Epidemiology of dysentery in Dagestan]

Analysis of material on bacterial dysentery and other acute intestinal infections morbidity in the Dagestan ASSR for a period of 15 years showed high morbidity level and its variations, with reduction and elevation in individual years, and the leading role played by Shigella flexneri among the causative agents of dysentery. The greatest incidence of dysentery was revealed among children aged under one year and between 1 and 2 years. A high bacterial dysentery incidence was recorded in Dagestan throughout the whole year. However analysis of the seasonal dysentery curve showed the beginning of elevation in July, reaching the maximum in August, and lasting four months with a decline beginning in October. The persisting activity of the water route of dysentery transmission in the Dagestan ASSR requires particular attention to the organization of good-quality water-supply to the population of the republic.     

Epidemiology of bacillary dysentery in Algeria. I. The epidemiological aspects of dysentery in Algeria

Bacterial dysentery plays an important role among infectious diseases in Algeria. A tendency to the growth of the morbidity rate has been observed. Dysentery is irregularly spread in different zones of the country. The highest morbidity rate is registered in the Sahara zone and in the eastern part of the country. The morbidity rate among the urban population is higher than among the rural population. S. flexneri prevail in the etiological structure of dysentery infection. Of all age groups, the highest morbidity rate is observed among children during the first 2 years of life. In recent years lethality varies between 2.9% and 7.5%. Patients are hospitalized mainly on the basis of clinical symptoms.     

Analysis of the seasonality of acute intestinal diseases with regard to the detection of dysentery by antigen indication

Coincidence in the seasonal changes of the registered morbidity in dysentery and in other acute intestinal diseases is observed. The occurrence of Shigella antigens, detected with the use of erythrocyte diagnostic reagents, in the excreta of patients with the clinical diagnosis of dysentery and patients with other acute intestinal disease has a seasonal character, its peak coinciding with the period of increased morbidity in bacteriologically confirmed dysentery. The correction of monthly morbidity levels in dysentery and in other acute intestinal diseases with due regard for the proportion of Shigella antigens in the findings, made in the groups of patients with the clinical diagnosis of dysentery and with the diagnosis of other acute intestinal diseases for the corresponding month, has revealed that the actual morbidity in other acute intestinal diseases has a less pronounced seasonal character in comparison with the registered morbidity. This fact substantiates the statement that in the group of patients with other acute intestinal diseases a large proportion of such diseases is, actually, of a noninfectious nature.     

The results of a seroepidemiologic study of Newcastle dysentery

Differences in the monthly distribution in the number of seropositive individuals among children and adults in years with different intensity of the epidemic process have been revealed. Immunity in cases of dysentery caused by S. newcastle reflects the yearly and seasonal activation of the epidemic process in this Shigella infection both in children and adults, the seroconversion characteristics observed in the year of a high morbidity level being a more objective criterion indicating the beginning of the activation of the epidemic process in dysentery caused by S. newcastle in comparison with the commonly registered morbidity level.     

Manifestations of the cyclic nature of the epidemic process in dysentery

Different forms of dysentery, especially those caused by Sh. sonnei and Sh. flexneri, have been found to differ considerably in their cyclic recurrence. The development cycles of the epidemic processes of dysentery have an objective character, occur in the presence of any tendencies in the morbidity rate, and depend on the natural factors. Thus, the cycles of increase and decrease in morbidity are 3, 6, 9, 12 years for dysentery caused by Sh. sonnei and 6, 7, 8 years for dysentery caused by Sh. flexneri.     

Relation of the epidemiological characteristics of dysentery to the biological properties of the causative agents

The main forms of the epidemic manifestation of dysentery induced by different causative agents in 1975-1980 were revealed. During these years the cases of dysentery induced by Shigella sonnei, biovar II, were found to prevail (82.0-90.1%) both at the periods between epidemics and at the periods of the seasonal rise of morbidity. The experimental infection of white mice by intraperitoneal inoculation revealed no relationship between the seasonal rise of morbidity in dysentery and the virulence of its causative agents.     

Specific prophylaxis of shigellosis

A high level of shigellosis morbidity requires new approaches to the control of bacterial dysentery. According to modern concepts, the outbreaks of Shigella infections are linked both with less intensive epidemic control measures and the objective cyclic character of the epidemic process. In this connection great importance is attached to the development of vaccines for the immunization of high risk groups in territories with unfavorable epidemic conditions and in zones of military conflicts, as well as children of school and pre-school age, who mostly determine seasonal rises of shigellosis morbidity. In this article the data describing new approaches to the creation of new live enteric vaccines on the basis of the knowledge of the genetic control of microbial pathogenicity and the regulation of its expression are presented. Attenuated Shigella mutants, created by different authors and having good prospects to be used for the development of vaccines, are characterized.     

Seeding efficiency of the causative agent of dysentery as an index of the intensity of the epidemiologic process]

A study was made of the character and extent of interrelationship between the indices of dysentery morbidity and the indices of the seeding efficiency of dysentery bacilli persons who did not apply for medical aid. Establishment of such interrelationship permitted the authors to suggest the use of a more objective index of the seeding efficiency of dysentery bacilli, along with morbidity indices, for the assessment of the intensity of the epidemic process in this infection. On the basis of investigations carried out the authors came to the conclusion that a tendency to the increase of dysentery incidence the last few years chiefly bore a "statistical" character and was due to the improved detection of patients and carriers.     

Epidemiological analysis of hepatitis A morbidity

A retrospective epidemiological analysis of hepatitis A morbidity for many years among the population of two neighboring towns in the temperate climatic zone of the USSR has revealed the cyclic character of the epidemic process without a perceptible decrease in its extensiveness and has determined the high-risk groups, as well as the beginning of the seasonal rise of morbidity in these groups. The results of the study indicate that different levels of hepatitis A morbidity and risk groups can be observed in these two neighboring towns. At periods of a lower morbidity level the high-risk group embraces schoolchildren, and when morbidity is at a higher level the risk group includes schoolchildren and preschool children in organized groups. Among the latter the morbidity level is influenced by factors acting all the year round and among school children, by seasonal factors. The beginning of the seasonal rise of morbidity falls on August, while in organized groups of children of preschool age the seasonal rise of hepatitis A morbidity begins 1-1.5 months later. All prophylactic measures for controlling hepatitis A should be carried out with due regard to these features of the epidemic process.     

Use of data on Shigella contamination and immunity indices for studying the activity of the epidemic process in dysentery

The comparative study of the monthly distribution of characteristics indicating the levels of contamination with Sh. sonnei and Sh. flexneri separately, as well as the seasonal dynamics of the corresponding antibodies, in the years with high and low morbidity levels has been made with the use the indirect hemagglutination test. The possibility of using these characteristics for the evaluation of the activity of the epidemic process in dysentery caused by Sh. sonnei is shown.     

Characteristics and trends in the development of an epidemic process of Sonne and Flexner dysentery among preschool children

The results of studies indicate that the morbidity rates of dysentery among children attending preschool institutions and children brought up at home converged in recent years. This phenomenon was most pronounced among children of the kindergarten age group. At the same time dysentery caused by Sh. sonnei and Sh. flexnery produced a higher morbidity rate among children attending nursery in comparison with that among children of the same age group brought up at home. Group infections in preschool institutions were caused by Sh. sonnei in 89.1% of cases and by Sh. flexneri in 10.9% of cases. Outbreaks due to the transfer of infection through everyday contacts were observed only in dysentery caused by Sh. sonnei, constituting 71.4% of the total number of dysentery outbreaks.     

An analysis of the dysentery epidemic process in Blagoveshchensk

The retrospective analysis of dysentery morbidity in Blagoveshchensk for the period of 1960-1987 was made. The regularities linking general natural and biological factors triggering the epidemic process with dysentery morbidity among the population are emphasized. The study revealed that under the conditions of Blagoveshchensk dairy products were of major epidemic importance among factors contributing to the transmission of dysentery. Such a factor as flies also had a definite influence on the epidemic process of dysentery. Another risk factor was drinking water which influenced the epidemic process both directly and indirectly through dairy products and, probably, other foodstuffs. Reliable correlation between dysentery morbidity among the population and the quality of dairy products, tap water and the number of flies was established.     

Data to substantiate the early immunological diagnosis of dysentery]

The interaction of the whole blood from patients with dysentery and gastrointestinal diseases of non-dysenteric etiology, with the causative agents of dysentery, Sh. sonnei and Sh. flexneri, and saprophytic, staphylococci labeled with radioactive isotopes was studied in vitro. In dysentery an increase in the capacity of the blood for Shigella fixation was observed from the beginning of the disease. During the 1st week of the disease this reaction was strictly specific and accompanied by a decrease in the fixation of staphylococci, but later the reaction became relatively specific. An increase in Shigella fixation occurred considerably earlier than immune antibody formation, as revealed by the indirect hemagglutination test. This research substantiates the possibility of an earlier immunological diagnosis of dysentery as compared with the serological methods.     

Population migrations and the epidemic process of Flexner and Sonne dysentery

Analysis of the materials from the Khabarovsk Territory for the representative period of 25 years (1956-1980) revealed the influence of the migration of the population on the level and dynamics of morbidity in different kinds of dysentery, Flexner's dysentery shown to occur more frequently than Sonne dysentery. Intensive migrations increase the proportion of susceptible persons among the population, thus facilitating the formation and circulation of Shigella strains with pronounced virulence.     

Nature of the epidemic process in Sonne and Flexner dysenteries and the causes of its induction

A comparative study of the epidemic process in Sh. sonnei and Sh. flexneri dysentery in different regions of the USSR revealed that the morbidity level of Sh. sonnei dysentery changed simultaneously in the regions under study at intervals of 2-3 years. Sh. flexneri dysentery showed morbidity rises occurring at intervals 6-8 years, and their occurrence did not coincide with the periods of elevated morbidity in Sh. sonnei dysentery. The data obtained in the cohort analysis and in the study of recurrent morbidity suggest that Sh. flexneri dysentery produces more pronounced postinfection immunity than Sh. sonnei dysentery, and the immunological factor probably affects the dynamics of the epidemic of these Shigella infections.     

Grigor'ev-Shiga dysentery: a new epidemic threat. Its global tendencies and features of its spread

In this article, based on the data contained in literature, the development of the pandemic of Grigor'ev-Shiga dysentery, which began in 1960-ies, is followed. The stages of the formation of three powerful hyperpandemic foci in Central America, South-East Asia and Central Africa are characterized. The characterization of the epidemiological features of the spread of this disease and its clinical distinction are presented. The biological properties of the causative agent, and in particular its multiple medicinal resistance facilitating the spread of the disease throughout the world, is considered. The stable character of the foci of infection in developing countries, which actually present a threat also for this country, is pointed out. For this reason, the epidemiological surveillance on Grigor'ev-Shiga dysentery should be drastically strengthened.     

Effectiveness of social hygiene and organized preventive measures in dysentery in preschool institutions]

The work presents the data on the development and realization of the complex of social and hygienic, as well as organizational and preventive measures for dysentery control at institutions for children of preschool age in one of the regions of our country. This complex comprises the improvement of "epidemiological" knowledge of the staff, preventive orientation in the work of the epidemiological section of the local Sanitary Epidemiological Station, the spread of sanitary and hygienic knowledge children and in their families, the improvement of material and technical equipment of children's institutions. The complex proved to be highly effective: at institutions for children of preschool age morbidity -ate in dysentery decrease 4--5 times, and its specific falue dropped from 40% to 5.4%, the frequency of positive results given by tests for the presence of intestinal microflora in washings from various objects decreased more than 25 times. Morbidity rate at institutions for children of preschool age decreased 4--5 times as compared with that among children not attending such institutions. The above data suggest the necessity of introducing this experience in other regions of our country.     

Indicators of spontaneous and stimulated nitroblue tetrazole test of polymorphous-nuclear leucocytes in acute dysentery patients

140 healthy individuals and 93 sick with acute dysentery were subjected to an examination by spontaneous and by bacterial preparations stimulated reaction with nitroblue tetrazole (NBT test). Indicators in healthy persons were normal in the spontaneous, and increased in the NBT test, stimulated by bacterial preparations. Indicators of the spontaneous NBT test in patients with acute dysentery were raised with a maximum in the period of early convalescence. Stimulation by a live shigella culture--the dysentery vaccine--revealed by means of Sonne diagnostic high, and when endotoxin from Serratia marcescens and dysenterin was used as an inductor, mild indicators of NBT test activity. When a polyvalent agglutinating dysentery serum was used as a stimulator, the activity increased considerably, and a simultaneous use of serum and vaccine had an inhibiting effect on the indicators of the stimulated NBT test. The obtained results testify the sufficient high reserve possibilities of leucocytes towards complete phagocytosis and the efficiency of the NBT test, stimulated by bacterial preparations for the study of functional and metabolic activity of leucocytes in the process of acute bacterial dysentery.     

The manifestations of an epidemic process of typhoid infection in Moscow

The work deals with the results of typhoid morbidity in Moscow for the period of 1980-1988. The morbidity rate varied from 0.98 to 0.17 cases per 100,000 of population with a tendency towards decrease. In the structure of morbidity local cases accounted for 46.8% and cases of infection contacted outside Moscow accounted for 53.2%. The morbidity level was low throughout the whole territory, only in two districts morbidity rate was significantly higher (P = 95%) than the average morbidity rate in the whole of the city. In the group of local cases morbidity had no pronounced seasonal character, in contrast to cases due to infection contacted outside the city which were mostly registered in summer and autumn. Persons aged 21-30 years were found to be the most affected age group. The general factors, and not the contact route, are supposed to play the main role in the realization of the mechanism of infection transfer. Under modern conditions, some manifestations of the epidemic process of typhoid infection can be detected only at the level of the whole city, or even the whole country.     

The definition of the forms of the epidemic process in intestinal infections]

A method for the identification of the forms of the epidemic process in dysentery (annual, seasonal and outbreak forms) has been worked out. The method is based on the calculation of the upper limits of annual and seasonal morbidity from the data on the period of several years with the use of the formulae of binomial distribution, serving as the mathematical model of alternative random values, such as morbidity. The comparison of actual morbidity for each year of the analyzed period with the upper limits of annual and seasonal morbidity helps identify the form of the epidemic process.