Cell death induction facilitates egress of Coxiella burnetii from infected host cells at late stages of infection

Intracellular bacteria have evolved mechanisms to invade host cells, establish an intracellular niche that allows survival and replication, produce progeny, and exit the host cell after completion of the replication cycle to infect new target cells. Bacteria exit their host cell by (i) initiation of apoptosis, (ii) lytic cell death, and (iii) exocytosis. While bacterial egress is essential for bacterial spreading and, thus, pathogenesis, we currently lack information about egress mechanisms for the obligate intracellular pathogen C. burnetii, the causative agent of the zoonosis Q fever. Here, we demonstrate that C. burnetii inhibits host cell apoptosis early during infection, but induces and/or increases apoptosis at later stages of infection. Only at later stages of infection did we observe C. burnetii egress, which depends on previously established large bacteria-filled vacuoles and a functional intrinsic apoptotic cascade. The released bacteria are not enclosed by a host cell membrane and can infect and replicate in new target cells. In summary, our data argue that C. burnetii egress in a non-synchronous way at late stages of infection. Apoptosis-induction is important for C. burnetii egress, but other pathways most likely contribute.

Q fever screening among pregnant women with pre-term delivery in northern Israel: An observational study

The relationship between Q fever, caused by Coxiella burnetii, and obstetrical complications is debatable. Since Q fever is endemic in Israel, we aimed to assess its seroprevalence and clinical characteristics in pre-term deliveries. Between 1 August 2017 and 31 December 2019, we conducted serological screening for C. burnetii in pregnant women who presented to Rambam Health Care Campus with pre-term delivery (before 37 weeks of gestation). Anti-C. burnetii antibodies were tested first by enzyme-linked immunosorbent assay for the detection of phase I-IgG, phase II-IgG and phase II-IgM. Positive results were confirmed by indirect immunofluorescence with titre determination. Seropositivity was classified into past, acute and chronic infection. Demographic and clinical data of mothers and neonates were collected and compared between seropositive and seronegative women. Out of 386 pregnant women screened for anti-C. burnetii antibodies, 16 (4.1%) were seropositive, of whom three were diagnosed with past, 12 with acute and one with chronic infection. A higher percentage of seropositive women were immunosuppressed, 2/16 (12.5%) compared with 7/370 (1.9%) in seronegative women, (p = .05). Neonates with small for gestational age were born to 2/16 (12.5%) seropositive women compared with 29/370 (7.8%) to seronegative women, (p = .35). The seroprevalence of Q fever among pregnant women with pre-term birth reached 4% in northern Israel. This high rate in an endemic setting encourages investigating the role of routine screening for Q fever during pregnancy. Special attention should be given to pregnant immunosuppressed women at risk for exposure to Q fever.

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.

Coxiella burnetii (Q-fever) outbreak associated with non-occupational exposure in a semi-urban area of western Croatia in 2022

In March 2022, an outbreak of Q fever (Coxiella burnetii) with non-occupational exposure was confirmed in a semi-urban area in Čavle, Croatia. Veterinary and human epidemiological investigations were conducted to identify the source of the outbreak and to implement appropriate control measures. Three farms were settled next to each other near the homes of the first human cases at the end of the street. The closest farm was less than 500 meters away. These farms contained 161 adult sheep and goats. Among the animal samples analysed, all 16 goats (100%) and 24/50 sheep (48%) tested positive for C. burnetii IgM/IgG antibodies, phase I and II. One out of five sheeps' vaginal swabs were C. burnetti DNA positive. Human testing revealed 20 confirmed and three probable cases (9/23 pneumonia, 2/23 hepatitis, 21/23 fever), with three hospitalizations, and one death. Twenty-seven cases were discarded following negative laboratory results. The epidemiological investigation revealed airborne transmission as the most likely route of transmission. Multiple logistic regression analyses were used to evaluate risk factors for Q fever infection. Persons who were near the farms (≤750 m) (OR 4.5; 95% CI = 1.1-18.3) and lived in the nearest street to the farms had the highest risk of contracting Q fever (OR 3.7; 95% CI = 1.1-13.6). Decreased rainfall compared to monthly averages was recorded in the months prior to the outbreak with several days of strong wind in January preceding the outbreak. This was the largest Q fever outbreak in the county in the last 16 years, which was unexpected due to its location and non-occupational exposure. To stop the outbreak, numerous intensive biosecurity measures were implemented. The outbreak highlights the importance of urban development strategies to limit the number of animal housing near residential areas while providing regular biosecurity measures to prevent infections in livestock.

Macrophages inhibit Coxiella burnetii by the ACOD1-itaconate pathway for containment of Q fever

Infection with the intracellular bacterium Coxiella (C.) burnetii can cause chronic Q fever with severe complications and limited treatment options. Here, we identify the enzyme cis-aconitate decarboxylase 1 (ACOD1 or IRG1) and its product itaconate as protective host immune pathway in Q fever. Infection of mice with C. burnetii induced expression of several anti-microbial candidate genes, including Acod1. In macrophages, Acod1 was essential for restricting C. burnetii replication, while other antimicrobial pathways were dispensable. Intratracheal or intraperitoneal infection of Acod1^-/- mice caused increased C. burnetii burden, weight loss and stronger inflammatory gene expression. Exogenously added itaconate restored pathogen control in Acod1^-/- mouse macrophages and blocked replication in human macrophages. In axenic cultures, itaconate directly inhibited growth of C. burnetii. Finally, treatment of infected Acod1^-/- mice with itaconate efficiently reduced the tissue pathogen load. Thus, ACOD1-derived itaconate is a key factor in the macrophage-mediated defense against C. burnetii and may be exploited for novel therapeutic approaches in chronic Q fever.

Q Fever awareness and risk profiles among agricultural show attendees

OBJECTIVE

To assess awareness and risk of Q fever among agricultural show attendees.

SETTING

University of New England's Farm of the Future Pavilion, 2019, Sydney Royal Agricultural Show.

PARTICIPANTS

Participants were ≥18 years, fluent in English, Australian residents, and gave their informed consent.

MAIN OUTCOME MEASURES

Participants reported whether they had ever heard of Q fever and then completed the 'Q Tool' (www.qfevertool.com), which was used to assess participants' demographics and risk profiles. Cross-tabulations and logistic regression analyses were used to examine the relationship between these factors.

RESULTS

A total of 344 participants were recruited who, in general, lived in major NSW cities and were aged 40-59 years. 62% were aware of Q fever. Living in regional/remote areas and regular contact with livestock, farms, abattoirs and/or feedlots increased the likelihood of Q fever awareness. Direct or indirect contact with feral animals was not associated with Q fever awareness after controlling for the latter risk factors. 40% of participants had a high, 21% a medium, and 30% a low risk of exposure. Slightly less than 10% reported a likely existing immunity or vaccination against Q fever. Among those who were not immune, living in a regional or remote area and Q fever awareness were independently associated with increased likelihood of exposure.

CONCLUSIONS

Awareness of Q fever was relatively high. Although 61% of participants had a moderate to high risk of exposure to Q fever, they had not been vaccinated. This highlights the need to explore barriers to vaccination including accessibility of providers and associated cost.

Urban landscape and infection risk in free-roaming cats

Despite public concern on the role of free‐roaming cats as reservoirs of zoonotic agents, little is known about the influence of urban and peri‐urban landscapes on the exposure risk. We evaluated the seroprevalence of three zoonotic agents (Chlamydia felis, Coxiella burnetii and Toxoplasma gondii) in domestic cats (Felis catus). Two hundred and ninety‐one free‐roaming cats were trapped in Murcia municipality (Southeast Spain), and their sera were tested for specific antibodies against T. gondii using a modified agglutination test (MAT), and for C. felis, C. burnetii and feline immunodeficiency virus (FIV) antibodies with ELISA technique. Pathogen seroprevalence at 95% CI was calculated for each sex and age category (up to and over 12 months) and compared with a chi‐squared test. The role of human population density and urban landscape characteristics on the risk of pathogen exposure in the cat population was explored using generalized linear models. Seropositivity against a single pathogen was found in 60% of the cats, while 19% was seropositive for two or three pathogens. Seroprevalence of C. felis was 8% (CI_95%: 5–11), 37% (CI_95%: 31–42) for C. burnetii and 42% (CI_95%: 36–47) for T. gondii. In addition to these three pathogens, FIV seropositivity was low (1%, CI_95%: −0.1 to 2) and adult cats were more likely to be seropositive to C. burnetii than young individuals (OR: 2.3, CI_95%: 1.2–4.2). No sex or age class differences in seroprevalence were observed for the rest of the pathogens. Seropositivity was correlated with water surface areas for C. felis, and not with crop areas. Coxiella burnetii seropositivity was correlated with the percentage of urban areas (continuous with only buildings and discontinuous, that include buildings, parks, and pedestrian and urban green areas), human population size and peri‐urban areas with shrubs, and not correlated with other agricultural landscapes (orchards and crop areas). However, the seroprevalence of T. gondii was only associated with agricultural landscapes such as orchards. The detection of hotspot areas of high pathogen exposure risk is the basis for municipal services to implement surveillance and risk factor control campaigns in specific‐risk areas, including (a) efficient health management of urban cat colonies by geographical location, population census and health status monitoring of the components of each cat colony, (b) improvement of hygiene and sanitary conditions at the feeding points of the cat colony and (c) free‐roaming cat trapping for health monitoring and, in the long term, to know the evolution of the health status of their populations.

Perturbation of ATG16L1 function impairs the biogenesis of Salmonella and Coxiella replication vacuoles

Anti-bacterial autophagy, known as xenophagy, is a host innate immune response that targets invading pathogens for degradation. Some intracellular bacteria, such as the enteric pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium), utilize effector proteins to interfere with autophagy. One such S. Typhimurium effector, SopF, inhibits recruitment of ATG16L1 to damaged Salmonella-containing vacuoles (SCVs), thereby inhibiting the host xenophagic response. SopF is also required to maintain the integrity of the SCV during the early stages of infection. Here we show disruption of the SopF-ATG16L1 interaction leads to an increased proportion of cytosolic S. Typhimurium. Furthermore, SopF was utilized as a molecular tool to examine the requirement for ATG16L1 in the intracellular lifestyle of Coxiella burnetii, a bacterium that requires a functional autophagy pathway to replicate efficiently and form a single, spacious vacuole called the Coxiella-containing vacuole (CCV). ATG16L1 is required for CCV expansion and fusion but does not influence C. burnetii replication. In contrast, SopF did not affect CCV formation or replication, demonstrating that the contribution of ATG16L1 to CCV biogenesis is via its role in autophagy, not xenophagy. This study highlights the diverse capabilities of bacterial effector proteins to dissect the molecular details of host-pathogen interactions.

Acute and chronic Q fever national surveillance - United States, 2008-2017

Q fever is a zoonotic disease caused by the bacterium Coxiella burnetii and can manifest in an acute or chronic form. Many persons with acute Q fever are asymptomatic, but some develop a febrile illness, pneumonia or hepatitis. Chronic infections are rare and occur in less than 5% of persons exposed. Forms of chronic Q fever include endocarditis, infection of vascular grafts or aneurysms, osteomyelitis and osteoarthritis. Acute and chronic Q fever are nationally notifiable diseases, and presented here are the incidence, demographics and distribution of acute and chronic Q fever in the United States during 2008-2017. We summarized passive surveillance data from the Centers for Disease Control and Prevention's (CDC) National Notifiable Diseases Surveillance System (NNDSS) and supplemental case report forms (CRFs). Health departments reported 1,109 cases of acute Q fever and 272 chronic Q fever cases to NNDSS during this period. The 10-year average annual incidence for acute Q fever was 0.36 cases per million persons, and the average annual incidence for chronic Q fever was 0.09. Males accounted for nearly 75% of both acute and chronic Q fever cases. Average annual incidence was highest among persons aged 60-69 years for both acute and chronic Q fever (0.70 cases per million persons and 0.25, respectively). As reported through CRFs, many Q fever cases did not have a known exposure to C. burnetii; 60% (n = 380) of acute Q fever cases did not report exposure to animals in the 2 months before symptom onset. Almost 90% (n = 558) did not report exposure to unpasteurized milk. Only 40% (n = 247) of persons with reported Q fever were employed in high-risk occupations. Even though Q fever is a rare disease in the United States, incidence doubled from 2008 to 2017.

Molecular detection of Coxiella burnetii infection in small mammals from Moshi Rural and Urban Districts, northern Tanzania

Coxiella burnetii is an obligate intracellular bacterium that causes Q fever, a zoonotic disease of public health importance. In northern Tanzania, Q fever is a known cause of human febrile illness, but little is known about its distribution in animal hosts. We used a quantitative real-time PCR (qPCR) targeting the insertion element IS1111 to determine the presence and prevalence of C. burnetii infections in small mammals trapped in 12 villages around Moshi Rural and Moshi Urban Districts, northern Tanzania. A total of 382 trapped small mammals of seven species were included in the study; Rattus rattus (n = 317), Mus musculus (n = 44), Mastomys natalensis (n = 8), Acomys wilson (n = 6), Mus minutoides (n = 3), Paraxerus flavovottis (n = 3) and Atelerix albiventris (n = 1). Overall, 12 (3.1%) of 382 (95% CI: 1.6-5.4) small mammal spleens were positive for C. burnetii DNA. Coxiella burnetii DNA was detected in five of seven of the small mammal species trapped; R. rattus (n = 7), M. musculus (n = 1), A. wilson (n = 2), P. flavovottis (n = 1) and A. albiventris (n = 1). Eleven (91.7%) of twelve (95% CI: 61.5-99.8) C. burnetii DNA positive small mammals were trapped within Moshi Urban District. These findings demonstrate that small mammals in Moshi, northern Tanzania are hosts of C. burnetii and may act as a source of C. burnetii infection to humans and other animals. This detection of C. burnetii infections in small mammals should motivate further studies into the contribution of small mammals to the transmission of C. burnetii to humans and animals in this region.

Unravelling animal exposure profiles of human Q fever cases in Queensland, Australia, using natural language processing

Q fever, caused by the zoonotic bacterium Coxiella burnetii, is a globally distributed emerging infectious disease. Livestock are the most important zoonotic transmission sources, yet infection in people without livestock exposure is common. Identifying potential exposure pathways is necessary to design effective interventions and aid outbreak prevention. We used natural language processing and graphical network methods to provide insights into how Q fever notifications are associated with variation in patient occupations or lifestyles. Using an 18-year time-series of Q fever notifications in Queensland, Australia, we used topic models to test whether compositions of patient answers to follow-up exposure questionnaires varied between demographic groups or across geographical areas. To determine heterogeneity in possible zoonotic exposures, we explored patterns of livestock and game animal co-exposures using Markov Random Fields models. Finally, to identify possible correlates of Q fever case severity, we modelled patient probabilities of being hospitalized as a function of particular exposures. Different demographic groups consistently reported distinct sets of exposure terms and were concentrated in different areas of the state, suggesting the presence of multiple transmission pathways. Macropod exposure was commonly reported among Q fever cases, even when exposure to cattle, sheep or goats was absent. Males, older patients and those that reported macropod exposure were more likely to be hospitalized due to Q fever infection. Our study indicates that follow-up surveillance combined with text modelling is useful for unravelling exposure pathways in the battle to reduce Q fever incidence and associated morbidity.

Chronic Q fever associated with systemic sclerosis

BACKGROUND

After the Q fever outbreak in the Netherlands between 2007 and 2010, more than 300 patients with chronic Q fever have been identified. Some patients were also diagnosed with systemic sclerosis, a rare immune-mediated disease. We aimed to increase awareness of concomitant chronic Q fever infection and systemic sclerosis and to give insight into the course of systemic sclerosis during persistent Q fever infection.

MATERIALS AND METHODS

Chronic Q fever patients were identified after the Dutch Q fever outbreak in 2007-2010. Systemic sclerosis was diagnosed by a scleroderma expert and patients fulfilled the 2013 Classification Criteria for Systemic Sclerosis.

RESULTS

Four cases presented with chronic Q fever, persistent Coxiella burnetii infection, shortly preceded or followed by the diagnosis of limited cutaneous systemic sclerosis. The three male patients of 60 years or older developed a relatively mild systemic sclerosis, which did not require immunosuppressive therapy during adequate treatment of the chronic Q fever infection. The 58-year-old female patient used immunosuppressives for her newly diagnosed systemic sclerosis at the time she likely developed a chronic Q fever infection.

CONCLUSIONS

In this case series, chronic Q fever preceding systemic sclerosis was associated with a mild course of systemic sclerosis without the necessity of immunosuppressive drugs, while chronic Q fever development due to immunocompromised state was associated with a more deteriorating course of systemic sclerosis.

Unusual presentation of Q fever in a kidney-pancreas transplant recipient

Q fever is uncommon in solid organ transplant (SOT) recipients. We describe a case of granulomatous lung disease as an unusual presentation of chronic Q fever in a kidney-pancreas transplant recipient.

Use of a Dose-Response Model to Study Temporal Trends in Spatial Exposure to Coxiella burnetii: Analysis of a Multiyear Outbreak of Q Fever

The Netherlands underwent a large Q fever outbreak between 2007 and 2009. In this paper, we study spatial and temporal Coxiella burnetii exposure trends during this large outbreak as well as validate outcomes against other published studies and provide evidence to support hypotheses on the causes of the outbreak. To achieve this, we develop a framework using a dose-response model to translate acute Q fever case incidence into exposure estimates. More specifically, we incorporate a geostatistical model that accounts for spatial and temporal correlation of exposure estimates from a human Q fever dose-response model to quantify exposure trends during the outbreak. The 2051 cases, with the corresponding age, gender and residential addresses, reside in the region with the highest attack rates during the outbreak in the Netherlands between 2006 and 2009. We conclude that the multiyear outbreak in the Netherlands is caused by sustained release of infectious bacteria from the same sources, which suggests that earlier implementation of interventions may have prevented many of the cases. The model predicts the risk of infection and acute symptomatic Q fever from multiple exposure sources during a multiple-year outbreak providing a robust, evidence-based methodology to support decision-making and intervention design.