What is typhoid fever?
Typhoid fever is an infectious disease from the group of anthroponoses with fecal-oral mechanism of transmission caused by one of the varieties of Salmonella and proceeding with a primary lesion of the lymphatic apparatus of the small intestine on the background of pronounced toxic effects.
Despite the fact that mankind in the last century have significantly reduced the number of registered cases of typhoid fever, resolved to end this problem, can not be named. The likelihood of developing the disease exist, particularly in countries with troubled military situation and the poor hygienic norms for life. Therefore unhygienic conditions are a major condition for the spread of the disease.
Typhoid fever is the disease solely of the human population. Infection occurs after isolation from faeces of carriers and sick people germs in the environment. About the same time they containeralso water, food, household items. Not the last value belongs to flies as carriers of foreign pathogens. A healthy person can get sick after consuming infected food or after direct contact with patients.
In this regard, typhoid fever is characterized by the following features:
Predominant occurrence in the hot months and autumn;
The rapid spread of the transition in the epidemic;
The absolute susceptibility of human organism to the pathogen;
The proliferation of Salmonella with their massive release into the environment with every bowel movement;
A long course of the disease (about seven weeks) and it erased forms;
The presence of carriers of the causative agent of the disease. These people are not sick, but are contagious to others;
The pathogenesis of the disease and the spread of the pathogen inthe body consists of several stages:
Getting sufficient concentrations of pathogens in terminal small intestine;
Introduction through the mucous membrane with the development of the inflammatory process in the form of enteritis;
Penetration into lymphoid tissue to which Salmonella there is an inherent affinity. First affects Peyer's patches, and then the regional lymph nodes of the mesentery (mesenteric) and retroperitoneal;
Bacteremia (the passage of pathogens into the systemic circulation). This arises from the inability of the lymphatic system to hold and neutralize the pathogen. This is manifested in the form of their strong gains. Once in the blood of the portal system, the pathogen primarily spreads to the liver and spleen. In the cells of the reticuloendothelial system in these organs is its further reproduction. As a consequence, inflammation of the liver and spleen;
The circulation of the pathogen in systemic circulation triggers the immune response. While there is massive destruction of the pathogenic bacteria that, along with bacteremia, causing the toxemia due to toxins that are secreted from the destroyed pathogens.
All these stages of pathogenesis are cyclical in nature, constantly repeating up until the immune mechanisms will increase enough to neutralize all pathogens in the tissues of the lymph nodes, liver and spleen.
The symptoms of typhoid fever
The clinical picture in typhoid fever comes up from the above described peculiarities of its pathogenesis and is given in the form of a table.
The incubation period
Its duration from three days to three weeks. At this time, possible non-specific symptoms such as General weakness, weakness, feeling sick, nausea, head and muscle aches, light fever.
Fever and temperature of the reaction
It is noted increased body temperature to hectic numbers. Such a fever is noted periodically, which corresponds to a massive release of Salmonella in the systemic circulation.
Signs of mesenteric lymph node and small intestine (mezadenita on the background of enteritis)
The signs of liver and spleen
Dynamics of symptoms in typhoid fever allows you to combine them according to stages of the disease:
The period of incubation.Continues since the introduction of the pathogen into the body before the first clinical manifestations. The duration of this period depends on the pathogenic properties of the pathogen and the body's defenses;
The beginning of the disease. Lasts a few days. Clinical it is possible to limit the appearance the first thermal reaction to her persistent maintain at a high level;
The expanded period of flow. Is characterized by all symptoms of internal organs and intoxication;
The period of permission. Presents step-by-step reverse development of symptoms and fever reduction;
The period of convalescence. Is a full restoration of an organism and formation of resistant immunity.
Not always such a clear sequence of flow observed. The disease can become unpredictable with lightning transition from one stage to another or undulating their shift.
The danger of typhoid fever consists in the possibility of complications that immediately threaten the patient's life. In the case of disease progression, the risk of progressive liver failure, which on the background of intoxication can go into multiple organ failure.
No less dangerous and complications of a local nature. Their occurrence is associated with necrotic and ulcerative lesion of the terminal segment of the small intestine. Against this background very often have profuse intestinal bleeding and perforation of the intestinal wall. These conditions require urgent surgical treatment. The carrying out of any operations at the height of intoxication and organ failure always leads to worsening of the General condition of patients with typhoid fever.
The causative agent of typhoid fever
The pathogen which causes the occurrence of typhoid fever is one of the types of Salmonella – Salmonella typhi. Is a gram-negative Bacillus of the family Enterobacteriaceae, capable of reproduction only in the human body. Morphological differences from other Salmonella does not. Strict aerobe, therefore, can only exist in a living form, does not form spores. Not demanding to the surrounding environment so well cultivated on ordinary nutrient media. This type of Salmonella is enough stable inthe external environment, perfectly adapted to low temperatures and can survive even prolonged freezing.
Not resistant to high temperatures and instantly killed by boiling. It keeps pathogenic properties in flowing and stagnant water, and food (dairy products, vegetables, meat).
The typhoid pathogenicity of Salmonella due to their antigenic structure and endotoxin. The most important of them are the surface antigen is a virulence (Vi-antigen) and lipo-sugar-barnacles belcove complex cell wall (endotoxin). If the first determines the ability of a pathogen to affect organs and tissues, as well as the intensity of the immune response, the latter included the destruction of Salmonella by the immune cells with a powerful release of their toxic components. Features of antigen virulence of the causative agents of typhoid are such that allow him to change their antigenic properties, passing in different forms, including L-forms resistant to antimicrobial drugs. This allows the pathogen long to circulate, keeping the epidemic spread.
Life cycle of typhoid Salmonella after being hit in the susceptible organism can not pass without the participation of the lymphoid and reticular tissues. So gateway of infection campaigners clusters of lymphatic cells of the intestine (Peyer's patches) in the submucosa. Of these, bacteria spread to the mesenteric lymph nodes and portal blood flow. The most important place of reproduction of typhoid Salmonella becomes the liver and spleen. Over time, the immune mechanisms are able to neutralize pathogens, produced specific antibodies.
Serological testing for typhoid
Given that the distinguishing microscopic features typhoid Salmonella does not exist, the main method of diagnosis of abdominal typhus are serological studies. Their basis is the detection in plasma of specific antibodies.
This can be done in the following ways:
Agglutination. The easiest and most ancient method to determine the presence of antibodies to O-antigen of the pathogen. Getting informative two weeks after the onset of the disease. The method is nonspecific because it can give a false positive result when other types of Salmonella infection;
The reaction of indirect hemaglutination. Helps in the diagnosis of typhoid fever in the first week of the disease;
the Reaction of fluorescent antibodies. Highly sensitive diagnostic method, allowing to define any type of antibodies to antigenic components of the pathogen. Method helps not only in assessing the dynamics of the disease, but also in monitoring the media, and in reconvalescence period;
The basis for the diagnosis of typhoid fever according to the serological methods of diagnosis is a constant rise in titer of specific antibodies. For this study an indication of the dynamics.
Vaccination against typhoid and paratyphoid
The main preventive measure at typhoid is vaccination against this disease.
For this purpose, two types of vaccines:
Live containing attenuated typhoid Salmonella. Available in tablet forms;
Killed containing inactivated Salmonella. Available in injectable form.
Components introduction typhoid Salmonella in the body in small doses, leads to their recognition by immune cells. The result of this interaction should be long-term immunity, which will allow the body to confront the real agents when you meet them.
Indications for vaccination of any of the types of vaccines are:
Planning a stay in the territories epidemica in abdominal typhus;
The need of contact with sick with typhoid fever;
Direct work with pathogens of typhoid fever.
It is desirable that after the vaccination for two weeks vaccinated, the body is not in contact with the true causative agent of the disease. This is necessary in order to develop appropriate immunity. Otherwise, vaccination will end by worsening symptoms.
Contraindications for vaccination:
Allergic reactions to components of vaccines in history;
Child age (in the injection, up to 2 years, with tablets up to 6 years);
Powerful antibiotic therapy;
Colds and exacerbation of chronic disease;
The appointment of glucocorticoid hormones;
Cancer and chemotherapy.
After vaccination are possible reactions:
Inflammatory changes at the injection site;
Headache and muscle pain;
Nausea and vomiting;
Allergic reactions (urticaria, bronchospasm, drop in blood pressure)
The presence of reactions to the vaccine (except allergic) poses no threat. They indicate the immune mechanisms.
For the prevention of paratyphoid developed an injectable vaccine. Their technique involves the introduction of a course admission: twice with 4 week intervals between injections.
Which doctors should contact if You have typhoid fever?
Treatment, prevention, monitoring reconvalescence and carriers of typhoid fever deals with infectious disease physician. If necessary, the medical diagnostic process includes related professionals. It can be a: surgeon – if you have symptoms of acute abdomen and needs differential diagnoses, resuscitation – when a progressive worsening of the patient's condition and organ failure.