Coxiella burnetii Antibody Prevalence and Risk Factors of Infection in the Human Population of Estonia

Abstract

Q fever is an emerging health problem in both humans and animals. To estimate the prevalence of Coxiella burnetii (C. burnetii) antibodies in the Estonian population, we analyzed plasma samples from 1000 individuals representing the general population and 556 individual serum samples from five population groups potentially at a higher risk (veterinary professionals, dairy cattle, beef cattle, and small ruminant stockbreeders and hunters). Additionally, 118 dairy cow bulk tank milk samples were analyzed to establish the infection status of the dairy cattle herds and the participating dairy cattle keepers. Questionnaires were used to find the potential risk factors of exposure. The effects of different variables were evaluated using binary logistic regression analysis and mixed-effects logistic analysis. The prevalence in veterinary professionals (9.62%; p = 0.003) and dairy cattle farmers (7.73%; p = 0.047) was significantly higher than in the general population (3.9%). Contact with production animals in veterinary practice and being a dairy stockbreeder in C. burnetii positive farms were risk factors for testing C. burnetii seropositive (p = 0.038 and p = 0.019, respectively). Results suggest that C. burnetii is present in Estonia and the increased risk of infection in humans is associated with farm animal contact.Microorganisms 2019, 7, 629 2 of 12 estimates should be compared with caution as different approaches to determine seropositivity for Coxiella burnetii infection have been used in these studies. In most studies, indirect immunofluorescent assay (IFA) [2,3,7,11] or enzyme-linked immunosorbent assay (ELISA) [4,13] has been used, and less frequently the complement fixation test (CFT) [13]. The IFA has been shown to be the most sensitive and specific test for C. burnetii antibody detection, but since IFA testing is more laborious, combining ELISA as a primary screening test and IFA as a confirmatory test has been suggested for large-scale population studies [14].Domestic ruminants are considered one of the main infection sources for humans [13,[15][16][17][18][19][20]. The infection transmits to humans mainly through the inhalation of aerosols containing C. burnetii [13,15,19,21] or via direct contact with infected animals [22,23]. In lactating animals, the bacterium is excreted in the milk [24][25][26], and consuming unpasteurized goat's milk, cow's milk, or raw milk products is a risk factor for acquiring the infection [18,23,27]. Coxiella burnetii produces small spore-like forms [28] that enable the pathogen to survive in the environment for long periods of time [29,30]. Some environmental and meteorological conditions increase the risk of infection, such as higher wind speeds, soil, and landscapes being more sensitive to wind erosion and low rainfall [15,21,31]. A number of animal species, including pets [32][33][34][35], horses [36,37], birds [38], wildlife, and arthropods (mainly ticks) [39][40][41][42], might also play a role in spreading C. burnetii.The main risk factors for human infection are dire...

Pilot Study of Risk Group Human Seroprevalence to Coxiella burnetii (Q Fever) in Latvia

“…The number of control group samples in the study was smaller than the number of risk group samples. Possibly, by increasing the number of control group samples tested, the results would be similar to the study in Estonia where 3.9% seroprevalence was detected among the general adult population, testing 1000 samples from the biobank of the Estonian Genome Centre (Neare et al, 2019).…”

“…However, the seroprevalence in the general population was 3.9% and it did not statistically differ from other risk groups -beef farmers, small ruminant farmers, and hunters. Statistically significant differences were not observed between genders and among various age groups (Neare et al, 2019). The observed seroprevalence in Latvia and Estonia is significantly lower than in other countries.…”

Ticks and Tick-Borne Pathogens Associated with Dromedary Camels (Camelus dromedarius) in Northern Kenya

“…Our results demonstrate that camels and their associated ticks in northern Kenya constitute an important epidemiological reservoir of C. burnetii , which increases human exposure and zoonotic risk of Q fever infection for camel-keeping communities, veterinarians and abattoir workers in the area. Antibodies against C. burnetii have been found in significant numbers of livestock handlers, indicating exposure to the pathogen [ 86 , 87 ]. Given the potential impact of C. burnetii on camel reproduction and the zoonotic risk for public health, further studies are required to better understand the role of camels in the epidemiology of Q fever.…”

Seroepidemiologic evidence of Q fever and associated factors among workers in veterinary service laboratory in South Korea

“…A Japanese study reported diverse seroprevalence for Q fever among the general population and high-risk groups like veterinarians and meat-processing workers (3% in healthy adults vs. 11–22% in high-risk occupations) [ 45 ]. Likewise, another recent study from Estonia [ 46 ] reported significantly higher seroprevalence of C . burnetii antibodies in veterinary professionals (9.62%) and dairy cattle farmers (7.73%) than in the general population (3.9%).…”