Pathogenicity of Leptolegnia chapmanii and other oomycetes from Argentina against Aedes aegypti and Aedes albopictus larvae from Misiones Province: potential for biological vector control

Plastic pollution and infectious diseases

The ongoing Zika virus outbreak, which briefly threatened to put a stop to the 2016 Olympic Games in Brazil, has again focused attention on the threat of vector‐borne diseases. One efficient strategy to battle such diseases, now underway in Brazil to fight the Zika virus, is to kill the insects that carry the pathogen. Vector control has been practised with varying effectiveness for at least half a century, especially for malaria; the Brazil outbreak again highlights the need for integrating existing methods including the use of insecticides, vaccines, drugs and low technology such as sanitation to keep insect vectors at bay. In addition, new approaches are being developed based on sophisticated methods such as genome editing of the insect vector and deliberate infection of mosquitoes with the Wolbachia bacteria. However, attempts to scale up these new methods from field trials to deployment have been slowed down or halted by environmental concerns or public resistance against genetically modified organisms. The Zika outbreak in South America has stimulated cross‐border collaboration of public health authorities and increased pressure to use new integrative approaches that are essential for combatting vector‐borne diseases. The irony is that the Zika virus itself has a minimal global impact compared with other insect‐borne pathogens, but it has attracted enormous publicity because of the risk of causing microcephaly in unborn children, combined with the coincidence of the outbreak during the Olympic year. The exact risk for the foetus is as yet unknown [1], but it is clear that Zika is otherwise a relatively mild disease with no symptoms in the majority of cases (http://www.cdc.gov/zika/symptoms/index.html). By contrast, other mosquito‐borne diseases, including malaria, yellow fever, dengue and chikungunya (CHIKV), are major causes of both mortality and morbidity, responsible for hundreds of millions of cases each year and millions of deaths …

Hatching pattern and coexistence of Aedes aegypti and Aedes albopictus (Culicidae) in a subtropical city, Argentina, after three decades of coexistence

ABSTRACTThe Asian tiger mosquito ( Aedes albopictus, Diptera: Culicidae) has spread rapidly in the last 30 years from its native region in Southeast Asia. In Argentina, studies on its potential distribution suggest that this species could be found in temperate zones of the province of Buenos Aires. However, since its initial detection in 1998 Ae. albopictus is bounded to the subtropical province of Misiones. To evaluate the presence and abundance of Ae. albopictus in the Northeast of Argentina, we preliminarily evaluated the presence of this vector by analyzing its presence in tires of 20 cities belonging to the province of Misiones and four cities in Northern Corrientes, and then performed an evaluation of the vector in the towns where the vector was detected. Aedes albopictus was present only in two cities of Misiones: Eldorado and Colonia Aurora. Aedes aegypti and Ae . albopictus accounted for 86% of the individuals collected in the domiciles of both towns. In Colonia Aurora both species were in similar abundances suggesting a co-dominance. The present study extends the austral distribution of Ae. albopictus in Argentina to the city of Colonia Aurora where the highest abundance recorded in Argentina was detected. Nevertheless, the reasons of its bounded distribution in the region are not known.

BackgroundThe Aedes aegypti mosquito is the vector for dengue fever, yellow fever, chikungunya, and zika viruses. Inadequate vector control has contributed to persistence and increase of these diseases. This review assesses the evidence of effectiveness of different control measures in reducing Aedes aegypti proliferation, using standard entomological indices.MethodsA systematic search of Medline, Ovid, BVS, LILACS, ARTEMISA, IMBIOMED and MEDIGRAPHIC databases identified cluster randomised controlled trials (CRCTs) of interventions to control Aedes aegypti published between January 2003 and October 2016. Eligible studies were CRCTs of chemical or biological control measures, or community mobilization, with entomological indices as an endpoint. A meta-analysis of eligible studies, using a random effects model, assessed the impact on household index (HI), container index (CI), and Breteau index (BI).ResultsFrom 848 papers identified by the search, eighteen met the inclusion criteria: eight for chemical control, one for biological control and nine for community mobilisation. Seven of the nine CRCTs of community mobilisation reported significantly lower entomological indices in intervention than control clusters; findings from the eight CRCTs of chemical control were more mixed. The CRCT of biological control reported a significant impact on the pupae per person index only. Ten papers provided enough detail for meta-analysis. Community mobilisation (four studies) was consistently effective, with an overall intervention effectiveness estimate of −0.10 (95%CI -0.20 – 0.00) for HI, −0.03 (95%CI -0.05 – -0.01) for CI, and −0.13 (95%CI -0.22 – -0.05) for BI. The single CRCT of biological control had effectiveness of −0.02 (95%CI -0.07– 0.03) for HI, −0.02 (95%CI -0.04– -0.01) for CI and −0.08 (95%CI -0.15– -0.01) for BI. The five studies of chemical control did not show a significant impact on indices: the overall effectiveness was −0.01 (95%CI -0.05– 0.03) for HI, 0.01 (95% CI -0.01– 0.02) for CI, and 0.01 (95%CI -0.03 – 0.05) for BI.ConclusionGovernments that rely on chemical control of Aedes aegypti should consider adding community mobilization to their prevention efforts. More well-conducted CRCTs of complex interventions, including those with biological control, are needed to provide evidence of real life impact. Trials of all interventions should measure impact on dengue risk.

Important arboviruses for public health such as Dengue, Zika, and Chikungunya are transmitted by mosquito vectors, primarily Aedes aegypti and Aedes albopictus. The control of populations of these mosquitoes can be carried out by mechanical, chemical, and biological control. In view of the environmental impacts caused by synthetic chemical insecticides, the search for botanical larvicides with larvicidal potential has intensified. The objective of this work is to investigate the occurrence of acetylcholinesterase inhibition and histopathological alterations in Aedes aegypti and Aedes albopictus submitted to treatment with the ethanolic extract of the leaves of Acmella oleracea as possible mechanisms of larvicidal action. Larvae of Aedes aegypti and Aedes albopictus were exposed to treatment with the ethanolic extract of Acmella oleracea for an exposure period of 24 hours. After this time, larval mortality was recorded, and the larvae were separated in order to investigate the mechanisms of action. The ethanolic extract of Acmella oleracea had an LC50 of 29.15 µg.mL-1 and 16.00 µg.mL-1 against Aedes aegypti and Aedes albopictus, respectively. Significant reductions in acetylcholinesterase activity were observed in larvae treated with the ethanolic extract of Acmella oleracea, as well as histopathological changes in the midgut of treated larvae, including loss of integrity of the intestinal epithelium, vacuolation of the cell cytoplasm, and disruption of the peritrophic matrix. These results suggest that that the mechanism of action of the ethanolic extract of Acmella oleracea against Aedes larvae includes the potential to inhibit acetylcholinesterase and cause histopathological alterations in the midgut.

When a bacterium fights arboviruses

A series of aromatic thiosemicarbazone-oxime [TP1 and TP2] derivatives and their Ni(II), Cu(II), and Co(II) complexes were synthesized, and their larvicidal activity was evaluated against Aedes aegypti and Aedes albopictus larvae. The efficacy of these substances to Aedes albopictus larvae has been demonstrated for the first time. Laboratory colonized Aedes aegypti and Aedes albopictus larvae were subjected to larvicidal activity tests. Larval mortality rates at 24 and 48 hours were recorded and LC50 values were calculated. The study was carried out at Aydın Adnan Menderes University in 2021. For Aedes aegypti, LC50 of TP1 and its Co(II) complex were 15.41, 9.75, μg/mL whereas for TP2 and its Co(II) complex, LC50 were 21.62, 20.50 μg/mL after 24 and 48 h respectively. For Aedes albopictus, TP1 and its Co(II) complex showed an LC50 of 12.06, 8.75 μg/mL, whereas TP2 and its Co(II) complex showed an LC50 of 32.87, 25.48 μg/mL, for 24, and 48 h respectively. Both TP1 and TP2 compounds and their Co(II) complexes presented high efficacy against the larvae; it can be said that C=S groups in thiosemicarbazone derivatives are effective in showing activity and for this reason, studies should be continued to make these components effective.

Introduction: Biological control is a component of the integrated vector control strategy. Its aquatic habitat, which is safe for non-target organisms and appropriate for coexistence with target organisms and predators without the presence of predator’ enemies, is its limitation in terms of mosquito larval control. Methods: A predator Toxorhynchites splendens second instar larva was used in this study to consume immature stages of the second and third instars of Anopheline stephensi Culex quinquefasciatus and Aedes aegypti. The immature stages were raised in a rectangular enamel-coated tray that measured 17 x 12 x 6 inches and was filled with enough chlorinefree water in a lab at the Institute of Vector Control and Zoonoses (IVCZ), Hosur. To assess the predator's effectiveness, the number of preys it consumed was noted. A nonparametric ANOVA was used to model the relationship between three distinct prey intakes and time. Results: This led to finding that Anopheles stephensi, the malaria vector, was the predator's first choice in order of preference, followed by Culex quinquefasciatus, the vector of filaria, and Aedes aegypti, the vector of dengue. It became clear that the predator prioritized the Anopheles stephensi larvae as its primary source of food even all three of these types were present altogether. Conclusion: The potential predator of Anopheles stephensi larvae, which is the malaria vector, is larvae Toxorhynchites splendens, a non-blodd sucking mosquito species. How to cite this article:Basker P. Predation Efficiency of Non-Blood Sucking Mosquito Larvae of Toxorhynchites splendens (Weidman) Determined by Kruskal–Wallis One-Way Analysis of Variance by Ranks over Immature Stages of Malaria (Anopheles stephensi), Filariasis (Culex quinquefasciatus) and Dengue (Aedes aegypti) Vectors. J Commun Dis. 2024;56(3):127-130. DOI: https://doi.org/10.24321/0019.5138.202457

Aedes aegypti is the main transmitter of dengue hemorrhagic fever which is an important health problem in Indonesia and the world. The main vector of dengue hemorrhagic fever (DHF) is the Aedes aegypti mosquito which originated from Africa and discovered in Indonesia in 1968 in Surabaya. DHF continues to spread to all 472 districts or cities in 34 provinces in Indonesia. Data on dengue cases recorded until the 49th week of 2020 were 95,893 cases and 661 cases of death. Biological control using natural ingredients which is Asteraceae family plants that have larvicidal activity is one of the methode to prevent transmission and reproduction of the main vector. The object of this study is to know the potential of Asteraceae family plants as larvicides against Aedes aegypti. The method of this study is systematic review. The data sources used are secondary data obtained from Google Scholar. The keywords are Asteraceae, Aedes aegypti and larvicide. There are 17 literatures which fulfill the criteria. Synthesis of data is using SPIDER. The result of this study is, from 17 international and national journals reviewed, there were 9 (52,95%) journals shows that Asteraceae family plants have low potential to become Aedes aegypti larvicides and 8 (47,05%) journals shows that Asteraceae family plant have the potential to become Aedes aegypti larvicides, this is based on the LC50 value >1000ppm which indicates that the larvicidal activity is low. Asteraceae family plants have low potential to become Aedes aegypti larvicides.

The concern for environmental safety and increased development of resistance to chemical insecticides by major arthropod vectors is rekindling interest in the search for botanical products that may be used against major vectors. Essential oils of 11 local plants were evaluated for larvicidal activities against laboratory colonies ofAnopheles arabiensis and Aedes aegypti early fourth instar larvae. Those oils which induced higher larvicidal activities in the laboratory were also evaluated in the field. In the laboratory, the LC50 values of the oils ranged from 17.5 to 85.9 ppm againstA. arabiensis and from 9.1 to 67.8 ppm against A. aegypti. Similarly, the LC90values of the oils ranged from 33.2 to 128.4 ppm and from 14.3 to 96.4 ppm against the respective mosquito species. However, Chenopodium ambrosioides Linnaeus oil with LC50 of 17.5 and 9.1 ppm against A. arabiensis and A. aegypti, respectively, and Ocimum lamiifolium Hochst oil with LC 50 of 20.9 and 8.6 ppm against A. arabiensis and A. aegypti, respectively, were the most effective oils. A. aegypti,were more sensitive to most oils than A. arabiensis larvae. Of the five essential oils which exhibited relatively strong larvicidal effects in the laboratory and further tested in the field against wild-collected anopheline larvae, the LC50 and LC 90 values ranged from 35 to 110 ppm, and from 63.7 to 162.9 ppm, respectively. O. lamiifolium and C. ambrosioides still induced the highest larvicidal effects with LC50= 34 ppm; LC90 = 97. 9 ppm and LC50 = 47.3 ppm; LC90 = 97.9 ppm, respectively. However, it was revealed that laboratory bred mosquito larvae were more sensitive to the essential oils than wild-collected larvae. Key words: Anopheles arabiensis, Aedes aegypti, essential oils, botanical larvicides.

Biological vector control by using larvivorous fish will be beneficial in reducing Aedes aegypti population, hence reducing risk of dengue virus transmission. It is important to select the larvivorous fish according to its digestive organ.Current study aimed to investigate the predation potential among the fish species and to identify the influence of the digestive tract length of the fish related to their predation potential. The research was an analytical observational study with post-test only design. Third stage larvae of Aedes aegypti were used as preys for tilapia (Oreochromis niloticus), common carper (Cyprinus carpio), and guppy (Poecillia reticulata). In association with their digestive tract length, predation potential of tilapia, common carper, and guppy showed statistical differences (P<0.05). Tilapia demonstrated highest predation of the larvae, followed by common carper and guppy. There are associations between difference in shapes of mouth and intestines, mouth width, intestinal length, and predation potential of these fish species. Current study results showed possible associations between digestive tract length of tilapia, common carper and guppy and predation potential on Aedes aegypti larvae, allowing these fish species to be used inbiological control of Aedes aegypti.

Dengue Control: The Challenge Ahead

Aedes aegypti and Aedes albopictus are known vector mosquitoes for several emerging arthropod-borne viruses (arboviruses) including dengue fever, chikungunya, Zika fever, Mayaro and yellow fever viruses across the world. Aedes species vector mosquitoes are blamed for the spread of dengue and chikungunya in India. Dengue and Chikungunya is the illustrious public health problems in the country, dengue has public health importance and cumulative burden to the affected community, especially in the Southern States of India, since 1991, and followed by the highest outbreaks of chikungunya in the Southern India, 2006. Dengue cases reported from 24 States and 3 Union Territories out of 34 States / Union Territories in India, and highest reports recorded in 5 major States (Tamil Nadu, Kerala, Karnataka, Punjab and West Bengal), during 2017. All the four serotypes of dengue virus (DEN-1, DEN-2, DEN-3, and DEN-4) are detected across the country various with space and time. Mapping the geographical distribution and seasonal variation of dengue and chikungunya vector mosquitoes (Aedes aegypti and Aedes albopictus) is absolutely significant for the systematic surveillance, organization, and implementation, accordingly, the public health authority possibly will make prevention measures to control the dengue epidemic earlier in advance and monitoring the endemic situation in the state as well as in the country, continuously [16,17,18]. Aedes aegypti and Aedes albopictus vector mosquito’s density caused by the man-made containers (socio-economic variables), and the natural breeding habitats, and land use / land cover types, environmental risk factors, and climate determinants. All the four serotypes of dengue virus (DEN-1, DEN-2, DEN-3, and DEN-4) are reported in India. The study has mainly focused on the major endemic districts in India, where the state of endemic has accumulative problems, and is grumbling the community. Aedes aegypti and Aedes albopictus are the known vector mosquitoes of dengue and chikungunya. The endemic districts have unique landscape terrain and land use / land cover pattern, and climate factors (precipitation, temperature, relative humidity, and saturation deficiency). The major landscape terrain has hilly, plain and coastal areas. The epidemic areas receive rainfall by both the southwest monsoon and the northeast monsoon from April to November (almost 8 months), and has the average temperature range of 22°C to 31°C, and relative humidity of 70 % to 90 %, and the present study contains the vector density is highly influenced by the maximum number of rainy days, and the occurrences of dengue epidemics clustered regions in India mainly where it receives annual mean rainfall ranging from 300 mm to 1200 mm. The spatial distribution and seasonal variation of vector mosquitoes (Aedes aegypti and Aedes albopictus) in the identified endemic districts are absolutely griping the situation by seasonal variation in precipitation and temperature, land cover spatial variations, socio-economic, and ecological differences have directly affected the profusion of vector mosquitoes and the incubation period of the dengue and chikungunya virus, and thus, huge epidemics in the identified endemic districts along with entire state. Consequently, the nature and manmade environment is fuelling for the huge number of profusion of Aedes species mosquitoes in the epidemics area. Mapping the spatial distribution and seasonal variation of Aedes aegypti and Aedes albopictus, using Remote Sensing, and GIS technology could be an ultimate tool for functioning a dengue surveillance in the endemic districts as well as in the country, and thus, comfort to the public health experts to organize, implement and choose an appropriate control strategy for the prevention measures to control the grumpy situation in the dengue endemic hot spot regions in the country.

Aedes aegypti is a mosquito that is responsible for the spread of so many arboviral diseases such as yellow fever, zika and chikungunya which have recently drawn attention globally because of their rapid spread. The best way to control vectors that these arboviral diseases is the use of synthetic insecticides, however insecticides resistance may arise from indiscriminate use of these insecticides against Aedes aegypti. The present study was designed to evaluate insecticides resistance and to detect the knockdown resistance (kdr) mutations in Aedes aegypti of Bauchi State, North-eastern Nigeria. Mosquito larvae were collected from five Local Governments Areas across the state using ovitraps from April - September 2023 and evaluated against five main classes of insecticides using WHO bioassays. Larval bioassay revealed that Aedes aegypti larvae from all locations are susceptible to both temephos and deltamethrin except from larvae from Alkaleri that showed high resistance to deltamethrin (LC50 = 0.0193 mg/L RR = 18.2). Aedes aegypti adult showed moderate resistance towards the tested insecticides especially pyrethroids (deltamethrin and permethrin). Permethrin resistance populations from Misau and Ganjuwa Local Governments and deltamethrin resistance populations from Misau, Alkaleri, and Katagum Local Governments showed full susceptibility recovery following pre-exposure to PBO, indicating the involvement of cytochrome P450 monoxygenases. Aedes aegypti from Bauchi State was discovered to have the F1534C knockdown resistance mutation. Findings from this study will therefore help to design and implement insecticides resistant management interventions against Aedes aegypti and to improve yellow fever and dengue control in the state.