Box 142 Infectious disease pathogens vectors and reservoir host species sensitivity to changes in climatic conditions

• Changes in temperature, rainfall and humidity can affect the range, population density, and biological behaviors of various vector organisms (mosquitoes, ticks, water snails)

• Temperature affects the rate of bacterial proliferation (e.g. food-poisoning species); the proliferation of cholera vibrios increases in response to warmer coastal/estuarine waters, facilitating their subsequent dissemination in the aquatic food web

• The rate of maturation (incubation) of various viruses (e.g. dengue virus) and protozoa (e.g. malaria plasmodium) within mosquito and other vectors is typically very temperature-dependent

Anthony J. McMichael and Rosalie E. Woodruff Host

Climatic variation influences host growth and immunity levels. In arid and semiarid regions (and in temperate regions in severe drought years), the main determinant of host population breeding is the level of food supply. For mammalian vertebrates, rainfall is the dominant factor governing the control of pasture biomass (Noy-Meir, 1973). Kangaroos, for example - the main host for Ross River (see Box 14.3) and Barmah Forest viruses - respond to changes in food supply by adjusting their rates of reproduction (Bayliss, 1987), and come into breeding condition almost immediately following rainfall (Strahan, 1991).

A well-known example of the indirect influence of meteorological factors on a complex infectious transmission cycle is of hantavirus pulmonary syndrome in the southwest USA. The first outbreak in 1993 was subsequently attributed to a

0 0

Post a comment