What Is Malaria?

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Main Category: Tropical Diseases
Also Included In: Infectious Diseases / Bacteria / Viruses
Article Date: 20 May 2009 - 2:00 PDT

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The word malaria comes from 18th century Italian mala meaning "bad" and aria meaning "air". Most likely, the term was first used by Dr. Francisco Torti, Italy, when people thought the disease was caused by foul air in marshy areas. It was not until 1880 that scientists discovered that malaria was a parasitic disease which is transmitted by the anopheles mosquito. The mosquito infects the host with a one-cell parasite called plasmodium. Not long after they found out that Malaria is transmitted from human-to-human through the bite of the female mosquito, which needs blood for her eggs.

According to Medilexicon's medical dictionary, Malaria is "A disease caused by the presence of the sporozoan Plasmodium in human or other vertebrate erythrocytes, usually transmitted to humans by the bite of an infected female mosquito of the genus Anopheles that previously sucked blood from a person with malaria…" (Click here to see the complete definition in the dictionary). Malaria is also known as Jungle fever, Marsh fever, Paludal fever

Approximately 40% of the total global population is at risk of Malaria infection. During the 20th century the disease was effectively eliminated in the majority of non-tropical countries. Today Malaria causes over 350 million human acute illnesses, as well as at least one million deaths annually. The anopheles mosquito exists in most tropical and many sub-tropical countries of Latin America and the Caribbean, Africa, Oceania, and Asia.

According to WHO (World Health Organization), the majority of Malaria deaths occur among children in sub-Saharan Africa, killing an African child every 30 seconds. Not only is Malaria associated with poverty, it is also a cause of poverty and an important obstacle to economic development.

There are five types of Malaria:

• Plasmodium vivax (P. vivax) - milder form of the disease, generally not fatal. However, infected people still need treatment because their untreated progress can also cause a host of health problems. This type has the widest geographic distribution globally. About 60% of infections in India are due to P. vivax. This parasite has a liver stage and can remain in the body for years without causing sickness. If the patient is not treated, the liver stage may re-activate and cause relapses - malaria attacks - after months, or even years without symptoms.


• Plasmodium malariae (P. malariae) - milder form of the disease, generally not fatal. However, the infected human still needs treatment because no treatment can also lead to a host of health problems. This type of parasite has been known to stay in the blood of some people for several decades.


• Plasmodium ovale (P. ovale) - milder form of the disease, generally not fatal. However, the infected human still needs to be treated because it may progress and cause a host of health problems. This parasite has a liver stage and can remain in the body for years without causing sickness. If the patient is not treated, the liver stage may re-activate and cause relapses - malaria attacks - after months, or even years without symptoms.


• Plasmodium falciparum (P. faliparum) - the most serious form of the disease. It is most common in Africa, especially sub-Saharan Africa. Current data indicates that cases are now being reported in areas of the world where this type was thought to have been eradicated.


• Plasmodium knowlesi (P. knowlesi) - causes malaria in macaques but can also infect humans.

How does a human become infected with Malaria?

The female Anopheles mosquito transmits the parasite to a human when it takes a blood meal - it bites the human in order to feed on blood. Only the female Anopheles mosquito can transmit malaria, and it must have been infected through a previous blood meal taken from an infected human. When the mosquito bites an infected person a minute quantity of the malaria (plasmodium) parasite in the blood is taken. Approximately one week later that same infected mosquito takes its next blood meal. The plasmodium parasites mix with the mosquito's saliva and are injected into the host (human being).

Human-to-human transmission of Malaria

As the parasite exists in human red blood cells, malaria can be passed on from one person to the next through organ transplant, shared use of needles/syringes, and blood transfusion. An infected mother may also pass malaria on to her baby during delivery (birth) - this is called 'congenital malaria'.

You cannot catch Malaria by just sitting next to an infected person, or breathing in next to them when they cough and sneeze.

What are the symptoms of Malaria?

In areas where Malaria is endemic people may have immunity or semi-immunity, and therefore have either no symptoms or few symptoms. The severity of the Malaria depends on three things: 1. The type of parasite. 2. Your immunity. 3. Whether you still have your spleen.

Early stage symptoms of Malaria

• A high temperature (fever)
• Chills
• Headache
• Sweats
• Tiredness (fatigue)
• Nausea
• Vomiting

Symptoms may occur in cycles, each time they come they might do so at different levels of severity. How long symptoms last may also vary, depending on each cycle. However, at the beginning of the illness, symptoms may not follow this typical pattern.

Other common symptoms may include:

• Dry cough
• Back pain
• Muscle ache
• Enlarged spleen

Very rare symptoms may include:

• Impairment of brain function
• Impairment of spinal cord function
• Seizures (fits)
• Loss of consciousness

People who are infected with the P. falciparum parasite and become ill generally have much more serious symptoms, which may become fatal.

What is the incubation period of Malaria?

Incubation period refers to how long it takes from initial infection to the appearance of symptoms. This generally depends on the type of parasite:

• P. falciparum - 9 to 14 days
• P. vivax - 12 to 18 days
• P. ovale - 12 to 18 days
• P. malariae - 18 to 40 days

However, incubation periods can vary from as little as 7 days, to several months for P. vivax and P. ovale. If you are taking medication to prevent infection (chemoprophylaxis) the incubation period is usually longer.

It is important that a doctor eliminates other possible diseases or conditions which may have similar symptoms to Malaria. These include:

• Cold, flu, and some other viral infections
• Rickettsia (tick bite diseases)
• Gastroenteritis
• Hepatitis
• Typhoid fever
• Meningitis, and other bacterial infections
• Non-malarial parasitic infections

What are the treatments for Malaria?

According to WHO, in endemic areas treatment should start within 24 hours after the first symptoms appear. A person with uncomplicated malaria can be treated as an outpatient, while those with severe malaria need to be hospitalized. In non-endemic areas WHO recommends that patients with uncomplicated or severe malaria should be kept under clinical observation if possible.

A person who is infected with P. falciparum and has severe symptoms, but cannot take oral medications, should be given treatment intravenously.

In some parts of the world anti-malarial drugs may be presented as suppositories (not USA).

Some drugs used for treating malaria are available as continuous intravenous infusions.

According to the CDC (Centers for Disease Control and Prevention), the following drugs are commonly used for treating malaria:

• artemisin derivatives (not licensed in the USA, common elsewhere)
• atovaquone-proguanil (Malarone)
• chloroquine
• doxycycline
• mefloquine (Lariam)
• quinine
• sulfadoxine-pyrimethamine (Fansidar)

Also, primaquine is effective against hypnozoites (the dormant parasite liver forms) and prevents recurrences (relapses). Primaquine should not be given to expectant mothers, or patients who are deficient in glucose-6-phosphate dehydrogenase G6PD. A screening test excludes G6PD deficiency.

Preventing malaria

The two main ways of preventing malaria are:

• Avoiding mosquito bites - this can be achieved in various ways:


• Vector control - this means trying to reduce contacts between people and vectors of disease. A vector is an organism, such as a mosquito, or tick that carries disease-causing microorganisms from one host to another. Controlling mosquitoes can significantly reduce malaria incidence, as well as other mosquito-borne diseases.
  
  Getting rid of malaria in a region does not necessarily mean eliminating all the Anopheles mosquitoes that might transmit the disease. Anopheles mosquitoes still exist in North America and Europe - however, the parasite is not longer there. Improvements in people's standard of living, such as the installation of screened windows, air conditioning, together with strategies to reduce vector populations are very effective, and have led to the total elimination of malaria without completely getting rid of the mosquito.


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• ITNs (Insecticide-Treated Bed Nets)
  
  ITNs can reduce the incidence of malarial infection, and also mortality, in an endemic area considerably. Untreated nets are significantly less effective because the mosquito can bite the host through the net if the person is standing next to it. Also, even tiny holes in the netting are usually enough for the mosquito to find a way in. Nets that have been treated with insecticide are much more protective. Not only does the insecticide kill the mosquito and other insects, it is also a repellent - fewer mosquitoes are likely to enter the room(s).
  
  If ITNs are widely used in an endemic area the mosquito population may drop dramatically, as will their lifespans. This further protects those in that area who have no ITNs.


• Preventing disease - using anti-malarial medications. These drugs do not prevent the parasite from entering your bloodstream, but they stop it from developing in the blood. This type of prevention is also known as 'suppression'.

Written by - Christian Nordqvist


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