Julio Godoy
BERLIN, Jun 23 2007 (IPS) – The weather conditions in the heart of Europe were abnormal last year the summer too hot, too dry, and too long, and the winter too warm. But they were excellent for some foreign species, which, benefiting from the changed weather, settled in Germany, and have become a headache or worse for farmers and just about everybody else.
Adult deer tick. Credit: Scott Bauer/Agri.Research Service, USDA
The Culicoides imicola, for instance, a very small midge whose normal habitat is in sub-Saharan Africa, migrated to Europe during the last few years, and apparently has taken a liking to the new weather conditions in Germany.
The problem is, this midge transmits several viral diseases, including African horse sickness, and bluetongue disease, also known as catarrhal fever, affecting horses, sheep and, less frequently, cattle, goats, and even buffalo and deer.
This spring, in Germany alone, some 1,000 sheep have been affected by bluetongue. Although the disease is not transmittable to humans, 80 percent of the infected animals die.
We do not know much about the imicola, Helge Kampen, a researcher at the University of Bonn s Institute for Medical Microbiology, Immunology and Parasitology, told IPS. The university is located at the centre of the area where the midges and the disease have been identified in recent months.
We do have an approximate idea of which sort of midge is responsible for this epidemic, but our detailed knowledge is limited, he added.
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In August 2006, the researchers were aware that bluetongue disease is transmitted by the Culicoides imicola, which carries the virus. Both the vector and the virus are known from their impacts in tropical and subtropical areas, but had never before been detected in Germany.
However, at the time, the researcher at the University of Bonn found no traces of the bluetongue virus in the imicola midges found near Aachen, in the western border area with Belgium and the Netherlands.
It can be that our sample of the midges was too small to identify the virus, Heinz Mehlhorn, director of the Institute for Parasitology and Zoology at the University of Düsseldorf, some 100 kilometres north of Bonn, said in an interview.
One thing Mehlhorn could prove: The virus found in Germany has been common in the sub-Sahara region. Mehlhorn believes that the midge was transported to Europe through illegal animal imports, and that the hot summer and the warm winter in 2006 helped the midges and the virus to survive, until 2007.
We had hoped that a cold winter would kill all midges and virus, Mehlhorn told IPS. Instead, the weather helped the vector and the virus to survive until today.
A similar fate has favoured the proliferation of another insect species in Germany. The deer tick has profited from the abnormally warm temperatures of the last 12 months to proliferate, especially in southern Germany, leading to a medical alarm, and to scarcity in vaccines against borreliosis, or Lyme disease, and tick-borne meningoencephalitis or encephalitis, two diseases transmitted by the small arthropod.
In both cases, the viruses are transmitted by the tick through bites. Especially meningoencephalitis and the encephalitis, infections of the brain, or of the membrane surrounding the brain and spinal cord, can be mortal for humans, if not treated immediately.
The booming tick population in southern Germany has led to a run on vaccines, and to their scarcity. Drugs producers have announced that the vaccine won t be available again until mid-November, but pharmacies and other medical outlets have said the vaccine should be available again in a couple of weeks.
Yes, it is true that drugs producers are not delivering right now, but I think that the vaccines will be on the market by the end of June as the latest, said Hans Hillerbrand, spokesperson of the pharmacists association in Kelheim, a small Bavarian city some 400 km south of Berlin, and which has been one of the most affected by the proliferation of ticks.
While the warmer weather conditions have helped these species to multiply more rapidly, they are killing other animals, such as herring, the small oily fish typical of the North Atlantic and the Baltic seas.
Around the northern German seaside resort of Heiligendamm, on the Baltic, and which hosted the Group of Eight summit Jun. 6-8, hundreds of thousands of herring have been found dead, washed up on the beaches by seawater that is too warm for them.
Similar phenomena have been observed in other areas in the North Atlantic, around the German island of Sylt, just west of the Danish coast.
According to Harald Asmus, sea biologist at the Alfred Wegener Institute for Sea and Polar Research, the reason for the herring die-off is the proliferation of algae, which, when it dies, produces bacteria which take oxygen from water, and practically asphyxiate the herring.
The warm weather during the spring, and special wind and sea stream cycles helped the algae to grow in such a way that herrings could not survive, Asmus told IPS. We did measure only 17 percent of oxygen at the heart of the algae bushes, against more than 110 percent in water regions without algae, he added.
Other German biologists have found that abnormally warm seawater, even without algae, kills fish. Hans-Otto Poertner and Rainer Knust, also of the Alfred Wegener Institute, proved that fish in sea water warmer than 17 degrees Celsius have lower growth and higher mortality rates.
For their research paper titled Climate Change Affects Marine Fishes Through the Oxygen Limitation of Thermal Tolerance , Poertner and Knust used eelpout, a bio-indicator fish species for environmental monitoring from the North and Baltic Seas, to analyse the evolutionary consequences of too warm water.
A cause-and-effect understanding of climate influences on ecosystems requires evaluation of thermal limits of member species and of their ability to cope with changing temperatures, the researchers say in their document.
They add: We show that thermally limited oxygen delivery closely matches environmental temperatures beyond which growth performance and abundance decrease. Decrements in aerobic performance in warming seas will thus be the first process to cause extinction or relocation to cooler waters.
Poertner und Knust found that fish survive a very short time in waters warmer than 21 degrees Celsius. In addition, warmer water reduces fertility among fish, thus contributing to the decimation of future generations.
The main reason for these effects lies again in the smaller amount of oxygen in warmer water, asphyxiating the fish.
The researchers also estimated that the sea water temperatures in the North and Baltic seas near the German coast have increased by 1.13 degrees Celsius during the last 40 years. By the end of this century, temperatures could rise by up to 4.0 degrees Celsius.