control pests

Battle mosquitoes vigorously

India’s dengue deaths have long called for controlling mosquitoes through source reduction at breeding sites.

The WHO report describing the first Zika virus cases is important as it provides evidence of the virus circulating in India. While the Gujarat government says there’s no need to panic over the state’s three occurrences, it’s clear India must take greater precautions, more in areas where the Aedes mosquitoes are significantly present. The virus, which has no cure or vaccine but is not known to be deadly like dengue, was first found in India in 1964. It is known since 2015 that a virulent version, which swept the world and affected the Rio Olympics last year with some athletes withdrawing, could be headed for India as the more benign strain was within some people, and could prepare genetic grounds for the second coming.

Mosquito-borne diseases like malaria, dengue and chikungunya have taken more lives than other forms of pestilence. India’s dengue deaths have long called for controlling mosquitoes through source reduction at breeding sites. And yet the Gujarat CM took the pedantic line that there was no Zika patient in his state now as the three known cases were already treated. As none of the three had travelled abroad, it is likely the infection was picked up locally. However, the presence of Aedes aegypti and Aedes albopictus mosquitoes, which are active during daytime, and the general overcrowding, lack of hygiene and very warm summers are known to be grounds for an expanding threat. There has fortunately been no case yet of microcephaly (small head and brain in new-borns), but the war on mosquitoes must be fought with increased vigour.

Source: DECCAN Chronicle

Insects resist genetic methods to control disease spread, study finds

The research, reported in the journal Science Advances, combines advanced genetic and statistical analyses to show how certain genetic and behavioral qualities in disease-carrying insects, like mosquitoes, make these species resistant to genetic manipulation.

This resistance could complicate attempts to use CRISPR-Cas9 in the fight against malaria — a deadly mosquito-borne disease that threatens over 3 billion people worldwide — or crop blights such as the western corn rootworm, an invasive species that costs the U.S. about $1 billion in lost crops each year.

The discovery of the CRISPR-Cas9 system — or simply “CRISPR” — in the early 2010s introduced an unprecedented level of accuracy in genetic editing. Scientists can use the method to design highly precise genetic “scissors” that snip out and replace specific parts of the genome with sequences of their choosing. Two English scientists were the first to show the method could spread infertility in disease-carrying mosquitoes in late 2015.

“We found that small genetic variation within species — as well as many insects’ tendency to inbreed — can seriously impact the effectiveness of attempts to reduce their numbers using CRISPR technology,” said Michael J. Wade, Distinguished Professor of Biology at IU Bloomington. “Although rare, these naturally occurring genetic variants resistant to CRISPR are enough to halt attempts at population control using genetic technology, quickly returning wild populations to their earlier, ‘pre-CRISPR’ numbers.”

This means costly and time-consuming efforts to introduce genes that could control insect populations — such as a trait that causes female mosquitoes to lay fewer eggs — would disappear in a few months. This is because male mosquitoes — used to transmit new genes since they don’t bite — only live about 10 days.

The protective effect of naturally occurring genetic variation is strong enough to overcome the use of “gene drives” based on CRISPR-based technology — unless a gene drive is matched to the genetic background of a specific target population, Wade added. Gene drives refer to genes that spread at a rate of nearly 90 percent — significantly higher than the normal 50 percent chance of inherence that occurs in sexually reproducing organisms.

Wade, an expert in “selfish genes” that function similarly to gene drives due to their “super-Darwinian” ability to rapidly spread throughout a population, teamed up with colleagues at IU — including Gabriel E. Zentner, an expert in CRISPR-based genetic tools and assistant professor in the Department of Biology — to explore the effectiveness of CRISPR-based population control in flour beetles, a species estimated to destroy 20 percent of the world’s grain after harvest.

The team designed CRISPR-based interventions that targeted three segments in the genome of the flour beetle from four parts of the world: India, Spain, Peru and Indiana. They then analyzed the DNA of all four varieties of beetle and found naturally occurring variants in the targeted gene sequence, the presence of which would impact the effectiveness of the CRISPR-based technology.

The analysis revealed genetic variation in all four species at nearly every analyzed DNA segment, including a variance rate as high as 28 percent in the Peruvian beetles. Significantly, Wade’s statistical analysis found that a genetic variation rate as low as 1 percent — combined with a rate of inbreeding typical to mosquitos in the wild — was enough to eliminate any CRISPR-based population-control methods in six generations.

The results suggest that a careful analysis of genetic variation in the target population must precede efforts to control disease-carrying insects using CRISPR technology. They also suggest that the unintended spread of modified genes across the globe is highly unlikely since typical levels of genetic variation place a natural roadblock on spread between regions or species.

“Based on this study, anyone trying to reduce insect populations through this method should conduct a thorough genetic analysis of the target gene region to assess variation rates,” Wade said. “This will help predict the effectiveness of the method, as well as provide insight into ways to circumvent natural genetic variation through the use of Cas9 variants with an altered sequence specificity.”

Source: ScienceDaily

Fly landing on food have health risks, according to experts

They are one of the scourges of summer and have been ruining picnics since the dawn of time (probably).

Flies – harmless but incredibly annoying, most people think.

But it turns out the insects may be a lot more dangerous than we thought.

The average fly carries 200 different types of harmful bacteria, largely thanks to the various things they land on, such as rotting food and fecal matter.

Even if you swat one away as soon as it’s landed on your sandwich, the damage has already been done.

Thanks to thousands of tiny hairs on their arms and legs, the bacteria are quickly transferred to your food, which could pose a serious health risk according to a pest control expert.

“They only need to touch your food for a second for their legs or the tiny hairs all over their bodies to transfer germs from all those nasty things they eat onto what you are eating,” Ron Harrison, an entomologist and technical services director at Orkin pest control, told the Mail Online.

“And since flies can transfer serious, contagious diseases like cholera, dysentery and typhoid, it is probably best if you avoid eating things that a fly lands on.”

What’s more, flies nearly always vomit on any food upon which they land.

Unable to chew, the insects have to throw up digestive enzymes onto the food to dissolve it and allow them to slurp it up.

Of course, it’s hard to avoid any fly ever landing on your food again, so what can you do?

The best tactic is simply to cut off the part the fly has touched and throw it away. But you should be fine to continue eating the rest. Phew.

Source: INDEPENDENT

India begins outdoor caged trials of genetically modified mosquitoes

India launched a project aimed at suppressing the local Aedes aegypti mosquito population by introducing genetically modified mosquitoes, according to two companies involved in the plan.

A similar project was approved last year in Florida on the heels of the Zika virus outbreak, which has been driven primarily by A. aegypti mosquitoes. Both projects involve so-called self-limiting male mosquitoes — brand name Friendly (Oxitec) — that are genetically modified to produce offspring that do not survive to maturity.

Five open field trials of the mosquitoes in Brazil, Panama and the Cayman Islands each led to a more than 90% reduction of the wild A. aegypti populations, according to a news release from the British company Oxitec and Gangabishan Bhikulal Investment and Trading Limited (GBIT), an Indian company. Open field trials are also planned for India, pending regulatory approval, the companies said.

For now, the India project was launched on Jan. 23 with outdoor caged trials in Dawalwadi. In these trials, the genetically modified mosquitoes are released into cages to mate with wild-type A. aegypti mosquitoes, Matthew Warren, spokesman for Oxitec, explained to Infectious Disease News. The results are then compared with cages where the mosquitoes were not released, Warren said.

In November, officials in Florida authorized a plan to use Oxitec’s modified mosquitoes in a field trial in Monroe County. The decision by the Florida Keys Mosquito Control District (FKMCD) came after residents, apparently reluctant about the method at first, voted to approve the idea.

An earlier survey showed that residents did not support the use of genetically modified mosquitoes as insect control, but the survey was conducted before the Zika outbreak became headline news and prior to an FDA report that said the mosquitoes would have no significant impact on human health, animal health or the environment.

Oxitec is currently deploying the mosquitoes in the Cayman Islands and Piracicaba, Brazil, but Warren said the trial in the Florida Keys is not yet underway.

“We are working with the FKMCD to identify a new site for the trial, and are gathering and submitting additional information to the FDA,” Warren said. “At this stage I don’t have a timeline, but we’re working to ensure that it is held in the most rigorous way possible and launched as promptly as the regulatory process will allow.”

While India is not among the 76 countries that have reported evidence of mosquito-borne Zika virus transmission since 2007, WHO has said that any country with a population of Aedes mosquitoes is at risk for transmission.

The primary aim of the project in India seems to be decreasing cases of dengue and chikungunya, which also can be spread by A. aegypti mosquitoes. According to estimates published in 2014, dengue infects an average of 5.8 million people each year in India at a cost of more than $1.1 billion. The country also has seen outbreaks of chikungunya, including some last year, according to the news release.

“Increasing cases of dengue and chikungunya have been reported in recent years,” Shirish Barwale, member of the board of directors at GBIT, said in the release. “Presently available methods have not been effective against these public health hazards. We are very optimistic that this pioneering technology from Oxitec will help us to control the mosquito responsible for spreading these diseases.” – by Gerard Gallagher

Source: Healio

What a mosquito’s immune system can tell us about fighting malaria

Immune cells in a malaria-transmitting mosquito sense the invading parasites and deploy an army of tiny messengers in response. These couriers help turn on a mosquito’s defenses, killing off the parasites, a new study suggests.

This more detailed understanding of the mosquito immune system, published January 20 in Science Immunology, might help scientists design new ways to combat malaria, which infects more than 200 million people per year.

“If we understand how the mosquito reduces the parasite to begin with, we hope we can boost these mechanisms to completely eliminate these parasites [in mosquitoes],” says Kristin Michel, an insect immunologist at Kansas State University in Manhattan who wasn’t part of the study.

Different parasites in the Plasmodium genus cause malaria. The disease is spread by certain Anopheles mosquitoes. These mosquitoes have natural defenses against Plasmodium that keep them from being overrun with the parasites when feeding on an infected person’s blood. But malaria transmission still occurs, because some Plasmodium species are particularly skilled at evading mosquito immune systems.

Previous research has shown that hemocytes, the insect equivalent of white blood cells, help mosquitoes fight off pathogens. Carolina Barillas-Mury and her colleagues at the National Institute of Allergy and Infectious Diseases in Rockville, Md., injected Anopheles gambiae mosquitoes — a primary spreader of malaria in sub-Saharan Africa — with a dye that stained their hemocytes. Those mosquitoes snacked on mice infected with a rodent version of malaria. Then the scientists watched the dyed hemocytes’ response.
Parasite’s problem

Sensing the presence of a malaria-causing parasite, mosquito immune cells (teal) kill themselves and release microvesicles (red) that activate cellular machinery that fights off the parasites, a new study finds.

Hemocytes that detected certain chemical fingerprints left by the parasites began to self-destruct. These dying hemocytes released plumes of tiny vesicles that then activated the mosquito’s defenses against the parasite, the researchers found. The vesicles triggered a protein called TEP1 to take down the parasite. Scientists already knew that TEP1 is an important part of mosquitoes’ immune response against Plasmodium parasites, but it wasn’t clear how the protein was called into action. Without the vesicles, TEP1 didn’t target the parasites.

Barillas-Mury and colleagues don’t know exactly what the microvesicles contain. But she suspects they carry messenger molecules that jump-start TEP1 and other proteins involved in this immune response.

This type of response “is a very powerful defense system because it can make holes in the parasite and kill it,” says Barillas-Mury. “You want it to be active, but in the right place and at the right time.” Plasmodium parasites set up shop in different places in the mosquito gut depending on their life stage. Microvesicles, much smaller than the hemocytes, can more easily move through different gut compartments to trigger a localized immune response right where the parasite is.

The researchers eventually hope to use their understanding of the mosquito immune response to develop new ways to stop malaria. They’re interested in creating a vaccine that prevents mosquitoes that bite an infected person from passing along the parasite. Such a vaccine could be used in combination with others under development that would prevent people infected with the parasite from becoming sick, Barillas-Mury says.

Source: Sciencenews.org

Common insecticides are riskier than thought to predatory insects

Neonicotinoids — the most widely used class of insecticides — significantly reduce populations of predatory insects when used as seed coatings, according to researchers at Penn State. The team’s research challenges the previously held belief that neonicotinoid seed coatings have little to no effect on predatory insect populations. In fact, the work suggests that neonicotinoids reduce populations of insect predators as much as broadcast applications of commonly used pyrethroid insecticides.

“Predatory insects contribute billions of dollars a year to agriculture through the elimination of crop pest insects,” said Margaret Douglas, postdoctoral researcher in entomology, Penn State. “We have found that neonicotinoid seed coatings reduce populations of these natural enemies 10 to 20 percent.”

According to John Tooker, associate professor of entomology, Penn State, the use of neonicotinoids has risen dramatically in recent years, especially for large-acreage crop species like corn, soybeans and cotton. The insecticide is most often applied to seeds as a prophylactic coating. When the seeds are planted, the insecticide enters the soil where some of it is taken up by plant roots. The chemical then runs systemically through the plant, protecting young seedlings from insect pests.

“Applying insecticides to seeds rather than broadcasting them across a field was thought to reduce unwanted effects on natural enemies,” said Douglas. “But we found that seeds treated with neonicotinoid insecticides reduced populations of natural enemies by 10 to 20 percent in North American and European farming systems. Surprisingly, this effect was about the same as that associated with broadcast applications of pyrethroids.”

The team’s research appeared in the online journal PeerJ.

The team used a statistical method, called meta-analysis, to combine the results of more than 1,000 observations from 20 field studies across North America and Europe that tested the effects of seed-applied neonicotinoids on predatory insects. “Unfortunately, the available literature is difficult to interpret,” said Tooker. “Some studies show little influence of neonicotinoids presented as seed treatments on arthropod predators that are common in crop fields, whereas others show a strong influence of these seed treatments. By using a meta-analysis approach, we were able to combine the results of many studies to quantitatively reveal the overall influence of neonicotinoids on predator populations.”

Not only did the researchers find that neonicotinoid seed coatings significantly reduced natural enemy populations, they also found that the insecticide acted more strongly on insect predators than on spiders. In other words, spiders appeared to be less susceptible to neonicotinoids than insects, which is consistent with previous research.

“This result suggests that neonicotinoids are reducing populations of natural enemies at least partly through their toxic effects rather than simply by reducing the availability of their crop pest foods,” said Douglas. “After all, insects are more susceptible to these toxins than spiders, whereas the two groups should be similarly affected by a lack of food.” The researchers note that their results may help farmers and pest management professionals better weigh the costs and benefits of neonicotinoid seed treatments versus alternatives.

“Several governments have restricted the use of neonicotinoids out of concern for their possible effects on pollinators,” said Douglas. “But this raises the questions, ‘What will farmers do without these products? If they switch to broadcast applications of pyrethroids, will those products be better or worse for predatory insects?’ While our results do not speak to the pollinator issue, they do suggest that predatory insects are affected similarly by seed-applied neonicotinoids and broadcast pyrethroids.”

The answer to the problem, noted Tooker, lies in the application of integrated pest management (IPM), a strategy that uses a combination of techniques — which may or may not include the targeted use of insecticides — to control pests, rather than universally deploying prophylactic tactics like insecticidal seed coatings.

“Substantial research exists supporting the value of IPM for pest control,” he said. “It is the best chance we have of conserving beneficial insect species while maintaining productivity in our agricultural systems.”

Source: Science Daily