Malaria

Question 1

Cause

Answer 1

• Malaria is caused by the infection by a species of Plasmodium parasite (protist): Plasmodium falciparum.
• The parasite is transmitted to humans most commonly through mosquito bites.

Question 2

Distribution

Answer 2

Typically found in areas with
* Warmer temperatures
* Close to the equator
* Lower altitudes
* Tropical and subtropical
* Plenty of rainfall
* High humidity
* Temperatures below 20°C Plasmodium falciparum (which causes severe malaria) cannot complete its growth cycle in the Anopheles mosquito, and thus cannot be transmitted.

Even within tropical and subtropical areas, transmission will not occur:
* At very high altitudes;
* During colder seasons in some areas;
* In deserts (excluding the oases); and
* In some countries where transmission has been interrupted through successful control/elimination programs.

• Generally, in warmer regions closer to the equator
• Transmission will be more intense, and
• Malaria is transmitted year-round.
• The highest transmission is found in Africa South of the Sahara and parts of Oceania such as Papua New Guinea.
• In cooler regions, transmission will be less intense and more seasonal. There, P. vivax might be more prevalent because it is more tolerant of lower ambient temperatures.

Question 3

Transmission

Answer 3

• Transmission via a vector: infected female Anopheles mosquito.
• The mosquito bites an infected person, and takes their blood containing the protist, the protist reproduces inside the mosquito, and is transmitted to the next host via saliva.
• Infected mosquito then bites a noninfected person. The malaria parasites enter that person’s bloodstream and travel to the liver.
• When the parasites mature, they leave the liver and infect red blood cells.
• Once malaria has entered the red blood cells, it multiplies within the cells which then burst after a few days.
• This releases the parasite into the blood which spreads more infection to other red blood cells, causing more symptoms to be present and/or the symptoms to be more intense.
• In the liver: where some types can lie dormant for as long as a year.
• if you are infected an uninfected mosquito may bite you and the cycle continues

Other modes of transmission:
* Because the parasites that cause malaria affect red blood cells, people can also catch malaria from exposure to infected blood, including:
* From mother to unborn child
* Through blood transfusions
* By sharing needles used to inject drugs

Question 4

Cycle

Answer 4

• The life cycle is complex, requiring a human host and a mosquito vector.
  In the mosquito:
• The pathogen grows, reproduces sexually, and increases in number, but is not a mature parasite yet
  In the human:
• The pathogen reproduces asexually in the liver and sexually in red blood cells before maturing into the plasmodium parasite.

Question 5

Impact on host

Answer 5

Signs and symptoms of malaria may include:
* Slow-rising fever that escalates to rapid temperature fluctuation
* Chills
* General feeling of discomfort
* Headache
* Nausea and vomiting
* Diarrhea
* Abdominal pain
* Muscle or joint pain
* Fatigue
* Rapid breathing
* Rapid heart rate
* Cough
* Shivering
* Excessive sweating
* Severe anemia

• Some people who have malaria experience cycles of malaria “attacks.” An attack usually starts with shivering and chills, followed by a high fever, followed by sweating, and a return to normal temperature.
• Malaria signs and symptoms typically begin within a few weeks after being bitten by an infected mosquito. However, some types of malaria parasites can lie dormant in your body for up to a year.
• People at increased risk of serious disease include:
• Young children and infants
• Older adults
• Travelers coming from areas with no malaria
• Pregnant women and their unborn children
• Malaria can be fatal, especially when caused by the plasmodium species common in Africa.
• The World Health Organization estimates that about 94% of all malaria deaths occur in Africa — most commonly in children under the age of 5.

Malaria deaths are usually related to one or more serious complications, including:
* Cerebral malaria: If parasite-filled blood cells block small blood vessels to your brain (cerebral malaria), swelling of your brain or brain damage may occur. Cerebral malaria may cause seizures and coma.
* Breathing problems: Accumulated fluid in your lungs (pulmonary edema) can make it difficult to breathe.
* Organ failure: Malaria can damage the kidneys or liver or cause the spleen to rupture. Any of these conditions can be life-threatening.
* Anemia: Malaria may result in not having enough red blood cells for an adequate supply of oxygen to your body’s tissues (anemia).
* Low blood sugar: Severe forms of malaria can cause low blood sugar (hypoglycemia), as can quinine — a common medication used to combat malaria. Very low blood sugar can result in coma or death.

Question 6

Treatment

Answer 6

• Use anti-malarial drugs.
• These work by killing the parasites during their development stage in the liver and red blood cells.
• Interfere with the digestion of hemoglobin in the blood stages of the malaria life cycle.

Question 7

Prevention/control

Answer 7

• Use of insecticides to kill mosquitoes.
• Eliminate stagnant water or put oil on water to disrupt mosquito breeding.
• Avoid being outdoors at times when mosquitoes are active, use netting or repellent or wear protective clothes to avoid being bitten (stops transmission)
• Biological control of mosquitoes, such as mosquito fish
• Anti-malaria drugs result in fewer infected people - can be taken as a preventative drug if you are traveling to a location where malaria is common.
• Malarial vaccine