Rabies (hydrophobia) - Diagnosis

Intravital diagnostics of rabies consists of determining the viral antigen in the first days of the disease using the fluorescent antibody method in corneal imprints or in occipital skin biopsies, as well as determining antibodies after the 7th to 10th day of the disease. In unvaccinated patients, the diagnosis of rabies is confirmed by a fourfold increase in the antibody titer when examining paired sera. In vaccinated patients, the diagnosis is based on the absolute level of neutralizing antibodies in the serum, as well as the presence of these antibodies in the cerebrospinal fluid. After post-exposure prophylaxis, neutralizing antibodies in the cerebrospinal fluid are usually absent or their titer is low (less than 1:64), while in rabies, the titer of neutralizing antibodies in the cerebrospinal fluid ranges from 1:200 to 1:160,000. For diagnostic purposes, PCR is also used to detect rabies virus RNA in brain biopsy.

Postmortem diagnostics of rabies is carried out by several methods. The histological method is widely used - an express method, in which the answer can be obtained in 1-2 hours with a reliability of 85-90%, it is based on the detection of Babesh-Negri bodies in smears-prints of the brain. Babesh-Negri bodies when the preparation is treated with acidic dyes acquire a ruby color with a basophilic internal structure. Biological diagnostics of rabies is based on infecting laboratory animals (sucklings of white mice, Syrian hamsters) with the test material and detecting Babesh-Negri bodies in the brain tissue after the death of the animals; the answer can be obtained in 25-30 days. Immunological methods are also used - the method of fluorescent antibodies or ELISA, as well as the virological method based on the isolation and identification of the rabies virus.

For postmortem laboratory testing in humans, pieces of brain tissue (2-3 g of cerebellar tissue, Ammon's horn, cerebral cortex), salivary glands, cornea are used, which are placed in a sterile container with a 50% glycerol solution in physiological saline. The material must be collected under strict anti-epidemic conditions and personal preventive measures, and delivered to the laboratory in a hermetically sealed form, in a cooler bag. The head is most often sent as material for laboratory testing in animals, and if the animal is small, then the entire corpse. The material is placed in polyethylene bags, then in hermetically sealed containers with pieces of ice.

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Indications for consultation with other specialists

A consultation with a surgeon is indicated in the presence of multiple lacerated and suppurating wounds, and a neurologist - in the presence of clinical and laboratory symptoms of encephalitis of a different nature.

Indications for hospitalization

List of indications for hospitalization of victims of bites, scratches and drooling by animals and patients with hydrophobia:

• surgical indications (multiple lacerations, bites to the face, neck, hands and fingers);
• burdened medical history;
• infected bite wounds (except the hand);
• infected bite wounds of the hand;
• aggravated allergic history, individuals with unusual post-vaccination reactions and complications to anti-rabies drugs and those re-vaccinated;
• burdened neurological history;
• aggravated psychoneurological history;
• Pregnant women who have suffered from animal bites:
• newborns who have suffered from animal bites;
• patients with hydrophobia and victims of bites from infected animals.

Differential diagnostics of rabies (hydrophobia)

Differential diagnosis of rabies is carried out with diseases accompanied by the development of similar clinical symptoms.

Differential diagnosis of rabies

Sign	Rabies	Atropine poisoning	Tetanus	Lyssophobia
Incubation period	From 7 days to 1 year or more (usually 30-90 days)	2-4 hours	1-30 days	No
Onset of the disease	Gradual	Spicy	Acute, subacute	Spicy
Weakness, fatigue	Characteristic	Characteristic	Characteristic	Eat
Fever	Characteristic	Not typical	Characteristic	Not typical
Sweating	Eat	Eat	Eat	No
Headache	Eat	Eat	No	Eat
Salivation	Expressed. Dry mouth in the paralysis stage	Dry mouth and throat	Eat	No
Mental changes	Constant	Eat	No	Eat
General excitability	Eat	Eat	Eat	Eat
Speech and swallowing disorder	Eat	Eat	Eat	No
Mydriasis	Eat	Eat	No	No
Psychomotor agitation	Eat	Eat	No	No
Hallucinations	Eat	Eat	No	No
Cramps	Eat	Eat	Yes, against the background of muscle hypertonicity	No
Relaxing muscles after cramps	Eat	Eat	No	No cramps
Spasms of the muscles of the pharynx. Trismus.	Periodic	No	Constant	No
Loss of consciousness	Eat	Eat	Yes (before death)	No
Hydrophobia	Eat	No	No	No
Paralysis, paresis	Eat	No	No	No
Steady progression of the disease	Yes	No	No	No
Hemogram	Leukopenia, aneosinophilia	Not changed	There are no characteristic changes.	Not changed
CSF	Lymphocytic pleocytosis. slight increase in protein	Not changed	As a rule, it is not changed	Not changed

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