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When a best friend bites

The risks and management of dog-inflicted wounds.

By Sean Obmerga

MARCH 2013 

The night before a long weekend, I rushed home to pick up some stuff for an out-of-town surfing trip. Acknowledging a neighbor walking her adorable Shih Tzu, I was surprised when the cuddly canine lunged at me. Later, as I changed clothes, I noticed my thigh bleeding. Taking a closer look, there were three small puncture wounds—each mark about the size of a match head.

Dog bites and their risks

More than the pain associated with a dog bite, the threat of getting infected with rabies is frightening. Dog bites are the most common cause of rabies. It’s a zoonotic disease, meaning it can be transmitted from animals to humans. According to the World Health Organization (WHO), rabies occurs in more than 150 countries, and more than 55,000 people die of rabies every year—95 percent of them from Asia and Africa.

“Rabies, is a viral disease in mammals caused by the Lyssavirus of the genus Rhabdoviridae. This virus primarily affects the nervous system of the affected organism or animal thus literature often describes it as neurotropic,” says Vincent Rasalan, M.D., a resident training in surgery at the James L. Gordon Memorial Hospital and the president of the James L. Gordon Memorial Hospital Residents' Organization. “It follows the path from the peripheral nerves to the central nervous system, ultimately the brain, causing a condition known as encephalitis … This explains the neurologic symptoms in affected patients.”

Camille Macalalag-Sta. Cruz, M.D., Emergency Medicine Resident Physician with the Makati Medical Center, citing the comprehensive emergency medicine study guide Tintinalli's Emergency Medicine, affirms, “Rabies virus causes acute encephalitis [brain infection] and the outcome is almost always fatal.”

A ticking time bomb

Rabies affects domestic and wild animals, and spreads to people through close contact with infected saliva via bites or scratches, according to the WHO. Clinical rabies in humans, says Dr. Macalalag-Sta. Cruz, “comes in five stages: incubation period, prodrome, acute neurologic phase, coma then death or for some lucky souls ... recovery.”

“Incubation period after an exposure takes between 20 to 90 days and there are no common symptoms or signs during this time,” she warns.

During the prodrome stage, which may last from two to 10 days, pain or numbness at the site of the bite, flu-like symptoms like fever, malaise, lethargy, headache, nausea, vomiting and loss of appetite may manifest. Though, “not every symptom or sign may be present in each case!” she clarifies.

Early symptoms of rabies “are rather non-specific, in fact, mimicking the common flu. Here we have fever, headache, body malaise or that conspicuous feeling of being easily tired, generalized discomfort,” echoes Dr. Rasalan. The earliest neurologic discomforts an infected individual can feel would be numbness, discomfort or pain at the site of bite and its surrounding area. “The only salient feature that can differentiate rabies from other viral infections is the history of animal bite—which may include, dogs, cats, rodents and bats,” he adds.

“During the neurologic phase, symptoms would include anxiety, agitation, depression, confusion, delirium, hallucinations, hyperventilation, numbness, weakness, paralysis, [and] hydrophobia” or fear of water, enumerates Dr. Macalalag-Sta. Cruz. These symptoms can last from two to seven days.

Dr. Rasalan explains, “This correlates to the viral load of the human body and its progression towards the central nervous system. Late symptoms include hypersalivation and agitation. The patient then begins to hallucinate and manifest with exaggerated response to their environment. Eventually they begin to fear even water and light.”

Coma may ensue after and may last from hours to 14 days. Death, which may be due to complications in the lungs and secondary infections, usually follows.

Diffusing a catastrophe

Both doctors stress the importance of bringing a bite victim immediately to the nearest health facility for proper assessment and management, underscoring that it may be too late if the victim seeks medical help once symptoms start showing. “Once symptoms are manifested, the outcome is 99.99 percent of the time fatal,” warns Dr. Rasalan. “Don't take chances. Even suspected bites … should be [looked at by] physicians,” he counsels.

After an animal bite, post-exposure prophylaxis through vaccination is the usual course of management. The WHO Department of Communicable Disease Surveillance and Response has come up with categories of rabies exposure and corresponding management.

Anti-rabies vaccines and their administration

There are two rabies biologicals available, says Dr. Macalalag-Sta.Cruz—the rabies vaccine and the rabies immunoglobulin (RIG). “The rabies vaccine facilitates active immunity by stimulating the body to actively produce antibodies against rabies … RIG, on the other hand, facilitates passive immunity. It already contains the antibodies needed to combat rabies hence once given, the antibodies inactivate the rabies virus immediately.”

After receiving the vaccine, the body may take several days to produce enough antibodies to combat the virus. That’s why multiple administrations are necessary. The rabies vaccine is administered either intramuscularly or intradermally. In the Philippines, the intradermal schedule followed is one dose of 0.1 ml of PVRV given on each deltoid on Days 0, 3, 7 and 28 or 30 or the intramuscular regimen of 0.5 ml PVRV on the deltoid on Days 0, 3, 7, 14 and 28/30. RIG is administered on Day 0 in Category III exposures. The intradermal regimen “is less costly and has been adapted in the Philippines since 1997,” shares Dr. Rasalan.

There are many myths regarding rabies and its treatment. Grab a copy of the March issue of HealthToday from your favorite bookstore or newsstand to find out more about this dangerous infection.

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