Mowing dry detention basins makes mosquito problems worse

University of Illinois News Bureau: A study of the West Nile virus risk associated with “dry” water-detention basins in Central Illinois took an unexpected turn when land managers started mowing the basins. The mowing of wetland plants in basins that failed to drain properly led to a boom in populations of Culex pipiens mosquitoes, which can carry and transmit the deadly virus, researchers report.

...The team, led by University of Illinois postdoctoral researcher Andrew Mackay, found that mowing down cattails and phragmites, two invasive plants that tend to permeate stormwater basins, adds a lot of plant debris to the water.

“We suspect bacteria quickly colonize the waterborne debris, and mosquito larvae feed on the bacteria,” said Illinois entomology professor Brian Allan, a co-author on the study with Mackay, Illinois Natural History Survey entomologist Ephantus Muturi and U. of I. natural resources and environmental sciences professor Michael Ward.

“After aquatic plants were mowed in the basins, we saw a large increase in the number of Culex pipiens mosquito larvae in the basins, which had relatively few before mowing,” Mackay said. “And perhaps more importantly, we caught about twice as many adult Culex mosquitoes in traps at basins after these plants were mowed, compared with basins where the aquatic vegetation was left intact.”

Mowing phragmites, a tall and sturdy invasive grass, also dispersed a host of bird species that liked to roost in the grass, Allan said.  “We had observed that these phragmites-invaded basins would become colonized by large communa
l roosts of birds,” he said. “And we thought that was important because birds are the natural reservoir hosts of West Nile Virus.” The researchers suspected that a bird roost near a mosquito nursery might increase the West Nile virus risk to people living nearby.

“Instead, we found that the presence of a communal bird roost actually decreased West Nile virus risk,” Allan said. “That may be because these wetland roosts include a variety of bird species, many of which are not good reservoirs of the virus. They don’t amplify the virus like other bird species more associated with residential areas do – the American robin, for example....

Rather than decreasing risk, mowing wetland plants in dry detention basins can exacerbate a mosquito problem, researchers found. Photo by Andrew Mackay

UNICEF distributes half a million mosquito nets amid heavy rains and violence in CAR

A press release from UNICEF: Amid heavy rains and violence UNICEF and partners have distributed more than half a million mosquito bed nets reaching every home in Bangui to protect families from malaria - the leading killer of children under 5 in Central African Republic.

With the current heavy rains the risk of malaria significantly increases. To ensure children are protected UNICEF and the National Red Cross with support from the Ministry of Health mobilized more than 7,000 volunteers who went door-to-door distributing more than 530,000 mosquito nets in a single month.

“Rains are pouring down every day here", says UNICEF CAR Representative Souleymane Diabaté. “Courageous volunteers have been working every day in a volatile environment to provide families the protection they need from this deadly disease.”

Every year nearly 460,000 people in Central African Republic suffer from malaria, and there has been an increase in the number of malaria deaths since 2010. In the north-west of the country, malaria accounted for 70 percent of all child deaths from May to July last year. When used correctly, bed nets can reduce malaria by half and can reduce all causes of child mortality on average by 20 percent....

Genetically modified mosquitoes set to be released in Brazil to combat dengue

Justine Alford at IFL Science: ... Mosquitoes kill more people each year than all other animals combined, and on average they kill even more people than humans do. It is estimated that over 1 million people die per year from mosquito-borne diseases, such as Malaria and Dengue Fever, and millions more endure pain and suffering.

Tackling this problem has proved a formidable task in the past, but a very small UK-based company called Oxitec have been developing and implementing an exciting and cost effective technique that could help curb vector-borne diseases in problem areas without the negative environmental impacts that other approaches often bestow. This sustainable technique, which involves the release of “sterile” insects into the wild, has already proved a success story in several dengue mosquito trials in different areas of the world, and can also be applied to control other insect problems such as agricultural pests which risk food security. Furthermore, a factory in Brazil is set to be opened next week in order to raise and release these mosquitoes on a commercial scale in order to tackle Dengue Fever.

Dengue fever is the fastest-growing mosquito-borne disease in the world; incidence has increased 30-fold over the last 50 years, and currently it affects around 50-100 million people each year and causes around 25,000 deaths. It’s a viral disease spread primarily by two species of mosquito; Aedes aegypti and Aedes albopticus, although the former is responsible for the majority of transmissions. Dengue is sometimes nicknamed “breakbone fever” because of the agonizing bone pain associated with the illness, and severe cases may result in the often fatal manifestation dengue hemorrhagic fever. Currently there are no vaccines or effective antiviral drugs, meaning that mosquito control is the only viable option to control the disease....

A mosquito, photographed by ProjectManhattan , Wikimedia Commons, under the Creative Commons 3.0 license

Flood, poor sanitation result in health hazard around Monrovia

AllAfrica.com via New Republic (Liberia): One of the contaminated open wells, as the result of heavy downpours and Stockpile of dirt now causing mosquitoes in one of the communities hit by flood. The issue of poor sanitation in and around Monrovia, Liberia's Capital is going from bad to worst in the wake of on-going rainy season, resulting to heavy rain fall the past days.

The situation in Monrovia and its environs has increased sanitation problem, especially in communities affected by flooding. Affected areas include the Samuel Kanyon Doe Community, Clara Town, Topoe Village Community on the Somalia Drive and some parts of Jamaica Road, among other.

The heavy downpour of rain over the last few days socked huge piles of garbage resulting to unfavorable smells in most communities over taken by dirt, and creating mosquitoes as well. In some cases, the heavy downpours washed away the dirt and feces (caused from open defecation) in to wells and homes.

Residents in these communities informed the WASH Reporters & Editors Network of Liberia that heavy down pours over the last few days did not only increase the problem of poor sanitation, but also left their personally belongings destroyed...

Downtown Monrovia, shot by Erik (HASH) Hershman, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

A study finds that larvae control cuts malaria cases

Nick Kennedy in SciDev.net: Targeting mosquito larvae could cut malaria cases by up to 75 per cent in some sites, a review published today has found. The Cochrane review reports that a set of control methods, known collectively as larval source management (LSM), which kill mosquito larvae before they become malaria-carrying adults, could dramatically cut the disease's spread.

In some places, where the environmental conditions are right, this control method could reduce the number of people infected with the parasite by as much as 90 per cent, according to the review.

LSM techniques, which include draining land, adding larvicide to standing water or introducing animals that eat mosquito larvae, could boost malaria control efforts at a particularly challenging time for global malaria control.

"Malaria control is currently faced by various challenges, such as resistance to the main antimalarial drugs and insecticides, and new tools such as LSM are going to be increasingly needed," says lead author Lucy Tusting, a researcher from the London School of Hygiene & Tropical Medicine, United Kingdom.

Some malaria-endemic countries in Sub-Saharan Africa are already implementing LSM programmes, but there has been a lack of consensus on how effective the method is. Tusting and her team's report is the first large-scale review of the effectiveness of larval source management...

Mosquito larvae, shot by either Fir0002 or Fui in terra aliena (not sure which), Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license. Subject to disclaimers.

Mosquito numbers rising as Germany warms up

Deutsche Welle: Thanks to mild winters and moist air, mosquitoes are thriving in Germany. And not just the native species. Scores of exotic mosquito types are now moving here and the unwanted visitors are bringing dangerous baggage.

More and more species of exotic mosquitoes are arriving in Germany and with them the amount of dangerous infectious agents is rising, such as bacteria or viruses. Many of the mosquitoes hitch a ride on tourists or business travellers around the world before arriving in Germany.

Although they tend to survive for only a limited time and die out during the cold winter, experts say the climate in Germany will get warmer and the winters will shorten, meaning their numbers are set to continue to increase.

"The average temperature in certain regions is relatively high, and it's also getting wetter," says Sven Klimpel from the Senckenberg Gesellschaft für Naturforschung, a group of research institutes and natural history museums in Germany which conduct research into bio- and geosciences. "Those are ideal conditions for mosquitoes."

But it's not only the exotic pests causing scientists to worry. Native mosquitoes find the change in conditions equally appealing and are producing several generations of offspring each year...

Mosquito photo by Alvesgaspar, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Second door discovered in war against mosquito-borne diseases

Michigan State University Today: In the global war against disease-carrying mosquitoes, scientists have long believed that a single molecular door was the key target for insecticide. This door, however, is closing, giving mosquitoes the upper hand.

In this week’s Proceedings of the National Academy of Sciences, a team of researchers led by Michigan State University has discovered a second gateway that could turn the tide against the mosquitoes’ growing advantage.

For many years, pyrethroid insecticides have been deployed in developing countries to fend off diseases such as malaria, dengue fever and more. They’re so effective that they are the only insecticides the World Health Organization uses with their mosquito nets they distribute around the globe.

“Pyrethroids are effective because they eliminate mosquitoes while having few if any side effects on humans,” said Yuzhe Du, MSU electrophysiologist and one of the lead authors. “Our discovery of a second receptor in the mosquitoes’ sodium channel gives us a better understanding of how the insecticide works at a molecular level as well as could lead to ways to stem mosquitoes’ resistance to pyrethroids.”

...In the last decade, growing resistance in mosquitoes has been detected in many countries. At the molecular level, resistance appears as mutations in the primary receptor in the sodium channel that allow mosquitoes to survive exposure to the insecticide. The discovery of the second receptor in the sodium channel, however, opens up more avenues to increase pyrethroids’ effectiveness.

“One of the keys to the success of this research was our cloning of a mosquito sodium channel for the first time,” said Ke Dong, MSU insect toxicologist and neurobiologist and the paper’s senior author. “Another lead author of this study, Yoshiko Nomura, dedicated nearly one year to make this happen, which allowed Dr. Du to perform electrophysiological experiments with the clone.”...

Photo by Alvesgaspar, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Mosquitoes reared in cooler temperatures more susceptible to viruses that can affect human health

EurekAlert via Virginia Tech: Urban epidemics resulting from viral diseases, such as West Nile fever and chikungunya fever, are transmitted by infected mosquitoes. According to Virginia Tech scientists, mosquitoes reared in cooler temperatures have weaker immune systems, making them more susceptible to dangerous viruses and more likely to transmit them to people.

The connection between temperature and the mosquito's immune system, published Friday (May 31, 2013) in PLOS Neglected Tropical Diseases, is significant in light of global climate change, said researchers Kevin Myles and Zach Adelman, associate professors of entomology in the College of Agriculture and Life Sciences, and affiliates of the Fralin Life Science Institute.

"Our data offers a plausible hypothesis for how changes in weather influence the transmission of these diseases and will likely continue to do so in the future," Myles said.

A variety of weather anomalies may occur with global changes in climate. However, predicting what these weather anomalies will be is difficult due to the enormous complexity involved. Nevertheless, the work of Myles and Adelman suggest that it would be unwise to focus solely on warmer temperatures when considering links between climate change and disease transmission.

"Mosquitoes like to breed and lay their eggs in dark, cool places because that means the water will last longer," Adelman said. "They don't lay their eggs in sunny spots because that will dry the water out in a day or two. Although this has been known of some time, we are just learning about its potential affects on the mosquito immune response. Hopefully, this information can be used to build better models that more correctly predict when we'll have disease transmission."

Current computational outbreak models consider such things as meteorological variables and human population indexes but have failed to consider the effect of temperature on mosquito immunity, he added. Specifically, Adelman and Myles found that the mosquito's RNA interference pathway is impaired when reared at cooler temperatures.

The rate of transmission of both diseases has increased with outbreaks occurring in unexpected places, such as the introductions of West Nile virus to New York in 1999, and chikungunya virus to Italy and France in 2007 and 2010....

This image shows green fluorescent protein in the eyes of the mosquito Aedes aegypti when immunocompromised by cooler temperatures (left) compared with an immunocompetent sibling (right). Image from Virginia Tech

Global warming trends contribute to the spread of West Nile Virus to new regions in Europe

Newswise via the University of Haifa: Global warming trends have a significant influence on the spread of West Nile Virus to new regions in Europe and neighboring countries, where the disease wasn’t present before, according to a new study by the University of Haifa. The study was commissioned by the European Centre for Disease Prevention and Control (ECDC) in Stockholm, which belongs to the European Union. The study found that rising temperatures have a more considerable contribution than humidity, to the spread of the disease, while the effect of rain was inconclusive.

“These results are an additional testament that global warming contributes to the outbreak of mosquito-borne and other temperature-sensitive vector-borne diseases. The indications to this are piling up in different parts around the globe”, says Dr. Shlomit Paz, who led this research. These findings were recently published in the online scientific journal, “Plos One”.

West Nile Virus is spread by mosquitoes that repeatedly bite infected birds. The potential threat the infection poses to man is the possibility of causing irreversible brain damage or even death through encephalitis or meningitis. The elderly and people with weak immune systems are most susceptible.

...The current study examined the link between daily temperature, humidity and precipitation data and West Nile incidence in Europe and neighboring countries. “We used statistical tools and found that as a result of heat waves, a dramatic increase in the number of cases resulted from increased activity of the virus and a growth of the mosquito population”, claims Paz. According to her, these results were seen in various countries....

A CDC electron micrograph of the West Nile virus

Temperature changes effect growth of dengue mosquito

Phys.org: A significant field discovery analyzing how natural temperature fluctuations affect the growth rate of the dengue mosquito could lead to crucial control-and-prevention strategies, according to newly published research from Thomas Scott's Mosquito Research Laboratory and the Center for Vectorborne Diseases (CVEC), University of California, Davis.

The research, published March 8 in the PLOS ONE journal, shows that that "temperature effects on larval development time, larval survival and adult reproduction depend on the combination of mean temperature and magnitude of fluctuations," said lead author Lauren Carrington, a former postdoctoral fellow in the Scott lab and CVEC.

The scientists investigated how realistic fluctuations in temperature during the day influence the life-history traits and population dynamics of the dengue mosquito, Aedes aegypti. "The effect of temperature on insect biology is well understood under constant temperature conditions, but less so under more natural, fluctuation conditions," said Carrington, who completed her three-year postdoctoral fellowship last December at UC Davis but continues research projects with the Scott lab. She is now based at the Nossal Institute for Global Health, University of Melbourne, Australia.

The research, "Effects of Fluctuating Daily Temperatures at Critical Thermal Extremes on Aedes aegypti Life-History Traits," is expected to lead to greater accuracy of applications for mosquito surveillance and disease prevention. "An improved understanding of mosquito responses to natural temperature variation," Carrington said, "will enhance the effectiveness of vector control strategies, thereby reducing transmission of mosquito-borne diseases, such as dengue fever." By using constant temperatures, scientists can under- or -over estimate values, she said....

The aedes aegypti mosquito, carrier of dengue fever--image from the CDC