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Malaria


Poster admonishing malaria discipline

National Archives. Via about.com

Malaria is a debilitating and sometimes fatal disease caused by parasitic microorganisms of the genus Plasmodium. The parasite has a complicated life cycle that begins when gametocytes are picked up in a blood meal from an infected human by mosquitoes of the genus Anopheles. The gametocytes mate in the gut of the mosquito, then invade the gut wall to produce an oocyst. This bursts to release sporozoites, which migrate to the mosquito's salivary glands. When the mosquito bites another human, the sporozoites are injected with the mosquito's saliva.

The sporozoites rapidly invade liver cells, where they divide into thousands of merozoites. After one or two weeks, the merozoites break out of the liver cells and invade red blood cells to multiply further. The merozoites periodically break out of the red blood cells to produce the cycles of fever and chills that characterized the disease. Some of the merozoites transform into gametocytes, which can be picked up by another mosquito to complete the life cycle.

The most common strains of malaria encountered in the South Pacific were falciparum and vivax malaria. Falciparum malaria was the more common and severe form the disease. Complications of falciparum malaria include blackwater fever, which is thought to result from a violent reaction of the immune system to the presence of the malaria parasite during treatment with quinine. Large numbers of red blood cells are ruptured and spill their hemoglobin into the bloodstream. This leads to chills, high fever, nausea, jaundice, and severe anemia. The passing of very dark urine is the characteristic symptom of the disease. The mortality rate due to kidney failure is very high. An even more deadly complication of falciparum malaria is cerebral malaria, in which the parasite attempts to evade destruction in the spleen by causing the red blood cells it infects to stick to each other and to capillary walls. These clumps of red blood cells can block circulation in the brain and other organs and lead to severe brain damage and death.

Vivax malaria was less common and severe than falciparum malaria, but it was subject to relapses that can occur long after the initial cycles of fever and chills have subsided. Relapses occurred because a few of the vivax sporozoites transform into a resting form in liver cells, which can lie dormant for years following the initial infection.

Malaria is primarily a disease of warm climates, since the parasite cannot complete its life cycle within the mosquito at temperatures below about 68 degrees Fahrenheit (20 degrees centigrade). It was once common in southern Europe and the southeast United States, where nighttime temperatures are above the threshold much of the year, but public health measures to control mosquito populations had already greatly reduced malaria rates by the time of the Pacific War. The disease would be all but eradicated from the United States by 1947.

Photograph of malaria patients in a makeshift ward on Guadalcanal

U.S. Marine Corps. Via ibiblio.org

Unfortunately, malaria was still endemic in the islands of the South Pacific where much of the fighting of the Pacific War took place, and many Japanese and Allied units suffered appalling casualty rates from the disease. 1 Marine Division at Guadalcanal suffered over 8500 hospitalizations for malaria in the first five months of the campaign. Japanese casualties were likely even worse. It is estimated that 95 percent of the Japanese servicemen deployed to Rabaul suffered at least one bout of malaria, with one in five incapacitated by the disease. One Japanese airman described a bout of malaria (Gamble 2010):

I had a mysterious fever since this morning. Now malaria is really showing itself. It is said that there are 50,000 parasites in a drop of blood. I cannot stand the idea of being ruined by malaria parasites. To what height can people bear fever? Fever seems to affect the brain. I don't feel clear-headed. From 5 to later than 10 0'clock I tossed and turned. I can't describe how hard it is to sleep. I am about to give in to this disease. I feel helpless, as I know that this suffering will continue.

Malaria was treated with drugs such as quinine, which blocks metabolism of the highly toxic heme produced by the digestion of hemoglobin by the parasite. Quinine was also used as a prophylactic, being administered to healthy troops to prevent the infection from taking hold. Almost all the world's supply of quinine came from Java, and with its fall to the Japanese, the Allies were compelled to substitute atabrine, a synthetic quinine analog whose dose rate was still being worked out. Atabrine turned the skin of its users bright yellow, and an overdose could produce nausea, dizziness, or even psychosis. Contrary to rumor, infertility was not one of its side effects.

In addition to prophylactic treatment with quinine and its analogs, malaria could be prevented by keeping the mosquitoes away from the troops. Since many species of Anopheles prefer to feed at night, mosquito bed nets were effective in preventing the disease. This was little help to soldiers in foxholes, however. Destruction of mosquitoes themselves could be accomplished by oiling standing water to suffocate mosquito larvae. More effective was the use of DDT, which was lethal to insects but much less toxic to humans. By mid-1943, amphibious operations in the Southwest Pacific were usually accompanied by dusting flights that dropped tons of DDT over the beachhead and eliminated the disease vector.

Efforts to prevent malaria were slack during the Guadalcanal campaign, where insect repellent was unavailable, Marines who had other concerns "lost" their mosquito netting, and there was no systematic effort to take such elementary precautions as oiling standing water. In at least one theater, officers were threatened with relief for cause if their troops failed to make proper use of Atabrine and mosquito netting (Weina 1998) :

Sir William Slim's method for ensuring command responsibility was to organize surprise checks on units to assess the compliance with Atabrine discipline: "If the overall result was less than ninety-five per cent positive, I sacked the commanding officer. I only had to sack three; by then the rest had got my meaning." With regard to these events, Cantlie stated, "When for the first time in history a combatant officer was considered unfit to command a unit on the grounds that he had allowed his men to become ineffective through disease, a new day in military medicine dawned. The clouds of forgetfulness must not be allowed to overshadow the brightness of that day."

Slim's concern was justified. During the period July-November 1944, when XXXIII Corps suffered just 49 men killed in action, there were over 20,000 cases of malaria.

Japanese forces apparently did not have access to DDT and relied heavily on quinine as a prophylactic. As troops were bypassed and cut off from their sources of supply, they suffered terribly from malaria and other tropical diseases, which often produced many more casualties than enemy action. Japanese troops were equipped with mosquito nets, mosquito repellent, and smoke coils, but mosquito discipline was as poor among the Japanese as it initially was among the Allied troops.

References

Allen (1984)

Bergerud (1996)

Collie and Marutani (2009)

Cowdrey (1994)

Centers for Disease Control and Prevention (accessed 2008-2-4)

Gamble (2010)

Sherman (2011)

Weina, Military Medicine (September 1998; accessed 2008-6-24)



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