Vector-Borne Infections in Bulgaria

Bulgaria is an endemic country for Lyme borreliosis and Crimean-Congo hemorrhagic fever (CCHF). Sporadic cases of tick-borne encephalitis (TBE) and West Nile virus (WNV) encephalitis have been also reported. The reported incidence of Lyme borreliosis in Bulgaria is about 6/100,000 population. Two peaks in the seasonal distribution of cases and more frequent presentation of neuroborreliosis than of Lyme arthritis appear to be characteristics of Lyme borreliosis in Bulgaria. Borrelia afzelii is highly prevalent in Bulgarian Ixodes ricinus ticks. With sporadic cases or small outbreaks, CCHF appeared every year since the 1950s. For the last 10 years, a total of 60 CCHF cases were officially recorded. There is a tendency for CCHF to spread in previously non-endemic areas. The strains causing CCHF in the country belong to lineage Europe 1. A mean of 3.7% CCHF seroprevalence among the Bulgarian population is established. Both Europe 1 and Europe 2 CCHF virus lineages are present in ticks in Bulgaria. Tick-borne encephalitis (TBE) is very unusual. Only a few cases of TBE have been detected. Overall seroprevalence of 0.6% for TBE virus was found in humans. In 2015, a few WNV human cases were detected caused by lineage 2. Overall WNV seroprevalence in human population in the country is 1.5%

Infekcija virusom Zapadnog Nila s neurološkim poremećajima: prikaz slučaja i kratak pregled stanja u Bugarskoj

A case of a 66-year-old man with West Nile neuroinvassive disease manifested with fever, weakness, fa-tigue, consciousness disorders and underlying diabetes mellitus type 2 and cardiovascular diseases is pre-sented. Laboratory data showed elevated erythrocyte sedimentation rate and fibrinogen. Serological tests revealed West Nile virus specific antibodies of class IgM and IgG in serum. West Nile virus RNA was de-tected in urine sample. Supportive therapy was applied.Prikazuje se slučaj 66-godišnjeg bolesnika s neuroinvazivnom bolešću Zapadnog Nila koja se manifestirala grozni-com, umorom, poremećajem svijesti uz osnovnu bolest dijabetesa tipa 2 i kardiovaskularnom bolešću. Laboratorij-ski podaci pokazali su povišenu sedimentaciju i fibrinogen. Serološki testovi utvrdili su protutijela specifična za virus Zapadnog Nila klase IgM i IgG u serumu. Virusna RNA otkrivena je u uzorku mokraće. Primijenjena je suportivna terapija

SARS-COV-2 SEROSURVEY AMONG BULGARIAN HEALTHCARE WORKERS BEFORE AND AFTER VACCINATION

Background: In the response to the current COVID-19 pandemic caused by the novel SARS-CoV-2, one of the groups at higher risk were healthcare workers (HCWs), especially those who worked on the frontline. The presence of SARS-CoV-2 specific IgG antibodies (seropositivity) in certain populations provides better understanding of virus circulation and transmission. Our aim was to study the seroprevalence rates of anti-SARS-CoV-2 antibodies among a group of healthcare workers before and after vaccination/COVID-19 infection. Material and Methods: We determined the presence of SARS-CoV-2 specific IgG and IgA antibodies against S-antigen of by ELISA method. In this study, we enrolled 74 healthcare workers and three months later, 48 of the participants were followed up. At the baseline, none of the participants was vaccinated or had suffered COVID-19.  Results: SARS-Cov-2 specific IgG antibodies were found in 32.4% of the participants. Higher prevalence of class IgA antibodies – 44.6% was detected. All samples that were IgG seropositive were also positive or borderline for IgA antibodies. Overall, virus-specific antibodies were not detected in 40.6% of HCWs in the group. During the follow-up (after vaccination and/or COVID-19 infection) high rates of both IgG and IgA seroprevalence were established. SARS-C0V-2 specific IgG antibodies were detected in 95.8% of the participants. Statistically significant difference was found in the levels of IgG and IgA antibodies both before and after vaccination, p<0.0001. Conclusions: Based on detection of anti-SARS-CoV-2 IgG antibodies, seroprevalence of 32.4% was established in an unvaccinated group of HCWs. Our survey demonstrated that asymptomatic COVID-19 infection may induce weaker humoral immune response, with production of IgA but not of IgG antibodies

Crimean-Congo Hemorrhagic Fever in Bulgaria

We report the epidemiologic characteristics of Crimean-Congo hemorrhagic fever in Bulgaria, as well as the first genetic characterization of the virus strains circulating in the country in 2002 to 2003 that caused disease in humans

Diagnosing Borreliosis

Borrelia species fall into two groups, the Borrelia burgdorferi sensu lato (Bbsl) complex, the cause of Lyme borreliosis (also known as Lyme disease), and the relapsing fever group. Both groups exhibit inter- and intraspecies diversity and thus have variations in both clinical presentation and diagnostic approaches. A further layer of complexity is derived from the fact that ticks may carry multiple infectious agents and are able to transmit them to the host during blood feeding, with potential overlapping clinical manifestations. Besides this, pathogens like Borrelia have developed strategies to evade the host immune system, which allows them to persist within the host, including humans. Diagnostics can be applied at different times during the clinical course and utilize sample types, each with their own advantages and limitations. These differing methods should always be considered in conjunction with potential exposure and compatible clinical features. Throughout this review, we aim to explore different approaches providing the reader with an overview of methods appropriate for various situations. This review will cover human pathogenic members of Bbsl and relapsing fever borreliae, including newly recognized Borrelia miyamotoi spirochetes

Guidelines for the direct detection of Anaplasma spp. in diagnosis and epidemiological studies

The genus Anaplasma (Rickettsiales: Anaplasmataceae) comprises obligate intracellular Gram-negative bacteria that are mainly transmitted by ticks, and currently includes six species: Anaplasma bovis, Anaplasma centrale, Anaplasma marginale, Anaplasma phagocytophilum, Anaplasma platys, and Anaplasma ovis. These have long been known as etiological agents of veterinary diseases that affect domestic and wild animals worldwide. A zoonotic role has been recognized for A. phagocytophilum, but other species can also be pathogenic for humans. Anaplasma infections are usually challenging to diagnose, clinically presenting with nonspecific symptoms that vary greatly depending on the agent involved, the affected host, and other factors such as immune status and coinfections. The substantial economic impact associated with livestock infection and the growing number of human cases along with the risk of transfusion-transmitted infections, determines the need for accurate laboratory tests. Because hosts are usually seronegative in the initial phase of infection and serological cross-reactions with several Anaplasma species are observed after seroconversion, direct tests are the best approach for both case definition and epidemiological studies. Blood samples are routinely used for Anaplasma spp. screening, but in persistently infected animals with intermittent or low-level bacteremia, other tissues might be useful. These guidelines have been developed as a direct outcome of the COST action TD1303 EURNEGVEC (>European Network of Neglected Vectors and Vector-Borne Diseases>). They review the direct laboratory tests (microscopy, nucleic acid-based detection and in vitro isolation) currently used for Anaplasma detection in ticks and vertebrates and their application.This work was done under the frame of COST action TD1303.Peer Reviewe

Biosafety standards for working with Crimean-Congo haemorrhagic fever virus

In countries from which Crimean-Congo haemorrhagic fever (CCHF) is absent, the causative virus CCHF virus (CCHFV) is classified as a hazard group 4 agent and handled in containment level 4. In contrast, most endemic countries out of necessity have had to perform diagnostic tests under biosafety level (BSL) -2 or -3 conditions. In particular, Turkey and several of the Balkan countries have safely processed more than 100000 samples over many years in BSL-2 laboratories. It is therefore advocated that biosafety requirements for CCHF diagnostic procedures should be revised, to allow the required tests to be performed under enhanced BSL-2 conditions with appropriate biosafety laboratory equipment and personal protective equipment used according to standardized protocols in the affected countries. Downgrading of CCHFV research work from Cl-4, BSL-4 to Cl-3, BSL-3 should also be considered.Additional co-authors: Gülay Korukluoglu, Pieter Lyssen, Ali Mirazimi, Johan Neyts, Matthias Niedrig, Aykut Ozkul, Anna Papa, Janusz Paweska, Amadou A Sall, Connie S Schmaljohn, Robert Swanepoel, Yavuz Uyar, Friedemann Weber, Herve Zelle

SARS-COV-2 GENOMIC SURVEILLANCE IN BULGARIA INDICATES DIVERSE DYNAMICS DRIVEN BY MULTIPLE INTRODUCTIONS OF DIFFERENT VIRAL VARIANTS IN 2022

Background. Evolution of the emerging SARS-CoV-2 variants raises concerns about the possibility of accelerated transmission,  disease severity, diagnostic challenges, and reduced vaccine effectiveness in the ever-evolving COVID-19 pandemic worldwide. Objectives for this study were to build a comprehensive national system for monitoring and genomic surveillance of SARS-CoV-2  and to identify the introduced virus variants in the country. Methods. We analyzed SARS-CoV-2 infections in 7948 representative clinical samples collected in medical institutions in different  geographical regions of the country in 2022. Whole-genome next-generation sequencing of SARS-CoV-2 was performed on samples  from randomly selected SARS-CoV-2-positive individuals by using a modified ARTIC v3-tailed amplicon method. A bioinformatic and  phylogenetic analyses of the obtained sequences was carried out. Results. Significant dynamics was observed in the spread of viral variants in 2022, which is characterized by the introduction and  spread of multiple SARS-CoV-2 variants. The phylogenomic analysis identified a high genetic heterogeneiety composed of a total of 152 different viral clades divided into 3 main supergroups: 114 (75.0%) of which were Omicron sub-variants, 35 (23.0%) Delta sub-variants, and 3 (2.0%) recombinant forms. Conclusion. Viral variants and their sub-clades with different potentials to impact disease severity were identified and the  information was immediately published for use by decision-makers and the scientific community. The global pandemic of COVID-19  has shown the importance of molecular biological surveillance, which is an indispensable element of the modern approach in the  fight against infectious diseases