EU Science Hub
Spurred on by climate change, international travel and international
trade, disease-bearing insects are spreading to ever-wider parts of the
world.
This means that more humans are exposed to viral infections
such as Dengue fever, Chikungunya, Zika, West Nile fever, Yellow fever
and Tick-borne encephalitis.
For many of these diseases, there are as yet no specific antiviral agents or vaccines.
Global
warming has allowed mosquitoes, ticks and other disease-bearing insects
to proliferate, adapt to different seasons, migrate and spread to new
niche areas that have become warmer.
These are the findings of a
JRC report that aims to raise awareness about the threat posed by the
spread of arboviruses (arthropod-borne viruses).
The growing spread of arboviruses
Aedes mosquitoes spread several arboviruses, including Dengue, Chikungunya, Zika, West Nile and Yellow fever viruses.
These
mosquitoes thrive in urban settings due to the lack of natural
predators and the ready availability of food and habitats in which to
procreate.
They have existed in Africa and Asia for many years and are now becoming more and more widespread.
They
have recently become established in some European countries and the
Americas, largely as a result of international travel and trade.
Their
alarming spread poses a problem for public health. They are difficult
to eradicate - their larvae can survive for months, even in suboptimal
humidity and temperature conditions.
The tick-borne encephalitis
virus (TBEV) has been found in several European countries, including
Austria, the Czech Republic, Germany, Lithuania, Poland, Slovakia,
Sweden and, more recently, the Netherlands.
One of the more
recently reported vectors for the virus, the Dermacentor reticulatus
tick species, is rapidly spreading through Europe. It has a high
reproduction rate, is cold resistant and can live underwater for months.
Humans
can be infected by a tick bite or through consuming unpasteurised dairy
products that do not meet EU safety standards and have come from
infected animals. Luckily, TBEV can be vaccinated against.
Zika virus – a serious concern for Europe
Zika
virus has received a lot of media attention due to its association with
neurological disorders such as Guillain-Barré Syndrome (GBS) and the
development of microcephaly (abnormally small head) in foetuses.
It
is difficult to diagnose and there is no cure or vaccine. First
identified in 1947 in the Zika forest of Uganda, its spread is a serious
concern given the growing presence of its main vector, the mosquito
Aedes albopictus, in temperate zones including Europe and America.
The
first documented outbreak of ZIKV infection was reported in 2007 in
Micronesia. Since then it spread to French Polynesia and Brazil, where
it infected up to 1.3 million people in 2015.
More than 70
territories worldwide have confirmed autochthonous (indigenous) cases of
ZIKV. By March 2017, 2 130 Europeans were reported to have
travel-associated ZIKV infections.
Mosquito control strategies
The
report describes and discusses several methods that have been used to
control the spread of mosquitoes, including insecticides, mosquito
traps, genetic modification, land reclamation and habitat surveillance.
Currently,
the safest and most readily available and effective methods of
controlling mosquitoes are mosquito traps (for relatively small areas)
and nets, and the reduction of potential breeding sites (standing
water).
While the research team behind the study advocate better
control of mosquito populations, they also warn that it would be unwise
to remove mosquitoes completely from the ecosystem.
They are part
of the food web for some species, and pollinate many plants. Wiping them
out completely could have negative effects on nature, and consequently
on humans.
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