Rabies

Rabies is nearly always fatal once symptoms appear, and nearly always preventable if you act before they do. The whole game is the bite: wash the wound hard, get immunoglobulin and vaccine started, and do not wait for confirmation. Dogs cause up to 99% of human rabies deaths worldwide. The virus tracks the central nervous system to the brain, and once it gets there, supportive care is all you have.

What Is Rabies?

Rabies is a fatal but preventable viral disease that primarily affects the central nervous system (CNS). The name comes from the Latin for "to rage." Pasteur's 19th-century vaccine, given after inoculation, was the first thing to interrupt a uniformly fatal disease. It spreads to people and pets through the bite or scratch of a rabid animal, and without prompt care after exposure the virus reaches the brain and kills.

Pathophysiology

The course is best characterized in canine rabies variants.

An animal is bitten by a rabid animal, and rabies virus from infected saliva enters the wound. The virus travels through the nerves to the spinal cord and brain over roughly 3 to 12 weeks, during which the animal shows no signs. Once it reaches the brain, the virus multiplies rapidly and moves to the salivary glands as the animal starts showing disease. The infected animal usually dies within 7 days of becoming sick.

Etiology

Rabies is caused by a neurotropic virus of the family Rhabdoviridae, genus Lyssavirus, subgroup rabies virus.

Transmission is usually via saliva contaminating bites, scratches, and wounds, and more recently via mucosal exposure. The highest-risk animals for humans are canines (dogs, foxes, coyotes), cats, raccoons, and bats. With bats, a sleeping person may not notice the exposure, so postexposure prophylaxis (PEP) is recommended whenever a bat is found in the room of a sleeping or incapacitated person.

Statistics and Incidences

Each year, rabies causes approximately 59,000 deaths worldwide.

Dog rabies remains common in many countries, accounting for over 90% of human exposures and 99% of human rabies deaths worldwide. The highest annual death toll was recorded in the first half of the 20th century, averaging 50 documented cases per year. Encounters with rabid vectors may be higher in males, consistent with dog-bite data showing more bites in males than females. From 1960 to 2018, 125 human rabies cases were reported in the United States, roughly a quarter from dog bites during international travel. Of infections acquired within the United States, 70% were attributed to bats.

Clinical Manifestations

After exposure, the virus has to travel to the brain before it causes symptoms. This incubation period can last weeks to months.

Early symptoms mimic the flu: general weakness or discomfort, fever, or headache, lasting for days. Hydrophobia and aerophobia are pathognomonic and occur in 50% of patients; attempting to drink or having air blown in the face triggers severe laryngeal or diaphragmatic spasm and a sense of asphyxia, likely a violent airway-irritant response, and even the suggestion of drinking may induce a hydrophobic spasm. As the disease progresses, patients develop delirium, abnormal behavior, hallucinations, insomnia, anxiety, confusion, and agitation.

Assessment and Diagnostic Findings

In animals, rabies is diagnosed with the direct fluorescent antibody (DFA) test, which detects rabies virus antigens in brain tissue. In humans, several tests are required.

The dFA test relies on rabies virus antigen present in the tissues of infected animals; because rabies lives in nervous tissue rather than blood, brain is the ideal tissue to test. Histologic examination of biopsy or autopsy tissue occasionally helps diagnose unsuspected cases not caught by routine methods. Immunohistochemistry detects rabies in formalin-fixed tissue and is more sensitive than histologic stains such as H&E and Sellers, using specific antibodies to detect viral inclusions much like the dFA test. Electron microscopy shows the bullet-shaped Rhabdovirus particles and their inclusions in detail. For amplification, mouse neuroblastoma (MNA) and baby hamster kidney (BHK) cells grow the virus without animals, and biochemical methods amplify its nucleic acid.

Medical Management

Inpatient care is needed when wounds are extensive or on the face and hands, when surgical repair or blood replacement is required, or when infection develops.

Preexposure prophylaxis (active immunization) is recommended for veterinarians, veterinary students, regular cave explorers, lab workers exposed to the virus or high-risk specimens, and travelers to countries where rabies is a significant problem (visits longer than 30 days). For an animal bite, wash and debride the wound at the time of injury and clean it for longer than 10 minutes, generally leaving wounds to heal by secondary intention. Before symptoms start, optimal postexposure prophylaxis means immediate vigorous wound cleansing, passive immunization with immunoglobulin, and active immunization with rabies vaccine. After symptoms appear, intensive cardiopulmonary supportive care is the only treatment available.

Pharmacologic Management

Before symptom onset, passive and active immunization can prevent progression to full rabies.

Rabies immunoglobulin is recommended as part of the postexposure regimen for persons not previously immunized. Rabies vaccines induce an active immune response; two types exist, cell-cultured vaccines and nerve tissue vaccines.

Nursing Management

Nursing Assessment

History. In any suspected exposure, identify the nature of the interaction with the animal (remember that "provocation" does not lower rabies risk, since humans may not grasp what a wild animal finds provocative), any strange behavior such as a nocturnal animal out during the day, the animal's rabies vaccination status, and whether the animal is available for testing.

Physical exam. With furious rabies, expect episodic delirium, psychosis, restlessness, thrashing, muscular fasciculations, seizures, aphasia, and autonomic instability.

Nursing Diagnosis

Based on assessment, the major diagnoses are: Ineffective breathing pattern related to asphyxia; Imbalanced Nutrition: less than body requirements related to decreased swallowing reflexes; Hyperthermia related to viremia; Anxiety of the family related to exposure to information; Risk for injury related to seizures and weakness; and Risk for infection related to open wounds.

Nursing Care Planning and Goals

The patient improves breathing pattern, takes adequate calories and nutrients, maintains body temperature below 39° C (102.2° F), identifies strategies to reduce anxiety, and stays free of injury and infection.

Nursing Interventions

Improve breathing. Position the patient for maximum breathing, keep the airway clear by encouraging effective coughing to mobilize secretions, suction as needed, and pace activity with frequent rest.

Improve nutrition. Provide a pleasant environment, proper positioning, and good oral hygiene. Offer six small nutrient-dense meals instead of three larger ones daily to ease fullness. For impaired swallowing, coordinate with speech therapy, and offer the highest-calorie meal when appetite peaks.

Maintain temperature. Adjust room temperature and bed linens, remove excess clothing and covers, and give antipyretics as prescribed.

Reduce anxiety. Use presence, touch with permission, verbalization, and a calm demeanor to remind patients they are not alone and to encourage them to voice needs and questions. Interact peacefully, accept the patient's defenses, do not argue or debate, use simple language and brief statements, and explain all activities and procedures in nonmedical terms with calm, slow speech.

Prevent injury. Avoid restraints, and obtain a physician's order if they are needed. For new-onset confusion or delirium, provide reality orientation. Ask family or significant others to stay to prevent falls, remove hazards such as razors, medications, and matches, and place an injury-prone patient near the nurses' station.

Prevent infection. Maintain and teach aseptic technique for dressing changes and wound care, wash hands and teach the patient and significant other to wash hands before contact and between procedures, teach the purpose and technique for isolation, and if infection occurs, teach the patient to take antibiotics as prescribed.

Evaluation

Goals are met when the patient improves breathing pattern, takes adequate nutrition, maintains body temperature below 39° C (102.2° F), identifies anxiety-reduction strategies, and stays free of injury and infection.

Documentation Guidelines

Document individual findings and behaviors, cultural and religious beliefs and expectations, the plan of care, the teaching plan, responses to interventions and teaching, and progress toward outcomes.

Key Points

Rabies affects the central nervous system and spreads through the bite or scratch of a rabid animal, usually via saliva contaminating bites, scratches, and wounds, and recently via mucosal exposure. It causes approximately 59,000 deaths worldwide each year. First symptoms mimic the flu and last for days; hydrophobia and aerophobia are pathognomonic and occur in 50% of patients. Diagnosis in animals uses the DFA test on brain tissue. Wash and debride the bite and clean it for longer than 10 minutes. After symptoms appear, intensive cardiopulmonary support is the only treatment. Rabies immunoglobulin is part of the postexposure regimen for those not previously immunized.