Tag Archives: Mosquitos

Mosquitoes’ rapid spread poses threat beyond Zika

LONDON (Reuters) – As the world focuses on Zika’s rapid advance in the Americas, experts warn the virus that originated in Africa is just one of a growing number of continent-jumping diseases carried by mosquitoes threatening swathes of humanity.

The battle against the insects on the streets of Brazil is the latest in an ancient war between humankind and the Culicidae, or mosquito, family which the pests frequently win.

Today, mosquito invaders are turning up with increasing regularity from Washington DC to Strasbourg, challenging the notion that the diseases they carry will remain confined to the tropics, scientists documenting the cases told Reuters.

Ironically, humans have rolled out the red carpet for the invaders by transporting them around the world and providing a trash-strewn urban landscape that suits them to perfection.

The Aedes aegypti species blamed for transmitting Zika breeds in car tyres, tin cans, dog bowls and cemetery flower vases. And its females are great at spreading disease as they take multiple bites to satisfy their hunger for the protein in human blood they need to develop their eggs.

Around the world, disease-carrying mosquitoes are advancing at speed, taking viruses such as dengue and Zika, plus a host of lesser-known ills such as chikungunya and St. Louis encephalitis, into new territories from Europe to the Pacific.

“The concern is that we have these species spreading everywhere. Today the focus is on Zika but they can carry many different viruses and pathogens,” said Anna-Bella Failloux, head of the department that tracks mosquito viruses at France’s Institut Pasteur.

In 2014, there was a large outbreak of chikungunya, which causes fever and joint pains, in the Caribbean, where it had not been seen before, while the same virus sickened Italians in 2007 in a wake-up call for public health officials.

Europe has seen the re-emergence of malaria in Greece for the first time in decades and the appearance of West Nile fever in eastern parts of the continent.

Out in the Atlantic, the Madeira archipelago reported more than 2,000 cases of dengue in 2012, in a sign of the northerly advance of what – at least until Zika – has been the world’s fastest-spreading tropical disease.

In the past 40 years, six new invasive mosquito species have become established in Europe, with five arriving since 1990, driven in large part by the international trade in used vehicle tyres. Mosquitoes lay their eggs in the tyres and they hatch when rain moistens them at their destination.

North American health experts are also racing to keep up, with the first appearance of Aedes japonicus, an invasive mosquito, in western Canada last November and Aedes aegypti found in Washington DC, apparently after spending the winter in sewers or Metro subway stations.

SPREAD UNPRECEDENTED

The speed of change in mosquito-borne diseases since the late 1990s has been unprecedented, according to Jolyon Medlock, a medical entomologist at Public Health England, a government agency.

For many experts, the biggest potential threat is Aedes albopictus, otherwise known as the Asian tiger mosquito, which is expanding its range widely and is capable of spreading more than 25 viruses, including Zika.

“There is strong evidence that Aedes albopictus is now out-competing aegypti in some areas and becoming more dominant,” said Ralph Harbach, an entomologist at London’s Natural History Museum, who has been studying mosquitoes since 1976.

In the United States, Aedes albopictus has been found as far north as Massachusetts and as far west as California. In Europe it has reached Paris and Strasbourg.

Adding to the challenge for public health authorities are the blurred lines between diseases carried by different mosquitoes, as shown by research in Brazil this month that another common mosquito, Culex quinquefasciatus, may also be able to carry Zika.

Both Aedes aegypti and Culex quinquefasciatus probably first arrived in the Americas from Africa on slave ships, scientists believe. In the centuries since, commerce has shuttled other species around the world, while air travel has exposed millions of people to new diseases.

“You’ve got a global movement of mosquitoes and a huge increase in human travel. Humans are moving the pathogens around and the mosquitoes are waiting there to transmit them,” said Medlock.

Human incursions into tropical forests have aggravated the problem. Deforestation in Malaysia, for example, is blamed for a steep rise in human cases of a type of malaria usually found in monkeys.

DON’T KILL THE GOOD GUYS

There have been some victories against mosquitoes, thanks to insecticide-treated bed nets and vaccines against viruses like yellow fever and Japanese encephalitis, as well as a new one for dengue approved in December.

But mosquitoes still kill around 725,000 people a year, mostly due to malaria, or 50 percent more than are killed by other humans, according to the Bill & Melinda Gates Foundation.

Climate change adds a further twist. A 2 to 3 degree Celsius rise in temperature can increase the number of people at risk of malaria by 3 to 5 percent, or more than 100 million, according to the World Health Organization.

Hotter weather also speeds up the mosquito breeding cycle from around two weeks at 25 degrees to 7 to 8 days at 28 degrees, according to the Institut Pasteur’s Failloux.

So is it time to wipe out mosquitoes altogether?

Aggressive action in the 1950s and 1960s, including the use of the pesticide DDT, certainly pushed them back for a while.

Today, genetic modification, radiation and targeted bacteria are being considered.

Trying to eliminate all mosquitoes, however, would make no sense, since there are 3,549 species and fewer than 200 bite humans.

“It might be possible to wipe out a few species but we don’t want to wipe out the good guys because a lot of them serve as food for frogs, fish and bats,” said Harbach. “Many also visit flowers to feed on nectar and may play a role in pollination.”

Some are even our friends. Harbach has a soft spot for the Toxorhynchites genus, which have a convenient penchant for eating Aedes aegypti larvae.

(Editing by Giles Elgood)

CDC issues more travel notices about Zika virus

The Centers for Disease Control and Prevention (CDC) on Friday issued more travel notices about the Zika virus, warning travelers about the potential risks of the mosquito-borne illness.

The notices were issued one week after the CDC advised pregnant women who were planning to travel to 14 countries and territories where outbreaks of the virus were occurring to consider postponing their trips while scientists probe a potential tie between Zika and a rare birth defect.

The notices issued Friday added eight additional countries or territories to the list, bringing the total to 22. The warnings are spread throughout the globe and include places in South America, the Caribbean, Central America, Polynesia and more.

Travelers heading to those areas are asked to “practice enhanced precautions” to prevent mosquito bites, which is how the virus is spread. Pregnant women are advised to rethink their travel plans because of Zika’s potential impact on their unborn children.

Last week, the Hawaii Department of Health announced a child born with microcephaly — a birth defect marked by a smaller-than-usual head — had previously been infected with Zika. The department said his mother likely contracted the virus when she was living in Brazil last May.

The Brazilian Ministry of Health reports that there have been 3,893 cases of microcephaly in the country since the virus arrived in May. The country used to see fewer than 200 cases per year.

Children with microcephaly can develop seizures, vision problems and have developmental delays, the CDC says, but it only occurs in 2 to 12 out of every 10,000 births in the United States.

Scientists are still trying to find a conclusive link between Zika and microcephaly, which can be caused by several other factors. Last week, Dr. Lyle Petersen, the director of CDC’s division of vector-borne diseases, told a news briefing the CDC had “the strongest scientific evidence to date” of a link between Zika and “poor pregnancy outcomes,” though more tests were needed.

Still, the warnings and advice for pregnant women continue. Earlier this week, the CDC issued new guidelines about how healthcare providers in the United States should care for pregnant women who had traveled or were planning to travel to areas where Zika was being transmitted.

Only about 1 in 5 people infected with the virus display any signs of illness, the CDC says, and symptoms are generally mild. They include fever, rash and joint pain, and most people recover within a week. The illness is seldom severe and rarely requires hospitalization.

There haven’t been any reports of people contracting the virus in the United States, the CDC says, though there have been some instances where travelers got bit by infected mosquitos overseas and returned home. The mosquitos that transmit Zika are found in the United States, though Dr. Petersen told the news briefing it’s unclear exactly how or if the virus may spread here.

He told reporters the country has seen improvements in anti-mosquito measures, like using air conditioning and window and door screens, which have helped reduce the spread of other mosquito-borne illnesses, like dengue and malaria, in the past. The CDC encourages all travelers to Zika-prone areas to sleep in screened or air-conditioned rooms, as well as wear long clothing and insect repellant, as there is no vaccine or medicine that can currently prevent an infection.

Countries and territories where the CDC has issued travel notices for Zika include Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname, Venezuela, Barbados, Guadeloupe, Haiti, Martinique, Saint Martin, Samoa, Cape Verde, El Salvador, Guatemala, Honduras, Panama, Mexico and Puerto Rico.

Zika virus confirmed in Texas traveler, health officials say

Health officials in one Texas county say they’ve received word that a traveler who recently visited Latin America contracted the Zika virus, a puzzling mosquito-borne illness that has collected lots of attention because it may be linked to a substantial rise in birth defects in Brazil.

Harris County Public Health & Environmental Services made the announcement Monday, saying the Centers for Disease Control and Prevention (CDC) confirmed the diagnosis.

Harris County encompasses Houston and is one of the country’s largest counties.

According to the CDC, the Zika virus is spread when an infected mosquito bites a person, usually triggering a mild illness that causes people to experience symptoms like fever, rashes and joint pain. Most people recover within a week, and there’s seldom any need for hospitalization.

However, the Brazilian Ministry of Health is currently investigating more than 3,000 cases of microcephaly, a disorder that causes children to be born with abnormally small heads. Brazil only saw 147 cases of microcephaly last year, but the numbers have surged since the Zika virus arrived in May and authorities are still working to see if there’s a direct link between the two.

The CDC has said there hasn’t been any indication Zika has been contracted in the United States, though there have been multiple cases of people getting infected while visiting a foreign country and returning home. Officials didn’t indicate when or where this traveler got infected.

The virus has caused outbreaks in at least 12 countries in North and South America, according to the CDC, as well as many others in Africa and Southeast Asia. In late December, the CDC issued a travel notice for Puerto Rico after the island identified its first locally-acquired Zika infection.

The CDC asks people traveling to Puerto Rico — and other countries where Zika is present — to take proactive steps to safeguard themselves from mosquito bites, like wearing insect repellant and wearing long sleeves and pants. But the organization says the virus will likely continue to reach new territories because the specific kind of mosquitos that spread it live across the globe.

That type of mosquito — the Aedes species — are present in Harris County, according to the county Public Health & Environmental Service’s website. The agency echoed the CDC’s calls for travelers to take preventative steps when they’re traveling to nations where Zika is found.

There’s currently no vaccine against the virus, the CDC says.

Yellow Fever Transmitting Mosquitoes Found In Los Angeles County

The mosquito that transmits yellow fever has been found in two locations in Los Angeles County California.

The aggressive mosquito is known for biting in the daytime and was found October 7th and 8th in Commerce and Pico Rivera.

The species, Aedes aegypti, transmits yellow fever along with others such as dengue fever and chikungunya.

“While these debilitating viruses, so far, aren’t locally transmitted in L.A. County, the mosquitoes that can transmit them are now here,” Susanne Kluh, the district’s director of scientific-technical services, said in a statement quoted by the LA Times. “Infected travelers can bring these viruses to Los Angeles County.”

The yellow fever mosquito thrives in urban environments and usually uses small, man-made containers to lay eggs.

Officials speculate the mosquitoes arrived in California through eggs on imported tires or plants.