Malaria is certainly one of the main tropical endemic illnesses that have the most serious repercussion particularly on the death rate as well as on the economics. In essence, malaria is considered as one of the common diseases in Africa especially those countries that are located in bushy areas where mosquitoes commonly known as the Anopheles gambiae breeds. In this light, Anopheles gambiae giles is considered as the most efficient vector responsible for human malaria across the afro-tropical region of Africa. As a result, it is often referred to as African malaria mosquito (Barreaux, Stone, Barreaux, & Koella, 2018). Notably, the Anopheles gambiae complex of species of siblings is comprised of close to eight reproductively isolated species that are sometimes regarded to be indistinguishable morphologically. Members of the Anopheles gambiae are mostly located throughout tropical Africa as well as south of the Sahara desert. One particular species of the Anopheles gambiae is the Anopheles arabiensis that is considered to be around Southern Arabia (Attenborough, 2015). This type of mosquito is distributed across sub-Saharan countries that include Madagascar. The adult of a female Anopheles gambiae can be differentiated from the rest of mosquitoes given the fact that the palps are long just like their proboscis.
Furthermore, adult Anopheles gambiae is regarded to have a rather distinguishable position when they are resting where their abdomen is mostly raised into the air. Notably, Anopheles gambiae has many distinct colors of their body which ranges from light brown to the grey consisting of pale spots of yellow cream, white as well as the dark areas located on their wings (White, Collins, & Besansky, 2011). Compared to other species of mosquitoes, adult Anopheles gambiae are often small to a rather medium size that consists of an average length of the wings with some having an average wings size of about 2.8 to around 4.4mm. This paper intends to discuss in detail the Anopheles gambiae, a vector causing malaria in various African countries.
The overall morphology, as well as life history of Anopheles gambiae, is hugely characterized by the biting rates of this type of mosquitoes, the duration of their entire gonotrophic cycles, their survival chances, as well as the development of the immature mosquitoes and their adults. In this case, any factor that has the capability of influencing any of these factors has the capacity to influence disease transmission as caused by the Anopheles gambiae mosquitoes.
Head
The overall scales of the Anopheles gambiae mosquitoes are often pale, white, although in some specimens they are considered to be faintly yellowish in color or rather posteriorly.
Antennae: The antennae of the Anopheles mosquitoes are regarded to be light particularly on the torus as well as the inner parts of its segments.
Male palpi: in essence anopheles mosquitoes mostly have a rather pale with a black band near the bases as well as a black band.
Female pharynx: from the aspect of dorso-ventral the overall pharyngeal armature of this insect indicate that a rather double row of about 12 to 18 teeth. The entire bucco-pharyngeal striae is regarded to appear in an optical section in form of overlapping ridges.
Thorax
The overall integument of the Anopheles gambiae is often considered to be light brown which varies from greyish to rather brown with reflection which is often orange in color with spots which are not clearly defined. This mosquito has a median band that is located on the mesonotum with two dark longitudinal bands on each side of the middle line. Notably, the scales of this mosquito in the thorax are often cream or yellowish in color with small as well as pointed lobes which are mainly covered by scales. The mosquito contains about 3 to 6 spiracular bristles.
Legs: in essence, the femurs, the entire segment I of the tarsus as well as the tibia are mainly spectacled by rather creamy or even yellowish a scale that forms spots on the fore as well as the middle legs (Simões, Gibson, & Russell, 2017). The femur, as well as the middle legs of the Anopheles gambiae, has a spot or rather a pale ring that is located near the base. Additionally, the overall apex of the tibia is considered to be pale in color.
Anterior tarsus: gambiae has a very clear ring which covers the entire of is basal as well as the apical extremities of its segments.
Middle tarsus: the middle tarsus of the Anopheles gambiae is considered to be identical with the proceeding ones although the pale rings of its segments are narrower.
The overall integument of the gambiae is considered to be light brown of rather yellowish that appears to be darker or rather almost black particularly in the engorged females. Its dorsal, as well as the ventral surfaces, is often covered with yellowish hairs. Additionally, there are always light spots particularly on the sternite of its segments.
Male hypopygium: they contain an elongated coxite that is relatively narrow with a few scales as well as long setae on the external surfaces. Additionally, a half of its inner surface on the basal contains a group of rather five strong bristles or spines. The coaxial is prolonged in the second segment of the Terminalia which is narrow and elongated. There is a rather rudiment of the entire third segment that resembles a chitinized claw at its tip. Primarily, a lobe can be distinguished particularly at the base of the coxite on the interior outer edge.
Wings
In essence, it is no doubt that A. gambiae is often subjected to various individual variations especially in regards to the ornamentation of the legs as well as the distribution of both the dark and the pale regions on its wings. Nonetheless, specimens from most of the Eastern African countries tend to lose the pale interruptions in most of its third dark area of the vein.
Legs
There is a lot of variation in regards to the overall speckling particularly on the femora, tibiae, as well as the interior tarsi. The tarsi rings that are mostly located at the hind legs are often regarded to be very variable.
The overall duration of the life cycle of a particular A. gambiae has been a debated topic for the last couple of decades gives the fact that it holds a lot of importance. Notably, its importance arises especially when there is a need for obtaining an exact estimate especially when one aims to establish the rhythm of a particular operation in an ant larval campaign. Like all the mosquitoes, Anopheles gambiae passes through four main stages in their life cycle that is an egg, larva, pupa as well as an adult (Cheng,Tan, Hahn, & Besansky, 2018). The first three stages are considered to be aquatic while the last 5 to about 14 days is regarded to be dependent on the species as well as the ambient temperature. The adult stage is at the time when the female Anopheles gambiae mosquito acts as the main vector for the malaria illness. The adult female A. gambiae is most anticipated to live up to only a month and more specifically they do not live for a period more than one to two weeks in nature.
Eggs: in essence, the adult female of A. gambiae is estimated to lay eggs ranging from 50 to about 200 per every oviposition. While eggs are laid directly in the water, they tend to possess unique floats on either side. The eggs are mostly not resistance to drying and this they hatch after two to about three days. Nonetheless, hatching may take longer time usually one to two weeks in colder climatic regions.
Larvae: primarily, mosquito larvae often contain a well-developed head which contain brushes of mouth that is used in the feeding process, a large thorax as well as abdomen which are segmented. On the other hand, the larvae of mosquito are mostly considered to have no legs. Unlike other mosquitoes, anopheles gambiae have no respiratory syphon (Liu, Modrek, Gosling, & Feachem, 2013). Consequently, they often position themselves in a manner that their bodies are parallel to the surface of the water. Additionally, larvae tend to breath by the use of spiracles which are located at the 8th segment of the abdomen thus they tend to come to the surface of water occasionally.
Ideally, the larvae are considered to spend most of its life feeding on bacteria, microorganism as well as algae particularly in the surface of micro-layer. The only time that they tend to dive below is that the time they are disturbed (World Health Organization., 2018). Additionally, they either swim by the use of the jerky movements of their body or rather by the use of propulsion especially with the mouth brushes. The larvae of Anopheles mosquitoes tend to develop through four important stages. While the larvae of the A. gambiae occur in various habitats, they mostly prefer clean and unpolluted water.
Pupae: when viewed from either side, the pupae resembles rater comma-shaped where the head, as well as the thorax, are merged with the abdomen thus making them curve around underneath. Just like the larvae, the pupae often come to the surface to breathe something they do by the use of a pair of special respiratory trumpet on the cephalothorax (World Health Organization., 2018). The entire surface of the cephalothorax splits thus allowing the adult mosquitoes to emerge. The overall duration from egg to adult varies among other mosquitoes and is hugely influenced by the overall ambient temperature. While the A. gambiae can develop into an adult in 5 days, it takes about 10 to 14 days in case of tropical climatic conditions.
Adults: just like other mosquitoes, the Anopheles mosquitoes tend to have rather slender bodies containing three sections, head, thorax as well as abdomen. The head of this type of mosquito contains eyes as well as long of various segmented antennae. The antenna is used for the overall detection of the host odors of breeding sites, particularly where females tend to lay their eggs. The head of the Anopheles gambiae mosquito tends to have a rather elongate, a projection forward also called the proboscis that issued for feeding as well as a two sensory organ called the palps. The thorax of the mosquito is specifically modified for the purpose of locomotion with three pairs of legs as well as a pair of wings that are attached to the thorax. On the other hand, the abdomen of the Anopheles gambiae mosquito is specially designed for the purpose of digesting food as well as eggs development. When a female takes a blood meal, this type of segmented body parts tends to expand considerably (Rhodes, Thomas, & Michel, 2018). The blood that is taken often takes time to be digested and thus serves as the main source of protein. Essentially, this is mostly used for the production of eggs which in the long run tend to fill the abdomen.
Impact of Anopheles Gambiae on the Host Population
Anopheles gambiae has for a long time been associated with various illnesses such as malaria in the sub-Saharan countries where it has caused increased deaths on its hosts. In fact, mosquitoes have had a damaging role to its hosts by causing other diseases such as yellow fever, dengue fever, and encephalitis. While mosquitoes do not cause the disease themselves, they act as caries to these diseases (Dong, Simões, Marois, & Dimopoulos, 2018). Researchers suggest that in areas where a particular disease is not present, there is little chance of people being affected unless other infected people are introduced into the area. The bites of mosquitoes themselves are so annoying and at times the sheer numbers of mosquitoes in a certain area have a huge impact on the host population. The main impact of the Anopheles gambiae is the transmission of malaria parasites called the Plasmodium falciparum. The overall results of the transmission of such parasite are the increased malaria in various sub-Saharan counties despite the fact that there has been an improved health care system.
While the negative effects of Anopheles gambiae are obvious in the ecosystem given the fact that it acts as a vector for carrying malaria, there are some useful roles that people rarely fathomed before in the society and in large the ecosystem (Pitts, Derryberry, Zhang, & Zwiebel, 2017). Nonetheless, there are various user roles that this type of mosquitoes tends to play in the overall ecosystem. As part of the useful role of the Anopheles gambiae, the larvae if this mosquito tends to provide food for various fish as well as other animals due to the fact that they live in water. Additionally, large larvae such as those of the dragonflies provide food for fishes in aquatic life (Isaacs, Lynd, & Donnelly, 2017). On the other hand, the larvae of the mosquitoes tend to eat microscopic organisms in water thus helping the ecosystem in recycling it. In the ecosystem, the adult mosquitoes tend to make them up some part of the diet of animals that feeds on insects for survival. Some of the insect-eating animals that hugely benefits in eating birds include the bats, adult dragonflies as well as spiders. Just like other insects, a mosquito helps in the pollination parts of flowers especially when they consume the nectars on the flowers.
While people might be striving to control the spread or rather the transmission of malaria or other diseases by eradicating mosquitos, a scientist has a different take on this matter in contemporary society. The problem of getting rid of mosquitoes is that people do not know everything surrounding mosquitoes yet. Apparently, this is because they might be useful in ways that people do not know and is therefore not advisable to eradicate them completely. Additionally, is the hope of many that valuable medicine will be identified from mosquitoes in the near future (Fu, Dimopoulos, & Zhu, 2017). Despite the fact that a mosquito does not play a vital role in the ecosystem, various insecticides that are used to kill them have been proven to harm as well other creatures that were not intended to be killed by the insecticides. Notably, this calls for effective interventions that do not interfere with the ecosystem itself.
There are various management techniques that can be used to control the overall population of mosquitoes with an aim of reducing the transmission of malaria in a particular region. Some of the effective and efficient methods that are used in the contemporary society includes educating the society regarding malaria as well as the overall role of mosquitoes in the transmission of this illness and modification of environment as well as households to make sure that the entry of mosquitoes have been minimized while reducing the sites that larvae are likely to develop (Chouaïbou, Fodjo-Behi-Kouadio, & Djogbenou, 2017). Additionally, some of the methods that may be used include the provision of treated bed nets, indoor residual spraying (IRS), and the use of spatial repellent (Centers for Disease Control and Prevention., 2015). Some of the proposed management techniques include the initiates to introduce biological controls including predators, the application of sterile, as well as the release of mosquitoes that have been modifying genetically.
The introduction of bed nets that have been treated across sub-Saharan countries has helped in the reduction of the prevalence of mosquitoes in the countries. The overreliance on the insecticides is like to create or rather the population of mosquitoes which are resistant to drugs in the long run. In fact, according to studies that were conducted in Uganda, Anopheles gambiae mosquitoes were found to be extremely resistant to insecticides such as the pyrethroid. The increase in the resistance levels tends to decreases the level or rather the overall efficacy level of the pyrethroids in treated bed nets (Ramirez, Barletta, & Barillas-Mury, 2017). As a result, there is a need for carrying out experiments as well as monitoring strategies to the effect of insecticides occasionally. Moreover, the aspect of home and environmental modification can as well result to rather dramatic changes the abundance. Screens that are placed on windows, as well as those on Windows, can work a long way in the reduction of the spread of malaria cases in a particular area. On the other hand, decreasing the number of breeding sites has been tipped to substantially reduce the population of mosquitoes. This can be done by making sure that there is no stagnant water by making sure that there is periodic draining of fish ponds as well as occasionally draining out rice fields.
Conclusion
Malaria control strategies in tropical Africa have no doubt become one of the most preoccupations among the health workers in contemporary society in those areas. Compared to any other endemic illness, the campaign to reduce the overall transmission of malaria ought to be given a lot of importance while conducted energetically as well as judicious manner. Without the previous knowledge behind the biological aspect of vector causing malaria, the campaign may be ineffective and dangerous to be carried out.
It was important to note that the egg-adult cycle of the Anopheles gambiae varies especially to control the transmission and control of the mosquito’s population across the areas that are hugely affected. As a result, various management or rather control strategies were set out with an aim of not only controlling the spread of malaria in the sub-Saharan regions but as well to reduce the overall population of mosquitoes in these areas. Notably, the paper identified methods of control such as the use of pesticides, use of treated nets, occasionally draining out stagnant water in a particular area to reduce the breeding sites. The research as well identified Anopheles gambiae as being mosquito with the highest levels of resistance especially when using pesticides. This tends to reduce the efficacy of particular insecticides thus calling for biological control methods such as the coming up with genetically modified mosquitoes to reduce the existing mosquitoes. While the study identified various negative impacts of the mosquitoes, it as well showcased the roles Anopheles gambiae mosquitoes has in the ecosystem such as acting as food to the fish and other animals in the environment.
References
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