Kothmann i 1970 ansat i det tyske Forskningscenter for Virussygdomme hos Dyr og dernæst - i 1972 - i veterinærforvaltningen for Niedersachsen.
After a period of general veterinary practice, Dr Kothmann joined the German Federal Research Centre for Animal Virus Diseases in 1970 and the veterinary administrative service for Lower Saxony in 1972.