Ragweed (Ambrosia) progression and its health risks: will Switzerland resist this invasion?

The purpose of this article is to alert physicians for the environmental and health threats of Ambrosia artemisiifolia (common ragweed) in Switzerland. Switzerland borders several heavily ragweed colonised areas. Up to 12% of the population suffers from allergies (hay fever, asthma) to ragweed pollen in these areas. Switzerland is beginning to be invaded by this plant. Currently, the ragweed pollen counts are still low but can reach local peaks that induce symptoms in allergic individuals. Ragweed allergy, however, is still rare in Switzerland. Because the amount of ragweed pollen was increasing in the last few years, identification and surveillance of ragweed plant foci was started. Colonisation is currently systematically monitored in Geneva and southern Tessin. Major accumulation of ragweed foci have been detected in the canton of Geneva, the western shore of the lake of Geneva belonging to the canton of Vaud, and in the southern part of the canton of Tessin, aside from minor foci registered all over Switzerland. The routes of ragweed invasion are presented and discussed. Current measures of ragweed containment and needs for the future are presented. The urge for these measures at an early stage of ragweed spread is underlined by the impracticability of eradication in highly colonised areas. The costs of preventing ragweed spread in Switzerland are likely to be several magnitudes lower than the treatment of a significant percentage of the Swiss population for ragweed pollen allergy. Because areas can change from low to heavy ragweed colonisation within a few years, the current window of opportunity to prevent further colonisation by ragweed should not be missed.