Typhoid and paratyphoid A and B
Epidemiology / / August 12, 2017
Typhoid and paratyphoid A and B - acute infectious disease of bacterial origin from the group of intestinal infections.There are in the form of sporadic cases of group diseases and, less commonly, outbreaks.
Etiology The causative agents of typhoid, paratyphoid A and B are in the vast Salmonella group.As they are indistinguishable morphological properties.Differentiation is carried out by their biochemical and serological properties.The causative agent of typhoid fever by specific phages can be divided into a number of phage types.
All three of the pathogen is quite resistant in the external environment.Thus, in the soil, depending on the number of features (.. The structure, moisture, temperature, pH, etc.) they survive a few days to 2-3 months in feces in experimental conditions - from 1-3 days to several weeks,water depending on the influence of different factors - from several days to 2 weeks or more, in the sludge pond - several months in the ice can overwinter in food
to disinfectants used in the usual concentrations, pathogens typhoid and paratyphoid unstable.In the process of disinfecting is necessary only to consider the protective properties of the medium in which pathogens are, and to withstand exposure adopted.
Pathogens typhoid and paratyphoid successfully cultivated in the laboratory practice applied in nutrient media (selenitovaya environment Müller Wednesday, Wednesday and Levin et al.).
One of the important properties of pathogens typhoid and paratyphoid is a tropism for lymphoid tissue and intracellular multiplication.
incubation period of typhoid fever lasts 14 days on average, often hesitate in the direction of shortening to 7 days, and in the direction of elongation up to 21-29 days.When paratyphoid average incubation period lasts 8-10 days and may be shortened to 3 days.
after diseases immunity persists for a long time.Recurrent disease among recover found in 2.2% of cases.
source of infection of typhoid fever and paratyphoid sources of infection are sick and carriers.Dangerous for the patient in different periods of the disease varies.The incubation period the infected person is practically no danger to others.
dangerous for the patient increases as the disease progresses.During this period, the pathogen is released from the body in different ways.In repeated studies, it is found in the feces of almost all patients, in 30-50% of cases - in the urine;more than 70% - in the milk, and a number of other objects (sweat, the contents of the throat, nose and throat).
Most recover exempt from the pathogen in the first 1-2 weeks and in the next 2-3 months.Approximately 3-5% recover remain carriers for a long time, and some - for a lifetime (chronic carriers).
pathogen from the body carrier is allocated is not constant, and there is intermittent selection.To a large extent it appears to be associated with the exciter frequency of receipt of breeding sites in the body (liver, spleen, bone marrow, kidneys and others.) Into the intestinal lumen.Detection and neutralization of media is very difficult.Therefore carriers compared with patients, and plays a key role in the spread of infection.
epidemiological role of chronic carrier is fully dependent on the observance of rules of personal hygiene.Particularly serious consequences are observed in cases where the working medium of the character comes into contact with food.More dangerous as carriers that produce the pathogen in the urine, since urine is made more often than defecation."Healthy" carriers, which include people who have had clinically established form of typhoid fever, due to the short duration of the carrier state have limited epidemiological significance.
infection From the body of the patient and the causative agent of the carrier is excreted in feces, urine and other excrement, and it penetrates the body of another person with food and water.In other words, typhoid, paratyphoid diseases, as well as others, intestinal infections, characteristic fecal-oral mechanism of infection.The factors involved in transmission, are manifold.Typhoid fever and paratyphoid fever are spread through water and food contaminated hands, objects of household environment (dishes, towels, etc..) And flies.Intensity of infection each of the three ways to transfer (water, foods, infection in the home) varies widely.It is very diverse epidemiology of typhoid, paratyphoid infections.
for typhoid and paratyphoid characterized by widespread.these infections diseases, though not uniformly found in all climatic zones of the world, wherever there are human settlements.However, the geographical distribution of paratyphoid A there are some features: This form is more common among people of Eastern, Central and Southern Asia.
Although ubiquitous, typhoid and paratyphoid never, even in the most difficult periods of the epidemic of the past, not received the pandemic spread, cholera and other infections.This pattern is, on the one hand, determined by the duration of the incubation period and the beginning of a massive release of microbes at a time when patients are in most cases are in the hospital, on the other hand - the lack of universally conditions for the spread of infection through food and water.
typhoid and paratyphoid peculiar kind of "endemic" t. E. The ability for a long time held in a particular area, usually in certain localities.Therefore, a high incidence in the district or other administrative unit is usually determined not universal distribution of typhoid and paratyphoid, and registering them in a limited number of localities.Such statistical endemic unlike true endemic, inherent diseases with natural foci, primarily depends on the defects in the water supply.As the domestic and foreign experience, streamlining supply and purification of the territory in a short time has a beneficial effect on the incidence of typhoid and paratyphoid: it begins to decline rapidly and receives sporadic.
Unlike water foods although affect the incidence, but at the expense of their typhoid-parathyphoid infection more or less extensive territory for a long time are not kept.This is due to the fact that any food pathogens can enter periodically, and contamination of food in a short time is realized in certain populations.The exceptions are milk and dairy products, especially from individual farms.If you have a carrier at the thrush cases of typhoid fever among certain population groups can take a protracted nature.However, due to milk and milk products typhoid-paratyphoid diseases are held in the area for a limited time.In the end, unable to identify the cause of disease, and its removal entails the termination of the epidemic process.
Household and mouse transmission factors are not able to hold as long typhoid and paratyphoid at any significant level.
confinement of typhoid and paratyphoid certain settlements greatly facilitates the fight against these infections.Thus, it is possible to concentrate all efforts on certain areas and not wasting manpower and resources, to achieve the best results in the fight for the reduction of morbidity.
important feature of typhoid and paratyphoid is seasonality.The duration and intensity of seasonal rise of morbidity in different locations vary.In the European part of the rise in the incidence observed for 3-4 months.In the republics of Central Asia and Transcaucasia seasonal rise stretched to 6-7 months.In contrast, in many areas against the background of a sharp decline in the incidence of seasonal upgrades its virtually non-existent.Therefore, you need to carefully study the causes of seasonality in specific conditions and take measures to address the factors that cause it
From what has been said above, clearly it implies that the incidence of typhoid and paratyphoid ultimately determined by the factor being infected.It is no accident that the low level of sanitary and municipal improvement and deterioration of his background in the social upheaval clearly impact on the spread of these infections.
for typhoid and paratyphoid in accordance with the three transmission paths characterized by three types of epidemic process: water, food, and household.