Public Health Aspects of Rabies Control

Lecture 8

Dr. Paul Bartlett, MPH., DVM., Ph.D.

Source of Rabies Information

• CDC Web site – Very comprehensive!

• http://www.cdc.gov/ncidod/dvrd/rabies/Professional/professi.htm

Human Rabies Biologics(Rabies vaccines for people)

• Duck embryo vaccine– No longer available as of December, 1981– Post exposure required 23 SQ injections– Local reactions including pain, erythema, and induration at

the injection site were very common– Systemic reactions such as fever, malaise, and myalgia

occurred in about 33% of recipients.– When use as prescribed and used in conjunction with HRIG,

about 15% of recipients never achieved a protective titer.– Neuroparalytic reactions were rare.

Human Rabies Biologics(Rabies vaccines for people)

• Human diploid cell vaccine (HDCV)– Rate of allergic reaction usually, limited

to hives, is approximately 1 in 625– Guillaune-Barre-like peripheral

neuropathy = .3% – Another report says “30+% risk of severe

Arthrus reaction”– HDCV is administrated IM due to low

rate of reaction.

Human Rabies Biologics(Rabies vaccines for people)

• RabAvert Rabies Vaccine– Produced by the Chiron Corporation

– Purified chick embryo cell vaccine.

– Licensed in the US in 1997

– 14 million doses have been used worldwide

Immuloglobins• Equine antirabies serum (ARS)

– Still available but not the drug of choice because it produces serum sickness in 40% of adult recipients.

• Human rabies globulin (HRIG)– Serum from hyperimmunized persons provides

immediate passive protection against rabies.– Adverse reactions rare - drug of choice.– In a fresh bite wound, located in a fleshy part of the

body, all of the HRIG can be injected around the wound. If that is not possible then the remainder can be injected in the buttocks far from the site of the rabies vaccinations. Due to the large volume of HRIG involved, injection at several sites is recommended.

Rational for Rabies ImmunizationPre-exposure

• Pre-exposure immunization is recommended for persons whose vocational or avocational activities increase their exposure to animals which may be rabid.– Veterinarians (RR = 312), veterinary technicians, animal

wardens, hunters and trappers.

• Pre-exposure immunization protects against unknown exposures.

• Pre-exposure immunization allows for a rapid anamnestic rise in rabies titer if followed by vaccination or exposure.

Rational for Rabies ImmunizationPost-exposure

• Long incubation period of rabies allows us to immunize exposed individuals before the brain is affected, but it is most effective when begun early after exposure.

• Use of HRIG provides immediate passive immunization for 7 to 10 days, until the vaccine can induce active immunity.

• Local infiltration of HRIG is intended to prevent tissue fixation of the virus, but it is only effective immediately after a biting incident.

Recommended HDCV and HRIG Treatment Schedules - Pre-exposure

• Three doses total - on days 0, 7,and 21 or 28.

• No HRIG is given.

• Persons wishing to maintain a protective titer should have their titer determined and, if their titer is low, they should receive a booster dose.

• Most veterinarians with only infrequent exposure do not need to have their boosters or titers checked after the primary pre-exposure course.

Recommended HDCV and HRIG Treatment Schedules - Post-exposure

• 5 doses total - on days 0,3,7,14, & 28.

• HRIG should also be received on day 0.

• If the person has ever had a protective titer, or has ever had the recommended three-dose pre-exposure regimen, only two doses of vaccine recommended on days 0, 3 and no HRIG is needed.

Rational for TreatmentTen-day Observation Period

• Dogs, cats, and ferrets (as of November 1997) which live without clinical signs of rabies for 10 days following inflicting a bite can be safely assumed to have no rabies virus in their saliva at the time of the bite.– Most states have a law mandating a ten day

observation period be observed for dogs, cats, and ferrets after they bite a human.• Under the observation of a vet (in some states)

– Post-exposure vaccination for humans can be delayed when the capture of the correct animal is imminent.

Rational for TreatmentTen-day Observation Period

• The ten day observation period is only recommended for dogs, cats, and ferrets. All other biting animals should be immediately euthanized and sent to the laboratory for rabies testing. (but there are exceptions)

Rational for TreatmentLocal Rabies Prevalence

• Information regarding the prevalence of rabies in your area is available from your local or state health department.

• Some major metropolitan areas of the USA have been free from rabies in terrestrial mammals for many years.– Chicago and New York City are among these.– Animal bites occurring in these areas may not require post-

exposure immunization.• This does not include bites inflicted by bats.

Rational for TreatmentSpecies of Biting Animal

• Bites from non-mammals never pose a rabies threat.• Bites from rodents, lagomorphs, and opossums in the USA

generally do not necessitate rabies prophylaxis.– Recently however there have been considerably more

instances of rodents and rabbits being found with rabies.• Animals species in different regions of the country represent

differing degrees of rabies exposure potential.– Skunks in the Midwest.– Raccoons in the southeastern and eastern USA.

Rational for TreatmentNature of Bite

• Deep bites to the head are more likely to transmit rabies.– Bites to the head are more likely to induce

rabies and are more likely to result in a shorter incubation period.

• Approximately 15% of bites from known rabid animals will result in transmission of rabies if the person is not treated (Winkler, CDC).

Rational for TreatmentAnimal Tissue Contacted

• Central nervous system tissue, spinal fluid, and saliva are the tissues of major public health importance.– Other tissues such as muscles, skin, musk

(skunk spray), and fat have negligible amounts of virus.

• Contact with blood, urine, or feces does not constitute an exposure

Disposition of Exposed Animals

• Each state has different regulations regarding handling of animals exposed to rabies (or suspect rabid animals).

• The CDC recommends that exposed dogs, cats, and ferrets which are currently vaccinated be euthanized, or revaccinated then observed in confinement for 45 days.

• Exposed dogs, cats, and ferrets whose vaccination status is not current should be euthanized or confined for 6 months with vaccination 1 month prior to their release.

Animal Bite Trauma• Confinement is frequently defined differently in

various states.– Most states specify “confinement under the

supervision of a veterinarian.”• Regardless of the treat of rabies, animal bites in

themselves can represent a serious public health hazard.– 18 to 20 people, usually children, die each

year from wounds inflicted by dogs. So…• It should be the responsibly of all veterinarians

to encourage the euthanasia of vicious dogs from the canine population to remove this public health hazard.

Veterinary Care of Wild Animals

• Wild animals, most notably skunks and raccoons, can create a considerable health hazard when people attempt to domesticate them.

• The exposure potential for rabies for humans is greater than for dogs or cats because:– Wild animals frequently bite and

scratch their owners.

Veterinary Care of Wild Animals

• The American Veterinary Medical Association, CDC, National Association of State and Public Health Veterinarians, and the US Animal Health Association strongly discourage the vaccination or de-scenting of wild animals.– Killed rabies vaccine has not been proven effective

in these animals, and may give the owner a false sense of security.

– De-scenting skunks make them a better pet and thereby encouraging ownership.

Veterinary Care of Wild Animals

• In Michigan and most other states, permits must be obtained to keep most species of wild animals in captivity.

• In Michigan and other Midwestern states, permits are never issued to the general public for owning skunks, and rarely issued for raccoons.– Veterinarians should not treat wild animals such as

skunks or raccoons without first making sure that the owner has the proper documentation for ownership of these animals.

Clinical Course

• Incubation periods vary with virus strain, dosage on inoculum and host species.– Man - 3 to 66 weeks on

average, but maybe up to a year

– Dogs - 3 to 8 weeks average, but maybe up to 6 months

– Cats - 9 to 51 days– Skunks - 22 to 177 days

– Foxes - 12 to 153 days– Bats - 6 to 145 days– Bovines - 20 to 165 days

• Typical syndrome; disposition change, irritably, dysphasia, incoordination progressing to either the furious or dumb form followed by paralysis, coma and death.

Control of Rabies (see “Compendium of Animal Rabies Vaccines”)

• In domestic animals, rabies control is based upon vaccination, quarantine, stray control and education.

• For several years, there have been more rabid cats reported in the US than rabid dogs, yet most states do not have cat vaccination laws.

• Rabies vaccine must be evaluated for safety.– MLV are no longer approved by the USDA.

Veterinarian’s Responsibility in Rabies Control

• Actively assist in planning and executing local rabies control programs including health education.

• Examine the biting dog or cat initially and take the following actions:– Observe and record any clinical symptoms of the

animal.– Notify the health department of the examination

results.– Advise the owner on the best means of confinement

and observation.

And Finally…

Veterinarian’s Responsibility in Rabies Control

• Re-examine the dog, cat, or ferret during the ten day observation period– Notify the health department as soon as possible if a

diagnosis of rabies is possible.• Confirmation of the diagnosis of rabies is NOT needed.

– If the dog, cat, or ferret exhibits no symptoms of rabies at the end of the 10 day observation period, report to the health department that the animal was not capable of transmitting rabies at the time of the bite and recommend that it be released from confinement.

Veterinarian’s Responsibility in Rabies Control

• Remember that in the 10 day observation period you are not trying to confirm a diagnosis before you call the health department. You are looking for any signs which may in any way be compatible with rabies. – Do NOT wait for an animal to die or exhibit signs

more definite signs.– Do NOT wait until you can “confirm” some other

diagnosis.

Veterinarian’s Responsibility in Rabies Control

• Educate clients on the advantages of dog, cat and ferret immunization and dangers of allowing pets to run loose.

• Encouraging rabies immunization is not only ethical, but actually the responsibility of the veterinarian.

• Notify the health department of all animal bites and suspected rabies cases.

• Inform clients of the possibility of rabies when treating bite wounds on their animals.

Veterinarian’s Responsibility in Rabies Control

• Remember that the 10 day observation period is only possible for dogs, cats, and ferrets.

– In other species, rabies virus may be shed over a more variable period of time.

– Other species should be sacrificed and sent to the laboratory for examination as soon as possible.