Laboratory workers who frequently handle research rats that commonly cause asthma symptoms have fewer allergic reactions to the rats than individuals with less exposure, according to a study at six pharmaceutical sites in Great Britain.
The findings appear in the first issue for July 2006 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
Meinir Jones, Ph.D., of the Department of Occupational and Environmental Medicine at Imperial College in London, and five associates analyzed the background information and blood tests of 689 pharmaceutical employees who had been exposed to lab rats in varying degrees.
The investigators wanted to learn more about the complex relationship between allergen exposure from the animals and the induction of human asthma. They noted that occupational asthma caused by an allergy to a laboratory animal can provide a useful model of allergic reaction from which exposure can be readily characterized and measured.
"We recorded the dates of their first and most recent handling of rats and estimated the duration of contact with rat proteins," said Dr. Jones. "Employees were classified according to the job they had that incurred the highest exposure to rats, with office and maintenance workers showing low exposure, scientists medium exposure, and animal technicians or cage cleaners high exposure."
There was close agreement between the exposure category associated with the job title and the maximum number of rats handled in one day.
"Approximately 38 percent had handled more than 50 rats per day, whereas 17 percent had never handled any," said Dr. Jones. "There were equal proportions, 23 and 22 percent, who had handled either from 1 to 10 or 11 to 50 rats. For 464 employees or 68 percent, their highest exposure to rat proteins came during their work as a scientist."