Prevention of tick-borne encephalitis
Protection against tick-borne encephalitis virus involves several approaches. Specific routine prophylaxis is indicated for individuals living in endemic regions, as well as those planning trips there during the spring-summer period. Inactivated cell-culture vaccines are used for immunization.
If a person is not vaccinated, passive prophylaxis is possible before visiting a natural focus. Human immunoglobulin is administered 96 hours before entering the hazardous area. The protective effect develops within 24 hours and lasts for about four weeks, after which a booster may be required.
Emergency seroprophylaxis is performed after a tick attachment. It is indicated for unvaccinated patients or those who received the vaccination less than 10 days ago, provided that laboratory testing of the tick (PCR or ELISA) confirms the presence of the virus. The drug is administered intramuscularly strictly within the first 96 hours (4 days) after the bite.
Administration of immunoglobulin after the fourth day (during the incubation period, which lasts up to 28 days) is strictly prohibited. This is due to the risk of antibody-dependent enhancement (ADE) of the infection, which worsens the course of the disease. Because of this risk, the drug is not used in children under 14 years of age in some countries.
Nonspecific prophylaxis is also important, aimed at interrupting the alimentary transmission route: in endemic foci, only boiled milk is permitted for consumption.
Vaccination of patients with bleeding disorders
The presence of hemophilia or other blood coagulation disorders is not a reason to refuse immunization. Patients in this group can be vaccinated. Special priority is given to protection against viral hepatitis B.
The choice of the route of administration plays a key role:
- Preferred routes: oral and subcutaneous.
- Undesirable routes: intramuscular and intradermal.
If only the intramuscular route is available, the procedure requires rigorous preparation. To prevent post-vaccination hematoma formation, the patient is mandatorily prescribed replacement therapy. Important rule: therapy must be carried out strictly on the eve of immunization. Administering replacement drugs directly on the day of vaccination is not recommended.
An absolute contraindication to vaccination in such patients is the presence of active bleeding.
Biological research method (In vivo)
The biological method (bioassay) is based on the experimental infection of susceptible laboratory animals (mice, rats, guinea pigs, rabbits). The choice of a specific animal species depends on the biological characteristics of the pathogen being studied.
The method serves several crucial purposes:
- Isolation of the pathogen. This is the main advantage of the method, especially relevant for microorganisms that are unable to grow on artificial nutrient media.
- Assessment of pathogenicity. It allows for determining the degree of virulence of the microbe and the type of toxin it produces.
- Modeling of infection. It is used to reproduce the clinical picture of the disease, study pathogenesis, and examine microorganism-macroorganism interaction mechanisms.
- Immunology and pharmacology. The method is essential for studying the immune response and evaluating the activity of antimicrobial drugs and vaccines.
The material can be administered to animals via various routes: enteral (oral), respiratory (into the respiratory tract), and parenteral (intradermal, subcutaneous, intramuscular, intravenous, intraperitoneal). In special cases, administration into specific loci is used: into the anterior chamber of the eye, subdurally (via trepanation of the skull), or suboccipitally (into the cisterna magna).
To remember the timing for emergency prophylaxis of tick-borne encephalitis, use the "Rule of Fours": 4 days (96 hours) for administration, protection lasts 4 weeks, administration after the 4th day is prohibited.
Class and exam questions
Why is it forbidden to administer tick-borne encephalitis immunoglobulin on the 5th day after a bite?
Administration of antibodies during the incubation period (after the 4th day) can trigger antibody-dependent enhancement of the infection and significantly worsen the course of the disease.
How to safely administer an intramuscular vaccine to a patient with hemophilia?
Replacement therapy must be performed strictly on the eve of vaccination to prevent hematoma formation. Therapy is not administered on the day of the vaccination itself.
What is the main advantage of the biological research method?
It allows for the isolation and study of microorganisms that cannot be grown on artificial nutrient media.
What else to study on this topic
- Mechanism of antibody-dependent enhancement of infection in tick-borne encephalitis
- Types and composition of inactivated cell-culture vaccines
- Assessment of virulence and toxigenicity of microorganisms in vivo
- Modeling the infectious process in laboratory animals
- Replacement therapy regimens in hemophilia before invasive procedures
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