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Malaria: Transmission, Symptoms And Treatment

Malaria is an infectious disease caused by protozoa of the genus Plasmodium, transmitted to humans through the bite of mosquitoes of the genus Anopheles

Human malaria is caused by four different species of Plasmodium: Plasmodium Falciparum, Plasmodium Vivax, Plasmodium Ovale and Plasmodium Malariae.

Of these, P. falciparum is particularly dangerous, as it can cause fulminant infections and is resistant to common antimalarial drugs.

Infection caused by P. falciparum can be fatal, especially in children, the elderly and pregnant women.

Malaria is a huge global health problem and is the leading cause of morbidity and mortality in many countries

It is especially widespread in the tropical and sub-tropical regions of the planet, where it causes more than 300 million infections and around one million deaths a year.

In Italy it has disappeared since the 1950s; the cases that occur in our country are mainly the result of tourists returning from malaria-affected countries and immigration from these countries.

Malaria transmission

The infection is transmitted to humans by the bite of a female anopheles mosquito that has previously bitten a sick person.

The parasite multiplies in the mosquito and, through its bite (which does not cause itching or pain), infects the new host.

Thus begins the incubation period, during which the parasites develop in the human liver completely asymptomatically.

The incubation period may be short (7-14 days for P. falciparum infection, 8-14 for P. vivax and P. ovale, and 7-30 days for P. malariae) or may last for several months (as for some strains of P. vivax and P. ovale).

In any case, after this period, the plasmodia manage to evade the immune system and reach the blood, where they attack and destroy red blood cells, thus initiating the symptomatic phase.

Malaria: what are the symptoms

The symptoms of malaria are variable and depend on many factors, primarily the species of the infecting plasmodium and the general health condition of the infected person.

The disease generally presents itself with fever, chills, headache, diffuse sweating, muscle pain, anaemia, gastrointestinal problems, vomiting and abdominal pain.

In the most severe cases (caused mainly by P. falciparum), malaria can cause convulsions, jaundice, renal failure, respiratory failure, haemorrhaging, altered consciousness and coma, and even progress to death.

Malaria attacks, caused by the release of parasites into the bloodstream, occur at intervals of approximately 48 or 72 hours, depending on the type of parasite.

They usually last between 8 and 12 hours. They begin with cold chills, followed by a strong fever, nausea and widespread pain.

The malarial episode ends with a phase of profuse sweating, during which the fever subsides but leaves the sick person tired and exhausted.

Diagnosis and treatment of malaria

The clinical diagnosis is based on observation of the patient’s symptoms.

However, the only way to make a definitive diagnosis of malaria is to detect the presence of the parasite or its components in the blood by means of laboratory tests.

Direct haemoscopy, i.e. the direct observation under a microscope of a drop of blood taken through a finger prick, is considered the ‘Gold Standard’ method.

The examination must be performed either on a thick drop of blood or on a thin smear: the former facilitates diagnosis especially in the case of a low number of parasites, the latter helps to establish the species.

Malaria requires very early diagnosis and treatment, but plasmodia have become highly resistant to almost all antimalarial drugs, especially chloroquine, the least expensive and most widely used antimalarial.

As a result, new drug combinations are increasingly being used.

Particular care must be taken when treating pregnant women with malaria, especially in the last trimester.

Patients suffering from severe P. falciparum malaria or who cannot take oral medication should be treated by continuous intravenous infusion.

The best available treatment, particularly for Plasmodium falciparum malaria, is artemisinin-based combination therapy (ACT).

Malaria prophylaxis

It is important to remember that there is no pharmacological prophylaxis that offers complete protection.

All available drugs have side effects of varying degrees that decrease tolerance and consequently reduce adherence to treatment.

Moreover, antimalarial drugs are sometimes contraindicated, especially in young children and pregnant women, and combination with other drugs may be inadvisable.

The choice of drugs to be used must take into account the different plasmodium species and, above all, the geographical distribution of P. falciparum (resistant to chloroquine).

Protection against mosquitoes is still the best defence against malaria infection.

Here are some tips for preventing contact with the Anopheles mosquito and avoiding its bite

  • sleep in rooms with nets on the windows or use mosquito nets, preferably impregnated with insecticide;
  • wear clothes that do not leave parts of the body uncovered (long-sleeved shirts, long trousers, etc.) and prefer light-coloured clothing (dark colours attract mosquitoes);
  • apply insect repellents to the skin (bearing in mind that sweat reduces their effect) and use mosquito repellent sprays or insecticide dispensers in the room at night;
  • avoid, if possible, going out at night (when mosquitoes usually bite);
  • avoid staying near water and in damp areas.

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