Climate Change and the European Water Dimension - Agri ...

(cholera). Mosquito borne diseases are more influenced by ambient conditions than
diseases transmitted directly from human to human. In fact, climate changes:
• influence distribution and growth rate of vectors,
• alter the geographic distribution of pests
• temperature plays a determinant role in vector development, cutting the time
necessary to develop from egg to adult and fastening the generation turn over
(Kiska, 2000).
However, temperature affects also pathogen development within the vector (Bouma
et al., 1994): incubation period decreases and disease reproduces faster inside the
pest carrier.
VI.E. Vector-Borne Diseases
Mosquitoes are among the first organisms to extend their range as climate change
make new areas more accessible (Lindsay, 1996). The transmission of infectious
diseases may rise as temperature grows warmer and insects migrate northward. As
a consequence, diseases that are typically restricted to tropical and subtropical
regions could become more common in northward areas. In North America, malaria
and dengue fever are already among the new arrivals; Lyme disease already affects
northern US regions (http://www.ccah.cpha.ca). Malaria has already appeared in
Canada: during hot, humid period in 1990, locally transmitted malaria occurred in
Toronto as well as in the northeastern (New York, New Jersey) and north central
(Michigan) United States. It is estimated that 300-500 million people suffer from
malaria every year (WHO, 1993), while over 2 billion people are considered at risk
from contracting disease (Epstein, 2000) with a predicted 3°C rise in global
temperature, an additional 50-80 million cases of malaria will occur each year.
Since 1970 the height at which freezing occurs (the freezing isotherm) has climbed
approximately 160m within the tropical belts, equivalent to almost 1°C warming (Diaz
and Graham 1996). Insects and insect borne diseases are now being reported at
high elevation in east and central Africa, Latin America and Asia. Malaria is
nowadays detected in highland urban centers like Nairobi, and rural highlands in
Papua New Guinea (Epstein et al., 1998).
Dengue fever is a tropical disease caused by Arbovirus and transmitted by the bite of
an infected mosquito (genus Aedes). There is no vaccine and the disease becomes
increasingly fatal with successive infections. (Breslin, 1994). Outbreaks have so far
been restricted to Central America but warming trends due to climate change would
increase the range and frequency of dengue fever in North America. However
concern arises because, although specific vector are involved in transmission of
malaria and dengue fever, even local mosquitoes can become potential vectors and
the cost of mosquito eradication would dramatically increase to control the spread of
disease.
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