Spotted fever in the Rocky Mountains: causes, symptoms, diagnosis, treatment

Spotted fever of the Rocky Mountains (synonyms: tick-borne rickettsiosis of America, Texas fever, Brazilian typhus, etc.) is an acute natural zochotic rickettsiosis transmitted by ixodid mites and is characterized by remittent fever, severe intoxication, damage to the nervous and vascular system, abundant maculopapular a rash.

For the first time, the "spotted fever of the Rocky Mountains" disease was described by Mahsu in 1899. Studies by Ricketts (1906) proved the transmission of infection through ixodid ticks. Somewhat later, the causative agent of the disease was detected in the blood of patients (Ricketts, 1909), and isolated and studied in detail Wolbach in 1919

[1], [2], [3], [4]

Epidemiology of spotted fever in the Rocky Mountains

Sources and reservoir of infection are wild rodents (voles, ground squirrels, chipmunks, squirrels, rabbits), some domestic animals (cattle, dogs, sheep) and various kinds of ixodid ticks. In warm-blooded animals, the infection is asymptomatic as a temporary carrier. The main and more stable reservoir forms 15 species of ixodid ticks, which are specific vectors of rickettsia. The greatest epidemiological importance is Dermacentor andersoni (forest mite) and D. Variabilis, attacking humans. Transdermal and transphasal transplantations of the pathogen are observed in the mites, which explains the possibility of prolonged, lifelong carriage of rickettsia.

The mechanism of infection transmission is realized with tick bites, less often - when they are crushed and rubbed into the skin of the tick in combs.

The natural susceptibility of people is high. In temperate countries, the disease has a spring-summer seasonality (the period of maximum activity of ixodid mites), in the tropics transmission of infection occurs throughout the year. Villagers and persons of certain professions (foresters, hunters, geologists, etc.) are more often infected when working in the forest or on pastures. The incidence is mostly sporadic. Postinfectious immunity is intense.

Spotted fever in the Rocky Mountains is endemic in most parts of the United States, in Canada, as well as in Central and South America.

[5], [6], [7], [8], [9]

What causes the spotted fever of the Rockies?

Spotted fever of the Rocky Mountains is caused by a small polymorphic gram-negative rod, Rickettsia rickettsi, which belongs to the genus Rickettsia. Parasitizes in the cytoplasm and nuclei of sensitive cells. It is well cultivated in the body of mites of various species, in the transplanted cell lines, in yolk sacs of chick embryos and in the body of guinea pigs, in which it causes the development of toxicosis. The causative agent has hemolytic properties, is colored according to Ramanovsky-Giemsa and Gimenez.

Pathogenesis of spotted fever in the Rocky Mountains

Rickettsii penetrate into the body with a bite of infected ticks without the formation of primary affect, enter the systemic bloodstream and affect predominantly small and medium blood vessels of the skin, subcutaneous tissue, central nervous system, lungs, heart, adrenal, liver and spleen. In the vascular endothelium, fixation and multiplication of rickettsia occurs, necrosis of endothelial cells develops, followed by accumulation of biologically active substances and intensification of toxicosis. In severe infection, necrotic changes are even captured by the smooth muscle fibers of the mesothelium, which underlies the possible development of microinfarctions in the brain substance, DIC syndrome, specific glomerulonephritis, exanthema. Pathohistological changes in the vessels are similar to those in epidemic typhus.

Symptoms of spotted fever in the Rocky Mountains

The incubation period of spotted fever in the Rocky Mountains lasts from 2 to 14 days, on average - 7 days. Sometimes at the onset of the disease, there may be short prodromal events in the form of malaise, mild chills, and mild headache. In most cases, the onset of the disease is acute, sudden. Characteristic are the following symptoms of spotted fever in the Rocky Mountains: severe headache, chills, severe weakness, arthralgia and myalgia, a rapid increase in body temperature to 39-41 ° C. In severe cases, vomiting, prostration, and nasal bleeding occur.

Later the fever acquires a remitting character, with fluctuations between morning and evening indices up to 1-1.5 ° C.

When examining patients at the onset of the disease, such symptoms of spotted fever of the Rocky Mountains are revealed: hemorrhagic enanthem on the oral mucosa, bradycardia, muffling of cardiac tones, lowering of arterial pressure. On the 2nd-5th day of the illness, exanthema usually occurs, although in exceptional cases the rash may be absent. Spotted elements of the rash quickly turn into maculopapular, spread throughout the body, including the face, scalp, palms and soles. During the following days, the rash becomes more distinct, sometimes draining, hemorrhagic, with a necrotic component. In severe cases, there is necrosis of fingertips, ear buds, genitals. Exanthema persists for 4-6 days (sometimes more than a week) and disappears after a drop in temperature, permanently leaving the peeling and pigmentation.

Intoxication syndrome manifests itself as an increase in symptoms of encephalopathy, including painful headache, insomnia, irritability, agitation, impaired consciousness, hallucinations, delirium, delirium and even to someone, which indicates the development of encephalitis. In case of severe illness, paresis and paralysis, hearing and vision impairment, pathological reflexes and other signs of CNS damage can be observed, which persist for weeks and even months.

Disturbances from the cardiovascular system in the midst of the disease are manifested by hypotension, bradycardia, widening of the heart boundaries, muffled heart tones. There may be sudden collapse. The appearance of tachycardia in this period indicates a poor prognosis of the disease. Respiratory organs, the urinary system and the gastrointestinal tract are not significantly disturbed. Hepatolienal syndrome develops irregularly, sometimes with manifestations of jaundice.

The duration of the acute period of the disease is 2-3 weeks. The severity of the course of the disease and the severity of its individual symptoms can vary widely. There are light, moderate, severe and fulminant forms of the disease with the development of coma and death in the early days of the disease.

The period of convalescence is distinguished by the duration and slow reverse development of the disturbed functions of the organism.

Complications of the spotted fever of the Rocky Mountains

The most frequent complications of spotted fever in the Rocky Mountains are thrombophlebitis, pneumonia. Possible acute vascular insufficiency, necrosis of the skin, gangrene, nephritis, neuritis, visual and hearing impairment. In the period of convalescence, the obliterating endarteritis sometimes develops.

Spotted fever of the Rocky Mountains has a rather serious prediction, in severe cases in different foci the mortality varies from 20 to 80%, the early administration of antibiotics reduces it to 7%.

[10], [11], [12], [13], [14], [15]

Diagnosis of spotted fever in the Rocky Mountains

The disease should be differentiated with other tick-borne rickettsiosis, hemorrhagic vasculitis, infectious erythema, leptospirosis, secondary syphilis, iersiniosis. Diagnosis of the spotted fever of the Rocky Mountains takes into account the data of epidemiology (recent visit or stay in the endemic area), acute cyclical development of the disease with intermittent fever, marked toxicosis, hemorrhagic enanthema, maculopapular and hemorrhagic exanthema, symptoms of CNS damage.

[16], [17], [18], [19], [20]

Laboratory diagnosis of spotted fever in the Rocky Mountains

The hemogram has no characteristic changes. Typical proteinuria. Methods of confirmation of the diagnosis are the reaction of immunofluorescence and RSK with rickettsial antigens. Bioassays with laboratory animals (guinea pigs) can be used to isolate the pathogen.

Treatment of spotted fever in the Rocky Mountains

Etiotropic treatment of spotted fever in the Rocky Mountains provides for the use of drugs that have protivorykettsial activity: tetracyclines (doxycycline 0.2 g per day), rifampicin (0.3 g 3 times per day), fluoroquinolones (400-500 mg twice a day ), macrolides in average therapeutic doses. Antibacterial treatment continues throughout the febrile period and the first 2-3 days of apyrexia. Carry out detoxication treatment, prescribe calcium preparations, vikasol, sedatives, glucocorticosteroids.

How is the spotted fever of the Rockies prevented?

For the purpose of nonspecific prevention of spotted fever in the Rocky Mountains on endemic territories, the extermination of rodents and mites is carried out, protective clothing and repellents are used. According to epidemiological information, preventive vaccination of people at risk is carried out.