Abstract
Dear sir,
I appreciated the contributions published in Veterinary Pathology, September 2009 (vol. 46, no. 5): “Mycoplasma pulmonis and Lymphoma in Bioassays in Rats,” by Schoeb et al (pp. 952–959), as well as “Confidence in Rodent Carcinogenesis Bioassays,” by Ward and Alden (pp. 790–791). They vividly demonstrate how ignorance can produce harm. Let me add, in a few words, my experience in dealing with a similar matter. In 1989, I was employed as a toxicologic pathologist with a major Swiss multinational chemical company. My employer was manufacturing an agrochemical that was appropriately tested for toxicity, registered, and successfully marketed around the world. One day, we received a message that this agrochemical was examined by scientists in a certain country and was found to be carcinogenic to rats. This message was very surprising because our agrochemical had been previously tested in chronic rodent studies in a renowned UK contract research laboratory and was found to be free of carcinogenicity. My employer sent me to visit these scientists and review the available data. My observations and conclusions were as follows: The chronic rat study was carried out under non-specific-pathogen-free conditions, in a room with free access for people and pets, much worse than conventional conditions, where any kind of infection was possible. No data were kept, save for photographs of tissue masses observed at necropsy in treated animals. Reportedly, such tissue masses occurred only in treated animals but not the control group. The scientists were not aware of the fact that aging rats develop spontaneous tumors. They were self-appointed toxicologists, and this study was the first—and, luckily, the only one—they ever carried out. I did not believe that they had any control animals. The microscopic slides were not available—they had been discarded! The original microscopic evaluation had been carried out by an MD pathologist in a local hospital. He found many lymphocytes in the lung and believed that the rats had lymphomas.
When I showed these scientists the rat volume of an American College of Laboratory Animal Medicine series, in the chapter dealing with mycoplasmal pneumonia where there was explicit warning about the possibility of confusing massive inflammation with lymphomas, the hosts started to be rude. They wished to have no more discussion, and I was asked to leave their country and never to return. They wrote a letter of complaint to my employer, accusing me of impolite behavior. Nowadays, we are increasingly concerned about new emerging diseases (see the recent issue of Veterinary Pathology). This story underlies the necessity of remembering the classical and supposedly eradicated diseases as well.