Rabies virus Agent Information Sheet

Boston University
Research Occupational Health Program (ROHP)
617-358-7647

Agent

Rabies is a disease caused by the rabies virus. Rabies virus belongs to the order Mononegavirales, viruses with single RNA genomes. Classified in the Rhabdoviridae family, which includes at least three genera of animal viruses, Lyssavirus, Ephemerovirus, and Vesiculovirus.

Disease/Infection

Progressive encephalomyelitis

Pathogenicity

Laboratory Associated Infections (LAI) is extremely rare. Almost all cases of clinical rabies are fatal.

Biosafety Information

Risk Group/BSL
Risk Group 2
Biosafety Level 2 Practices

Modes of Transmission
Rabies is most commonly transmitted to humans via the bite of a rabies-infected animal. The amount of virus reaching the lesion is also a factor in transmission; for example, when a bite has to penetrate clothing, the saliva may be retained in the fabric and be prevented from entering the wound. Potential non-bite modes of transmission include contamination of a pre-existing wound, contact of mucous membrane or respiratory tract with the saliva of an infected animal, exposure to aerosolized rabies virus in the laboratory (or from bats), or via organ transplantation from an infected donor.

Host Range/Reservoir
Humans, and many mammals, most commonly wild and domestic canids (e.g. dogs, foxes, coyotes), mustelids (e.g. skunks, badgers, martens), viverids (e.g. mongooses, civets, genets), procyonids (e.g. raccoons), and insectivorous and haematophagous bats.

Symptoms
It may take several weeks or even a few years for people to show symptoms after getting infected with rabies, but usually people start to show signs of the disease 1 to 3 months after the virus infects them. Rabies virus can cause an acute infection, marked by progressive encephalomyelitis, and is usually fatal. The initial symptoms of rabies resemble those of other systemic viral infections. This prodromal phase typically lasts about 4 days, but can last as long as 10 days before specific symptoms develop. Human rabies is typically seen in 2 forms: furious and paralytic (or dumb).

Furious rabies: Accounts for 80% of rabies cases, is dominated by encephalitis, and presents with hydrophobia, delirium, and agitation. Hydrophobia is the symptom most identified with rabies; patients have severe difficulty in swallowing and can become fearful at the sight of water despite an intense thirst. Other manifestations of furious rabies include hyperactivity, seizures, and aerophobia. Hyperventilation is frequently present, presumably reflecting brain stem infection. Patients then fall into a coma and typically die within 1 to 2 weeks, despite maximal intensive care.

Paralytic (dumb) rabies: In contrast to furious rabies, paralytic rabies patients lack signs of cortical irritation, instead presenting with ascending paralysis or symmetrical tetra paralysis. As the condition progresses, the patient becomes confused and death preceded by a coma may ensue

Incubation Period
Varies from days to more than 7 years, with 75% of patients becoming ill within 90 days of exposure.

Viability
Rabies virus is inactivated by exposure to 70% ethanol, phenol, formalin, ether, trypsin, β-propiolactone, and some other detergents.

Survival Outside Host
This virus does not survive well outside its host (in dried blood and secretions) as it is susceptible to sunlight and desiccation.

Information for Lab Workers

Laboratory PPE

Personal protective equipment includes but is not limited to laboratory coats or gowns, disposable gloves, and safety glasses. Special practices may be recommended based on risk assessment.

Containment

BSL-2 and /or ABSL-2 practices, containment equipment, and facilities are recommended for all activities utilizing known or potentially infectious materials or animals. Pre-exposure rabies vaccination is recommended for all individuals prior to working with agent. Additional primary containment and personnel precautions, such as those described for BSL-3, are indicated for activities with high potential for droplet or aerosol production, and for activities involving large quantities or high concentrations of infectious materials.

In Case of Exposure/Disease

• For injuries in the lab which are major medical emergencies (heart attacks, seizures, etc…):
  • Medical Campus: call or have a coworker call the Control Center at 617-414–4144.
  • Charles River Campus: call or have a coworker call campus security at 617-353-2121.
    You will be referred to or transported to the appropriate health care location by the emergency response team.
• For lab exposures (needle sticks, bite, cut, scratch, splash, etc…) involving animals or infectious agents, or for unexplained symptoms or illness call the ROHP 24/7 hour number (1-617-358-ROHP (7647); or, 8-ROHP (7647) if calling from an on-campus location) to be connected with the BU Research Occupational Health Program (ROHP) medical officer. ROHP will refer you to the appropriate health care location.
• Under any of these scenarios, always inform the physician of your work in the laboratory and the agent(s) that you work with.
• Provide the wallet-size agent ID card to the physician.

Vaccination

Rabies vaccination also is recommended for all individuals entering or working in the same room where lyssaviruses or infected animals are used. Pre-exposure immunization of individuals at high risk for exposure (e.g. laboratory workers, veterinarians, and animal handlers) can be done using Imovax Rabies, a human diploid cell vaccine (HDCV), or RabAvert, a purified chick embryo cell vaccine (PCECV). Use of booster doses and periodicity of serological monitoring is determined by the level and frequency of contact with agent.

Information for First Responders/Medical Personnel

Public Health Issues

Direct human-to-human transmission is theoretically possible but rare. Standard precautions can be used.

Diagnosis/Surveillance

Monitoring for symptoms is inadequate since, by the time symptoms are apparent, rabies is invariably fatal. Hence immediate post exposure prophylaxis as outlined below is important. No diagnostic methods are available during the incubation period. Following the incubation period, methods of detection include viral isolation, RT- PCR, and direct immunofluorescence of clinical specimens.

First Aid/Post Exposure Prophylaxis

First aid for rabies begins with good wound care, which can reduce the risk of rabies by up to 90%.

Post-exposure rabies prophylaxis with HDCV or PCECV together with the administration of rabies immunoglobulin (RIG) is highly effective, although this should not be used in persons who have previously received complete vaccine regimens (pre-exposure vaccination) who require vaccination only.

Perform one of the following actions:

Treatment

Following wound care, the clinician must decide whether to institute passive and/or active immunization. There is no established treatment for rabies once symptoms have begun; without post exposure prophylaxis, almost all patients succumb to the disease or its complications within a few weeks of onset. Supportive therapy includes intubation, sedation, mechanical ventilation, fluid and electrolyte management, nutrition, and management of intercurrent illnesses and complications.

References

Biosafety in Microbiological and Biomedical Laboratories; Deborah E. Wilson, DrPH, CBSP Director Division of Occupational Health and Safety National Institutes of Health Bethesda, Maryland L. Casey Chosewood, M.D. Director Office of Health and Safety Centers for Disease Control and Prevention Atlanta, Georgia; US Government Printing Office, Washington DC. 5th Edition; 2007

Control of Communicable Diseases Manual. David L. Heymann. Washington DC, USA: American Public Health Association Press, 19th edition, 2008

CDC Rabies http://www.cdc.gov/rabies/

Revised: 8/10/2012