BIOLOGICAL SAFETY 



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^ BIOLOGICAL SAFETY IN THE VETERINARY DIAGNOSTIC VIROLOGY LABORATORY Pearson, J. E. 



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Biological safety and security is extremely important in the veterinary diagnostic virology laboratory. The 

 specimens received may contain agents known to be infectious to animals but the potential effect on humans is 

 unknown. This laboratory is often the first laboratory involved in an exotic disease outbreak. 



There are three areas to be considered when discussing biological safety. 



1. Protection of the laboratory worker. The danger of human infection should always be considered when any 

 potentially hazardous specimen is received, e.g., an encephalitis case. The hazard to all laboratory personnel 

 including mail handlers, janitors, maintenance, etc., must be considered. 



2. Containment of viral agents. Specimens received may contain infectious agents that are exotic to that 

 country and should not be released into the environment. This has taken on new importance recently with the hog 

 cholera eradication program, Venezuelan equine encephalitis in Mexico and velogenic viscerotropic Newcastle in 

 California. 



3. Protection of diagnostic procedures from contamination. A diagnostic virology laboratory as compared to a 

 research laboratory will usually have a variety of agents present in a relatively small area. Therefore it is important 

 that extra precautions be taken to prevent cross contamination. 



A virus laboratory has several problems associated with its specialized function. The use of antibiotics in 

 cultures and preparation of specimens helps to control possible bacteria infections and contamination. However, 

 many viral isolation procedures require grinding tissues which can produce viral laden aerosols. It is possible a human 

 infection may be produced before the causative virus is identified. 



Each laboratory has unique problems so a set of rules that are applicable to all cannot be developed. The 

 laboratory supervisor has the ultimate responsibility for biological safety. He must often consider the safest 

 technique as compared to the technique that would be the most efficient. Even though a variety of diagnostic 

 specimens may be received there is usually adequate history to make a decision as to what safety precautions are 

 required. The supervisor should be free to impose more stringent or lenient restrictions as the situation demands. 

 Often in a diagnostic laboratory only a relatively small area is needed for viral isolation and identification. The 

 biological security' in this area should be very stringent as compared to the area where serology with inactivated 

 reagents is being conducted. 



There are several good references available that describe methods for handling hazardous viral material, 

 particularly human pathogens, and on developing laboratory designs (1, 2, 3, 4, 5, 7). 



Following are some general precautions and security methods which have been applied within Diagnostic 

 Virology, Veterinary Services Diagnostic Laboratory, Ames, Iowa. As Chlamydia and Rickettsia agents are 

 propagated on the same host systems as viruses they are included. 



Air Handling Systems 



Control of aerosols, particularly as produced by tissue grinding techniques such as blendors, is important. The 

 most desirable method is to have the laboratory under negative pressure as compared to the corridors. Air is not 

 recirculated but exhausted to the outside atmosphere through biological filters. Isolating the virology laboratory in a 

 separate building will add a dilution effect to the air when it is released. It should still be passed through biological 

 filters because air currents can carry a relatively high concentration of virus in one direction. 



An alternate method is the use of biosafety cabinets or vertical laminar flow hoods in a room with 

 recirculating air. The biosafety cabinet is the safest type. It draws air into the hood from the room at 100 linear feet 

 per minute and exhausts through biological filters. This poses the additional hazard of drawing viral agents into the 



Numbers in parentheses refer to References at the end of this report. 



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