of Atalantia monophylla (L) Correa against Spodoptera litura Fab. (Lepidoptera: Noctuidae)

ObjectiveTo evaluate the efficacy of Atalantia monophylla (A. monophylla) leaf in different solvent crude extracts and fractions against eggs of Spodoptera litura (S. litura).MethodsHexane, ethyl acetate and chloroform solvent extracts of A. monophylla leaf and 12 fractions from hexane extract were screened at 5.0%, 2.5%, 1.0% and 0.5% for crude extracts and 1 000, 500, 250 and 125 mg/kg for fractions against the eggs of S. litura for the ovicidal activity. LC₅₀ and LC₉₀ were calculated using probit analysis.ResultsHexane crude extract showed maximum ovicidal activity of 61.94% at 5.0% concentration with a correlation value of r²=0.81, and least LC₅₀ value of 3.06%. Hexane extract was fractionated using silica gel column chromatography and 12 fractions were obtained. Fraction 9 was active which showed maximum ovicidal activity of 75.61% at 1 000 mg/kg with the LC₅₀ value of 318.65 mg/kg and LC₉₀ value of 1 473.31 mg/kg. In linear regression analysis, significant and high correlation (r²=0.81%) was seen between concentration and ovicidal activity of hexane crude extracts and its active fraction.ConclusionsAs per our knowledge, this is the first report for ovicidal activity of A. monophylla against S. litura, A. monophylla could be used for the management of S. litura and other insect pests.     

Bioefficacy of Mentha piperita essential oil against dengue fever mosquito Aedes aegypti L

Objective

To assess the larvicidal and repellent potential of the essential oil extracted from the leaves of peppermint plant, Mentha piperita (M. piperita) against the larval and adult stages of Aedes aegypti (Ae. Aegypti).

Methods

The larvicidal potential of peppermint oil was evaluated against early fourth instar larvae of Ae. aegypti using WHO protocol. The mortality counts were made after 24 and 48 h, and LC₅₀ and LC₉₀ values were calculated. The efficacy of peppermint oil as mosquito repellent was assessed using the human-bait technique. The measured area of one arm of a human volunteer was applied with the oil and the other arm was applied with ethanol. The mosquito bites on both the arms were recorded for 3 min after every 15 min. The experiment continued for 3 h and the percent protection was calculated.

Results

The essential oil extracted from M. piperita possessed excellent larvicidal efficiency against dengue vector. The bioassays showed an LC₅₀ and LC₉₀ value of 111.9 and 295.18 ppm, respectively after 24 h of exposure. The toxicity of the oil increased 11.8% when the larvae were exposed to the oil for 48 h. The remarkable repellent properties of M. piperita essential oil were established against adults Ae. aegypti. The application of oil resulted in 100% protection till 150 min. After next 30 min, only 1-2 bites were recorded as compared with 8-9 bites on the control arm.

Conclusions

The peppermint essential oil is proved to be efficient larvicide and repellent against dengue vector. Further studies are needed to identify the possible role of oil as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the oil could help in formulating strategies for mosquito control.     

Repellent properties of Cardiospermum halicacabum Linn. (Family: Sapindaceae) plant leaf extracts against three important vector mosquitoes

Objective

To determine repellent activity of hexane, ethyl acetate, benzene, chloroform and methanol extract of Cardiospermum halicacabum (C. halicacabum) against Culex quinquefasciatus (Cx. quinquefasciatus), Aedes aegypti (Ae. aegypti) and Anopheles stephensi (An. stephensi).

Methods

Evaluation was carried out in a net cage (45 cm×30 cm×25 cm) containing 100 blood starved female mosquitoes of three mosquito species and were assayed in the laboratory condition by using the protocol of WHO 2005; The plant leaf crude extracts of C. halicacabum was applied at 1.0, 2.5, and 5.0 mg/cm² separately in the exposed area of the fore arm. Only ethanol served as control.

Results

In this observation, the plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity was dependent on the strength of the plant extracts. The tested plant crude extracts had exerted promising repellent against all the three mosquitoes.

Conclusions

From the results it can be concluded the crude extract of C. halicacabum was potential for controlling Cx. quinquefasciatus, Ae. aegypti and An. stephensi mosquitoes.     

Bioactivity of seagrass against the dengue fever mosquito Aedes aegypti larvae

Objective

To identify the larvicidal activity of the seagrass extracts.

Methods

Seagrass extracts, Syringodium isoetifolium (S. isoetifolium), Cymodocea serrulata and Halophila beccarii, were dissolved in DMSO to prepare a graded series of concentration. Batches of 25 early 4th instars larvae of Aedes aegypti (Ae. aegypti) were transferred to 250 mL enamel bowl containing 199 mL of distilled water and 1 mL of plant extracts (0.01 mg – 0.1 mg). After 24 h the mortality rate was identified with the formulae [(% of test mortality – % of control mortality)/(100 – % of control mortality)] × 100. Each experiment was conducted with three replicates and a concurrent control group. A control group consisted of 1 mL of DMSO and 199 mL of distilled water only.

Results

: The root extract of S. isoetifolium showed maximum larvicidal activity with minimum concentration of extract of LC₅₀= 0.0 604 ± 0.0 040)µg/mL with lower confidence limit (LCL) – upper confidence limit (UCL) = (0.051–0.071) and LC₉₀=0.0 972µg/mL followed by leaf extract of S. isoetifolium showed LC₅₀= (0.062 ± 0.005)µg/mL. The regression equation of root and leaf extract of S. isoetifolium for 4th instar larvae were Y= 4.909 + 1.32x (R²= 0.909) and Y= 2.066 + 1.21x (R² =0.897) respectively. The results of the preliminary phytochemical constituents shows the presence of saponin, steroids, terpenoid, phenols, protein and sugars.

Conclusions

From the present study the ethanolic extracts of seagrass of S. isoetifolium possesses lead compound for development of larvicidal activity.     

凤梨科植物叶腋中蚊类和无脊椎动物的种类组成及其对白纹伊蚊的生存影响(英文)

目的 凤梨科植物(家族:凤梨科)在佛罗里达东北部的住宅景观中普遍存在。众所周知,许多凤梨科植物能保持水分不流失,可为各种疾病媒介蚊类和其他无脊椎动物提供幼虫栖息地。本研究的目的是调查凤梨科植物上的幼虫繁殖状况及其对病媒蚊生存的可能影响。方法 对凤梨科植物进行采集和取样,收集蚊幼虫和其他无脊椎动物,并在显微镜下鉴定种类。以蚊幼虫和凤梨科植物为实验对象,研究成年蚊类在植物上的生存状况。结果 在佛罗里达州东北部圣约翰县的13个地点监测了蚊类的种类。2015年4月—2016年7月期间,从凤梨科植物叶腋上收集了Aedes aegypti Linn.、Aedes albopictus Skuse、Culex quinquefascaitus Say、Wyeomyia mitchelli Theobald和Toxorhynchites r. rutilus Coquillett的幼虫。在被调查的80%的居住地点的凤梨科植物上积水中发现了白纹伊蚊和致倦库蚊两种蚊的幼虫,在几处地点的植物叶腋中发现了八种不同的无脊椎动物。结论 凤梨科植物是白纹伊蚊、其他蚊类和几种无脊椎动物的繁殖地。尽管蚊类可能会利用凤梨科植物来作为栖息地,实验证明,完整或受损的凤梨叶不是成年白纹伊蚊生存的主要营养来源。     

广州大学城2020年白纹伊蚊幼虫及成蚊抗药性调查

目的 了解广州大学城登革热媒介白纹伊蚊幼虫及成蚊对常用杀虫剂的抗药性现状,为制定针对性防控策略提供参考.方法 分别在广州大学城一期和二期校区采集白纹伊蚊幼虫,在实验室条件下繁殖一代,分别采用幼虫浸渍法和成蚊接触筒药膜滤纸接触法对4类4种幼虫药物和4类9种成蚊药物进行敏感性测定,并运用SPSS25.0进行统计学分析.结果...     

基于斑马鱼幼鱼模型的甘遂毒性评价

[目的]以模式生物斑马鱼幼鱼为模型,评价甘遂不同溶剂连续提取物毒性差异及毒性特征。[方法]采用索氏提取法获得甘遂不同溶剂连续提取物。通过预实验,确定各提取物72 h最大不致死浓度和最小全致死浓度。在此区间设定6~8个药物浓度,建立致死曲线,计算半数致死浓度（LC₅₀）。以毒性最大提取物的10%致死浓度（LC₁₀）、最小致死浓度（LC₁）、1/3 LC₁和1/10 LC₁为给药浓度,同时设立空白组和溶剂对照组,连续给药72 h,观察甘遂毒性特征。停药后将幼鱼置于养殖水中恢复48 h,观察毒性可逆性。[结果]甘遂不同提取部位毒性顺序为石油醚 > 二氯甲烷 > 乙酸乙酯 > 乙醇提取物。甘遂的主要毒性为肝毒性和胃肠道刺激性。肝毒性既可造成肝肿大,又可导致肝变性,肝肿大不可逆,而肝变性具有可逆性。[结论]本实验首次利用单个模型以相同浓度单次给药,同时评价了甘遂对心脏、肝脏、肾脏、神经系统和胃肠道等脏器系统的毒性作用及可逆性。实验结果证实了甘遂的毒性集中于石油醚提取部位,并可对肝脏和胃肠道造成实质性损伤。本实验为斑马鱼模型在中药毒性评价中的应用提供了参考。     

中华按蚊和白纹伊蚊涎腺及血淋巴中蛋白质的PAGE分析

比较研究了中华按蚊初羽化和吸血后的涎腺及血淋巴中蛋白质的PAGE分析。结果表明,初羽化的两种蚊虫涎腺及血淋巴蛋白质区带分别为9和15条,8和22条。吸血第12d涎腺蛋白区带分别为9和8条。吸血第5d血淋巴蛋白区带分别是15条和26条。初羽化中华按蚊和白纹伊蚊血淋巴脂蛋白区带分别有2条和4条。     

Ovicidal and repellent activities of botanical extracts against Culex quinquefasciatus,Aedes aegypti and Anopheles stephensi (Diptera: Culicidae)

Objective

To determine the ovicidal and repellent activities of methanol leaf extract of Ervatamia coronaria (E. coronaria) and Caesalpinia pulcherrima (C. pulcherrima) against Culex quinquefasciatus (Cx. quinquefasciatus), Aedes aegypti (Ae. aegypti) and Anopheles stephensi (An. stephensi).

Methods

The ovicidal activity was determined against three mosquito species at various concentrations ranging from 50-450 ppm under the laboratory conditions. The hatch rates were assessed 48 h after treatment. The repellent efficacy was determined against three mosquito species at three concentrations viz., 1.0, 2.5 and 5.0 mg/cm² under the laboratory conditions.

Results

The crude extract of E. coronaria exerted zero hatchability (100% mortality) at 250, 200 and 150 ppm for Cx. quinquefasciatus, Ae. aegypti and An. stephensi, respectively. The crude extract of C. pulcherrima exerted zero hatchability (100% mortality) at 375, 300 and 225 ppm for Cx. quinquefasciatus, Ae. aegypti and An. Stephensi, respectively. The methanol extract of E. coronaria found to be more repellenct than C. pulcherrima extract. A higher concentration of 5.0 mg/cm² provided 100% protection up to 150, 180 and 210 min against Cx. quinquefasciatus, Ae. aegypti and An. stephensi, respectively. The results clearly showed that repellent activity was dose dependent.

Conclusions

From the results it can be concluded the crude extracts of E. coronaria and C. pulcherrima are an excellent potential for controlling Cx. quinquefasciatus, Ae. aegypti and An. stephensi mosquitoes.     

Laboratory assessment of the molluscicidal and cercariacidal activities of Balanites aegyptiaca

Objective

To assess the molluscicidal and cercariacidal activities of aqueous extracts of Balanites aegyptiaca (B. aegyptiaca) against Ethiopian Biomphalaria pfeifferi (B. pfeifferi), Lymnaea natalensis (L. natalensis) and Schistosoma mansoni (S. mansoni) cercariae.

Methods

Extracts of seeds, endocarp, mesocarp, and fruit of B. aegyptiaca were tested for their activities against adult B. pfeifferi and L. natalensis. The cercariacidal activity of the seeds of the plant was also evaluated against S. mansoni. Bioassays were carried out following the methods recommended by WHO. Snail mortalities were compared between each plant part and snail species, and LC₅₀ and LC₉₀ values for the plant parts tested were computed. The cercariacidal activity of the plant was assessed by exposing the mice to the cercariae pre-exposed to aqueous extract of B. aegyptiaca seeds.

Results

For the molluscicidal activities of seeds, endocarp, mesocarp and whole fruit, the LC₅₀ values against B. pfeifferi were 56.32, 77.53, 65.51 and 66.63 mg/L, respectively, while the respective LC₉₀ values were 77.70, 120.04, 89.50 and 97.55 mg/L. Similarly, the LC₅₀ values for the seeds, endocarp, mesocarp and whole fruit against L. natalensis were 80.33, 92.61, 83.52 and 87.84 mg/L, respectively, while the respective LC₉₀ values were 102.30, 138.21, 115.42 and 127.69 mg/L. B. pfeifferi were found to be more susceptible to B. aegyptiaca than L. natalensis. S. mansoni cercariae exposed to 15 mg/L of extract of seeds were incapable of infecting mice. The mean egg load of tissue was reduced in mice infected with the cercariae exposed to 5 and 10 mg/L of the extract.

Conclusions

The aqueous extracts of different parts of B. aegyptiaca exhibited reasonable molluscicidal activity against B. pfeifferi and L. natalensis, as well as cercariacidal activity against S. mansoni cercariae. However, comprehensive laboratory evaluation is recommended prior to field tests of the plant parts since their impact on other aquatic biota is not known.     

The biology and demographic parameters of Aedes albopictus in northern peninsular Malaysia

Objective

To generate life table characteristics for the dengue vector Aedes albopictus (A. albopictus) under uncontrolled conditions, incorporating both the aquatic and the adult stages.

Methods

Ten females derived from wild pupae were allowed to fully blood-feed on restrained mice. 774 eggs were hatched in seasoned water. F1 larvae were followed for development until their F2 counterparts emerged as adults. Some population parameters were monitored (F1) or estimated (F2).

Results

A. albopictus exhibited increased fecundity and egg hatch success. Immature development was quick. Immature survival was high, with lowest rate in the pupal stage. Adult emergence was about 81% and sex ratio was close to 1:1. Generational mortality (K) was about 28%. A high proportion of females completed a reproductive cycle and the obtained parity rate was predicted to lead to higher fecundity in the next generation.

Conclusions

It can be concluded that natural A. albopictus populations in Penang seem largely determined by quick development in combination with low immature loss and increased oviposition.