Malaria represents a severe and mainly fatal infectious disease that emerged thousands of years ago. Despite the advances in medicine, it continues to afflict hundreds of millions people yearly throughout the world. The majority of death from malaria occurs in sub-Saharan Africa, whereas poverty and tropical climate create favorable conditions for the spread of the disease in this area. This paper will reveal the concept of malaria, its causative agent, signs, and symptoms, explain epidemiology of the disease, and identify effective methods of its prevention.
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Concept of the Disease
Scientists assure that malaria existed in ancient societies long ago. The ancient Romans thought that stinky gases from swamps were the cause of marsh fever and called them mala aria that means “bad air”. Therefore, the disease was called malaria. Until 1897, people did not possess sufficient information regarding the cause of the malaria. The works of Italian scientist Camillo Golgi and British physician Donald Ross uncovered the Plasmodium parasite, the cause of human malaria, and the way of its transmission, accordingly. Most probably, malaria originated in tropical Africa. The earliest infections belonged to zoonotic, since the mosquitoes took blood meals from gorillas infected by simian malarias and then transferred the infection to humans via the bite. Infected mosquitoes are able to leave parasites in the human blood, which reproduce and thereby, worsen human health. Currently, the timely treatment may prevent fatal outcome.
Cause of Malaria
Malaria refers to a mosquito-borne communicable disease. Female Anopheles species mosquitoes transmit the above-mentioned disease to humans. Besides, malaria can be transferred from pregnant infected women to her fetus. People also may acquire malaria via the blood transfusion or reusing needles to inject drugs. The causative agent of malaria is protozoan parasites that belong to the genus Plasmodium. They represent single-celled organisms, which require the host for survival. More than hundred species of Plasmodium are known, which infect rodents, reptiles, birds, and monkeys. However, only five of them can lead to human malaria: Plasmodium falciparum, Plasmodium ovale, Plasmodium malariae, Plasmodium vivax, and Plasmodium knowlesi. Plasmodium falciparum and Plasmodium vivax cause the most severe form of malaria and entail the largest number of human death. Whereas Plasmodium vivax can survive in cooler climates, it is more widespread compared to Plasmodium falciparum. Plasmodium ovale and Plasmodium malariae result in a milder form of disease that ordinarily is not deadly for humans. Plasmodium knowlesi refers to zoonosis that commonly infects macaques but can also cause malaria in humans.
When any of five Plasmodium parasites enters the human bloodstream, it moves to the liver. It infects hepatocytes, the liver cells, multiplies there asexually, and forms the merozoites. Thereafter, they rupture hepatocytes and return into the bloodstream. The merozoites invade erythrocytes, the red blood cells, and continue to multiply. Periodically, they infect new blood cells. It is difficult for the human immune system to detect the parasite, since it remains relatively invisible within the liver and erythrocytes.
Plasmodium parasites cause various symptoms within human body. Therefore, uncomplicated and severe forms of malaria disease can be distinguished. The first signs of the disease appear from 7 to 30 days after infection. In case Plasmodium falciparum enters the human blood, the first symptoms arise in a shorter period of time. Plasmodium malariae requires more time to develop the symptoms. Since the manifestation of the initial symptoms needs much time, physician can make the wrong or delayed diagnosis that prevents timely and appropriate treatment.
Uncomplicated form of malaria begins with flu-like symptoms, such as headache, weakness, loss of appetite, high fever, and chills. Diarrhea, nausea, vomiting, and body ache are also manifested. The fever attacks every 48 to 72 hours. It is explained by the fact that the erythrocytes full of parasites are released into the bloodstream periodically. Plasmodium vivax, Plasmodium falciparum, and Plasmodium ovale belong to the so-called “tertian” parasites. They provoke fever every second day. Plasmodium malariae, or “quartan” parasite, in its turn, entails fever attacks every third day. However, it is rarely observed. Malaria attacks consist of three stages. During the first stage a person feels cold and shivering. The second stage includes fever, vomiting, and headache. Lastly, on the third stage, a person’s temperature returns to normal. Besides, a person sweats and feels tiredness.
Plasmodium falciparum ordinarily results in severe malaria. This serious form of disease has harmful impact on organ’s functioning. The complications that are observed in a case of severe malaria include acute respiratory distress syndrome, kidney failure, decrease of blood sugar, also known as hypoglycemia, parasitemia, and low blood pressure. Since parasites continue to destruct the red blood cells, severe anemia also can develop. However, the most life-threatening consequence of severe malaria is infection of cerebrum that leads to cerebral malaria. Excessive sleepiness, seizures, unconsciousness, and coma characterize this neurological complication.
Prompt and proper treatment can prevent the human death. An individual’s spleen tends to swell in a case of infection with Plasmodium. Therefore, an enlarged spleen is a major sign that helps doctor suspect malaria. With the aim to confirm diagnosis, the microscopic examination of blood should be used. If the presence of Plasmodium in any of the blood cells is detected, a person surely is infected with malaria. Appropriate treatment eliminates the symptoms of malaria during two weeks. Inadequate treatment, in its turn, results in periodic malaria attacks over years. Repeated exposure ensures humans with partial immunity to malaria, and milder form of disease can develop.
Epidemiology of the malaria
Tropical and sub-tropical areas with its warm and wet climate create favorable conditions for Anopheles mosquitoes breeding. Slow-moving water is an excellent place for mosquitoes to lay their eggs. Temperature above 16ºC is dominant almost all year in many tropical and sub-tropical countries. Therefore, mosquitoes remain active during a long period of time there and can transmit malaria. Currently, the epicenter of malarial infection remains tropical Africa. According to estimates of malariologists, approximately 90 percent of all human death from malaria occurs there. Sub-Saharan regions of Africa have hot and humid climate that is perfect for malaria-carrying mosquitoes. Many cases of malaria are also reported in southern Asia, in countries such as Indonesia, India, Bangladesh, Thailand, and Myanmar. Approximately four million of malaria cases occur there annually. However, the human deaths from malaria are less common in southern Asia than in Africa, whereas there is not so dangerous type of malaria parasite.
Malaria poses a significant threat to the nations of central Asia. Afghanistan and Pakistan have thousands of malaria cases per year. People in Eastern Asia and the Pacific are also at risk for malaria infection. Moreover, Central and South America have a proper condition for malaria transmission. As for Europe, it is free of malaria due to inhospitable climate for malaria-carrying mosquitoes.
Malaria can affect anyone from newborns to elder persons. People, who live in poverty, are at greater risk of getting malaria. Poor families cannot afford critical tools to prevent malaria transmission. Moreover, they cannot get proper medications needed to treat this infectious disease. Human activities contribute to the reemergence of malaria. Inadequate land use, global warming, and modern transportation create perfect conditions for spread of malaria. In addition, this disease developed resistance to medication that complicates its treatment.
Malaria belongs to a preventable disease. Personal protection allows people to defend themselves from the bites of infected mosquitoes. Since mosquitoes are more active at dawn and dusk, people should stay indoors during this time in malaria-stricken regions. Both mosquito nets and bed nets are effective protective barriers, whereas hinder mosquitoes to bite people. Clothing that covers human arms and legs also refers to necessary protection. In a case people cannot avoid mosquitoes, they should use insect repellents that are sprayed directly on the skin. Such repellents are harmless to people and help prevent the bites.
Public health officials implement various methods to control Anopheles mosquitoes. With the aim to reduce mosquitoes breeding, standing water should be eliminated. Fountains, swimming pools, and roof gutters provide unlimited possibilities for mosquitoes’ reproduction. Since it is impossible to drain all places with water, people use chemicals that designed to kill mosquitoes and its larvae. Such chemicals are called insecticides and larvicides, respectively. Insecticides used to kill adult mosquito include pyrethrin and malathion. Methoprene, monomolecular films, temephos, chlorine, and temephos belong to lavricides. Bacteria are also used to control mosquitoes breeding. Certain types of bacteria, such as Bacillus thuringiensis israelensis and Bacillus sphaericus, are destructive to mosquitoes’ larvae. Lastly, Gambusia, or the so-called mosquito fish, relates to effective protective measure, whereas can eat approximately one hundred larvae daily. Breeding this fish is helpful in controlling mosquito population.
In conclusion, many millions of people die from malaria annually. The largest number of human deaths occurs in sub-Saharan Africa. Malaria is a severe mosquito-borne infectious disease. Female Anopheles mosquitoes can infect people with Plasmodium parasites that result in malaria. The symptoms of the disease are the following: fever, nausea, vomiting, chills, and tiredness. Severe form of malaria leads to damage of brain tissue, kidney failure, and anemia. Mosquito nets, insect repellents, and special clothing prevent people from the malaria infection.
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