Share thisFrom simple beginnings, IVCs have evolved into complex systems that filter contaminants and reduce labour.
Recently I was looking at the advanced technology of today’s individually ventilated caging systems (IVCs), and thought how easy it is to forget the humble beginnings of laboratory animal housing for rodents. From wooden boxes and glass jars to HEPA filtered air delivered directly to 100+ individually ventilated cages per rack, caging standards and the conditions of the micro and macro environments have dramatically improved over the years.
THE EVOLUTION OF IVCS
In the 1950s and 1960s, galvanised and stainless steel rodent cages were most common due to their durability and low cost. Plastic eventually beat out metal in most instances due to cost increases for metal products and the advantages of plastic being lighter, not easily misshapen, transparent, and having a lower heat transfer coefficient. In 1962, polycarbonate plastic was introduced and became the industry standard until polysulfone plastic caging surpassed polycarbonate due to its strength and reliability over many years of heavy use.
While the cage bottom was evolving due to the introduction of superior materials, researchers were still struggling with the limitations of open top caging. Open top caging served researchers well by providing an appropriately sized home for experimental rodents, however there was the issue of diseases spreading from cage to cage and infecting entire rooms and/or colonies. In 1958, Lisabeth Kraft published a paper while at Yale University detailing the use of a filtered cage to decrease the occurrence of epizootic diarrhea of infant mice (EDIM). In the mid-1970s, Robert Sedlachek invented, and Lab Products, Inc. developed, molded transparent plastic tops with filter paper inserts in the lids that began to be commercially produced in the mid-1980s.
While filter top cages were a step up from open caging, they still had their drawbacks. Many researchers appreciated the protection the filter tops afforded the animals, however the downside was the increased levels of moisture, ammonia, and carbon dioxide within the cages. Concerned about the intracage conditions of a filter top cage, Edwin P. Les of The Jackson Laboratory, USA was the first to develop the individually ventilated cage (IVC) concept. This new concept introduced filtered air directly into the cage. This advancement controlled the spreading of diseases from cage-to-cage, while providing a more acceptable microenvironment for the animals. In 1978, Les partnered with William Thomas of Thoren Caging Systems, Inc. to bring the first commercial IVC system to market. Other commercial vendors began to develop their own systems, and by the early 1990s these systems were widely accepted by the industry.
An attractive feature of the early IVC systems was that they not only created a better microenvironment for the animal, but they also reduced the number of times a cage needed to be changed per week. This greatly reduced labour, and the amount of resources needed to change and clean cages, lowering cost of operation.