Tick-borne Typhus

2024 Author: Josephine Shorter | [email protected]. Last modified: 2023-12-16 21:43

Description of the disease

Typhus is a disease of an infectious origin from a variety of rickettsioses caused by tick bites, characterized by a relatively mild course with damage mainly to the lymph nodes and skin rashes. Other names of the disease that are found in medical practice and everyday life can be: tick-borne rickettsiosis, Siberian tick-borne typhus, eastern typhus.

The disease belongs to typical zoonoses, because the circulation of the pathogen and the incidence is recorded only among small rodents in natural conditions. These can be gophers, hamsters, field mice, chipmunks, voles. A person enters this natural circle by accident after a tick bite. Therefore, tick-borne typhus belongs to diseases with natural focus and is tied to certain territories where pathogens are constantly circulating. These are some regions of Siberia, Krasnoyarsk, Khabarovsk, Primorsky Krai, Turkmenistan, Armenia, Kazakhstan, Mongolia.

Ixodid ticks are carriers of infection between healthy and sick animals. The prevalence of the disease in natural conditions is so wide that every fifth representative of ticks is infected. This explains the relatively high incidence of tick-borne typhus among people living in pandemic areas. It averages 200-300 cases per 100 thousand population per year. A significant number of residents have persistent natural immunity, therefore, mainly visitors and people with weakened immunity are sick.

The pathogenesis of the disease is determined by the pathogenic properties of rickettsia. They enter the human body through a skin wound that remains after a tick bite. This place is called the primary affect, since the first inflammatory changes occur here when tissues come into contact with pathogens. In this case, pathogens spread through the lymphatic pathways into the collectors of regional lymph nodes. The result of such processes can be lymphangitis next to the primary affect, and an increase in lymph nodes. In them, reproduction of rickettsia occurs with a regular release into the systemic circulation and spread throughout the body.

The peculiarity of infectious agents in tick-borne typhus is in maintaining a tropism to the vascular endothelium, as in epidemic typhus, but with significantly less pathogenic and toxigenic properties. The main pathogenetic links of the disease are microcirculatory disorders as a result of capillary damage, inflammation in them and increased permeability, as well as minor intoxication that occurs when pathogens are destroyed by the body's immune cells. Therefore, their distribution in the body proceeds relatively favorably and never causes serious complications.

Tick-borne typhus symptoms

The incubation period of pathogens of tick-borne typhus, which lasts from the moment of a tick bite to the appearance of the first manifestations of the disease, ranges from 3-4 days to a week. At this time, except for a slight inflammation of the skin at the site of the bite, nothing else bothers the patients. The clinical picture develops suddenly and rather sharply.

In this case, the following symptoms of typhus appear:

Hyperthermic reaction. In most cases, the temperature is hectic (39% C or more), constant or intermittent. The duration of the febrile period can be up to two weeks, if the patient is not treated. A few days after the appearance of the figure, the temperatures decrease slightly, it becomes constant;
Light chills with muscle and headaches. They arise synchronously with hyperthermia and decrease with its decrease;
Moderate puffiness of the face against the background of its hyperemia;
Infiltrative and inflammatory changes in soft tissues in the tick bite zone are the primary affect. It should never be after a tick bite that is not infected with pathogenic rickettsia. The bite site itself turns into a small ulcer under a black scab, and around it there is a 2-3-mm strip of skin hyperemia;
Hyperemia of the conjunctiva and mucous membrane of the oropharynx with enhanced and congestive vascular pattern;
Skin rash. It is represented by a true polymorphism of primary elements: roseola, small papules, spots, up to several millimeters in diameter. Their appearance is noted 4-5 days after the onset of temperature. Constant pouring of new elements is characteristic. Hemorrhagic rash is uncommon. The first rashes appear on the skin of the limbs, from where they spread to other areas;
Swollen lymph nodes, primarily regional in relation to the site of the bite;
Tachycardia or bradycardia. Arrhythmias are rare. Blood pressure may decrease slightly;
Symptoms of damage to the nervous system: lethargy, headache, apathy, sleep disturbances. Confusion and meningeal signs are extremely rare.

The causative agent of tick-borne typhus

Tick-borne typhus is caused by pathogenic microorganisms from the rickettsia group. Their specific species is Rickettsia sibirica. It has general properties that are common to all representatives of rickettsia. The only difference is moderate virulence. Therefore, its ingestion does not cause severe manifestations.

According to the morphological structure, Rickettsia sibirica is a gram-negative bacillus with an aerobic type of metabolism. The only natural reservoir for it is the rodent organism. Ixodid ticks act as a carrier of infection, which ensures its constant circulation in a certain area. This type of rickettsia is very stable in the external environment in relation to the action of high and low temperatures. Different strains can have different virulent and pathogenic properties, determining the clinical course of the disease.

In most cases, Rickettsia sibirica disease is timely verified by the body's immune cells. Its destruction does not cause the release of dangerous endotoxins. This allows the body to cope with the pathogen on its own, even if untreated. As a result, a stable immunity arises in the form of antibodies to the antigenic components of this type of rickettsia, which remains for life.

Prevention of tick-borne typhus

The following complex of non-specific preventive measures can help prevent tick-borne typhus:

Rodent control;
Prevention of tick bites while staying in foci pandemic for tick-borne typhus: the use of chemical repellents and essential oils, clothing should cover open parts of the body as much as possible, periodic examinations of the surface of clothing in order to detect and remove ticks;
Reception of tetracycline in therapeutic doses with the development of a primary affect at the site of a tick bite;

There is no specific prevention of tick-borne typhus.

Author of the article: Danilova Tatyana Vyacheslavovna | Infectionist

Education: in 2008 received a diploma in General Medicine (General Medicine) at the Pirogov Russian Research Medical University. Immediately passed an internship and received a diploma of a therapist

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