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Zoonotic Diseases

(Text Modified from Document Created by Michael S. Rand, DVM, ACLAM)

Institutional Policies and Procedures

Introduction

Table 1 should alert investigators working with these animals of the potential for inadvertent introduction of zoonotic diseases into animal colonies, causing possible disease exposure and infection in laboratory workers. Preventing laboratory acquired infections requires a five-pronged approach, including: appropriate engineering controls; appropriate quarantine and stabilization of the animal; appropriate work practices and procedures (including supervisory control); appropriate personal protective devices; and training. This approach is especially important in preventing clinically silent laboratory acquired infections, such as Lymphocytic Choriomeningitis Virus or Herpesvirus B in animals. The universal precautions approach used when manipulating human blood or blood products offers an analogous situation: staff members should follow safe work practices rigorously whenever working with (zoonotic) agents that may not induce signs of ill health in the animal.

Infection Control in the Laboratory and Animal Facility

Since zoonotic diseases can enter the body through a variety of methods including broken skin or through the eyes, mucus membranes, or the lungs, a combination of engineering controls, work practices, and personal protective devices are necessary to prevent laboratory acquired infection.

Engineering Controls

Of these routes of entry, controlling transmission by the aerosol route is the most difficult. The facility (laboratory, procedure, or animal room) must operate with inward directional air flow; i.e., air must move from the corridor (area of least contamination) into the room where staff members manipulate the animal or animal by-products (area of greatest contamination). Air exhausted from these rooms cannot be recirculated to other rooms; the air must be discharged to the outside. When there is a very high potential for aerosol generation, additional facility related engineering controls such as sealed penetrations through the walls, double door access to the rooms, or installation of HEPA filters in the exhaust air system may be necessary. A facility can also apply engineering controls locally to reduce aerosol spread. Containment devices (e.g., bonnet tops for cages, ventilated racks) will help keep a potential zoonotic agent in the cage. Staff should use biological safety cabinets when opening the cages, conducting sampling or necropsy activities, or manipulating infectious materials. All biological safety cabinets and the high efficiency particulate air (HEPA) filters in ventilated cage racks need to be certified and leak tested annually. Staff should use special devices such as sealable centrifuge cups, blenders, or homogenizers whenever there is a high potential for creating aerosols of infectious microorganisms. Workers must also rely on personal protective devices, such as respirators, to minimize their exposure to infectious aerosols when containment devices offer insufficient protection.

Animal Quarantine and Stabilization

Quarantine is the separation of newly received animals from those already in the facility until the health of the animal has been evaluated. Effective quarantine minimizes the introduction of disease agents into established colonies. The quarantine period should be of sufficient duration to allow expression of diseases present in the incubation stages. Some or all of the following should be achieved during the quarantine and stabilization period: diagnosis, control, prevention, and treatment of diseases; physiological and nutritional stabilization; and, grooming to include ectoparasite control (many zoonotic agents require an arthropod vector!).

Work Practices and Procedures

Handwashing is an important means of preventing the spread of infectious contaminant. Workers should wash their hands after removing gloves and before leaving the laboratory, procedure room, or animal room. A handwashing sink should be located near the door of the room. Liquid soap dispensers are preferable to soap bars to minimize cross contamination. After thorough washing, workers should dry their hands with disposable paper towels. Eating, drinking, smoking, handling contact lenses, and applying cosmetics should not be permitted in laboratories, nor should any other activities that might involve hand-to-mouth or hand-to-eye contact, such as mouth pipetting. Staff members should perform all manipulations of potentially infectious materials so as to minimize aerosol production. The person who generates infectious waste or contaminates equipment, work surfaces, or other areas is responsible for decontamination before the next person begins work. Chemical disinfection or, preferably, steam autoclaving, is recommended for decontaminating reusable materials before washing. When finished working, staff members must dispose of contaminated waste materials, and package them according to local infectious waste regulations prior to disposal.

Personal Protective Devices

Staff members can protect against splashes and splatters by adhering to careful work practices and rigorous use of personal protective devices. Face shields provide protection for eye and mucus membranes. Biological safety cabinets provide near sterile work environments that offer protection to the worker, the materials they are manipulating, and the work area itself. Lab coats or work uniforms will help prevent contamination of street clothes and should be changed whenever visibly soiled. Staff members should autoclave lab coats before disposal or laundering; soiled labcoats should go to on site or professional cleaners only. Latex or vinyl gloves provide barrier protection for hands. Staff must change gloves that are torn or visibly contaminated, and should autoclave them before disposal. Gloves and other protective devices cannot prevent needle sticks or other unintentional injuries caused by sharp instruments, broken glass, etc. Self sheathing needles are available, as are other engineered safety devices. Needles must not be bent, cut, or recapped: they must be discarded directly into puncture resistant and leakproof containers.

Training

All at-risk persons working in a facility should receive appropriate training on that facility's particular biohazards, precautions, and biohazard evaluation procedures. Personnel should receive annual updates and additional training when procedures or policies change. Laboratory workers and animal care personnel should know how to recognize hazard warning signs, to protect themselves and their coworkers against each hazard, and to react properly in the event of emergencies, such as an unintentional biohazard material release. Training should be appropriate for the employee's education, experience, and language skills, and should be performance based to ensure that employees master the skills before encountering a hazard. The facility should incorporate the syllabus of the training programs into its safety manual. Supervisors should assess each employee's biosafety knowledge during the formal training period and later through subsequent regular observation of routine activities. All persons who work in a laboratory bear responsibility to minimize risk of infection through consistent good safe microbiological practices and procedure.

Role of the Facility Director

The facility director may be the veterinarian, researcher, facility manager, or other individual responsible for day-to-day operations and the occupational health and safety of facility employees. Laboratories working with infectious human disease agents should elect a director who is knowledgeable and experienced in laboratory microbiology; this becomes increasingly important when staff are conducting work at BSL3 and BSL4. The facility director is responsible for ensuring that all employees have appropriate training regarding potential laboratory hazards such as chemicals, radioactive materials, and infectious microorganisms. The director must establish and maintain appropriate biosafety level practices and procedures in the laboratory or animal facility; and, it is incumbent on the director to ensure necessary biosafety materials and equipment are available to all personnel. To maintain facility safety, the director should review the research protocols and, based on the anticipated risks and necessary precautions, limit access to the laboratory or animal facility to those persons who have been advised of these potential risks. In general, immunocompromised persons or those for whom infection might be unusually hazardous should not have access to the animal room. Furthermore, the director should establish policies or specific requirements necessary for worker health and safety. In conjunction with occupational health personnel, the director can establish medical surveillance programs for staff members who plan to work with specific microorganisms. The facility may collect employee serum samples periodically and store them for subsequent testing under strict monitoring by appropriate management control to guarantee confidentiality and informed consent. The director should ensure that the laboratory and animal rooms are posted with hazard warning signs incorporating the universal biohazard symbol, listing the names of the microorganisms in use, the personal protective equipment to be worn in the room, special required practices and the names and phone numbers of persons to contact in case of emergency. Staff members should immediately report unintentional exposures to infectious materials to the supervisor or director, who will arrange for medical evaluation, treatment, and subsequent surveillance as needed. At-risk personnel should inform supervisors of any febrile illness as part of ongoing surveillance for potential laboratory associated infections. In addition, the director should maintain appropriate written records of all unintentional releases, spills, and exposures to biohazardous materials. The laboratory director should also make sure that an appropriate detailed biosafety manual, incorporating established guidelines as minimum standards for handling injuries, spill cleanup, waste handling, etc., is developed for the facility. This manual can then become part of the overall employee occupational safety and health program and a basis for on-the-job training activities. Granting agencies and regulatory organizations (OSHA, APHIS, AAALAC) which inspect animal facilities often request such manuals.

Conclusions

To prevent laboratory acquired infections, laboratory and animal care workers must carefully follow published explicit biosafety guidelines and must be cognizant of special biosafety hazards posed and animal husbandry practices needed by animals. Staff members should perform any animal work with infected materials (e.g., clinical specimens, tissues, tumor cell lines) at ABSL-3. Propagation of tumor cell lines in animals, especially in immunocompromised animals, requires particular biosafety vigilance, including quarantine of newly acquired animals, screening of cell lines and animals from nonstandard sources for extraneous infections, regular sentinel surveillance of laboratory animals, and preventing feral or wild animal access to the animal facility. In addition, laboratory personnel must be aware of the potential for extraneous infections in the laboratory, and how such infections would present in workers, animals, and cell lines. Any facility engaged in animal passage of cell lines not carefully tested for various microorganisms such as arenavirus or hantavirus should reevaluate their extraneous microbiological monitoring programs and insist on rigorous adherence to appropriate engineering controls, work practices, and procedures to prevent similar outbreaks.

References

Collins, CH. 1993. Laboratory-Acquired Infections. Elsevier Publishers, Boston, MA.

Chomme, BB. 1992. Zoonoses of house pets other than dogs, cats, and birds. The Pediatric Infectious Disease Journal. 11(6):479-87.

Cooper, JE. 1977. Diseases of lower vertebrates and biomedical research. Laboratory Animals. 11(2):119-23.

Guide for the Care and Use of Laboratory Animals. 1985. National Institutes of Health, Bethesda, MD.

Fox JG and NS Lipman. 1991. Infections transmitted by large and small laboratory animals. Infectious Disease Clinics of North America. 5(1):131-63.

Hubbert, WT, WF McCulloch, and PR Schnurrenberger. 1975. Diseases Transmitted From Animals to Man. Charles C. Thomas Publishers, Springfield, IL. Richmond, JY, CA Dykewicz, LM Aldeman, et al. Working safely with LCMV-infected immunocompromised animals. Lab Animal. May, 1994:25-28.

Schlossberg, D. 1994. Infections of Leisure. Springer-Verlag, New York, NY.

Telford, SR, RJ Pollack, and A Spielman. 1991. Emerging vector-borne infections. Infectious Disease Clinics of North America. 5(1):7-17.


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