Detection of Coxiella burnetii from dust in a barn housing dairy cattle

Coxiella burnetii in the environment: A systematic review and critical appraisal of sampling methods

Q fever is a zoonotic disease caused by the intracellular bacterium, Coxiella burnetii. Its primary mode of transmission is by inhalation of aerosols originating from infected animals and contaminated environments. The organism has a very low infective dose, can persist in the environment for long periods of time and large outbreaks fuelled by windborne spread have been previously reported. Detection of C. burnetii in the environment is therefore important during human and animal outbreak investigations and for the control and prevention of Q fever. This study aimed to systematically review and critically appraise the published literature on sampling methods used to detect C. burnetii from different environmental samples. A search of four electronic databases with subsequent hand searching identified 47 eligible articles published since 1935. These articles described sampling of dust, air, soil and liquids in attempts to detect C. burnetii during 19 Q fever outbreaks and in 28 endemic settings. Environmental positivity was most commonly associated with ruminant livestock populations. Evidence describing spatio-temporal characteristics and associated geographical dispersion gradients was limited. The most commonly tested sample type was dust which also yielded the highest bacterial loads of >10⁸ bacteria/cloth. The MD8 (Sartorius) air sampler was used widely for air sampling. Soil was the only sample type for which a validated laboratory protocol was established specifically for C. burnetii. Each environmental sample type has its advantages and limitations which are discussed in detail and a simplified framework to guide decisions around environmental sampling for C. burnetii is provided. In any type of environmental sampling, it is recommended to use standardized and validated methods and to match the most ideal sampling strategy and timing with the research context. These conditions are essential to be considered when designing future Q fever management plans that involve environmental sampling for C. burnetii.

Domestic sheep show average Coxiella burnetii seropositivity generations after a sheep-associated human Q fever outbreak and lack detectable shedding by placental, vaginal, and fecal routes

Coxiella burnetii is a globally distributed zoonotic bacterial pathogen that causes abortions in ruminant livestock. In humans, an influenza-like illness results with the potential for hospitalization, chronic infection, abortion, and fatal endocarditis. Ruminant livestock, particularly small ruminants, are hypothesized to be the primary transmission source to humans. A recent Netherlands outbreak from 2007–2010 traced to dairy goats resulted in over 4,100 human cases with estimated costs of more than 300 million euros. Smaller human Q fever outbreaks of small ruminant origin have occurred in the United States, and characterizing shedding is important to understand the risk of future outbreaks. In this study, we assessed bacterial shedding and seroprevalence in 100 sheep from an Idaho location associated with a 1984 human Q fever outbreak. We observed 5% seropositivity, which was not significantly different from the national average of 2.7% for the U.S. (P>0.05). Furthermore, C. burnetii was not detected by quantitative PCR from placentas, vaginal swabs, or fecal samples. Specifically, a three-target quantitative PCR of placenta identified 0.0% shedding (exact 95% confidence interval: 0.0%-2.9%). While presence of seropositive individuals demonstrates some historical C. burnetii exposure, the placental sample confidence interval suggests 2016 shedding events were rare or absent. The location maintained the flock with little or no depopulation in 1984 and without C. burnetii vaccination during or since 1984. It is not clear how a zero-shedding rate was achieved in these sheep beyond natural immunity, and more work is required to discover and assess possible factors that may contribute towards achieving zero-shedding status. We provide the first U.S. sheep placental C. burnetii shedding update in over 60 years and demonstrate potential for C. burnetii shedding to reach undetectable levels after an outbreak event even in the absence of targeted interventions, such as vaccination.

Circulation of Coxiella burnetii in a Naturally Infected Flock of Dairy Sheep: Shedding Dynamics, Environmental Contamination, and Genotype Diversity

Q fever is a worldwide zoonosis caused by Coxiella burnetii. Domestic ruminants are considered to be the main reservoir. Sheep, in particular, may frequently cause outbreaks in humans. Because within-flock circulation data are essential to implementing optimal management strategies, we performed a follow-up study of a naturally infected flock of dairy sheep. We aimed to (i) describe C. burnetii shedding dynamics by sampling vaginal mucus, feces, and milk, (ii) assess circulating strain diversity, and (iii) quantify barn environmental contamination. For 8 months, we sampled vaginal mucus and feces every 3 weeks from aborting and nonaborting ewes (n=11 and n=26, respectively); for lactating females, milk was obtained as well. We also sampled vaginal mucus from nine ewe lambs. Dust and air samples were collected every 3 and 6 weeks, respectively. All samples were screened using real-time PCR, and strongly positive samples were further analyzed using quantitative PCR. Vaginal and fecal samples with sufficient bacterial burdens were then genotyped by multiple-locus variable-number tandem-repeat analysis (MLVA) using 17 markers. C. burnetii burdens were higher in vaginal mucus and feces than in milk, and they peaked in the first 3 weeks postabortion or postpartum. Primiparous females and aborting females tended to shed C. burnetii longer and have higher bacterial burdens than nonaborting and multiparous females. Six genotype clusters were identified; they were independent of abortion status, and within-individual genotype diversity was observed. C. burnetii was also detected in air and dust samples. Further studies should determine whether the within-flock circulation dynamics observed here are generalizable.

Selected Zoonoses

Human risks of acquiring a zoonotic disease from animals used in biomedical research have declined over the last decade because higher quality research animals have defined microbiologic profiles. Even with diminished risks, the potential for exposure to infectious agents still exists, especially from larger species such as nonhuman primates, which may be obtained from the wild, and from livestock, dogs, ferrets, and cats, which are generally not raised in barrier facilities and are not subject to the intensive health monitoring performed routinely on laboratory rodents and rabbits. Additionally, when laboratory animals are used as models for infectious disease studies, exposure to microbial pathogens presents a threat to human health. Also, with the recognition of emerging diseases, some of which are zoonotic, constant vigilance and surveillance of laboratory animals for zoonotic diseases are still required.

Vaccination using phase I vaccine is effective to control Coxiella burnetii shedding in infected dairy cattle herds

The effectiveness of the vaccination of dairy cows combined or not with antibiotics (i.e. oxytetracycline) to control Coxiella burnetii (Cb) shedding at herd level was investigated in 77 Q fever clinically affected herds. In addition to nulliparous heifers' vaccination, one out of the four following medical strategies was randomly assigned to dairy cows in each herd: vaccination (using a phase I vaccine) alone, vaccination combined with oxytetracycline, oxytetracycline alone or nothing. Their effectiveness to reduce Cb load in quarterly samples of bulk tank milk (BTM) and of pooled milk of primiparous (MP) was assessed through logistic hierarchical models. A significant reduction in Cb load was observed in herds where the vaccination of ≥80% of dairy cows was implemented; whereas the use of antibiotics was uneffective. Our findings support the interest of a whole vaccination strategy and provide evidence for decreasing the use of antibiotics in dairy cattle herds.

Detection of Coxiella burnetii DNA in the environment during and after a large Q fever epidemic in the Netherlands

AIM

To investigate the Coxiella burnetii DNA content in environmental samples that may contribute to the transmission of C. burnetii.

METHODS AND RESULTS

During a large Q fever outbreak in the Netherlands, surface swabs and aerosol samples were collected inside stables and around six Q fever-affected ruminant farms, which are located in municipalities varying in Q fever incidence. After the outbreak in 2010, aerosol samples were collected in the same geographical areas. The use of an optimized multiplex qPCR for the detection of C. burnetii DNA revealed that all samples obtained inside stables were positive. In addition, the C. burnetii DNA content in aerosol samples collected in stables is significantly higher than in aerosol samples collected around the farms. Finally, the C. burnetii DNA content in aerosol samples collected in the same geographical locations was lower in 2010 in comparison with 2009.

CONCLUSIONS

The reduction in C. burnetii DNA content in aerosol samples between 2009 and 2010 is in agreement with the reduction in Q fever incidence in the same geographical areas.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of C. burnetii DNA in environmental samples collected on and around ruminant farms supports the hypothesis that C. burnetii can be disseminated from ruminant farms to the surrounding areas.

Detection of Coxiella burnetii DNA on small-ruminant farms during a Q fever outbreak in the Netherlands

During large Q fever outbreaks in the Netherlands between 2007 and 2010, dairy goat farms were implicated as the primary source of human Q fever. The transmission of Coxiella burnetii to humans is thought to occur primarily via aerosols, although available data on C. burnetii in aerosols and other environmental matrices are limited. During the outbreak of 2009, 19 dairy goat farms and one dairy sheep farm were selected nationwide to investigate the presence of C. burnetii DNA in vaginal swabs, manure, surface area swabs, milk unit filters, and aerosols. Four of these farms had a positive status during the Coxiella burnetii bulk milk monitoring program in 2009 and additionally reported abortion waves in 2008 or 2009. Eleven farms were reported as having positive bulk milk only, and five selected (control) farms had a bulk milk-negative status in 2009 and no reported Q fever history. Screening by quantitative PCR (qPCR) revealed that on farms with a history of abortions related to C. burnetii and, to a lesser extent, on farms positive by bulk milk monitoring, generally higher proportions of positive samples and higher levels of C. burnetii DNA within positive samples were observed than on the control farms. The relatively high levels of C. burnetii DNA in surface area swabs and aerosols sampled in stables of bulk milk-positive farms, including farms with a Q fever-related abortion history, support the hypothesis that these farms can pose a risk for the transmission of C. burnetii to humans.

Coxiella burnetii shedding and environmental contamination at lambing in two highly naturally-infected dairy sheep flocks after vaccination

Abortion due to Coxiella burnetii was confirmed in the 2007/08 season in two naturally-infected dairy sheep flocks. Proportion of C. burnetii shedders and bacterial loads in vaginal mucus were high among aborted or lambed ewes, as was within-flock seroprevalence. Before the next reproductive season (2008/09) 75% of ewes and 50% of replacement lambs were vaccinated (Coxevac, CEVA Santé Animale) keeping the remaining as untreated controls. Compared with the previous year results when abortion outbreak started, a great reduction in the percentage of abortions, in the number of shedders and in the bacterial burden excreted by the ewes was found in both flocks. However, seroconversion in non-vaccinated yearlings from both flocks and the presence of C. burnetii DNA in bioaerosols taken at sheep premises at lambing indicated that infection was still active. No differences were observed between vaccinated and control groups in terms of proportion of C. burnetii shedders. These results suggest that optimal results of vaccination in heavily infected flocks may not be obtained in a short-term period.

Effect of vaccination with phase I and phase II Coxiella burnetii vaccines in pregnant goats

Livestock is considered to be the major "source" of human Q fever. The efficacy of two currently available vaccines (Coxevac, phase I, CEVA Santé Animale and Chlamyvax FQ, phase II, MERIAL) against Coxiella excretion was investigated in terms of risks to human health. Two months before mating, 17 goats were vaccinated subcutaneously against Coxiella burnetii with an inactivated phase I vaccine and 16 goats were vaccinated with an inactivated phase II Coxiella mixed with Chlamydophila abortus vaccine. Fourteen goats were left unvaccinated. At 84 days of gestation, the goats were subcutaneously challenged with 10(4) bacteria of C. burnetii strain CbC1. Phase I vaccine was effective and dramatically reduced both abortion and excretion of bacteria in the milk, vaginal mucus and feces. In contrast, the phase II vaccine did not affect the course of the disease or excretion.

Prevalence of community-acquired respiratory tract infections associated with Q fever in Japan

A multicenter prospective cohort study to assess the occurrence and characteristics of acute Q fever associated with community acquired respiratory infections was performed. Among the 400 patients enrolled for the study, 10 (2.50%) patients (5 out of 120 cases of pneumonia, 3 out of 131 cases of acute bronchitis, and 2 out of 149 cases of upper respiratory infections) were diagnosed as having acute Q fever. Contact with dogs or cats before the onset of the disease was confirmed in most of the patients. The clinical profiles of these 10 patients were generally similar to those reported from other countries, such as fever, general fatigue and liver dysfunction, except for the predominance of sporadic cases among the urban population. Our study demonstrates that Q fever is not uncommon cause of community-acquired respiratory infections even in Japan.

Q fever in humans and animals in the United States

Coxiella burnetii, the etiologic agent of Q fever, is a worldwide zoonotic pathogen. Although Q fever is present in the United States, little is known about its current incidence or geographic distribution in either humans or animals. Published reports of national disease surveillance, individual cases, outbreak investigations, and serologic surveys were reviewed to better characterize Q fever epidemiology in the United States. In national disease surveillance reports for 1948-1986, 1,396 human cases were reported from almost every state. Among published individual case reports and outbreak investigations, occupational exposures (research facilities, farm environments, slaughterhouses) were commonly reported, and sheep were most frequently implicated as a possible source of infection. In studies conducted on specific groups, livestock handlers had a significantly higher prevalence of antibodies to C. burnetii than did persons with no known risk. Animal studies showed wide variation in seroprevalence, with goats having a significantly higher average seroprevalence (41.6%) than sheep (16.5%) or cattle (3.4%). Evidence of antibody to C. burnetii was reported among various wild-animal species, including coyotes, foxes, rodents, skunks, raccoons, rabbits, deer, and birds. This literature review suggests that C. burnetii is enzootic among ruminants and wild animals throughout much of the United States and that there is widespread human exposure to this pathogen. Sheep and goats appear to be a more important risk for human infection in the United States than cattle or wild animals, and research studies examining the natural history and transmission risk of Q fever in sheep and goats in this country should be encouraged.

Serosurvey of wild rodents for Rickettsioses (spotted fever, murine typhus and Q fever) in Java Island, Indonesia

The prevalence of antibodies against spotted fever group rickettsia (SFGR), murine typhus and Q fever were investigated in wild rats captured in Indonesia. Sera of 327 rats were collected from Jakarta and Boyolali on Java Island. The prevalences of antibodies against SFGR and murine typhus were 128 (39.1%) and 48 (14.7%), respectively. Antibodies against Q fever were not detected in these serum samples. Antibodies against SFGR were found in all species of rats (20.8-51.9%). The antibody positive rate against murine typhus in Rattus norvegicus (38.0%) was significantly higher than that in other rat species (0-4.8%, p<0.01). The antibody positive rates against SFGR and murine typhus in rats captured in Jakarta were significantly higher than those in rats captured in Boyolali (p<0.01). In this survey, all species of rats had antibodies against SFGR, indicating that the 4 species of tested rats (R. norvegicus, R. rattus, R. exulans, R. tiomanicus) were infected with SFGR and that SFGR may infest the whole of Java Island. Most of the rats that were antibody-positive against murine typhus were captured in Jakarta. Therefore, R. norvegicus and R. rattus are likely to be important hosts of murine typhus in Jakarta. The antibody-positive rates against SFGR and murine typhus in rats captured in the dry season were significantly higher than those in rats captured in the rainy season. This may coincide with the active periods of ticks and fleas in Indonesia.