Diarrhea Infections in North-Eastern Ukraine: Evolution of Epidemic Process

Background: The significance of some infection sources, pathways of pathogen transmission and etiological structure of diarrhea infections (DI) have changed. Many issues of DI epidemiology are still insufficiently studied, which prevents the organisation of quality epidemiological surveillance and diseases control. Objectives: To study the DI epidemic situation (ES) in NorthEastern Ukraine and to identify the factors that determines the characteristics of epidemic process (EP). Material and Methods: The reports of Ministry of Health of Ukraine (19602018) and Head Statistics Administration of Sumy Oblast (2001-2018) have been used. The biological properties of 40 strains of K. pneumoniae, 50 S. aureus, 40 E. cloacae recovered from the feces of patients with DI have been studied. Results: It has been found that the EP of DI is characterized by a sharp decrease in the incidence of typhoid fever and shigellosis, increase in the incidence of salmonellosis and dominance of DI caused by other specified or unspecified pathogens (SDI and UDI) in the nosological structure (p<0.05). The incidence of DI caused by Klebsiella, Staphylococus, Enterobacters exceeds the incidence of salmonellosis, shigellosis, typhoid fever (p<0.05). Opportunistic pathogens (OP), which are pathogens of DI have antilysozyme activity and adhesion ability, which proves their pathogenic potential. The demographics indirectly affect the incidence of DI. Access to water supply, sewerage, hot water supply is correlates with the incidence of DI. Conclusion: The system of epidemiological surveillance over DI in Ukraine needs improvement by optimisation its information and analytical subsystems aimed at objective epidemiological diagnostics and ES forecasting.


Introduction:
Diarrhea infections (DI) are among the most widely spread infectious diseases in the world. World Health Organisation reports 1.7 milliard cases of DI registered annually in the world 1 . DI incidence in both developing and economically developed countries is quite high 2, 3, 4, 5 .
DI epidemiology, influenced by globalization, migration increase, international tourism on the background of general environmental degradation, decrease of immunological status of the population, strengthening of the pathogenic potential of causative agents has changed. The significance of some infection sources, pathways of pathogen transmission and etiological structure of DI have changed 6,7,8 . Many issues of DI epidemiology are still insufficiently studied, which prevents the organisation of quality epidemiological surveillance and diseases control .

Objectives:
To study the DI epidemic situation (ES) in North-Eastern Ukraine and to identify the factors that determines the characteristics of epidemic process (EP).

Materials and research methods:
The reports of Ministry of Health of Ukraine  and Head Statistics Administration of Sumy Oblast (2001-2018) have been used. The biological properties of 40 strains of K. pneumoniae, 50 -S. aureus, 40 -E. cloacae recovered from the feces of patients with DI have been studied. Antilysozyme activity (ALA) of opportunistic pathogens (OP) was determined using cup-plate technique according to the method of O.V. Bukharin et al. in the range of lysozyme concentration from 5 to 25 µg/ml (the strain Micrococcus lysodecticus(ATCC 10240) was used as a test culture). The strains were considered highly active at lysozyme neutralization if concentration was greater than 25 µg /ml, intermediate level-10-20 µg/ml, lowlevel -5 µg /ml. The maximum value of lysozyme concentration in the medium at which the growth of the indicator strain was still observed was taken as ALA level of the studied cultures 9 . The adhesive properties of OP were determined using the method of V.I. Brilis et al. Adhesion was considered to be zero at average adhesion index from 0 to 1.0, low -at mean value of adhesion from 1.01 to 2.0, average -from 2.01 to 4.0, high -more than 4.0 10 . The epidemiological, microbiological and statistical methods of research have been applied. Statistical processing of the study results have been carried out using computer programmes Microsoft Office Excel 2010, SPSS, 12, Statstica 6. Ethical clearence: Not required Results and discussion: It has been established that during 1960-2018 there have been significant changes in EP of DI. The ES was characterized by the decrease in the incidence of typical intestinal anthroponoses (typhoid fever and shigellosis). Typhoid fever incidence decreased from 7.4 per 100 000 people in 1960 to 0. 3 -in 2002 Since 2003, the cases of typhoid fever in North-Eastern Ukraine have not been registered (Fig. 1). Shigellosis EP in the period of 1960-1975 was marked by the gradual incidence increase from 100.7 per 100 000 people up to 625 per 100 000 people. Starting 1976 there was a decrease to 0.6 per 100 000 people in 2018 on the background of insignificant rises in shigellosis incidence, (Fig. 2).  It is well known that the main risk factors for the rapid spread of DI are poor sanitation and hygiene, low cultural practices of population. The main causes of the cases were microbially contaminated products of dairy industry, public catering establishments, drinking water, as well as poor sanitary and technical state of the kitchen facilities of preschool institutions, gross violations of food technology. The Ministry of Health of Ukraine issued a decree regulating the main principles of sanitary and epidemiological surveillance and anti-epidemic measures in respect of DI in order to improve DI prevention during tense ES, when high incidence of shigellosis, outbreaks of DI were registered 11 . Taking into account the above, it can be assumed that many factors contributed to the decrease in the incidence of intestinal infections (typhoid fever and shigellosis), where a person is the only source of pathogens, and one of them is greater control over compliance with sanitary and hygienic rules, improvement of social and economic living conditions in Ukraine in general and Sumy Oblast in particular. Timely detection of DI pathogens carriers during preventive and periodic medical examinations of employees of food production facilities, continuous state sanitary and epidemiological supervision of compliance with sanitary legislation during procession, transportation, storage and sale of food and food stock; water supply facilities, certainly affected the improvement of ES. Automation of production processes in the food industry and public catering establishments, use of modern equipment allowed excluding people from the technological process, reducing the risk of microbial contamination of food. At the same time, it should be noted that the risk of ES worsening constantly exists taking into account the epidemiology of the abovementioned diseases. Thus, 3-5 cases of typhoid fever are detected annually in foreign citizens or tourists returning to Ukraine from endemic area of typhoid fever. The median incidence of shigellosis in 2011-2018 in the neighboring Kharkiv Oblast is 11.6 times higher and is 18.6 per 100.000 people. On the background of reduced incidence of intestinal anthroponoses, salmonellosis EP was characterized by the incidence increase from 3.6 per 100.000 people in 1960 to 19.3 in 2018 (Fig. 3). The incidence rate of other DI or caused by other specified or unspecified pathogens (SDI and UDI) was high, despite the decrease from 499.4 per 100.000 in 1960 to 132.1 in 2018 (3.8 times) (Fig. 4). In 1995 the decree of the Ministry of Health of Ukraine listed especially dangerous, dangerous and parasitic diseases of human which had to be mandatory registred 14  At lysozyme concentrations of 5 and 10 µg/ml, the level of ALA strains isolated from the feces of the patients with acute intestinal infectious disease varied in the range from 76.0 to 100 %. Even at lysozyme concentration of 25 µg/ml in the feces, the microorganisms demonstrated ALA.
It is well known that the adhesion of microorganisms is a releaser in the development of infectious pathological process. The study revealed the ability to adhesion in (50.8±4.4) % of the studied cultures isolated from the feces of patients with DI (Table 2). Adhesion is inherent in the prevailing number (85,0 %) of K. pneumoniae and in more than one third of S. aureus and E. cloacae isolated from the feces of the patients with DI. It should be noted that the bacteria with low adhesion dominated in the studied strains.
Consequently, OP ability to overcome the immune defense of the macroorganism, to fix on the surface of enterocytes testifies their significant pathogenic potential, because ALA and the adhesion ability are inherent in OP.
In order to determine the social factors that can determine the EP of DI, the demographics and the access to water supply, sewerage, hot water supply were studied in North-Eastern Ukraine (Sumy Oblast). Correlation analysis was carried out to verify the hypothesis that demographics has an impact on the DI incidence. The direct strong correlation between shigellosis incidence and population number, both adults and children (r=0.838, r=0.778 and r=0.872, respectively), the population density (r=0.836); between the incidence of SDI, SDI and UDI and the migration rate of the population (r=0.897 and r=0.736, respectively). Indirect strong correlations were established between the number and density of the population and the incidence of salmonellosis (r=-0.722 and r=-0.721, respectively), SDI ( r=-0.779 and r=-0.779, respectively). That is, if the current trend in demographics remains, when the population decreases from year to year, we should expect a strong increase of both salmonellosis and SDI incidence. Access of the population to water supply, sewerage, hot water supply is a factor that characterizes the level of social and economic region development. The correlation analysis found that in addition to the expected indirect correlation between shigellosis incidence and availability of water supply, sewerage, hot water, there was the direct strong correlation between the availability of water supply and sewerage as well as hot water (table. 5). The abovementioned indirectly points to the issues existing in the services provision for the population, namely, microbially contaminated drinking water. Consequently, the following social (decreased role of a human as an infection source, increased role of animals and soil as OP source; depopulation, less than half of the housing is equipped with water supply, sewerage, hot water supply) and biological (OP demonstrate ALA and adhesion ability) factors have changed EP of DI, namely they decreased the incidence of intestinal anthroponoses (shigellosis, typhoid fever) and increased intestinal zoonoses (salmonellosis) and sapronoses (DI caused by OP).

Conclusions:
1. ES with DI is characterized by a sharp decrease in the incidence of typhoid fever and shigellosis, increase in the incidence of salmonellosis and dominance of SDI and UDI in the nosological structure (p<0.05). 2. The incidence of DI caused by Klebsiella, Staphylococcus, Enterobacter exceeds the incidence of salmonellosis, shigellosis, typhoid fever (p<0.05). OP, which are DI pathogens, have ALA and adhesion ability, which proves their pathogenic potential. 3. The demographics indirectly affects the DI incidence. The correlations have been found between population number and the incidence of shigellosis (r=0.838) and salmonellosis (r=-0.722), SDI (r=-0.779); population density and shigellosis (r=0.836), salmonellosis (r=-0.721), SDI (r=-0.779); migration and SDI and UDI (r=0.736).

4.
The access level to water supply, sewerage, hot water supply correlates with the incidence of DI. Correlations between the abovementioned factors and the incidence of shigellosis (r= from -0.783 to -0.823,), salmonellosis, SDI and UDI (from r= 0.729 to 0.872) have been established. 5. The system of ES over DI in Ukraine needs improvement by optimisation its information and analytical subsystems aimed at objective epidemiological diagnostics and ES forecasting.