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Malaria: cycle, symptoms, transmission and treatment

Malaria is an infectious disease transmitted through the bite of the female Anopheles mosquito infected by the protozoan Plasmodium, the most frequent species being Plasmodium vivax and Plasmodium malariae. The best way to prevent malaria is to avoid getting stung because it is transmitted by a mosquito bite, so you should use repellent and window protections, for example.

Once you get infected, Plasmodium goes to the liver, where it multiplies and then reaches the bloodstream, where it invades and breaks red blood cells, causing symptoms such as fever, sweating, chills, nausea, vomiting, headache and weakness.

Malaria has a cure, but it is important that treatment be started quickly, since in many cases the disease can become severe, with anemia, platelet loss, renal failure or even brain impairment, in which the chances of complications and death are much greater.

Malaria: cycle, symptoms, transmission and treatment

Main symptoms

The first symptoms of malaria usually appear between 8 and 14 days after transmission, and can take up to 30 days or more to appear. The appearance of symptoms depends on factors related to Plasmodium, such as multiplication rate and species, and factors related to your individual characteristics, such as your immune system. The most common signs and symptoms of malaria are:

  • Fever, which may arise and disappear in cycles;
  • Sweating and chills;
  • Strong headache;
  • Nausea and vomiting;
  • Muscle pain throughout the body;
  • Weakness and constant tiredness;
  • Yellowish skin and eye.

Most of these symptoms can be difficult to identify as being indicative of malaria and so if they arise it is important to go to the doctor to diagnose the disease and initiate appropriate treatment, especially if you are in a place where malaria is frequent, such as in the region Amazon and Africa, for example.

In addition, these symptoms can appear in cycles, that is, manifest every 48 hours or 72 hours depending on the species of Plasmodium that is infecting the body. This happens because of their life cycle, as they develop they can reach the bloodstream and cause symptoms like red blood cells being destroyed.

The most serious form of malaria occurs when the infection compromises the brain, causing headache, neck stiffness, seizures, drowsiness, and even coma. Other complications include anemia, reduction of platelets, renal failure and respiratory failure.

How is malaria transmitted

Malaria transmission occurs through the bite of an infected female Anopheles mosquito, which acquired the parasite by stinging a person infected with the disease. It is important to remember that malaria is not contagious, that is, it is not transmitted from person to person, except in rare cases of sharing infected syringes and needles, poorly controlled transfusions or childbirth.

Usually mosquitos bite people during dusk or nighttime. The countries most at risk of contamination are South America, Central America, Africa and part of Asia, especially in places with clean water that has little current, humidity and temperature between 20º and 30ºC. 

Malaria infection cycle

Malaria: cycle, symptoms, transmission and treatment

The cycle of the Plasmodium parasite in the human body happens as follows:

  1. The bite of the female Anopheles mosquito transmits, through its saliva, the Plasmodium into the person's bloodstream, in its Sporozoite phase;
  2. The sporozoites travel to the liver, where they mature and multiply, for about 15 days, giving rise to the form of Merozoites;
  3. Merozoites break the liver cells and reach the bloodstream, invading the red blood cells;
  4. Inside the infected blood cells, which are called Schizonts, the parasites multiply and break this cell, and begin to invade others, in a cycle that lasts from 48 to 72 hours.

Within each schizont, the cycle varies according to the Plasmodium species, being 48 hours for the species P. falciparum, P. vivax, and P. ovale and 72 h for P. malariae. During the period when red blood cells are broken and the schizonts become free in the blood, the symptoms may be accentuated, especially fever and chills.

How to confirm the diagnosis

After the first symptoms appear, it is recommended you go to the hospital or the emergency room, especially if the symptoms appear every 48 to 72 hours. In this way, the doctor can identify the presence of the parasite in the body through blood tests, such as immunological tests, and can start the appropriate treatment, preventing the infection from worsening and becoming life-threatening.

How is treatment done

Malaria treatment is done with antimalarial drugs such as Chloroquine, Primaquine, Artemether and Lumefantrine or Artesunate and Mefloquine, for example, which act by destroying Plasmodium and preventing its transmission.

The medications chosen, doses and duration are indicated by the doctor according to your age, severity of the disease and analysis of health conditions. Children, infants and pregnant women need a special treatment with Quinine or Clindamycin, always in accordance with the medical recommendations and, generally, hospitalization is indicated.

It is further recommended you:

  • Eat normally;
  • Do not consume alcoholic beverages;
  • Do not stop the treatment before medical recommendation, even if the symptoms disappear before, because of the risk of relapse and complications of the disease.

Treatment of malaria should be started as soon as possible, as it may evolve severely and, without appropriate treatment, can lead to death.

How to protect yourself

Prevention of malaria can be done through:

  • Wearing light-colored clothing and thin fabric with long sleeves and long pants;
  • Avoid areas prone to contamination of the disease, especially during dusk or dawn, for example;
  • Use DEET (N-N-diethylmetatoluamide) based repellent, respecting manufacturer's directions for repellent replacement;
  • Put mosquito screens on windows and doors;
  • Avoid lakes, ponds and rivers in the late afternoon and evening.

Those who travel to a place where there are cases of malaria can receive a preventive treatment, called chemoprophylaxis, with anti-malarial drugs such as Doxycycline, Mefloquine or Chloroquine, for example.

However these drugs have strong side effects, so the doctor usually indicates this type of prevention for people who are at greater risk of developing serious illness, such as going to places with high rates of transmission or when the person has some disease that may have major complications with the infection.

These medications should only be used after medical advice and are usually started 1 day before the trip and persist for a few days or weeks after returning.


Bibliografia

  • OPAS BRASIL. Folha informativa - Malária. Link: <www.paho.org>. Access in 03 Jun 2019
  • FIOCRUZ. Conheça a Malária. Link: <www.fiocruz.br>. Access in 03 Jun 2019
  • MÉDICOS SEM FRONTEIRAS. Malária. Link: <www.msf.org.br>. Access in 03 Jun 2019
  • MINISTÉRIO DA SAÚDE. Malária: o que é, causas, sintomas, tratamento, diagnóstico e prevenção. Link: <www.saude.gov.br>. Access in 03 Jun 2019
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