Two news bits regarding insects and Cordyceps related fungi came to my attention today.
First piece of research is on ant behavior and what seems like their vaccination program against Metarhizium anisopliae, a Cordyceps anamorph that is a pathogenic fungus. The second article reports on the hope of using the same Metarhizium to fight ticks in in New England, the vector for the spread of Lyme's disease.
Metarhizium anisopliae use as a insecticide is not a new approach. It was first used over 130 years ago. In 1879 Elie Metchnikoff used it in experimental tests to control the wheat grain beetle, Anisoplia austriaca. It was later used to control the sugar beet curculio, Cleonus punctiventris (for more details see MBCN). In recent years the use of Metarhizium anisopliae is being researched to control the spread of malaria by infecting the African mosquito Anopheles gambiae.
1. A German/Austrian researcher team published an article entitled "Social Transfer of Pathogenic Fungus Promotes Active Immunisation in Ant Colonies"
in PloS Biology describing what looks like Lasius ants vaccinating each other against theCordyceps anamorph Metarhizium anisopliae, which is a serious entomopathogene.
Author Summary
Close social contact facilitates pathogen transmission in societies, often causing epidemics. In contrast to this, we show that limited transmission of a fungal pathogen in ant colonies can be beneficial for the host, because it promotes “social immunisation” of healthy group members. We found that ants exposed to the fungus are heavily groomed by their healthy nestmates. Grooming removes a significant number of fungal conidiospores from the body surface of exposed ants and reduces their risk of falling sick. At the same time, previously healthy nestmates are themselves exposed to a small number of conidiospores, triggering low-level infections. These micro-infections are not deadly, but result in upregulated expression of a specific set of immune genes and pathogen-specific protective immune stimulation. Pathogen transfer by social interactions is therefore the underlying mechanism of social immunisation against fungal infections in ant societies. There is a similarity between such natural social immunisation and human efforts to induce immunity against deadly diseases, such as smallpox. Before vaccination with dead or attenuated strains was invented, immunity in human societies was induced by actively transferring low-level infections (“variolation”), just like in ants.
Citation: Konrad M, Vyleta ML, Theis FJ, Stock M, Tragust S, et al. (2012) Social Transfer of Pathogenic Fungus Promotes Active Immunisation in Ant Colonies. PLoS Biol 10(4): e1001300. doi:10.1371/journal.pbio.1001300
2. Scientists find fungus that kills Lyme disease-carrying ticks
BRIDGEPORT, Conn. — Local scientists have found a way to control the ticks responsible for passing Lyme disease on to humans. A new natural pesticide, derived from a strain of fungus that is deadly to the black-legged tick could help keep tick populations under control.
Unlike some synthetic pesticides that can be dangerous for more than just ticks, the fungus does not harm honeybees, earthworms or other beneficial insects.
The product was developed by a Fairfield-based company that was bought out by the Danish industrial biotechnology company Novozymes.
The Connecticut Agricultural Experiment Station’s field trials of the fungus helped obtain federal Environmental Protection Agency registration. Novozymes has built a plant in Canada to mass produce the product, Tick-Ex.
It will be commercially available in 2014, said Kirby Stafford, the station’s vice director and chief entomologist.
“A lot of people do have their yards sprayed with pesticides, and they are quite effective, because synthetic materials will give you an 85 to 100 percent success rate,” Stafford said. “But there are a special number of people who don’t want to use them. The (organic product) may be slightly less effective, but it’s giving people options. It certainly would fit in to organic land care.”
The pesticide is made of the F52 strain of the Metarhizium anisopliae fungus, which occurs naturally in soil. The station tested it on residential properties in northwestern Connecticut and found up to 74 percent fewer ticks after treatment.
Although rates dipped slightly in 2010, the number of people in Connecticut with Lyme disease has been steadily rising, according to the federal Centers for Disease Control and Prevention. Connecticut has the nation’s highest number of cases, relative to population. The first symptoms of the disease include headache, fever and rashes. But if left untreated, the disease can spread to the joints, heart and nervous system.
The overabundant deer population is one reason the disease is so widespread, according to the state Department of Public Health. Black-legged ticks feed on large mammal hosts, which in Connecticut are usually deer.
Many Lyme disease experts have said the solution is to cull the deer, but research shows that is only really effective when the deer are culled to very low numbers, said Louis Magnarelli, director of the Connecticut Agricultural Experiment Station.
The station has researched a number of methods to control Lyme disease.
It found nootkatone, a component of essential oil from Alaskan Yellow Cedar and grapefruit is toxic to ticks, and is highly effective.
As tests wind down, there is a small chance a company will pick it up because the cedar oil is only produced at a grade suitable for cosmetics and foods, making it expensive. Until production is scaled up for more commercial uses, it won’t be used to eradicate ticks, Stafford said. The station has also tested a garlic spray product, which suppresses tick activity for around two weeks. Scientists in Maine discovered that a rosemary oil product, EcoEXEMPT, will eradicate ticks for at least two weeks.
The nationwide tick control research community is pretty small, Stafford said. Between 2001 and 2012, the state Department of Health and the agricultural experiment station have received a little more than $2 million for public outreach and tick control research from the CDC. The CDC was expected to hand out two tick control grants in 2011, but based on available funds ended up only distributing one, which went to a research laboratory in Rhode Island.
Studies have found the fungus strain is also effective in killing bed bugs, but it won’t be marketed for that use just yet.
“I can’t see spreading the spores of this fungus into a bedroom,” Stafford said. “But it begs for a formulation of how you expose it to just the targets and not the rest of the environment.”
(c)2012 the Connecticut Post (Bridgeport, Conn.)
Distributed by MCT Information Services