Clinical aspects and prevention of Q fever in animals

First Insight into the Prevalence of Coxiella burnetii Infection among Veterinary Medicine Students in Bulgaria

The aim of this study was to assess the prevalence of Coxiella burnetii infection among veterinary medicine students from two Bulgarian Universities, located in Sofia and Stara Zagora. Blood samples were collected from a total of 185 veterinary students for the detection of C. burnetii phase II antibodies and presence of DNA using an enzyme-linked immunosorbent assay (ELISA) and end-point PCR test. Out of all samples, 29.7% were positive for at least one C. burnetii phase II antibody marker or by the result of the PCR test. Veterinary students from Stara Zagora showed a significantly high seropositivity for Q fever (33.6%), as compared to the students in Sofia (23%; p < 0.05). Evidence of recent exposure with detection of anti-C. burnetii phase II IgM (+) antibodies was observed in 14.6% of the students under study. Seroprevalence among students in Stara Zagora was higher (15.3%). Anti-C. burnetii phase II IgG antibodies were detected in 21.6% of examined samples. Our study revealed a higher seropositivity among the male students (32.8%) as compared to females (16.0%; p < 0.05). The end-point PCR assay detected 5.9% blood samples as positive. The relative risk (RR) of Q fever exposure for male students was 40.7%, whereas it was 24.6% in females (p < 0.05). The findings from this study indicate that the C. burnetii infection is widely distributed amongst veterinary students in Bulgaria. This study emphasizes the need for improved safety protocols and infection control measures in veterinary training programs.

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

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

Molecular epidemiology of Coxiella burnetii infection in sheep and goats in Henan province, China

Q fever is a significant zoonotic disease caused by Coxiella burnetii, an obligate intracellular gram-negative bacterium. Although C. burnetii infection has been identified in various animal species, domestic ruminants serve as the primary reservoirs and main sources of human infection. Understanding of the epidemiology of C. burnetii in domestic ruminants is crucial for preventing and controlling of C. burnetii infection in humans. In this study, spleen tissues from sheep and goats were collected in Hennan province, China. Through PCR screening, C. burnetii was detected in sheep and goats in Henan province with an overall infection rate of 6.8 %. Sequence comparison and phylogenetic analysis revealed that all newly identified C. burnetii strains shared a close genetic relationship with those found in humans worldwide. These findings highlight the high risk of C. burnetii infection among slaughterhouse workers and emphasize the importance of epidemiological studies that investigate samples from both humans and animals within the "One Health" framework. Such surveillance will contribute to a better understanding of the epidemic situation and aid in the development of effective prevention and control strategies for C. burnetii infections in humans.

Coxiella burnetii in ticks, livestock, pets and wildlife: A mini-review

Coxiella burnetii is a zoonotic bacterium with an obligatory intracellular lifestyle and has a worldwide distribution. Coxiella burnetii is the causative agent of Q fever in humans and coxiellosis in animals. Since its discovery in 1935, it has been shown to infect a wide range of animal species including mammals, birds, reptiles, and arthropods. Coxiella burnetii infection is of public and veterinary health and economic concern due to its potential for rapid spread and highly infectious nature. Livestock are the primary source of C. burnetii infection in most Q fever outbreaks which occurs mainly through inhalation of contaminated particles. Aside from livestock, many cases of Q fever linked to exposure to wildlife. Changes in the dynamics of human-wildlife interactions may lead to an increased potential risk of interspecies transmission and contribute to the emergence/re-emergence of Q fever. Although C. burnetii transmission is mainly airborne, ticks may act as vectors and play an important role in the natural cycle of transmission of coxiellosis among wild vertebrates and livestock. In this review, we aim to compile available information on vectors, domestic, and wild hosts of C. burnetii, and to highlight their potential role as bacterial reservoirs in the transmission of C. burnetii.

First serological record of Coxiella burnetii infection in the equine population of Slovakia

Coxiella burnetii is a worldwide zoonotic pathogen causing Q fever in various animal species and humans. In Slovakia, cases of C. burnetii infection in both animals and humans are confirmed every year. The role of horses in the epidemiology of this neglected disease is still unclear. In our study, we focused on a serosurvey of C. burnetii in the equine population in Slovakia by the ELISA method. Subsequently, a nested PCR was performed to detect the 16S rRNA fragment of the genus Coxiella. Among 184 horse sera, the presence of specific antibodies to C. burnetii was detected in four samples, representing a 2.17% seropositivity. All the positive horses were mares; two originated from Central Slovakia and two from Eastern Slovakia. Although the number of positive samples was too small for a determination of statistical significance, our results provide the first confirmation of antibodies to C. burnetii in horses from Slovakia. Although no positive PCR result was obtained, these serological findings may help to clarify the circulation of the pathogen in the environment.

The prevalence of Coxiella burnetii in ticks and animals in Slovenia

BACKGROUND

The obligate intracellular bacterium Coxiella burnetii causes globally distributed zoonotic Q fever. Ruminant livestock are common reservoirs of C. burnetii. Coxiella burnetii are shed in large numbers in the waste of infected animals and are transmitted by inhalation of contaminated aerosols. This study was conducted to evaluate the prevalence of C. burnetii infection in domestic animals and ticks in areas of Slovenia associated with a history of Q fever outbreaks.

RESULTS

A total of 701 ticks were collected and identified from vegetation, domestic animals and wild animals. C. burnetii DNA was detected in 17 out of 701 (2.4%) ticks. No C. burnetii DNA was found in male ticks. Ticks that tested positive in the PCR-based assay were most commonly sampled from wild deer (5.09%), followed by ticks collected from domestic animals (1.16%) and ticks collected by flagging vegetation (0.79%). Additionally, 150 animal blood samples were investigated for the presence of C. burnetii-specific antibodies and pathogen DNA. The presence of pathogen DNA was confirmed in 14 out of 150 (9.3%) blood samples, while specific antibodies were detected in sera from 60 out of 150 (40.4%) animals.

CONCLUSIONS

Our results indicate that ticks, although not the primary source of the bacteria, are infected with C. burnetii and may represent a potential source of infection for humans and animals. Ticks collected from animals were most likely found to harbor C. burnetii DNA, and the infection was not lost during molting. The persistence and distribution of pathogens in cattle and sheep indicates that C. burnetii is constantly present in Slovenia.

Serological Evidence of Coxiella burnetii Infection in Cattle and Goats in Bangladesh

We tested 1149 ruminant sera conveniently collected from three districts of Bangladesh to identify the serological evidence of Coxiella burnetii infection in cattle and goats by enzyme-linked immunosorbent assay. We found that 0.7% (8/1149) of ruminants had detectable immunoglobulin G for C. burnetii: 0.65% (4/620) in cattle and 0.76% (4/529) in goats. A sub-set of ruminant samples was retested and confirmed by immunofluorescence assay (18/112). Although we cannot rule out false-positive reactions, our study suggests the presence of C. burnetii in cattle and goats in Bangladesh. Further studies are required to estimate disease burden at the population level and identify risk factors for Q fever in ruminants in Bangladesh.

Does Coxiella burnetii affect reproduction in cattle? A clinical update

Q fever is a zoonosis produced by Coxiella burnetii, a bacterium that is widely distributed worldwide. Domestic ruminants are the most important source of C. burnetii for human infection. In sheep and goats, abortion is the main clinical consequence of infection, yet the symptoms described in cattle have so far been inconsistent. Q fever has been also scarcely reported in cattle, most likely because of its difficult diagnosis at the farm level and because of the many existing responsible C. burnetii strains. In this report, the effects of C. burnetii infection or Q fever disease on the reproductive behaviour of dairy cattle are reviewed, with special emphasis placed on the scarcity of data available and possible control actions discussed.

Simultaneous detection of Chlamydia spp., Coxiella burnetii, and Neospora caninum in abortion material of ruminants by multiplex real-time polymerase chain reaction

Chlamydia spp., Coxiella burnetii, and Neospora caninum are responsible for reproductive diseases and are closely linked with high abortion rates in ruminants. Furthermore, C. burnetii and Chlamydia spp. have zoonotic potential. A real-time polymerase chain reaction (PCR) assay was developed for the simultaneous detection of Chlamydia spp., C. burnetii, and N. caninum. The detection of beta-actin as internal control in the same PCR reaction provides additional information about sample quality by detecting the presence of PCR inhibitors. The multiplex real-time PCR developed in the current study shows a greater sensitivity compared to previously used single-target PCR reactions with a reproducible detection limit of 0.13 plasmid copies per PCR for each target. Additional parallel amplification of all detectable pathogens did not adversely impact sensitivity. This new multiplex PCR allows the highly sensitive, cost-effective, and rapid detection of 3 important pathogens and has the potential to be a useful time-saving tool in the routine diagnosis of abortion cases in ruminants.

Coxiella-like endosymbionts

In the past two decades, many Coxiella-like bacteria have been found in hard ticks and soft ticks as well as in vertebrate hosts. It is interesting to note that many ticks harbor Coxiella-like bacteria with high prevalence. Coxiella-like bacteria and virulent Coxiella burnetii have high homology to each other; they form a monophyletic clade based on 16S rRNA sequence data and subsequent phylogenetic tree analyses. In this chapter, methods of detection, phylogeny, prevalence and density, distribution in tick organs, transmission routes, bacteria-host interactions, and putative functions of the Coxiella-like bacteria are reviewed.

Experimental inoculation of male rats with Coxiella burnetii: successful infection but no transmission to cage mates

Beginning in 2007, the largest human Q fever outbreak ever described occurred in the Netherlands. Dairy goats from intensive farms were identified as the source, amplifying Coxiella burnetii during gestation and shedding large quantities during abortions. It has been postulated that wild rodents are reservoir hosts from which C. burnetii can be transmitted to domestic animals and humans. However, little is known about the infection dynamics of C. burnetii in wild rodents. The aim of this study was to investigate whether brown rats (Rattus norvegicus) can be experimentally infected with C. burnetii and whether transmission to a cage mates occurs. Fourteen male brown rats (wild type) were intratracheally or intranasally inoculated with a Dutch C. burnetii isolate obtained from a goat. At 3 days postinoculation, a contact rat was placed with each inoculated rat. The pairs were monitored using blood samples and rectal and throat swabs for 8 weeks, and after euthanasia the spleens were collected. Rats became infected by both inoculation routes, and detection of C. burnetii DNA in swabs suggests that excretion occurred. However, based on the negative spleens in PCR and the lack of seroconversion, none of the contact animals was considered infected; thus, no transmission was observed. The reproduction ratio R(0) was estimated to be 0 (95% confidence interval = 0 to 0.6), indicating that it is unlikely that rats act as reservoir host of C. burnetii through sustained transmission between male rats. Future research should focus on other transmission routes, such as vertical transmission or bacterial shedding during parturition.

Detection of Coxiella burnetii in complex matrices by using multiplex quantitative PCR during a major Q fever outbreak in The Netherlands

Q fever, caused by Coxiella burnetii, is a zoonosis with a worldwide distribution. A large rural area in the southeast of the Netherlands was heavily affected by Q fever between 2007 and 2009. This initiated the development of a robust and internally controlled multiplex quantitative PCR (qPCR) assay for the detection of C. burnetii DNA in veterinary and environmental matrices on suspected Q fever-affected farms. The qPCR detects three C. burnetii targets (icd, com1, and IS1111) and one Bacillus thuringiensis internal control target (cry1b). Bacillus thuringiensis spores were added to samples to control both DNA extraction and PCR amplification. The performance of the qPCR assay was investigated and showed a high efficiency; a limit of detection of 13.0, 10.6, and 10.4 copies per reaction for the targets icd, com1, and IS1111, respectively; and no cross-reactivity with the nontarget organisms tested. Screening for C. burnetii DNA on 29 suspected Q fever-affected farms during the Q fever epidemic in 2008 showed that swabs from dust-accumulating surfaces contained higher levels of C. burnetii DNA than vaginal swabs from goats or sheep. PCR inhibition by coextracted substances was observed in some environmental samples, and 10- or 100-fold dilutions of samples were sufficient to obtain interpretable signals for both the C. burnetii targets and the internal control. The inclusion of an internal control target and three C. burnetii targets in one multiplex qPCR assay showed that complex veterinary and environmental matrices can be screened reliably for the presence of C. burnetii DNA during an outbreak.

Modelling the effect of heterogeneity of shedding on the within herd Coxiella burnetii spread and identification of key parameters by sensitivity analysis

Coxiella burnetii is the bacterium responsible for Q fever, a worldwide zoonosis. Ruminants, especially cattle, are recognized as the most important source of human infections. Although a great heterogeneity between shedder cows has been described, no previous studies have determined which features such as shedding route and duration or the quantity of bacteria shed have the strongest impact on the environmental contamination and thus on the zoonotic risk. Our objective was to identify key parameters whose variation highly influences C. burnetii spread within a dairy cattle herd, especially those related to the heterogeneity of shedding. To compare the impact of epidemiological parameters on different dynamical aspects of C. burnetii infection, we performed a sensitivity analysis on an original stochastic model describing the bacterium spread and representing the individual variability of the shedding duration, routes and intensity as well as herd demography. This sensitivity analysis consisted of a principal component analysis followed by an ANOVA. Our findings show that the most influential parameters are the probability distribution governing the levels of shedding, especially in vaginal mucus and faeces, the characteristics of the bacterium in the environment (i.e. its survival and the fraction of bacteria shed reaching the environment), and some physiological parameters related to the intermittency of shedding (transition probability from a non-shedding infected state to a shedding state) or to the transition from one type of shedder to another one (transition probability from a seronegative shedding state to a seropositive shedding state). Our study is crucial for the understanding of the dynamics of C. burnetii infection and optimization of control measures. Indeed, as control measures should impact the parameters influencing the bacterium spread most, our model can now be used to assess the effectiveness of different control strategies of Q fever within dairy cattle herds.

Development of a set of multiplex standard polymerase chain reaction assays for the identification of infectious agents from aborted bovine clinical samples

The current study describes the development of a set of 5 multiplex polymerase chain reaction (mPCR) assays for the simultaneous detection of abortive infection agents in bovine fetal tissues, including Brucella spp., Leptospira spp., and Campylobacter fetus (mPCR1); Hammondia heydorni, Neospora caninum, and Toxoplasma gondii (mPCR2); Coxiella burnetii and Chlamydophila psittaci (mPCR3); Mycoplasma bovis, Mycoplasma bovigenitalium, and Ureaplasma diversum (mPCR4); and Bovine viral diarrhea virus (BVDV) and Bovine herpesvirus-1 (BoHV-1; mPCR5). The protocol was tested on different tissue samples collected from 50 aborted bovine fetuses, and it showed that out of the 50 fetuses, 7 (14%, mPCR2) were PCR-positive for N. caninum, 4 (8%, mPCR5) were PCR-positive for BVDV, and 2 (4%, mPCR4) were PCR-positive for U. diversum. The results obtained by using each multiplex PCR were 100% concordant with those obtained by using the respective PCR assays targeting single genes on the same specimens. Moreover, all multiplex PCR assays on clinical samples were compared with reference methods, obtaining a perfect accordance in all samples and confirming the validity of the set of multiplex PCR assays. The proposed set of multiplex PCR assays is, therefore, suitable for the simultaneous detection of the main infectious agents responsible for bovine abortion.

Modelling effectiveness of herd level vaccination against Q fever in dairy cattle

Q fever is a worldwide zoonosis caused by the bacterium Coxiella burnetii. The control of this infection in cattle is crucial: infected ruminants can indeed encounter reproductive disorders and represent the most important source of human infection. In the field, vaccination is currently advised in infected herds but the comparative effectiveness of different vaccination protocols has never been explored: the duration of the vaccination programme and the category of animals to be vaccinated have to be determined. Our objective was to compare, by simulation, the effectiveness over 10 years of three different vaccination strategies in a recently infected dairy cattle herd.A stochastic individual-based epidemic model coupled with a model of herd demography was developed to simulate three temporal outputs (shedder prevalence, environmental bacterial load and number of abortions) and to calculate the extinction rate of the infection. For all strategies, the temporal outputs were predicted to strongly decrease with time at least in the first years of vaccination. However, vaccinating only three years was predicted inadequate to stabilize these dynamic outputs at a low level. Vaccination of both cows and heifers was predicted as being slightly more effective than vaccinating heifers only. Although the simulated extinction rate of the infection was high for both scenarios, the outputs decreased slower when only heifers were vaccinated.Our findings shed new light on vaccination effectiveness related to Q fever. Moreover, the model can be further modified for simulating and assessing various Q fever control strategies such as environmental and hygienic measures.

Growth of Coxiella burnetii in the Ixodes scapularis-derived IDE8 tick cell line

Q fever, a zoonotic disease, is caused by a gram-negative intracellular bacterium, Coxiella burnetii. Although normally transmitted during exposure to infectious aerosols, C. burnetii is also found in arthropod vectors. In the environment, ticks are thought to play a crucial role in bacterial maintenance and transmission by infecting various mammalian species. However, the nature of the pathogen-tick relationship is not well defined. To determine C. burnetii's interactions with a cultured tick cell line, we introduced purified C. burnetii NMII into Ixodes scapularis-derived IDE8 cells and assayed for bacterial presence, replication, gene expression, and subsequent infectivity for mammalian cells. Tick cells were harvested at 24 h, 72 h, 7 days, and 11 days postinfection (PI). C. burnetii uptake and subsequent replication was demonstrated by indirect immunofluorescence assay, electron microscopy, and real-time polymerase chain reaction (PCR). When a genome equivalent multiplicity of infection of 30 was used, 30%-40% of exposed cells were seen to have small, rounded, vacuoles at 72 h PI, whereas at 7 and 11 days PI, 60%-70% of cells contained enlarged vacuoles harboring large numbers of bacteria. Quantitative PCR analysis of total genomic DNA confirmed that C. burnetii genome numbers increased significantly from 24 h to 11 days PI. Expression of C. burnetii type four secretion system homologs at 7 days PI was demonstrated by reverse transcriptase PCR. Finally, indirect immunofluorescence assay demonstrated that C. burnetii propagated within IDE8 cells were infectious for mammalian cells. These studies demonstrate the utility of cultured tick cell lines as a model to investigate C. burnetii's molecular interactions with its arthropod vectors.

Spread of Q fever within dairy cattle herds: key parameters inferred using a Bayesian approach

Q fever is a worldwide zoonosis caused by Coxiella burnetii. Although ruminants are recognized as the most important source of human infection, no previous studies have focused on assessing the characteristics of the bacterial spread within a cattle herd and no epidemic model has been proposed in this context. We assess the key epidemiological parameters from field data in a Bayesian framework that takes into account the available knowledge, missing data and the uncertainty of the observation process owing to the imperfection of diagnostic tests. We propose an original individual-based Markovian model in discrete time describing the evolution of the infection for each animal. Markov chain Monte Carlo methodology is used to estimate parameters of interest from data consisting of individual health states of 217 cows of five chronically infected dairy herds sampled every week for a four-week period. Outputs are the posterior distributions of the probabilities of transition between health states and of the environmental bacterial load. Our findings show that some herds are characterized by a very low infection risk while others have a mild infection risk and a non-negligible intermittent shedding probability. Moreover, the antibody status seems to be a key point in the bacterial spread (shedders with antibodies shed for a longer period of time than shedders without antibodies). In addition to the biological insights, these estimates also provide information for calibrating simulation models to assess control strategies for C. burnetii infection.

Report of a serological study of Coxiella burnetii in domestic animals in Albania

The prevalence of Coxiella burnetii antibodies in domestic ruminants in Albania has been investigated. A total of 1656 serum samples taken from sheep, goats, and cattle housed on farms located in 20 different districts were tested by ELISA for the presence of specific antibodies to C. burnetii phase I and II antigens. Specific IgG antibodies were detected in 9.1% of the animals from both lowland and mountainous areas. In total, a slightly higher percentage of antibodies was detected in sheep and goats (9.8%) than in cattle (7.9%).

Diagnosis of Coxiella burnetii-related abortion in Italian domestic ruminants using single-tube nested PCR

Coxiella burnetii, an obligate intracellular parasite with a worldwide distribution, is the causative agent of acute and chronic Q fever in humans. Although infection is often unapparent in cattle, sheep and goats, there is increasing evidence that C. burnetii infection in these species is associated with abortion and stillbirth. This paper describes the introduction of a single-tube nested PCR protocol for the diagnosis of C. burnetii-related abortion in domestic ruminants in Italy. A total of 514 aborted foetuses from cattle (n = 138) and sheep and goat (n = 376), collected from 301 farms, were analyzed from January 2001 to March 2005. Ninety-seven of 514 (18.9%) animals tested PCR-positive, with 16/138 (11.6%) cattle and 81/376 (21.5%) sheep and goat. Eleven of 102 (10.8%) farms with reproductive disorders in cattle and 37/199 (18.6%) farms with reproductive disorders in sheep and goats were infected with C. burnetii. A greater incidence was observed in three of the seven investigated provinces (p < 0.01), with rates of infected farms of up to 23.8%. Data showed that almost all the C. burnetii-related abortions were recorded between October and April (p < 0.01). These findings suggest that Q fever in humans is largely underestimated in Italy, probably because its occurrence is obscured by flu-like symptoms in acute forms.

[Application of four ELISA techniques (two for IgM and two for IgG) for serological diagnosis of an outbreak of Q fever]

OBJECTIVE

To evaluate four ELISAs (commercialized by Panbio and Serion) for IgM and IgG detection in an outbreak of Q fever.

METHODS

Fifty-three serum samples corresponding to 29 persons were processed. An indirect immunofluorescence assay was used as the reference method.

RESULTS

The sensitivity and specificity for IgM were 100% and 74% (Panbio), and 91% and 88% (Serion). IgG sensitivity was 72% (Panbio) and 89% (Serion). The specificity of both techniques for IgG was 97%.

CONCLUSIONS

Both ELISAs seem to be good IgM screening methods for use during Q fever outbreaks.

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.

Q fever (coxiellosis): epidemiology and pathogenesis

Q fever is a widespread zoonosis caused by the Gram-negative bacterium Coxiella burnetii. Aborting domestic ruminants are the main sources of human infection but the reservoir of infection is extremely wide. In humans, Q fever may occur as acute pneumonia, hepatitis or flu-like illness or may take a severe chronic form, characterized by endocarditis, chronic hepatitis and chronic fatigue syndrome. In animals, the main clinical manifestation is late abortion. Infection with C. burnetii can be diagnosed using cultural, serological and genetic methods but because the organism is potentially dangerous and requires specialized skills only specialist laboratories are capable of undertaking diagnostic tests. This paper provides a brief overview of the epidemiology and pathogenesis of Q fever (coxiellosis).

Occurrence, distribution, and role in abortion of Coxiella burnetii in sheep and goats in Sardinia, Italy

Between 1999 and 2002, 9349 sera and 517 aborted samples (422 foetuses and 95 placenta) were analysed from 675 sheep and 82 goat farms distributed all over the island of Sardinia. After abortion notification, sera collected at random from adult animals were examined to detect antibodies specific to Coxiella burnetii by ELISA, whereas foetuses and placenta were analysed by PCR assay. Specific IgG antibodies were detected in 255 (38%) sheep farms and in 39 (47%) goat herds whereas 40 ovine (10%) and 3 (6%) caprine foetuses were C. burnetii PCR-positive. Although C. burnetii DNA was amplified from different types of tissues, placenta was the tissue with the highest detection rate. Seroprevalence analysis indicates that C. burnetii distribution in sheep and goats is very high, but PCR results demonstrate that C. burnetii has a relatively low role in abortion, especially in goats.

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.

Shedding of Coxiella burnetii in ewes in two pregnancies following an episode of Coxiella abortion in a sheep flock

Coxiella burnetii infection in pregnant sheep typically causes abortion or the birth of weak lambs. Two C. burnetii-related abortions in a group of 34 pregnant ewes were reported at their first lambing in our research institute. The seroprevalence of C. burnetii infection and bacteria shedding were investigated using an ELISA and PCR, respectively, during the course of two subsequent pregnancies. None of the ewes examined seroconverted from negative to positive at the time of the second and the third parturition and most of the ewes that were seropositive at the abortion episode remained positive throughout the investigation. The two successive pregnancies resulted in the birth of healthy lambs without PCR evidence of Coxiella infection from placenta and vaginal swabs taken postpartum. PCR assay performed on vaginal swabs taken from all animals 1, 5 or 12 days after the second lambing were also negative for Coxiella. However, one ewe that had previously experienced C. burnetii shedding at the first lambing excreted the bacteria in the genital tract after the third parturition. The bacteria could not be detected by PCR in milk and faecal samples taken up to 12 days after both parturitions.

Coxiella burnetii infection is associated with placentitis in cases of bovine abortion

A positive score on a modified acid-fast (MAF)-stained smear test of fresh placenta was used to identify a group of bovine abortion submissions believed to be infected with Coxiella burnetii. Immunohistochemical (IHC) testing for Coxiella and Chlamydia antigens was performed on 14 MAF smear-positive cases as well as 29 MAF smear-negative cases received during the study period. Nine MAF smear-positive cases as well as 1 MAF smear-negative case were Coxiella-positive via the IHC test. No placentas were positive for Chlamydia antigen. Various histopathologic features were categorized for all placentas and the presence or absence of selected risk categories was also graded for each case. The results between Coxiella IHC-positive cases and Coxiella IHC-negative/MAF-negative cases were compared using Fisher's exact test (P value at 95% confidence). Significant associations were found between Coxiella IHC-positive cases and the presence of placental inflammation (P = 0.0027), placental necrosis (P = 0.012), fetal pneumonia (P = 0.0152), and the visibility of Coxiella-like organisms within trophoblasts on hematoxylin and eosin-stained sections (P < 0.0001). Histopathologic features of Coxiella IHC-positive placentas included infiltration of the chorionic stroma by mononuclear cells, necrosis of chorionic trophoblasts, and focal exudation of fibrin and neutrophils. The results indicate that MAF smears are a good screening tool for the presence of Coxiella in placentas from bovine abortion cases and that the detection of this pathogen in aborted placentas via traditional staining or IHC methods is usually associated with placentitis.

Range expansion of the tick Amblyomma triguttatum triguttatum, an australian vector of Q fever

The tick Amblyomma triguttatum triguttatum has previously been reported from Western Australia, Queensland and New South Wales. A viable population of this species, including all developmental stages, has now been discovered on the southern end of Yorke Peninsula, South Australia. Species determination was carried out morphologically and using 18S and 16S rRNA. The data for 16S rRNA are the first published for this species. Amblyomma t. triguttatum is significant through its involvement in the natural, Australian cycle of Coxiella burnetti, the pathogen causing Q fever. The environment of Yorke Peninsula contains all of the components required for a natural Q fever cycle and three cases of this disease have been reported from this area since 1995. These findings reinforce the need to put in place effective mechanisms to monitor parasite distributions at a time of large scale global change.

Seroprevalence of coxiellosis in cattle, sheep and people in the east of Turkey

Serum samples collected randomly from 416 cattle in 48 herds, and 411 sheep in 47 flocks, in eight different locations in the east of Turkey between June and December 1998, were examined by indirect fluorescent antibody test (IFAT) to determine the prevalence of Q fever. The age, sex, breed, tick control and abortion history of the animals were also recorded. In addition, 102 serum samples were collected from apparently healthy people who were at risk of contracting the disease, such as farmers, veterinarians, abattoir and laboratory workers, and veterinary students. Seropositivity was observed in 5-8 per cent (24/416) of the cattle in 17 (35-4 per cent) of the herds and in 10-5 per cent (43/411) of the sheep in 21 (44-7 per cent) of the flocks. Eight of the 102 people were seropositive, with the highest prevalence (12-0 per cent) in farmers and abattoir workers. All the seropositive farmers had seropositive animals. None of the laboratory workers or veterinary students was seropositive.

Q fever

Q fever is a zoonosis with a worldwide distribution with the exception of New Zealand. The disease is caused by Coxiella burnetii, a strictly intracellular, gram-negative bacterium. Many species of mammals, birds, and ticks are reservoirs of C. burnetii in nature. C. burnetii infection is most often latent in animals, with persistent shedding of bacteria into the environment. However, in females intermittent high-level shedding occurs at the time of parturition, with millions of bacteria being released per gram of placenta. Humans are usually infected by contaminated aerosols from domestic animals, particularly after contact with parturient females and their birth products. Although often asymptomatic, Q fever may manifest in humans as an acute disease (mainly as a self-limited febrile illness, pneumonia, or hepatitis) or as a chronic disease (mainly endocarditis), especially in patients with previous valvulopathy and to a lesser extent in immunocompromised hosts and in pregnant women. Specific diagnosis of Q fever remains based upon serology. Immunoglobulin M (IgM) and IgG antiphase II antibodies are detected 2 to 3 weeks after infection with C. burnetii, whereas the presence of IgG antiphase I C. burnetii antibodies at titers of >/=1:800 by microimmunofluorescence is indicative of chronic Q fever. The tetracyclines are still considered the mainstay of antibiotic therapy of acute Q fever, whereas antibiotic combinations administered over prolonged periods are necessary to prevent relapses in Q fever endocarditis patients. Although the protective role of Q fever vaccination with whole-cell extracts has been established, the population which should be primarily vaccinated remains to be clearly identified. Vaccination should probably be considered in the population at high risk for Q fever endocarditis.

Prevalence of Coxiella burnetii infection in dairy cattle with reproductive disorders

The prevalence of Coxiella burnetii infection in 207 cattle with reproductive disorders was studied by using an indirect immunofluorescence (IF) test, nested polymerase chain reaction (PCR) and isolation. IF antibodies to phase I and phase II antigens of C. burnetii were found in 122 (58.9%) and 125 (60.4%) of the sera, respectively, and PCR-positives were found in 8 (3.9%) of the sera and in 51 (24.6%) of the milk samples. In addition, C. burnetii was isolated from 51 (24.6%) of the milk samples by inoculating laboratory mice. The results indicate that the IF test plus PCR are useful in the diagnosis of bovine coxiellosis. It is difficult to deny that dairy cattle with reproductive disorders would be one of the important reservoirs of C. burnetii responsible for infection in both animal and human populations in Japan.

Advances in the understanding of Coxiella burnetii infection in Japan

Q fever is a zoonotic disease caused by a rickettsia Coxiella burnetii. Since its first description in 1937, the disease has been found to be present in most countries of the world. Serological evidences of Q fever in humans and coxiellosis in animals were reported in Japan in the 1950s, however, systematic studies of the disease did not begin until the report of isolation of C. burnetii from an acute Q fever patient in 1989. In addition to the extensive information about epidemiology of the disease, the understanding of Japanese isolates of C. burnetii is increasing rapidly in recent years. In this review, the epidemiology of the disease along with some characteristics of isolates of C. burnetii in Japan is summarized in five sections, i.e., coxiellosis, Q fever, modes of spread of the infection, laboratory diagnosis of the infection and some characteristics of Japanese isolates. This review includes some recent, unpublished data from our and other groups.

Q fever (Coxiella burnetii) reservoir in wild brown rat (Rattus norvegicus) populations in the UK

Seroprevalence of Coxiella burnetii, the causal agent of Q fever in humans, was examined in wild brown rat populations from 4 Oxfordshire farmsteads (n = 127), 9 Somerset homesteads (n = 98), and 1 captive enclosure (n = 88) in the UK. Seroprevalence ranged between 7 and 53%, the lowest being within the captive population and the highest on dairy farmsteads with sheep present. This is the first reported investigation of C. burnetii in wild rats outside India. We suggest that the high seroprevalence among rats (i) provides evidence that wild rats constitute an important reservoir for C. burnetii in the UK, and (ii) explains why cats, as frequent predators of rats, are so important in the epidemiology of this disease.

Immunocytochemical demonstration of Coxiella burnetii antigen in the fetal placenta of naturally infected sheep and cattle

Coxiella burnetii antigen was demonstrated immunocytochemically in the placental tissues of aborted fetuses from four cows and two ewes and from one full-term calf. Antigen was observed in cytoplasmic vacuoles of trophoblasts, especially along the base of the chorionic villi. Positive trophoblasts were of normal size or exhibited striking cytoplasmic enlargement. Antigen was also demonstrated in neutrophils, degenerated cells and extracellularly in the intervillous spaces. The chorioallantoic connective tissue, allantoic surface and fetal tissues were devoid of C. burnetii antigen. Ovine placentas showed strong coxiella-specific staining and histological lesions characterized by moderate to severe, multifocal, necrotizing and purulent inflammation. In bovine placentas, the number of immunopositive cells varied from few to moderate and changes were mild or absent. Placental vasculitis consisting of infiltrating mononuclear cells, neutrophils or eosinophils was observed in both of the ovine and two of the bovine fetuses. In addition, a few intravascular thrombi were observed in one ovine and one bovine placenta. Thus the ovine coxiellosis cases were associated with an abundant accumulation of C. burnetii antigen and with severe necrotizing purulent placentitis, whereas in bovine coxiellosis the lesions were mild or absent and the number of organisms demonstrated immunocytochemically was much smaller. These results suggest a relation between species, lesion severity and weight of infection.

Spread and distribution of Coxiella burnetii in C57BL/6J (H-2b) and Balb/cJ (H-2d) mice after intraperitoneal infection

Spread and distribution of Coxiella burnetii were investigated immunocytochemically and antigen dissemination was correlated with light microscopic alterations in Balb/cJ (H-2d) and C57BL/6J (H-2b) mice. Intraperitoneal inoculation of C. burnetii resulted in a self-limiting systemic infection. Gross findings consisted of hepatosplenomegaly and histological lesions were characterized by microabscesses and granulomas in numerous organs including spleen, liver, mesentery, bone marrow, lymph nodes, pancreas, heart and uterus. In addition, splenic lymphoid depletion, venous microthrombi and reduction of bone marrow cells were observed. Coxiella burnetii antigen was demonstrated immunocytochemically in the aforementioned organs, especially in spleen, liver and most of all in the bone marrow. Coxiella antigen was detected in macrophages, macrophage precursor cells, and occasionally endothelial cells. Numerous C. burnetii antigen-positive cells were observed between 5 and 12 days post-infection; thereafter, the amount of C. burnetii antigen decreased rapidly. Immunopositivity was detectable until 30 and 44 days post-infection in the bone marrow of Balb/cJ and C57BL/6J mice, respectively. Severity of histological lesions was associated with presence and clearance of C. burnetii antigen. Specific IgM antibodies were detected 4 days after infection and IgG seroconversion was noticed 7 to 10 days post-infection. Coxiella burnetii-specific IgM and IgG antibodies were still present 150 days after infection. Significant strain-specific differences in the antibody response were not found. The findings demonstrate systemic spread of C. burnetii, especially to bone marrow, spleen and liver, and antigen distribution was closely correlated with the appearance and degree of histological lesions.

Histological and immunocytochemical characterization of Coxiella burnetii-associated lesions in the murine uterus and placenta

The fetoplacental units and the postgravid uterus of BALB/cJ (H-2d) mice inoculated intraperitoneally with Coxiella burnetii (Nine Mile isolate, phase I) on day 6 of pregnancy were examined histologically and immunocytochemically at 1 to 160 days postinoculation. Clinically, abortions, stillbirths, and perinatal deaths were observed. Histological lesions in the placenta were characterized by severe necrosis of the decidua basalis and the labyrinth, fibrinoid degeneration of decidual vessels, and microthrombosis. Pyometra and endometritis at the sites of previous placental attachment, characterized by ulceration, central necrosis, and moderate cellular infiltration consisting of neutrophils and macrophages, were observed postpartum. Pups sacrificed at the age of 9 days exhibited interstitial pneumonia with few granulomas and granulomatous hepatitis and splenitis. Immunocytochemically, antigen-bearing cells were first detected in the decidua 9 days postconception, and single immunopositive cells were detected in the fetal placenta 4 days later. Thereafter, until abortion or parturition, abundant accumulation of C. burnetii antigen was observed in the maternal and fetal compartments of the placenta. Up to 28 days postinoculation, many immunopositive cells were demonstrated at the sites of previous placental attachment, whereas the adjacent endometrium contained only a few antigen-positive cells. C. burnetii antigen was demonstrated in decidual cells, trophoblasts, and macrophages and extracellularly within the sinuses of the labyrinth and in the uterine lumen but not in granulated metrial gland cells. Fetuses in utero and aborted, stillborn, or perinatally dying offspring were immunocytochemically negative for C. burnetii antigen; however, pups killed 9 days after birth showed lesion-associated positive immunoreaction in the lung, liver, and spleen. The present study shows that infection with C. burnetii during pregnancy results in uncontrolled growth of the organism in the murine uteroplacental unit and that associated lesions are characterized by necrosis of placental tissues, fibrinoid degeneration of decidual vessels, and microthrombosis.

Serological evidence that the Q fever agent (Coxiella burnetii) has spread widely among dairy cattle of Japan

Serological examination of bovine and human sera for antibodies against Coxiella burnetti was carried out by the immunofluorescence technique. Twenty to 30% of the cows examined were antibody-positive. Sera from two veterinarians also had antibody against C. burnetii. These results suggest an increase in the number of infected cows with C. burnetii in Japan since 1954, and also imply the possibility of the prevalence of acute Q fever in the human population, which had been underestimated and undiagnosed for the last three decades.