Rheumatoid arthritis: Are pets implicated in its etiology?

Rheumatoid arthritis (RA) is thought to be triggered by an environmental agent or agents in immunogenetically predisposed persons. To investigate if animals or animal products might be the disease reservoir for a putative environmental trigger for RA that acts in childhood, a case-control study was undertaken. Included were 122 cases of RA and 114 control subjects of similar age. A specifically trained assistant, blinded to the diagnosis, used a standard interview proforma to gather information on ages of exposure to agents before onset of symptoms. Univariate analysis showed that cases were significantly more likely to have had a close association with a cat in the prepubertal period (65%) than were controls (27%); odds ratio (OR), 4.9 (confidence interval [Cl] 2.7 to 9.0). In addition, there was a dose-response relationship between extent of prior exposure to cats and RA. There was a weaker association between recalled prior exposure to birds, budgerigars (parakeets) in particular, and RA. These data suggest that certain pets may be the reservoirs for environmental agents that trigger RA after a period of latency. (C) 1996 by W.B. Saunders Company