Malaria

Malaria is among the most important vector-borne diseases. Over 2.5 billion people are always at risk and there are over 1 million deaths of malaria every year. Malaria is the infection caused by the parasitic protist of the genus Plasmodium and is spread by the mosquito vector. The disease is a result of the multiplication of the parasites within red blood cells leading to fever and headache, eventually progressing to coma or death in severe cases.

Temperature and rainfall are critical factors in determining Malaria patterns. Climate change will increase the opportunities for malaria transmission in traditionally malarious areas, in areas were the disease has been controlled, and in new areas previously unaffected by malaria. Higher temperatures are both lethal and beneficial to Plasmodium and it’s vector. Regions where temperatures are close to the physiological tolerance of the parasite and mosquito can lead to decreased transmission if temperatures rose. However, the increased temperature in temperate regions would increase the risk of transmission to a greater extent because warmer temperatures alter the growth cycle of the parasite and the mosquito, enabling them to develop faster and earlier. Any change in precipitation to either extremes will also increase malaria transmission. Increased rainfall associated with El Nino can flood areas that are usually dry. In dry climates, heavy intermittent rainfall can provide good breeding conditions for mosquitoes. However, the opposite scenario is also true in that drought has been identified as a factor contributing to increased malaria mortality and transmission due to drought-related malnutrition in humans and better breeding conditions, respectively. Drought may turn rivers into strings of pools, which are the preferred breeding grounds for mosquitoes.

            Many tropical countries such as those in South America and Africa experienced malaria epidemics following El Nino years by mechanisms mentioned above in regards to temperature change and precipitation. The relationship between El Nino and the malaria epidemics, is again, statistically significant. Transmission rates up to 40% have even been seen following El Nino associated heavy rainfall and flooding. Climate change increases the epidemic potential of malaria in tropical countries. The increasing temperatures will reintroduce or increase transmission of malaria in tropical and temperate regions that have eliminated or controlled transmission.