Validation of an indirect immunofluorescence assay (IFA) for the detection of IgG antibodies against Coxiella burnetii in bovine serum

Coxiella burnetii seroprevalence in domestic goat does in the United States: Prevalence, distribution, and associated risk factors

Infection with the bacterium Coxiella burnetii can cause coxiellosis in animals and Q fever in humans. Coxiellosis a consistently underreported infectious disease. The infection can result in reproductive consequences for humans and animals. Ruminants are a reservoir for infection and humans are generally infected via aerosolized secretions, making it a public health concern. Studies of ruminant seroprevalence are generally limited in size and scope. This study determined seroprevalence in a large-scale U.S. population of female goats using serum samples from 7736 does from 24 states. This study identified C. burnetii seroprevalence in the United States domestic goat population. Overall, 14.5 % (SE = 2.3) of does were seropositive and 21.0 % (SE = 2.4) of operations had at least 1 seropositive doe. Further, operation demographics and herd management practices associated with seropositivity were as follows: the suspected or confirmed presence of caprine arthritis encephalitis (CAE), caseous lymphadenitis (CL), Johne's disease, or sore mouth in the herd in the previous 3 years, not cleaning or disinfecting the kidding areas or removing aborting does from other does, allowing visitors to access the kidding areas, and a lower percentage of adult goat inventory that were adult bucks or wethers. Furthermore, goat breed was associated with seropositivity. These data show C. burnetii seroprevalence in the United States and identify operation and animal characteristics and management practices associated with C. burnetii seropositivity. Together, this information can be used to help limit animal transmission, inform public health measures, and help educate and protect individuals working with goats.

Detection of Coxiella antibodies in ruminants using a SucB recombinant antigen

The detection of Coxiella burnetii in ruminants remains challenging despite the use of new technology and the accumulation of novel knowledge. Serology tools, the primary methods of infection surveillance in veterinary medicine, have limitations. We used recombinant antigen production to develop an ELISA based on the SucB protein, one of the major immunodominant antigens described in humans and laboratory animals. We produced the antigen successfully in an Escherichia coli heterologous system, confirmed by sequencing and mass spectrometry, and seen as a band of ~50 kDa in SDS-PAGE and on western blot analysis. We compared the performance of the recombinant ELISA with a commercial ELISA. We observed agreement of 83.5% and a substantial Cohen κ value of 0.67 in our pilot study.

Seroprevalence of Coxiella burnetii antibodies in wild deer populations in eastern Australia

Coxiella burnetii causes significant reproduction losses in livestock and the disease Q fever in humans. Transmission of C. burnetii is facilitated by the stability of the bacterium in the environment and the susceptibility of a variety of host species to infection. Consequently, inter-species transmission occurs frequently through either direct or indirect contact. Wildlife may represent reservoirs of C. burnetii and could therefore be a source of infection for domestic animals. Understanding the prevalence of C. burnetii infections at the wildlife-livestock interface is important for disease control. This study aimed to investigate the extent of C. burnetii exposure in wild deer in eastern Australia. Serum samples were obtained from 413 wild deer from seven regions in four eastern Australian states from 2017 to 2020. Antibodies were detected using a commercial Q fever antibody kit validated for ruminants. Seroprevalence of C. burnetii antibodies in deer was determined and true prevalence estimated, for each region. The overall seroprevalence of C. burnetii antibodies in wild deer was 3.4% (14 seropositive of 413 deer sampled) with true prevalence estimated to be 4.3% (95% credible interval: 0.6%, 10.9%). Seropositive deer were identified only in Queensland (7/108 seropositive) and northern New South Wales (7/120 seropositive). This geospatial distribution is consistent with seropositivity in other animal species and indicative of the level of C. burnetii in the environment. The low seroprevalence suggests that wild deer are unlikely to be a major reservoir species for C. burnetii in eastern Australia but may still be implicated in inter-species transmission cycles.

Screening for Coxiella Burnetii in Dairy Cattle Herds in Poland

Introduction

The intracellular bacterium Coxiella burnetii is the aetiological agent of Q fever, a zoonosis affecting many animal species worldwide. Cattle and small ruminants are considered the major reservoirs of the bacteria and they shed it through multiple routes.

Material and Methods

A total of 2,180 sera samples from 801 cattle herds in all Polish voivodeships were tested by ELISA for the presence of specific antibodies. Milk samples were obtained from seropositive cows in 133 herds as part of a separate study. The milk samples were examined by ELISA and real-time PCR tests.

Results

Seroprevalence at the animal level was 7.06% and true positive seroprevalence was 6.0% (95% confidence interval (CI) 1.1-9.4). Seroprevalence at the herd level was estimated at 11.1% and true positive seroprevalence was 10.5% (95% CI 3.2-15.8). Shedding of the pathogen in milk was detected by real-time PCR in 33 out of 133 tested herds (24.81%, 95% CI 17.74-33.04%) and the presence of C. burnetii antibodies was confirmed in 85 of them (63.9%, 95% CI 55.13-72.05%). The highest level of conformity between ELISA and real-time PCR results was obtained for bulk tank milk samples.

Conclusion

Coxiella burnetii infections are quite common in cattle herds across the country, which emphasises the crucial roles of surveillance and adequate biosecurity measures in the prevention and limitation of Q fever spread in Poland.

First serological evidence of Q fever in large ruminants and its associated risk factors in Punjab, Pakistan

Coxiellosis, also known as Q fever, is a zoonotic disease caused by Coxiella burnetii, a gram-negative bacterium that exerts a significant deleterious impact on the productive and reproductive capabilities of livestock, severely effecting the economics of this sector. In this study, 448 sera samples from cattle (n = 224) and buffalo (n = 224) were collected from 112 farms in Pakistan and examined for antibodies against C. burnetii using an indirect ELISA. Ticks were also collected from these animals. Serological analysis revealed a 23.66% and 27.23% seroprevalence of Q fever in cattle and buffalo, respectively. Odds ratio (OR) analysis of the factors associated with C. burnetii seropositivity was performed, and a multivariable logistic model identified five main variables associated with the seropositivity for coxiellosis. These were: (i) the absence of acaricide use (OR 5.61; 95% CI 2.97-10.94); (ii) the presence of ticks (OR 3.23; 95% CI 1.87-5.69); (iii) the abortion history during the preceding year on the farm (OR 14.96; 95% CI 8.09-29.34); (iv) the presence of sheep and goats (OR 2.47; 95% CI 1.20-5.35); and (v) the absence of a separate parturition area (OR 3.17; 95% CI 1.76-5.86). This study provides new insights into the seroprevalence of Q fever in large ruminants across seven studied districts of Punjab, Pakistan, also providing baseline data to inform improved herd management and on-farm practices for the prevention and control of Q fever in large ruminants in the region. Results of this work suggest that further molecular investigation of coxiellosis is warranted to provide a more thorough evaluation of C. burnetii epidemiology in Pakistan.

Validation of an Indirect Immunofluorescence Assay and Commercial Q Fever Enzyme-Linked Immunosorbent Assay for Use in Macropods

Kangaroos are considered to be an important reservoir of Q fever in Australia, although there is limited knowledge on the true prevalence and distribution of coxiellosis in Australian macropod populations. Serological tests serve as useful surveillance tools, but formal test validation is needed to be able to estimate true seroprevalence rates, and few tests have been validated to screen wildlife species for Q fever. In this study, we modified and optimized a phase-specific indirect immunofluorescence assay (IFA) for the detection of IgG antibodies against Coxiella burnetii in macropod sera. The assay was validated against the commercially available ID Screen Q fever indirect multispecies enzyme-linked immunosorbent assay (ELISA) kit (IDVet, Grabels, France) to estimate the diagnostic sensitivity and specificity of each assay, using Bayesian latent class analysis. A direct comparison of the two tests was performed by testing 303 serum samples from 10 macropod populations from the east coast of Australia and New Zealand. The analysis indicated that the IFA had relatively high diagnostic sensitivity (97.6% [95% credible interval [CrI], 88.0 to 99.9]) and diagnostic specificity (98.5% [95% CrI, 94.4 to 99.9]). In comparison, the ELISA had relatively poor diagnostic sensitivity (42.1% [95% CrI, 33.7 to 50.8]) and similar diagnostic specificity (99.2% [95% CrI, 96.4 to 100]) using the cutoff values recommended by the manufacturer. The estimated true seroprevalence of C. burnetii exposure in the macropod populations included in this study ranged from 0% in New Zealand and Victoria, Australia, up to 94.2% in one population from New South Wales, Australia.

Characterization of recombinant Ybgf protein for the detection of Coxiella antibodies in ruminants

Q fever remains a One Health problem, posing a zoonotic threat and causing significant economic losses to the livestock industry. The advancement of detection tools is critical to the effective control of infection. In humans, laboratory investigations depend largely on the immunofluorescence assay, considered the gold standard. In contrast, serologic tools routinely used for veterinary screening have several gaps, resulting in interpretations that are frequently misleading. We investigated the potential application of recombinant Ybgf antigen (r-Ybgf), a periplasmic protein described as one of the most immunodominant antigens in humans, in an indirect ELISA. Following successful expression in the prokaryotic system and the preliminary evaluation of immunoreactivity in western blot, we used r-Ybgf to develop an in-house ELISA using serum samples from sheep, goats, and cattle, which were tested in parallel with an Idexx ELISA kit. The results obtained with the 2 tests were compared, and r-Ybgf performed favorably, with 81.8% sensitivity and 90.1% specificity and substantial agreement, as revealed by receiver operating characteristic analysis. Moreover, we evaluated the serologic response against phase I (PhI) and phase II (PhII) antigens, and r-Ybgf antigen induced by vaccination, using phase-specific ELISAs. The dynamics of antibody response showed a significant increase in reactivity against PhI and PhII, but not against r-Ybgf, antigens. This property may be very useful given the absence of a protocol for the differentiation of infected from vaccinated animals.

Evaluation of the sensitivity and specificity of three diagnostic tests for Coxiella burnetii infection in cattle and buffaloes in Punjab (India) using Bayesian latent class analysis

Q Fever is a zoonotic disease of significant animal and public health concern, caused by Coxiella burnetii (C. burnetii), an obligate intracellular bacterium. This study was done to evaluate the diagnostic sensitivity (DSe) and diagnostic specificity (DSp) of three diagnostic methods to diagnose C. burnetii infection in cattle and buffaloes in Punjab, India: an indirect ELISA method applied in serum samples and a trans-Polymerase Chain Reaction (trans-PCR) technique applied in milk samples and genital swabs, using a Bayesian latent class analysis. Conditional independence was assumed between the tests, given (i) the different biological principle of ELISA and trans-PCR and (ii) the fact that the trans-PCR was performed on different tissues. The ELISA method in the serum samples showed the highest DSe of 0.97 (95% Probability Intervals (PIs): 0.93; 0.99) compared to the trans-PCR method applied in milk samples 0.76 (0.63; 0.87) and genital swabs 0.73 (0.58; 0.85). The DSps of all tests were high, with trans-PCR in genital swabs recording the highest DSp of 0.99 (0.98; 1), while the DSp of trans-PCR in milk samples and ELISA in serum samples were 0.97 (0.95; 0.99) and 0.95 (0.93; 0.97) respectively. The study results show that none of the applied tests are perfect, therefore, a testing regimen based on the diagnostic characteristic of the tests may be considered for diagnosis of C. burnetii.

The first report of seroprevalence of Q fever in water buffaloes (Bubalus bubalis) in Phatthalung, Thailand

Background and Aim:

Q fever is a worldwide zoonosis caused by the intracellular bacterium, Coxiella burnetii. A few studies focused on the occurrence of Q fever infection in water buffaloes in Thailand have been conducted; however, little is known regarding the seroprevalence of C. burnetii antibodies in buffaloes. In the present study, we describe the prevalence of Q fever infection in water buffaloes (Bubalus bubalis) in Phatthalung, Thailand.

Materials and Methods:

A total of 421 samples (156 blood, 156 sera, and 109 ectoparasites [lice]) were collected from 156 water buffaloes from 29 farms of the Phatthalung Province from January 22, 2021, to March 26, 2021. The blood and ectoparasite samples were screened for C. burnetii DNA using a polymerase chain reaction assay and the sera were tested for C. burnetii antibody using an indirect immunofluorescence assay.

Results:

C. burnetii DNA was not detected in blood or ectoparasites; however, the seroprevalence of individual water buffaloes was 4.49% (95% CI: 2.19-8.99%), whereas that of the herd was 13.79%. There was a significant difference between abortion history and Q fever infection at 29 farms (p=0.005; OR=33.55 [95%CI: 156-722.38]).

Conclusion:

This is the first report describing the low seroprevalence of C. burnetii antibodies in water buffaloes in Phatthalung Province, Thailand. The occurrence of this pathogen in buffaloes with reproductive disorders and people working with buffaloes warrant further investigation. Animal health authorities should inform farmers to effectively prevent and control this zoonosis.

Evaluation using latent class models of the diagnostic performances of three ELISA tests commercialized for the serological diagnosis of Coxiella burnetii infection in domestic ruminants

ELISA methods are the diagnostic tools recommended for the serological diagnosis of Coxiella burnetii infection in ruminants but their respective diagnostic performances are difficult to assess because of the absence of a gold standard. This study focused on three commercial ELISA tests with the following objectives (1) assess their sensitivity and specificity in sheep, goats and cattle, (2) assess the between- and within-herd seroprevalence distribution in these species, accounting for diagnostic errors, and (3) estimate optimal sample sizes considering sensitivity and specificity at herd level. We comparatively tested 1413 cattle, 1474 goat and 1432 sheep serum samples collected in France. We analyzed the cross-classified test results with a hierarchical zero-inflated beta-binomial latent class model considering each herd as a population and conditional dependence as a fixed effect. Potential biases and coverage probabilities of the model were assessed by simulation. Conditional dependence for truly seropositive animals was high in all species for two of the three ELISA methods. Specificity estimates were high, ranging from 94.8% [92.1; 97.8] to 99.2% [98.5; 99.7], whereas sensitivity estimates were generally low, ranging from 39.3 [30.7; 47.0] to 90.5% [83.3; 93.8]. Between- and within-herd seroprevalence estimates varied greatly among geographic areas and herds. Overall, goats showed higher within-herd seroprevalence levels than sheep and cattle. The optimal sample size maximizing both herd sensitivity and herd specificity varied from 3 to at least 20 animals depending on the test and ruminant species. This study provides better interpretation of three widely used commercial ELISA tests and will make it possible to optimize their implementation in future studies. The methodology developed may likewise be applied to other human or animal diseases.

Evaluation of three immunological assays to mitigate the risk of transboundary spread of Coxiella burnetii by alpacas

Coxiella burnetii causes coxiellosis in animals and Q fever in humans, a potentially debilitating zoonotic disease commonly transmitted through domestic ruminants. To prevent transboundary spread of C. burnetii, animals may be tested prior to export. In alpacas, this process is complicated by the lack of scientific evidence for C. burnetii infection in the species, and the unique composition of camelid antibodies, which may cause false-positive results in assays developed for ruminants. We evaluated a complement fixation test (CFT; currently recommended for alpacas in New Zealand), an enzyme-linked immunosorbent assay (ELISA) and an immunofluorescence assay (IFA). Positive analytical control samples were generated through vaccination of alpacas with a human Q fever vaccine, whereas negative analytical control samples were sourced from New Zealand (deemed free of C. burnetii). Immunological assays were conducted on 131 alpaca sera submitted for export testing. Test characteristics (sensitivity, specificity, positive and negative predictive values) for CFT, ELISA and IFA were determined using Bayesian latent class analysis. Due to anticomplementary activity, 37 (28.2%) of the CFT results were inconclusive, making CFT unsuitable for routine use. Of the remaining 94 samples, 10.6%, 0% and 7.4% were positive for C. burnetii antibodies based on CFT, ELISA and IFA, respectively, yielding estimated sensitivities of 58%, 26% and 78%, and estimated specificities of 95%, 98% and 95%, with the estimates for sensitivity being imprecise, as evidenced by wide 95% credible intervals. Positive predictive values were similar across assays, albeit very low at the estimated seroprevalence of 5%. Our results indicate that, of the tests available, IFA appears to be the most appropriate for use in alpacas. Higher sensitivity of antibody detection, use of antigen detection assays and availability of samples from individuals with evidence of infection could provide additional insight into the risk of transboundary spread of C. burnetii by alpacas.

A Freedom of Coxiella burnetii Infection Survey in European Bison (Bison bonasus) in Poland

Simple Summary

Q fever is one of the important diseases transmissible from animals to humans. The source of infection can be numerous species of animals including mammals, birds, reptiles, amphibians as well as ticks. The role of wildlife in its epidemiology is poorly understood. Therefore, we examined 523 sera samples obtained from European bison for the presence of specific antibodies to assess whether infection occurs in this species and whether European bison may be an important source of infection in the natural environment as suggested by historical reports. The antibodies were found only in one free-living bull, while two other samples were doubtful. The results suggest the transmission of infection to the European bison was rather accidental and its role as an important source of infection nowadays is unlikely.

Abstract

Q fever is an important zoonosis caused by the intracellular Gram-negative bacteria Coxiella burnetii. The source of infection are numerous species of mammals, birds, reptiles and amphibians, as well as ticks. The disease is widespread throughout Europe, but the role of wildlife in its epidemiology is poorly understood. The European bison (Bison bonasus) population has been growing European-wide quite dynamically over the last few years. The aim of this study was to determine whether C. burnetii infection occurs in European bison and whether it can be considered an important bacterial reservoir in the natural environment. Five hundred and twenty three samples of European bison sera originating from 14 (out of the 26 existing) Polish populations were examined for the presence of specific antibodies using an ID Screen Q Fever Indirect Multi-species ELISA test. Only one (0.19%) serum sample was positive in ELISA, and two other samples were doubtful. The only seropositive animal found in this study was a free-living bull. It suggests possible transmission from domestic cattle by sharing pastures. The transmission of C. burnetii into the European bison was rather accidental in the country and its role as an important wild reservoir is unlikely. Since no tests are available for wildlife ruminants there is a need for the adaptation of the available tests.

Prevalence and spatial distribution of Coxiella burnetii seropositivity in northern Australian beef cattle adjusted for diagnostic test uncertainty

Q fever is a zoonotic disease caused by infection with Coxiella burnetii transmitted from animals including, but not limited to, cattle, sheep and goats. The infection in cattle is typically sub-clinical with some evidence suggesting associated reproductive loss. There is currently limited data on the true prevalence and distribution of coxiellosis in beef cattle across northern Australia. During this study, 2,012 sera samples from beef cattle managed on commercial farms located in Queensland and the Northern Territory were tested using an indirect immunofluorescent assay (IFA) for serological evidence of IgG antibodies against C. burnetii. Bayesian latent class models were used to estimate the true prevalence, adjusted for diagnostic test sensitivity and specificity and incorporating the hierarchical structure of the cattle within farms and regions. In this study, cattle in the Northern Territory had lower estimated true prevalence than cattle within most regions of Queensland with the exception of south-east Queensland. Results from this study have described the geographic distribution and estimated the true prevalence of antibodies to C. burnetii in a sample of extensively managed beef cattle located across the tropical grazing regions of northern Australia.

Molecular detection of Coxiella burnetii in horse sera in Iran

Coxiella burnetii is a zoonotic bacterium that can infect a wide range of animals including horses. However, its circulation dynamics in and through horses are still unclear. The aim of this study was to evaluate prevalence of C. burnetii and its genomic characteristics in horse sera samples in the North of Iran (Golestan Province). The samples were collected in 2018 and the age, sex, and breed of each animal were recorded. Nested-PCR was used to detect C. burnetii based on the presence of the transposable gene IS1111. The results showed that 7.50 % (P < 0.05; 95 % CI: 0.5 %-0.12 %) of the examined sera samples were positive for C. burnetii. Based on the resuls, prevalence of C. burnetii in the age groupof < Years 1-5 (p-value <0.05, 95 % CI: 1 %-8 %) was less than the age group of >6 years old (p-value <0.05, 95 %, CI: 7 %-19.8 %). In previous studies, it was concluded that the horses' population in Golestan Province should be considered as an important factor in the epidemiology of Q fever and consequently in public health. Further studies should be implemented to evaluate if horses may be relevant indicators of zoonotic risk in urban and suburban endemic areas.

Detection of Coxiella burnetii antibodies in sheep and cattle on a veterinary campus in St. Kitts: Implications for one health in the Caribbean region

Coxiella burnetii is a ubiquitous zoonotic bacterium reported worldwide that causes Q-fever. Infections result in profound economic losses to livestock producers by causing abortions and low birth weights. Current information about the disease in the Caribbean region is scarce. With multiple small islands and territories, it is often considered that the bacterium is absent or circulates at a low prevalence. Our study aimed to determine whether sheep and cattle housed at a veterinary campus in St Kitts had previous exposure to C. burnetii. Blood samples were taken from cattle (n = 63; 72% of the herd) and sheep (n = 133; 71% of the flock). Antibodies to C. burnetii were detected by a commercial indirect enzyme-linked immunosorbent assay (IDvet® ELISA) test. The seroprevalence was estimated at 26.3% (95% CI: 19.1–34.7%) in sheep and 0% (95% CI: 0–5.7%) in cattle. Sheep importation to St. Kitts is very rare, thus, these results suggest that C. burnetii is present on the island. The seronegativity of all the cattle highlights the absence of the bacterium on the veterinary campus. The high seroprevalence in sheep, however, has potentially important implications for animal health and public health as well as for wildlife conservation. Further investigation about animal seroprevalence and human exposure are warranted in St. Kitts and in the Caribbean region.

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Seroprevalence in sheep from a veterinary university was 26.3%

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No cattle from the university were seropositive

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Risk for human and animal health is likely to be important in St. Kitts

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There is a need to investigate the prevalence of Coxiella burnetii in Caribbean region

Evaluation of the Diagnostic Potential of Recombinant Coxiella burnetii Com1 in an ELISA for the Diagnosis of Q Fever in Sheep, Goats and Cattle

Coxiella burnetii is the causative agent of Q fever, a zoonosis infecting domestic ruminants and humans. Currently used routine diagnostic tools offer limited sensitivity and specificity and symptomless infected animals may be missed. Therefore, diagnostic tools of higher sensitivity and specificity must be developed. For this purpose, the C. burnetii outer membrane protein Com1 was cloned and expressed in Escherichia coli. The His-tagged recombinant protein was purified and used in an indirect enzyme-linked immunosorbent assay (ELISA). Assay performance was tested with more than 400 positive and negative sera from sheep, goats and cattle from 36 locations. Calculation of sensitivity and specificity was undertaken using receiver operating characteristic (ROC) curves. The sensitivities and specificities for sheep were 85% and 68% (optical density at 450nm, OD₄₅₀ cut-off value 0.32), for goats 94% and 77% (OD₄₅₀ cut-off value 0.23) and for cattle 71% and 70% (OD₄₅₀ cut-off value 0.18), respectively. These results correspond to excellent, outstanding and acceptable discrimination of positive and negative sera. In summary, recombinant Com1 can provide a basis for more sensitive and specific diagnostic tools in veterinary medicine.