Q fever--a review and issues for the next century

Risk factors associated with Coxiella burnetii in wild boars: A study in South Korea

Coxiella burnetii is a Gram-negative bacterium that causes the zoonotic disease Q fever. Wild boars serve as reservoirs for C. burnetii. This study aimed to identify the risk factors associated with C. burnetii infection in wild boars. We analyzed the data from 975 wild boar samples collected from June to November 2021 in South Korea. We utilized the indirect ELISA to detect antibodies against C. burnetii. A sample optical density to positive-control optical density value exceeding 50% was classified as positive. We gathered data on the forestation, terrain, weather, agriculture, and animal density of the region where the samples were collected. Continuous variables were categorized into tertiles. We performed a univariate logistic regression analysis and included variables with a p-value < 0.2 in the final multivariable logistic regression model. In our multivariable logistic regression analysis to identify risk factors for C. burnetii infection in wild boars, we used a forward selection method to enter variables based on the order of their significance. We performed the final multivariable logistic regression analyses using either continuous variables or variables categorized into tertiles. The prevalence of C. burnetii was 14.6% (n=142). Locations with the highest maximum wind speeds (3.92-8.24 m/s) showed a 59% increase in infection odds compared to locations with the lowest speeds (1.45-3.25 m/s)(p=0.044). For each 1 m/s increase in maximum wind speed, infection odds increased by 24.1% (p=0.037). Regions with the highest percentage of paddy fields per area (8.3-45%) showed a 76% increase in infection odds compared to regions with the lowest percentage (0-1.5%)(p=0.011). For each 1% increase in the proportion of paddy fields per area, infection odds increased by 3.3% (p=0.003). High maximum wind speed and a high percentage of paddy field were identified as significant risk factors for C. burnetii infection in wild boars.

Susceptibility, Immunity, and Persistent Infection Drive Endemic Cycles of Coxiellosis on Dairy Farms

Coxiella (C.) burnetii, a zoonotic bacterium, is prevalent in dairy farms. Some cows develop a persistent infection and shed C. burnetii into milk and occasionally by amniotic fluid at calving. Serological diagnosis of Q fever in humans is performed by phase (Ph)-specific antibody tests; PhII antibodies usually indicate an acute infection, while the development of a chronic infection is characterised by elevated PhI antibody titres. Phase-specific tests have now been established for diagnosis of coxiellosis in cattle. Additionally, an interferon-γ (IFN-γ) recall assay has been implemented to assess cellular immunity to C. burnetii in cattle. Milk samples from all lactating cows (n = 2718) of 49 Bavarian dairy farms were collected through a convenience sample and analysed for phase-specific antibodies. Antibody profiles were evaluated by age. Based on the seropositivity of first-lactation cows, three distinct herd profiles were observed: an 'acute' state of herd infection was characterised by a PhI-/PhII+ pattern. The detection of PhI antibodies (PhI+/PhII+) characterised the 'chronic' state, and seronegative results defined the 'silent' state of herd infection. If antibodies had not been detected in multiparous cows, the herd was considered as probably free of coxiellosis. The analysed cattle herds were noted to have an 'acute' (n = 12, 24.5%), 'chronic' (n = 18, 36.8%), or 'silent' state of herd infection (n = 16, 32.6%). Only three farms (6.1%) were classified as 'free' of C. burnetii. The detection of these herd states over a time period of 4 years in one farm indicated that the described states occur in a cyclical manner. Frequently, a wave-like profile was seen, i.e., a circumscribed seronegative age group was flanked by seropositive age groups. In seronegative animals, IFN-γ reactivity was demonstrated. Seroconversion after vaccination was observed by day 7 post-vaccination in chronically infected herds, whereas in the case of silent infection, it started by day 14. These data indicated a pre-existing immunity in seronegative animals in chronically infected herds. Additionally, IFN-γ reactivity was detected in seronegative calves (>3 months) and heifers from chronically infected farms compared to a negative farm. An infection prior to 3 months of age resulted in cellular immunity in the absence of detectable antibodies. An infection around calving would explain this. The aforementioned circumscribed seronegative age groups are, therefore, explained by an infection early in life during active shedding at calving. Based on these results, an endemic cycle of coxiellosis is proposed: Susceptible young heifers get infected by persistently infected cows. Subsequently, shedding of C. burnetii at calving results in infection and then in cellular immunity in offspring. When these calves enter the cow herd two years later, a maximum of herd immunity is achieved, shedding ceases, and new susceptible animals are raised. In an acutely infected dairy farm, the PhI+/PhII+ serological pattern prevailed in second-lactation cows. In this study, stored sera collected since birth were analysed retrospectively. From the earliest seroconversion, the peak of seroconversion took about 33 months. These data suggested a slow spread of infection within herds. The classification of dairy cow herds is a promising basis for further analysis of the clinical impact of coxiellosis.

Acute Q fever in an Omani presenting with a febrile movement disorder - A Case Report

Q fever is a zoonotic infection caused by the organism Coxiella burnetii. It is transmitted by contracting the organism from it is most known reservoirs which include cattle, sheep, and goats. It is an endemic disease with very few cases reported in the Arabian Peninsula. It can present with a wide range of clinical presentations; however, the neurological manifestation of Q fever is rare and overlooked hence we present a case report of a 38-year-old man who presented with fever, headache, and jerky movements. He had a significant exposure to livestock animals mainly goats and sheep. The work up was negative apart from positive Coxiella burnetii serology and serum PCR suggestive of acute Q fever. He had shown remarkable improvement after a course of antimicrobial therapy with complete resolution of fever and neurological symptoms. Our case report highlights the importance considering Q fever as a cause of unusual neurological symptoms in Q fever endemic areas and patients with a significant zoonotic exposure.

Genetic diversity of wild rodents and detection of Coxiella burnetii, the causative agent of Q fever, in Saudi Arabia

Throughout history, wildlife has been regarded as a major source of infectious diseases. Rodentia, the most speciose order of mammals, whose members are recognised hosts of more than 60 zoonotic diseases, represent a potential threat to human health. Recently, epidemiological data from Saudi Arabia indicated an actual growth in the number of emerging and/or re-emerging cases of several zoonoses. However, there is a lack of studies focusing on the molecular taxonomy of rodents and the pathogens they may harbour in this region. In this study, the first molecular characterisation of six rodent taxa in this region is provided, based on partial Cyt B and 16S genes. The data confirm the spread of rodent-associated C. burnetii strains in Jazan, southwestern Saudi Arabia. The PCR targeting IS111, the multi-copy transposase gene, revealed 17.5% (36/205) positive samples, whereas the second nested PCR, targeting the single-copy Com1 gene, revealed 16.6% (34/205) positive samples. Phylogenetic and network analyses indicated the presence of four haplotypes of C. burnetii within the studied localities. One major haplotype (H-2) was observed in all rodent species and from 18 localities. The infection rates of C. burnetii among studied species, localities and habitats were not significantly different (>0.05). Our results facilitate the assessment of the health risk associated with rodents and the development of strategies to control the increasing impacts of Q fever.

Inactivation Kinetics of Coxiella burnetii During High-Temperature Short-Time Pasteurization of Milk

The Gram-negative, obligate intracellular bacterium Coxiella burnetii is the causative organism of the zoonosis Q fever and is known for its resistance toward various intra- and extracellular stressors. Infected ruminants such as cattle, sheep, and goats can shed the pathogen in their milk. Pasteurization of raw milk was introduced for the inactivation of C. burnetii and other milk-borne pathogens. Legal regulations for the pasteurization of milk are mostly based on recommendations of the Codex Alimentarius. As described there, C. burnetii is considered as the most heat-resistant non-spore-forming bacterial pathogen in milk and has to be reduced by at least 5 log10-steps during the pasteurization process. However, the corresponding inactivation data for C. burnetii originate from experiments performed more than 60 years ago. Recent scientific findings and the technological progress of modern pasteurization equipment indicate that C. burnetii is potentially more effectively inactivated during pasteurization than demanded in the Codex Alimentarius. In the present study, ultra-high heat-treated milk was inoculated with different C. burnetii field isolates and subsequently heat-treated in a pilot-plant pasteurizer. Kinetic inactivation data in terms of D- and z-values were determined and used for the calculation of heat-dependent log reduction. With regard to the mandatory 5 log10-step reduction of the pathogen, the efficacy of the established heat treatment regime was confirmed, and, in addition, a reduction of the pasteurization temperature seems feasible.

Rickettsia burneti and Brucella melitensis co-infection: a case report and literature review

Rickettsia is the pathogen of Q fever, Brucella ovis is the pathogen of brucellosis, and both of them are Gram-negative bacteria which are parasitic in cells. The mixed infection of rickettsia and Brucella ovis is rarely reported in clinic. Early diagnosis and treatment are of great significance to the treatment and prognosis of brucellosis and Q fever. Here, we report a case of co-infection Rickettsia burneti and Brucella melitensis. The patient is a 49-year-old sheepherder, who was hospitalized with left forearm trauma. Three days after admission, the patient developed fever of 39.0°C, accompanied by sweating, fatigue, poor appetite and headache. Indirect immunofluorescence (IFA) was used to detect Rickettsia burneti IgM. After 72 hours of blood culture incubation, bacterial growth was detected in aerobic bottles, Gram-negative bacilli were found in culture medium smear, the colony was identified as Brucella melitensis by mass spectrometry. Patients were treated with doxycycline (100 mg bid, po) and rifampicin (600 mg qd, po) for 4 weeks. After treatment, the symptoms disappeared quickly, and there was no sign of recurrence or chronic infection. Q fever and Brucella may exist in high-risk practitioners, so we should routinely detect these two pathogens to prevent missed diagnosis.

Identification of Immunogenic Linear B-Cell Epitopes in C. burnetii Outer Membrane Proteins Using Immunoinformatics Approaches Reveals Potential Targets of Persistent Infections

Coxiella burnetii is a global, highly infectious intracellular bacterium, able to infect a wide range of hosts and to persist for months in the environment. It is the etiological agent of Q fever—a zoonosis of global priority. Currently, there are no national surveillance data on C. burnetii’s seroprevalence for any South American country, reinforcing the necessity of developing novel and inexpensive serological tools to monitor the prevalence of infections among humans and animals—especially cattle, goats, and sheep. In this study, we used immunoinformatics and computational biology tools to predict specific linear B-cell epitopes in three C. burnetii outer membrane proteins: OMP-H (CBU_0612), Com-1 (CBU_1910), and OMP-P1 (CBU_0311). Furthermore, predicted epitopes were tested by ELISA, as synthetic peptides, against samples of patients reactive to C. burnetii in indirect immunofluorescence assay, in order to evaluate their natural immunogenicity. In this way, two linear B-cell epitopes were identified in each studied protein (OMP-H_(51–59), OMP-H_(91–106), Com-1_(57–76), Com-1_(191–206), OMP-P1_(197–209), and OMP-P1_(215–227)); all of them were confirmed as naturally immunogenic by the presence of specific antibodies in 77% of studied patients against at least one of the identified epitopes. Remarkably, a higher frequency of endocarditis cases was observed among patients who presented an intense humoral response to OMP-H and Com-1 epitopes. These data confirm that immunoinformatics applied to the identification of specific B-cell epitopes can be an effective strategy to improve and accelerate the development of surveillance tools against neglected diseases.

Prevalence of Coxiella burnetii seropositivity and shedding in farm, pet and feral cats and associated risk factors in farm cats in Quebec, Canada

Cats represent a potential source of Coxiella burnetii, the aetiological agent of Q fever in humans. The prevalence and risk factors of C. burnetii infection in farm, pet and feral cats were studied in Quebec, Canada, using a cross-sectional study. Serum samples were tested using a specific enzyme-linked immunosorbent assay (ELISA) for the presence of antibodies against C. burnetii, whereas rectal swabs were assayed using real-time quantitative polymerase chain reaction (qPCR) for the molecular detection of the bacteria. Potential risk factors for farm cats were investigated using clinical examinations, questionnaires and results from a concurrent study on C. burnetii farm status. A total of 184 cats were tested: 59 from ruminant farms, 73 pets and 52 feral cats. Among farm cats, 2/59 (3.4%) were ELISA-positive, 3/59 (5.1%) were ELISA-doubtful and 1/59 (1.7%) was qPCR-positive. All pets and feral cats were negative to C. burnetii ELISA and qPCR. Farm cat positivity was associated with a positive C. burnetii status on the ruminant farm (prevalence ratio = 7.6, P = 0.03). Our results suggest that although pet and feral cats do not seem to pose a great C. burnetii risk to public health, more active care should be taken when in contact with cats from ruminant farms.

Selected Endemic Zoonoses in Pigs Presenting for Slaughter in Kampala, Uganda

Leptospirosis, brucellosis, and Q fever (coxiellosis) are bacterial zoonoses that cause acute febrile illness in people as well as reproductive losses in pigs. Pig keeping is an increasingly important livelihood to millions of smallholder farmers in Uganda because of exponential increases in demand for pork. The prevalence of leptospirosis and Q fever in pigs is unknown, and the few studies of porcine brucellosis have estimated a range of seroprevalence. Therefore, we undertook a prevalence survey of leptospirosis, brucellosis, and Q fever in pigs using quantitative real-time PCR to determine the potential importance of these zoonoses to the growing pig sector in Uganda. Six hundred forty-nine pigs were sampled in 2015–2016 at an urban pork slaughterhouse. Ten percent of pigs (n = 68) had leptospiral DNA in either their kidney or reproductive tissue. In adjusted analyses, variables predictive of leptospiral status included female sex (odds ratio [OR]: 2.37, P < 0.01) and pigs sampled in March 2016 (OR: 2.23, P = 0.02) and October 2016 (OR: 0.30, P = 0.04). DNA fingerprinting revealed circulation of at least four distinct serovars in these pigs. Brucella spp. and Coxiella burnetii DNA were not detected in any sampled pig. This is the first report of widespread circulation of pathogenic Leptospira spp. in pigs in Uganda, suggesting that leptospirosis likely has a greater impact on the health of pigs than was previously recognized. Pig farmers, pig traders, and slaughterhouse workers may be at greatest occupational risk because of their direct contact with infective leptospires in aborted fetuses, bodily fluids, and other tissues.

First molecular detection of Coxiella burnetii in Brazilian artisanal cheese: a neglected food safety hazard in ready-to-eat raw-milk product

Background

Global publications on Q fever have increased after the 2007 epidemic in the Netherlands. However, the epidemiology of Q fever/coxiellosis in Brazil is still poorly understood. Accordingly, there have been few studies investigating the presence of Coxiella burnetii in dairy products around the world, especially in Brazil, where consumption of fresh cheese made from raw-milk is very high.

Objective

This study was a random survey to assess the prevalence of C. burnetii by PCR in traditional Minas artisanal cheese from the Serro microregion, Brazil, which is manufactured from bovine raw-milk.

Methods

DNA extracted from 53 cheese samples were analyzed by nested PCR with C. burnetii-specific primers and the products confirmed by DNA sequencing.

Results

Out of the 53 cheese samples five (9.43%) were C. burnetii DNA-positive, each coming from one of the respective randomly selected manufacturing agroindustries.

Based on our results, it is estimated that 1.62 tons/day of ready-to-eat cheese made from raw-milk from a total of 16.2 tons produced daily in the study region are contaminated with C. burnetii.

Conclusion

To our knowledge, this is the first report of highly heat-resistant zoonotic pathogen in raw-milk Brazilian artisanal cheese. This food safety hazard has been completely neglected in ready-to-eat raw-milk Brazilian artisanal cheese and could imply potential threats to consumers, since C. burnetii survives in artisanal cheese submitted to long ripening periods. Thus, this work established random and representative baseline prevalence of C. burnetii in this food product in Brazil. Further epidemiological studies, monitoring trends and setting control targets are warranted. Finally, these results point out the importance of including C. burnetii in animal and public health surveillance programs.

Q Fever Endocarditis in Iran

Patients with the underlying valvular heart disease are at the high risk of developing sub-acute or chronic endocarditis secondary to Coxiella burnetii. Q fever endocarditis is the most common manifestation along with persistent the infection. There is some serologic and molecular evidence of C. burnetii infection in humans and livestock in Iran. As it is possible to observe chronic Q fever in Iran, it seems necessary to study the prevalence of Q fever endocarditis in this country. In the present study, Infective Endocarditis (IE) patients (possible or definite based on Duke Criteria) hospitalized in Rajaie Cardiovascular Medical and Research Center were enrolled from August 2016 to September 2018. Culture-negative endocarditis patients were evaluated by Raoult criteria for diagnosis Q fever endocarditis. The serological results for brucellosis were negative for all subjects. All blood and tissue samples including valve samples were tested for C. burnetii infection using serology and Polymerase Chain Reaction (PCR). In this study, 126 patients who were admitted to the hospital were enrolled; of which 52 subjects were culture-negative IE. Among the participants, 16 patients (30.77%) were diagnosed with Q fever IE and underwent medical treatment. The mean age of patients was 46.6 years ranging from 23 to 69 years and 75% of them were male. Considering the high prevalence of Q fever IE, evaluation of the patients with culture-negative IE for C. burnetii infections was highly recommended.

Estimating the incubation period of acute Q fever, a systematic review

Estimates of the incubation period for Q fever vary substantially between different reviews and expert advice documents. We systematically reviewed and quality appraised the literature to provide an evidence-based estimate of the incubation period of the Q fever by the aerosolised infection route. Medline (OVIDSP) and EMBASE were searched with the search limited to human studies and English language. Eligible studies included persons with symptomatic, acute Q fever, and defined exposure to Coxiella burnetti. After review of 7115 titles and abstracts, 320 records were screened at full-text level. Of these, 23 studies contained potentially useful data and were quality assessed, with eight studies (with 403 individual cases where the derivation of incubation period was possible) being of sufficient quality and providing individual-level data to produce a pooled summary. We found a median incubation period of 18 days, with 95% of cases expected to occur between 7 and 32 days after exposure.

The clinical challenge of chronic Q fever with isolated liver involvement

Chronic Q fever is defined as an infection by Coxiella burnetii (C. burnetii) that lasts for six months or more. It occurs in 1-5% of individuals infected with this agent and develops over a period of months to years after the acute infection. Cases of hepatic involvement are rare.

Resolution of Q Fever-Associated Cryoglobulinemia With Anti-CD20 Monoclonal Antibody Treatment

Immunologic phenomena can complicate chronic infections with Coxiella burnetii (Q fever), including immune complex deposition causing vasculitis, neuropathy, and glomerulonephritis. We describe the case of a man with Q fever endocarditis, mixed cryoglobulinemia, and life-threatening vasculitis driven by immune complex deposition who was successfully treated with B cell depleting therapy (rituximab).

Chronic Q fever: A missed prosthetic valve endocarditis possibly for years

Chronic Coxiella burnetii endocarditis usually develops in people with underlying heart disease and accounts for 60–70% of chronic Q fever. Onset is generally insidious and manifestations are atypical. The authors report a case of Coxiella burnetii prosthetic valve endocarditis in a 53 years- old patient with recurrent mechanical valve dehiscence on mitral position. He lived in a rural area with sheep and goats on the surroundings. During a 9 year- period, he was submitted to three cardiac mitral valve surgeries two of which with no Q fever diagnosis suspicion. Diagnosis was based on a positive serology test (Indirect imunofluorescence). Treatment consisted in a combination of prolonged course of hydroxychloroquine plus doxycycline and surgical replacement of the mitral valve, with a favorable outcome. With this case report, the authors pretend to highlight the not always expected diagnosis of Q fever endocarditis. If not considered, Coxiella burnetii endocarditis may lead to multiple cardiac surgeries, greater morbidity and potentially death.

COMPARISON OF DIAGNOSTIC EFFECTIVENESS OF METHODS OF DETECTION OF COXIELLA BURNETII IN BLOOD OF PATIENTS WITH Q FEVER BASED ON AMPLIFICATION OF 16S rRNA GENE FRAGMENTS (STANDARD PCR) AND groEL GENE (REALTIME PCR)

Aim. Comparison of diagnostic capabilities of 2 variants of PCR for detection of Coxiella burnetii persistence in dynamics of infectious process in patients with Q fever. Materials and methods. 110 samples of clinical material, obtained from patients with Q fever in an endemic region for this infection (Astrakhan region), were studied. The samples were studied in a standard PCR (marker - 16S rRNA gene fragment) and in real-time PCR (RT-PCR) (marker - groEL gene fragment). Results. Both markers were established to be perspective for detection of C. burnetii DNA in clinical material, and RT-PCR detects positive result including late stages of the disease (illness day 21 - 31). Conclusion. This study is the first Russian publication on comparison on different PCR variants for detection of C. burnetii in blood of Q fever patients in dynamics of the infectious process.

Community-acquired pneumonia related to intracellular pathogens

Community-acquired pneumonia (CAP) is associated with high rates of morbidity and mortality worldwide; the annual incidence of CAP among adults in Europe has ranged from 1.5 to 1.7 per 1000 population. Intracellular bacteria are common causes of CAP. However, there is considerable variation in the reported incidence between countries and change over time. The intracellular pathogens that are well established as causes of pneumonia are Legionella pneumophila, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Chlamydophila psittaci, and Coxiella burnetii. Since it is known that antibiotic treatment for severe CAP is empiric and includes coverage of typical and atypical pathogens, microbiological diagnosis bears an important relationship to prognosis of pneumonia. Factors such as adequacy of initial antibiotic or early de-escalation of therapy are important variables associated with outcomes, especially in severe cases. Intracellular pathogens sometimes appear to cause more severe disease with respiratory failure and multisystem dysfunction associated with fatal outcomes. The clinical relevance of intracellular pathogens in severe CAP has not been specifically investigated. We review the prevalence, general characteristics, and outcomes of severe CAP cases caused by intracellular pathogens.

Brucellosis and Coxiella burnetii Infection in Householders and Their Animals in Secure Villages in Herat Province, Afghanistan: A Cross-Sectional Study

Background

Brucellosis and coxiellosis are known to be endemic in ruminant populations throughout Afghanistan, but information about their prevalence and factors that affect prevalence in householders and livestock under diverse husbandry systems and pastoral settings is sparse.

Methods/Principal Findings

We conducted a cross-sectional survey to investigate the seroprevalence of brucellosis and Coxiella burnetii in humans and livestock in six secure districts in Herat from 26^th December 2012–17^th January 2013. A total of 204 households with livestock were surveyed in six Kuchi and five sedentary type villages. Blood samples from 1,017 humans, 1,143 sheep, 876 goats and 344 cattle were tested for brucellosis and Q fever. About one in six households (15.7%) had at least one Brucella seropositive person, about one in eight households (12.3%) had at least one Brucella seropositive animal and about one in four (24.5%) had either seropositive animals or humans. Ninety-seven percent of households had at least one C. burnetii seropositive person and 98.5% of households had one or more C. burnetii seropositive animals. Forty- seven householders had serological evidence of exposure to both C. burnetii and Brucella and eight animals were serologically positive for both diseases. Drinking unpasteurised milk (OR 1.6), treating animals for ticks (OR 1.4), milking sheep (OR 1.4), male gender (OR 1.4) and seropositivity to Brucella (OR 4.3) were identified as risk factors for seropositivity to C. burnetii in householders. Household factors associated with households having either Brucella seropositive animals or humans were Kuchi households (OR 2.5), having ≤4 rooms in the house (OR 2.9) and not owning land (OR 2.9).

Conclusions

The results from this study provide baseline information for the planning and monitoring of future interventions against these diseases. The implementation of this study greatly improved collaboration, coordination and capability of veterinary and public health professionals from government, NGOs and donor funded projects.

Our study alerted authorities to a hitherto unrecognised high prevalence of C. burnetii infections, acted as a catalyst for the introduction of a national vaccination programme for protection of sheep and goats from brucellosis using Rev1 vaccine, demonstrated the benefits of a coordinated approach and fostered a better understanding of the nature of infection in different hosts and of the constraints for control faced by government services. A notable feature of the study was the enthusiasm and interest displayed by all of the participants throughout, from heads of government services to field personnel and villagers. Livestock owners regard zoonoses as adversities that affect their livestock and members of their households and do not partition them separately as medical or veterinary problems. Control programs need to take that perception into account and wherever possible avoid vesting ownership separately into veterinary or public health agencies.

Brucella and Coxiella; if you don't look, you don't find

Brucella and Coxiella are similar; both are obligate intracellular, zoonotic pathogens with a broad geographic distribution. Infection in animals is usually asymptomatic, but causes fetal loss and therefore has significant economic impact. Human infection may be asymptomatic or give rise to either organ-specific or multi-system disease. Organism culture is challenging for Coxiella and can lack sensitivity for Brucella. Therefore, infection is most commonly diagnosed by serology, but this may be negative in early infection and serology results may be challenging to interpret. Both Brucella and Coxiella are typically susceptible to a wide range of antimicrobials, but long courses may be needed.

Clinical microbiology of Coxiella burnetii and relevant aspects for the diagnosis and control of the zoonotic disease Q fever

Coxiella burnetii is the causative agent of the zoonotic disease Q fever. Since its first recognition as a disease in the 1930s, the knowledge about the agent and the disease itself has increased. This review summarizes the current knowledge on C. burnetii and Q fever, its pathogenesis, diagnosis and control. C. burnetii is a bacterium which naturally replicates inside human or animal host cells. The clinical presentation of Q fever varies per host species. C. burnetii infection in animals is mainly asymptomatic except for pregnant ruminants in which abortions and stillbirth can occur. In humans, the disease is also mainly asymptomatic, but clinical presentations include acute and chronic Q fever and the post-Q fever fatigue syndrome. Knowledge of the pathogenesis of Q fever in animals and excretion of C. burnetii in infected animals is crucial in understanding the transmission routes and risks of human infection. Our studies indicated that infected pregnant animals only excrete C. burnetii during and after parturition, independent of abortion, and that C. burnetii phase specific serology can be a useful tool in the early detection of infection. Domestic ruminants are the main reservoir for human Q fever, which has a major public health impact when outbreaks occur. In outbreaks, epidemiological source identification can only be refined by genotypic analysis of the strains involved. To control outbreaks and Q fever in domestic ruminants, vaccination with a phase 1 vaccine is effective. Future challenges are to identify factors for virulence, host susceptibility and protection.

Chronic q Fever with no elevation of inflammatory markers: a case report

We describe the case of a 55-year-old man with a biological prosthetic aortic valve who suffered from epigastrium and right hypochondrium pain associated with intermittent night sweats. Liver biopsy showed infectious hepatitis pattern without pathognomonic features. Coxiella burnetii serology was suggestive of chronic Q fever, and modified Duke's criteria for endocarditis were also fulfilled. The authors present a brief literature review concerning chronic Q fever, emphasizing absent previous reports of chronic Q fever with hepatitis and endocarditis and no increase in inflammatory markers.

Unusual manifestations of acute Q fever: autoimmune hemolytic anemia and tubulointerstitial nephritis

Q fever is a worldwide zoonotic infection that caused by Coxiella burnetii, a strict intracellular bacterium. It may be manifested by some of the autoimmune events and is classified into acute and chronic forms. The most frequent clinical manifestation of acute form is a self-limited febrile illness which is associated with severe headache, muscle ache, arthralgia and cough. Meningoencephalitis, thyroiditis, pericarditis, myocarditis, mesenteric lymphadenopathy, hemolytic anemia, and nephritis are rare manifestations. Here we present a case of acute Q fever together with Coombs’ positive autoimmune hemolytic anemia (AIHA) and tubulointerstitial nephritis treated with chlarithromycin, steroids and hemodialysis. Clinicians should be aware of such rare manifestations of the disease.

Effectiveness of vaccination and antibiotics to control Coxiella burnetii shedding around calving in dairy cows

Effectiveness of phase 1 vaccine, combined or not with tetracycline, to control Coxiella burnetii vaginal shedding at calving in cows was assessed through a 13 months study in 22 Q fever clinically affected commercial dairy herds. Four medical strategies implemented at herd level but randomly assigned to cows (vaccination, vaccination and tetracycline, tetracycline, nothing) were compared. There was no significant interaction effect between vaccination and antibiotherapy. Tetracycline used once at drying off was associated with a lower risk of being detected shedder at calving (OR=0.40, CI 95% [0.21-0.75]), but had no significant effect on the bacterial load shed. Vaccination did not significantly prevent shedding but was significantly (OR=0.15, CI 95% [0.03-0.85]) associated with lower bacterial load shed. Thus, vaccination using a phase 1 vaccine and antibiotherapy using tetracycline is associated with a decrease in shedding in dairy cows and could contribute to reduce the bacterial load generated in the environment. To the best of our knowledge, this is the first study providing useful information for evidenced-based and rational use of medical strategy combining antibiotic and vaccination in infected dairy cattle herds.

Screening-level risk assessment of Coxiella burnetii (Q fever) transmission via aeration of drinking water

A screening-level risk assessment of Q fever transmission through drinking water produced from groundwater in the vicinity of infected goat barnyards that employed aeration of the water was performed. Quantitative data from scientific literature were collected and a Quantitative Microbial Risk Assessment approach was followed. An exposure model was developed to calculate the dose to which consumers of aerated groundwater are exposed through aerosols inhalation during showering. The exposure assessment and hazard characterization were integrated in a screening-level risk characterization using a dose-response model for inhalation to determine the risk of Q fever through tap water. A nominal range sensitivity analysis was performed. The estimated risk of disease was lower than 10(-4) per person per year (pppy), hence the risk of transmission of C. burnetii through inhalation of drinking water aerosols is very low. The sensitivity analysis shows that the most uncertain parameters are the aeration process, the transport of C. burnetii in bioaerosols via the air, the aerosolization of C. burnetii in the shower, and the air filtration efficiency. The risk was compared to direct airborne exposure of persons in the vicinity of infected goat farms; the relative risk of exposure through inhalation of drinking water aerosols was 0.002%.

Lipopolysaccharide of Coxiella burnetii

A lipopolysaccharide (LPS) is considered to be one of the major determinants of virulence expression and infection of virulent Coxiella burnetii. The LPSs from virulent phase I (LPS I) and from avirulent phase II (LPS II) bacteria were investigated for their chemical composition, structure and biological properties. LPS II is of rough (R) type in contrast to LPS I, which is phenotypically smooth (S) and contains a noticeable amount of two sugars virenose (Vir) and dihydrohydroxystreptose (Strep), which have not been found in other LPSs and can be considered as unique biomarkers of the bacterium. Both sugars were suggested to be located mostly in terminal positions of the O-specific chain of LPS I (O-PS I) and to be involved in the immunobiology of Q fever. There is a need to establish a more detailed chemical structure of LPS I in connection with prospective, deeper studies on mechanisms of pathogenesis and immunity of Q fever, its early and reliable diagnosis, and effective prophylaxis against the disease. This will also help to better understanding of host-pathogen interactions and contribute to improved modulation of pathological reactions which in turn are prerequisite for research and development of vaccines of new type. A fundamental understanding of C. burnetii LPS biosynthesis is still lacking. The intracellular nature of the bacterium, lack of genetic tools and its status as a selected agent have made elucidating basic physiological mechanisms challenging. The GDP-β-D-Vir biosynthetic pathway proposed most recently is an important initial step in this endeavour. The current advanced technologies providing the genetic tools necessary to screen C. burnetii mutants and propagate isogenic mutants might speed the discovery process.

Q Fever: current state of knowledge and perspectives of research of a neglected zoonosis

Q fever is an ubiquitous zoonosis caused by an resistant intracellular bacterium, Coxiella burnetii. In certain areas, Q fever can be a severe public health problem, and awareness of the disease must be promoted worldwide. Nevertheless, knowledge of Coxiella burnetii remains limited to this day. Its resistant (intracellular and environmental) and infectious properties have been poorly investigated. Further understanding of the interactions between the infected host and the bacteria is necessary. Domestic ruminants are considered as the main reservoir of bacteria. Infected animals shed highly infectious organisms in milk, feces, urine, vaginal mucus, and, very importantly, birth products. Inhalation is the main route of infection. Frequently asymptomatic in humans and animals, Q fever can cause acute or chronic infections. Financial consequences of infection can be dramatic at herd level. Vaccination with inactive whole-cell bacteria has been performed and proved effective in humans and animals. However, inactive whole-cell vaccines present several defects. Recombinant vaccines have been developed in experimental conditions and have great potential for the future. Q fever is a challenging disease for scientists as significant further investigations are necessary. Great research opportunities are available to reach a better understanding and thus a better prevention and control of the infection.

Tortoise tick Hyalomma aegyptium as long term carrier of Q fever agent Coxiella burnetii--evidence from experimental infection

The experimental study investigated the ability of tortoise tick Hyalomma aegyptium to play a role in forming and maintaining natural foci of Q fever. We tested the competence of H. aegyptium larvae to acquire Coxiella burnetii infection from mammals, serve as a C. burnetii vector between mammalian hosts, and be a long-term carrier of C. burnetii, including interstadial transmission. H. aegyptium larvae were allowed to feed on guinea pigs experimentally infected with C. burnetii. Engorged larvae molted to nymphs, some of which were preserved in 96% ethanol and later examined by polymerase chain reaction (PCR) using C. burnetii-specific primers (CBCOS, CBCOE). Prevalence of C. burnetii among these nymphs was 5.6% (n=235). Remaining nymphs then fed on other, C. burnetii-negative guinea pigs; and according to results of both, micro-agglutination reaction, and ELISA, they successfully transmitted C. burnetii to those new hosts. Detached engorged nymphs molted to adults, which were kept alive long term and then placed in 96% ethanol 383 days post-infection. Thereafter, they were examined by PCR in the same manner as were the nymphs. Prevalence of C. burnetii among adult H. aegyptium was 28.9% (n=90). According to our results, tortoise-specific ticks have indisputable potential in the epidemiology of Q fever natural foci.

Prevalence of Coxiella burnetii antibodies in Danish dairy herds

During recent years in Denmark higher rates of antibodies to Coxiella burnetii have been detected in animals and humans than previously reported. A study based on bulk tank milk samples from 100 randomly selected dairy herds was performed to estimate the prevalence and geographical distribution of antibody positive dairy herds. Using the CHEKIT Q-Fever Antibody ELISA Test Kit (IDEXX), the study demonstrated a prevalence of 59% antibody positive herds, 11% antibody intermediate herds and 30% antibody negative herds based on the instructions provided by the manufacturer. The geographical distribution does not indicate a relationship between the regional density of dairy farms and the prevalence of antibody positive dairy farms. The result supports the hypothesis of an increase in the prevalence of positive dairy herds compared to previous years.

Coxiella burnetii glycomics and proteomics--tools for linking structure to function

Coxiella burnetii, the causative agent of Q fever, is an obligate intracellular bacterium and a highly infectious pathogen. The disease is a widespread zoonosis and is endemic throughout the world. An easy aerosol dissemination, environmental persistence, and high infectivity make the bacterium a serious threat for humans and animals. Lipopolysaccharide is considered one of the major factors of virulence expression and infection of the bacterium. Detailed glycomic studies enabled to better understand structural and functional peculiarities of this biopolymer and its role in pathogenesis and immunity of Q fever. Recent proteomic studies of C. burnetii have brought new approaches in accurate detection of the infectious agent and offered new insights into the inter- or intra-species relatedness. Thus, structure/function relationship studies are currently of utmost importance in the field. This paper will focus on glycomic and proteomic approaches providing information on unique glycan and protein species of the microorganism as the candidate molecules for the use in detection/diagnosis, therapy, and prophylaxis.

Q fever endocarditis; not always expected

Q fever endocarditis is a chronic disease with protean manifestations. The clinical and serological manifestations of nine patients diagnosed as having Q fever endocarditis during a 19-year period are reviewed. Four patients (44%) required valve replacement due to congestive heart failure. Three of these four patients were diagnosed as having Q fever endocarditis only after elective valve surgery, by histopathological examination of the valve and subsequent serological tests. Prior to surgery they were afebrile and had no other symptom or sign indicative of endocarditis. The antibiotic treatment and the decreasing titres of Q fever antibodies of all nine patients during several years of follow-up are summarized. Careful assessment of heart valves for histopathological evidence of inflammation is suggested, even after elective replacement. If found, clinical and laboratory evaluation should include determination of anti-Coxiella burnetti antibodies.

An economic evaluation of increased uptake in Q fever vaccination among meat and agricultural industry workers following implementation of the National Q Fever Management Program

INTRODUCTION

Q fever is a serious but vaccine-preventable infectious disease that predominantly affects those working in the meat and agricultural industries. In October 2000, the Commonwealth Government introduced the National Q Fever Management Program. This economic evaluation assesses the cost-effectiveness and cost-utility of improved vaccine uptake among meat and agricultural industry workers.

METHODS

Separate analyses were conducted for meat and agricultural industry workers. Clinical and epidemiological data used to create the models were obtained from published sources. Markov modelling was used to estimate the impact of Q fever vaccination uptake on the direct costs and outcomes of Q fever over a 20-year period.

RESULTS

Increasing vaccine uptake from 65% to 100% among meat industry workers results in an incremental cost per life year gained of $20,002, and a cost per QALY of $6,294. Increasing vaccine uptake from zero to 20% among agricultural industry workers results in an incremental cost per life year gained of $24,950, and a cost per QALY of $7,984. Including some indirect costs in the form of Workcover payments results in cost savings for both industry groups.

CONCLUSION

The results of this evaluation indicate that public health strategies to enhance the uptake of Q fever vaccine among high-risk workers potentially provides excellent value for the money invested.