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Siberian tick-borne typhus

Siberian spotted tick fever /other names – tick-borne rickettsiosis, North Asian tick-borne typhus, Eastern tick-borne typhus, eastern spotted typhus/ is an acute benign endemic rickettsiosis, spread only by ticks and characterized by the presence of a primary affect, febrile reaction, with a spotted-nodular rash on the skin, with an increase and tenderness of the regional lymph nodes.

The disease was first described in 1936. Its origin, epidemiology and clinic were studied in detail in 1938, in the same year its causative agent was also isolated from necrotic skin cells of a sick person after being bitten by an ixid tick.

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Epidemiology and etiology

The causative agent of tick-borne rickettsiosis is similar to that of other rickettsioses and multiplies in the affected cells.

In natural outbreaks of the disease, the circulation of Rickettsia siberica takes place between wild mammals and ixid ticks – the main and natural carriers of these bacteria.

Human infection with tick-borne typhus occurs in natural outbreaks through the bite of infected ticks whose saliva contains rickettsiae.

Tick-borne spotted typhus is a seasonal disease. Maximum morbidity is observed in late spring /from the beginning of May/ and the beginning of summer, which is determined by the period of greatest activity of ticks.

In autumn, a second rise in morbidity is possible, which is determined by the second generation of arthropods. Single cases of the disease are registered mainly among workers in agriculture.

The area of ​​distribution of Siberian tick-borne typhus is the whole of North Asia.

Pathogenesis and pathoanatomy

At the site of the entrance door of the infection, a primary affect occurs – an inflammatory reaction of the skin with regional lymphadenitis. The causative agent Rickettsia siberica penetrates the endothelium of small blood vessels, causing inflammatory changes.

At the same time, proliferative processes prevail over destructive ones with the development of mono- and perivaxulitis, which also explains the milder course of the disease compared to epidemic typhus.

Rickettsemia and toxinemia in tick-borne rickettsiosis cause the symptoms of intoxication of the body.

Clinical picture

The incubation period lasts 4-7 days. The disease begins acutely – chills appear, the body temperature quickly rises to 39-40 degrees Celsius.

Prodromal phenomena, that is, preceding and early symptoms, such as malaise, headache and muscle pain, loss of appetite, are less frequently observed. Redness of the face, neck, throat mucosa, and also a rash on the oral mucosa are often noticed.

Toward the end of the incubation period, at the site of the tick bite on the exposed parts of the body – the scalp, neck and shoulder girdle, a primary effect occurs, which is a thickening of the skin, slightly painful on palpation.

A dark brown necrotic crust is formed in its center, and a red line is formed on the periphery, which is the result of developed hyperemia. The inflammatory thickening reaches 1-2 cm in diameter.

Fever is remittent, less often constant, lasts 8-10 days, sometimes 20 and subsides gradually. Depending on the intensity of the symptoms of intoxication, mild, medium and severe forms of tick-borne rickettsiosis are distinguished.

Main in the clinical picture of the disease are the symptoms of involvement of the nervous system. They are expressed in a persistent, sometimes excruciating headache, pain in the muscles and in the lower back area.

Treatment of Siberian tick-borne typhus

Etiotropic therapy is successfully carried out with antibiotics of the tetracycline group in hospital settings. Along with the antibacterial agents, measures are also taken to control the symptoms. Prevention is protection against tick bites.

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