Effects of natural pyrethrum and synthetic pyrethroids on the tiger mosquito,Aedes albopictus (skuse) and non-target flower-visiting insects in urban green areas of Padua,Italy

Abstract

The tiger mosquito is a key vector of several human diseases and is considered a public health concern worldwide. The implementation of strategies aimed at maximizing mosquito control without affecting non-target insect groups is of major importance. In a field trial, we tested the efficiency of a natural pyrethrum-based vs. a synthetic pyrethroid-based insecticide in reducing tiger mosquito population and how they affect the diversity of non-target flower-visiting insects in green urban areas. Only the pyrethroid insecticide was effective in reducing mosquito abundance, although its effects disappeared nine days after application. The two adulticides did not significantly affect the diversity of flower-visiting insects, probably because of their large body size and the difference in flying and foraging activity. To effectively control mosquito populations while preventing intoxication of non-target flower-visiting insects, adulticide applications should be applied early in the morning and only on bushes and trees. Results from our small-scale applications cannot be extrapolate when larger areas are treated.     

Non-target toxicology of a new mosquito larvicide, trypsin modulating oostatic factor

Trypsin modulating oostatic factor (TMOF), a peptide hormone originally isolated from the ovaries of adult Aedes aegypti, is currently under commercial development as a new pesticide chemistry with a novel mode of action for the control of larval mosquitoes. The objective of the current research is to evaluate potential risks of the use of TMOF as an insecticide on non-target organisms. TMOF (YDPAP₆) was degraded in vitro (as determined by HPLC and LC/MS) to DPAP₆, PAP₆, and then AP₆ by leucine aminopeptidase, a pancreatic enzyme found in the digestive system of vertebrates. The rate of degradation of TMOF and PAP₆ was significantly greater than that of DPAP₆, while no metabolism of AP₆ was found. TMOF technical insecticide was produced on a commercial scale by recombinant yeast (heat-killed before application). The technical TMOF when administered in a single dose by gavage to male and female mice at 2000 mg dry weight/kg body weight produced no negative effects as compared to controls up to 12 days after treatment. When male and female mallard ducks were treated by gavage with 1250 mg dry weight of technical TMOF/kg body weight each day for 5 days, again no toxic effects were noted through 35 days after the last treatment. TMOF technical insecticide was also applied to the shaved skin of male and female rabbits at the rate of 2000 mg/kg for 1-2 days, with no effect. The end point observations in these in vivo experiments were mortality; changes in growth rate, behavior, body structure, and color; and possible lesions observed during necropsy. Finally, Daphnia incubated with technical TMOF in rearing water at the level of 1.0 × 10⁶ yeast cells/ml (10 mg/ml) also demonstrated no negative effects on mortality, growth, molting, time to first brood, and production of viable neonates. It appears from these studies that TMOF can be degraded by vertebrate digestive proteases and technical TMOF is not toxic to the non-target organisms examined.     

食蚊鱼白内障的研究初报

采用定期观察方法,了解食蚊鱼白内障的发生过程以及由此导致的外部形态和行为的变化情况。研究的食蚊鱼群体的白内障有较高的发生率,白内障鱼一般体色晦暗,经常浮于水面缓慢游动;其摄食和生长也受较大影响。食蚊鱼白内障大多是双眼同时发生的,眼球可见不同程度的浑浊。从外观形态区分,食蚊鱼白内障主要有两种类型,一种是绕核性白内障,另一种无法看到晶状体形状,表现为整个眼球的不透明。对病鱼的眼球等进行组织病理观察,发现病理变化部位主要在晶体,所有病例的晶状体纤维都出现病理变化,最普遍的是晶状体皮质区纤维不同程度变性或断裂;晶状体上皮细胞有脱落、增生等。食蚊鱼白内障为鱼类白内障研究提供良好材料。     

Mosquito-killing water molds isolated from soil samples collected in Taiwan

Mosquito-killing water molds were isolated from soils collected from various parts in Taiwan. The first-instar larvae of Aedes aegypti and Aedes albopictus were used as baits. A total of 453 soil samples were collected from Taipei, Ilan, Hualien, Taoyuan, Hsinchu, Miaoli, Taichung, Tainan, Nantou, Chiayi, Yunlin and Pintung. Four mosquito-killing Pythium spp. and one Saprolegnia sp. were isolated from the soil samples. Using zoospores of the Pythium spp. as inoculum to infect the first-instar larvae, scanning electron micrographs showed that most zoospores attached in the anal gill and a few attached between head and thorax. Thus, Pythium spp. is a potential biocontrol agent against first-instar larvae of A. aegypti and A. albopictus.     

Toxicity of novel aromatic and aliphatic organic acid and ester analogs of trypsin modulating oostatic factor to larvae of the northern house mosquito, Culex pipiens complex, and the tobacco hornworm, Manduca sexta

Eight non-peptidic chemical analogs of trypsin modulating oostatic factor (TMOF, NH₂-YDPAP₆), an insect hormone inhibiting trypsin biosynthesis in mosquitoes, were synthesized based on the structure of the native peptide. The median lethal concentration (LC₅₀) for the chemical analogs, TMOF and FDPAP (a peptidic analog of TMOF) was estimated for larvae of the northern house mosquito, the Culex pipiens complex, using a static 5-day bioassay. Four of these compounds demonstrated the same larvicidal activity as TMOF, while three of these compounds were 1.2-2.5-fold more active than TMOF. The compounds introduced by injection were toxic to fourth instars of the tobacco hornworm, Manduca sexta, except for TMOF, FDPAP, and PPHEN. Injection of TMOF and FDPAP into fourth stadium and TMOF into second stadium M. sexta had no effect on trypsin activity, growth, or mortality. Apparently the mosquito hormone is inactive in the tobacco hornworm at the developmental stages examined. Three TMOF analogs (CHEA, PHEA, and PHA) demonstrating the highest activity by injection in M. sexta were also found to be toxic by injection in fourth instars of the tobacco budworm, Heliothis virescens, and the cotton bollworm, Helicoverpa zea, as well as adult male German cockroaches, Blattela germanica. A two-choice feeding bioassay with H. virescens indicated that at least one of the TMOF analogs, PHEA, has anti-feeding properties.     

Evidence of West Nile virus seropositivity in wild birds on the island of Cyprus

West Nile Virus (WNV)¹ is an emerging pathogen in Cyprus, with the first human case of infection reported in 2016, and another documented in 2018. A cluster of cases in humans was then reported in 2019. However, little is known regarding which avian species might bring WNV to Cyprus. Here, we investigated seroprevalence of WNV antibodies in migratory and resident birds, captured across Cyprus to assess to what extent human populations might be exposed to WNV. We used Enzyme-Linked Immunosorbent Assay (ELISA)² to test for the presence of WNV antibodies in 836 avian blood samples of 44 species captured between 2015 and 2020. A seropositivity rate of 1.3 % was found. The majority of seropositive wild birds belonged to the migratory species Sylvia atricapilla, a common and widespread migrant, implying a high risk of WNV being introduced throughout Cyprus.     

2011～2014年华东四地区口岸蚊类监测报告

[目的]掌握华东四地区口岸蚊类种群构成、分布、密度、季节消长和携带病原体情况,为蚊类的口岸防治提供基础数据.[方法]采用CO2诱蚊器、集卵器法、捞勺法、目测法对华东四地区口岸蚊类进行调查,对捕获蚊类进行分类鉴定和病原体检测.[结果]2011～2014年本底共捕获蚊类102 583只,隶属于1科6属18种,以致倦库蚊/淡色库蚊为优势种.5～10月均可捕获蚊类,以6月为高峰者最多.集卵器法阳性率为9.41％,孳生地阳性率为7.23％.入境截获蚊类数量较少,以淡色库蚊为主.登革热、疟疾等病原体检测均为阴性.[结论]华东四地区口岸以致倦库蚊/淡色库蚊为优势种,6月为高峰,口岸存在蚊类孳生环境,应在今后的防控工作中作为重点对象.     

不同方法提取驱蚊香草精油中化学成分的比较

[目的]比较不同方法提取的驱蚊香草精油的化学成分。[方法]应用GC/MS分别对2种方法提取的精油进行分离和检测。[结果]在水蒸气蒸馏法提取的精油中检测到23个成分,在有机溶剂法提取的精油中检测到49个成分;精油的主要成分为香茅醇、马兜铃烯、乙酸香茅酯、香叶醇、芳樟醇、异薄荷酮、β-波旁烯和香榧烯醇等。[结论]水蒸气蒸馏法使驱蚊香草精油化学成分大量损失,但对沸点高、相对难挥发的主要化学成分有很好地富集作用;有机溶剂提取法能很好地保留驱蚊香草精油的化学成分。     

Fire fighting truck-based emergency mosquito biolarviciding to prevent outbreaks of malaria and arboviral disease in Kabul, Afghanistan

Emergency control of disease vectors requires high efficacy, rapid reaction and safe use of biocides in order interrupt transmission cycles without harming humans, non-target animals and the environment. In countries with complex emergencies, air-borne large-scale vector control is often limited, or impossible, due to questionable security as well as military, safety, equipment, or logistical constraints. While facing a potential outbreak of malaria and dengue fever in the Kabul area, Afghanistan, combined with high abundance of anopheline and Culex mosquitoes, emergency mosquito larvae control with Bacillus thuringiensis var. israelensis (Bti) and methoprene were carried out. For the first time, larvicides were applied by using a modern fire fighting truck in combination with aerial imaging of potential breeding sites. Three treatments with 0.07 g a.i. sterilized, water-dispersible granular (WDG) Bti/m² in combination with 0.0014 g a.i. methoprene/m², or 0.07 g a.i. Bti/m² alone, were conducted on July 29, August 29, and September 28, 2004, and significantly reduced larval indexes of 96.5 (P < 0.0001), 96.7 (P < 0.0001), and 97.6% (P < 0.0001) against anopheline, and 98.2 (P < 0.0001), 95.6 (P < 0.0001), and 96.2% (P < 0.0001) against Culex larvae, respectively. Before the larviciding campaigns started, up to 222.4 ± 32.0 mosquitoes were captured per standardized light trap per night. During May until October 2004, the following anopheline and Culex species were abundant: A. superpictus (29.3%), A. fluviatilis (17.0%), C. pipiens (15.2%), and C. pseudovishnui (38.5%). After biolarviciding, abundance of adult mosquitoes, as measured by light trap catches 20 days post-treatment, decreased significantly in Anopheles at 81.4 (P < 0.0001), 87.1 (P < 0.0001), and 78.2% (P = 0.01), and in part significantly in Culex for 75.2 (P < 0.0001), 78.3 (P < 0.0001), and 30.8% (P = 0.463), respectively. After the treatment, mosquito-associated annoyance complaints and disease transmission decreased markedly, and not a single confirmed case of malaria or arbovirosis was reported. It is concluded that biolarviciding using a fire fighting truck as the application device is a highly successful, rapid, and cost-effective method to control vector mosquito larvae, and to reduce human exposure to mosquito-borne diseases during complex emergency situations.