Reducing exposure to laboratory animal allergens.

Laboratory animal allergy is a serious health problem. We examined several possible allergen-reducing strategies that might be effective in the working mouse room. Ambient allergen concentrations were measured when mice were maintained under several conditions: conventional housing versus ventilated cage racks operated under negative or positive pressure. We found that housing mice in ventilated cages operated under negative pressure and using ventilated changing tables reduced ambient mouse allergen (Mus m 1) concentrations tenfold, compared with values when mice were housed in conventional caging and using a conventional (non-ventilated) changing table. Housing mice in positively pressurized cages versus conventional cages did not reduce ambient allergen values. Cleaning mouse rooms at an accelerated frequency also did not reduce ambient Mus m 1 concentration. We also quantified ambient allergen values in several areas of The Jackson Laboratory. A facility-wide survey of Mus m 1 concentrations indicated that allergen concentrations were undetectable in control areas, but ranged from a mean (+/- SEM) 0.11 +/- 0.02 ng/m3 to 5.40 +/- 0.30 ng/m3 in mouse rooms with different cage types. The percentage of animal caretakers reporting allergy symptoms correlated significantly with ambient allergen concentrations: 12.9% reported symptoms in the rooms with the lowest allergen concentration (0.14 +/- 0.02 ng/m3), but 45.9% reported symptoms in rooms with the highest concentration (2.3 +/- 0.4 ng/m3). These data indicate that existing technology can significantly reduce exposure to laboratory animal allergens and improve the health of animal caretakers.

Assessing the risk of transmission of three infectious agents among mice housed in a negatively pressurized caging system.

Previous studies from our institution have shown that ventilated caging run at negative pressure to a mouse room dramatically reduced exposure of personnel to the major mouse allergen, Mus m 1. The current study was designed to determine whether negative cage ventilation posed an inordinate risk for spread of infectious agents between cages and/or racks. B6;129S-Tnfsf5(tm1Imx)/J (TNF) mice, which were naturally and persistently infected with Pneumocystis carinii, Helicobacter bilis, and Pasteurella pneumotropica, were used as the source of infections. Uninfected C3Smn.CB17-Prkdc(scid)/J (SCID) mice with severe combined immunodeficiency were used to detect transmission. The following methods were used to detect transmission of infections: polymerase chain reaction (PCR) amplification and histological examination of lungs for P. carinii; PCR of fecal specimens or cecal contents for H. bilis; and culture of oropharyngeal, tracheal, or vaginal swabs for P. pneumotropica. We determined whether transmission of the three agents occurred via direct contact (cohabitation), exposure to soiled bedding, and/or by handling naive SCID mice after handling infected TNF mice. During a 12-week period, all three infectious agents were readily transmitted to uninfected mice by cohabitation. Transmission was much less efficient and occurred later among mice exposed to contaminated bedding. Transmission did not occur as a result of handling. We then studied transmission of the three infectious agents among mice housed in individually ventilated cages run at negative pressure in a small, crowded mouse room. Transmission of P. carinii was detected at the end of the 12-month study in the densely populated room, probably because the exhaust from the changing station passed over soiled cages and caused aerosolization of particulates. Caging systems run at negative pressure effectively reduce personnel exposure to allergens and may also inhibit the transmission of infectious diseases.