Rocky Mountain spotted fever is an acute natural focal zoonosis with a predominantly transmissible transmission mechanism caused by rickettsias. The clinical picture is characterized by the presence of fever, general intoxication syndrome, abundant macular-papular rash with a hemorrhagic component, signs of damage to the nervous and cardiovascular systems. Diagnosis is based on the detection of serological markers in the patient’s blood serum. The PCR method is used. Treatment is carried out with antibacterial drugs from the tetracycline group. In parallel, symptomatic therapy is prescribed.
A77.0 Spotted fever caused by Rickettsia rickettsii
The disease was first reported in the mountainous regions of the United States in 1899. Spotted fever is known by various names: mountain fever, Brazilian typhus, tick-borne rickettsiosis of America. This nosology is common in the USA, Canada, Central and South America. Seasonality is characteristic. The peak of morbidity is recorded in the spring-summer period, which is associated with the high activity of vector ticks. Susceptibility is universal, but men from 40-65 years old and children under 10 years old living in rural areas are more likely to get sick. This trend can be explained by the choice of profession (foresters, hunters) and active recreation, respectively.
The causative agent of spotted fever is the gram–negative stick Rickettsia rickettsii. It has a pronounced polymorphism. In cells, it is found both in the cytoplasm and in the nucleus. The microorganism is sensitive to heat, it is quickly inactivated at temperatures above 50 ° C and under the influence of disinfectants. It is resistant to freezing, it remains in a dried state for a long time. The reservoir and source of infection are wild rodents, cattle, dogs. In addition, ixode mites of certain species are considered carriers and a persistent reservoir. A person is a random host. Infection occurs when an insect bites or when a tick is crushed and rubbed in the area of combs. In the carrier, rickettsias persist throughout life, are transmitted transovarially.
The pathogenesis of Rocky Mountain spotted fever is associated with the tropicity of rickettsias to endothelial cells. The primary focus does not form after a tick bite. The parasite enters the regional lymph nodes, and then into the systemic circulation. The pathogen is fixed on endothelial cells, penetrates them and promotes the development of necrosis. Vessels of small and medium caliber of various localization are mainly affected. As a result, parietal thrombi are formed, the production of biologically active substances increases with an increase in the degree of intoxication, antibodies to endotheliocytes begin to be produced.
Infiltrates consisting of lymphocytes, macrophages, plasmocytes and microscopically resembling granulomas form around the affected vessels. Destructive or destructive-proliferative vasculitis develops. When the muscular wall of the vessels is involved in the pathological process, panvasculitis is observed. The most common lesion of the vessels of the kidneys, adrenal glands, skin, heart and brain. A characteristic rash is a consequence of pathomorphological changes in the vessels of the skin. When the lumen is obstructed by a thrombus, necrosis of the corresponding anatomical areas is formed.
The course of rickettsiosis can be diverse and accompanied by various symptoms. The main triad of the disease includes a pronounced febrile reaction, headache and a characteristic rash that appears in a short period of time. In clinical practice, moderate and severe forms of the disease prevail. American scientists have proposed the following classification of Rocky Mountain spotted fever:
- Outpatient form. There is a subfebrile temperature. Minor intoxication is detected with a moderate feeling of malaise, weakness. Rashes may be atypical, with uncharacteristic localization, or absent altogether.
- Abortive form. There is a sharp rise in temperature to high numbers. The fever period is about 7 days. A specific rash also persists for about a week, then disappears, replaced by prolonged pigmentation and peeling.
- Typical form. A typical clinical picture is formed with a pronounced fever lasting about 3 weeks, headaches and muscle pains. Hemorrhagic rash is first detected on the extremities, then spreads to the center of the body.
- Lightning-fast form. It is characterized by an extremely severe course with pronounced intoxication and decompensation of the condition. The patient may fall into a coma from the first days. In most cases, it ends in death after 4-5 days.
Rocky Mountain spotted fever symptoms
The incubation period can be up to 2 weeks, on average lasts 7 days. Sometimes the height of the disease is preceded by a short prodromal period, manifested by malaise, headaches, loss of appetite. Usually, the disease begins acutely with a sharp rise in body temperature to 39-41 ° C, pronounced arthralgia, myalgia and headaches. Possible abdominal pain simulating acute appendicitis (more often in children). In some patients, edema of the dorsal side of the palms is detected. Nausea, vomiting, and nosebleeds often occur. In some cases, periorbital edema is formed, injection of conjunctival vessels. When examining the oral cavity, hemorrhagic rashes are found on the mucous membranes. Gradually, the fever acquires a remitting character with daily temperature fluctuations up to 1.5 ° C. The fever period lasts 2-3 weeks.
On the 3-5 day of the disease, a maculopapular rash appears on the skin of patients. Typical is the primary localization in the ankle joints, wrists and elbows, followed by spread throughout the body. Elements tend to merge. In severe cases, exanthema is found on the palms and soles. From 8-10 days of the course of pathology, the rash becomes hemorrhagic in nature, which in severe forms leads to the formation of necrosis in the area of the tips of the nose and auricles, soft palate and genitals. Rashes begin to disappear after a decrease in body temperature. Pigmentation and bran-like peeling remain in place of the elements for a long time.
Somatic symptoms most often include signs of damage to the cardiovascular system and the central nervous system. Hypotension, bradycardia, deafness of heart tones are possible. Tachycardia corresponds to an extremely severe course of the disease. Collapses are not uncommon. The involvement of the nervous system is accompanied by delirium, convulsions, paresis and paraplegia, paralysis of the cranial nerves, the appearance of pathological reflexes, disorders of consciousness of varying severity up to the development of coma. Hepatolienal syndrome is rarely detected. More than half of the patients develop constipation. There are no specific symptoms of damage to the respiratory and urinary systems.
The most common complications of Rocky Mountain spotted fever are pneumonia and phlebitis. It is possible to develop glomerulonephritis, myocarditis with the occurrence of acute heart failure, neuritis, iritis and obliterating endarteritis, the formation of gangrene of characteristic localization. When the cranial nerves are affected, the appearance of appropriate symptoms is noted (usually – violations of the functions of the organs of hearing and vision). Sometimes seizures, meningism, Guillain-Barre syndrome are detected. Coma is considered the most dangerous complication. From the gastrointestinal tract, bleeding of various localization, perforation, hepatomegaly with jaundice may be observed. There have been cases of rapid decompensation in people suffering from alcoholism and in black men with glucose-6-phosphate dehydrogenase deficiency.
During a physical examination, an infectious disease doctor discovers a specific rash on the skin, sometimes the presence of hemorrhagic elements on the mucous membrane of the oral cavity. There is rarely a primary affect with regional lymphadenitis. If there are signs of central nervous system damage, a neurologist is appointed to consult, who identifies pathological reflexes and symptoms of cranial nerve damage. The following laboratory methods are used to diagnose Rocky Mountain spotted fever:
- General laboratory research. The blood test determines anemia, thrombocytopenia. According to the results of a biochemical blood test, electrolyte balance disorders in the form of hyponatremia are possible, sometimes – an increase in the levels of bilirubin, hepatic transaminases, urea and creatinine. In the cerebrospinal fluid, leukocytosis with elevated or normal glucose levels is noted.
- Identification of infectious markers. It is used to determine the increase in the titer of specific antibodies in the patient’s blood by the ELISA, IFR method. The titer IgM>1:64, IgG>1:128 is considered to be diagnostically significant. A bioassay is used to isolate the pathogen. PCR diagnostics has been developed. The complement binding reaction has a high specificity.
Differential diagnosis is carried out with other spotted fevers, endemic and epidemic typhus, as well as leptospirosis, yersiniosis and secondary syphilis. It is necessary to exclude monocytic ehrlichiosis and granulocytic human anaplasmosis. Sometimes differentiation with hemorrhagic vasculitis and infectious erythema is required. In children, it is important to distinguish rickettsiosis from pharyngitis caused by group A streptococcus, with the appearance of a rash after an acute period.
Rocky Mountain spotted fever treatment
Treatment should be carried out in a hospital under the supervision of an infectious disease specialist with the possibility of transfer to an intensive care unit. Antibacterial agents of the tetracycline series are prescribed, tetracycline and doxycycline can be used. In the treatment of pregnant women, the drug of choice is chloramphenicol. In parallel, symptomatic therapy is carried out (antipyretic, intravenous infusions). Particular attention is paid to the control of electrolyte and water balance. With the development of complications, the treatment plan is adjusted in accordance with the nature of pathological changes.
Prognosis and prevention
The prognosis is doubtful. Mortality, according to various sources, ranges from 5 to 80%. Early detection of the pathological condition and timely administration of antibacterial drugs contributes to a favorable outcome of the disease. Long-term recovery, especially when various body systems are affected, may be accompanied by the formation of persistent disorders. Specific prevention is not carried out. Non-specific measures include the extermination of rodents and ticks, the wearing of special protective clothing, the use of repellents and personal protective equipment. Of great importance is the correct extraction of the tick and the early start of antimicrobial treatment when the first symptoms of the disease appear.