Monday, July 6, 2009

Spread of Malaria

Undoubtedly, mosquito bites are the most common way that malaria is spread. Specifically, the female anopheles mosquito is most often the culprit of infection. There are approximately sixty varieties of this mosquito.

How mosquitoes spread malaria:
When an infected individual is bitten by a mosquito, the insect ingests the gametocytes (reproductive forms of the parasite) with the blood. These gametocytes continue in the sexual phase of their cycle. Soon sporozoites (cells that infect new hosts) develop and fill the salivary glands of the mosquito. When the mosquito bites the next person, it injects the sporozoites into the human blood stream along with its saliva.

Most mosquito bites occur between 17:00 (5PM) and 07:00.

Other ways malaria is spread:
Mosquito bites are not the only way that malaria is spread. Other common methods of infection include:
1. Blood transfusions
2. Congenital infection
3. Blood-instrument transmission

Infection through Blood Transfusions:
Infection through blood transfusions is a common problem in areas where malaria is rampant. Even when an individual no longer feels sick from malaria, he/she can still transmit the disease via blood transfusion. Infectious periods differ by malaria strain, but for all strains the malaria may remain in the bloodstream for a number of years.
The duration of time malaria remains infectious by strain:
P. falciparum: 1-3 years
P. vivax: 3-4 years
P. malariae: 15+ years (duration may be for life)

Infections through blood transfusions occur when the blood is not stored properly for a long enough period of time. Most infections occur when blood is stored less than five days. It is rare for blood that has been stored over two weeks to transmit the disease. Frozen plasma is not considered infectious.

Blood can be tested for the infectiousness through the indirect fluorescent antibody test or Enzyme-linked immunosorbent assay (ELISA). Visual examination of the blood manually cannot deliver conclusive results.

Another method to reduce the spread of malaria through blood transfusion is to administer chloroquine to the transfusion recipients. Chloroquine is used to prevent malaria from Plasmodium vivax, ovale and malariae.

Congenital Infection:

"80% of deaths due to malaria in Africa occur in pregnant women and children below 5 years. In Africa, perinatal mortality due to malaria is at about 1500/day" (Malaria Site). Physiological changes within the pregnant woman increases the severity of malaria symptoms. Morbidity may be caused by anemia, high fever, pulmonary edema, puerperal sepsis, and hemorrhage.

The infection may be spread from the mother to the child during pregnancy; however this occurs in less than 5% of malaria cases. Congenital malaria is most common in the first pregnancy. Generally, the placenta protects the child from the infection. However, it is possible for transmission to occur prenatally. Babies who contract the disease congenitally are born with symptoms of malaria. Also, infants born to a mother with malaria may be premature, underweight, or stillborn. Malaria and pregnancy are

Blood-instrument transmission:
Instruments that come in contact with blood (including surgical instruments and needles) may transmit the disease. Much like HIV, malaria can be spread through any contact with the blood of an infected individual. Needles (particularly those used in relation to recreational drugs) may transmit malaria if they are shared. At times, malaria was transmitted unintentionally by medical personnel seeking to inoculate against infectious diseases. Medical personal no longer uses the same needles for multiple individuals, so this risk has decreased dramatically. Intravenous drug users can still transmit the disease if needles are shared between individuals.

Note: People have been intentionally infected with malaria (via needles) as a treatment for syphilis because it produced prolonged high-fevers.

Malaria is a disease that can be treated and in some cases prevented. For information how you can help support malaria research and treatment programs, please visit: The Roll Back Malaria Partnership. Infectious bite is not currently accepting money. All donations should be directed through the individual programs.

The Malaria Site. 6 July 2009.
Roll Back Malaria Partnership. 30 June 2009.
World Health Organization: Malaria. 26 June 2009.
Center for Disease Control: Malaria. 26 June 2009.

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