Abdelkrim Amer

Bio: Abdelkrim Amer is an academic researcher. The author has contributed to research in topics: Aedes aegypti & Anopheles stephensi. The author has an hindex of 4, co-authored 5 publications receiving 1201 citations.

Larvicidal effects of various essential oils against Aedes, Anopheles, and Culex larvae (Diptera, Culicidae).

Abstract: Mosquitoes in the larval stage are attractive targets for pesticides because mosquitoes breed in water, and thus, it is easy to deal with them in this habitat. The use of conventional pesticides in the water sources, however, introduces many risks to people and/or the environment. Natural pesticides, especially those derived from plants, are more promising in this aspect. Aromatic plants and their essential oils are very important sources of many compounds that are used in different respects. In this study, the oils of 41 plants were evaluated for their effects against third-instar larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. At first, the oils were surveyed against A. aegypti using a 50-ppm solution. Thirteen oils from 41 plants (camphor, thyme, amyris, lemon, cedarwood, frankincense, dill, myrtle, juniper, black pepper, verbena, helichrysum and sandalwood) induced 100% mortality after 24 h, or even after shorter periods. The best oils were tested against third-instar larvae of the three mosquito species in concentrations of 1, 10, 50, 100 and 500 ppm. The lethal concentration 50 values of these oils ranged between 1 and 101.3 ppm against A. aegypti, between 9.7 and 101.4 ppm for A. stephensi and between 1 and 50.2 ppm for C. quinquefasciatus.

Repellency effect of forty-one essential oils against Aedes , Anopheles , and Culex mosquitoes

Abstract: Since ancient times, plant products were used in various aspects. However, their use against pests decreased when chemical products became developed. Recently, concerns increased with respect to public health and environmental security requiring detection of natural products that may be used against insect pests. In this study, 41 plant extracts and 11 oil mixtures were evaluated against the yellow fever mosquito, Aedes aegypti (Linnaeus), the malaria vector, Anopheles stephensi (Liston), and the filariasis and encephalitis vector, Culex quinquefasciatus (Say) (Diptera: Culicidae) using the skin of human volunteers to find out the protection time and repellency. The five most effective oils were those of Litsea (Litsea cubeba), Cajeput (Melaleuca leucadendron), Niaouli (Melaleuca quinquenervia), Violet (Viola odorata), and Catnip (Nepeta cataria), which induced a protection time of 8 h at the maximum and a 100% repellency against all three species. This effect needs, however, a peculiar formulation to fix them on the human skin.

Persistency of larvicidal effects of plant oil extracts under different storage conditions

Abstract: The persistency of larvicidal effects of 13 oils (camphor, thyme, amyris, lemon, cedarwood, frankincense, dill, myrtle, juniper, black pepper, verbena, helichrysum, and sandalwood) was examined by storage of 50-ppm solutions under different conditions (open, closed, in the light, and in the dark) for 1 month after the preparation of the solutions. The stored solutions were tested against Aedes aegypti larvae for four times during the storage period. Some oils under some conditions stayed effective until the last test, while some solutions had lost their toxicity during a short time after preparation. Thus, the mode of storage is absolutely important for the larvicidal effects. The fresh preparations were always the best.

The sensilla of Aedes and Anopheles mosquitoes and their importance in repellency

Abstract: The aim of this study was to detect the role of some mosquito organs in their sensation of repellent materials. A total of 250 females (15 days old) of the target species Aedes aegypti and Anopheles stephensi were prepared and divided into five groups: group 1, without antenna; group 2, without maxillary bulbs; group 3, without proboscis; group 4, without frontal tarsus; and group 5, normal females as control. A mixture of five oils containing Litsea cubeba 1%, Melaleuca leucadendron 1%, Melaleuca quinquenervia 1%, Viola odorata 1%, and Nepeta cataria 1% was included in a complex solvent containing 20% genapol, 10% polyethylene glycol, 20% ethanol, and 50% water. Furthermore, Bayrepel was used in this experiment at a 20% concentration in the same solvent. Pure water was used as control in this study. The test was carried out by spreading 100 μl of the repellent material or water on a 30-cm2 exposure area of a human volunteer’s arm. In A. aegypti, the biting and landing percentages increased significantly in those mosquito groups that lacked some organs (especially maxillary bulbs), while in A. stephensi, it became not clear which organ is responsible for perception of repellents.

Larvicidal effects of various essential oils against Aedes, Anopheles, and Culex larvae (Diptera, Culicidae).

Abstract: Mosquitoes in the larval stage are attractive targets for pesticides because mosquitoes breed in water, and thus, it is easy to deal with them in this habitat. The use of conventional pesticides in the water sources, however, introduces many risks to people and/or the environment. Natural pesticides, especially those derived from plants, are more promising in this aspect. Aromatic plants and their essential oils are very important sources of many compounds that are used in different respects. In this study, the oils of 41 plants were evaluated for their effects against third-instar larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. At first, the oils were surveyed against A. aegypti using a 50-ppm solution. Thirteen oils from 41 plants (camphor, thyme, amyris, lemon, cedarwood, frankincense, dill, myrtle, juniper, black pepper, verbena, helichrysum and sandalwood) induced 100% mortality after 24 h, or even after shorter periods. The best oils were tested against third-instar larvae of the three mosquito species in concentrations of 1, 10, 50, 100 and 500 ppm. The lethal concentration 50 values of these oils ranged between 1 and 101.3 ppm against A. aegypti, between 9.7 and 101.4 ppm for A. stephensi and between 1 and 50.2 ppm for C. quinquefasciatus.

Research in mosquito control: current challenges for a brighter future.

Abstract: Mosquitoes (Diptera: Culicidae) are a key threat for millions of people worldwide, since they act as vectors for devastating pathogens and parasites. In this scenario, vector control is crucial. Mosquito larvae are usually targeted using organophosphates, insect growth regulators, and microbial agents. Indoor residual spraying and insecticide-treated bed nets are also employed. However, these chemicals have negative effects on human health and the environment and induce resistance in a number of vectors. Newer and safer tools have been recently implemented to enhance control of mosquitoes. Here, I focus on some crucial challenges about eco-friendly control of mosquito vectors, mainly the improvement of behavior-based control strategies (sterile insect technique (“SIT”) and “boosted SIT”) and plant-borne mosquitocidals, including green-synthesized nanoparticles. A number of hot areas that need further research and cooperation among parasitologists, entomologists, and behavioral ecologists are highlighted.

Declining malaria, rising of dengue and Zika virus: insights for mosquito vector control

Abstract: The fight against mosquito-borne diseases is a challenge of huge public health importance. To our mind, 2015 was an extraordinary year for malaria control, due to three hot news: the Nobel Prize to Youyou Tu for the discovery of artemisinin, the development of the first vaccine against Plasmodium falciparum malaria [i.e. RTS,S/AS01 (RTS,S)], and the fall of malaria infection rates worldwide, with special reference to sub-Saharan Africa. However, there are major challenges that still deserve attention, in order to boost malaria prevention and control. Indeed, parasite strains resistant to artemisinin have been detected, and RTS,S vaccine does not offer protection against Plasmodium vivax malaria, which predominates in many countries outside of Africa. Furthermore, the recent outbreaks of Zika virus infections, occurring in South America, Central America and the Caribbean, represent the most recent of four arrivals of important arboviruses in the Western Hemisphere, over the last 20 years. Zika virus follows dengue (which slyly arrived in the hemisphere over decades and became more aggressive in the 1990s), West Nile virus (emerged in 1999) and chikungunya (emerged in 2013). Notably, there are no specific treatments for these arboviruses. The emerging scenario highlights that the effective and eco-friendly control of mosquito vectors, with special reference to highly invasive species such as Aedes aegypti and Aedes albopictus, is crucial. The concrete potential of screening plant species as sources of metabolites for parasitological purposes is worthy of attention, as elucidated by the Y. Tu's example. Notably, plant-borne molecules are often effective at few parts per million against Aedes, Ochlerotatus, Anopheles and Culex young instars, can be used for the rapid synthesis of mosquitocidal nanoformulations and even employed to prepare cheap repellents with low human toxicity. In addition, behaviour-based control tools relying to the employ of sound traps and the manipulation of swarming behaviour (i.e. "lure and kill" approach) are discussed. The importance of further research on the chemical cues routing mosquito swarming and mating dynamics is highlighted. Besides radiation, transgenic and symbiont-based mosquito control approaches, an effective option may be the employ of biological control agents of mosquito young instars, in the presence of ultra-low quantities of nanoformulated botanicals, which boost their predation rates.

Plant-mediated biosynthesis of nanoparticles as an emerging tool against mosquitoes of medical and veterinary importance: a review

Abstract: Mosquitoes (Diptera: Culicidae) are a key threat for millions of people worldwide, since they act as vectors for devastating parasites and pathogens. Mosquito young instars are usually targeted with organophosphates, insect growth regulators and microbial control agents. Indoors residual spraying and insecticide-treated bed nets are also employed. However, these chemicals have strong negative effects on human health and the environment. Newer and safer tools have been recently implemented to enhance control of mosquitoes. In this review, I focus on characterization, effectiveness, and non-target effects of mosquitocidal nanoparticles synthesized using botanical products (mosquitocidal nanoparticles, MNP). The majority of plant-fabricated MNP are silver ones. The synthesis of MNP is usually confirmed by UV-visualization spectroscopy, followed by scanning electron microscopy or transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction studies. Interestingly, plant-synthesized metal nanoparticles have been reported as effective ovicides, larvicides, pupicides, adulticides, and oviposition deterrents against different mosquito species of medical and veterinary importance. Few parts per million of different MNP are highly toxic against the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti, and the filariasis mosquito Culex quiquefasciatus. However, despite the growing number of evidences about the effectiveness of MNP, moderate efforts have been carried out to shed light on their possible non-target effects against mosquito's natural enemies and other aquatic organisms. In the final section, particular attention was dedicated to this issue. A number of hot areas that need further research and cooperation among parasitologists and entomologists are highlighted.