Tropical Diseases: Protection from Bites

How incredibly fast a mosquito-borne disease can spread geographically is shown particularly clearly by the example of the “West Nile” virus. The viral disease, which manifests itself 1-6 days after a mosquito bite with sudden high fever, headache, and pain in the limbs, was first diagnosed in Uganda in 1937.

West Nile fever in the United States

In 1999, there was an outbreak of West Nile fever in horses and birds in New York, which subsequently caused meningitis in humans. Since then, the virus has spread to many U.S. states, where it is endemic, especially in southern regions. For travelers to the U.S., complete mosquito protection is therefore an absolute must, as there is no vaccine protection yet.

Epidemiologists assume that the virus was introduced into the USA with an infected migratory bird, but possibly also through illegal bird trade. And the virus continues to spread. It has already been detected in Bulgaria, Romania, Hungary, the Czech Republic, Portugal and France.

It is possible that many cases of the typical summer flu are due to West Nile fever, the symptoms of which are indistinguishable from those of the flu in mild cases. In the United States, about 800,000 people now become infected with the virus each year, and about 20% of them become ill.

Data lacking

In many cases, researchers simply lack the data to detect the so-called “vector-associated” diseases in Germany. This refers to diseases transmitted by insects, ticks or mites – namely, the vectors. This is at least true for tropical diseases, which could soon occur in our country to a much greater extent due to climate change.

Among the domestic diseases, Lyme disease and early summer encephalitis (TBE), both diseases transmitted by infected ticks, are in the focus of scientists. Just recently, the Robert Koch Institute in Berlin expanded the number of TBE risk areas in Bavaria and Baden-Württemberg. To be sure, this expansion is due to a change in the definition that determines the criteria under which a county is considered a risk area for early summer encephalitis. However, the change in definition was made to allow for better prophylaxis and to protect more people from tick bites. This is because overall tick numbers are rising sharply nationwide.

The missing winter 2006/2007 will lead to a tick plague this summer, scientists are sure. Anyone who spends a lot of time outdoors in a tick-risk area should consider vaccination against early summer encephalitis. Against the other vector-associated diseases, on the other hand, only protection against the mosquito bite helps.

The spread of the pathogens and their vectors is unlikely to be prevented, because every piece of luggage, every car tire, in short every contact, offers the exotic offenders the opportunity to reach warmer Europe and survive there. Moreover, it is unlikely that the increased risk of infection applies only to the pathogens and diseases mentioned above.

In principle, this risk potential applies to all tropical diseases transmitted by insects. The transfer possibilities have long been valid – and climate change creates the necessary environment. This can only be changed if climate change does not become permanent and temperatures here drop again. Whether that will happen?