New criteria for immunofluorescence assay for Q fever diagnosis in Japan

High prevalence of Coxiella burnetii infection in humans and livestock in Assiut, Egypt: A serological and molecular survey

BACKGROUND AND AIM

Q fever is considered a neglected zoonotic disease and is caused by Coxiella burnetii. Very little information is available on C. burnetii infections in cattle, sheep, and goat populations in Egypt. The aim of this study was to identify the seroprevalence of C. burnetii in humans and livestock and to test for the presence of C. burnetii DNA in sera from seropositive animals and humans.

MATERIALS AND METHODS

Blood samples were collected from 160 apparently healthy farm animals and 120 patients from three hospitals of the Assiut Governorate throughout 2017/2018. These populations were tested for antibodies against C. burnetii phase II antigen by immunofluorescence assay [IFA] and enzyme-linked immunosorbent assay (ELISA). Seropositive samples were subjected to real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

The results of the IFA revealed C. burnetii seroprevalence rates of 45.3%, 56.0%, 45.7%, and 53.3% in cattle, sheep, goats, and humans, respectively. In humans, the seroprevalence rates were 52.1%, 30.4%, 37.5%, 74.1%, and 62.5% in patients with fever of unknown origin, influenza, kidney dialysis, hepatitis C virus, and hepatitis B virus, respectively. Likewise, by ELISA, the seroprevalence in bovine was 50.7%; sheep, 60.0%; goats, 51.4%; and humans, 55.0% (54.3%, 30.4%, 37.5%, 77.8%, and 62.5% in patients with fever of unknown origin, influenza, kidney dialysis, hepatitis C virus, and hepatitis B virus, respectively). RT-qPCR targeting the repetitive element IS1111 confirmed the presence of C. burnetii DNA.

CONCLUSION

These results proved that apparently healthy cattle, sheep, and goats may be very important reservoirs of C. burnetii infection. In light of these data, the effect of Q fever on the replication of hepatitis virus remains unclear. Although hepatitis is one of the main aspects of acute Q fever, the influence of hepatitis on Q fever remains to be investigated. Q fever is not a reportable disease in Egypt, and clinical cases may rarely be recognized by the health-care system. Additional information on the epidemiology of C. burnetii in Egypt is warranted, including other associated problems such as the distribution of infections, pathologic hallmarks, and molecular typing.

Detection of Coxiella burnetii Using Silicon Microring Resonator in Patient Blood Plasma

Blood plasma from patients is a powerful resource for diagnosing infectious disease due to it having many genetic materials as well as being relatively easy to obtain. Thus, various biosensors have been investigated for diagnosing diseases in blood plasma. However, there are no optimized and validated sensors for clinical use due to the low sensitivity, complexity, and difficulties of removing the inhibitors from plasma samples. In this study, we described a silicon microring resonator sensor used to detect Coxiella burnetii from the blood plasma of Q-fever patients in a label-free, real-time manner. Q-fever is an infectious disease caused by Coxiella burnetii via direct contact or inhalation aerosols. We validated this biosensor in the blood plasma of 35 clinical samples (including 16 Q fever samples infected with Coxiella burnetii and 19 samples infected with other febrile diseases. The biosensors are capable of rapid (10 min), highly sensitive (87.5%), and specific (89.5%) detection in plasma samples compared to the use of the conventional method.

Rapid and Visual Detection of Coxiella burnetii Using Recombinase Polymerase Amplification Combined with Lateral Flow Strips

Coxiella burnetii, a global-distributed biological warfare agent, is the causative agent of Q fever. Correct diagnosis of Q fever is challenging and developing a fast, simple, and reliable detection method is necessary. In this study, recombinase polymerase amplification (RPA) assay combined with lateral flow (LF) test was developed targeting 23S rRNA gene of C. burnetii Xinqiao strain. Primers and probe were designed and synthesized, with one set with high amplification efficiency screened for establishment of the method. Reaction conditions were optimized. Sensitivity, specificity, and accuracy were evaluated. The established RPA-LF reaction could be completed in 30 minutes by combining RPA at 37°C with LF at room temperature, with visually judged results. The method showed good specificity without recognizing other bacteria evaluated. It detected positive plasmid and genomic DNA at levels of 10 copies/reaction and 7 copies/reaction, respectively, levels comparable to that of real-time quantitative PCR (RT-qPCR) targeting 23S rRNA gene established previously. Both RPA-LF and RT-qPCR were used to detect C. burnetii-infected mouse samples and the results were fully consistent. The method showed superior detection performance and will provide technical support against C. burnetii in resources-limited areas.

Seroreactivity to Q Fever Among Slaughterhouse Workers in South Korea

Objectives

Q fever is a zoonotic disease that occurs worldwide; however, little is known about its prevalence in South Korea. We attempted to determine the prevalence of Q fever seroreactivity among Korean slaughterhouse workers and the risk factors for seroreactivity according to the type of work.

Methods

The study was conducted among 1503 workers at a total of 73 slaughterhouses and 62 residual-product disposal plants. During the study period, sites were visited and surveys were administered to employees involved in slaughterhouse work, and serological tests were performed on blood samples by indirect immunofluorescence assays. Serological samples were grouped by job classification into those of slaughter workers, residual-product handlers, inspectors and inspection assistants, and grading testers and testing assistants. Employee risk factors were analyzed according to the type of work.

Results

Out of 1481 study subjects who provided a blood sample, 151 (10.2%) showed reactive antibodies. When these results were analyzed in accordance with the type of work, the result of slaughter workers (11.3%) was similar to the result of residual-product handlers (11.4%), and the result of inspectors and assistants (5.3%) was similar to the result of grading testers and assistants (5.4%). Among those who answered in the affirmative to the survey question, “Has there been frequent contact between cattle blood and your mouth while working?” the proportions were 13.4 and 4.6%, respectively, and this was identified as a risk factor that significantly varied between job categories among slaughterhouse workers.

Conclusions

This study found a Q fever seroreactivity rate of 10.2% for slaughterhouse workers, who are known to be a high-risk population. Contact with cattle blood around the mouth while working was the differential risk factor between job categories among slaughterhouse workers.

Prevalence of Antibodies Against Coxiella burnetii in Korean Native Cattle, Dairy Cattle, and Dogs in South Korea

Coxiella burnetii is a zoonotic agent and causes coxiellosis, which is a cause of reproductive failure in a range of animal species, including abortion and stillbirth and Q fever, which is most often characterized by an acute flu-like illness, mild pneumonia, and/or hepatitis in humans. While livestock are well recognized worldwide as a source of infection, the zoonotic risk of C. burnetii infection in companion animals such as dogs may be overlooked. For serological diagnosis, indirect immunofluorescent assay (IFA) and enzyme-linked immunosorbent assay (ELISA) are generally considered good methods for prevalence surveys of coxiellosis. In this study, we conducted a nationwide survey of the seroprevalence of previous exposure to C. burnetii in dogs, dairy cattle, and Korean native cattle (a primarily beef breed) in South Korea. Serum samples obtained from 3087 Korean native cattle, 1224 dairy cattle, and 1023 dogs were collected from eight provinces in South Korea, and IFA and ELISA were performed to test for seropositivity. The prevalence of C. burnetii was 1.7% in Korean native cattle, 10.5% in dairy cattle, and 2.9% in dogs. This is the first report identifying previous exposure to C. burnetii in South Korean dogs. Furthermore, the presence of C. burnetii antibodies in companion and feral dogs indicates that dogs can be a potential reservoir species for zoonotic risk of C. burnetii infection in South Korea. Therefore, more detailed studies aiming to clarify epidemiological factors should be performed in the future.

Detection of Q Fever Specific Antibodies Using Recombinant Antigen in ELISA with Peroxidase Based Signal Amplification

Currently, the accepted method for Q fever serodiagnosis is indirect immunofluorescent antibody assay (IFA) using the whole cell antigen. In this study, we prepared the recombinant antigen of the 27-kDa outer membrane protein (Com1) which has been shown to be recognized by Q fever patient sera. The performance of recombinant Com1 was evaluated in ELISA by IFA confirmed serum samples. Due to the low titers of IgG and IgM in Q fever patients, the standard ELISA signals were further amplified by using biotinylated anti-human IgG or IgM plus streptavidin-HRP polymer. The modified ELISA can detect 88% (29 out of 33) of Q fever patient sera collected from Marines deployed to Iraq. Less than 5% (5 out of 156) of the sera from patients with other febrile diseases reacted with the Com1. These results suggest that the modified ELISA using Com1 may have the potential to improve the detection of Q fever specific antibodies.

Epidemic Q fever in humans in the Netherlands

In 2005, Q fever was diagnosed on two dairy goat farms and 2 years later it emerged in the human population in the south of the Netherlands. From 2007 to 2010, more than 4,000 human cases were notified with an annual seasonal peak. The outbreaks in humans were mainly restricted to the south of the country in an area with intensive dairy goat farming. In the most affected areas, up to 15% of the population may have been infected. The epidemic resulted in a serious burden of disease, with a hospitalisation rate of 20% of notified cases and is expected to result in more cases of chronic Q fever among risk groups in the coming years. The most important risk factor for human Q fever is living close (<5 km) to an infected dairy goat farm. Occupational exposure plays a much smaller role. In 2009 several veterinary control measures were implemented including mandatory vaccination of dairy goats and dairy sheep, improved hygiene measures, and culling of pregnant animals on infected farms. The introduction of these drastic veterinary measures has probably ended the Q fever outbreak, for which the Netherlands was ill-prepared.

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.

The application of an enzyme-linked immunosorbent assay or an immunofluorescent assay test leads to different estimates of seroprevalence of Coxiella burnetii in the population

The diagnosis and epidemiological studies of Q fever depend on serology. Among the main methods employed are the enzyme-linked immunosorbent assay (ELISA) and the immunofluorescent assay test (IFAT). We show that two commercial assays representing the two methods with two different cut-off titres can lead to significant differences in diagnostic and seroprevalence estimates. This in turn emphasizes the need for a standardized gold method to compare the various assays; whether this standard is 'in-house' or commercially obtained.

Q fever in Japan: an update review

As neglected zoonosis for many years, Q fever is now ubiquitous in Japan. Similarly to elsewhere in the world, domestic animals are considered to be important reservoirs of the causal agent, Coxiella burnetii, a resistant intracellular bacterium. Infected animals shed bacteria in milk, feces, urine, vaginal mucous and birth products. Inhalation of bacteria present in the environment is the main route of animal and human infection. Shedding of C. burnetii in milk by domestic ruminants has a very limited impact as raw milk is seldom ingested by the Japanese population. The clinical expression of Q fever in Japan is similar to its clinical expression elsewhere. However clinical cases in children are more frequently reported in this country. Moreover, C. burnetii is specified as one of the causative organisms of atypical pneumonia in the Japanese Respiratory Society Guideline for the management of community-acquired pneumonia. In Japan, C. burnetii isolates are associated with acute illness and are mainly of moderate to low virulence. Cats are considered a significant source of C. burnetii responsible for human outbreaks in association with the presence of infected parturient cats. Since its recognition as a reportable disease in 1999, 7-46 clinical cases of Q fever have been reported by year. The epidemiology of Q fever in Japan remains to be elucidated and the exact modes of transmission are still unproven. Important further research is necessary to improve knowledge of the disease itself, the endogenous hosts and reservoirs, and the epidemiological cycle of coxiellosis in Japan.

Comparison of PCR, immunofluorescence assay, and pathogen isolation for diagnosis of q fever in humans with spontaneous abortions

Coxiella burnetii, an obligate intracellular parasite with a worldwide distribution, is the causative agent of Q fever in humans. We tested a total of 368 samples (placental bits, genital swabs, fecal swabs, and urine and serum samples) collected from women (n = 74) with spontaneous abortions for C. burnetii by a PCR assay targeting IS1111, the repetitive transposon-like region of C. burnetii (trans-PCR); real-time PCR; an indirect immunofluorescence assay (IFA); and the isolation of the pathogen. The IFA showed seropositivity for 25.68% of the women with spontaneous abortions, whereas trans-PCR and real-time PCR each detected the pathogen in 21.62% of cases. Overall, 25.68% of the subjects were positive by one or more assays. Real-time PCR showed a slightly higher level of sensitivity than trans-PCR. With the IFA as the reference, the two PCR assays showed a higher level of sensitivity (84.21%) than pathogen isolation (26.31%), while both the PCR assays and pathogen isolation were specific (100%). The detection of high numbers of C. burnetii cells in clinical samples and the frequent association of the pathogen with cases of spontaneous abortions observed in this study revealed that Q fever remains underdiagnosed and that the prevalence in India is underestimated.