Potential of medicinal plants in mosquito control

Medicinal plants have long history as important components in traditional medicine, and food of humans since ancient Egyptians and Chinese. Naturally occurring botanical compounds contain a broad range of chemical active ingredients can intervene in all biological processes of the mosquito, thus interrupt its life cycle and dispersal and reduce harms to humans and animals. Many medicinal plants were tested for their pesticide and repellent potential, as crude material, essential oils or individual active ingredients. This article reviewed studies on the efficacy of many well known and commonly used safe medicinal plants or their products in controlling the mosquitoes; Aedes aegypti, Anopheles gambiae, An. stephensi and Culex quinquefasciatus and the ticks, Dermacentor variabilis, Amblyomma americanum, Ixodes scapularis and I. ricinus. Promising and encouraging results were obtained against these arthropod-vectors of zoonotic diseases

Histopathological effects of fenugreek [trigonella foenum-graceum] extracts on the larvae of the mosquito culex quinquefasciatus

Botanical bioactive compounds represent a rich resource for the discovery of novel pesticides that are effective, cheap and environmentally safe. The main targeted insect pests are mosquito vectors of most serious human and animal diseases in the world, such as the mosquito Culex quinquefasciatus. The susceptibility of the 3[rd]-4[th] instar larvae of Cx. quinquefasciatus laboratory colony from Saudi Arabia to an aquaeous as well as an ethanol extract of fenugreek was tested. Biochemical and histopathological effects of this extract were studied in the treated larvae. Bioassays showed that larvae are highly susceptible to the two fenugreek water and ethanol extracts; where 30% concentration caused 98 to 100% mortality, respectively. The ethanol extract is 1.5-2.5 fold more effective against the larvae compared to the water extract; 20% concentration caused about 98% mortality. Histopathological examination showed that the midgut, hindgut, muscles and nerve ganglia are the most affected tissues. These tissues suffered major changes including rupture and disintegration of epithelial layer and cellular vacuolization. Protein analysis indicated obvious changes in general protein profile of fenugreek-treated larvae compared to control Culex larval profile. The changes include the loss of protein bands of high molecular weights between 75 and 212 KD. A group of bands of molecular weights between 28-39 KD appeared in treated larvae. The overall changes show the gain of one band in treated larvae [total bands=9] compared to the control mosquito profile [total bands=8]. These results showed that fenugreek water and ethanol extracts have high larvicidal effect against mosquito larvae under laboratory conditions. Treatment of larvae with water extract caused prominent effects on various body tissues including the midgut and nervous system as well as total protein content. The active ingredients in plant extracts have important effects on physiological processes of the mosquito and therefore could implicate its life cycle and vectorial capacity for disease transmission and thus present new source for the development of insecticides against mosquitoes and other vectors

Histopathological and biochemical effects of myrrh, pomegranate and black seed on the mosquito culex quinquefasciatus in Saudi Arabia

Medicinal plants contain numerous bioactive compounds that rendered them potential targets for extensive research to produce novel pesticides against mosquitoes and important vectors of infectious diseases in the world. In this study, the histopathological and biochemical effects of three medicinal plants, myrrh, pomegranate and black seed, were tested against the mosquito Culex quinquefasciatus in Saudi Arabia. Fourth instar larvae were treated with aquaeous extract of each plant separately and the changes in various larval tissues and protein profile of the treated larvae were investigated. The results showed that many tissues suffered major changes due to exposure to plant extracts. The observed changes include rupture and disintegration of midgut epithelium with detachment of cellular membranes. There were vacuolization and swelling of some epithelial cells with the appearance of unknown structures. Other cells appeared devoid of nuclear material, which might be due to fragmentation of nuclear DNA/chromosomes, an important sign of apoptotic cells. Other tissues: Malpighian tubules, muscles, nerve ganglla and fat tissue suffered varying degrees of damage, but lesser than the midgut. Protein analysis showed changes in general protein profile of treated larvae compared to normal larvae. Treatment with plant extracts resulted in loss of protein bands of molecular weights of 2.3 KD and bands between 75 and 212 KD. In all treatments, a group of bands of molecular weights between 9 and 71 KD appeared but with variable profiles, which indicates the loss or gain of one or more band compared to the control mosquito profile. These bands might be metabolic products or fractions of the larger protein bands in response to treatment. These results showed that water extracts of myrrh, pomegranate and black seed affected various tissues and protein products of the mosquito at varying degrees and apparent modes of action. These changes will implicate various physiological processes of the mosquito and could interfere with its life cycle and vectorial capacity for disease transmission. Therefore, more research is needed to determine the specific mode of action and molecular targets in different mosquito stages as well as the side effects on non-targets of each plant extract for the production of novel effective and safe mosquitocidal compounds