A bite from a tsetse fly (采采蝇) is an extremely unpleasant experience. It is not like a mosquito, which can put its thin mouthpart directly into your blood, often without you noticing. In contrast, the tsetse fly’s mouth has tiny saws on it that saw into your skin on its way to suck out your blood.

To make matters worse, several species of tsetse fly can transmit diseases. One of the most dangerous is a parasite that causes “sleeping sickness”, or “human African trypanosomiasis” to give it its official name. Without treatment, an infection is usually fatal.

Like so many tropical diseases, sleeping sickness has often been neglected by medical researchers. However, researchers have long endeavored to understand how it avoids our bodies’ defence mechanisms. Some of their insights could now help us eliminate sleeping sickness altogether.

There are two closely-related single-celled parasites that cause this deathly sleep: Trypanosoma brucei rhodesiense and T. b. gambiense. The latter is far more common: it is responsible for up to 95% of cases, mostly in western Africa. It takes several years to kill a person, while T. brucei rhodesiense can cause death within months. There are still other forms that infect livestock.

After the initial bite, sleeping sickness symptoms often start with a fever, headaches and aching muscles. As the illness goes on, those infected become increasingly tired, which is where it gets its name. Personality changes, severe confusion and poor coordination can also happen.

While medication does help, some treatments are toxic and can themselves be deadly, especially if they are given after the disease has reached the brain.

It is worth noting that sleeping sickness is no longer as deadly as it once was. In the early 20th Century several hundred thousand people were infected each year. By the 1960s the disease was considered “under control” and had reached very low numbers, making its spread more difficult. But in the 1970s there was another major epidemic, which took 20 years to control.

Since then, better screening programmes and earlier interventions have reduced the number of cases dramatically. In 2009 there were fewer than 10,000 cases for the first time since records began, and in 2015 this figure dropped to fewer than 3,000, according to the latest figures from the World Health Organisation. The WHO hopes the disease will be completely eliminated by 2020.

While this decline looks positive, there may be many more cases that go unreported in rural Africa. To eliminate the disease completely, infections have to be closely monitored.

More problematically, a series of new studies have shown that the parasite is more complicated than previously believed.

Sleeping sickness has always been considered — and diagnosed — as a blood disease, because T. brucei parasites can readily be detected in the blood of its victims.

Scientists from Austria, Finland and Hungary are using laser scanners to study the day-night rhythm of trees. As it turns out, trees go to sleep too.

Most living organisms adapt their behavior to the rhythm of day and night. Plants are no exception: flowers open in the morning, some tree leaves close during the night. Researchers have been studying the day and night cycle in plants for a long time: Linnaeus observed that flowers in a dark cellar continued to open and close, and Darwin recorded the overnight movement of plant leaves and stalks and called it ''sleep. '' But even to this day, such studies have only been done with small plants grown in pots, and nobody knew whether trees sleep as well. Now, a team of researchers from Austria, Finland and Hungary measured the sleep movement of fully grown trees using a time series of laser scanning point clouds consisting, of millions of points each.

''Our results show that the whole tree droops(下垂)during night which can be seen as position change in leaves and branches, '' says Eetu Puttonen(Finnish Geospatial Research Institute), ''The changes are not too large,only up to 10 cm for trees with a height of about 5 meters,but they were systematic and well within the accuracy of our instruments. ''

To rule out effects of weather and location, the experiment was done twice with two different trees. The first tree was surveyed in Finland and the other in Austria. The leaves and branches were shown to droop gradually,with the lowest position reached a couple of hours before sunrise. In the morning, the trees returned to their original position within a few hours. It is not yet clear whether they were “woken up” by the sun or by their own internal rhythm.

Andras Zlinszky(Centre for Ecological Research,Hungarian Academy of Sciences) explains ''Plant movement is always closely connected with the water balance of individual cells, which is affected by the availability of light through photosynthesis(光合作用). But changes in the shape of the plant are difficult to document even for small herbs as classical photography uses visible light that interferes with the sleep movement. '' With a laser scanner, plant disturbance is minimal. The scanners use infrared light(红外线),which is reflected by the leaves. Individual points on a plant are only illuminated for fractions of a second. With this laser scanning technique, a full-sized tree can be automatically mapped within minutes with sub-centimeter resolution(分辨率).

''We believe that laser scanning point clouds will allow us to develop a deeper understanding of plant sleep patterns and to extend our measurement scope from individual plants to larger areas, like orchards or forest plots, '' says Norbert Pfeifer(TU Wien).

''The next step will be collecting tree point clouds repeatedly and comparing the results to water use measurements during day and night, '' says Eetu Puttonen. ''This will give us a better understanding of the trees' daily tree water use and their influence on the local or regional climate. ''

Scientists have recreated a 1985 study of birds in Peru that shows climate change is pushing them from their natural environment. Thirty years ago, researchers studied over 400 kinds of birds living on a mountainside in Peru. In 2017, researchers looked again at the bird populations. They found that almost all had moved to higher places in the mountain. Almost all had decreased in size. And, the scientists say at least eight bird groups that started at the higher elevations (高地) had died out completely.

The researchers say the birds might have moved up the mountain because of temperature changes. Or changes to food sources may have forced them to go higher. The findings were published in a science journal. The 1985 research has documented birds and other animals moving up in elevation (高地) in reaction to warming temperatures. Mark Urban, a biologist at a university, said this recent study was the first to prove that rising temperatures and moving to avoid them can lead to extinction.

In 2016, Fitzpatrick, director and a co-writer of the study passed his notes, photos and other records to Benjamin Freeman. Freeman has been researching tropical birds for more than 10 years. He set out in August and September of 2017 to copy Fitzpatrick’s study. His team used the same methods, searching the same places in the same time of year.

Freeman’s team wanted to see how things had changed for the bird groups since 1985. The average temperatures on the mountain had risen 0.42 degrees Celsius. His team placed 20 sound recording devices on the mountain to record the sounds of birds that might not easily be seen.

Freeman said that the birds moved an average of 98 meters further up the mountain. He believes that temperature is the main cause of the birds’ movement. Fitzpatrick noted that birds used to living in areas with little temperature change may be especially at risk because of climate change. He said, “We should expect that what’s happening on this mountain top is happening more generally in the Andes, and other tropical mountain ranges.”