Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Benign bacteria block mosquitoes from transmitting Zika, chikungunya viruses


Researchers at the University of Wisconsin-Madison have confirmed that a benign bacterium called Wolbachia pipientis can completely block transmission of Zika virus in Aedes aegypti, the mosquito species responsible for passing the virus to humans.

Matthew Aliota, a scientist at the UW-Madison School of Veterinary Medicine (SVM) and first author of the paper -- published today (July 1, 2016) in the journal Scientific Reports -- says the bacteria could present a "novel biological control mechanism," aiding efforts to stop the spread of Zika virus.

A strain of Aedes aegypti mosquitoes feed from a membrane of blood in a research lab insectary in the Hanson Biomedical Sciences Building at the University of Wisconsin-Madison on May 17, 2016.

Photo by Jeff Miller/UW-Madison

Thirty-nine countries and territories in the Americas have been affected by the Zika epidemic, and it is expected that at least 4 million people will be infected by the end of the year. Scientists believe the virus is responsible for a host of brain defects in developing fetuses, including microcephaly, and has contributed to an uptick in cases of a neurological disorder called Guillain-Barre syndrome. There are not yet any approved Zika virus vaccines or antiviral medications, and ongoing mosquito control strategies have not been adequate to contain the spread of the virus.

Researchers led by Jorge Osorio, a UW-Madison professor of pathobiological sciences, and Scott O'Neill of the the Eliminate Dengue Program (EDP) and Monash University in Melbourne, Australia, are already releasing mosquitoes harboring the Wolbachia bacterium in pilot studies in Colombia, Brazil, Australia, Vietnam and Indonesia to help control the spread of dengue virus. Their work is supported by the Bill and Melinda Gates Foundation.

An important feature of Wolbachia is that it is self-sustainable, making it a very low-cost approach for controlling mosquito-borne viral diseases that are affecting many tropical countries around the world.

"In two of our initial study sites in Australia, approximately 90 percent of the mosquitoes continue to be infected with Wolbachia after initial release more than six years ago" says O'Neill.

EDP has now received additional endorsement from the World Health Organization's Vector Control Advisory Group to conduct further pilot studies and scale up in endemic areas.

Wolbachia can be found in up to 60 percent of insects around the world, including butterflies and bees. While not typically found in the Aedes aegypti mosquito -- the species that also transmits dengue, chikungunya and yellow fever viruses -- O'Neill discovered in the early 1990s that Wolbachia could be introduced to the mosquito in the lab and would prevent the mosquitoes from transmitting dengue virus.

Zika virus belongs to the same family as dengue virus and Aliota and Osorio -- with co-authors Stephen Penaido at SVM and Ivan Dario Velez, at the Universidad de Antioquia in Medellin, Colombia -- asked whether Wolbachia-harboring Aedes aegypti may also be effective against Zika virus. They were also interested in studying the mechanisms behind Zika virus infection and transmission in mosquitoes.

In the study, the team infected mice with Zika virus originally isolated from a human patient and allowed mosquitoes from Medellin to feed on the mice either two or three days after they were infected. The mosquitoes were either harboring the same strain of the Wolbachia bacteria (called wMel) used in field studies or were Wolbachia-free and the mice had levels of virus in their blood similar to humans infected with Zika virus.

An additional group of mosquitoes, both wild-type and Wolbachia-infected, was allowed to feed instead from a membrane containing sheep's blood spiked with a high concentration of Zika virus, per other standard laboratory studies.

Four, seven, 10 and 17 days after the mosquitoes fed on Zika-virus-infected blood the researchers tested them for Zika virus infection, assessed whether the virus had disseminated -- or spread to other tissues in the mosquito, and examined whether the virus made its way to the mosquito saliva, where it must be present to be transmitted.

"The first site of replication for arboviruses is the mosquito midgut," says Aliota. "It eventually leaves the midgut and is swept in their blood to secondary tissues and eventually to the salivary glands, where it replicates more and is eventually spit out."

They found that mosquitoes carrying Wolbachia were less likely to become infected with Zika virus after feeding on viral blood, and those that were infected were not capable of transmitting the virus in their saliva.

"We saw reduced vector competence in Aedes aegypti with Wolbachia," says Osorio, defined as the intrinsic ability of an insect to support the development or replication of a pathogen like a virus and then transmit it. "Mosquitoes with Wolbachia were less capable of harboring Zika virus, and though they do get infected with Zika, it is to a lesser extent than wild-type mosquitoes."

They also found that where mosquitoes got their blood meal -- whether from mice or the membrane -- impacted their infection and transmission status. This has implications for other laboratory-based Zika virus studies, Aliota says.

Though mice had a lower concentration of virus in their blood than the blood contained in the membrane, mosquitoes that fed on the mice were infected at higher rates than those that were membrane-fed. The levels of virus found in the mice were also more similar to those seen in human infections.

Non-Wolbachia-containing mosquitoes that acquired Zika virus from mice were also capable of transmitting the virus in a shorter number of days, and in less time than other studies have shown. Additionally, the researchers learned that a relatively low percentage of Zika-virus-transmitting mosquitoes may be sufficient to sustain an outbreak.

"A surprisingly low percentage of mosquitoes are actually capable of transmitting the virus," Aliota says, "but given the size of the outbreak, and that we think mosquitoes are the driver of the outbreak, the results were somewhat unexpected. It just goes to show you how much we still need to understand about the basic biology of this virus."

The study is one of the first to study Zika virus transmission dynamics using a living host, says Aliota.

Importantly, the team also confirmed that the strain of Wolbachia used does not impact the Aedes aegypti mosquito, which is important to the success of field studies.

Once inside a mosquito, Wolbachia is passed from mother to offspring, so newborn mosquitoes will contain the bacteria and incorporate it into the wild population. EDP hopes to see greater than 80 percent of Aedes aegypti mosquitoes in study areas harboring Wolbachia. According to Osorio, mosquitoes carrying Wolbachia in the study site in Medellin are close to reaching that number.

Other studies show Wolbachia prevents mosquito transmission of yellow fever virus -- which is causing an outbreak in Africa -- and, in another study published in late April in PLOS Neglected Tropical Diseases, Aliota, Osorio and their UW-Madison and Universidad de Antioquia colleagues showed that Wolbachia prevents Colombian Aedes aegypti from transmitting chikungunya virus.

Like Zika virus, chikungunya emerged out of Africa and spread to the Americas. It is now transmitted by mosquitoes on every inhabited continent around the globe, says Aliota. The virus can cause fever, chronic joint pain, fatigue, nausea and a rash. There is no cure or specific treatment.

Aliota and Osorio continue to study Wolbachia in mosquitoes in relation to these viruses, monitoring for changes or developments that could affect ongoing field releases. So far the findings have been encouraging, Aliota says.

"Our findings are complementary to results described earlier in the month in Cell Host & Microbe by our colleagues with EDP-Brazil, which is really exciting and really promising," he says.


The Zika virus study was funded in part by the National Institutes of Health.

Kelly April Tyrrell,, 608-262-9772

Media Contact

Matthew Aliota


Matthew Aliota | EurekAlert!

Further reports about: Aedes aegypti Zika virus dengue virus mosquito mosquitoes viruses

More articles from Health and Medicine:

nachricht Scientists develop tiny tooth-mounted sensors that can track what you eat
22.03.2018 | Tufts University

nachricht NIH scientists describe potential antibody treatment for multidrug-resistant K. pneumoniae
14.03.2018 | NIH/National Institute of Allergy and Infectious Diseases

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Modular safety concept increases flexibility in plant conversion

22.03.2018 | Trade Fair News

New interactive map shows climate change everywhere in world

22.03.2018 | Earth Sciences

New technologies and computing power to help strengthen population data

22.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>