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By M.Sc. (Agric) Jan Sten Jørgensen, Danish Plant Directorate, Lyngby, Denmark, July 2008.
 
During the last couple of years, the International Association of Feedstuff Analysis – section Feedstuff Microscopy (IAG) has been engaged with the problems of Ambrosia seeds in compound feed for wild birds. This work has resulted in the development of the IAG method “Determination of Ambrosia feeds in feedingstuffs”.
 
The reason for this interest from IAG is the fact that Ambrosia, from being a plant with origin in North America, during the last decades has spread to many European countries starting in the South East area of Europe. This plant has now started to “invade” also the Northern European countries. The highly allergic pollen from this plant could be a strong risk for human health if it continues to spread. Because of the late flowering in September-October the season of exposure from pollen to allergic sufferer may be prolonged at least 2-3 weeks in the autumn. In Denmark the plant has up till now only been found sporadic, and in the official control of bird feed not much attention has been drawn to this topic. There is presently no Community legislation setting maximum levels of Ambrosia seed in feedingstuffs. Switzerland has introduced an  intervention value at 50 mg/kg feed which equals around 10 seeds/kg feed.
 
This was the situation until October 10th, 2007 when a press release came from the Danish Allergy Organization (Astma-Allergi Forbundet), a non-governmental organization, informing the public of the danger from the Ambrosia pollen and the spread of the plant also in Denmark. People were encouraged to remove and burn the plant if found. It was highlighted that the Ambrosia seeds could survive more than 30 years in soil, and that pollen from Ambrosia now was found more often in the pollen traps. These pollen originated not necessarily from “Danish plants” but also pollen brought from as far away as Hungary, Rumania, Serbia and Croatia. Travelers in these countries could be exposed and such exposures could be the first step for developing an allergic reaction. If the plant took root in Denmark it was estimated that up to 100,000 more persons could be allergic to pollen from this plant. To-day around one million out of a population of five million people in Denmark is allergic to pollen.
 
Because of this the Danish Plant Directorate immediately decided to determine the level of contamination of Ambrosia seeds in Danish feeds for wild birds, and a survey started in autumn-winter 2007.
 
16 samples were brought in for examination. 8 of the samples were single feedstuffs (Sunflower- and hempseeds) and 8 samples were compound feeds. The intention was to have feed from the most important producers and importers of wild bird feed in Denmark. The samples were examined for Ambrosia seed by using the IAG method, where only seeds between 1,5-4,0 mm are examined visually using a microscope at low magnification. The normal size for Ambrosia seeds is 2-4 mm. During examination also other undesirable seeds were picked out (eg. Datura seeds). 
 
In 8 of the samples Ambrosia seeds were found. The content varied from 38 – 975 mg/kg. 6 of the samples were compound feed and 2 were sunflower seeds. Datura seeds were found in 3 samples of compound feed and 2 samples of Sunflower seeds – but only in small quantities. The result is shown in annex 1. These results show exactly the same results as surveys published from other European countries (Switzerland, Germany)
 
Because of these results the Danish Plant Directorate and the main producers and importers of feedingstuffs for wild birds arranged a meeting. It was agreed that the main source for introducing the Ambrosia to Denmark was the presence of seeds in feedstuffs for wild birds. If the mild winters continues, these seeds would germinate and grow into flowering plants producing pollen and new seeds. If no action is taken the plant will spread and invade also the Danish fauna, and cause allergic reactions to thousands of new persons. Therefore it was decided to contact the suppliers of feedstuffs, and ask them to prevent the Ambrosia seeds in raw materials.

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