INSECTICIDAL ACTIVITY OF CHROMOLAENAODORATA AND VERNONIAAMYGDALINA LEAF EXTRACTS AGAINST ANOPHELES GAMBIAE LARVA
Abstract
Female Anopheles mosquitoes are the vectors of human malaria. The use of chemical insecticides for vector control has hampered with environmental pollution and insect. This suggests the need for the development of more potent and environment-friendly insecticides for effective control of malaria. This research investigated the insecticidal activity of Chromolaenaodorata and Vernoniaamygdalina leaf extracts against An.
gambiae in the laboratory at ambient temperature of 28 ± 2 °C and 75 ± 5% relative humidity. Different concentrations of 20 mg/L, 40 mg/L, 80 mg/L, 120 mg/L and 160 mg/L were prepared and these aqueous solutions were used for the experiments. Larval, pupal and adult mortality of An. gambiae were tested after 24 hours of exposure. Results showed that there were significant differences (P < 0.05)in toxicity level of the two plant extracts on An. gambiaelarvae, pupae and adults.
Vernoniaamygdalina extract was the most toxic to An. gambiae larvae at all tested concentrations of 20 mg/L, 40 mg/L, 80 mg/L, 120 mg/L and 160 mg/L causing 47.5%, 82.5%, 100%, 100% and 100% mortality after 24 hours of treatment, respectively. Chromolaenaodorata extract caused 32.5%, 60%, 82.5%, 92.5% and 100% mortality of An. gambiae larvae after 24 hours of treatment at concentrations 20 mg/L, 40 mg/L, 80 mg/L, 120 mg/L and 160 mg/L, respectively. Vernoniaamygdalina extract was the most lethal to An.
gambiae pupae and adults which caused 55% mortality of adult An. gambiae at concentration 160 ml/L. The concentration of C. odorata and V. amygdalina leaves extracts required to evoke 50% death of An. gambiae adult were 296.20 mg/L and 147.98 mg/L respectively. The LC90 of C. odorata extract was 3107.55 mg/L while V. amygdalina extract was 2221.05 mg/L for mosquito adults.
The plant extracts were not as effective against adults compared to larva and pupa of An. gambiae. This study showed that C. odorata and V. amygdalina were toxic to malaria vector with V. amygdalina being more potent. This suggest that V. amygdalina extracts could serve as an alternative method to synthetic chemical control of malaria vectors.
1.0 INTRODUCTION
1.1 Background of the Study
Several diseases are transmitted by arthropod vectors of which mosquito is one of them. Mosquitoes are responsible for the transmission of diseases such as malaria, lymphatic filariasis, and dengue fever among others most especially in the tropical regions of the world (WHO 2017). Out of these diseases transmitted by mosquitoes, malaria is the most devastating in terms of the number of incidence, prevalence, morbidity and mortality (WHO 2017).
It is transmitted by the mosquitoes of the genus Anopheles and it is caused by the protozoa of the Plasmodium genus (WHO 2018). Examples of Anopheles species include Anopheles gambiae, Anopheles culicifacies, Anopheles stephensi, Anopheles fluviatilis, Anopheles minimus, Anopheles dirus and Anopheles sundaicus among others with Anopheles gambiae being the prominent one among them all (Singh et al. 2014).
Five species of Plasmodium namely Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale and Plasmodium knowlesiare responsible for human malaria but P. falciparum and P. vivaxare most notorious in terms of the number of cases they are responsible for (WHO 2018).
They were an estimated 219 million cases of malaria with 435,000 of them resulting in death in 2017 (WHO 2018). In order to stop or reduce the transmission of malaria parasites, there is need to control the vector population.
Several methods such as habitat modification, the use of synthetic chemical insecticides and the use of biological means such as employing natural predators, parasites and parasitoids to control the populations of mosquitoes (Kwenti 2017).
The major method that have been employed in the control of mosquitoes is the use of synthethic insecticides such as chlorodane, aldrin, Dieldrin, dichlorodiphenyltrichoroethane (DDT) among others (Singh et al 2014).
However, these chemical have been shown to have negative effect in the dynamics of the earth’s ecosystem resulting in resistance of mosquito species to the chemicals, environmental pollution and toxicity to human and other non-targeted organisms (Mahmood et al 2015).
Hence, there have been clamor by various quarters to develop a safe means to combat the proliferation of insect vector species (Gupta &Dikshit 2010). This has led to the focus on developing insecticides from botanical sources that are safe to use in the environment due to the fact that they are easily degradable and less toxic to humans and non-targeted organisms(Thomson &Vijan 2016).
Several plant materials such as Alstoniaboonei, Curuma longa, Cymbopogonwinterianus, Ocimumamericanum, Nepetacataria, Viola odorata, Melaleucaquinquenervia, Azadirachtaindica, Citrus medica, Nicotianatabacum, Anacardiumoccidentale, Aframomummelegueta, Garcinia kola, Citrus sinensis and Murrayakoenigiihave been used to control mosquitoes (lleke 2018).
Extracts from plants has been good sources of phytochemicals as mosquito egg and larval control agents, since they constitute an abundant source of bioactive compounds that are easily biodegradable into non-toxic products. In fact, many researchers have reported on the effectiveness of plant extracts or essential oils against mosquito larvae. They act as larvicides, insect growth regulators, repellents, and oviposition attractants (Pushpanathan, 2008;Samiduraiet al., 2009;Mathivanantet al., 2010).
Chromolaenaodoratais a weed which belongs to Asteraceae family. It is found in tropical and subtropical areas, extending from west, central and southern Africa to India, Sri Lanka, Bangladesh, Laos, Cambodia, Thailand, southern China, Taiwan, and Indonesia.
The weed goes by many common names including; Siam weed, devil weed, French weed, communist weed (Vaisakh and Pandey, 2012). In Nigeria, the Chromoleanaodoratais referred to as ―Obuinenawa‖ by the Igbo and ―ewe awolowo‖ by the Yoruba. This plant is exploited traditionally for its medicinal properties, especially for external uses as in wounds, inflammation and skin infections.
Some studies also demonstrate the efficacy of its leaf extract, as antioxidant, anti-inflammatory, analgesic, anti-microbial and cytoprotective agent (Ajaoet al., 2011). The oil from C. odorataalso had been exploited as insecticide, ovicide and larvicide (Noudogbessiet al., 2006). Previous phytochemical studies of the leaf extracts of C. odorata show the presence of alkaloid, cardiac glycosides, anthocyanin, tannin, and flavonoids (Ngoziet al., 2009).
Vernoniaamygdalina belong to the family Asteraceae and grows in the tropical regions of Africa (Odugbemi 2006). The plant is a shrub, evergreen in colour and can grow between 2-5 m in height with petiolate leaf of about 6 mm in diameter (FAO 2001).
The plant is bitter due to the characteristic odour and bitter taste of the leaves owing to the presence of anti-nutritional factors such as alkaloids, saponins, tannins and glycosides (Bonsi et al 1995). The aim of this research study is to investigate the ant mosquito activities of C. odorataand V. amygdalinaleaf extracts on the larvae, pupae and adults of malaria vector, An. gambiae.
An estimated 3.3 billion people are at risk of malaria globally, with populations living in sub- Saharan Africa having the highest risk (WHO, 2012) and two-fifths of the world‘s population is at risk of dengue fever (WHO, 2003). Malaria alone accounts for about 50 per cent of outpatient consultation, 15 per cent of hospital admission, and also among the top three causes of death in the country.
In recent years, the use of many synthetic insecticides in mosquito control programme has been limited, due to many challenges such as, high cost of synthetic insecticides, environmental sustainability, toxic effect on human health (immune suppression), and other non-target organisms, environmental persistence, higher rate of biological accumulation and magnification through ecosystem, as well as increasing insecticide resistance on large scale (Srivastava and Sharma, 2000; Raghvendra and Subbarao, 2002).
These challenges have resulted in an urge to search for environmentally sustainable, biodegradable, affordable and target selective insecticides against mosquito species (Saxena and Sumithra, 1985; Kumar and Dutta, 1987; Chariandyet al., 1999; Markouket al., 2000; Tare et al., 2004).
Consequently, the application of eco-sustainable alternatives such as biological control of vectors has become the main focus of the control programme to replace the synthetic chemical insecticides (Gosh et al., 2012). One of the most effective alternative approaches under the biological control programme is to utilise the plants biodiversity as a reservoir of safer insecticides of botanical origin as a simple, affordable and sustainable method of mosquito control.
1.3.1 General Aim
The aim of this study was to investigate the insecticidal activities of extracts of Chromolaenaodorata and Vernoniaamygdalina leave against Anopheles Gambiae larva
1.3.2 Specific ObjectivesPresent an analysis of the crude extracts ofChromolaenaodorataand Vernoniaamygdalinaleaves against Anopheles Gambiae larva.Determination of the most potent solvent extracts with larvicidal activity against Anopheles Gambiae larva.
Do You Have New or Fresh Topic? Send Us Your Topic
1.4 Research Questions
The research question for this work include:
What is the effect of the crude extracts ofChromolaenaodorataand Vernoniaamygdalinaleaves on Anopheles Gambiae larva?What is the most potent solvent extracts with larvicidal activity against Anopheles Gambiae larva?
Mosquito larvae is the easiest stage to target in its life cycle and several studies have documented the efficacy of plant extracts as a reservoir pool of bioactive toxic agents against mosquito larvae. Furthermore, evolution of the resistance to plant-derived compounds has rarely been reported (Sharma et al., 2006).
However, the main reasons for the failure in laboratory to field utilisation of bioactive phytochemicals are poor characterization and inability to determine the active toxic components responsible for larvicidal activity (Ghosh et al., 2012).
Hence, there is a need for the characterization, of various plant extracts to determine the active (larvicidal) components of locally available plants for mosquito control. This will help to reduce dependence on expensive and mostly imported products, and stimulate local efforts to enhance the general public health.
INSECTICIDAL ACTIVITY OF CHROMOLAENAODORATA AND VERNONIAAMYGDALINA LEAF EXTRACTS AGAINST ANOPHELES GAMBIAE LARVA
INSTRUCTIONS AFTER PAYMENT
- 1.Your Full name
- 2. Your Active Email Address
- 3. Your Phone Number
- 4. Amount Paid
- 5. Project Topic
- 6. Location you made payment from