Plague

Plague (pestis), acute infectious disease manifested General intoxication and characterized by inflammation of the lymph nodes, lungs, skin and other organs. Plague belongs to the group of so-called highly dangerous (quarantine) infections with natural focality. In the USSR dissolved.
Etiology. Pathogen - plague Bacillus with rounded ends, swollen in the middle, in consequence of which is ovoid shape. Painted normal aniline paints; the middle part is painted pale (bi-color). Resistance to environmental exposure is small. Drying, solar light, competition is harmful germs quickly ruin; boiling kills for 1 minute Low temperature stick moves well. The organism can survive long on linen, clothing, contaminated sputum, pus, blood; the long-term remains in the water, or food. In the dead rodents, unless he begins a process of decay (in winter), the wand can remain viable in the next 4-5 months. A solution of 5% of Lysol and 5-10% carbolic acid kill the plague Bacillus for 5-10 minutes, and the corrosive sublimate solution 1 : 1000 for 1 to 2 minutes
Epidemiology. The Keeper of infection in nature are wildly-living rodents (squirrels, marmots, gerbils). Sufficient density and continuity colonies of rodents, the large number of fleas - vectors of infection, the ability simonpedia squirrels and Surkov carry infection in latent form ensures a continuous circulation of the plague pathogen among these rodents. To the plague very sensitive and domestic rats, house mice, common vole, steppe pestrushka and other rodents. Infinitely long storage of the plague pathogen in nature, these rodents can not provide. But this does not exclude the possibility of a powerful epidemic (see) among rodents, especially in the so-called mouse misfortunes, which in turn entails severe epidemic among people. To maintain long-flowing Epizooties in rodents need a high density of population and the large number of fleas on them. These conditions are usually formed only in southern latitudes, such as in the Middle and Far East, where the plague infection among people usually applies synanthropic rats. Seriously, in the receptive to the plague of the camel. In the past often been noted outbreaks of plague among the people associated with the forced slaughter of sick camels. Susceptible to plague foxes, jackals, ferrets do not have much practical value. Infection among rodents distributed mainly transmitted by fleas).
The spread of plague among the people may vector-borne, airborne and contact-household ways. The emergence of the first cases of plague among the people always starts with the bubonic form as a result of vector-borne or contact transmission (the bite of fleas, removing the skin from the patient rodent, cutting camel carcass at slaughter sick animal, and so on). In the further development of the disease is determined and other mechanisms of transmission through infected household items, food and water. If the bubonic form of plague is complicated by secondary plague pneumonia, the patient infection diffuses through coughing, talking. Airborne transmission entails the emergence of primary pneumonic form of plague in which patients massively infect the environment.
Pathogenesis and pathological anatomy. Place the entrance gate infection during the plague in humans can be skin, mucous membranes of the respiratory tract, conjunctiva, rarely infection occurs through the mouth. Accordingly distinguish between skin form of plague, soon passing in skin-bubonic due to the development of regional buboes. Cutaneous form is relatively rare (3-5%). More common bubonic form of plague in which bubo (inflammation of lymph node) is a mandatory feature. The plague pathogen is logged in the node lymph flow and causes inflammation. Primary bubny distinguished from secondary arising hematogenous (by blood) usually later. Hematogenous infection can enter the lungs (secondary pulmonary plague), brain (meningitis), and in some cases lead to sepsis (secondary septicaemic plague). When primary pulmonary plague lung damage tends to be focal character. In severe cases, the inflammatory process captures a percentage or more shares, characteristic serosanguineous exudate. Intestinal form is very rare.


Plague (pestis), acute infectious disease of the group of zoonoses, manifested by acute intoxication and inflammation of the lymph nodes, lungs and other organs.
Currently plague logged in Asia, Africa, North and mainly South America. Europe and Australia is free from the plague.
Etiology
The causative agent H - pestis Bacterium, Pasteurella pestis - polymorphic rod of length 1-3 microns and a width of 0,3-0,7 MK. The ends of bacteria rounded, and the middle slightly inflated so that they are ovoid (egg-shaped) form. Easily coloured aniline dyes, gram-negative. At colouring of the middle part of microbial cells becomes paler than their ends (bi-color), especially when stained with methylene blue and Romanovsky - Giemsa (Fig. 1). Bacteria ovoid shape, with a clear bipolar colors prevail in smears of Pankratov bubo, from the blood and organs of fresh corpses of people and animals.

Fig. 1. Bipolar painted sticks plague from the spleen Guinea pigs (H1200).
Fig. 2. A two-day colony plague microbe on agar (X40).

Modified forms of bacteria (balls, thick thread) are found in smears from festering of Bubnov, from bodies decayed corpses and with the growth on agar with salt. In stained smears from 24-48 hours agar culture detected short sticks (Kokko-types) and sticks placed singly and in groups. Among them there are long winding
thread and spherical (involution) form. In smears from broth culture - sticks of various length, arranged in chains.
Bacteria of a plague not have high mobility, spores do not form, having capsule. On artificial nutrient media education capsules contribute growing at temperature 37 deg, wet and slightly acidic environment, adding to the environment blood, glikokol and cultivation in the atmosphere containing 20-25% carbon dioxide.
The plague pathogen - optional gone anaerobic. Grows well on nutrient media with optimal pH equal to 6.9 to 7.2 at temperature of 25-30 degrees.
Usually grows in the R-form, sometimes in an S-shape. The R-form colonies rough, convex, with brown centre, surrounded by the periphery of the lace edging (Fig. 2); in the S-form - smooth, transparent, without lace zone. Virulent plague germs allocated from infected rodents and humans, as well as from fleas, grow in the R-form.
Bacteria of a plague gelatine and collapsed serum not diluting gelatin; fermented with the formation of acid, glucose, maltose, mannitol and arabinose, not ferment lactose, saccharose and rhamnose. In relation to the glycerol there are two types of plague microbe: glycerinatergto and glycerinated.
The plague pathogen tolerates low temperature, but is very sensitive to heat; when temperature 58° dies within 30 minutes, and at boiling point - within 1 to 5 minutes Sensitive to the action of direct sunlight. Poor stability to action of disinfectants: 3-5% solution of carbolic acid, solution of Lysol, bleach, chlorine, alcohol kill him within 1-10 minutes In the protein environment (bloody sputum, blood, and other) microbes plague, protected from the light and dry, can be stored up to 10-15 days and more and more resistant to disinfectants. For a long time (3-5 months). they persist in the body for fleas. In the environmental objects contaminated with the other flora, quickly die. Sensitive to antibiotics (streptomycin, tetracyclines, and others).
The plague pathogen causes spontaneous disease in animals, mainly in rodents. Other kinds of animals (camels, cats, foxes) and people become infected with plague in contact with rodents or by the bite of infected fleas. Of laboratory animals is very susceptible to plague the Guinea pigs and white mice, less susceptible white rats and rabbits.
The virulence of the plague microbe fluctuates. Virulent strains of the plague microbe contain a particular set of antigens (V & W), they are characterized by resistance to phagocytosis.
They have a very high invasiveness in the body, quickly spread through the lymphatic and blood vessels, breed in the internal organs and cause death with symptoms of sepsis and severe intoxication.
A toxin isolated from the plague microbe different methods, has the properties of endo - and exotoxins. Between virulence and toxigenicity plague microbe direct connection is not established. Cm. also Pasteurella.