Mosquitoes also spread tropical chikungunya viruses at low temperatures
New experiments conducted at the insectarium (high biosafety level 3) of the Bernhard Nocht Institute for Tropical Medicine (BNITM) and at the DZIF show that chikungunya viruses are able to replicate in Asian tiger mosquitoes at relatively mild temperatures of 18 degrees centigrade. Consequently, a potential chikungunya virus spread in non-tropical regions such as Germany is conceivable, should the tiger mosquito become endemic.
Tropical disease pathogens, such as Zika, dengue and West Nile viruses, usually require very warm temperatures over a period of several weeks in order to replicate in mosquitoes. “Average temperature conditions of 25 to 27 degrees do not usually occur in Germany which results in dual disease control: first, due to the relatively low temperatures and second, due to a low prevalence of corresponding transmitters such as Aedes albopictus, the Asian tiger mosquito,” explains Prof Egbert Tannich, Head of the National Reference Centre for Tropical Pathogens at the BNITM and scientist at the DZIF.
Chikungunya viruses are evidently an exception: authorities have reported outbreaks in European countries with significantly lower temperatures than in the tropics, for example in Italy (2007, 2017) and France (2010, 2014, 2017). For this reason, BNITM scientists conducted experiments with mosquitoes and infection. In a specific laboratory of high biosafety level (BSL3 insectarium), they fed blood containing chikungunya viruses to Aedes albopictus mosquitoes from Germany and Italy, and subsequently kept them in environmental chambers with average temperatures of 18, 21 or 24 degrees for two weeks.
“The viruses in the German mosquito population were able to replicate very well at a temperature of 18 degrees. Two weeks later we confirmed the presence of infectious viruses in the saliva of over 50 percent of the mosquitoes,” summarises Tannich. “In contrast to other tropical viruses, chikungunya virus transmission is therefore not so much determined by external temperatures but rather more by the presence of transmitting mosquitoes. However, the danger of chikungunya virus transmission to humans is currently rated low, as tiger mosquitoes have only been found in localised regions and in small numbers” Tannich reassures. “Additionally, in order to be able to transmit the virus, the mosquito first has to bite a person who has chikungunya viruses in his/her blood.
Nonetheless, both Tannich and Prof Jonas Schmidt-Chanasit, Head of the arbovirology group at the BNITM, strongly recommend that all European countries that have established populations of Aedes albopictus implement corresponding mosquito surveillance systems and control measures. “A further spread of tiger mosquitoes can only be prevented by reducing or eliminating existing mosquito populations,” says Schmidt-Chanasit.
Source and further information: BNITM Press Office
