Vectors and Pathogens.
According to Nelson Williams (2006), malaria is a vector borne disease that is highly infectious. Spread of malaria is through the bite of an infected female anopheles mosquito. The female anopheles mosquito feeds on blood thus they are the ones involved in the transmission of malaria. Malaria is caused by protozoa of genus plasmodium. The red blood cells are the ones that are affected by malaria causing protozoa.
There are four different types of the genus plasmodium whose presence in circulation causes malaria. These are plasmodium malariae, plasmodium vivax, plasmodium falciparum, and plasmodium ovale. The dominant plasmodium species in Africa is plasmodium falciparum. Plasmodium vivax is commonly found in central and other parts of South America, northern parts of Africa, and Middle East. Plasmodium ovale are mostly found in West Africa. Infection by plasmodium falciparum develops very serious and life threatening malaria (Davis, 2010).
Natural reservoir
The development of plasmodium occurs in the digestive system of the anopheles mosquito. Through a mosquito bite, the pathogens are transmitted into circulation by means of saliva. Plasmodium pathogens are then transported through circulation in the victims liver. They then invade the liver cells and multiply. Spread of malaria involves two hosts, the anopheles mosquito and humans (Nelson Williams, 2006). These parasites utilize man as the main natural intermediate host. The mosquito acts as the ultimatedefinitive host. Plasmodium parasites may affect higher primates with the exception of plasmodium malariae which do not have a natural animal reservoir. For transmission to occur, a human reservoir of viable sexual forms of the parasite must be available. People who harbor malaria parasite for a very long time without displaying symptoms of malaria act as reservoirs during long dry spells.
Characteristics of plasmodium pertinent to disease transmission
Plasmodium parasites depending on the phase of their life cycle can reproduce both sexually and asexually. Asexual reproduction occurs in man while sexual reproduction occurs in mosquitoes. The asexual forms of the parasite are immature trophozoites and schizonts. The sexual forms are the gametocytes.
Reproduction of the parasite in the sexual phase takes place on the digestive system of the mosquito. This makes it very easy for transmission. Saliva contains a lot of these parasites and once a mosquito that had fed on blood from an infected person feeds on another person, it introduces saliva containing the pathogens to that person. These parasites enter the liver and later reinvade the red blood cells. Transmission of malaria by mosquitoes is perfected by the fact that these parasites invade the red blood cells making them easily ingestible by mosquitoes. Plasmodium malariae has the ability of remaining in human hosts for a very long time and still remain infectious to mosquitoes (Cook Zumla, 2008).
The female anopheles mosquitoes once infected with the parasites remains like that for ever. This means that they can transmit the parasite each time it feeds on blood, usually after every two to three days, from a human host.
2. Morphology, Species, and Natural Habitat of the Vector
Morphology
The anopheles mosquito has four life stages with the adult stage acting as the vector for malaria. The mosquitoes have got proboscis that projects forward that they use for feeding. The abdomen of the mosquito is specialized where development of eggs and food digestion takes place. Female anopheles mosquitoes ingest blood that is used in eggs development (Kakkilayas, 2006).
Species
There are various species of the genus anopheles, mosquitoes. Though there are more than one hundred species of genus anopheles mosquitoes, only about 80 of these transmit malaria to humans. 66 of these species are taken as natural vectors and approximately 50 of these species are considered important vectors. Those that transmit include anopheles gambiae, anopheles funestus, and many others (Kakkilayas, 2006). The ability of a species to transmit malaria depends on the preference of the mosquito to feed on human, their average life span, and the natural ability of these species to allow the parasite to develop in them. The behavioral patterns of different species and vector competence may vary between environmental areas.
Natural habitat
Anopheles mosquitoes do not live for more than 1-2 weeks in nature. Their life span highly relies on humidity, temperature, blood meal availability, and ability to evade hosts defense mechanism. Most of the anopheles species mainly thrive on colder latitudes. They are commonly found in areas that have high levels of humidity and temperatures ranging from 20c to 30c. These vectors are mainly found in places like Asia and Africa (Kakkilayas, 2006).
Some anopheles species breed on streams, stagnant water and swampy vegetations. The eggs of the anopheles species requires that they be laid on the water directly. Their larvae are found on streams which flow slowly and contain vegetation and are exposed to some sunlight. Anopheles gambiae which is the most important vector for malaria in Africa particularly breeds in small ponds that are uncovered. During the rainy season, the humidity increases favoring the survival of anopheles mosquitoes. Breeding also increase during this period due to increased amount of water that offers favorable breeding sites. Excess rainfall may however, wash away the larvae and pupae.
Malaria is a disease caused by protozoa known as plasmodium. It is transmitted by vectors mainly female anopheles mosquito. Though there are numerous species of the anopheles mosquito, not all are known to transmit malaria. The female anopheles mosquito feed on blood from human thereby spreading the disease. The species of anopheles mosquito are mainly found in the tropics. They mainly breed in areas with moderate temperatures and high humidity.
There are four different types of the genus plasmodium whose presence in circulation causes malaria. These are plasmodium malariae, plasmodium vivax, plasmodium falciparum, and plasmodium ovale. The dominant plasmodium species in Africa is plasmodium falciparum. Plasmodium vivax is commonly found in central and other parts of South America, northern parts of Africa, and Middle East. Plasmodium ovale are mostly found in West Africa. Infection by plasmodium falciparum develops very serious and life threatening malaria (Davis, 2010).
Natural reservoir
The development of plasmodium occurs in the digestive system of the anopheles mosquito. Through a mosquito bite, the pathogens are transmitted into circulation by means of saliva. Plasmodium pathogens are then transported through circulation in the victims liver. They then invade the liver cells and multiply. Spread of malaria involves two hosts, the anopheles mosquito and humans (Nelson Williams, 2006). These parasites utilize man as the main natural intermediate host. The mosquito acts as the ultimatedefinitive host. Plasmodium parasites may affect higher primates with the exception of plasmodium malariae which do not have a natural animal reservoir. For transmission to occur, a human reservoir of viable sexual forms of the parasite must be available. People who harbor malaria parasite for a very long time without displaying symptoms of malaria act as reservoirs during long dry spells.
Characteristics of plasmodium pertinent to disease transmission
Plasmodium parasites depending on the phase of their life cycle can reproduce both sexually and asexually. Asexual reproduction occurs in man while sexual reproduction occurs in mosquitoes. The asexual forms of the parasite are immature trophozoites and schizonts. The sexual forms are the gametocytes.
Reproduction of the parasite in the sexual phase takes place on the digestive system of the mosquito. This makes it very easy for transmission. Saliva contains a lot of these parasites and once a mosquito that had fed on blood from an infected person feeds on another person, it introduces saliva containing the pathogens to that person. These parasites enter the liver and later reinvade the red blood cells. Transmission of malaria by mosquitoes is perfected by the fact that these parasites invade the red blood cells making them easily ingestible by mosquitoes. Plasmodium malariae has the ability of remaining in human hosts for a very long time and still remain infectious to mosquitoes (Cook Zumla, 2008).
The female anopheles mosquitoes once infected with the parasites remains like that for ever. This means that they can transmit the parasite each time it feeds on blood, usually after every two to three days, from a human host.
2. Morphology, Species, and Natural Habitat of the Vector
Morphology
The anopheles mosquito has four life stages with the adult stage acting as the vector for malaria. The mosquitoes have got proboscis that projects forward that they use for feeding. The abdomen of the mosquito is specialized where development of eggs and food digestion takes place. Female anopheles mosquitoes ingest blood that is used in eggs development (Kakkilayas, 2006).
Species
There are various species of the genus anopheles, mosquitoes. Though there are more than one hundred species of genus anopheles mosquitoes, only about 80 of these transmit malaria to humans. 66 of these species are taken as natural vectors and approximately 50 of these species are considered important vectors. Those that transmit include anopheles gambiae, anopheles funestus, and many others (Kakkilayas, 2006). The ability of a species to transmit malaria depends on the preference of the mosquito to feed on human, their average life span, and the natural ability of these species to allow the parasite to develop in them. The behavioral patterns of different species and vector competence may vary between environmental areas.
Natural habitat
Anopheles mosquitoes do not live for more than 1-2 weeks in nature. Their life span highly relies on humidity, temperature, blood meal availability, and ability to evade hosts defense mechanism. Most of the anopheles species mainly thrive on colder latitudes. They are commonly found in areas that have high levels of humidity and temperatures ranging from 20c to 30c. These vectors are mainly found in places like Asia and Africa (Kakkilayas, 2006).
Some anopheles species breed on streams, stagnant water and swampy vegetations. The eggs of the anopheles species requires that they be laid on the water directly. Their larvae are found on streams which flow slowly and contain vegetation and are exposed to some sunlight. Anopheles gambiae which is the most important vector for malaria in Africa particularly breeds in small ponds that are uncovered. During the rainy season, the humidity increases favoring the survival of anopheles mosquitoes. Breeding also increase during this period due to increased amount of water that offers favorable breeding sites. Excess rainfall may however, wash away the larvae and pupae.
Malaria is a disease caused by protozoa known as plasmodium. It is transmitted by vectors mainly female anopheles mosquito. Though there are numerous species of the anopheles mosquito, not all are known to transmit malaria. The female anopheles mosquito feed on blood from human thereby spreading the disease. The species of anopheles mosquito are mainly found in the tropics. They mainly breed in areas with moderate temperatures and high humidity.
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