Search

The Siberian tick-borne typhus (STT) is the most common tick-borne rickettsiosis (TBR) in Russia, registered in 17 administrative territories of the Southern Siberia and the Far East. The aim of this study was to describe clinical picture, pathological data and results of laboratory diagnostics during fatal mixed infection caused by two Rickettsia species most common in Russia — pathogenic Rickettsia sibirica and poorly examined Candidatus R. tarasevichiae, including identification of its etiological agents. A four-year-old girl in Krasnoyarsk Krai in a hyperendemic focus of the Siberian tick-borne typhus after tick sucking revealed typical TBR symptoms (scab at the site of tick suction, fever, spotted rash, myalgia) and meningeal syndrome, which is not typical for the Siberian tick-borne typhus. The child died on the seventh day of illness. Autopsy data (hepatosplenomegaly; cerebral edema, which was the immediate cause of death) and the results of histological examination (productive vasculitis of the brain, spinal cord and skin, polymorphic cell perivascular infiltrates in the liver and lungs, serous meningitis, myeloid hyperplasia of the spleen and lymph nodes, interstitial lymphoid infiltration in the myocardium) confirmed the clinical diagnosis of tick-borne rickettsiosis. The patient’s blood and brain samples were tested for a wide range of tick-borne pathogens and enteric viruses that cause brain damage using PCR followed by sequencing of the positive samples. The DNA of Rickettsia sibirica and Candidatus Rickettsia tarasevichiae was found in both blood and brain samples. R. sibirica was identified by the nucleotide sequences of gene fragments gltA, ompA and ompB, and Candidatus R. tarasevichiae — by the gltA and ompB genes using nested PCR and sequencing. All amplified fragments were sequenced in both directions; the obtained sequences were deposited in the GenBank database under the inventory numbers MK048467–MK048475. We have not identified other tick-borne pathogens or intestinal viruses in the patient samples able to result in meningeal syndrome. The area where the child was sucked by the tick belongs to the regions with a high incidence of STT. Several species of mites coexist in this area; of these, Haemaphisalis concinna, the carrier of R. sibirica, dominates the populations of Ixodes mites, while Ixodes persulcatus, the main reservoir of Candidatus R. tarasevichiae, is less common. As a result of the conducted studies, for the first time in the Russian Federation, a verified case of a lethal infection associated with two species of Rickettsia — Rickettsia sibirica and Candidatus R. tarasevichiae — was identified and described.

Aim. Estimation of the prevalence of Ixodes tick-borne borreliosis (ITBB) without erythema migrans in the Krasnoyarsk Territory in comparison with the prevalence of ITBB with erythema, that is Lyme disease (LD). Detection of cases of «new» infection caused by Borrelia miyamotoi (ITBB-BM) among patients with suspected tick-borne infection, primarily among patients with ITBB without erythema (ITBB-W/O-E). Materials and methods. We analyzed the database of Rospotrebnadzor containing individualized information about cases of ITBB officially registered in the Krasnoyarsk Territory in 2011 — 2016. Blood samples from 18 patients with suspected of tick-borne infection hospitalized in the Krasnoyarsk Emergency Hospital in 2017 were collected and studied. ITBB-BM was diagnosed if B. miyamotoi DNA was found in patient’s blood and/or the antibodies to specific antigens of B. miyamotoi were detected. Results. With an average annual incidence rate of ITBB of about 10 cases per 100,000 population, the proportion of ITBB-W/O-E among all ITBB in the Krasnoyarsk Territory is about 45%. Epidemiological characteristics of ITBB-W/O-E and LD are similar, but these diseases are very different clinically. All cases of ITBBW/O-E and some cases of tick-borne infections of unknown etiology, subjected to our enhanced laboratory diagnostics, were caused by B. miyamotoi. Conclusion. ITBB-W/O-E is a widespread disease in the Krasnoyarsk Territory, caused mainly by B. miyamotoi. The results of the study significantly expand the known geographic area of the ITBB-BM.