Lice relapsing fever

Louse relapsing fever /louse relapsing typhus, European, relapsing fever/ – an acute infectious disease caused by spirochetes. It is characterized by an acute onset, paroxysmal fever, general intoxication and enlargement of the liver and spleen.

Etiology

The causative agent of louse / European / relapsing typhus are the spirochetes Borrelia recurrentis Obermeieri. Other relapsing fevers transmitted by lice are also known, which are caused by other Borrelia species /B. Verbera, V. Carteri/.

The causative agent of European typhus has 4-6 whorls, is 10-20 microns in length, is motile, grows in nutrient medium and on developing chicken embryos, is pathogenic for monkeys, white mice and rats.

It is sensitive to penicillin, to antibiotics from the tetracycline group, chloramphenicol, erythromycin.

Epidemiology

The only source and reservoir of infection is the sick person. Body lice serve as vectors, which can transmit the infection 5 days after infection. Head and pubic lice are of little epidemiological importance. There is currently no relapsing typhus in Bulgaria.

Pathogenesis

After entering the body /through the hemolymph of the infected lice through small wounds on the skin/. The spirochetes multiply in the vascular endothelium and in the cells of the reticuloendothelial system.

The appearance of a large number of spirochetes in the blood coincides with the onset of an attack of the disease. The severity of relapsing fever and the damage to tissues and organs depends on the amount of circulating spirochetes, and in the most severe forms it can reach several trillion per liter blood.

The development of thrombohemorrhagic syndrome sometimes reaching the stage of disseminated intravasal coagulation or the so-called DIC-syndrome is also possible.

Under the influence of the antibodies formed in the body, the main part of the spirochetes die, a period of apyrexia occurs, that is, the body temperature drops.

However, a small amount of spirochetes of a new antigenic variant are stored in the blood or in the tissues.

The new antigenic variant is formed spontaneously by genetic mutations with a frequency of one bacterium per 103-105 spirochetes and contains surface proteins that are different from those that caused the infection or the previous relapse.

The spirochetes of the new antigenic variant multiply and after about 7 days their quantity reaches a level sufficient for the development of a new attack. Eventually, immunity is formed against several types of spirochetes and clinical recovery occurs.

Symptoms and course of louse fever

The incubation period lasts from 5 to 15 days, most often around 7 days. In some patients, prodromal phenomena can be observed – general weakness, joint pain, headache, adynamia, difficulty in digestion /dyspepsia/.

Most often, the attack of the disease begins acutely, usually in the first half of the day.

Chills appear, sometimes extremely strong, alternating with a feeling of heat, headache. The body temperature on the first day of the onset of the disease already reaches 39°C and more.

The maximum body temperature is observed on the 2nd-3rd day from the onset of the disease. Patients report pain in the muscles, especially in the lower limbs, severe fatigue, nausea, and nausea and vomiting often occur.

Sometimes there are pains in the area of ​​the left hypochondrium caused by the enlargement of the spleen. The skin of the face turns red due to poor arterial blood flow. Expressed tachycardia, lowering of arterial pressure is observed, heart tones are faintly discernible.

Increases its size and liver. As a result of thrombocytopenia, damage to the liver and vascular endothelium, signs of thrombohemorrhagic syndrome often develop – persistent nosebleeds, hemorrhages on the skin and mucous membranes, hemoptysis, erythrocytes appear in the urine.

In 10-15% of patients, at the peak of the attack, meningeal symptoms such as neck stiffness, etc. are also manifested.