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Essays > Malaria (October 19, 1999 by Pat Heyman)
By midsummer Happy Valley was in complete despair. The malaria had continued to spread but there was no pattern to the epidemic. Not everyone in the same house was infected. Not every house in the same area was touched.
Coolies would not come into Happy Valley until the sun was high in the sky, and they returned to Tai Ping Shan before dark. Struan and Brock and all the traders were at their wits’ end. There was nothing they could do—except move, and moving meant disaster. Staying could mean worse than disaster. And though there were those who insisted it could not be poisoned soil and polluted night air that brought malaria, only those who slept in the valley were afflicted. The God-fearing believed as Culum had believed, that the fever was the will of God, and they redoubled their petitions to the almighty to protect them; the godless shrugged though equally frightened and said, "Joss." The trickle of families back to ships developed into a flood, and Queen’s Town became a ghost town. –Tai-Pan, James Clavell (1966)
- Geographic risk factors
- Malaria follows a very definite geographic pattern, as it is dependent on both the Anopheles mosquito and human hosts to continue its lifecycle. So the number one risk for contracting malaria is living in an area where Anopheles mosquitoes live. The mosquitoes are dependent on stagnant waters to reproduce and they don’t tend to do as well in cold climates and high elevations, so those living in low-lying tropical areas are most at risk for contracting the disease (Garrett, 1994). Women and children are at greatest risk (WHO, 1996).
- Demographic risk factors:
- Malaria tends to be more prominent in poor, rural areas where access to healthcare is less available and mosquito prevention programs are sparse. Stagnant waters abound in dirt roads, basins, under the eaves of roofs, in old tires. Farmers in newly cleared land are particularly at risk for ecological factors.
- Ecological risk factors:
- In an ecosystem with great plant diversity, there is a concurrent diversity of insects. No one species can become dominant. But when farmers clear new land and plant one or two crops, a few insects tend to dominate the ecosystem. Usually these insects are considered pests, and the farmers use insecticides to control them. While short-term success is usually had, the benign insects are harmed far more than the hardier problem insects, which tend to develop insecticidal resistance. The pests are now free from competition and resistant to our chemical weapons. This pattern is particularly true of the Anopheles, in which there is resistance to multiple insecticides (Garrett, 1994)
- Behavioral factors:
- Anopheles mosquitoes are not active during the daylight hours, but only at dusk, dawn, and night. Those who enjoy outdoor activities at night are more prone to being bitten by the Anopheles mosquitoes. The use or nonuse of bed nets and local insecticides also influence one’s risk of contracting malaria (WHO, 1999).
Etiology
Pathogenesis
Morphology
Clinical Manifestations