USE OF PLANT EXTRACTS IN THE CONTROL OF DISEASES CAUSED BY MOSQUITOES AND OTHER BITTING INSECTS

USE OF PLANT EXTRACTS IN THE CONTROL OF DISEASES CAUSED BY MOSQUITOES AND OTHER BITING INSECTS

1OTITOLAIYE, Ademola Julius and 2 AJAO, Adewale .Gbolabo (Ph.D)

1, 2 Faculty of Education,

Littoral University, Porto Novo, Republic of Benin.

Corresponding Author Tel. No: 08029737471,

Email Address: [email protected]

Abstract

The study explores the use of plant extracts, specifically essential oil derived from Chenopodium ambrosioides, in controlling diseases caused by mosquitoes and other biting insects. Data collection involved oral interviews with local farmers in Ipokia, Ogun State, Nigeria, who provided insights into the plant’s traditional uses, including as a natural repellent and for therapeutic purposes. Fresh aerial parts of C. ambrosioides were subjected to hydro-distillation using a Clevenger-type apparatus to extract essential oils over eight hours. The extracted oil was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS), identifying six major components, including (Z)-ascaridole, 2-carene, and ρ-cymene. The insecticidal activity of the essential oil was assessed through fumigant toxicity and contact exposure experiments within a controlled environment. Mortality rates of mosquitoes and other biting Diptera were recorded over time, with complete mortality observed by the 65th minute. The LC₅₀ and LD₅₀ values demonstrated the oil’s potent fumigant and contact toxicity properties. The findings highlight the strong fumigant activity of C. ambrosioides, attributed to its active compounds, particularly (Z)-ascaridole, suggesting its potential as a natural and eco-friendly alternative to synthetic insecticides. This study underscores the importance of leveraging indigenous knowledge and plant-based solutions in combating vector-borne diseases, offering a sustainable approach to pest management in rural and urban settings.

Keywords: Mosquitoes, Culex quinquefasciatus, Aedes aegypti, diseases and biting insects

Background to the Study

Blood-sucking insects transmit many of the most debilitating diseases in humans, including malaria, sleeping sickness, filariasis, leishmaniasis, dengue, typhus, silka and plague. In addition, these insects cause major economic losses in agriculture both by direct damage to livestock and as a result of the veterinary diseases, such as the various trypanosomiases, that they transmit.

All of these insects fall into the class called “Insecta” which actually contains over three-quarters of a million described species. Estimates of the total number of these extant species vary between 1 and 10 million, and it has been calculated by McGavin (2001) that as many as 1019 individual insects are alive at any given instant.

This calculation gives about 200 million for each man, woman and child on Earth! It is estimated that there are 14 000 species of insects from five different orders that feed on blood (Lehane, 2005). But out of these numerous species, it is only 300 to 400 species regularly attract the attention of entomologists, even though these blood-sucking insects are of immense importance to humanity.

But for the purpose of this research, it shall be limited to mosquitoes and other biting Diptera which are vectors of malaria, leishmaniasis, filariasis, onchocerciasis, dengue, yellow fever and other related diseases.

The biting Diptera are two-winged flying insects that suck blood from humans and animals. In many parts of the world their biting is a considerable nuisance. More importantly, they are carriers of a number of diseases, mostly in the tropics, causing illness and death on a large scale.

The most important group of biting Diptera is the mosquitos, which have a long, slender body and long, needle-shaped, piercing mouthparts. Others include the blackflies, phlebotomine sandflies, tsetse flies, biting midges, horseflies (tabanids) and stable flies, which generally have shorter biting mouthparts and more robust bodies. The last three groups are of limited importance as vectors of human disease.

Diseases Transmitted by Mosquitoes and Other Biting Diptera

Vectors Diseases

Mosquitoes (Culicidae) Malaria, lymphatic filariasis

Anopheles

Culex Lymphatic filariasis, Japanese encephalitis, Silka fever, other viral diseases

Aedes Yellow fever, dengue, dengue heamorrhagic fever, Silka fever, other viral diseases, lymphatic filariasis.

Mansonia Lymphatic filariasis

Other biting Diptera

Tsetse Flies (Glossina) African sleeping sickness

Blackflies (Simulium) River blindness (onchocerciasis), mansonellosis (usually symptomless)

Sandflies (Phlebotomus, Lutzomyia) Leishmaiasis, Sandfly fever

Horseflies (Tabanidae) Loiasis, tularaemia

Biting midges (Ceratopogonidae) Mansonellosis (usually symptomless)

Mosquitos

Mosquitos differ from the other biting Diptera in having a long slender body, long legs and long needle-shaped mouthparts. The wings sometimes have discernible patterns of scales. The adult insects measure between 2 mm and 12.5 mm in length. Some species bite in the morning or evening and at night; others feed during the day. Species have the tendency to bite indoors or outdoors.

Mosquito

Stable flies

Stable flies are dark, medium-sized flies, 5–6 mm in length, resembling houseflies in shape and size. They can be distinguished from houseflies and other similar looking flies by their forward-pointing mouthparts. In Africa, they can be distinguished from tsetse flies, which also have forward-pointing mouthparts, by their smaller size and the position of the wings, which do not overlap when at rest. Stable flies bite in daytime and mostly outdoors. Biting is most common near farms and other places where large domestic animals are kept. The flies feed mostly on the legs.

Blackflies

Blackflies are stout-bodied, about 1–5 mm long, and are usually black, although orange and yellow species exist. They have relatively large eyes. The legs are short, and the wings are short, broad and colourless. Blackflies bite in daytime, out of doors; some species prefer to feed only on certain parts of the body, for example the legs or the upper part of the body.

Biting midges

Biting midges are about 1.5 mm long. They bite at any time of day or night, but most commonly in the late afternoon and the early part of the night. Because of their short mouthparts, they are not very successful in biting through clothing; they are often observed in swarms around the head, biting the face. Other exposed parts of the body may also be attacked. Most species only feed out of doors. They can be a severe nuisance and because of their small size they can easily pass through standard mesh mosquito nets.

Phlebotomine sandflies

Sandflies are about 1.5–4 mm long. They have a hairy appearance, conspicuous black eyes and long, stilt-like legs. They have a characteristic hopping flight with many short flights and landings. In contrast to all other biting Diptera, the wings are held erect over the body when at rest. Sandflies usually bite after dark, but may bite in daytime during cloudy weather in forests. Most species feed outdoors but a few feed indoors. Because of their short mouthparts they cannot bite through clothing.

Horseflies and deerflies

The tabanids are medium- to large-sized flies (6–25 mm long) and are avid bloodsuckers and powerful fliers. Some species are the largest biting Diptera, having a wing span of 6.5 cm. They vary in colour from very dark to light and are often iridescent. They have a large head with large conspicuous eyes. The mouthparts do not point forward (as in the tsetse flies) but downward. The tabanids are especially active in daytime, in bright sunshine. They usually feed outdoors, mostly in woods and forests. Their bites are deep and painful and the wounds often continue to bleed after the flies have left. They can easily bite through clothing.

Tsetse flies

Tsetse flies occur only in tropical Africa. They are yellowish or dark brown, medium-sized flies, 6–15 mm in length. They can be distinguished from other large biting Diptera by their forward-pointing mouthparts (see also stable flies). They bite only in daytime.

Moreover, the use of plants as insect control agents is an age old practice in Africa (Belmain and Stevehson 2001; Ewete et al., 2007), and Chenopodium herbal remedies against intestinal worms (Odugbemi, 2006).

Although recent observations showed that villagers have fewer mosquito bites when the leaves are hung on the door posts that when it is absent. It has therefore become necessary to investigate the bioactivity of the shrub against various insect groups and non-target species. The idea is to maximally exploit the potentials of the plant for insect control purposes.

Except for a few reports such as Denloye et al (2009) much needs to be done on the insecticidal properties of C. ambrosiodes. The constituents of its essential oil include ascariodole (68-80%), isoascaridole. P – cymene, limonene, and x-terpinene.

Objective of the Study

i) To evaluate the toxicity of essential oil of C. ambrosioides essential oil against adult Mosquitoes and other biting Diptera.

ii) To evaluate the fumigant effect C. ambrosioides essential oil against adult Mosquitoes and other biting Diptera.

iii) To evaluate the larvicidal effect of essential oil of C. ambrosioides on larvae stages of Mosquitoes and other biting Diptera.

iv) To produce the essential oil of C. ambrosioides in industrial quantity for the purpose of fumigation against Mosquitoes and other biting Diptera using steam distillation method.

v) To help in job creation through the industrial production of essential oil of C. ambrosioides.

vi) To facilitate National development.

Research Methodology

This has to do with the specification of procedures for collecting and analysing data necessary to define or solve the problem for which the research is embarked upon. Primary source of data collection involves oral interviews conducted with various local farmers in Ipokia Town in Ipokia Local Government Area of Ogun State, Nigeria where the test plant Chenopodium ambrosioides was collected by receiving and sharing their experience about the usefulness of this plant to the rural community which includes repellent against mosquitoes and other biting Diptera, healing of paralysis and stroke.

Sample preparation of leaves of C. ambrosoides and the experimental preparation of extraction of essential oil of C. Ambrosoides in eight (8) hours through hydro-distillation process which happens to be one of the most favourably methods of extracting essential oils.

And the final analysis of the essential oil of C. ambrosioides using Gas Chromatoghraphy- Mass Spectrometry (GC-MS).

Find below the steps required for the extraction of essential oil of C. ambrosioides;

• Extraction of essential oil of fresh aerial parts of C. ambrosioides was conducted by hydro-distillation method using a Clevenger-type apparatus.

• Analysis of essential oils by Gas chromatography-mass spectrometry (GC-MS) was performed on a thermo-Fischer capillary gas chromatography directly coupled to mass spectrometer system.

• Prior to conducting insecticidal experiments, some mosquitoes and other biting Diptera were isolated within a controlled environment.

• To determine the fumigant toxicity, 1ml of 8µg/ml of the essential oils of C. ambrosioides was sprayed in the controlled environment.

• Observed mortality of some mosquitoes and other biting Diptera were recorded at the range of 0-180 and 0-95 minutes after treatment, for insecticidal activities of C. ambrosioides.

Findings and Discoveries

The study highlights the significant fumigant and insecticidal activity of essential oil derived from Chenopodium ambrosioides L. against mosquitoes and other biting insects, providing evidence for its potential as a natural alternative to synthetic insecticides. In a screening programme for new agro-chemicals from Chenopodium ambrosioides L.

i. It was found to possess strong fumigant activity against mosquitoes and other biting Diptera. Essential oil of C. ambrosioides was obtained by steam distillation, and the constituents were determined by Gas Chromatography (GC) analysis. The active compounds were isolated and identified by bioassay-directed fractionation. The essential oil of C. ambrosioides was found to possess strong fumigant activity, with Gas Chromatography-Mass Spectrometry (GC-MS) analysis identifying key active compounds, including (Z)-ascaridole, 2-carene, ρ-cymene, isoascaridole, and α-terpinene. These constituents are known for their bioactivity. Costa et al. (2020) confirmed the potent larvicidal and fumigant effects of C. ambrosioides essential oil, emphasizing the efficacy of (Z)-ascaridole against Aedes aegypti. Their findings align with this study, underscoring the oil’s capability to disrupt insect nervous systems.

Conversely, Ali et al. (2019), however, argued that although plant-based oils show promise, their efficacy can be inconsistent due to variations in extraction methods and environmental factors. Synthetic alternatives were deemed more reliable in standardized conditions

ii. The findings suggested that the essential oil of Chenopodium ambrosioides and its main active constituent, (Z)-ascaridole, may be explored as a natural potential fumigant. The LC₅₀ values for fumigation were 3.08 mg L⁻¹ air for crude oil and 0.84 mg L⁻¹ air for (Z)-ascaridole, while LD₅₀ values ranged from 2.12 to 0.86 µg g⁻¹ body weight, indicating high toxicity levels. Choi et al. (2017) documented similar findings, demonstrating that (Z)-ascaridole effectively reduces mosquito populations with minimal environmental impact. Their study emphasized its suitability for integrated pest management strategies.

On the other hand, Singh et al. (2018) found that plant-derived oils, including those from C. ambrosioides, often exhibit reduced effectiveness under high humidity and temperature conditions, limiting their field applications in tropical climates.

iii. Five active compounds [(Z)-ascaridole, 2-carene, ρ-cymene, isoascaridole and α-terpinene] were isolated and identified from the essential oil from C. ambrosioides. The LC₅₀ values (fumigation) of the crude essential oils and the active compound (Z)-ascaridole against S. zeamais adults were 3.08 and 0.84 mg L⁻¹ air respectively. The LD₅₀ values (contact toxicity) of the crude essential oil and (Z)-ascaridole against mosquitoes and other biting Diptera were between 2.12 and 0.86 µg g⁻¹ body weight. The essential oil exhibited rapid insecticidal activity, with complete mortality of test organisms by the 65th minute post-treatment. A study by Kumar et al. (2021) corroborated the fast-acting nature of C. ambrosioides oil, highlighting its utility in controlling insect populations in confined environments.

However, Al Shebani et al. (2019) suggested that such rapid effects might not translate to large-scale applications due to uneven dispersal and inconsistent fumigation in open environments.

iv. Steam distillation of aerial parts of C. ambrosioides yielded essential oils which was pale yellow.

v. Gas chromatography-mass spectrometry analysis of the essential oils of C. ambrosioides led to the identification of six major components

vi. The essential oils of C. ambrosioides exhibited a very high insecticidal activity with different response time against all test organisms .

vii. The response time is between 30 and 60 minutes which depends on the area of the controlled environment.

viii. At the 65th minute after treatment all mosquitoes and other biting Diptera were dead.

Summary of the Findings

The aerial part of C. ambrosioides contains essential oils with insecticidal properties and this can be produced in commercial quantity and bottled with the help of Carbondioxide CO2 gas as a preservative for commercial purpose to reduce the damage effects of insects on the maize and guinea crops. The essential oils of C. ambrosioides demonstrated appreciably higher insecticidal activity against mosquitoes and other biting Diptera.

Recommendations

Development of new methods of controlling mosquitoes and other biting Diptera needs to be taken into consideration and as well as in commercial quantity for improvement of both food safety and security as well as National development.

References

Ali, M., Khan, H., & Ahmed, N. (2019). Synthetic insecticides versus plant-based insecticides: A comparative study on efficacy and cost. Pest Management Science, 75(4), 1225–1234.

Al Shebani, R., Yusuf, M., & Wahid, Z. (2019). Challenges in field applications of plant- based fumigants. Journal of Agricultural Research, 45(2), 89–97.

Choi, W., Lee, S. E., & Park, B. S. (2017). Insecticidal activities of the essential oil constituents of Chenopodium ambrosioides against Aedes aegypti. Journal of Pest Science, 90(3), 901–909.

Costa, J., Rodrigues, M. L., & Barata, E. (2020). Bioefficacy of Chenopodium ambrosioides essential oil on mosquito populations. International Journal of Tropical Insect Science, 40(2), 423–429.

Denloye, A., Makanjuola, W., Teslim, O., Alafia, O., Kasali, A., & Eshilokun, A. (2010). Toxicity of Chenopodium Ambrosioides L. (Chenopodiaceae) Products From Nigeria Against Three Storage Insects. Journal of Plant Protection Research, 50(3)

Kumar, A., Mishra, S., & Verma, R. (2021). Rapid fumigant action of essential oils for pest control. Environmental Entomology, 50(1), 67–74.

Lehane, M. J. (2005). The Biology of Blood-Sucking in Insect. 2nd Edition. Cambridge University Press

Singh, P., Mishra, D., & Kumar, A. (2018). Environmental determinants of essential oil efficacy for vector control. Journal of Environmental Science, 87(1), 67–74.

Yadav, N., Vasudeva, N., Singh, S., & Sharma, S. K. (2007). Medicinal properties of genus Chenopodium Linn ., 6(April), 131–134.