Q fever is a rare infectious disease transmitted through the inhalation or ingestion of the bacteria Coxiella burnetii. Cattle, sheep, and goats frequently serve as bacterial hosts for this microorganism. C. burnetii is mostly transmitted through inhalation of contaminated air or ingestion of contaminated food and beverages. Agricultural laborers, particularly those engaged with livestock, individuals employed in abattoirs, and veterinarians are particularly susceptible to this disease. Alternative modes of transmission are infrequent but encompass tick bites and human-to-human transmission. Q fever impacts individuals of all ages, with most cases occurring in those between 30 and 70 years old.
Classification and symptoms
| Classification Level | Disorder |
| Prevalence | NA |
| Age of Onset | All ages |
| Inheritance | NA |
Image I: Modes of Transmission of Q Fever; Image II: Mechanism involved in Q Fever and cellular effector responses to bacteria C. burnetii
Approximately 60% of cases exhibit no symptoms. Q fever manifests with a wide spectrum of symptoms, ranging from acute (typically self-limiting) infections to potentially lethal chronic infections. Q fever impacts individuals of all ages, with most cases occurring in those between 30 and 70 years old. The incubation phase lasts 2 to 3 weeks. The predominant symptoms of acute Q fever include elevated temperature, intense headache, muscle pain, chills, and cough. It may also be linked to pneumonia or hepatitis. Pneumopathy is generally modest; nonetheless, pleural effusion or acute respiratory distress may arise. Children frequently experience gastrointestinal symptoms and skin rashes, affecting up to 50% of those diagnosed. The infection may progress to a chronic form in less than 5% of instances among those with predispositions, such as heart valve or vascular defects, months or years following the initial infection. Chronic symptoms including endocarditis, vascular infections, and osteomyelitis, or, less frequently, fever with hepatitis progressing to hepatic fibrosis or cirrhosis. A primary infection during pregnancy may result in spontaneous abortion, preterm, low birth weight, fetal infection, or recurrent miscarriages. Chronic Q fever following delivery may be linked to heart involvement.
Diagnosis and treatment
The management of chronic Q fever is intricate and contingent upon the specific symptoms exhibited by the individual. Individuals of all ages are vulnerable to Q fever. The diagnosis of acute Q fever is validated by serological evidence of a fourfold increase in phase II immunoglobulin (Ig) G using an immunofluorescent assay conducted on paired samples collected 3-6 weeks apart. Diagnosis of chronic Q fever relies on an elevated phase 1 IgG titer (generally ≥1:1024) and the presence of a discernible nidus of infection (such as endocarditis, vascular infection, osteomyelitis, or chronic hepatitis). Liver enzyme levels are frequently elevated. PCR testing of blood or serum may be beneficial within the initial two weeks of symptom onset and prior to the prescription of antibiotics. The differential diagnosis includes any illness presenting with fever and additional constitutional symptoms, including Brucellosis and influenza. Prophylactic techniques rely on immunization (in Australia) and suitable hygiene practices. Compliance with conventional precautions during patient care mitigates transmission. Patients exhibiting symptoms of acute Q fever should receive doxycycline treatment for a duration of two weeks. A pregnancy test must be conducted prior to initiating treatment in women of reproductive age. Children under 8 with minor sickness, pregnant women, and anyone allergic to doxycycline may be treated with trimethoprim-sulfamethoxazole. Chronic Q fever is managed with a regimen of doxycycline and hydroxychloroquine for no less than 18months.
The worldwide implementation of the current preventative human Q fever vaccine, Q-VAX, is restricted by reactogenic responses in pre-sensitized individuals. However, there has been limited success in the development of a universal Q fever vaccine, despite the implementation of numerous strategies. The mechanisms of the underlying reactogenic responses are only partially understood and are significant factors in the development of a safe Q fever vaccine. The United States does not have access to Q fever vaccines.
By averting contact with animals, particularly those that are in the process of giving birth, you can lower your risk of contracting Q fever. C. burnetii, the bacterium that induces Q fever, is a potential bioterrorism agent.
In spite of this advancement, a significant impediment to the development of enhanced Q fever vaccines is the absence of an understanding of the antigenic determinants of C. burnetii and the protective correlates of Q fever vaccination. Consequently, a comprehension of the bacterial determinants of immunity and the subsequent host immune responses will be of immense value in the ongoing development of vaccine strategies. Meanwhile, click here to read about Q fever.One can find out more about available support on CDC, WHO.
Dr. Malini Gupta, Ph.D.
Sources
- https://www.cdc.gov/q-fever/data-research/index.html
- Figure derived from: https://qfeveraustralia.com.au/q-fever-faqs/
- Figure derived from: https://www.nature.com/articles/s41541-023-00727-6
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