What Are the Symptoms of Rabies

1 Symptoms of Rabies

Epidemiology

The rabies virus can infect all mammals and birds. Rabid dogs are the main source of infection for people and livestock; wild animals, dogs and bats are the main reservoirs. Transmission is mainly through bites, with the virus entering the wound via saliva; it can also enter via the respiratory tract through virus-laden aerosols, or via the digestive tract if someone eats the meat of a sick animal or pets eat each other.

Clinical symptoms

The incubation period depends on the distance of the wound from the central nervous system and the virulence and amount of virus. Usually 20-60 days, as short as 8 days, or as long as months or over a year. Generally divided into furious and paralytic forms.

(1) Furious form

After a 1-2 day depressive period, the dog becomes disoriented, restless and drools; it may lie quietly or walk with tail tucked, then suddenly stop and bark, with markedly heightened reflex excitability and sensitivity to sound, bright light and touch, appearing frightened or jumping. Labored breathing, diaphragmatic spasm, dilated pupils. Anorexia, increased salivation, hind-limb paralysis. The excited phase lasts 2-4 days, escalating to mania with alternating excitement and depression, aggression toward people and animals, often running away from home, gradually losing consciousness and biting wildly. The terminal stage has a 1-2 day paralytic phase with drooling, protruded tongue, dropped jaw and hind-quarter paralysis; death usually comes from respiratory-center paralysis or failure. The whole course is 6-10 days.

(2) Paralytic form

The excited phase is very short (2-4 days) or unclear, then it enters the paralytic phase. Head muscle paralysis causes drooling, difficulty swallowing, mouth hanging open, and paralysis of the jaw, hindquarters and larynx; death in 2-4 days. Because some dogs have atypical courses, note any history of bites.

Pathological changes

The exterior usually shows no specific changes: emaciation, dehydration, rough coat, congested and eroded oral and gastrointestinal mucosa. Histology shows non-suppurative encephalitis with eosinophilic inclusions in nerve cell cytoplasm.

Differential diagnosis

(1) Rabies vs. pseudorabies

Both show restlessness, mania, drooling, biting objects and self-licking.

Difference: rabies causes confusion, jaw paralysis, hydrophobia and aggression toward people and animals; pseudorabies usually shows sudden death, intense itching and no aggression.

(2) Rabies vs. canine tetanus

Both show heightened reflex excitability to sound and light, neurological signs and a history of wound infection.

Difference: tetanus shows tonic spasms with limbs like a sawhorse and no hydrophobia. Rabies has a dog-bite history; tetanus follows wound infection.

(3) Rabies vs. canine meningitis

Both show restlessness, mania, depression, fear, biting when caught, sound sensitivity, barking and stupor.

Difference: meningitis is not contagious, with fever; neurological signs are mainly circling and convulsions, sometimes blind running without avoiding obstacles, sometimes vomiting.

(4) Rabies vs. organophosphate poisoning

Both show drooling, ataxia, labored breathing and convulsions.

Difference: rabies usually has a dog-bite history, is contagious and aggressive, with dropped jaw when drooling; organophosphate poisoning has exposure history, acute outbreaks or sudden onset, vomiting, abdominal pain, diarrhea and a garlic smell in GI contents.

(5) Rabies vs. sodium fluoroacetate poisoning

Both show aimless running, barking, rapid breathing and hiding in dark places.

Difference: rabies shows aggression, drooling, chewing wood, stones and other objects, with clear neurological signs in the paralytic phase; sodium fluoroacetate poisoning lacks the wood/stone chewing and causes rapid death.

(6) Rabies vs. canine lead poisoning

Both show restlessness, wandering blindly and barking.

Difference: lead poisoning follows ingestion of lead-containing paint or dye, with vomiting and diarrhea, and no bizarre-object chewing or aggression.

Notes

A preliminary diagnosis is based on the excited/restless state, drooling with open mouth, active aggression toward people and animals, and later ataxia, together with sporadic occurrence and a bite history; confirmation requires laboratory testing.

Prevention and control

1. Strengthen public-health management; resolutely catch and euthanize stray dogs and cats.

2. Manage working, household and companion dogs strictly; vaccinate all against rabies.

3. Euthanize rabid dogs and other affected animals promptly. For companion pets at risk, give emergency vaccination, second dose 3-5 days after the first. For high-risk cases, give hyperimmune serum 3 days after a bite at 0.5 mL/kg, then vaccinate.