Activity of Natural Tularemia Foci in West Ukraine

Oksana Velychko, Liliia Vasiunets, Oksana Semenyshyn, Lesya Hasiy

Abstract


ObjectiveStady the activity of natural foci of tularemia and identify the maintypes of reservoirs and vectors ofFrancisella tularensis.IntroductionAnnually sporadic cases of tularemia in humans are registered inUkraine and new enzootic areas are found. Monitoring of tularemianatural foci is important given the potential significant financiallosses in case of tularemia outbreaks and taken into account that thispathogen can be used as a bioterrorist agent.Methods1. Light microscopy of smears of organs and tissues of animals,bacterial suspension (Gram staining) - the study of morphological andtinctorial properties of the pathogen.2. Immunofluorescence method for detection of antibody (IFA)- detection of tularemia bacterial cells using specific fluorescentimmunoglobulin.3. Biological method - subcutaneous infection of laboratoryanimals (white mice) with material from environmental samples andbacterial suspension (for accumulation of tularemia agent in organsand tissues of laboratory animals).4. Bacteriological method - inoculation of samples of wildand laboratory animals in differential diagnostic nutrient media(for isolation of a pure culture of tularemia agent).5. Serological method:- Indirect reaction of agglutination - detection of antibodies totularemia agent in blood of humans, wild rodents (liquid tularemiaantigen erythrocyte diagnostic agent).- Indirect reaction of agglutination - detection of tularemia agentand its antigen in suspensions of organs, swabs of substrate fromnests of rodents, pellets of birds (liquid tularemia immunoglobulinerythrocyte diagnostic agent).- Reaction of agglutination - detection of tularemia agent and itsantigen (dry tularemia diagnostic serum).ResultsTularemia in Lviv oblast has been studied for more than40 years, 69 enzootic localities in 14 administrative districts have beenregistered. More than 200 cultures ofFrancisella tularensishave beenisolated, mostly from ticks (58.3%) and Myomorphic rodents (24.5%),the rest from water, straw, other rodents, and patients. In 2012-2015,210 suspected patients were studied for tularemia, negative resultswere obtained. 22,320 ticks, 1,810 Myomorphic rodents, 282 watersamples, 15 straw samples, and 3 bird nests were tested for tularemia.Tularemia cultures have not been isolated bacteriologically over thelast few years. Pathogen circulation in natural foci was confirmedby immuno-serological studies of field material. Antibodies to thepathogen were detected in 6.5% out of 630 samples from Myomorphicrodents of seven species studied by Indirect Hemagglutination test.Most of the positive results were obtained from the samples of stripedfield mouse (46.3%), red-backed vole (17.0%), and common vole(14.6%).Francisella tularensisantigen was detected in 32 samplesout of 14,600 ticksD. reticulatuscollected in natural biotopes and in8.9% out of 289 samples of pellet.ConclusionsNo incidence registered in Lviv oblast and difficulty of isolationof Francisella tularensis cultures over the last years in other oblasts(the last one happened in 2006) may indicate the decrease of fociactivity under the influence of anthropogenic and environmentalfactors or changes in parasitic systems. But there are some evidenceof agent circulation in the oblast, so some precautions should betaken, especially considering the fact that there have been no specificpreventive measures taken over the last years.

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DOI: https://doi.org/10.5210/ojphi.v9i1.7673



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