Lifecycle of Malaria

life cycle

The natural history of malaria involves periodic human infection and anaphylaxis. In humans, parasites grow and multiply first in liver cells and then in red blood cells. In the blood, the successive incubation of the parasites grows inside the red cells and destroys them, and the parasites of the daughter ("merozite") that continue in the cycle invade other red cells.

Blood stage parasites are those that cause the symptoms of malaria. When certain forms of the blood stage parasites (gametocytes, which occur in the form of males and females) are ingested during the feeding of blood by the mosquito Anopheles, they mate in the intestines of mosquitoes and begin a cycle of growth and reproduction in mosquitoes. After 10-18 days, the form of parasites called sporozoite moves to salivary glands of mosquitoes. When anopheles mosquitoes take a blood meal on another human, the anti-clotting saliva is injected with sporozoites, which migrate to the liver and thus begin a new cycle.

Thus, infected mosquitoes transmit the disease from one person to another (acting as a "vector"), while infected humans transmit the parasite to the mosquitoes. Unlike the human host, mosquitoes do not suffer from parasites.

The life cycle of malaria parasites includes hosts. During the blood meal, the malaria-infected female infects the pimples in the human host. Sporozoites infect liver cells and mature in schizonts, which rip and release merozoites. (P. vivax and P. ovale note that the hypnozoites can persist in the liver (if not treated) and cause relapses by invading the weeks of the bloodstream, or even years later.) After this initial recurrence In the liver (schizophrenia), the parasites multiply without sex in red blood cells (erythrocytes). Merozoites infect red blood cells. The stage arms mature stage in the schizonts, which rip the launch of merozoites. Some parasites differ into the stages of the erythrocytes (chorionic cells). Blood stage parasites are responsible for the clinical manifestations of the disease. Female mosquitoes (microgametocytes) and females (macrogametocytes) are swallowed by the anopheles mosquito while taking blood. The proliferation of parasites in mosquitoes is known as the sporogonic cycle. While in the mosquito's stomach, tiny microglyces penetrate the microgytes. In turn, the zygote becomes moving and extended (oukines) that invade the mucus wall from the mosquitoes, where they develop into eggs. Oocytes grow and tear and release pimples, which make their way to salivary glands of mosquitoes. The vaccination of sporozoites in a new human host perpetuates the life cycle of malaria.

More about: mosquito mosquitoes

More about: Malaria parasites

Human factors and malaria

Biological characteristics and behavioral traits can affect the risk of an individual becoming infected with malaria and, on a larger scale, the severity of population transition.

Malaria environment

Where does malaria happen?

For the transmission of malaria to occur, conditions must be so that the three components of the malaria life cycle are present:

Anopheles parasites, which can feed on humans, in which parasites can complete half of the host of invertebrates from their life cycle

Humans. Who can invoke the mosquito of Anophilis, through which parasites can complement the host of vertebrates from half their life cycle

Malaria parasites.

climate

Climate is one of the major determinants of both geographical distribution and seasonal malaria. Without enough precipitation of rain, mosquitoes can survive, and if they are not warm enough, the parasites can not survive in mosquitoes.

Anophyls develop their eggs in a variety of freshwater or saline bodies, with different species having different preferences. Hatching eggs within a few days, where larvae are produced from 9 to 12 days to develop to adults in the tropics. If the larval habitats dry before the process is complete, the larvae die; if the rains are excessive, they may be destroyed and destroyed. Life is risky for mosquito larvae, where most die before they become adults.

Life is usually short for adult mosquitoes, where temperature and humidity affect longevity. Older females can only transmit malaria, where they must live long enough for pimples to develop and move to salivary glands. This process takes at least nine days when temperatures are warm (30 ° C or 86 ° F) and will take longer at cooler temperatures. If temperatures are too cold (15 ° C or 59 ° F for Plasmodium vivax, 20 ° C or 68 ° F for P. falciparum), evolution can not be completed and malaria can not be transmitted. Malaria transmission is therefore more intense in warm and humid areas, with the possibility of transmission in temperate regions only during the summer months.

Human Factors and Malaria

Genetic Factors

Biologic characteristics present from birth can protect against certain types of malaria. Two genetic factors, both associated with human red blood cells, have been shown to be epidemiologically important. Persons who have the sickle cell trait (heterozygotes for the abnormal hemoglobin gene HbS) are relatively protected against P. falciparum malaria and thus enjoy a biologic advantage. Because P. falciparum malaria has been a leading cause of death in Africa since remote times, the sickle cell trait is now more frequently found in Africa and in persons of African ancestry than in other population groups. In general, the prevalence of hemoglobin-related disorders and other blood cell dyscrasias, such as Hemoglobin C, the thalassemias and G6PD deficiency, are more prevalent in malaria endemic areas and are thought to provide protection from malarial disease.

Persons who are negative for the Duffy blood group have red blood cells that are resistant to infection by P. vivax. Since the majority of Africans are Duffy negative, P. vivax is rare in Africa south of the Sahara, especially West Africa. In that area, the niche of P. vivax has been taken over by P. ovale, a very similar parasite that does infect Duffy-negative persons.

Other genetic factors related to red blood cells also influence malaria, but to a lesser extent. Various genetic determinants (such as the “HLA complex,” which plays a role in control of immune responses) may equally influence an individual’s risk of developing severe malaria.

More on: Sickle Cell and Malaria

Acquired Immunity

Acquired immunity greatly influences how malaria affects an individual and a community. After repeated attacks of malaria a person may develop a partially protective immunity. Such “semi-immune” persons often can still be infected by malaria parasites but may not develop severe disease, and, in fact, frequently lack any typical malaria symptoms.

In areas with high P. falciparum transmission (most of Africa south of the Sahara), newborns will be protected during the first few months of life presumably by maternal antibodies transferred to them through the placenta. As these antibodies decrease with time, these young children become vulnerable to disease and death by malaria. If they survive repeated infections to an older age (2-5 years) they will have reached a protective semi-immune status. Thus in high transmission areas, young children are a major risk group and are targeted preferentially by malaria control interventions.

In areas with lower transmission (such as Asia and Latin America), infections are less frequent and a larger proportion of the older children and adults have no protective immunity. In such areas, malaria disease can be found in all age groups, and epidemics can occur.

Anemia in young children in Asembo Bay, a highly endemic area in western Kenya. Anemia occurs most between the ages of 6 and 24 months. After 24 months, it decreases because the children have built up their acquired immunity against malaria (and its consequence, anemia).

Mother and her newborn in Jabalpur Hospital, State of Madhya Pradesh, India. The mother had malaria, with infection of the placenta.

Pregnancy and Malaria

Pregnancy decreases immunity against many infectious diseases. Women who have developed protective immunity against P. falciparum tend to lose this protection when they become pregnant (especially during the first and second pregnancies). Malaria during pregnancy is harmful not only to the mothers but also to the unborn children. The latter are at greater risk of being delivered prematurely or with low birth weight, with consequently decreased chances of survival during the early months of life. For this reason pregnant women are also targeted (in addition to young children) for protection by malaria control programs in endemic countries.

More on: Malaria During Pregnancy

Behavioral Factors

Human behavior, often dictated by social and economic reasons, can influence the risk of malaria for individuals and communities. For example:

Poor rural populations in malaria-endemic areas often cannot afford the housing and bed nets that would protect them from exposure to mosquitoes. These persons often lack the knowledge to recognize malaria and to treat it promptly and correctly. Often, cultural beliefs result in use of traditional, ineffective methods of treatment.

Travelers from non-endemic areas may choose not to use insect repellent or medicines to prevent malaria. Reasons may include cost, inconvenience, or a lack of knowledge.

Human activities can create breeding sites for larvae (standing water in irrigation ditches, burrow pits)

Agricultural work such as harvesting (also influenced by climate) may force increased nighttime exposure to mosquito bites

Raising domestic animals near the household may provide alternate sources of blood meals for Anopheles mosquitoes and thus decrease human exposure.

Anophilus mosquitoes

Malaria is transmitted to humans by mosquitoes of the genus anophylate. Female mosquitoes take blood meals to produce eggs, and these blood meals are the link between human and mosquito hosts in the parasite life cycle. Successful development of mosquito parasites in mosquitoes (from "chorionic" to "bispozoite") depends on several factors. More importantly, the temperature and humidity of the environment (the high temperature of parasite growth in mosquitoes) and whether the anophila live long enough to allow the parasite to complete its course in the host of mosquitoes (sporogonic or "external"), 9 to 18 days) . Unlike the human host, the mosquito host does not suffer significantly from the presence of parasites.

Female adult mosquito plot

Female adult mosquito plot

Thumbnail of mosquito distribution map.

The world map shows the distribution of prevalent malaria vectors

Anophil Freshoni mosquitoes pump blood

Anophil Freshoni mosquitoes pump blood

Larger image

Slide powerpoint of mosquito freeborni mosquitoes pumping blood

Successive images of mosquitoes take blood meal

general information

There are approximately 3,500 species of mosquitoes grouped in 41 genus. Human malaria is transmitted only by females of the genus Anophyla. Of the approximately 430 species of anopheles, only 30 to 40 species carry malaria (ie, "vectors") by nature. The remainder either infects humans irregularly or can not maintain the development of malaria parasites.

Geographical distribution

Anophylline is found worldwide except for Antarctica. Malaria is transmitted by different types of anophyls in different geographical areas. Within geographic regions, different environments support different types.

Anophylline can be found that can transmit malaria not only in malaria-endemic areas, but also in areas where malaria has been eradicated. These areas are at risk of re-emergence.

life steps

Like all kinds of mosquitoes, anovilous mosquitoes pass through four stages in their life cycle: eggs, caterpillars, baboons and adults. The first three stages are aquatic and last 7-14 days, depending on the species and surrounding temperature. Anopheles mosquitoes may bite malaria. Male mosquitoes do not bite, so can not transmit malaria or other diseases. Adult females are usually short-lived, with only a small proportion of them (enough than 10 days in the tropics) to transmit malaria.

eggs

Adult females put between 50-200 eggs per white case. The eggs are placed individually on the water and are unique in the presence of buoys on both sides. The eggs are irresistible to dry and hatch during 2-3 days, although hatching may take up to 2-3 weeks in cold climates.

Larvae

Mosquito larvae have a sophisticated head with mouth brushes used for feeding, a large chest, and a fragmented belly. They do not have legs. Unlike other mosquitoes, anophyla larvae lack a respiratory siphon and for this reason their body is placed parallel to the surface of the water.

Top: Anophilus eggs. Notice floating lateral. Bottom: Single anophila eggs are placed

Top: Anophilus eggs. Notice floating lateral.

Bottom: Single anophila eggs are placed.

Larvae breathe through the spiracles located on the eighth abdominal part, and therefore must come to the surface frequently.

Larvae spend most of their time feeding on algae, bacteria and other microorganisms in the small surface layer. They do this by rotating their 180 degrees head and feeding down the microlayer. Larvae sink under the surface only when disturbed. The larvae swim either through the convulsive movements of the whole body or by pushing with mouth brushes.

Larvae develop through 4 stages, or stages, and then turn into pupa. At the end of each stage, larvae fall, and give up their outer structure, or their skin, to allow for further growth.

A picture of anoville larva, floating parallel to the surface of the water

Anophilis is a larva. Note the position, parallel to the water surface.

Larvae occur in a wide range of habitats but most species prefer clean non-polluted water. Anopheles' mosquitoes were found in freshwater or saline swamps, mangrove swamps, rice paddies, weed pits, tributaries of streams and rivers, and small temporary rainwater ponds. Many species prefer habitats with vegetation. Others prefer habitat that contains nothing. Some of them thrive in open sunlit ponds while others are found only in shaded breeding sites in the forest. Some species reproduce in tree holes or leaf hubs of some plants.

The cocoons

The cocoon is a comma when viewed from the side. This is a transitional stage between the larva and the adult. Crocodiles do not feed, but undergo radical transformation. The head and chest are incorporated into the vertical head with the abdominal curvature around it. As with larvae, cocoons must come to the ornamental surface.