What is Malaria?
Malaria is a tropical disease spread by mosquitoes. It is prevalent in most tropical and sub-tropical countries and remains a serious public health problem. In 2011, it was estimated that around 3.3 billion people were at risk for malaria. Malaria is the most significant health hazard facing travelers to tropical countries. According to the World Health Organization (WHO) report, in 2010 there were 219 million cases of malaria, most of which (80%) occurred in the African region. In the same year there were 660,000 deaths due to malaria, 91% of which occurred in Africa and 86% of which occurred in children under the age of five.
What causes malaria?
There are five types of parasite that can cause malaria: Plasmodium (P.) vivax, P. ovale, P. malariae, P. knowlesi, and P. falciparum. Anopheles mosquitoes carrying parasites bite their victim and inject infective forms of the parasite into the bloodstream. These infective forms are then passed into the liver where they start to develop into parasites over the course of 6–11 days.
The parasites are then released back into the bloodstream where they begin to infect the red blood cells. A blood sample examined under a microscope will show the presence of the parasites. P. vivax and P. ovale can lie dormant in the liver after a person is bitten, causing recurring symptoms each time a new batch of mature parasites is released into the bloodstream. This is why some people with malaria suffer from intermittent fever.
Anopheles mosquitoes bite at night from dusk until dawn and this is when most protection is needed.
What are the symptoms of malaria?
Symptoms of malaria usually appear around 10–15 days after being bitten by an infected mosquito. However, in some cases symptoms can develop months or even years later, particularly if malaria prevention medication was being taken at the time of infection.
The main symptoms are fever, chills with sweating, headache, muscle aches and malaise. In the early stages, the symptoms may resemble influenza (the flu). Other possible symptoms include abdominal pains, diarrhea, jaundice and coma.
The severity of the disease is related to the number of parasites in the blood, and the type of malaria. Malaria caused by P. falciparum is the most dangerous type and can be fatal. People who live in countries where this type of malaria exists tend to develop some immunity to it, but visitors and children who have no immunity often develop serious or even fatal disease. Severe falciparum malaria can cause symptoms of severe anemia, liver and kidney failure and convulsions. If the brain is affected (cerebral malaria), coma may occur.
Pregnant women are more at risk because resistance to malaria drops during pregnancy. The disease is more frequent and severe in pregnant women. It also increases the rate of miscarriage and stillbirth in infected women. The disease is rarely passed on to the unborn baby but this is more likely to happen in women with no previous immunity, such as travelers.