Texas fever returns
Anaplasmosis, the cattle disease that struck this week in Switzerland, is known as Texas fever in the United States.
Eradicated in the 1940s, it reappeared in the US as commercial exchanges with Mexico expanded.
Texas fever was first identified in North America in Virginia and Missouri around 1810. The disease, which causes cattle to become extremely anemic, has appeared all over the world for centuries.
Cattle imported from Spain
American scientists have concluded that the disease came from cattle imported from Spain when settlers to the "New World" arrived in Texas via the Antilles and Mexico.
In the 19th century Texan cowboys drove cattle toward the mid-west, where the animals were then shipped by railroad to large cities on the north, east, and west coasts.
The disease expanded across the United States, causing several states to take measures against it. In 1861, Missouri and Kansas - two important points of transit - prohibited the passage of Texan cattle through their territories.
When Britain and Germany threatened to stop importing American cattle, the government intervened. In 1895, Washington imposed quarantine on infected cattle, and created a line of demarcation between the north and south.
At the same time, two scientists at the Department of Agriculture isolated the source of the disease, a micro-organism that destroys the red corpuscles in the blood of infected animals.
The Mexican path
The scientists discovered that the illness was transmitted to cattle by ticks. This lead to a programme of cattle disinfections, with each animal at risk given a pesticide bath.
In 1943, the authorities concluded that anaplasmosis was eradicated in the US. But until the mid-1990s, the illness continued to resurface in Texas.
Veterinarians believe that the recurrence is due to expanded commercial exchanges brought about by the North American Free Trade Agreement (NAFTA).
The treaty contributed to the development of trade between breeders in Texas and Mexico, a country where Anaplasmosis is virulent.
To contain the disease, Texas has created a quarantine corridor along its frontier with Mexico.
A team from Texas A & M University is working on the development of a vaccine.
swissinfo/Marie-Christine Bonzom in Washington
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