CIESIN Reproduced, with permission, from: Freier, J. E., D. J. Rogers, M. J. Packer, N. Nicholls, and J. Almendares. 1993. Vector-borne diseases. In Global health watch: Monitoring impacts of environmental change, by A. Haines, P. R. Epstein, and A. J. McMichael. Lancet 342: 1464-69.

Global health watch: monitoring impacts of environmental change

Andrew Haines, Paul R Epstein, Anthony J McMichael, on behalf of an international panel*

Vector-borne diseases

(Freier, Rogers and Packer, Nicholls, Nov 20; Almendares and others, Dec 4)

The WHO task group identified several vector-borne diseases that might be influenced by climate change. Examples are malaria, lymphatic filariasis, African trypanosomiasis, dengue and yellowfever.[6]

Changes in terrestrial ecosystems---detected for instance, by satellite imaging---can help monitor vector-borne diseases. In particular, vegetation indices produced by high-resolution radiometry have been correlated with mortality rates and population density of tsetse flies. Several types of remote sensing can be used to indicate animal and vector habitats; the LANDSAT and SPOT satellites (figure 1) have resolutions of 30 m and 10 m, respectively, and have been used to identify habitats of ticks and mosquitoes. The US National Aeronautics and Space Administration is sponsoring research on the use of satellite information for vector-borne disease monitoring and control.[7] Improved surveillance systems should be incorporated within the next generation of earth observation platforms. Integrated systems combining meteorological, topographic, and epidemiological data must become more accessible and simpler to use.

Climate change may first have impact on vector-borne diseases at the margins of their current distributions. In global warming isotherms shift polewards and vectorborne disease may follow in the same direction 10[[ring]]C for yellowfever,[8] 16deg.C for vivax malaria, 20[[ring]]C for falciparum malaria). Climate change might also affect the altitude at which vector-borne diseases are found, and high altitude sites in Kenya, Rwanda, Costa Rica, and Argentina may be good sites for monitoring. Field studies have been done but they must be kept going indefinitely. Low cost continuous monitoring may be possible through local primary care facilities with health staff trained to diagnose malaria and other conditions reliably and to keep accurate records.

In Latin America, Chagas' disease could be monitored in Chile and Argentina, currently at the edges of the endemic area. Schistosomiasis could also be susceptible to climate change, especially if irrigation patterns change. In the USA there is a possibility of the spread of five vector-borne diseases---malaria, yellowfever, Rift Valley fever, dengue fever, and arbovirus-induced encephalitides.[9] The use of the Southern Oscillation Index, based on differences in atmospheric pressure, to predict outbreaks of Australian encephalitis was discussed by Nicholls.

Climate change may result in the elimination of some vectors and/or pathogens---for instance, as a result of very hot dry conditions, as in Honduras (Almendares et al). Local influences, such as deforestation, need to be distinguished from climate change.


6 WHO Task Group. Potential health effects of climate change. Geneva: WHO, 1990: 58.

7 Epstein PR, Rogers DJ, Sloff R. Satellite imaging and vector-borne disease. Lancet 1993; 341: 1404-06.

8 Maurice J. Fever in the urban jungle. New Sci Oct 16, 1993: 25.

9 Longstreth JA. Human health. In: Smith JB, Tirpak D, eds. The potential effects of global climate change on the United States. Washington, DC: Environmental Protection Agency, 1989.