bubble_chart Overview

Rabies, also known as hydrophobia, is an acute infectious disease of the central nervous system caused by the rabies virus. The disease is characterized mainly by agitation, fear of water and wind, pharyngeal muscle spasms, progressive paralysis, and ultimately death. The primary hosts of the infection are wild animals such as wolves and foxes, but humans and domestic animals (dogs, cats) can also be infected. Humans primarily contract the disease through saliva transmission from bites by rabid dogs.

bubble_chart Clinical Manifestations

The incubation period is generally 1 to 3 months, ranging from as short as 10 days to as long as over 1 year, with some cases lasting up to 19 years.

1. Prodromal phase: 2 to 4 days. Manifestations include:
   1. Local symptoms: Numbness, cutaneous pruritus, pain, or abnormal sensations such as ants crawling on limbs near the healed wound site.
   2. Systemic symptoms: Low-grade fever, lack of strength, headache, nausea, dysphoria, fear and unease, throat tightness, and heightened sensitivity to sound, light, and wind stimuli.
2. Excitement phase: 1 to 3 days. Symptoms include:
   1. Extreme excitement, irritability, intense terror, hydrophobia, fear of wind and sound, and possible delirium or mental disturbances.
   2. Paroxysmal pharyngeal muscle spasms and difficulty breathing. Thirst but fear of drinking, or drinking but fear of swallowing—even mentioning water or hearing the sound of water from a river can trigger pharyngeal spasms. Wind, light, or sound stimuli may also induce pharyngeal spasms, and in severe cases, generalized painful spasms and respiratory muscle spasms worsen breathing difficulties.
   3. Sympathetic hyperactivity, often presenting as profuse sweating, increased salivation, elevated blood pressure, and tachycardia.
3. Paralysis phase: 6 to 18 hours. The patient's spasms cease, replaced by generalized calm and paralysis, especially flaccid paralysis of the limbs, which progressively worsens until unconsciousness ensues, followed by respiratory and circulatory failure leading to death. The entire course does not exceed 6 days.

Atypical cases may lack the excitement phase and hydrophobia, instead presenting with high fever, headache, vomiting, and pain at the bite site, followed by limb weakness progressing to paralysis, termed "dumb rabies." For suspected cases, a fan test can be performed: fanning air at the patient's face. If neck and pharyngeal spasms occur, it indicates a positive "aerophobia" sign, which aids diagnosis.

bubble_chart Auxiliary Examination

1. General Laboratory Tests
   1. The total white blood cell count is mildly to moderately elevated (grade II), with neutrophils accounting for over 80%.
   2. Cerebrospinal fluid pressure is slightly increased, with a mild elevation in cell count and protein levels.
2. Immunological Tests
   1. Serological Tests: (a) Paired serum neutralization antibody comparison test: For individuals not vaccinated against rabies, a fourfold or greater increase in antibody titer confirms the diagnosis. For vaccinated individuals, an absolute neutralization antibody titer of 1:5000 or higher is diagnostic. (b) Dot immunobinding assay: This method uses inactivated viral antigen to detect rabies virus-neutralizing antibodies in serum, offering high specificity and sensitivity, and is simple to perform.
   2. Detection of viral antigen in brain tissue and saliva: Immunofluorescence can yield results within hours. Viral antigen can also be detected using enzyme-linked immunosorbent assay (ELISA), which has diagnostic value for ante-mortem diagnosis.
3. Virus Isolation: Saliva or post-mortem brain tissue can be inoculated intracranially into mice for virus isolation.
4. Negri body examination: Touch smears from the brain tissue of deceased individuals or biting animals, stained using Seller's method, can reveal Negri bodies in the cytoplasm. These are eosinophilic inclusions representing viral colonies and have specific diagnostic value.

bubble_chart Diagnosis

History of being bitten or scratched by a rabid dog.

bubble_chart Treatment Measures

There is currently no specific treatment for this disease, and the fatality rate is extremely high. Active emergency measures are essential for survival; otherwise, the mortality rate is 100%.

1. Isolate the patient in a single room, maintain a quiet environment, and avoid all stimuli such as sound and light.
2. Monitor and maintain respiratory and circulatory functions. A tracheotomy may be performed, and a ventilator with positive-pressure oxygen can be used.
3. Administer sedatives and muscle relaxants. For patients with cerebral edema, provide dehydrating agents.
4. Maintain nutrition and water-electrolyte balance through a combination of nasogastric feeding and intravenous fluids.
5. Some suggest intrathecal injection of Belamcanda Rhizome interferon, which may be attempted.

Preventive Treatment

1. Wound Management
   1. Thoroughly clean the wound to remove any existing virus. The following can be used: (1) 20% soapy water; (2) 0.1% benzalkonium bromide; (3) 1–2% benzalkonium chloride; (4) 1% hexadecyltrimethylammonium bromide. The cleaning process should last half an hour. Note that soapy water should not be used in combination with the latter two solutions, as it may neutralize their effects. After rinsing with soapy water, the wound must be thoroughly washed with clean water before applying the latter two solutions.
   2. After cleaning, apply 70–75% alcohol or 3% iodine tincture to the wound. Do not bandage or suture the wound.
   3. If conditions permit, inject high-potency serum into the base and surrounding areas of the wound. For deep or dirty wounds, tetanus antitoxin and appropriate antibiotics may also be administered.
2. Rabies Vaccine Injection
   1. Hamster kidney vaccine has fewer side effects and good efficacy. (1) Grade I bite: Administer 2ml intramuscularly on the day of injury, and on the 7th and 14th days. (2) Grade III bite: Administer 2ml intramuscularly on the day of injury, and on the 7th, 14th, and 30th days.
   2. Human diploid cell vaccine: Prepared by inoculating human embryonic lung fibroblasts with the virus. There are two administration methods: (1) Intramuscular injection of 1ml on the day of injury, and on the 3rd, 7th, 14th, 30th, and 90th days (recommended by the World Health Organization); (2) Intramuscular injection of 1ml on the day of injury, and on the 7th, 14th, and 21st days (as per the U.S. Centers for Disease Control and Prevention protocol). (3) Duck embryo vaccine: Prepared by inactivating the virus cultured in duck embryos. Administer 1ml subcutaneously daily for 14–21 days after injury, followed by booster injections on the 10th, 20th, and 90th days after completing the full course. Antibodies develop by the 10th day post-vaccination. Side effects may include nausea, fever, chills, headache, myalgia, and lymphadenopathy, with occasional reports of rash, angioneurotic edema, or anaphylactic shock.
   3. Inactivated sheep brain tissue vaccine: This has been phased out internationally but is still used in some regions domestically. It has some efficacy. The administration method and course are the same as for the duck embryo vaccine, but the dose is doubled. Due to its content of brain tissue and myelin, it may cause more neurological complications.
3. Immune Serum: For severe bites or cases with a short incubation period, it is best to combine treatment with immune serum.
   1. Equine anti-rabies serum: After a negative skin test, calculate the dose at 40IU/kg or 0.5ml/kg. Half of the total dose should be injected locally around the wound, and the other half intramuscularly. Equine serum may cause anaphylactic shock, so emergency preparations should be made before injection.
   2. Human anti-rabies immunoglobulin: Administer half the dose of equine serum, i.e., 20IU, via intramuscular injection. A booster dose of the vaccine must be given 10–20 and 90 days after completing the vaccination course to trigger a recall response and produce a higher level of corresponding antibodies.
4. Interferon Inducers: Some recommend combining the vaccine with interferon inducers (such as Polyl:C or Polyl:C-lysine complex) for better efficacy.