Route of infection determines the clinical manifestations of acute Q fever

The integration of Coxiella burnetii PCR testing in serum into the diagnostic algorithm of suspected acute Q fever in an endemic setting

Serum polymerase chain reaction (PCR) for the detection of Coxiella burnetii DNA has been suggested for rapid Q fever diagnosis. We evaluated the role of PCR testing in serum in the diagnosis of acute Q fever in an endemic setting. We examined patients suspected of acute Q fever tested for C. burnetii-specific serum real-time PCR in a tertiary hospital between January 2019 toand December 2022. In the first half, PCR orders were consultation-based by infectious diseases specialists, while in the second half, they were guided by serology, positive IgM2, and negative IgG1 and IgG2, indicating early acute infection. Logistic regression analyzed independent predictors for positive PCR. PCR positivity rates were calculated using various clinical criteria in the diagnostic algorithm. Out of 272 patients, 13 (4.8%) tested positive and 130 exhibited serologically suspected early infection. Presentation during April-July and aspartate aminotransferase (AST) > 3× upper normal limit (UNL) were independently associated with positive PCR with an odds ratio (OR) = 15.03 [95% confidence interval (CI), 1.58-142.46], P = 0.018 and OR = 55.44 [95% CI, 6.16-498.69], P < 0.001, respectively. PCR positivity rate was 8.5% in serologically suspected early infection vs 1.4% in other serology, yielding OR = 6.4 [95% CI, 1.4-29.7], P = 0.009. Adding AST > 3× UNL increased OR to 49.5 [95% CI, 5.9-408.7], P ≤ 0.001 reducing required PCR tests for a single acute Q fever case from 11.8 to 3. Elevated AST in serologically suspected early Q fever is proposed to be used in a diagnostic stewardship algorithm integrating PCR in serum in an endemic setting.

IMPORTANCE

Our study suggests in a diagnostic stewardship approach the integration of molecular testing (Coxiella burnetii targeted PCR) for the diagnosis of acute Q fever in a reliable time in the endemic setting. Integrating PCR detecting Coxiella burnetii in serum in routine testing of suspected early acute Q fever based on serology result increased the PCR positivity rate significantly. Adding increased transaminases optimizes PCR utility which is highly requested particularly in endemic areas.

The lower Saint Lawrence River region of Quebec, a hot spot for sheepfold-associated Q fever in Canada: Review of 258 cases

Background

The lower Saint Lawrence river region (LSLRR), in Quebec, has a 10-fold higher incidence of Q fever compared to the provincial rate. This study aimed to review clinical cases and the Q fever risk exposure in this region.

Methods

Data were retrieved from microbiology laboratory, medical records from Rimouski Regional Hospital and Public Health reports between 1991 and 2018. They were analyzed with Epi Info 7.2.2.6. Patients with confirmed acute, probable acute, and chronic Q fever were classified using standard case definitions and mapped according to the postal code, to assess the correlation between cases and sheep distribution.

Results

Out of 295 cases, 258 were included (241 confirmed acute, seven probable acute, 10 chronic). Median age was 49 years, 76% were male. For acute cases, the prominent symptoms were fever (99%), headache (83%), chills (80%), sweating (72%), myalgia (69%), and fatigue (67%). Clinical presentation was mostly febrile syndrome with mild hepatitis (84%). A seasonal peak was observed from May to July (56% of acute cases). Most cases (56%) occurred within the two counties where sheep production was highest. Exposure to sheep was prominent 93%, including 64% direct contact (15% shepherds, 49% sheepfold visitors), 14% indirect contact, and 15% sheepfold neighbors.

Conclusions

To our knowledge, this is one of the largest retrospective studies of Q fever cases reported in Canada. Q fever in Quebec LSLRR is associated mainly with sheep exposure. Fever and hepatitis were the most common manifestations. Preventive measures should be considered in this region to protect sheepfold workers, visitors, and their neighbors.

Molecular detection of Coxiella burnetii in raw meat samples collected from different abattoirs in districts Kasur and Lahore of Punjab, Pakistan

Coxiella burnetii is the zoonotic pathogen that causes Q fever; it is widespread globally. Livestock animals are its main reservoir, and infected animals shed C. burnetii in their birth products, feces, vaginal mucus, urine, tissues, and food obtained from them, i.e., milk and meat. There were previously very few reports on the prevalence of C. burnetii in raw meat. This study aimed to determine the prevalence of C.burnetii and its molecular characterization in raw ruminant meat from the Kasur and Lahore districts in Punjab, Pakistan, as this has not been reported so far. In this study, 200 meat samples, 50 from each species of cattle, buffalo, goat, and sheep, were collected from the slaughterhouses in each district, Kasur and Lahore in 2021 and 2022. PCR was used for the detection of the IS1111 element of C. burnetii. The data were recorded and univariate analysis was performed to determine the frequency of C. burnetii DNA in raw meat samples obtained from different ruminant species using the SAS 9.4 statistical package. Of the total of 200 raw meat samples, C. burnetii DNA was present in 40 (20%) of them, tested by PCR using the IS1111 sequence. The prevalence of C.burnetii differed among the studied species of ruminants. When species were compared pairwise, the prevalence in cattle was statistically significantly lower than in sheep (P = 0.005). The sequence alignment based on origin implied that the strains are genetically diverse in different districts of Punjab, Pakistan. The findings demonstrated that the prevalence of C. burnetii, especially in raw meat samples, deserves more attention from the health care system and professionals from Punjab, Pakistan, i.e., abattoir workers and veterinarians.

Risk factors associated with self-reported Q fever in Australian wildlife rehabilitators: Findings from an online survey

Australian wildlife rehabilitators (AWR) are at increased risk of developing Q fever, a serious zoonotic disease caused by the intracellular bacterium Coxiella burnetii. Previous studies have suggested that Australian wildlife may be a potential C. burnetii infection source for humans. However, a recent serological survey of AWR found no association between C. burnetii exposure and direct contact with any wildlife species. To further explore the potential risk that wildlife may pose, this study aimed to identify associations between self-reported Q fever in AWR and risk factors for exposure to C. burnetii. An online cross-sectional survey was implemented in 2018 targeting AWR nationwide. Risk factors for self-reported Q fever were determined using multivariable logistic regression. Medically diagnosed Q fever was self-reported in 4.5% (13/287) of unvaccinated respondents. Rehabilitators who self-reported medically diagnosed Q fever were significantly more likely to: primarily rehabilitate wildlife at a veterinary clinic (OR 17.87, 95% CI: 3.09-110.92), have domestic ruminants residing on the property where they rehabilitate wildlife (OR 11.75, 95% CI: 2.91-57.42), have been educated at a High School/Technical and Further Education level (OR 10.29, 95% CI: 2.13-84.03) and be aged >50 years (OR 6.61, 95% CI: 1.60-38.35). No association was found between self-reported Q fever and direct contact with wildlife. These findings support previous work suggesting that AWR are at increased risk of C. burnetii infection and may develop Q fever potentially via exposure to traditional infection sources including livestock, other domestic animals, or contaminated environments, in association with their rehabilitation practices and lifestyle. Although Q fever vaccination is recommended for AWR, vaccine uptake is low in this population. Future studies should aim to determine the level of Q fever awareness and identify barriers to Q fever vaccination in this at-risk group. The difficulty in accessing the AWR population also highlights the need for a national centralized AWR database.

Preclinical Animal Models for Q Fever Vaccine Development

Coxiella burnetii is a zoonotic pathogen responsible for the human disease Q fever. While an inactivated whole cell vaccine exists for this disease, its widespread use is precluded by a post vaccination hypersensitivity response. Efforts for the development of an improved Q fever vaccine are intricately connected to the availability of appropriate animal models of human disease. Accordingly, small mammals and non-human primates have been utilized for vaccine-challenge and post vaccination hypersensitivity modeling. Here, we review the animal models historically utilized in Q fever vaccine development, describe recent advances in this area, discuss the limitations and strengths of these models, and summarize the needs and criteria for future modeling efforts. In summary, while many useful models for Q fever vaccine development exist, there remains room for growth and expansion of these models which will in turn increase our understanding of C. burnetii host interactions.

Natural genetic variation in Drosophila melanogaster reveals genes associated with Coxiella burnetii infection

The gram-negative bacterium Coxiella burnetii is the causative agent of Query (Q) fever in humans and coxiellosis in livestock. Host genetics are associated with C. burnetii pathogenesis both in humans and animals; however, it remains unknown if specific genes are associated with severity of infection. We employed the Drosophila Genetics Reference Panel to perform a genome-wide association study to identify host genetic variants that affect host survival to C. burnetii infection. The genome-wide association study identified 64 unique variants (P < 10⁻⁵) associated with 25 candidate genes. We examined the role each candidate gene contributes to host survival during C. burnetii infection using flies carrying a null mutation or RNAi knockdown of each candidate. We validated 15 of the 25 candidate genes using at least one method. This is the first report establishing involvement of many of these genes or their homologs with C. burnetii susceptibility in any system. Among the validated genes, FER and tara play roles in the JAK/STAT, JNK, and decapentaplegic/TGF-β signaling pathways which are components of known innate immune responses to C. burnetii infection. CG42673 and DIP-ε play roles in bacterial infection and synaptic signaling but have no previous association with C. burnetii pathogenesis. Furthermore, since the mammalian ortholog of CG13404 (PLGRKT) is an important regulator of macrophage function, CG13404 could play a role in host susceptibility to C. burnetii through hemocyte regulation. These insights provide a foundation for further investigation regarding the genetics of C. burnetii susceptibility across a wide variety of hosts.

Pathologic changes and immune responses against Coxiella burnetii in mice following infection via non-invasive intratracheal inoculation

Q fever is a worldwide zoonosis caused by Coxiella burnetii. Human Q fever is typically acquired through inhalation of contaminated aerosols, resulting in an initial pulmonary infection. In this study, BALB/c mice were infected with C. burnetii via an intratracheal (IT) route using a non-invasive aerosol pulmonary delivery device to directly place the living C. burnetii organisms into the lungs of the mice. The bacterial loads, pathological lesions, and antibody and cellular responses were analyzed and compared with those of mice infected via an intraperitoneal (IP) route. Compared with mice infected via an IP route, mice infected via an IT route exhibited a higher bacterial load and more severe pathological lesions in the heart and lungs at days 3 and 7 post-infection (pi). The levels of interferon-γ and IL-12p70 in the serum of mice infected via the IT route were significantly higher than those of mice infected via the IP route at day 3 pi. In conclusion, this murine model of acute C. burnetii infection via IT inoculation closely resembles the natural route of C. burnetii infection than that of IP injection. Thus, this newly developed model will be useful for investigating the pathogenesis and immunity of C. burnetii aerosol infection, as well as for the evaluation of therapeutic drugs and preventive vaccines of Q fever.

Coxiella burnetii Intratracheal Aerosol Infection Model in Mice, Guinea Pigs, and Nonhuman Primates

Coxiella burnetii, the etiological agent of Q fever, is a Gram-negative bacterium transmitted to humans by inhalation of contaminated aerosols. Acute Q fever is often self-limiting, presenting as a febrile illness that can result in atypical pneumonia. In some cases, Q fever becomes chronic, leading to endocarditis that can be life threatening. The formalin-inactivated whole-cell vaccine (WCV) confers long-term protection but has significant side effects when administered to presensitized individuals. Designing new vaccines against C. burnetii remains a challenge and requires the use of clinically relevant modes of transmission in appropriate animal models. We have developed a safe and reproducible C. burnetii aerosol challenge in three different animal models to evaluate the effects of pulmonary acquired infection. Using a MicroSprayer aerosolizer, BL/6 mice and Hartley guinea pigs were infected intratracheally with C. burnetii Nine Mile phase I (NMI) and demonstrated susceptibility as determined by measuring bacterial growth in the lungs and subsequent dissemination to the spleen. Histological analysis of lung tissue showed significant pathology associated with disease, which was more severe in guinea pigs. Infection using large-particle aerosol (LPA) delivery was further confirmed in nonhuman primates, which developed fever and pneumonia. We also demonstrate that vaccinating mice and guinea pigs with WCV prior to LPA challenge is capable of eliciting protective immunity that significantly reduces splenomegaly and the bacterial burden in spleen and lung tissues. These data suggest that these models can have appreciable value in using the LPA delivery system to study pulmonary Q fever pathogenesis as well as designing vaccine countermeasures to C. burnetii aerosol transmission.

Clinical characteristics of acute Q fever patients in South Korea and time from symptom onset to serologic diagnosis

BACKGROUND

Acute Q fever usually presents as a nonspecific febrile illness, and its occurrence is rapidly increasing in South Korea. This study investigated the clinical characteristics of acute Q fever patients in South Korea and the time from symptom onset to serologic diagnosis. The clinical courses were examined according to antibiotic treatment.

METHODS

Data of patients diagnosed with acute Q fever at Chungbuk National University Hospital between January 2015 and February 2018 were retrospectively collected. Demographic and epidemiologic data were reviewed. The time from symptom onset to serologic diagnosis by an immunofluorescence assay (IFA) was analyzed. Clinical courses and the percentage of patients with a high phase I immunoglobulin G titer (≥ 1:1024) were compared between patients administered antibiotics with anti-Coxiella burnetii activity and patients not administered such antibiotics.

RESULTS

Forty-eight patients (median age: 51.5 years) were included. Most were male (95.8%) and had no history of animal contact (91.7%). The median time from illness onset to serologic diagnosis was 21 days. Thirty-nine patients received antibiotics with anti-C. burnetii activity. The length of hospital stay and fever duration did not significantly differ between patients who received antibiotics with anti-C. burnetii activity (7 and 15 days) and those who did not (5 and 8 days) (P = 0.110 and P = 0.137, respectively). The percentage of patients with a high phase I immunoglobulin G titer (≥ 1:1024) did not significantly differ between patients who received antibiotics with anti-C. burnetii activity and those who did not (P = 0.340).

CONCLUSIONS

Most acute Q fever patients had a nonspecific febrile illness with mild elevation of transaminases and no history of animal contact or occupational risk. The time from symptom onset to a positive IFA test was longer than the fever duration in most acute Q fever patients. Consequently, it may be difficult for clinicians to serologically diagnose acute Q fever. However, inappropriate antibiotic treatment was not associated with prolongation of symptoms or progression to chronic Q fever.

The hypervirulent Coxiella burnetii Guiana strain compared in silico, in vitro and in vivo to the Nine Mile and the German strain

OBJECTIVE

Q fever epidemic outbreaks have been reported in French Guiana and in The Netherlands. To determine whether the C. burnetii strains involved in these epidemics had a peculiar virulence pattern, we compared the pathogenicity of the Guiana and the German strain (a clone of The Netherlands strain), in silico, in vitro, and in vivo versus the Nine Mile strain.

METHOD

The pan-genomes of the Guiana (Cb175), German (Z3055), and the referent Nine Mile (RSA 493) C. burnetii strains were compared. In vitro, the growth rate and the morphological presentation were compared. In vivo (SCID and Balb/c mice), weight loss, histological lesions, C. burnetii bacterial load in deep organs, and serological response were reported according to each C. burnetii strain studied.

RESULTS

The Guiana strain had 77 times more missing genes and 12 times more unique genes than the German strain. The Guiana strain presented as large cell variants (LCVs) and led to the most pronounced fatality rate in SCID mice (100% at 4 weeks). The German strain presented as small cell variants (SCVs), and had an intermediate fatality rate (75% at 4 weeks). Both the Guiana and the German strains led to a significant higher serological response at 2 and 4 weeks post infection (p <0.05).

CONCLUSION

The Guiana strain was the most virulent strain, followed by the German strain and the referent Nine Mile strain. Unique and missing genes could be implicated but further investigations are necessary to specify their role.

Presentation and diagnosis of acute Q fever in Portugal - A case series

Q fever is a worldwide zoonotic infection caused by the obligate intracellular bacterium Coxiella burnetii that can course with acute or chronic disease.

This series describes 7 cases of acute Q fever admitted in a Portuguese University Hospital between 2014 and 2015.

All cases presented with hepatitis and had epidemiological history. Diagnosis was done by PCR on majority (5) and by serology and PCR in only 2.

Serological tests can be negative in the initial period of the disease. Molecular biology methods by polymerase chain-reaction are extremely important in acute disease, allowing timely diagnosis and treatment.

Mouse Model of Coxiella burnetii Aerosolization

Coxiella burnetii is mainly transmitted by aerosols and is responsible for multiple-organ lesions. Animal models have shown C. burnetii pathogenicity, but long-term outcomes still need to be clarified. We used a whole-body aerosol inhalation exposure system to mimic the natural route of infection in immunocompetent (BALB/c) and severe combined immunodeficient (SCID) mice. After an initial lung inoculum of 10(4) C. burnetii cells/lung, the outcome, serological response, hematological disorders, and deep organ lesions were described up to 3 months postinfection. C. burnetii-specific PCR, anti-C. burnetii immunohistochemistry, and fluorescent in situ hybridization (FISH) targeting C. burnetii-specific 16S rRNA completed the detection of the bacterium in the tissues. In BALB/c mice, a thrombocytopenia and lymphopenia were first observed, prior to evidence of C. burnetii replication. In all SCID mouse organs, DNA copies increased to higher levels over time than in BALB/c ones. Clinical signs of discomfort appeared in SCID mice, so follow-up had to be shortened to 2 months in this group. At this stage, all animals presented bone, cervical, and heart lesions. The presence of C. burnetii could be attested in situ for all organs sampled using immunohistochemistry and FISH. This mouse model described C. burnetii Nine Mile strain spread using aerosolization in a way that corroborates the pathogenicity of Q fever described in humans and completes previously published data in mouse models. C. burnetii infection occurring after aerosolization in mice thus seems to be a useful tool to compare the pathogenicity of different strains of C. burnetii.

[Description of a case of severe Q fever]

The paper considers a rare clinical case of severe Q fever in a young man with no compromised premorbid background. It describes and analyzes clinical manifestations and laboratory findings with consideration for the current data available in the literature. The issues of the differential diagnosis, laboratory diagnosis, and treatment of Q fever are discussed.

Clinical characteristics of Q fever and etiology of community-acquired pneumonia in a tropical region of southern Taiwan: a prospective observational study

Background

The clinical characteristics of Q fever are poorly identified in the tropics. Fever with pneumonia or hepatitis are the dominant presentations of acute Q fever, which exhibits geographic variability. In southern Taiwan, which is located in a tropical region, the role of Q fever in community-acquired pneumonia (CAP) has never been investigated.

Methodology/Principal Findings

During the study period, May 2012 to April 2013, 166 cases of adult CAP and 15 cases of acute Q fever were prospectively investigated. Cultures of clinical specimens, urine antigen tests for Streptococcus pneumoniae and Legionella pneumophila, and paired serologic assessments for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Q fever (Coxiella burnetii) were used for identifying pathogens associated with CAP. From April 2004 to April 2013 (the pre-study period), 122 cases of acute Q fever were also included retrospectively for analysis. The geographic distribution of Q fever and CAP cases was similar. Q fever cases were identified in warmer seasons and younger ages than CAP. Based on multivariate analysis, male gender, chills, thrombocytopenia, and elevated liver enzymes were independent characteristics associated with Q fever. In patients with Q fever, 95% and 13.5% of cases presented with hepatitis and pneumonia, respectively. Twelve (7.2%) cases of CAP were seropositive for C. burnetii antibodies, but none of them had acute Q fever. Among CAP cases, 22.9% had a CURB-65 score ≧2, and 45.8% had identifiable pathogens. Haemophilus parainfluenzae (14.5%), S. pneumoniae (6.6%), Pseudomonas aeruginosa (4.8%), and Klebsiella pneumoniae (3.0%) were the most common pathogens identified by cultures or urine antigen tests. Moreover, M. pneumoniae, C. pneumoniae, and co-infection with 2 pathogens accounted for 9.0%, 7.8%, and 1.8%, respectively.

Conclusions

In southern Taiwan, Q fever is an endemic disease with hepatitis as the major presentation and is not a common etiology of CAP.

Comparison between emerging Q fever in French Guiana and endemic Q fever in Marseille, France

Q fever is an emergent disease in French Guiana. We compared the incidence clinical and serologic profiles between patients from Cayenne, French Guiana and Marseille in metropolitan France during a four-year period. The annual incidence of diagnosed acute Q fever was significantly higher in Cayenne (17.5/100,000) than in Marseille (1.9/100,000) (P = 0.0004), but not the annual incidence of endocarditis (1.29 versus 0.34/100,000). Most patients had fever (97%) and pneumonia (83%) in Cayenne versus 81% and 8% in Marseille (P < 0.0001 and P < 0.0001, respectively) but transaminitis was more common in patients from Marseille (54% versus 32%; P < 0.0001). The proportion of patients with cardiovascular infections was significantly lower in Cayenne (7%) than in Marseille (17%) (P = 0.017), although they showed a stronger immune response with higher levels of phase I IgG (P = 0.024). The differing epidemiology, clinical, and serologic responses of patients from Cayenne and Marseille suggest a different source of infection and a different strain of Coxiella burnetii.

Characteristics of hospitalized acute Q fever patients during a large epidemic, The Netherlands

BACKGROUND

From 2007 to 2009, The Netherlands experienced a major Q fever epidemic, with higher hospitalization rates than the 2-5% reported in the literature for acute Q fever pneumonia and hepatitis. We describe epidemiological and clinical features of hospitalized acute Q fever patients and compared patients presenting with Q fever pneumonia with patients admitted for other forms of community-acquired pneumonia (CAP). We also examined whether proximity to infected ruminant farms was a risk factor for hospitalization.

METHODS

A retrospective cohort study was conducted for all patients diagnosed and hospitalized with acute Q fever between 2007 and 2009 in one general hospital situated in the high incidence area in the south of The Netherlands. Pneumonia severity scores (PSI and CURB-65) of acute Q fever pneumonia patients (defined as infiltrate on a chest x-ray) were compared with data from CAP patients. Hepatitis was defined as a >twofold the reference value for alanine aminotransferase and for bilirubin.

RESULTS

Among the 183 hospitalized acute Q fever patients, 86.0% had pneumonia. Elevated liver enzymes (alanine aminotransferase) were found in 32.3% of patients, although hepatitis was not observed in any of them. The most frequent clinical signs upon presentation were fever, cough and dyspnoea. The median duration of admission was five days. Acute Q fever pneumonia patients were younger, had less co-morbidity, and lower PSI and CURB-65 scores than other CAP patients. Anecdotal information from attending physicians suggests that some patients were admitted because of severe subjective dyspnoea, which was not included in the scoring systems. Proximity to an infected ruminant farm was not associated with hospitalization.

CONCLUSION

Hospitalized Dutch acute Q fever patients mostly presented with fever and pneumonia. Patients with acute Q fever pneumonia were hospitalized despite low PSI and CURB-65 scores, presumably because subjective dyspnoea was not included in the scoring systems.

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.

Acute Q fever in Portugal. Epidemiological and clinical features of 32 hospitalized patients

INTRODUCTION

Q fever is a worldwide zoonosis caused by Coxiella burnetii. The main characteristic of acute Q fever is its clinical polymorphism, usually presenting as a febrile illness with varying degrees of hepatitis and/or pneumonia. Q fever is endemic in Portugal, and it is an obligatory notifiable disease since 1999. However, its epidemiological and clinical characteristics are still incompletely described.

METHODS

We performed a retrospective study of 32 cases admitted in the Infectious Diseases Department, Santa Maria's University Hospital, from January 2001 to December 2010, in whom acute Q fever was diagnosed by the presence of antibodies to phase II Coxiella burnetii antigens associated with a compatible clinical syndrome.

RESULTS

Out of the 32 cases recorded, 29 (91%) were male, with a male:female ratio of 9.7:1. Individuals at productive age were mainly affected (88%, n=28, with ages between 25 and 64 years). Clinically, the most common manifestation of acute Q fever was hepatic involvement (84%, n=27), which occurred isolated in 53% (n=17) of the cases. Hepatitis was more severe, presenting with higher values of liver function tests, in patients presenting both pulmonary and hepatic involvement. Additionally, we report one case of myocarditis and another one with neurological involvement. Empiric but appropriate antibiotic therapy was given in 66% (n=21) of the cases. There was a complete recovery in 94% (n=30) of the patients, and one death. We confirmed the sub-notification of this disease in Portugal, with only 47% (n=15) of the cases notified.

CONCLUSION

In Portugal further studies are needed to confirm our results. From the 32 cases studied, acute Q fever presented more frequently as a febrile disease with hepatic involvement affecting mainly young male individuals. Furthermore, acute Q fever is clearly underdiagnosed and underreported in Portugal, which suggests that an increased awareness of the disease is needed, together with a broader use of serological testing.

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.

Q fever: the neglected biothreat agent

Coxiella burnetii is the causative agent of Q fever, a disease with a spectrum of presentations from the mild to fatal, including chronic sequelae. Since its discovery in 1935, it has been shown to infect a wide range of hosts, including humans. A recent outbreak in Europe reminds us that this is still a significant pathogen of concern, very transmissible and with a very low infectious dose. For these reasons it has also featured regularly on various threat lists, as it may be considered by the unscrupulous for use as a bioweapon. As an intracellular pathogen, it has remained an enigmatic organism due to the inability to culture it on laboratory media. As a result, interactions with the host have been difficult to elucidate and we still have a very limited understanding of the molecular mechanisms of virulence. However, two recent developments will open up our understanding of C. burnetii: the first axenic growth medium capable of supporting cell-free growth, and the production of the first isogenic mutant. We are approaching an exciting time for expanding our knowledge of this organism in the next few years.

In search of hidden Q-fever outbreaks: linking syndromic hospital clusters to infected goat farms

Large Q-fever outbreaks were reported in The Netherlands from May 2007 to 2009, with dairy-goat farms as the putative source. Since Q-fever outbreaks at such farms were first reported in 2005, we explored whether there was evidence of human outbreaks before May 2007. Space–time scan statistics were used to look for clusters of lower-respiratory infections (LRIs), hepatitis, and/or endocarditis in hospitalizations, 2005–2007. We assessed whether these were plausibly caused by Q fever, using patients' age, discharge diagnoses, indications for other causes, and overlap with reported Q fever in goats/humans. For seven detected LRI clusters and one hepatitis cluster, we considered Q fever a plausible cause. One of these clusters reflected the recognized May 2007 outbreak. Real-time syndromic surveillance would have detected four of the other clusters in 2007, one in 2006 and two in 2005, which might have resulted in detection of Q-fever outbreaks up to 2 years earlier.

[Severe cholestatic hepatitis due to Q fever: report of a case]

Severe cholestatic hepatitis due to Coxiella burnetii is a rare form of clinical presentation of acute Q fever that is only occasionally detected in association with this infectious disease. We report a case of severe cholestatic hepatitis due to acute Q fever, with clinical signs of hepatic insufficiency, marked cholestasis, and renal insufficiency. The results of the initial serologic study using a complement fixation test were negative on two occasions, and transjugular biopsy and serological analysis with indirect immunofluorescence were required to establish the diagnosis. Despite treatment with doxycycline and ciprofloxacin, the cholestasis progressively worsened, with the development of hepatic and renal insufficiency, which rapidly disappeared after corticosteroid treatment.

Coxiella burnetii isolates cause genogroup-specific virulence in mouse and guinea pig models of acute Q fever

Q fever is a zoonotic disease of worldwide significance caused by the obligate intracellular bacterium Coxiella burnetii. Humans with Q fever may experience an acute flu-like illness and pneumonia and/or chronic hepatitis or endocarditis. Various markers demonstrate significant phylogenetic separation between and clustering among isolates from acute and chronic human disease. The clinical and pathological responses to infection with phase I C. burnetii isolates from the following four genomic groups were evaluated in immunocompetent and immunocompromised mice and in guinea pig infection models: group I (Nine Mile, African, and Ohio), group IV (Priscilla and P), group V (G and S), and group VI (Dugway). Isolates from all of the groups produced disease in the SCID mouse model, and genogroup-consistent trends were noted in cytokine production in response to infection in the immunocompetent-mouse model. Guinea pigs developed severe acute disease when aerosol challenged with group I isolates, mild to moderate acute disease in response to group V isolates, and no acute disease when infected with group IV and VI isolates. C. burnetii isolates have a range of disease potentials; isolates within the same genomic group cause similar pathological responses, and there is a clear distinction in strain virulence between these genomic groups.

Severe Q fever community-acquired pneumonia (CAP) mimicking Legionnaires' disease: Clinical significance of cold agglutinins, anti-smooth muscle antibodies and thrombocytosis

Atypical community-acquired pneumonia (CAP) may be caused by zoonotic or nonpulmonary pathogens. However, atypical pathogens are systemic infectious disease accompanied by pneumonia in contrast with typical bacterial pathogens with infection limited to the lungs and absent extrapulmonary findings. Clinically and radiologically, the atypical CAP pathogens that most closely resemble each other are psittacosis, Q fever, and Legionnaires' disease. Psittacosis can usually be readily suspected or eliminated on the basis of a recent psittacine bird contact history. The 2 atypical pneumonias that most closely resemble each other clinically are Q fever and Legionnaires' disease. The epidemiology of Q fever is related to livestock, and sporadic cases are related to contact to parturient cats. In nonendemic areas, Q fever CAP mimics Legionnaires' disease most closely. Both Q fever and Legionella CAP have several clinical and laboratory features in common. However, there are subtle but important differences that allow the astute clinician to differentiate between these 2 disorders on the basis of clinical and nonspecific laboratory findings before definitive diagnostic tests results are reported. We report a case of severe Q fever CAP mimicking Legionnaires' disease in a young adult normal host. Her initial zoonotic contact history was negative, and her clinical presentation suggested Legionnaires' disease as the most likely diagnosis. Against the diagnosis of Legionnaires' disease was the patient's age and occurrence of the disease in spring time. In contrast, Legionnaires' disease is usually an infection of older individuals and occurs in late summer/fall. Although the patient did not have splenomegaly, a common finding in Q fever CAP, she did have mild hepatomegaly. Hepatomegaly is a uncommon in Q fever CAP but is not a feature of Legionnaires' disease. In the absence of a positive zoonotic contact history, the cardinal findings pointing to the diagnosis of Q fever in this case were "multiple round opacities" on chest computed tomography scan and thrombocytosis during her hospitalization. Against the diagnosis of Legionnaires' disease was the absence of hypophosphatemia and highly elevated ferritin levels. In patients with atypical pneumonias in whom the clinical presentation and nonspecific laboratory findings suggest Legionnaires' disease, but in addition have findings not associated with Legionnaires' (eg, hepatomegaly, thrombocytosis), Q fever serology should be ordered. We conclude that Q fever may closely mimic Legionnaires' disease. Severe atypical CAP with "multiple round opacities" on chest x-ray/computed tomography chest scan with elevated anti-smooth muscle antibodies or thrombocytosis should suggest the diagnosis of Q fever and prompt specific testing for Q fever. Rarely, Q fever CAP may be associated with elevated cold agglutinin titers.

Acute Q fever: an emerging and endemic disease in southern Taiwan

Acute Q fever is a worldwide zoonosis caused by Coxiella burnetii infection. In Taiwan, cases of acute Q fever increased during 3 y of observation, especially at Kaohsiung County and City in southern Taiwan. From 15 April 2004 to 15 April 2007, a total of 67 cases of acute Q fever were identified at E-Da hospital located at Kaohsiung County. 19 (28.4%) patients had a history of travel in rural areas and only 1 had been outside southern Taiwan. 21 (31.3%) patients had a history of animal contact. 20 (30.8%) of the 65 examined patients had underlying chronic hepatitis B or hepatitis C virus infection. Fever (98.5%), chills (79.1%), headache (79.1%), relative bradycardia (44.8%), elevated aminotransferases (100%), and thrombocytopenia (74.6%) were common manifestations. 12 (19.0%) cases had abnormal findings on chest X-ray. Fatty liver (50.0%) and hepatomegaly and/or splenomegaly (41.9%) were found by abdominal image examinations. 42 (76.4%) of 55 cases had defervescence within 3 d after treatment, whereas 4 (7.3%) had spontaneous remission. Acute Q fever is an endemic infectious disease with hepatitis rather than pneumonia as the major presentation in southern Taiwan and the emergence of Q fever is due to increased alertness for the disease by physicians.

[Q Fever in Tunisia]

Q fever is a common zoonosis with almost a worldwide distribution caused by Coxiella burnetii. Farm animals and pets are the main reservoirs of infection and transmission to humans is usually via inhalation of contaminated aerosols. Infection in humans is often asymptomatic, but it can manifest as an acute disease (usually a self-limited flu-like illness, pneumonia or hepatitis) or as a chronic form (mainly endocarditis, but also hepatitis and chronic-fatigue syndrome). In Tunisia, although prevalence of anti-Coxiella burnetii was high among blood donors, Q fever was rarely reported and frequently miss diagnosed by physicians. This study is a review of epidemiological and clinical particularities of Q fever in Tunisia.

Coxiella burnetii Infection

Coxiella burnetii is an obligate intracellular bacterium that causes a worldwide zoonosis, Q fever, and can be misused as a biological warfare agent. Infection in animals (coxiellosis) is mostly persistent. Infection in humans is often asymptomatic, but it can manifest as an acute disease (usually a self-limited flu-like illness, pneumonia, or hepatitis) or as a chronic form (mainly endocarditis, but also hepatitis and chronic fatigue syndrome). C. burnetii infection in pregnant women may result in abortions, premature deliveries, and stillbirths. Infection in nature is maintained and transmitted by ticks as the principal vector and reservoir. Cattle, sheep, and goats are the most important source of human infections. Humans contract C. burnetii infection mostly by aerosol in contact with contaminated environs, wind playing an important factor in spreading the infection. The wide distribution of C. burnetii contributes to a high resistance of its extracellular small cell variant to environmental conditions. Its intracellular large cell variant, adapted to survive under harsh conditions of phagolysosomes, enables long-term survival and persistence of C. burnetii, namely in monocytes/macrophages. Host factors such as underlying disease and cell-mediated immunity play a decisive role in the clinical expression of C. burnetii infection. Complete genome analysis of C. burnetii will certainly contribute to better understanding of the pathogenesis of C. burnetii infection and will improve Q fever diagnosis and immunoprophylaxis.

Natural history and pathophysiology of Q fever

Q fever is a zoonosis caused by Coxiella burnetii. Infection with C burnetii can be acute or chronic, and exhibits a wide spectrum of clinical manifestations. The extreme infectivity of the bacterium results in large outbreaks and makes it a potential bioweapon. In the past decade, the complete genome sequencing of C burnetii, the exploration of bacterial interactions with the host, and the description of the natural history of the disease in human beings and in experimental models have all added to our knowledge about this fascinating disease. Advances in understanding the pathophysiology and natural history of Q fever are reviewed.

Q fever pneumonia: virulence of Coxiella burnetii pathovars in a murine model of aerosol infection

Q fever is a worldwide zoonosis caused by Coxiella burnetii, a strictly intracellular bacterium that is a potential bioweapon. Humans usually acquires Q fever after inhalation of dust infected by subclinical animals. We used an aerosol exposure apparatus to challenge immunocompetent (BALB/c) and severe combined immunodeficient (SCID) mice with two different strains (strain Nine Mile and strain Q 212) of C. burnetii at two different inocula. Pathological lesions and dissemination of the bacteria were related to the size of the inoculum. SCID mice showed major pulmonary lesions, whereas similarly infected BALB/c mice were more able to eliminate the bacteria. Pathological differences were found between the strains, with Nine Mile showing more severe histological lesions and quantified spread of bacteria. Our animal model could provide a new tool for the study of acute Q fever pneumonia, the development of Q fever in immunodeficient hosts, and the differentiation of pathogenicity among C. burnetii isolates.

Pseudoepidemic of Q Fever at an Animal Research Facility

Serum samples from people exposed to sheep at a research facility were evaluated by a commercial laboratory and resulted in an overall Coxiella burnetii seroprevalence of 75%. We interviewed individuals to determine exposure history and compatible illness, and retested their sera. Analysis indicated that the commercial laboratory was misinterpreting its results; when corrected, the seroprevalence dropped to 27%. Test kits of the brand used by the commercial laboratory gave equivalent results to the in-house CDC assay when tested in parallel at CDC. Upon final analysis, only the attending veterinarian was confirmed as a Q fever case. This event resulted in increased risk reduction protocols at the research facility and improved public health communication among health authorities. This pseudoepidemic resulted from a lapse in laboratory quality control for testing. Similar errors can be avoided through standardization and improved review of laboratory procedures.

Q fever: a biological weapon in your backyard

Coxiella burnetii, which causes Q fever, is a highly infectious agent that is widespread among livestock around the world. Although the culture process for coxiella is laborious, large amounts of infectious material can be produced. If used as an aerosolised biological weapon, coxiella may not cause high mortality, but could provoke acute disabling disease. In its late course, Q fever can be complicated by fatal (eg, endocarditis) or debilitating (eg, chronic fatigue syndrome) disorders. The diagnosis of Q fever might be delayed because of non-specific and protean presentations. Effective antibiotic treatment is available for the acute form of disease but not for the chronic complications. Vaccination and chemoprophylaxis in selected individuals may be used in the event of bioterrorism.

SCID mouse model for lethal Q fever

Q fever, a worldwide zoonosis caused by Coxiella burnetii, has many manifestations in humans. Endocarditis is the most serious complication of Q fever. Animal models are limited to acute pulmonary or hepatic disease and reproductive disorders. An appropriate experimental animal model for Q fever endocarditis does not yet exist. In this study, severe combined immunodeficient (SCID) mice infected with C. burnetii showed persistent clinical symptoms and died, whereas immunocompetent mice similarly infected became asymptomatic and survived. The SCID mice examined in this study had severe chronic lesions in their primary organs: the heart, lung, spleen, liver, and kidney. The heart lesions of the SCID mice were similar to those in humans with chronic Q fever endocarditis: they had focal calcification and expanded macrophages containing C. burnetii. The 50% lethal dose of C. burnetii in SCID mice was at least 10(8) times less than that in immunocompetent mice. The SCID mouse is highly susceptible to C. burnetii, and the immunodeficiency of the host enhances the severity of Q fever. This animal model could provide a new tool for the study of chronic Q fever and Q fever in immunodeficient hosts.

Q fever: epidemiology, clinical features and prognosis. A study from 1983 to 1999 in the South of Spain

OBJECTIVES

Clinical polymorphism is a main feature of Q fever and, depending upon the geographic location, differences in its clinical picture have been described. The objective of this study was to determine the epidemiology, clinical features and prognosis of acute Q fever in our area.

METHODS

From 1985 to 1999, consecutive cases of Q fever, presented as febrile syndrome and attended in a tertiary teaching hospital in Sevilla, Spain, were included and followed prospectively.

RESULTS

Two hundred and thirty-one cases of acute Q fever were included. A non-focalized febrile syndrome lasting from 7 to 28 days (fever of intermediate duration) was the most frequent presentation (n=208, 90%). One hundred and forty-eight patients had hepatitis. Overall, 53% of the cases were urban and contact with animals was referred in 39% of the patients. No relationship between clinical presentation and possible route of infection was observed. Prognosis was excellent (100% cured), although in 18 patients fever was prolonged more than 28 days and three patients developed life-threatening organ affection. Antimicrobial treatment was more effective if it was administered in the first two weeks (median defervescence of fever: 3 days versus 5.5 days, p<0.01).

CONCLUSIONS

Acute Q fever is a common cause of fever of intermediate duration, even in urban areas. Elevation of hepatic enzymes was the most frequent laboratory finding. Severe organ affection is uncommon and the overall prognosis of the disease is excellent. Early treatment seems to shorten the duration of the disease.

Q fever in adults: review of 66 clinical cases

Sixty-six cases of Q fever in adults, serologically confirmed by indirect immunofluorescence, were studied to analyze the epidemiological, clinical and therapeutic aspects of the disease. Eighty-three percent of the patients were male, and the mean age was 44.7 years. Contact with animals was recorded in 24 patients. The main clinical form of presentation was pneumonia (37 cases); eight patients had hypoxia, and five had respiratory failure. The empirical treatment consisted of macrolides in 36% of cases. Evolution was favorable in all cases.

Myocarditis, a rare but severe manifestation of Q fever: report of 8 cases and review of the literature

Myocarditis has only rarely been described as a manifestation of acute Q fever. Among our series of 1276 patients in whom acute Q fever was diagnosed during 1985--1999, myocarditis was diagnosed in 8. Two patients (25.0%) developed cardiac symptoms during the course of interstitial pneumonia, 2 (25.0%) initially presented with unexplained fever, and 1 (12.5%) presented with febrile cutaneous rash. In 3 patients, cardiac symptoms were inaugural: 1 patient experienced heart failure, and 2 experienced precordial pain. Dilated cardiomyopathy was documented in 7 patients, and 2 (1 of whom had undergone heart transplantation) died despite therapy. In addition, 1 patient was scheduled for heart transplantation because of cardiac insufficiency. When the patients in this study were compared with 32 control patients with acute Q fever, no specific epidemiological or clinical features were associated with this disease except worse prognosis (P=.006). Moreover, among the 12 patients from our series who died as a result of acute Q fever, 2 patients, who were significantly younger than the other 9 patients (P=.03), had myocarditis. Our study highlights the severity of Coxiella burnetii myocarditis.

Q fever epidemiology and pathogenesis

The lungs are a port of entry and primary infectious focus of Coxiella burnetii, the obligate intracellular contagium of the worldwide zoonosis Q fever. The infectious process and immune response are characterised by studies in cell culture and animal systems. Following endocytosis, replication exclusively occurs in the phagolysosome. Several potential virulence factors are described.