What is Recurrent Typhus?
Typhoid fever (lat. Typhus recurrens) is a collective name combining epidemic (pathogen carrier – louse) and endemic (pathogen carrier – tick) spirochetosis, which alternate with attacks of fever and periods of normal body temperature.
Typhoid fever is found throughout the world, with the exception of Australia, in the form of a sporadic, epidemic or endemic disease. The highest incidence and the most severe forms of relapsing fever are noted in Africa. Thus, only in Sudan during the ten years after World War I, as a result of this disease, about 100,000 people died – almost 10% of the total population of the country. Typhoid fever is also rampant in India, major epidemic outbreaks have been reported in Russia and in the countries of the Balkan Peninsula. In India, Iran, countries of Southeast Asia, recurrent typhoid fever refers to epidemic infections. In European countries and the United States the disease is less common and occurs in a milder form. Crowded living and unsanitary conditions contribute to the spread of the disease. In Africa, Asia, Europe and South America, the disease is transmitted by lice of the genus Pediculus, which are parasitic on humans. Tick-borne relapsing fever, occurring as an endemic disease in Africa, Asia and Europe, in North America (including Canada and Mexico), in Central America and some regions of South America, is transmitted by ticks of the genus Ornithodorus.
Causes of Recurrent Typhus
The causative agents of relapsing typhoid relate to spirochaetes of the genus Borrelia, in particular, one of the most common causative agents of typhoid fever – Borellia Obermeier Borellia Obermeieri, discovered in 1868 by Otto Obermeyer.
Tick-borne relapsing fever is a zoonotic transmissible disease. The causative agents are many types of borrelia: B. duttonii, B. persica, B. hispanica, B. latyschewii, B. caucasica, common in certain geographical areas. These Borrelia are similar to the causative agent of epidemic recurrent typhoid in morphology, resistance to environmental factors, and biological properties.
Transporters
Tick-borne relapsing fever is an obligate-transmissible disease. It is transferred by ticks of the Argasidae family, such as Ornitodorus papillares (village tick), Argas persicus (Persian tick). Ticks are the reservoir hosts of the spirochete. The reservoir of Borrelia of various species in natural foci are also different species of rodents. Tick infestation persists throughout their life (about 10 years). Transovarial transmission of pathogens, which penetrate into the oviduct and ovum of arthropods, also takes place. In natural foci there is a constant circulation of the pathogen from rodents to ticks and back. Animals and mites parasitizing on them usually accumulate in burrows, caves, but find for themselves dwelling in various economic structures in settlements.
A person becomes infected with tick bites. At the site of inoculation of the pathogen a papule is formed (primary affect). The pathogenesis and clinical manifestations of tick-borne typhus are similar to the epidemic. Diseases often occur in the warm season with the activation of vital activity of ticks.
The population of areas endemic for tick-borne typhoid fever acquires a certain degree of immunity to circulating pathogens – in the serum they show antibodies to borrelias that are common in this region. Mainly visitors are getting sick.
Carriers of epidemic B. typhus – lice Pediculus humanus capitis (head), P. humanus humanus (ward) and Phtirius pubis (pubic). A louse sucking the blood of a patient becomes capable of infecting a person throughout its life, since Borrelia is non-pathogenic for lice, and microorganisms reproduce well in the insect hemolymph. Transovarial transmission of borrelia in lice does not exist. A person becomes infected by rubbing a hemolymph containing Borrelia with lice (by combing a bite, crushing an insect) (contaminant infection). In the environment, Borrelia die quickly. Under the action of a temperature of 45-48 ° C, death occurs in 30 minutes. Epidemic recurrent typhus affects only people.
Pathogenesis During Relapsing Typhoid
Once in the internal environment of the body, Borrelia invade the cells of the lymphoid-macrophage system, where they multiply and then flow into the blood in larger quantities. Under the influence of the bactericidal properties of the blood, they are partially destroyed and at the same time endotoxin, which damages the blood and central nervous system, is released. Toxicosis is accompanied by fever, and necrosis occurs in the spleen and liver. Due to the formation of borrelia aggregates under the influence of antibodies, which are retained in the capillaries of the internal organs, the local blood supply is disrupted, which leads to the development of hemorrhagic heart attacks.
The first febrile period of the disease ends with the formation of antibodies against the first-generation Borrelia. Under the influence of these antibodies, microbial aggregates appear with a load of platelets and most of the borrelia die. Clinically, this is expressed by the onset of remission. But part of the pathogens change antigenic properties and become resistant to the formed antibodies, stored in the body. This new generation of Borrelia multiplies and, flooding the bloodstream, gives a new bout of fever. The resulting antibodies against the second generation of the pathogen lyse a significant portion of them, but not completely. Resistant pathogens that have altered antigenic specificity, multiplying, again give a relapse of the disease. This is repeated several times. Recovery occurs only when a spectrum of antibodies appears in the blood, lysing all the antigenic variants of borrelia.
The disease does not leave a lasting immunity. Formed antibodies persist for a short time.
Symptoms of Relapsing Typhoid
The first attack begins suddenly: a short-term chill is replaced by fever and headache; pains in the joints and muscles (mainly gastrocnemius), nausea and vomiting. The temperature quickly rises, the pulse is frequent, the skin is dry. The nervous system is involved in the pathological process, delirium often occurs. At the height of the attack appear various forms of rash on the skin, spleen and liver are enlarged, jaundice sometimes develops. During a fever, there may be signs of heart damage, as well as bronchitis or pneumonia. The attack lasts from two to six days, after which the temperature drops to normal or subfebrile and the patient feels quickly improved. However, after 4–8 days, the next attack develops with the same symptoms. Cases of the disease without repeated attacks are rare.
For vsino recurrent typhoid one or two recurrent episodes are characteristic, which end in complete recovery and temporary immunity. Tick-borne relapsing fever is characterized by four or more bouts of fever, they are shorter and easier in clinical manifestations, although the second attack may be harder than the first.
Complications. Meningitis, iritis, iridocyclitis, uveitis, spleen rupture, synovitis. The previously observed icteric typhoid is a layering of Salmonella infection.
Diagnosis of Relapsing Typhoid
Recognition is based on epidemiological data, a characteristic clinical picture of the disease (acute onset, critical temperature drop with profuse sweating at the end of an attack, early and significant enlargement of the spleen (splenomegaly), alternation of febrile seizures and apyrexia). Peripheral blood tests (moderate leukocytosis, especially during an attack, aneosinophilia, thrombocytopenia, increasing anemia, ESR increased) have a diagnostic value.
Laboratory diagnosis
During an attack, at the height of a fever, the pathogen can be relatively easily detected in the patient’s blood. For this purpose, preparations of a thick drop or blood smear are prepared, stained according to Romanovsky – Giemsa or fuchsin and microscopically. You can microscopy blood drops in a dark field, watching the mobility of borrelia. The method of serological diagnosis consists in the formulation of lysis reactions, RSK.
The differentiation of epidemic from endemic relapsing fever is carried out in a biological experiment: a guinea pig is injected with the patient’s blood. Borrelia epidemic relapsing fever in contrast to endemic do not cause animal disease. With tick-borne typhus, mumps gets sick on days 5-7, and Borrelia is found in its blood.
Treatment of Recurrent Typhoid
Antibiotics (penicillin, chloramphenicol, chlortetracycline) and arsenic drugs (novarcelon) are used to treat epidemic recurrent typhoid. In the treatment of tick-borne typhus used antibiotics tetracycline, chloramphenicol, ampicillin.
Prevention of Relapsing Typhoid
Preventing epidemic typhus comes down to combating lice, avoiding contact with patients with stiffness. Currently, in our country and in many others, epidemic typhus is not found. Preventing tick-borne typhoid fever consists of protecting people from tick attacks, exterminating rodents and insects in natural foci.