There are many ways of fighting disease, but Brian Allan from Washington University has suggested a most unusual one – a spot of weeding. Allan’s research shows that getting rid of a plant called the Amur honeysuckle might be one of the best ways of controlling an emerging human disease called ehrlichiosis. The plant, however, doesn’t cause the disease. The connection between the two is far more complicated than that.
The Amur honeysuckle is an Asian plant that’s naturally alien to American shores. But, like many species that are brought to new habitats, it has become an invader. It forms thick growths that deprive native plants of light, causing local diversity to plummet in the face of an expanding blanket of honeysuckle. This story has been repeated all over the world with different species cast as invasive villains, and different communities cast as suffering victims. But the true consequences of these invasions often go unnoticed.
The honeysuckle doesn’t just crowd out local plants; Allan has found that it also attracts white-tailed deer. Where the deer go, so do their parasites, and these include the lone star tick, the animal that spreads ehrlichiosis. Through their blood-sucking bites, the ticks spread five species of bacteria that infect and kill white blood cells. This weakens the immune systems of their hosts and causing the flu-like symptoms that accompany a bout of ehrlichiosis.
Prions are proteins that have become bent out of shape. Their chain of amino acids folds up in an abnormal ways, and they can transmit this rogue alignment to their normal counterparts. As their numbers increase, they gather in large clumps that can kill neurons and damage brains. They most famously cause BSE in cows, CJD in humans and scrapie in sheep. But other mammals suffer from prion diseases too – the deer equivalent is called chronic wasting disease or CWD and it is shedding light on how prions are transmitted in the wild.
Gultekin Tamguney from the University of California, San Francisco, has found that even infected deer are contagious even when they are apparently healthy and show no outward symptoms. Their faeces are bursting with prions, and through these infectious dollops, deer effectively seed their environment with sources of contagion.
CWD can be very common in both wild and captive deer, and its quick spread suggests that individuals must be able to pass on infections from one to another, probably via their environment. Scientists have suggested that faeces could act as a vehicle for prions, but so far, no one had ever shown that.
Farmers and herders have known for centuries that herds of cattle have an uncanny ability to all point in the same direction. Last year, a group of German and Czech scientists discovered the reason behind this alignment – unbeknownst to humans for thousands of years of domestication, these animals have a magnetic sense. The team used Google Earth satellite images to rule out alternative explanations like the wind and the sun, and show that cow and deer herds tend to point towards magnetic north like a living, hoofed compass needle.
Now, the same team have found that high-voltage power lines, which emit strong magnetic fields of their own, disrupt the orientation of cattle and deer. Near these lines, their neat alignment goes astray and they position themselves at random. This disturbance becomes less and less pronounced as the animals stray further away from the power lines. This is yet further proof that cows and deer have a magnetic sense that’s only just become apparent to us.
A wide variety of animals navigate using the Earth’s magnetic field as a guide, but until recently, bats and rodents (including hamsters, mice and mole rats) were the only mammals to demonstrate this sense. In fact, the ability may be much more widespread, for these groups are small and easily tested in the kinds of laboratory experiments that would be impossible with larger creatures. To study the senses of cows and deer, Hynek Burda from the University of Duisberg-Essen was forced to be more creative.
He used pictures of herds of animals taken by Google Earth’s satellites to show that they line up according to the North-South poles, regardless of the position of the sun and in parts of the world with very different prevailing winds. In this new study, he made use of large magnetic anomalies caused by the presence of power lines to see if the animals’ behaviour was affected.