Questions to control the knowledge

1. Etiology, pathogenesis, anatomic pathology, complications and outcomes of typhoid, dysentery, amebiasis, salmonelloses.

2. Etiology, pathogenesis, anatomic pathology, complications and outcomes of cholera, plague, anthrax.

Terminology

Typhoid, bacteraemia, bacteriocholia, ileotyphus, coloty-phoid, cerebriform swelling, necrosis, formation of ulcers, clear ulcers, healing of typhoid granuloma; wax-like necrosis of abdominal muscles, typhoid sepsis, salmonelloses, the most acute gastroenteritis, «home cholera», paratyphoids A and B; dysentery, catarrhal colitis, fibrinous colitis, ulcerative colitis, chronic dysentery; cholera, profuse diarrhea, choleraic enteritis, choleraic gastroenteritis, algid period, exsicosis, choleraic typhoid, postcholeraic uremia.

VIRAL DISEASES

Viral diseases are those caused by viruses. The nature of viral infections differs from that of infectious diseases.

The peculiarities of viral diseases are:

1. Being highly contagious, viruses cause epidemics and pandemic.

2. The variety of viruses determines the involvement of specific cells due to the virus trophism. Trophism is determined by the character of the cell receptors.

3. The course of the disease depends both on the type of the virus and the reactivity of the macro-organism and can be acute, chronic, slow.

4. The morphological manifestations of cell-virus interrelations are:

• cytolytic effect of the virus on the cell (grippe);

• formation of inclusions in the cell (grippe, adenovirus infection);

• integration of the virus and the cell genome without considerable destruction of the cell (hepatitis B, HIV infection);

• proliferation of target cells (smallpox);

• giant-cell transformations (measles).

ACUTE RESPIRATORY VIRAL INFECTION

(ARVI)

Some years ago it was termed acute catarrh of the upper respiratory tract (season catarrh). The term denotes a group of acute inflammatory diseases caused by pneumotropic viruses (grippe, paragrippe, adenovirus infection, respiratory sincitial virus, rhinovirus, reovirus). Each of the above diseases is associated with different serological strains of viruses. RNA containing viruses prevail. Grippe viruses are indeed 3 types of RNA containing viruses (for the first time the virus was isolated in 1933). At present, we know 3 inde-pendent types (A, B, C). Each of them has its own subtypes (Al, A2, A3 and so on). Paragrippe virus (isolated in 1965 by Chenok), respiratory sincitial virus (1956—1957, Morris and Chenok), rhinovirus, rheovirus are also RNA containing. Adenovirus is a DNA containing one.

At present differential diagnosis of ARVI is not difficult. Immunomorphological study with antisera to the definite strain of viruses is performed in the smears from the mucous membrane of the upper respiratory tract or in the tissue (if it is autopsy material). In this case bright fluorescence is seen under the microscope.

The source of infection in all ARVI is a sick person. The infections spread by coughing and breathing.

According to WHO, ARVI is the main cause of disease and death in the world.

Grippe (influenza, or flu for short) is caused by RNA-containing viruses of 3 serological types (A, B, C).

The incubative period is 2—4 days. The virus invades the bronchial and alveolar epithelium and endotheliocytes of the capillaries and multiplies there causing primary viremia. The epithelial cells die, the virus leaves them and invades ones more the bronchial and alveolar epithelium. At this stage acute bronchitis or tracheitis develop. These are the first clinical signs of the disease. The development of the virus in the cells causes degeneration, necrosis and desquamation of the bronchial epithelium which in turn causes secondary viremia. Its manifestations is vasoparalytic action (plethora, stasis, hemorrhage) and immune-depressive action (phagocytosis inhibition, chemo-taxis, etc.) which contributes secondary (often bacterial) infection.

Pathology. Slight, mild and severe grippe are distinguished.

Slight grippe is characterized by the lesion of the mucous membrane of the upper respiratory tract (edema, hyperemia, seromucus discharge). These are microcolonies of the virus, they also can be determined with immunomorphological method. The duration of the disease is 5—6 days, the disease ends with recovery.

Involvement of not only the upper respiratory tract but also the mucous membrane of the bronchi,

bronchioles and lungs characterize mild grippe. Serous hemorrhagic inflammation is present in the trachea and bronchi, it is often accompanied by the foci of necrosis. Desquamation of the bronchial epithelium causes atalectases and emphysema in the lungs. Grippe pneumonia develops against a background of the atelectasis and emphysema. The alveoli are filled with serous exudation with alveolar macrophages, desquamation of alveolocytes, erythrocytes, leukocytes is observed. Interalveolar septa are thickened due to proliferation with lymphocytes. The duration of the disease is 3—4 weeks.

The large variegated grippe lung characterizes severe grippe.

Severe grippe may be of two types.

The first type develops due to marked intoxication. Besides serous hemorrhagic bronchitis and pneumonia, hemorrhagic lung edema may develop. Hemorrhage to the brain and internal organs develop. The patients die on the 4th—5th day of hemorrhage to vital centers and of acute respiratory and cardiovascular insufficiency.

The second type is pulmonary complication (large variegated grippe lung).

Grippe encephalitis, serous meningitis, brain edema, trunk dislocation develop in the brain. Obliterating bronchitis, bronchiolitis, bronchoectasis, pneumofibrosis and other chronic lung diseases develop in the lungs. Degeneration and inflammation

in the nodes of the vagus and sympathetic nerves cause neuritis.

The death is caused by intoxication, cerebral hemorrhages, brain edema, brain trunk dislocation, pulmonary complications (pneumothorax, empyema), cardiovascular and pulmonary insufficiency.

Paragrippe is caused by 4 types of RNA containing viruses. The disease is characterized by upper respiratory tract involvement and moderate intoxication. The pathology of the disease resembles slight grippe.

The characteristic signs are tracheal and bronchial epithelium proliferation, appearance of polymorphic cells with one or several picnotic nuclei. Soft tissue edema in the throat is marked. False croup may develop.

Complications are secondary infection, bronchopneumonia, asphyxia, angina, sinusitis, otitis.

The death is caused by asphyxia and pulmonary complications.

Adenovirus infection (AVI) is caused by DNA containing adenovirus. This is characterized by invasion of the upper respiratory tract, lymphoid tissue of the intestine, abdominal lymphatic nodes as well as conjunctivitis.

The course may be slight and severe.

Slight AVI is characterized by acute rhinolaryn-getracheobronchitis, acute pharyngitis, conjunctivitis and regional lymphadenitis. Hyperemia, edema,

petechial hemorrhages, lymphohistiocyte infiltration, epithelium desquamation are observed in the mucous membrane of the upper respiratory tract. Adenovirus pneumonia may occur in children under 1 year.

Severe AVI is caused by generalization of the virus and secondary infections. In generalized infection, the viruses multiply in the epithelium of the intestine (diarrhea), kidneys, liver, pancreas, ganglious cells of the brain with development of inflammation and hemorrhages. Secondary infection is characterized by suppuration and sepsis.

Complications: otitis, sinusitis, angina, pneumonia due to the secondary infection.

The cause of death is pneumonia, sepsis.