Rocky Mountain Spotted Fever

What is Rocky Mountain Spotted Fever?

Rocky Mountain Spotted Fever (Synonyms: Highland Fever, American Tick-borne Richetsiosis, Bulla Fever, Black Fever, Rocky Mountain Spotted Fever. Maligned Spotted Rocky Fever – Brazil Typhus, Typhus Saeaus aus aus aus aus aus aeur ao fire – acute rickettsial disease, characterized by symptoms of general intoxication and the appearance of abundant maculopapular exanthema, which in a severe course of the disease becomes hemorrhagic.

Causes of Rocky Mountain Spotted Fever

The causative agent of Rocky Mountain spotted fever – Rickettsia rickettsii was discovered by Ricketts in 1906. It is characterized by properties inherent in all rickettsia. It has hemolytic and toxic activity, is an intracellular parasite, colonizes both the nucleus and the cytoplasm. On artificial nutrient media is not growing. Rickettsia is cultivated in the yolk sacs of chick embryos, in cell culture and by infection of laboratory animals (guinea pigs, rabbits, etc.). Dies quickly when heated (+50 ° C) and under the influence of disinfectants.

It is observed in the USA (600-650 cases are registered annually), in Canada, Brazil, Colombia. In the US, about 15 species of ticks have been identified – the natural carriers of the Rockies fever pathogen. The main ones are: Dermacentor andersoni, D. variabilis, Amblyomma arnericanurn.

A person becomes infected with a tick bite, which often goes unnoticed; in the US, only 54.2% of patients reported tick bites about 2 weeks before the disease. In natural foci, there is a natural infection of about 10 species of animals – ticks feeding. Characteristic transovarial transfer rickettsia. Dogs can play the role of an additional natural reservoir of infection.

Pathogenesis during the Rocky Mountain Spotted Fever

The gated infection is the skin at the site of the tick bite. Unlike other tick-borne rickettsiosis, the primary affect at the site of the tick bite is not formed. The lymphatic rickettsia invade the blood, parasitizing not only in the vascular endothelium, but also in the mesothelium, in the muscle fibers. The most pronounced changes in blood vessels are observed in the myocardium, brain, adrenal glands, lungs, and skin. The affected endothelial cells of the vessels necrotize, parietal thrombi are formed at the site of injury with cellular infiltration around them. In severe cases of the disease, extensive ischemic foci are observed in various organs and tissues (brain, myocardium, etc.). Thrombohemorrhagic syndrome develops.

Symptoms of Rocky Mountain Spotted Fever

The incubation period lasts from 3 to 14 days (in milder forms it is longer, and in severe forms it is reduced to 3-4 days). The disease begins acutely with chills, body temperature rises (up to 39-4 ° C), severe headache, weakness, weakness, pain in muscles, bones, joints, sometimes vomiting occurs. Some patients for 1-2 days have mild prodromal symptoms (weakness, loss of appetite). In severe forms of the disease, thrombohemorrhagic syndrome (nasal bleeding, vomiting “coffee grounds”, hemorrhagic rash, bruising at the injection site, etc.) occurs early. Primary affect is not formed, but in some patients, it is possible to detect regional (to the site of the tick bite) lymphadenitis, an increase and tenderness of the lymph node are moderately expressed. On the 2nd-4th day (rarely on the 5th-6th day), an abundant maculopapular rash appears. A rash appears on the limbs, then on the whole body, on the face, on the scalp and almost always on the palms and soles. With the development of thrombohemorrhagic syndrome, the rash undergoes hemorrhagic transformation. In place of spots and papules appear petechiae and larger hemorrhages in the skin. At the site of extensive hemorrhage, necrotization can be observed in the form of gangrene of certain skin areas (scrotum, etc.) and mucous membranes (soft palate, uvula). Conjunctive rash and enanthema on the soft palate is detected. After 4-6 days, the elements of the rash turn pale and gradually disappear. At the site of hemorrhage skin pigmentation persists for a long time. Possible peeling of the skin.

Manifestations of general intoxication are reminiscent of its manifestations in epidemic typhus. There is a strong headache, irritability, agitation, impaired consciousness, hallucinations, delusions. There may be paresis, paralysis, impaired hearing and vision, meningeal signs and other signs of damage to the central nervous system. The duration of the acute period in severe reaches 2-3 weeks. Recovery is slow and even with modern methods of therapy, mortality reaches 5-8%.

According to clinical manifestations, there are: an outpatient form of the disease (subfebrile body temperature, a small rash without hemorrhagic manifestations, the total duration is 1-2 weeks); abortive with acute onset, high fever, duration of fever for about a week, rash quickly disappears; typical with characteristic symptoms and duration of the disease up to 3 weeks, and fulminant, in which in 3-4 days death occurs. The latter form is characteristic of the malignant variant of the fever of the Rockies (Brazilian typhus).

Complications – thrombophlebitis, nephritis, pneumonia, hemiplegia, neuritis, blurred vision, deafness, in the period of convalescence, and in later periods – obliterating endarteritis.

Diagnosis of Rocky Mountain Spotted Fever

In case of severe clinical symptoms and epidemiological data (stay in an endemic area, bites of ticks 5-14 days before the onset of the disease, etc.), diagnosis is possible before obtaining laboratory test data. Serological reactions are used to confirm the diagnosis: agglutination reaction with OXjg and OX2 (Weyl-Felix) proteins, CSC with a specific antigen, the indirect immunofluorescence response recommended by WHO (1993) is more sensitive. Also use the selection of the pathogen from the blood of patients by infection of guinea pigs. Differentiation is necessary with other tick-borne rickettsiosis.

Rocky Mountain Spotted Fever Treatment

The most effective etiotropic drug is tetracycline, which is administered orally at 0.5 g 4 times a day for 5-7 days; for severe forms, it is better to administer the antibiotic parenterally during the first day. Given the frequent occurrence of pronounced throm-bohemorrhagic syndrome, it is necessary to introduce heparin (40 000-60 000 IU per day), it is better drip in 5% glucose solution. With the development of infectious-toxic shock, conduct appropriate therapeutic measures.

Forecast. In severe cases, the prognosis is serious, even with modern methods of therapy. In the United States in recent years, mortality was 5.2%, and among patients older than 40 years – 8.2%. Persistent residual effects (deafness, etc.) are possible.

Prevention of Rocky Mountain Spotted Fever

Tick-borne interventions are carried out in endemic areas and vaccination of contingents at risk of infection.