Climate change promotes the spread of
mosquito and tick-borne viruses
European Commission
Joint Research Centre
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 fetuses.
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.
Reference: CONDUTO
ANTÓNIO Diana Sofia, SANSEVERINO Isabella, POZZOLI Luca, LETTIERI Teresa, 2017.
Toward Climate Change Impact: Vectors carrying viral infection. Publication
Office of the European Union, Luxembourg. ISBN:978-92-79-80856-2, https://doi.org/10.2760/067022