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Cause

The rabies virus is present in the saliva of infected animals; all warm-blooded animals are susceptible to rabies, and some may serve as natural reservoirs of the virus.

Occurence

The overall risk of exposure for travelers is low, but, as with local populations, risk is determined to a large extent by each individual's level of exposure to unvaccinated domestic animals. The risk for expatriate residents is of course cumulative, and children are at special risk since they may be less likely to avoid contact with animals, and they may be afraid to tell anyone they have been bitten if the bite is not serious enough (in their minds) to need adult or medical care.

Vaccination of pets and livestock is the most effective control measure in preventing disease and subsequent human exposure.

Transmission

While the only verified cases of human-to-human transmission have occurred as a result of corneal implants from infected donors, bite or non-bite exposures inflicted by infected persons are said in some countries to have transmitted rabies to other humans. Skunks have been infected experimentally by being fed infected animals.

Incubation

If the head of an animal or a person is severely bitten, symptoms may appear in as few as 14 days. Under rare circumstances illness may not develop for a year or more. The farther the bite is from nerve endings, the longer it takes to reach the nervous system and develop an infection; therefore, post-exposure treatment with vaccines can still be effective in preventing rabies even if there is a delay, but the delay should be a short as possible and especially if the bite was "central" rather than peripheral. It is also true that the bite of a rabies-infected animal does not invariably cause disease.

The disease is usually contracted from the bite of a rabid animal, but on rare occasions, contact of virus-laden saliva with broken skin may be sufficient to transmit infection. There have also been reported cases of human-to-human rabies transmission by corneal transplants; which demonstrates the importance of not using transplant tissue from anyone who died of a neurological illness of unknown cause.

All warm blooded mammals are susceptible to rabies, if bitten by a rabid animal.

When to Suspect Rabies in Animals

• Nervousness
• (Unusual) aggressiveness
• Excessive drooling and foaming at the mouth
• Other abnormal behaviour such as:
• Wild animals losing their fear of human beings; or
• Animals normally active at night being seen in the daytime.

Other early signs of rabies in animals include fever, loss of appetite, and often, altered phonation, such as a change in tone of a dog's bark. These signs are often slight, however, and may escape notice. After a few days, marked restlessness and agitation may develop, along with trembling.

An affected dog may growl and bark constantly and will viciously attack any moving object, person, or animal it encounters. If not restrained, it may leave home and travel great distances, inflicting much damage as it goes. This excited state usually lasts three to seven days and is followed by convulsions and paralysis. In some instances, signs of excitement and irritability are slight or absent, and paralysis develops within a few days of disease onset. In cases of this type, an early sign is often paralysis of the lower jaw, accompanied by increased salivation. This may cause the animal to appear to be choking on a foreign object, constituting a dangerous trap for humans, who, in attempting to be helpful, may unwittingly expose themselves to infection.

Diagnosis of rabies in animals is similar, in most respects, to the procedure in humans, but the disease is easier to confirm at an early stage, since the animal can be killed for detailed brain studies. However animals that die after long periods of illness may not have infectious virus in the brain due to the so-called "auto-sterilisation" phenomenon; in that event, the tissue or spinal fluid may need to be tested for antibodies which is a sophisticated procedure not usually available in many countries.

Once symptoms appear in man, the only treatment is vigorous supportive measures to control the respiratory, circulatory, and central nervous system symptoms. Recovery has occurred in a only 4 reported rabies survivors.

Clinical diagnosis of rabies in humans is based on the patient's history of exposure and development of characteristic symptoms. To confirm the diagnosis (usually not possible until late in the disease), rabies virus must be demonstrated in saliva or brain tissue. The virus may be identified on the basis of animal inoculation tests or specific staining with fluorescent antibodies but this requires sophisticated diagnostic procedures not available in many countries include identification of rabies antibodies in the patient's blood or cerebrospinal fluid and demonstration of characteristic Negri bodies in samples of brain tissue.

Preventive Measures

Pre-exposure vaccination is recommended for persons living in or visiting (for more than 30 days) countries with endemic dog rabies as above. Pre-exposure vaccination greatly simplifies, but does not eliminate, the need for post-exposure treatment. (Exposed persons who were not previously vaccinated require more vaccine doses, plus injections of rabies immune globulin.) Pre-exposure vaccination is given as a series of 3 injections (see below) and is used to protect travellers in circumstances where exposure may be inapparent, post-exposure therapy may be delayed, or locally available vaccines may pose a high risk of adverse reactions.

Pre-exposure vaccination is also recommended for travellers whose occupations, avocations or activities place them at frequent risk of exposure to rabies virus or to potentially rabid animals in epizootic areas. Those at risk are hunters, forest rangers, taxidermists, laboratory workers, stock breeders, slaughterhouse workers, veterinarians or spelunkers (people who go caving). Travellers who will remain at continuous or frequent threat of exposure due to high-risk activities or extended visits in high-risk areas should consult with their health providers every 2 years regarding the need to have their antibody levels checked and/or receive a booster dose of rabies vaccine. Maintenance of high antibody levels is especially important in situations where exposures may be inapparent or there may be delays in getting safe, effective post-exposure treatment.

The vaccine is considered safe for use during pregnancy, but should only be given if the disease risk clearly outweighs any risk to the unborn baby. Many developing countries are still using killed rabies vaccines prepared from baby mouse brains. Although effective, the unpurified vaccines may cause serious side effects as did the original Pasteur vaccine. Vaccinees may experience redness, swelling, and itching at the injection site; as well as headache, nausea, abdominal pain and muscle aches. Also, 5-10% of people receiving the series will develop an "immune complex-like" syndrome 2-20 days later with itching, fever, fatigue, joint pain, arthritis, nausea, and vomiting. A few rare cases of neurological complications have been reported from this immunisation, but all resolved by themselves. There is a rare chance that other serious problems and even death could occur after getting the vaccine. Such problems could happen after taking any medicine or after receiving any vaccine.

For international travellers, three 0.1 ml intradermal (ID) OR three 1.0 ml intramuscular (IM) vaccinations are given over a 21 day period (usually given on days 0, 7, and 21 or 28) for pre-exposure vaccination.

Persons who will also be taking mefloquine or chloroquine for malaria prevention should complete their three-dose ID rabies vaccinations BEFORE these medications are begun as they may interfere with the antibody response to rabies vaccine. Otherwise, the intramuscular (IM) dose/route should be used. This dose/route provides a sufficient margin of safety for persons taking anti-malarial drugs.

Prevention of rabies after animal bites is based on physical removal of the virus by proper management of the bite wound and on specific immunological protection by post-exposure vaccination: Rabies Immune Globulin and Vaccine as indicated: usually 20 iu/kg rabies immunoglobulin IM - half in the wound, half IM - and rabies vaccine on Day 0, 3, 7, 14, 30, and 90. It is ESSENTIAL to ALSO cleanse the wound immediately and THOROUGHLY with soap and water or even water alone to remove saliva from the area. The wound may then be squeezed to promote bleeding, since this will also help to clean it. The physician who treats the wound should again cleanse the contaminated area, with a 20 percent solution of medicinal soft soap or similar, and use a syringe to apply the solution to the full depth of the wound. The possibility of tetanus may necessitate more specific treatment such as excision of dead tissue if the wound is severe, as well as tetanus prophylaxis. The wound should not be stitched, unless unavoidable for cosmetic or tissue support reasons, to allow free bleeding and drainage.

VACCINATION IS NOT A SUBSTITUTE FOR THOROUGH WOUND CLEANING.

If at all possible, the dog or cat inflicting a bite should be captured alive and kept under surveillance. This may make it possible for the bitten individual to avoid undergoing rabies vaccination unnecessarily. If the animal remains healthy under confinement and veterinary observation for at least seven days, one may usually assume that it was not infective. If, however, the animal becomes ill or dies, as well as treating the victim, local health authorities should be notified immediately.

Checklist of Treatment for Animal Bites

1. Cleanse and flush wound immediately (first aid).
2. Seek medical help for thorough deep wound cleansing.
3. Rabies Immune Globulin and Vaccine as indicated: usually 20 iu/kg rabies immunoglobulin IM - half in the wound, half IM - and rabies vaccine on Day 0, 3, 7, 14, 30, and 90.
4. Tetanus prophylaxis and antibacterial treatment when required.
5. No sutures (stitches) for wound closure advised, unless unavoidable.
6. Follow-up for completion of vaccine program as well as for wound care.

Checklist for Bites in Children

• The injury is severe enough to require stitches.
• The cut or puncture wound is bleeding excessively.
• There are signs of infection. Signs of infection include severe swelling and pain and drainage of pus.
• Your child was bitten by an animal other than a vaccinated family pet. If there is a risk of rabies, your child may need a series of shots for protection.

Our appreciation to Dr. Rene de Jongh of International SOS, An AEA Company who has contributed this article in response to a growing health threat faced by expatriates in Indonesia.