SummaryThe aim of the present study is to perform a retrospective analysis of the prevalence of intestinal parasitic infections among the Bulgarian population over the period 2015 – 2017. The study involved all Bulgarians and foreign nationals residing in the country who had been tested for intestinal protozoa and helminths. A total of 23,785 infections have been revealed, of which 17,712 (74.47 %) were helminth and 6,073 (25.53 %) protozoan invasions. Enterobiasis was found to be the most prevalent among patients infected with intestinal helminths (81.75 %), while giardiasis (62.05 %) was the most common among those diagnosed with protozoan infections. In spite of improved living conditions and increasing public health awareness, parasitic diseases in general, and intestinal parasitic infections in particular, still represent a significant part of the overall morbidity in Bulgaria, thus posing a major issue for the public health care system.

Objective: Cystic echinococcosis (CE) is one of the most severe parasitoses, which leads to prolonged disability, frequent recurrences, and even to death. In Bulgaria it is one of the most frequently registered and severe helminthic infection.. The aim of this study is to determine the epidemiological indicators as morbidity, mortality and lethality from CE in Bulgaria for the period 2011-2020, as well as a comparative analysis of morbidity in the country with that of other EU member states. Materials and Methods: The study is a retrospective analysis of confirmed cases of CE, as well as of the deceased from this parasitic disease. Data from several sources were used - the annual analyzes of parasitic morbidity in the country, prepared by the NCIPD, as well as information from the National Center for Public Health and Analysis and the National Statistical Institute. Statistical methods were used to calculate morbidity and mortality rates Results: From 2011 to 2020, a total of 2626 cases of CE are registered in Bulgaria (95% Confidence Interval: 263 ± 3.16), with an average incidence for the period of 3.7%₀₀₀ (95% CI: 3.65 ± 0.357). The registered primary cases are 2336 (95% CI: 233.6 ± 3.03) in total and 290 (95% CI: 29 ± 1.04) are recurrences. Cystic echinococcosis is comparatively more prevalent in women than in men, respectively 1397 (95% CI: 139.7 ± 2.39) and 1229 (95% CI: 122.9 ± 2.14) registered cases for the period and for morbidity values are 3,7%₀₀₀ (95% CI: 3.71 ± 0.36) to 3,5%₀₀₀ (95% CI: 3.53 ± 0.343). The most affected is the age group 20–59 years, i.e. people of active working age. The number of affected children aged 1 to 19 (509 cases) is relatively high, which indicates an active transmission of the parasite. During the studied period deceased patients due to echinococcosis are 65 of whom 38 men and 27 women. The average mortality and the lethality are respectively 0.09%₀₀₀ (95% CI: 0.09 ± 0.103) and 2.49% (95% CI: 2.49 ± 0.405). Conclusion: The results show a reduction in examined indicators regarding cystic echinococcosis compared to data for the 1990s and the studied from us period, but these values are still higher than the established EU averages.

Background: Pneumocystis pneumonia (PCP) commonly affects immunocompromised individuals, whereas in immunocompetent persons, it occurs relatively rarely, and in most cases the Pneumocystis infection is detected as an asymptomatic colonization. The present study aimed to establish the prevalence of Pneumocystis jirovecii infection in human hosts with different immune status (immunocompromised and immunocompetent), using molecular diagnostic methods, and to compare their diagnostic value with that of classical staining methods. Methods: We used the collected to this moment data from a prospective study on the prevalence of pneumocystosis among the Bulgarian population. Clinical specimens (including throat secretion, induced sputum, tracheal aspirate, and bronchoalveolar lavage collected from 220 patients suspected of PCP (153 immunocompetent and 67 immunocompromised patients) were examined with staining microscopic methods and real-time PCR for detection of P. jirovecii. Results: DNA of the pathogen was detected in 38 (17%) specimens (32 immunocompromised patients and 6 immunocompetent subjects). From all 220 clinical samples examined by staining methods, only in five (2%) P. jirovecii cysts were detected by the Gomori's stain. All patients with PCP were treated with trimethoprim-sulfamethoxazole, but in ten of them (HIV- positive patients) the disease was with fatal outcome. Conclusions: This study is the first for the country including the main available laboratory methods for diagnosis of human pneumocystosis in Bulgaria. Regarding the etiological diagnosis of PCP, in our study the sensitivity of real-time PCR was higher compared to the staining methods. The choice of a method for sample collection and examination has an important role in the efficiency of the laboratory diagnostics.

Enterobius vermicularis is an intestinal parasite with a cosmopolitan distribution and the disease which causes (enterobiasis) is one of the most common helminth infection worldwide. According to literature data it affects nearly 1 billion people and is found in various socio-economic groups. Everyone is susceptible to infection, but children are more often affected than adults due to their poorly developed hygiene habits. Patients with enterobiasis are often reinfected which together with the high endurance of the pinworm eggs in the environment contributes to the difficult control of the disease. In recent decades, a number of studies have been conducted on the genotypic characteristics of the nematode, including sequencing, which accumulates data on phylogenetic varieties of the species to improve the diagnosis and control of this infection in humans.The available data reveal influence of E. vermicularis on the local immunity of intestinal mucosa in infected individuals, but these data are scarce and contradictory and do not clarify the significance of this influence on the clinical manifestations of the disease. Additional studies are needed to define the relationship of this effect with the clinical symptoms of the disease.

The aim of this report is to review and assess the dynamics of parasitic diseases in Bulgaria during 2020-2021. Materials and methods. The analysis is based on the annual reports of the Regional Health Inspectorates (RHIs) about the cases of registered parasitic diseases among humans in the country and on data from the National Reference Laboratory “Diagnosis of Parasitic Diseases” at the National Centre for Infectious and Parasitic Diseases (NCIPD), Sofia, for all examined cases. Results. For the study period a total of 1,225,485 individuals were examined in the country’s parasitological laboratories at the Regional Health Inspectorates, stand-alone medical diagnostic laboratories and at the National Center for Infectious and Parasitic diseases (NCIPD), of whom 19,509 (1.59%) were diagnosed with a positive result for parasitic pathogens. Among the zoonotic helminth infections with local transmission, a special attention deserve cystic echinococcosis and trichinellosis as the incidence of these parasitoses in Bulgaria is the highest among the European member states. The prevalence of ascariasis and trichuriasis in the country have been reduced to such an extent that they do not represent a public health danger any more. Data regarding community acquired giardiasis and hymenolepiasis can be interpreted in a similar way, while for enterobiasis, an increasing prevalence among both children and adults has been observed in recent years. Although imported parasitic pathology is relatively limited in volume, Bulgarian climate and fauna are quite favorable for local transmission of a number of imported parasitic diseases. Control measures regarding this pathology consist in the timely detection and removal of infection sources. Conclusion. In Bulgaria, there is a well-established system for surveillance and control of human parasitic diseases, which allows the acquisition of comprehensive information including patients demographic data and characteristics of the causative agents. This enables the monitoring of parasitic pathology among the population and an accurate assessment of the the endemic-related risks.