Rabies is an acute infectious disease of the central nervous system to which all warm-blooded animals and man are susceptible. The virus, frequently present in the saliva of an infected host, is usually transmitted by bites, by licks, and occasionally by the respiratory route. The disease is characterized by a profound dysfunction of the central nervous system and ends almost invariably in death.
Etiology of Rabies
Epizootics of rabies occur in any climate during any season of the year, Wars and mass movements of men and animals favor the geographic spread of the disease. Man becomes an accidental host upon exposure to the infected saliva of the biting animal, and wild animals are often sources of human rabies. The attack rate in man, after exposure, depends to a certain extent on the location and on the severity of the inflicted wounds. Head and neck bites lead to a higher incidence of infection than bites on other parts of the body. The bites of rabid wolves are apparently very dangerous; an attack rate of 47 per cent was observed in 32 persons who were bitten by the same animal and did not receive anti-rabies treatment in time to be of any protective value.
Rabies Clinical Manifestation
In the paralytic type of rabies, the excitation phase may be slight or totally-absent, and the disease is charac- terized only by the paralytic syndrome. Paralysis of the lower jaw, accompanied by excessive salivation, appears as an early symptom, and the animal acts as though it were choking on a foreign body. Paralysis of the muscles of phonation may lead to loss of the bark. As the disease progresses, paralysis of the posterior extremities sets in, followed by general paralysis and death. The time from the onset of the disease to the death of the animal ranges from one to eleven days. On the other hand, dogs may die suddenly without noticeable signs of illness. Man. In man, the prodromal phase is marked by fever, anorexia, headache, malaise, nausea, and sore throat.
Abnormal sensations around the site o/ infection, such as intermittent pain, tingling, or burning, are of diagnostic significance. Extreme stimulation of the general sensory system is manifested by hyperesthesia of the skin to temperature changes and to drafts, and by acute sensitiveness to sound and light. Other symptoms include increased musculartonus, prompt gag and corneal reflexes, dilation of pupils, and increased salivation.
In rabies in man resulting from vampire bat infection, the excitation phase is almost totally absent, and the disease is characterized by ascending paralysis without hydrophobia. Without an adequate history of exposure, clinical diagnosis of this type of infection may be dif- ficult,
Diagnosis of Rabies
Profound dysfunction of the central ner- vous system, accompanied by impairment in deglutition, in persons who either were exposed to a bite or lick of any animal or may have recently visited caves harboring bats, facilitates the clinical diagnosis. Isolation of virus from saliva obtained in the course of the disease and from brain tissue obtained at autopsy, followed by proper identification of the agent by means of neutralization test, willeonfirm the diagnosis. Syrian hamsters, rabbits, guinea pigs, and, preferably, suckling mice are used for diagnostic purposes.
Demonstration of rabies virus antigen in smears of brain tissue obtained from ei- ther patient or animal (preferably brainstem, cerebel- lum, or Ammon’s horn) by means of specific staining with antibody coupled with fluorescein isothiocyanate is of diagnostic significance. The presence of intracytoplasmic inclusion bodies in the neuron (Negri bodies) is pathognomonic, but their absence does not exclude the diagnosis of rabies, as the presence of virus may be dem- onstrated by other means.
Prognosis of Rabies
Although inapparent infection with street virus may be induced artificially in laboratory animals, and although animals have recovered completely after exhibiting signs of the disease, there is only one case reported of the recovery of a human from rabies after showing unmistakable signs of disease. In all other reported cases, the disease proved fatal to humans.
Confinement and observation of the biting animal, preferably under the supervision or a veterinarian, for a period of not less than ten days for dogs and cats, is one of the most important steps in deciding whether an individual has been exposed to rabies. Biting wild animals should be sacrificed and their brain tissue examined properly by im- munofluorescent staining. Treatment of severely ex- posed persons should be started without awaiting results of the laboratory diagnosis. If the absence of rabies infection in the biting animal is reported, treatment may be stopped.
Local Treatment of Wounds.
Since the most effective available mechanism of protection against rabies is the elimination of the virus at the site of infection, all bite wounds, as well as scratches and other abrasions exposed to licks of animals, should be treated immediately by thorough cleansing and adequate mechanical flushing of the wound with soap solution followed by treatment with substances such as 40 to 70 per cent alcohol, tincture or aqueous solutions of iodine, or 0.1 per cent quaternary ammonium compounds, which are lethal to rabies virus.
If debridement is necessary, infiltration with local anesthetics is not contraindicated. Bite wounds should not be sutured immediately. After determination of sensitivity to anti-rabies serum, the serum should be used in local application upon the wound. Preliminary application of antimicrobial drugs is of no value as a prophylactic measure. However, antitetanus treatment and local application of antiseptics and an- timicrobials should be instituted if indicated.
Treatment Once Clinical Signs Are Apparent.
Although no specific therapeutic measures are available to save the life of a person exhibiting symptoms of the disease, the survival of one patient with human rabies indicates that all the tools of modern medicine should be used in the attempt to save the patient’s life.
These there therapeutic measures should consist of 1 starting treatment immediately after signs of rabies appear; (’21 placing the patient in the intensive medical care unit in a quiet environrnent, with constant monitoring to prevent cardiac failure; (3) using sedatives for the relief of anxiety and pain; (4) performing a tracheostomy and applying at’, artificial breathing to maintain respiratory function; (5) using curare-like drugs to alleviate spastic muscular contractions if they occur; and (6) instituting intravenous per-fusions and administering diuretics to assure proper hydration and diuresis. Since rabies virus may be present in the saliva of the patient exhibiting signs of the disease, all attending personnel should be protected against contamination through the use of goggles, masks, and rubber gloves.