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Climate Change Raises Mosquito-Borne Disease Risk

Students who are beneficiaries of the activities financed by UNICEF and developed together with their humanitarian partners. This photograph was taken as part of the coverage of recreational days for the prevention of Zika, during the development of the theater play "La Zancuda Patirrayas and the Zika Virus." Manta, Manabí, Ecuador. March 2, 2017. (Photo by UNICEF) Creative Commons License va Flickr

Students who are beneficiaries of the activities financed by UNICEF and developed together with their humanitarian partners. This photograph was taken as part of the coverage of recreational days for the prevention of Zika, during the development of the theater play “La Zancuda Patirrayas and the Zika Virus.” Manta, Manabí, Ecuador. March 2, 2017. (Photo by UNICEF) Creative Commons License va Flickr

By Sunny Lewis

BATH, Somerset, United Kingdom, November 5, 2018 (Maximpact.com News) – Present-day climate change could result in the spread of deadly mosquito-borne diseases to new places or their return to areas where they have already been eradicated, scientists are warning, based on the largest-ever study of the mosquito evolutionary tree, going back 195 million years.

These diseases – such as malaria, Yellow fever, Zika virus, and Dengue fever – cause millions of deaths each year.

While many of these diseases have been eradicated from Europe and are under control in other parts of the world, resurgence is possible.

New research from British and Chinese scientists at the Milner Centre for Evolution at the University of Bath, University of York  and China Agricultural University, shows that the rate at which new species of mosquitos evolve increases when levels of atmospheric carbon dioxide are higher.

Carbon dioxide levels today are higher than at any point in at least the past 800,000 years, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).

The global average atmospheric carbon dioxide in 2017 was 405 parts per million (ppm), with a range of uncertainty of plus or minus 0.1 ppm.

The scientists say this is concerning because the greater the number of mosquito species, the more potential exists for new ways of vectoring diseases, and perhaps for new variants of those diseases.

Professor Matthew Wills, from the University of Bath’s Milner Centre for Evolution, said, “It’s only the female mosquitos that take a blood meal, and they use the CO2 that mammals and other vertebrates exhale as a very general cue to locate their hosts.”

“One line of thinking is that as ambient levels of atmospheric CO2 rose, as they have done in recent decades, mosquitos may have found it increasingly difficult to distinguish between the CO2 from their hosts and those background levels,” Wills speculated.

“Vision, body heat and other smells might then have become more important in locating their blood meals, but many of these cues tend to be more specific to particular hosts,” said Wills. “As a general rule, we know that strong host specificity can be an important driver of speciation within parasites, and the same may be true in mosquitos.”

The Bath, York and China Agricultural research found that while there is a link between rising carbon dioxide (CO2) levels and mosquito diversification, the association is more complicated than previously thought. Other factors – such as the diversity of mammalian hosts – contribute to an increase in the species richness of mosquitos.

Dr. Katie Davis, from the University of York’s Department of Biology, said, “We found that the increase in the diversity of mammals led directly to a rise in the number of mosquito species, and also that there is a relationship between CO2 levels and the number of mammal species.”

“But there are still missing pieces of this puzzle, so we can still only speculate at this stage,” she said.

“It is important to look at the evolution of the mosquito against climate change because mosquitos are responsive to CO2 levels. Atmospheric CO2 levels are currently rising due to changes in the environment that are connected to human activity, so what does this mean for the mosquito and human health?

“Despite some uncertainties, we can now show that mosquito species are able to evolve and adapt to climate change in high numbers. With increased speciation, however, comes the added risk of disease increase and the return of certain diseases in countries that had eradicated them or never experienced them before.”

Chufei Tang, formerly at the Milner Centre for Evolution and now at the China Agricultural University, said, “The rising atmospheric CO2 has been proven to influence various kinds of organisms, but this is the first time such impact has been found on insects. This research provides yet another reason for people to participate in low-carbon lifestyles.”

More research is needed to understand what climate change means for the future of the mosquito, and this research is expected to contribute to further discussions about the value of mosquitos to the ecosystem and how to manage the diseases they carry.

The study, Tang et al (2018) “Elevated atmospheric CO2 promoted speciation in mosquitoes (Diptera, Culicidae)” is published in the journal “Communications Biology,” DOI: 10.1038/s42003-018-0191-7.

Featured Image: Mosquitos, Eldorado, Misiones Province, Argentina, 2012 (Photo by Oscar Fava) Public domain


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Zika Virus ‘Spreading Explosively’ Across the Americas

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Microcephaly is a birth defect where a baby’s head is smaller than expected when compared to babies of the same sex and age. Babies with microcephaly often have smaller brains that might not have developed properly. (Drawings courtesy Centers for Disease Control and Prevention) Public domain.

By Sunny Lewis

GENEVA, Switzerland, February 2, 2016 (Maximpact.com News) – The head of the World Health Organization Monday declared the spread of the Zika virus to 24 countries in the Americas “a public health emergency of international concern.”

Zika is a mosquito-borne virus that is new to the Americas. Since Brazil reported the first cases of local transmission of the virus in May 2015, it has spread within Brazil and to 23 other countries and territories in the region.

The World Health Organization (WHO) estimates that four million people could be affected by the Zika virus over the next 12 months.

Arrival of the virus in Brazil its spread across the Americas has been associated with a steep increase in the birth of babies with abnormally small heads and incomplete brain development, a condition called microcephaly.

The Brazilian government has confirmed that the Zika virus infection in pregnant women can cause microcephaly in the fetus, but not every pregnant woman who is infected will have the baby with a small head.

Also associated with Zika infection is an increase in cases of Guillain-Barré syndrome, a poorly understood condition in which the immune system attacks the nervous system, sometimes resulting in paralysis.

“A causal relationship between Zika virus infection and birth defects and neurological syndromes has not been established, but is strongly suspected,” says the WHO.

WHO Director-General Dr. Margaret Chan Monday convened an Emergency Committee meeting of 18 experts and advisers via teleconference to gather advice on the severity of the health threat associated with the continuing spread of Zika virus disease in Latin America and the Caribbean.

Acting on the advice of the Emergency Committee, Dr. Chan Monday declared that the recent cluster of microcephaly cases and other neurological disorders reported in Brazil, following a similar cluster in French Polynesia in 2014, constitutes “a Public Health Emergency of International Concern.”

No vaccines exist to prevent infection with the virus. It is spread by the Aedes aegypti mosquito, which also spreads dengue fever. There are no specific treatments or rapid diagnostic tests for Zika.

Dr. Chan said WHO will prioritize the development of vaccines and new tools to control mosquito populations, as well as improving diagnostic tests.

“A coordinated international response is needed to improve surveillance, the detection of infections, congenital malformations, and neurological complications, to intensify the control of mosquito populations, and to expedite the development of diagnostic tests and vaccines to protect people at risk, especially during pregnancy,” she said.

At present, the most important protective measures are the control of mosquito populations and the prevention of mosquito bites in at-risk individuals, especially pregnant women.

“The Zika virus was first isolated in 1947 from a monkey in the Zika forest of Uganda. Its historical home has been in a narrow equatorial belt stretching across Africa and into equatorial Asia,” Dr. Chan told the WHO Executive Board in a January 28 briefing.

“For decades, the disease, transmitted by the Aedes genus of mosquito, slumbered, affecting mainly monkeys. In humans, Zika occasionally caused a mild disease of low concern,” Chan explained.

In 2007, Zika expanded its geographical range to cause the first documented outbreak in the Pacific islands, in the Federated States of Micronesia. From 2013-2014, four additional Pacific island nations documented large Zika outbreaks.

“The situation today is dramatically different,” said Dr. Chan. “Last year, the virus was detected in the Americas, where it is now spreading explosively. As of today, cases have been reported in 23 countries and territories in the region. The level of alarm is extremely high.”

WHO is “deeply concerned” about this rapidly evolving situation, in part because conditions associated with this year’s El Nino weather pattern are expected to greatly increase mosquito populations in many areas.

PAHO anticipates that Zika virus will continue to spread and will likely reach all countries and territories of the region where Aedes mosquitoes are found.

Yet, the Emergency Committee found no public health justification for restrictions on travel or trade to prevent the spread of the Zika virus.

Only about one in five people infected with the Zika virus will feel sick. In those that do, symptoms are usually mild and can include fever, rash, joint pain and red eye.

The role of Aedes mosquitoes in transmitting Zika is documented and well understood, while evidence about other transmission routes is limited, says the Pan American Health Organization (PAHO), the regional office of the World Health Organization for the Americas.

Zika has been isolated in human semen, and one case of possible person-to-person sexual transmission has been described. However, says PAHO, more evidence is needed to confirm whether sexual contact is a means of Zika transmission.

Zika can be transmitted through blood, but this is an infrequent mechanism. Standard precautions that are already in place for ensuring safe blood donations and transfusions should be followed, PAHO advises.

Evidence on mother-to-child transmission of Zika during pregnancy or childbirth is also limited. Research is currently under way to generate more evidence regarding perinatal transmission and to better understand how the virus affects babies.

There is currently no evidence that Zika can be transmitted to babies through breast milk.

In the coming weeks, the World Health Organization will convene experts to address critical gaps in scientific knowledge about the virus and its potential effects on fetuses, children and adults.

In Brazil the number of Zika infections is estimated to top 1.3 million cases, according to the medical journal “The Lancet.”

President Dilma Rousseff will broadcast a plea to all Brazilians to wipe out the Aedes mosquito in a video recorded Monday for broadcast nationwide on Wednesday.

Brazilian government officials are even considering cancelling this summer’s Olympic Games, just seven months away.

Presidential Chief of Staff Jacques Wagner said Monday that “there is the possibility of cancellation of the Olympics in August because of the seriousness of the problem.”

In the United States, President Barack Obama is taking steps to warn the American people and help them to protect themselves.

The U.S. mainland does have Aedes species mosquitoes that can become infected with and spread Zika virus. U.S. travelers who visit a country where Zika is found could become infected if bitten by a mosquito.

In a meeting with Director of the Centers for Disease Control and Prevention, Dr. Thomas Frieden, and other health and national security advisors, Obama emphasized the need to accelerate research efforts on diagnostic tests, to develop vaccines and therapeutics, and to ensure that all Americans have information about the Zika virus and steps they can take to better protect themselves.

SIDEBAR

Mosquito populations should be reduced and controlled by eliminating breeding sites, authorities advise. Containers that can hold even small amounts of water where mosquitoes can breed, such as buckets, flower pots or tires, should be emptied, cleaned or covered to prevent mosquitoes from breeding in them. Larvicide can be used to treat standing waters.

All people living in or visiting areas with Aedes mosquitoes should protect themselves from mosquito bites by using insect repellent; wearing clothes that cover as much of the body as possible; using physical barriers such as screens, closed doors and windows; and sleeping under mosquito nets, especially during the day when Aedes mosquitoes are most active.


Award-winning journalist Sunny Lewis is founding editor in chief of the Environment News Service (ENS), the original daily wire service of the environment, publishing since 1990.

Featured image:  The Aedes aegypti mosquito spreads Zika and dengue fever, among other illnesses. (Photo by James Gathany) Public domain.