Viral cross contamination of rats maintained in a fabric-walled mass air flow system.

Rates for microbial cross transmission were measured in sentinel rats housed for 60 days in a fabric-walled mass air flow system. Naturally infected rats housed in the enclosure were the source of the infectious material. The cross transmission rates for rat coronaviruses, Kilham's rat virus, pneumonia virus of mice, Sendai virus, and Toolan's H-1 virus, were measured by positive seroconversion. The mass air flow system did not prevent, over a 60-day period, the transmission of the rat coronaviruses or Sendai virus between rats housed on separate racks maintained 81 cm apart. At 15 days, all sentinel rats had acquired two or more additional bacterial organisms, indicating rapid cage to cage cross transmission. It was concluded that rats from different sources with different microbial profiles should not be housed in this room at the same time.