(bubbly electronic music)
>>Hello, I am Michael Peercy, an epidemiologist
working with a large Native American tribe in Oklahoma.
Today, I will be discussing changes in the cycles
of infectious, vector-borne disease that may be linked
to changes in the global climate.
Vector-borne diseases are transmitted typically
by the bite of an infected arthropod.
The arthropod could be something very familiar to us
such as a mosquito, tick or fly.
Or it might be a less familiar species
such as an African tsetse fly or a copepod.
These arthropods that carry and transmit disease
are known as vectors.
Other non-arthropod vectors can include rodents
such as rats, certain bats and several species
of wild birds.
Different vectors carry different diseases
such as malaria, dengue, encephalitis,
African sleeping sickness and yellow fever.
Vector-borne diseases are caused by pathogens
such as bacteria or viruses that are often transmitted
by insect vectors such as ticks or mosquitoes.
These diseases are interesting to study because they require
a cycle of pathogen-host interaction
that leads to human infection.
Successful infection requires the presence
of a susceptible host, a competent vector
and virulent pathogens interacting
in an appropriate environment.
The rapid growth of the human population
and the incursion of people into previously rarely
encountered parts of the world have exposed humans
to new and ancient pathogens that historically
have been isolated from mankind.
Vector-borne diseases such as Ebola, hemorrhagic fever,
Rift Valley fever, West Nile encephalitis
and Japanese encephalitis fall into this category.
In addition to increased contact between virulent pathogens
and naive hosts, the climate has a direct impact
on the ability of the vector-borne disease cycle
to result in an outbreak.
And abundance of vectors and hosts directly affects
the rate of disease as does an increase in temperature
or a change in seasonality.
Increased temperature affects the reproductive,
biting and survival rates of vectors
and the pathogens contained within.
Higher temperatures result in longer seasons of activity
for the vectors and an increased spread of disease.
Increased rainfall also has a strong impact on vectors
such as mosquitoes that require an aquatic
reproductive phase.
Increased humidity can also stimulate the activity
of vectors such as the species of ticks that carry
Lyme disease.
According to a study published
by the World Health Organization in 2015,
the global geographic distribution of vector-borne diseases
is changing rapidly due to factors such as climate change,
intensive farming, dams, irrigation, deforestation,
population movement, rapid unplanned urbanization
and increases in international travel and trade.
There is evidence that the geographic range of ticks
and mosquitoes that carry disease has changed in response
to climate change.
While future climate change is expected to continue
to alter the distribution of disease vectors,
it is important to recognize that there are several
other factors such as land use, population density
and human behavior that can also change the distribution
of disease and the extent of infection.
In response to this problem, health and climate researchers
are looking at ways to measure health vulnerability
to climate change and to estimate the potential scale
of the issue.
They are studying health protection strategies
and the health impact of potential adaptation
and mitigation measures.
Research in this field must be matched
with health policy planning, and stronger relationships
must be formed between current health programming
and the modeling of future scenarios
of vector-borne disease.