Guidelines for Handling Animal Reservoirs of Hantavirus: Field Practices in Arizona

Rodents are known reservoirs of hantaviruses, and other small mammals can be infected as well. In Arizona, deer mice (Peromyscus spp.) are the implicated reservoir for a strain of hantavirus pathogenic to humans. Deer mice are common throughout the state. Although current evidence indicates that the rodents harboring hantavirus are most prevalent in rural settings, suburban or urban areas cannot be excluded as potentially affected. These guidelines apply to handling Peromyscus.

Exposure is believed to result from inhalation, inoculation into broken skin, and biting. Persons have been infected after only a few minutes exposure to laboratory rodents infected with a similar virus.

People who frequently handle or are exposed to rodents (e.g., mammalogists, field biologists, pest-control workers) are at higher risk for hantavirus infection than the general public because of their frequency of exposure. The likelihood of infection with hantavirus is low, but the fatality rate for the Muerto Canyon (NM) strain is high (approximately 60%) and diagnosis and treatment can be difficult. Therefore, enhanced precautions are warranted to protect against infection.

It is the responsibility of each worker and the supervisor to ensure that appropriate protective measures are used.

Guidelines

  1. For all persons whose work involves frequent rodent contact, before beginning work in the field, it is recommended that a baseline serum sample be drawn and stored at the Student Health Center.

  2. Workers in potentially high-risk settings should receive thorough orientation about the symptoms of the disease and hantavirus transmission. They should be given detailed guidance on prevention measures and trained to perform the required activities safely.

  3. Workers who develop febrile or respiratory illness within 45 days of potential exposure should immediately seek medical attention and inform the physician of the occupational risk of hantavirus infection. The physician should contact local health authorities promptly if hantavirus-associated illness is suspected. A blood sample will be obtained and sent with the baseline serum to the Arizona State Department of Health Laboratory (ASHL) for hantavirus antibody testing.

  4. When handling rodents, removing implicated rodents from traps, excavating nests, or exploring rodent burrows in an affected area, it is recommended that workers wear a half-face air-purifying (negative-pressure) respirator with HEPA filters or a powered air purifying respirator (PAPR) equipped with HEPA filters. Respirators (including positive pressure types) are not protective if facial hair interferes with the face seal, since proper fit cannot be assured.

  5. Hantaviruses are lipid-enveloped viruses which are susceptible to most disinfectants -- dilute hypochlorite solutions (bleach), 70% alcohol, detergents, phenolics, or most general-purpose household disinfectants. The survival time of the virus in the environment in liquids, aerosols, or dried states is not known.

  6. Workers should wear rubber, plastic, or latex gloves when handling rodents or traps containing rodents or contaminated by rodents. Before removing the gloves, wash gloved hands in a disinfectant and then in soap and water. Thoroughly wash hands with soap and water after removing gloves. If this is not possible, then rinse gloves with water or use a disinfectant wipe; wash your hands thoroughly at the end of the work period.

  7. Disinfect all traps contaminated by rodent urine or feces or in which a rodent was captured. If this is not done until the end of the trapping run, always wear a respirator whenever handling contaminated traps and transport the traps in closed plastic bags.

  8. Dispose of dead rodents by placing the carcasses in a plastic bag containing enough disinfectant to thoroughly wet the carcasses. Seal the bag and dispose of it as animal waste.

  9. Workers performing high-risk procedures such as removing organs or obtaining blood from rodents in an affected area should contact ADHS (Arizona Department of Health Services) for detailed safety precautions.

Specific Recommended Practices

I. Visual Survey of Area, Walking or Hiking
No special precautions are needed for protection against hantavirus infection. However, respiratory protection may be advisable in a known affected area which is visually contaminated by rodents or has especially dusty conditions.

II. Setting Trap Lines
Wear leather or thick rubber gloves when handling clean traps, to protect against sharp edges. Respiratory protection is recommended if the traps have not been disinfected from prior use.

III. Recovering Traps Containing Animals
Wear protective clothing, including rubber gloves. If using open-mesh traps, wear respiratory protection. Eye protection is recommended. To avoid contamination of vehicles, place traps which contain animals into a non-air-tight, but air flow restrictive secondary container. Use caution to avoid hyperthermia of the animals.

IV. Handling Live Animals
Wear protective clothing, including gloves, eye protection, and respiratory protection. If biting is a possibility, use appropriate methods to provide protection against both bites and urine contamination of hands. Define a zone to exclude others who are not wearing appropriate protective equipment. Work with the wind at your back if possible. Perform all procedures in a manner to minimize aerosol creation.

When possible, anesthetize the animal before handling. Remove captured animal from the trap by shaking it into an anesthesia bag; or alternately, pinch the animal's skin through the mesh of the trap with forceps, and inject the animal with anesthetic.

If it is not possible or appropriate to use anesthesia, wear protective clothing as described and use appropriate restraining devices. Avoid creating aerosols.

Wearing gloves, disinfect contaminated traps. The ideal method is to submerge them in a bucket of disinfectant for 10 minutes, rinse twice with water, and set in the sun to dry. Alternatively spray the traps with disinfectant. If traps are not to be disinfected until the end of the project, store them in closed plastic bags.

V. Field Dissection
Field dissection is strongly discouraged. Instead, transport animals to a laboratory to process them under safer working conditions.

If field dissection is done, wear protective clothing, including latex gloves, eye protection, and respiratory protection. Surgical gowns, booties, and head coverings provide additional protection.

Process animals in an isolated area. Use the minimum number of workers to do the job safely. Define and mark a zone to exclude others not directly involved in the animal dissection. Work with the wind at your back.

Perform all procedures carefully to minimize the creation of aerosols. Use extreme caution with any contaminated sharp items, including needles, syringes, slides, pipettes, capillary tubes and scalpels. Substitute plastic ware for glass whenever possible.

Use hypodermic needles and syringes only for gavage, parenteral injection, or aspiration of fluids from diaphragm bottles or well-restrained animals. Use only needle-locking syringes or disposable syringe-needle units. Do not bend, shear, break, recap or otherwise manipulate needles by hand before disposal; place used disposable needles and other sharps in a conveniently located puncture-resistant container.

Decontaminate the sharps container before disposal. Place non-disposable sharps in a hard-walled closeable container, preferably containing a suitable disinfectant. Do not handle broken glassware directly; use mechanical means such as brush and dustpan, tongs, or forceps.

Place tissues or specimens of body fluids in a container that prevents leakage during collection, handling, processing, storage, transport, or shipping. Carcasses may be preserved and transported in 10% formalin, dry ice or liquid nitrogen.

Dispose of unwanted carcasses in a plastic bag containing enough disinfectant to thoroughly wet the carcasses; seal the bag and dispose of it as animal waste.

VI. Clean Up
Place used instruments into disinfectant for 10 minutes. Decontaminate all wastes appropriately before disposal.

Remove protective clothing in a well-ventilated area (such as outside). Bag clothing in plastic bags for disposal or laundering.

Wash hands thoroughly with soap and water.

VII. Additional Precautions
Establish practical and effective protocols for handling emergency situations.

VIII. Additional Information
Arizona Department of Health Services, Vector Born and Zoonotic Disease Program, Craig Levy (602)230-5918

Mills, J. N., T. L. Yates, J. E. Childs, R. R. Parmenter, T. G. Ksiazek, P. E. Rollin, & C. J. Peters. 1995. Guidelines for working with rodents potentially infected with hantavirus. Journal of Mammalogy 76(3):716-722. (copies available from the Animal Care Program).