Molecular prevalence of Coxiella burnetii in bulk-tank milk from bovine dairy herds: Systematic review and meta-analysis

Prevalence of Coxiella burnetii in unpasteurized dairy products in west of Iran

Q fever is a zoonotic disease caused by Coxiella burnetii. This study investigated the prevalence of C. burnetii in traditional dairy products, specifically yogurt and cheese, in Lorestan Province. A total of 100 samples of traditional yogurt and unpasteurized cheese were collected from various regions. To analyze the genome of C. burnetii, DNA was purified and molecular detection was performed using nested PCR with primers specific to the IS1111 transposon gene. The results revealed a prevalence of 13.3 % (95 % CI: 6.9 %-24.16 %) in yogurt samples and 12.5 % (95 % CI: 5.46 %-26.11 %) in cheese samples. Additionally, a significant seasonal variation in contamination levels was observed, with a p-value of less than 0.05. However, no significant correlation was found between geographical location and the degree of contamination. These findings suggest that the contamination of dairy products with C. burnetii is likely due to the bacterium's 'spore-like' form and the lack of pasteurization in the traditional production of yogurt and cheese. While the direct risk of transmission via unpasteurized dairy products is considered low, these products should still be monitored in Q fever outbreaks.

Herd-level seroprevalence, molecular prevalence, and trends of Coxiella burnetii (Q fever) in cattle worldwide: A systematic review and meta-analysis

Background and Aim

Cattle are the reservoir host of Coxiella burnetii, a causative agent of Q fever. Pooling herd-level prevalence data from individual studies would help determine the global prevalence of C. burnetii in cattle herds. This study aimed to estimate the global herd-level seroprevalence and molecular prevalence of C. burnetii in cattle, explore sources of heterogeneity, and determine trends and cumulative evidence of the pooled prevalence over time.

Materials and Methods

Relevant studies were retrieved from PubMed, Scopus, and Web of Science and then screened for possible inclusion. A random-effects model was used for all meta-analyses. Subgroup meta-analysis and meta-regression were used to explore some sources of heterogeneity associated with the pooled prevalence and to determine the trends of C. burnetii in cattle herds over the study years (1961-2020). A cumulative meta-analysis was used to determine the cumulative evidence of the pooled prevalence over the publication years.

Results

Of the 1541 citations, 86 studies with 38,057 cattle herds from 42 countries on six continents were included in the meta-analysis. The global herd-level seroprevalence of C. burnetii in cattle was estimated to be 44.4% (95% confidence interval [CI], 37.9%-51.1%), with high heterogeneity among the included studies. The herd-level seroprevalence was significantly higher in dairy than in beef cattle herds (49.0% [95% CI: 41.9%-56.2%] vs. 14.5% [95% CI: 5.8%-32.1%], respectively). The global herd-level molecular prevalence of C. burnetii in cattle was estimated to be 32.3% (95% CI: 25.3%-40.01%), with high heterogeneity among the included studies. Herd-level molecular prevalence was significantly different among continents. The herd-level molecular prevalence ranged from 12.8% (95% CI: 7.1%-21.9%) in Asia to 70.0% (95% CI: 36.3%-90.5%) in North America. Regarding trends, the herd-level seroprevalence of C. burnetii in cattle did not change significantlyover the study years.

Conclusion

The global herd-level seroprevalence and herd-level molecular prevalence of C. burnetii in cattle were high, estimated at 44% and 32%, respectively. The herd-level seroprevalence trend did not significantly change over time. This result indicates that cattle remain a major reservoir host for C. burnetii and pose a potential risk to human health.

Molecular and genotyping techniques in diagnosis of Coxiella burnetii: An overview

Although we live in the genomic era, the accessibility of the complete genome sequence of Coxiella burnetii, the etiological agent of Q fever, has increased knowledge in the field of genomic diversity of this agent However, it is still somewhat of a "question" microorganism. The epidemiology of Q fever is intricate due to its global distribution, repository and vector variety, as well as absence of surveys defining the dynamic interaction among these factors. Moreover, C. burnetii is a microbial agent that can be utilized as a bioterror weapon. Therefore, typing techniques used to recognize the strains can also be used to trace infections back to their source which is of great significance. In this paper, the latest and current typing techniques of C. burnetii spp. are reviewed illustrating their advantages and constraints. Recently developed multi locus VNTR analysis (MLVA) and single-nucleotide polymorphism (SNP) typing methods are promising in improving diagnostic capacity and enhancing the application of genotyping techniques for molecular epidemiologic surveys of the challenging pathogen. However, most of these studies did not differentiate between C. burnetii and Coxiella-like endosymbionts making it difficult to estimate the potential role that ticks play in the epidemiology of Q fever. Therefore, it is necessary to analyze the vector competence of different tick species to transmit C. burnetii. Knowledge of the vector and reservoir competence of ticks is important for taking adequate preventive measures to limit infection risks. The significant prevalence observed for the IS1111 gene underscores its substantial presence, while other genes display comparatively lower prevalence rates. Methodological variations, particularly between commercial and non-commercial kit-based methods, result in different prevalence outcomes. Variations in sample processing procedures also lead to significant differences in prevalence rates between mechanical and non-mechanical techniques.

Molecular prevalence of Coxiella burnetii in cheese samples: Systematic review and meta-analysis

BACKGROUND

Cheese is a popular dairy product consumed worldwide, and it has been implicated as a source of Coxiella burnetii infections.

OBJECTIVES

The present study aimed to describe the molecular prevalence and source analysis of C. burnetii in cheese samples.

METHODS

A systematic literature search was conducted using the Medline/PubMed, Science Direct, Web of Science, Scopus, and Google Scholar databases to identify studies reporting the molecular prevalence of C. burnetii in cheese samples. The pooled prevalence of C. burnetii in cheese samples was estimated using a random-effects model.

RESULTS

A meta-analysis was conducted using the mean and standard deviation values obtained from 13 original studies. The overall molecular prevalence of C. burnetii in cheese was estimated to be 25.2% (95% confidence interval [CI]: 13.1%-39.7%). The I2 value of 96.3% (CI95% 94.9-97.3) suggested high heterogeneity, with a τ2 of 0.642 (CI95% -0.141 to 0.881), and an χ2 statistic of 323.77 (p < 0.0001).

CONCLUSIONS

In conclusion, our meta-analysis provides a thorough assessment of the molecular prevalence and source analysis of C. burnetii in cheese samples.

Molecular and serological prevalence of Coxiella burnetii in bovine dairy herds in southern Chile: A PCR and ELISA-based assessment of bulk tank milk samples

Coxiella burnetii (C. burnetii) is a highly resilient zoonotic bacterium responsible for Q fever, a disease which occurs worldwide, with the exception of New Zealand. However, in Chile, the prevalence and impact of C. burnetii in cattle herds remain poorly understood due to limited research. This study aimed to assess the presence of C. burnetii in dairy cattle herds in southern Chile, using two diagnostic methods on bulk tank milk samples. The results of the study revealed a high prevalence of C. burnetii infection in the analyzed herds. Of the 271 milk tank samples tested, 76% (208/271, CI: 71.1-81.5) tested positive using ELISA, while 73% (200/271, CI: 68.0-78.8) tested positive using qPCR. These findings indicate a significant presence of C. burnetii in the cattle herds studied. Despite the high prevalence observed, no new Q fever outbreaks have been reported in the study area. This discrepancy highlights the need for further research to better understand the transmission dynamics, environmental factors, and livestock management practices associated with C. burnetii infection. These studies will contribute to the development of effective prevention and control strategies and promote public health regarding Q fever.

Distribution and Prevalence of Coxiella burnetii in Animals, Humans, and Ticks in Nigeria: A Systematic Review

'Query' (Q) fever is a neglected but emerging or re-emerging zoonotic disease caused by the bacterium Coxiella (C.) burnetii. Several host species are considered or speculated to be the primary reservoir hosts for human infection. In the past, several research groups in Nigeria have evaluated the prevalence of C. burnetii in various vertebrate and invertebrate hosts. Currently, there is a paucity of knowledge regarding the epidemiology of the pathogen in Nigeria with limited or no attention to control and prevention programs. Therefore, this review was undertaken to comprehend the current situation of C. burnetii infection in human, domestic and peri-domestic animals, and some tick species in Nigeria since 1960 with the aim to help identify future research priorities for the country. A comprehensive literature search was performed using the PRISMA guidelines on five scientific databases including Google Scholar, PubMed, AJOL, Science Direct, and Scopus for articles published from Nigeria dealing with the screening of blood, milk, or tick DNA for evidence of C. burnetii using any standard diagnostic approach. Of the 33 published articles subjected to full-text evaluation, more than 48% of the articles met the inclusion criteria and were thus included in this review. We observed different ranges of prevalence for C. burnetii antibodies from four vertebrate hosts including cattle (2.5-23.5%), sheep (3.8-12.0%), goats (3.1-10.9%), and humans (12.0-61.3%). Additionally, the use of molecular diagnostics revealed that the DNA of C. burnetii has been amplified in eight tick species including Hyalomma (Hy) dromedarii, Hy. truncatum, Hy. impeltatum, Hy. rufipes, Hy. impressum, Amblyomma (Am.) variegatum, Rhipicephalus (Rh.) evertsi evertsi, and Rh. annulatus. Two rodent's species (Rattus rattus and Rattus norvegicus) in Nigeria were documented to show evidence of the bacterium with the detection of the DNA of C. burnetii in these two mammals. In conclusion, this review has provided more insight on the prevalence of C. burnetii and its associated host/vector in Nigeria. Domestic animals, peri-domestic animals, and ticks species harbor C. burnetii and could be a source of human infections. Due to the paucity of studies from southern Nigeria, we recommend that research groups with interest on vector-borne diseases need to consider more epidemiological studies in the future on C. burnetii prevalence in diverse hosts to help unravel their distribution and vector potentials in Nigeria as a whole.

Detection of Coxiella burnetii and characterisation by multiple-locus variable-number tandem repeat analysis in bovine bulk tank milk samples

Coxiella burnetii is the aetiological agent of Q fever, which is highly prevalent in Turkiye, but information on the genetic profiles of the bacterium is limited. This study aimed to investigate the presence of C. burnetii in bovine bulk tank milk (BTM) samples by polymerase chain reaction (PCR) and to investigate the genotypes by means of multiple-locus variable-number tandem repeat analysis (MLVA). A total of 25 markets that sold raw cow's milk were analysed by conventional PCR analysis. An MLVA analysis was performed at six loci, namely MS23, MS24, MS27, MS28, MS33, and MS34, to determine the genotypic variations of C. burnetii found in the positive DNA samples. The DNA of C. burnetii was detected in 16% of the BTM samples. The C. burnetii strains identified in the bovine milk samples collected in this study were found to belong to the same genotypic group as those detected in the bovine milk samples gathered in Greece. As a result, both the presence and genotyping studies of C. burnetii on the BTM samples in Turkiye will contribute to the determination of the geographical distribution of the agent.

Endemicity of Coxiella burnetii infection among people and their livestock in pastoral communities in northern Kenya

Background

Coxiella burnetti can be transmitted to humans primarily through inhaling contaminated droplets released from infected animals or consumption of contaminated dairy products. Despite its zoonotic nature and the close association pastoralist communities have with their livestock, studies reporting simultaneous assessment of C. burnetti exposure and risk-factors among people and their livestock are scarce.

Objective

This study therefore estimated the seroprevalence of Q-fever and associated risk factors of exposure in people and their livestock.

Materials and methods

We conducted a cross-sectional study in pastoralist communities in Marsabit County in northern Kenya. A total of 1,074 women and 225 children were enrolled and provided blood samples for Q-fever testing. Additionally, 1,876 goats, 322 sheep and 189 camels from the same households were sampled. A structured questionnaire was administered to collect individual- and household/herd-level data. Indirect IgG ELISA kits were used to test the samples.

Results

Household-level seropositivity was 13.2% [95% CI: 11.2–15.3]; differences in seropositivity levels among women and children were statistically insignificant (p = 0.8531). Lactating women had higher odds of exposure, odds ratio (OR) = 2.4 [1.3–5.3], while the odds of exposure among children increased with age OR = 1.1 [1.0–1.1]. Herd-level seroprevalence was 83.7% [81.7–85.6]. Seropositivity among goats was 74.7% [72.7–76.7], while that among sheep and camels was 56.8% [51.2–62.3] and 38.6% [31.6–45.9], respectively. Goats and sheep had a higher risk of exposure OR = 5.4 [3.7–7.3] and 2.6 [1.8–3.4], respectively relative to camels. There was no statistically significant association between Q-fever seropositivity and nutrition status in women, p = 0.900 and children, p = 1.000. We found no significant association between exposure in people and their livestock at household level (p = 0.724) despite high animal exposure levels, suggesting that Q-fever exposure in humans may be occurring at a scale larger than households.

Conclusion

The one health approach used in this study revealed that Q-fever is endemic in this setting. Longitudinal studies of Q-fever burden and risk factors simultaneously assessed in human and animal populations as well as the socioeconomic impacts of the disease and further explore the role of environmental factors in Q-fever epidemiology are required. Such evidence may form the basis for designing Q-fever prevention and control strategies.

Serological, Molecular Prevalence and Genotyping of Coxiella burnetii in Dairy Cattle Herds in Northeastern Algeria

In Algeria, data on the epidemiology of coxiellosis in cattle are still lacking. In this study, bulk tank milk (BTM) samples from 200 randomly selected dairy cattle herds from Setif province of Algeria were analyzed by an indirect enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Results highlighted that 37% (95% CI: 30.31–43.69%) and 9% (95% CI: 5.03–12.96%) of BTM samples contained Coxiella burnetii antibodies and DNA, respectively. Based on Cohen’s kappa coefficient, a very low agreement between the ELISA and PCR results was found (k = 0.0849) (95% CI: 0.00–0.189). For a second experiment, 186 whole blood samples of cows from farms with reproduction disorders were analyzed by molecular tools to detect C. burnetii. This study revealed an overall prevalence of 6.98% (95% CI: 3.32–10.65%). All positive samples determined by conventional PCR were analyzed by real-time quantitative PCR (qPCR). Eleven samples with cycle threshold (Ct) values lower than 35 were selected for genotyping by the multispacer sequence typing (MST) method. The MST12 genotype in BTM samples, the MST32 genotype and a new MST genotype (partial profile) in whole blood samples were identified. Obtained results have allowed us to better understand the epidemiology of bovine coxiellosis in the region of Setif.

Coxiella burnetii abortion in a dairy farm selling artisanal cheese directly to consumers and review of Q fever as a bovine abortifacient in South America and a human milk-borne disease

Coxiella burnetii is a highly transmissible intracellular bacterium with a low infective dose that causes Q fever (coxiellosis), a notifiable zoonotic disease distributed worldwide. Livestock are the main source of C. burnetii transmission to humans, which occurs mostly through the aerogenous route. Although C. burnetii is a major abortifacient in small ruminants, it is less frequently diagnosed in aborting cattle. We report a case of C. burnetii abortion in a lactating Holstein cow from a dairy farm producing and selling artisanal cheese directly to consumers in Uruguay, and review the literature on coxiellosis as a bovine abortifacient in South America and as a milk-borne disease. The aborted cow had severe necrotizing placentitis with abundant intratrophoblastic and intralesional C. burnetii confirmed by immunohistochemistry and PCR. After primo-infection in cattle, C. burnetii remains latent in the lymph nodes and mammary glands, with milk being a significant and persistent excretion route. Viable C. burnetii has been found in unpasteurized milk and cheeses after several months of maturing. The risk of coxiellosis after the consumption of unpasteurized dairy products, including cheese, is not negligible. This report raises awareness on bovine coxiellosis as a potential food safety problem in on-farm raw cheese manufacturing and sales. The scant publications on abortive coxiellosis in cattle in South America suggest that the condition has probably gone underreported in all countries of this subcontinent except for Uruguay. Therefore, we also discuss the diagnostic criteria for laboratory-based confirmation of C. burnetii abortion in ruminants as a guideline for veterinary diagnosticians.

Serological Evidence of Human Infection with Coxiella burnetii after Occupational Exposure to Aborting Cattle

Cattle are broadly deemed a source of Coxiella burnetii; however, evidence reinforcing their role in human infection is scarce. Most published human Q fever outbreaks relate to exposure to small ruminants, notably goats. Anti-phase II C. burnetii IgG and IgM were measured by indirect fluorescent antibody tests in 27 farm and veterinary diagnostic laboratory workers to ascertain whether occupational exposure to cattle aborting due to C. burnetii was the probable source of exposure. Four serological profiles were identified on the basis of anti-phase II IgG and IgM titres. Profile 1, characterised by high IgM levels and concurrent, lower IgG titres (3/27; 11.1%); Profile 2, with both isotypes with IgG titres higher than IgM (2/27; 7.4%); Profile 3 with only IgG phase II (5/27; 18.5%); and Profile 4, in which neither IgM nor IgG were detected (17/27; 63.0%). Profiles 1 and 2 are suggestive of recent C. burnetii exposure, most likely 2.5-4.5 months before testing and, hence, during the window of exposure to the bovine abortions. Profile 3 suggested C. burnetii exposure that most likely predated the window of exposure to aborting cattle, while Profile 4 represented seronegative individuals and, hence, likely uninfected. This study formally linked human Q fever to exposure to C. burnetii infected cattle as a specific occupational hazard for farm and laboratory workers handling bovine aborted material.

Q Fever: A troubling disease and a challenging diagnosis

Q fever is a disease caused by the bacterial pathogen Coxiella burnetii. This hardy organism can easily spread long distances in the wind, and only a few infectious aerosolized particles are necessary to cause serious illness. Presentations of Q fever disease can be wide-ranging, allowing it to masquerade as other illnesses and highlight the importance of laboratory testing for diagnosis and treatment. This review summarizes Q fever's epidemiology and clinical presentations and presents classical laboratory diagnostic assays and novel approaches to detecting this troubling disease.