Molecular and seroepidemiological investigation of Сoxiella burnetii and spotted fever group rickettsiae in the southern region of Kazakhstan

Abstract

Ticks are involved in the circulation of a number of human pathogens, including spotted fever group (SFG) Rickettsia spp. and Coxiella burnetii. Little is known about the occurrence of these microorganisms in the southern region of Kazakhstan. In 2018-2022, a total of 726 ticks were collected from bitten humans, livestock, and vegetation in four oblasts of the southern region of Kazakhstan and subjected to DNA extraction. The overall infection rate of Coxiella spp. and Rickettsia spp. in the ticks was 3.3% (24/726) and 69.9% (300/429), respectively. Phylogenetic analysis of ompA and gltA genes revealed the presence of three pathogenic SFG rickettsiae: Candidatus R. tarasevichiae, R. aeschlimannii and R. raoultii in ticks collected from bitten humans. In addition, Candidatus R. barbariae was detected in six Rhipicephalus turanicus ticks for the first time in Kazakhstan. To determine the seroprevalence of C. burnetii infection, we performed a serological analysis of samples collected from 656 domestic ruminants (cattle, sheep, and goats) in the region. Overall, 23.5% (154/656) of the animals tested were positive for IgG against C. burnetii. Seroprevalence at the herd level was 54% (28/52). Goats (43%; 12/28; odds ratio (OD) = 28.9, p < 0.05) and sheep (31.9%; 137/430; OD = 18.1, p < 0.05) had higher seroprevalence than cattle (2.5%; 5/198). Among the risk factors considered in this study, age (p = 0.003) and the oblast in which the animals were sampled (p = 0.049) were statistically associated with seropostivity for Q fever in sheep, according to the results of multivariate logistic regression analysis. Seroprevalence ranged from 0% to 55.5% in animals in different districts of the southern region of Kazakhstan. Active C. burnetii bacteremia was detected in four of 154 (2.6%) seropositive animals. The data obtained provide strong evidence of the presence of pathogenic rickettsiae and C. burnetii in the southern region of Kazakhstan and emphasize the need to improve epidemiological surveillance in the region.

Keywords: Coxiella burnetii; Q fever; Rickettsia; Southern Kazakhstan; Tick.