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How to Protect Yourself Against Malaria 1 4 From our Whitepaper Files: How to > See companion document Protect Yourself Against Malaria World Malaria Risk Chart 2020 Edition This content is no longer being reviewed or updated. Last update: December 11, 2020. Canada 67 Mowat Avenue, Suite 036 Toronto, Ontario M6K 3E3 (416) 652-0137 USA 1623 Military Road, #279 Niagara Falls, New York 14304-1745 (716) 754-4883 New Zealand 206 Papanui Road Christchurch 5 www.iamat.org | [email protected] THE ENEMY area. Of the 460 Anopheles species, approximately 100 can transmit malaria Sunset — the hunt for human blood begins. parasites. From dusk to dawn the female Anopheles, Mosquitoes prey on a variety of hosts — the malaria-carrying mosquito, searches for humans, monkeys, lizards, birds — carrying a host to supply her with blood. Blood is an different species of malaria parasites which absolute necessity for her because it provides the in turn infect only specific hosts. Of the protein needed for the development of her eggs approximately 50 different species of malaria which she later deposits in her breeding place. parasites sharing the genetic name Plasmodium, She has a tiny, elegant body, measuring only 5 infect humans: Plasmodium falciparum from 8 mm to 1 cm. She has dark spots on (the killer parasite); Plasmodium vivax; her wings, three pairs of long, slender legs and Plasmodium ovale, Plasmodium malariae and a prominent tubular proboscis with which Plasmodium knowlesi. The latter, a malaria she draws blood. parasite of Old World monkeys, has been Fig. 1 Female Anopheles mosquito. The Anopheles enters your room at night. identified to infect humans in Southeast Asia. Image source: World Health Organization You may recognize her by the way she rests In the past this parasite has been misdiagnosed on the wall — she stands on her head with the as Plasmodium malariae. tail-end of her body tilted upwards, protruding Malaria parasites are older than human- into the air like a rocket on a launching pad. kind. They have accompanied the evolution of Malaria parasites are older She is unlike the common pests of our temperate primates throughout the geological ages from climates, the Culicinae (Culex, Aedes, etc.), which their earliest ancestors up to the emergence of than humankind. They have assume a position parallel to the surface. humans. The parasites, too, underwent adaptive accompanied the evolution She is your enemy, because only she can changes and it is believed that the Plasmodium of primates throughout the harbour the human malaria parasite and carry falciparum, which causes the fatal form of geological ages from their it from an infected person to a new victim human malaria, is the latest evolved species of earliest ancestors up to the (male mosquitoes do not bite). In fact, in the parasite. The benign Plasmodium malariae, East Africa the same word, umbu, means both the oldest on the scale of evolution, may have emergence of humans. malaria and mosquito. Around the world, she been the first to invade humans. infects more than 200 million people with malaria and kills an estimated 430,000 people, THE BITE mostly children. The unprotected international traveller Now that she has entered your premises, the pays her a heavy toll — she is responsible for Anopheles waits patiently in a dark corner for the infecting thousands with malaria every year. right moment to strike. Attracted by the warmth Her bite is the direct cause of death for many of your body and the carbon dioxide you exhale, who contract the disease in their travels. she approaches silently. She does not hum or hover The more than 3,500 species of mosquitoes as other mosquitoes do. are grouped into the family of Culicidae, of In a moment she will land on an exposed part which the genera Aedes, Anopheles and Culex are of your body and pull out from her proboscis the most widespread. Throughout the world, her armament, consisting of six stylets. First, two each species of Anopheles is peculiar to a localized needle-pointed stylets will stab your skin, then two How to Protect Yourself Against Malaria 1 4 i q r s h z l w v u t g m p n b a c o 1 f e 3 2 d Fig. 2 Life cycle of the malaria parasite. blades bearing very fine teeth will lacerate the THE THREE LIVES OF skin like a microscopic saw, searching for a small THE MALARIA PARASITE vein. Soon she pierces the vessel with a flexible tube, the “food canal” through which blood is The malaria organism is a protozoan conveyed into her mouth. During the feeding, (Gr.: proto=primitive; zõon=animal), that is to she will introduce into the wound her sixth say a microscopic, single-celled animal, not to weapon, a hollow stylet containing a duct be confused with a bacterium, which belongs to which is connected to the salivary glands. the plant kingdom. The parasite has a complex Through this duct she injects a few drops of her life cycle, reproducing first in the liver, then in saliva to act as a local anaesthetic so that you do the red blood cells and finally in the mosquito. not feel her bite. During these three cycles the parasite transforms Simultaneously with her saliva she will itself and emerges each time with new physical introduce into your bloodstream hundreds and biochemical characteristics. of motile sporozoites (Gr.: sporá=sowing, seed; zõon=animal). She acquired these organisms from The Liver: Hiding Place of the Parasite biting a person infected with malaria. They have The malaria organisms (sporozoites) injected into been multiplying in her intestine for two weeks. the body by the bite of the infected mosquito Soon she will fly away, loaded to twice her remain in the bloodstream for only a short period unfed weight with blood, to conceal herself in — see the illustration of the Life Cycle of the The most dangerous species a dark corner of your room. During the forty- Malaria Parasite (Fig. 2) — usually less than one eight hours it takes to digest the blood she has hour. They disappear from the circulation and of Anopheles attack humans taken, her ovaries will completely develop and she establish themselves in the cells of the liver (2a), between dusk and dawn; will be ready to lay her eggs. where they commence cycles of reproduction, a midnight to 4 am is the peak At sundown she will leave your room for her process lasting from six to twelve days, depending time. This means you are breeding place nearby. She can breed almost on the species. This stage corresponds to the in- a prime target when you are anywhere water collects — a footprint, a puddle, cubation period of the disease. During this time, a tire track, even a coconut shell or a man-made each sporozoite grows through repeated divisions most vulnerable — asleep. container. After laying her eggs, her ovarian cycle of the nucleus into one large cell named schizont starts again, and she may return to see you the (Gr.: schizein=to divide; ontos=being), now con- same night. During her three-month life span she taining thousands of tiny new parasites (2b). may lay up to three thousand eggs. The increased pressure causes the schizont This shuttling between blood source and to burst and release these newly formed parasites, breeding place makes malaria a ‘focus’ disease; called merozoites (Gr.: meros=part, zõon=animal) that is to say, its area of infective activity is (2c), which leave the liver and enter the localized and dependent upon the radius of red blood cells where they initiate cycles of the flight range of the Anopheles, usually from reproduction. a few hundred yards to a mile. On entering the liver, all sporozoites of Plas- The most dangerous species of Anopheles attack modium falciparum, Plasmodium malariae, and humans between dusk and dawn; midnight to Plasmodium knowlesi immediately enter into a 4 am is the peak time. This means you are a prime reproductive phase which exhausts itself after one target when you are most vulnerable — asleep. generation. If you are harbouring an infection IAMAT Whitepaper Files 2 caused by these parasites, suppressive medication When the Anopheles bites an infected person, will eliminate the parasites from the red blood the merozoites drawn from the bloodstream are cells, and because no new invasions from the digested in the stomach of the mosquito, liver can occur, you will be completely cured of while the gametocytes (4q) develop in the the infection (2a, 2b, 2c). intestine into mature cells called gametes, the However, Plasmodium vivax and Plasmodium female ovule and the male spermatozoon (4r). Like humans, anopheline ovale enter the liver cell as two different forms The fertilized eggs, ookinete (Gr.: õon=egg; mosquitoes are concerned of sporozoites: one strain immediately enters kinesis=motion) (4t), moves to the outside wall with food, shelter and into a phase of reproduction (2a, 2b, 2c); and of the mosquito gut where, by secreting a cyst the other, called hypnozoite (Gr.: hypno=sleep, wall around itself, it develops into an oocyst reproduction. Will she feed zõon=animal), lies dormant in the liver cell (2d (4u, v), which will give rise to a myriad of on humans or on domestic red cell). The hypnozoites enter into reproduc- new parasites, the sporozoites. As soon as these animals? Will she enter tive phases at different times(2e, 2f), even after sporozoites (4z) are released from the oocyst they human dwellings to bite or will months or years, depending upon the species, migrate to the salivary glands of the Anopheles, she feed outdoors? Does she and are therefore responsible for the well-known waiting to be injected into the next victim.
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