INFECTIOUS DISEASES : RABBIT FEVER (TULAREMIA) - etiology, pathogenesis, symptoms and course of, recognition, prediction and prevention
Etiology. Pathogen Century tularensae - short rod with rounded edges (coccobacilli), characterized by polymorphism and bipolar okrashivaemoy, morphologically similar to the plague Bacillus. When the crops from the bodies of rodents gives slow growth on special nutrient media with the addition of chicken egg yolk.
Epidemiology. The main reservoir of the virus are wild-living rodents: rabbits (America, Australia), ground squirrel, water rats (CIS and Russia), hares, ground squirrels, marmots. In recent years, described a major epidemic among field rodents (voles and other), and house mice and even rats, much closer reservoirs of the virus in animals to humans. Animals become infected from each other by direct contact (droplet path, devouring the sick and dead animals), and contact with secretions and excreta of infected animals and is transmitted by fleas, lice, ticks, horseflies, botflies, mosquitoes).
The escalation of the epidemic in the epidemic occurs in connection with a man closer to the hearth of the epidemic (commercial epidemic) or, on the contrary, the approximation of the epidemic to the man (infection collected in the fields loaves of bread, grain, food in pantries). The resistance in the external environment, as well as in organs and meat of animals coming in human food, is the main cause of multiple human diseases. A number of blood-sucking parasites that feed on human and animal, is also a link in the epidemiological chain of tularemia: horseflies, botflies, flies Zhigalko, mosquitoes carry the infection purely mechanical, pasture ticks long preserve of tularemia pathogen and can infect humans throughout their lives. Well-known role in the transfer of infection from animals to humans play some birds of prey. Infection reservoirs sick animals leads to the development of prominent outbreaks among humans and contamination of food - nutritional epidemics. Commercial epidemic associated with hunting period, develop more often in the spring, during floods; epidemics originating from voles occur in the autumn and winter.
Route of human infection, Rudneva, the following:
1) contact: a) direct (hunting, striping and processing skins, laboratorie experiments, cooking from hares and rabbits, catch voles, contact with the killed animals) and b) indirect (bathing, washing with contaminated water, contact with contaminated objects, hay, straw, grain, etc.,);
2) suction (dust infection during harvest and disassembly Stogov, ricks, etc., and drip in the infection from infected animals);
3) alimentary (water, food);
4) transmitted through ticks and blood-sucking flying insects). The largest size reached epidemic arising aspirational by (voles). People not infected.
The pathogenesis. In susceptible animals tularemia flows by type of septicemia with the formation of multiple small necrotic lesions in the internal organs (spleen, liver, kidneys, lungs) and lymph system.
A person zabolevania developing a more diverse, depending on the routes of infection and the gate of the infection. When the infection through the skin and mucous membranes (conjunctiva often) formed the primary foci of local reactions in the form of sysusages bundle. When the suction infection often develops local reactions at the tonsils (tularemia angina). The causative agent of tularemia has defined lymphotropism, therefore, as a rule, develops regional lymphadenitis (bubo), clearly acting at peripheral location (submandibular, cervical, axillary, inguinal) and inaccessible to observation in the abdominal location. In addition to the primary Bubnov closely related to the localization of introduction of infection can occur and secondary bubany due to the transfer agent hematogenous route. Lymph nodes person serve as a barrier, which by severe local reactions counteracts the generalized spread of the pathogen throughout the body. In addition to abscesses can be the outcomes of Bubnov in ulceration with subsequent scarring, sclerotization or resorption. The overall reaction, in particular, temperature, accompanies all forms of tularemia, but in a generalized form, arising mainly by suction and flowing without the observable local manifestations, the temperature response is the only early manifestation of the disease. In this form the General phenomena are in the form of intoxication is mainly the nervous system. Secondary lesions in the internal organs, although formed, but do not reach such a strong development in animals.
Symptoms. Acute onset: high fever with chills in all forms. Headache, muscle pain. In the early days you can mix with fever, flu. Primary ulcers on the skin or conjunctiva, regional bubany without periadenitis. In generalized form of the dimming of consciousness, sometimes crazy, often erythematous skin rash.
For. Incubation is 3 to 4 days; it can be shortened to 1 day and be extended up to 14 days.
1) the generalized form (corresponds to septic and typhoidal forms by Francis);
2) bubonic subdivided into ulcerative-bubonic, pure bubonic, angina-bubonic, oculo-bubonic (better conjunctival-bubonic and abdominal;
3) lung (often bronchietasis or flu-like version of it, at least - pneumonic).
Other symptoms in addition to these, in the first 2 to 3 days is not observed. Suspected tularemia at this time there is epidemiological evidence order (stay in epidemic outbreak, contact with sick animals or knowingly infected subjects, work in special compartments laboratories). In a generalized form of the General phenomenon is expressed more sharply: General oppression, sometimes darkening of consciousness and even delirium. Bubonic form until recently was considered to be the most frequent. When skin or ulcerative-bubonic form on the site of the introduction of infection on the 3 - 4th day of illness formed the knot with subsequent necrotization and ulceration. At the same time developing regional lymphadenitis. The size of the inflamed glands different to chicken eggs and more; glands dense, painful, with the skin and underlying tissues are not. Localization of skin ulcers and Bubnov depends on the method of infection: when handling carcasses - most of the upper limb and axillary bubany, when transmissible infections through blood-sucking flying on exposed parts of the body, when the tick bites in different places. Bubany kept for a long time and after healing skin ulcers, and after the fall of temperature. Sometimes they appear and without sores at the place of introduction of infection is purely bubonic form.
The penetration of infection through the conjunctiva develops conjunctival-bubonic form of education submandibular buboes. The conjunctiva is a sharp hyperemia, swelling, accumulation of mucous secretions and superficial necrotic plaque with the formation of ulcerations. When angina-bubonic form on the forefront are the changes from tonsils (see infectious Angina). The nature of angina mostly necrotic, which gives it a resemblance to a sore throat Plaut-Vincent; often outgrowths on the amygdala leads to confusion with diphtheria (see Recognition). Submandibular lymphadenitis persists after the disappearance of angina. Abdominal shape develops as a result of alimentary infection; affects the mesenteric glands, which sometimes cannot probe. Possible complications of peritonitis. The generalized form is particularly often took place in a laboratory infections from experimental animals. Recently described large autumn-winter outbreaks associated with contamination of the suction means (dust infection) threshing, separation of a hay bale, ricks, etc., As described above, during the most severe with symptoms of intoxication and prolonged fever (about 2 weeks) continuous, remittent and less on the intermittent type. Often enlargement of the spleen. More often than in other forms of rash appears roseolous-papular or erythematous nature, with symmetric localization and subsequent desquamation. Less likely to have pulmonary form, giving two options: a) tracheo-bronchial, which is like the flu and flowing with the defeat of bronchial and peribronchial lymph nodes, and b) pneumonic occurring during the small-focus phenomena pneumonia with a tendency to the formation of foci of suppuration and necrosis; the long, frequent complications (abscess, pleurisy). In all forms of tularemia - leukopenia with neutrophilic shift to the left, and monocytosis. In suppurative processes, leukocytosis with neutrophilia. ROHE accelerated. The reduction in blood pressure inherent in all forms, but more dressed up mockingly in generalized form (marked lability of the pulse). The outcome of tularemia is often favorable, somewhat worse prognosis of visceral forms.
Recognition in the early days of the disease is very difficult because of the lack of characteristic features. In epidemic foci fever should raise suspicion for tularemia. The appearance is typical for tularemia changes on the skin or mucous membranes and Bubnov facilitates recognition. Differences: the plague the absence of a strong painful skin ulcers,severe abmho state; bubany not fused with surrounding tissues, relatively little painful. From anthrax - no black scab, Corolla small bubbles around it, anaesthesia and swelling. Diphtheria - no fibrinous spreading plaque swelling of the surrounding tissues and the presence of adenopathy, sharply different from diphtheria. From a sore throat and Plaut-Vincent - presence of pain and buboes, strong overall reaction. The most difficult recognition generalized forms, and deleted forms of proceeding without temperature reactions and symptoms.
In addition to the above clinical signs, it is necessary to use methods of specific diagnostics:
a) Test with toleenum (killed by heating to 50º suspended Century tularensae containing 100 million microbial cells in 1 ml). Cularin is injected intradermally in a volume of 0.1 ml tuberculin syringe). The reaction is observed after 24 and 48 hours. If a positive reaction at the injection site redness, swelling, and when pronounced reaction - even a limited necrosis. Quickly disappearing erythema without edema is non-specific. The positive reaction from the 5th day of illness (recommended repetition trials),
b) Reaction of agglutination with telarium the diagnosticum gives a positive result with a 9 - a 10-day illness; titer it further increases (it is necessary to follow the dynamics of title by repeated reactions). Both of these reactions, especially the first, suitable for retrospective diagnosis in a timely manner not recognized diseases,
C) Biological method applicable to a special laboratory. Infectious material taken from the patient (split skin ulcers or conjunctival smears from the tonsils, punctate buboes, blood), catches a white mouse or a Guinea pig. When disease or mortality emulsion from their bodies infect new animals, and from them comes the material for bacteriological crops on a special nutrient medium. Due to the risk of laboratory infection, this method is possible only in laboratories for special purposes. It is necessary to clarify tularemia etiology of epizootics, the establishment of infection of water and food.
Prevention is the determination of the existence of the epidemic among rodents in a wide measures for the destruction of rodents in the presence of epidemic and guard against rodents storage locations taken from the fields of cereals, storage of grain products, as well as measures to prevent the possibility of transmission from animals to man (denial hunting, destruction of infested rodents ricks and haystacks, akapana special ditches or fences icy shaft of the dugouts, water disinfection, and so on). Systematic observation of the number of field rodents and their case is in epidemic foci and in places threatened. On the number of rodents is judged by the number of holes per unit area. Catch rodents produced by mechanical means (baskets, Capranica and so on). To destroy apply satrapy sodium fluoride and barium carbonate.
During harvest and the relaying of ricks require glasses-canned and respirators. The lower layers ricks and haystacks, usually populated by voles, it is recommended to burn after the preliminary digging. Ring ditch for protection from voles escapes to a depth of 50 - 60 cm, width 40 cm, slightly wider to the bottom of the ditch. Protective shafts made from snow-50 - 60 cm and covered with water; the passage is pulled out of the ditch above the sample. Water disinfection is achieved by its chlorination and boiling. A great achievement of Soviet science is to develop a method of active immunization N. A. Gai and B. I. by Elbert. Tularemia vaccine is made from live avirulent strains Century tularensae. Vaccinations can be cutaneous method (like oppresively).
Treatment is mainly symptomatic. For skin ulcers - local gray mercury ointment. On bubny - local heat treatments (warm compress, diathermy); when softening - surgical intervention. Monitoring of the cardiovascular system and appropriate medical therapy. Recently, encouraging results obtained from the use of vaccine therapy by subcutaneous or more effective intravenous. The vaccine contains 50 million microbial cells in 1 ml Dosage: 1 injection of 0.1 ml, 2-I - 0.2 ml and 3-I - 0.3 ml; intervals 5 days. According to Shapiro and others, the overall reaction is often pronounced, but bubny or quickly nagnaivajutsja and heal, or dissolve. The method requires further validation. The best results will give the therapy of cutaneous immunization of live avirulent vaccine (vaccination every 2 days).