Typhoid Fever - Symptoms, Diagnosis, Prevention. The Causative Agent Of Typhoid Fever

2024 Author: Josephine Shorter | [email protected]. Last modified: 2023-12-16 21:43

Typhoid fever

What is typhoid fever?

Typhoid fever is an infectious disease from the group of anthroponoses with a fecal-oral transmission mechanism, caused by one of the varieties of Salmonella and proceeding with a predominant lesion of the lymphatic apparatus of the small intestine against a background of pronounced toxic manifestations.

Despite the fact that mankind in the last century managed to significantly reduce the number of registered cases of typhoid fever, which was resolved to the end, this problem cannot be named. The likelihood of developing the disease exists, especially in countries with a turbulent military environment and poor hygiene standards for life. Therefore, unsanitary conditions are the main condition for the spread of the disease.

Typhoid fever refers to diseases, exclusively, of the human population. Infection occurs after excretion of the causative agents of the disease in the feces of carriers and sick people into the environment. At the same time, they contaminate water, food, household items. Flies are also important as external carriers of pathogens. A healthy person can get sick after eating contaminated food or after direct contact with a sick person.

In this regard, typhoid fever is characterized by the following features:

1. Occurs predominantly in hot months and autumn;
2. Rapid spread with the transition to an epidemic;
3. The absolute susceptibility of the human body to the pathogen;
4. Rapid reproduction of Salmonella with their massive release into the environment with each bowel movement;
5. Long course of the disease (about seven weeks) and the presence of its erased forms;
6. The presence of carriers of the causative agent of the disease. Such people do not get sick, but are contagious to others;

The pathogenesis of the disease and the spread of the pathogen in the body consists of several stages:

1. The ingress of a sufficient concentration of pathogens into the terminal sections of the small intestine;
2. Introduction through the mucous membrane with the development of an inflammatory process in the form of enteritis;
3. Penetration into lymphoid tissue, to which Salmonella has an initial tropism. First, Peyer's patches are affected, and then the regional lymph nodes of the mesentery (mesenteric) and retroperitoneal;
4. Bacteremia (entry of pathogens into the systemic circulation). This occurs due to the inability of the lymphatic system to keep and neutralize the pathogen. This manifests itself in the form of their strong increase. Once in the blood of the portal system, the pathogen, first of all, spreads to the liver and spleen. In the cells of the reticuloendothelial system of these organs, its further reproduction takes place. As a result - inflammatory damage to the liver and spleen;

5. The circulation of the pathogen in the systemic circulation triggers immune responses. In this case, a massive destruction of pathogenic bacteria occurs, which, along with bacteremia, causes toxemia due to toxins that are released from destroyed pathogens.

All these links of pathogenesis are cyclical, constantly repeating until the immune mechanisms are strengthened enough to neutralize all pathogenic pathogens in the tissues of the lymph nodes, liver and spleen.

Typhoid Fever Symptoms

The clinical picture with typhoid fever emerges from the above-described features of its pathogenesis and is given in the form of a table.

Its duration is from three days to three weeks. At this time, nonspecific symptoms are possible in the form of general weakness, weakness, poor health, nausea, headaches and muscle pains, mild subfebrile condition.
Fever and temperature reactions	There is an increase in body temperature to hectic figures. Such a fever is noted periodically, which corresponds to a massive release of Salmonella into the systemic circulation.
Intoxication symptoms	Chills at the height of a febrile attack; Sweating; General weakness, dizziness; Muscular-joint pain; Tachycardia and rapid breathing; Decrease in blood pressure; Clouding of consciousness and lethargy; Rash of a roseolous character over the entire surface of the skin (appear after two weeks of illness); Fuliginous tongue (sharply edematous, on the lateral surfaces of teeth imprints, covered with a dark coating); Sharp puffiness of the face against the background of its pallor; Exhausted appearance of the patient.
Signs of damage to the mesenteric lymph nodes and small intestine (mesenteric infection against the background of enteritis)	Pain in the right abdomen. Sometimes they are so intense that they simulate a clinic of acute appendicitis or an acute abdomen; Possibly slight loosening of the stool. The symptom does not always appear. Complicated typhoid fever can manifest itself in the form of bloody diarrhea or intestinal bleeding; Falling Down Symptom. It is determined by percussion of the abdominal wall, during which in the lower right parts of the percussion sound becomes shortened; On palpation, tumor-like formations are determined in the iliac region on the right in the form of an infiltrate, sharply painful; Peritonitis symptoms. They arise when the wall of the small intestine is completely destroyed by the inflammatory process and its perforation; Abdominal distension.
Signs of liver and spleen damage	Hepatomegaly - a sharp increase in the size of the liver and its soreness; Splenomegaly - a painful spleen protruding from under the left costal arch is palpable; Jaundice. As a rule, it is parenchymal in nature and indicates a severe course of the disease; Signs of liver failure: aggravation of cerebral symptoms and impaired consciousness, bleeding, increased jaundice, intoxication;

The dynamics of symptoms in typhoid fever allows you to combine them according to the stages of the disease:

1. Incubation period. It continues from the moment the pathogen is introduced into the body until the first clinical manifestations appear. The duration of this period depends on the pathogenic properties of the pathogen and the body's defenses;
2. The period of the onset of the disease. Lasts for several days. Clinical it can be limited by the appearance of the first temperature reaction until it is persistently maintained at a high level;
3. The period of the unfolded current. It is characterized by all the symptoms of damage to internal organs and intoxication;
4. Period of resolution. Presented by a step-by-step regression of symptoms and a decrease in fever;
5. Convalescence period. It is a complete restoration of the body and the formation of strong immunity.

Such a clear sequence of flow is not always observed. The disease can acquire an unpredictable character with a lightning-fast transition from one stage to another or a wave-like change.

The danger of typhoid fever lies in the possibility of developing complications that pose an immediate threat to the patient's life. In case of progression of the disease, there is a high risk of progressive liver failure, which, against the background of intoxication, can turn into multiple organ failure.

Local complications are no less dangerous. Their occurrence is associated with necrotic and ulcerative lesions of the terminal section of the small intestine. Against this background, profuse intestinal bleeding and perforation of the intestinal wall very often occur. These conditions require urgent surgical treatment. Carrying out any operation at the height of intoxication and organ failure always leads to an aggravation of the general condition of patients with typhoid fever.

The causative agent of typhoid fever

The pathogenic microorganism that causes typhoid fever is one of the types of Salmonella - Salmonella typhi. It is a gram-negative bacillus from the family of enterobacteriaceae, capable of reproduction exclusively in the human body. It has no morphological differences from other Salmonella. Strict aerobic, therefore, can exist only in a living form, does not form a spore. Not demanding on the environment and therefore well cultivated on conventional nutrient media. This type of Salmonella is quite stable in the external environment, perfectly adapted to low temperatures and can even survive long-term freezing.

Not resistant to high temperatures and instantly perishes when boiled. It retains its pathogenic properties well in running and standing water and food products (dairy products, vegetables, minced meat).

The pathogenicity of typhoid Salmonella is due to their antigenic structure and endotoxin. The most important of these are the surface virulence antigen (Vi antigen) and the liposaccharide protein complex of the cell wall (endotoxin). If the first determines the ability of the pathogen to infect organs and tissues, as well as the intensity of the immune response, then the second is activated when Salmonella is destroyed by immune cells with a powerful release of their toxic components. The peculiarities of the virulence antigen of typhoid pathogens are such that they allow it to change its antigenic properties, changing into different forms, including L-forms, resistant to the action of antibacterial drugs. This allows the pathogen to circulate for a long time, maintaining the epidemic spread.

The life cycle of typhoid Salmonella after entering a susceptible organism cannot pass without the participation of lymphoid and reticular tissues. Therefore, the entrance gate of infection is the accumulation of intestinal lymphatic cells (Peyer's patches) in the submucosal layer. Of these, bacteria spread to the mesenteric lymph nodes and into the portal bloodstream. The most important breeding ground for typhoid Salmonella is the liver and spleen. Over time, immune mechanisms are able to completely neutralize pathogens, as specific antibodies are produced.

Serological examination for typhoid fever

Given that the distinctive microscopic features of typhoid Salmonella do not exist, the main method for diagnosing typhoid fever is serological research. They are based on the detection of specific antibodies in blood plasma.

This can be done in the following ways:

1. Agglutination reaction. The simplest and most ancient method to determine the presence of antibodies to the O-antigen of the pathogen. Becomes informative two weeks after the onset of the disease. The method is non-specific, since it can give a false-positive result in other types of salmonella infection;
2. Indirect hemagglutination reaction. Helps in the diagnosis of typhoid fever already in the first week of the disease;
3. Fluorescent antibody response. A highly sensitive diagnostic method that allows you to determine any type of antibodies to the antigenic components of the pathogen. The method helps not only in assessing the dynamics of the disease, but also in observing the carriers, and in the reconvalescent period;

The basis for the diagnosis of typhoid fever according to serological diagnostic methods is a constant increase in the titer of specific antibodies. For this purpose, studies are necessarily repeated over time.

Vaccination against typhoid and paratyphoid fever

The main preventive measure for typhoid fever is vaccination against this disease.

For these purposes, two types of vaccines are used:

1. Live, containing weakened typhoid salmonella. Available in tablet form;
2. Killed, containing inactivated salmonella. Available in injection form.

The introduction of the components of typhoid Salmonella into 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 withstand real pathogens when it encounters them.

Indications for vaccination with any of the types of vaccines are:

1. Planning of stay in territories epidemic for typhoid fever;
2. The need for contact with patients with typhoid fever;
3. Direct work with causative agents of typhoid fever.

It is advisable that after the vaccination for two weeks the vaccinated organism does not come into contact with the true causative agent of the disease. This is necessary in order to develop the appropriate immunity. Otherwise, vaccination will result in worsening of the symptoms of the disease.

Contraindications for vaccination:

1. History of allergic reactions to vaccine components;
2. Children's age (with injections - up to 2 years, with tablets - up to 6 years);
3. Powerful antibiotic therapy;
4. Severe immunodeficiencies;
5. Colds and exacerbation of chronic pathology;
6. Taking glucocorticoid hormones;
7. Cancer pathology and chemotherapy.

After vaccination, the following reactions of the body are possible:

1. Temperature reaction;
2. Inflammatory changes at the injection site;
3. Headache and muscle pain;
4. Nausea and vomiting;
5. Stomach ache;
6. Rashes;
7. Allergic reactions (urticaria, bronchospasm, drop in blood pressure)

The presence of body reactions to the introduction of a vaccine (with the exception of an allergic one) does not pose a threat. They indicate the triggering of immune mechanisms.

Injectable vaccines have been developed for the prevention of paratyphoid infections. The technique of their introduction involves a course admission: two times with a 4-week interval between injections.

Which doctors should you contact if you have typhoid fever?

An infectious disease doctor deals with the treatment, prevention, observation of convalescents and carriers of typhoid fever. If necessary, related specialists are included in the treatment and diagnostic process. These can be: a surgeon - in the presence of symptoms of an acute abdomen and the need for differential diagnosis, an intensive care specialist - with a progressive aggravation of the patient's condition and multiple organ failure.

Author of the article: Danilova Tatyana Vyacheslavovna | Infectionist

Education: in 2008 received a diploma in General Medicine (General Medicine) at the Pirogov Russian Research Medical University. Immediately passed an internship and received a diploma of a therapist