Climatic influences on pathogen vector host

All infectious organisms (bacteria, viruses, protozoa, helminths, and others) are thought likely to be affected by some aspect(s) of climatic conditions. The most affected stages of the pathogen's lifecycle are the free-living, intermediate, or within-vector stages - that is, the stages spent outside either the human host or the intermediate (reservoir) host. Many studies have documented how climatic variations influence the occurrence of a wide range of infectious diseases. Some of these studies have depended on field observations of natural variations; other have tested specific relationships in laboratory-experimental fashion - such as the relationship between temperature and malarial parasite maturation within the vector mosquito.

The following section describes the biology underpinning the climate and infectious disease relationship, and refers to epidemiological studies that have recognized or tested this.

Direct transmission

HUMANS

Anthroponoses (human-to-human)

HUMANS

e.g. hepatitis

Indirect transmission

VECTOR

HUMANS VECTOR

HUMANS

e.g. dengue

ANIMALS

Zoonoses

(animal-to-human) ANIMALS

ANIMALS VECTOR /ECTOR ANIMALS

VECTOR

e.g. rabies e.g. West Nile HUMANS

HUMANS

e.g. West Nile HUMANS

Figure 14.1 Main types of transmission cycles for infectious agents. Based on Wilson (2001).

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