[Mosquito Control] What Does Climate Change Mean for Pests and PMPs?
Supplement - Mosquito Control
Populations of vectors will increase in response to extended
seasons suitable for development and less severe winters. Epidemics of
insect-borne diseases such as West Nile virus and dengue also could
become more common in response to an increase in the frequency of
extreme climatic events.
Global
climate change (a.k.a., global warming) has been the subject of
considerable debate for the past several years. Who to believe?
“The whole (global warming) thing is created to destroy America’s free enterprise system and our economic stability.” —
Jerry Falwell
“I’d say the chances are about 50-50 that humanity will be extinct or
nearly extinct within 50 years. Weapons of mass destruction, disease, I
mean this global warming is scaring the living daylights out of me.” —
Ted Turner
“If you asked me to name the three scariest threats facing the human
race, I would give the same answer that most people would: nuclear war,
global warming and Windows.” —
Dave Barry
Despite early skepticism about the phenomenon of global climate change,
it is now widely accepted by the scientific community, governments and
most people. The main questions, going forward, are the speed at which
change will occur and the specific environmental consequences. Climate
change in the temperate zone of the United States will likely have three
major components:
- Milder winters
- Longer growth seasons
- Increased frequency of weather extremes (e.g., tornados, droughts, floods, heat and cold)
What does this mean for PMPs? Should they revise their businesses in
anticipation of new conditions and new pests? The real answer is “it
depends.” You can expect some of the following:
- Pests will become active earlier in the year and there will be more pest insect/spider generations per season.
- Population sizes of pests will tend to increase, particularly later in a season.
- Occasional invaders and other pests will enter homes more often.
Large pest populations alone can be responsible, but drought conditions
and extreme temperatures can drive pests, seeking moisture, food and
cooler temperatures, into homes.
- Range expansion (generally to the north) of existing native and exotic nuisance pests.
- The number and frequency of invasive species will increase.
- Medically important arthropods will become more important as their ranges and populations increase.
Two recent examples, from the St. Louis area, illustrate
weather-influenced effects on pests. In 2012, termites swarmed unusually
early (February) following the extremely mild winter of 2011-12. The
mild winter was followed by a very warm and dry summer and this was
associated with a significant increase in houses invaded by brown
recluse spiders that normally reside outdoors.
The fossil record supports rapid insect movement northward in
response to warming climate. Fossils from the end of the last ice age
demonstrate that rapid, poleward shifts of insects accompanied overall
warming, including warmer winters. In addition to the direct impacts of
warming on insects, volatile weather and warming can disrupt the
relationships among species that help to prevent the spread of
‘‘nuisance’’ species. This is a topic that is difficult to study and
remains poorly documented.
Range expansions and population increases of medically important
species will likely be the most significant consequence of climate
change. For example, within the next 75 years it is estimated that the
range of the red imported fire ant in the United States could expand
northward by more than 80 miles and expand in total area by 21 percent
as warmer winters make new areas suitable for their survival.
Similarly, the Africanized bee, which entered California and the
desert southwest in the early 1990s, has continued to spread northward
and its northern limits will be influenced by warmer winter
temperatures.
What About Mosquitoes? The more serious issue is,
perhaps, that climate warming, urbanization and vegetation changes will
affect global patterns of vector-borne (primarily mosquitoes and ticks)
diseases. This will occur as the geographical distribution of vectors
expands. Populations of vectors will increase in response to extended
seasons suitable for development and less severe winters. Epidemics of
insect-borne diseases such as West Nile virus and dengue also could
become more common in response to an increase in the frequency of
extreme climatic events. Infections involving two or more species —
mosquitoes, ticks, deer, birds, rodents and humans — re?ect changing
ecological and climatic conditions as well as social changes (e.g.,
suburban sprawl).
Diseases carried by mosquito vectors are particularly sensitive to
meteorological conditions. Excessive heat kills mosquitoes. However,
within their survivable range, warmer temperatures increase their
reproduction and biting activity, and the rate at which pathogens mature
within them.
Temperature thresholds limit the geographic range of mosquitoes.
Yellow fever and dengue fever are both carried by Aedes aegypti, which
is restricted by the 10°C (50°F) winter isotherm. Freezing kills Aedes
eggs, larvae and adults. Thus, expanding tropical conditions can
increase the ranges and extend the season with conditions allowing
disease transmission. Warm nights and warm winters favor insect
survival.
In the United States, warm winters have been demonstrated to
facilitate overwintering and thus northern migration of the ticks that
carry tick-borne encephalitis and Lyme disease. Mild winters are
expected to allow a greater than 60 percent range increase of deer ticks
in the United States by the end of this century.
Malaria is the bane of mankind. Today, half of the world’s population
is exposed to malaria on a daily basis. Deforestation, drug resistance
and inadequate public health measures all have contributed to the recent
resurgence. Could malaria once again become a problem in the United
States?
Since 1976, several vector-borne diseases have reappeared in
temperate regions. Anopheline mosquitoes long have been present in North
America and malaria circulated in the United States in the early 20th
century. However, by the 1980s, transmission was limited to California
after mosquito control programs were instituted. Since 1990, small
outbreaks of locally transmitted malaria have occurred during hot spells
in Texas, Georgia, Florida, Michigan, New Jersey, New York and Toronto.
Malaria has returned to South Korea, areas of southern Europe and the
former Soviet Union. Malaria has recolonized the Indian Ocean coastal
province of South Africa, and dengue fever has spread southward into
northern Australia and Argentina.
These changes are consistent with climate projections, although land
clearing, population movements, and drug and pesticide resistance for
malaria control all have played parts. Warm weather facilitates malarial
transmission. At 20°C (68°F), falciparum malarial protozoa take 26 days
to incubate, but at 25°C (77°F) they develop in 13 days. Anopheline
mosquitoes, which are carriers of malaria, live only several weeks.
Thus, warmer temperatures permit parasites to mature in time for the
mosquito to transfer the infection.
Final Thoughts. Warming
encourages the spread of infectious diseases, but extreme weather
events also can have major impacts on public health. Large-scale weather
patterns have shifted. The warming of Eurasia, for example, has
intensi?ed the monsoons that are strongly associated with mosquito and
water-borne diseases in India and Bangladesh. The U.S. southwest
monsoons also may have shifted, with implications for disease patterns
there as well. Extremes can be hazardous for health. Prolonged droughts
fuel ?res, releasing respiratory pollutants. Floods foster fungi, such
as the house mold Stachybotrys atra, which may be associated with a
hemorrhagic lung disease. Floods greatly increase mosquito-breeding
sites and also pollute waterways.
Continued global warming and icecap melting will result in
significant rises in sea level. This, in turn, will lead to coastal
flooding and increased breeding habitat for brackish water mosquitoes
such as Ochlerotatus taeniorhynchus, Aedes squamiger and Aedes
sollicitans. In the future, nuisance biting mosquitoes are likely to
become a much greater problem in urban coastal areas.
Whatever its cause, global climate change is occurring and bringing
with it new pests, diseases and opportunities for PMPs. Read your
professional literature and stay informed!
Source: http://www.pctonline.com/pct0413-mosquitoes-increase-climate-change.aspx
you with no more gutters to clean and no more ladders to climb.
