‘Viral aphrodisiac’: Cricket disease leads Dalhousie University researcher to uncover unique sexually transmitted virus
Dalhousie Biologist Shelley Adamo and her team have discovered that one of the most unique sexually transmitted diseases nature has to offer is more disturbing than previously thought. The cricket virus not only effectively castrates its host, leaving them unable to reproduce, but also changes their behaviour so they continue to have more sex than usual.
The virus, IIV-6/CrIV, only infects or transmits through cold-blooded organisms. While it was first identified in crickets over a decade ago, Dr. Adamo and her team have identified a new, unexpected behavioural element to the virus.
After examining infected crickets housed in her laboratory, Dr. Adamo and her team noticed the virus not only rendered the crickets sterile but also changed their behaviour: they continued to mate with each other when infected and made infected males courted females more quickly.
While the team is not yet certain exactly how the virus works, it appears to affect communication between the immune and nervous systems. By preventing typical illness responses (loss of appetite, decline in desire to mate), the virus makes the cricket more likely to mate, therefore, to spread the virus. In some cases, the virus did not require the crickets to have sex and was transferred during courtship rituals.
The team believes the virus, a parasitic manipulator, may yield interesting applications through further research.
“I was working on stress responses in crickets when I found the virus. I brought in reptiles, bearded dragons, for the predators in the study. The bearded dragons were carrying the infection and they gave it to my crickets. At first I didn’t notice anything different because their behaviour was absolutely normal. Usually you notice quickly if the crickets are infected. Infected crickets don’t move around very much; they certainly don’t mate, and they don’t eat. However, these crickets looked and acted perfectly normal. The only reason I found out was because the females stopped laying eggs. By the time I noticed, the virus had infected the entire population.” Says Shelley Adamo, Department of Psychology and Neuroscience.
“What is happening is not unusual for many parasitic organisms. A parasite wants to hijack the host and get as much energy as it can without killing the host. If the host dies, the parasite dies and cannot reproduce. For many of them, including this virus, the organ system that can be removed without killing the host is the reproductive system. Now all that energy that is usually used by the host for reproduction can be used by the parasite to help make more viruses. How the virus causes the shift in behaviour is interesting in a sick, fascinating way.” Says Shelley Adamo, Department of Psychology and Neuroscience.
“If I were to follow up with this I would look into how sickness behaviour is shut off. That is an issue that goes much deeper than crickets and could have broader impact. Sexually transmitted infections run the gamut of pathogens, from viruses to bacteria, and if studied further this issue we might find common pathways they use to suppress sickness behaviour.” Says Shelley Adamo, Department of Psychology and Neuroscience.
|Cricket, Gryllus texensis |
Photo Credit: Shelley Adamo
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