Q Fever



Q Fever


Dima Youssef

James W. Myers



INTRODUCTION



  • Coxiella burnetii is a gram-negative intracellular, pleomorphic coccobacillus that undergoes phase variation. This variation is associated with changes in the lipopoly-saccharide of the outer membrane.


  • The virulent phase I exists in nature, but the avirulent phase II form is found following repeated passage of phase I bacteria in embryonated chicken eggs.


  • C. burnetii can be found in arthropods (ticks) rodents, birds, and fish.


  • The infected ticks can transmit it to sheep, goats, and cattle.


  • Acute Q fever, which develops after an incubation period of a few weeks, is usually characterized by a nonspecific febrile illness, pneumonitis, or hepatitis. On the other hand, chronic Q fever may present months to years after initial infection, usually manifesting as culture-negative endocarditis.


EPIDEMIOLOGY


Sources of Human Infection



  • Milk



    • The pasteurization process of commercial milk may reduce transmission of C. burnetii from cattle to humans.


  • Placental products


  • Dried feces in inhaled dust


  • Not by tick exposure


  • Occupational risk



    • Hunters


    • Farmers


    • Abattoir workers


    • Veterinarians


    • US military personnel recently deployed to Iraq and Afghanistan


  • France and Australia cases outnumber those from the USA.


CLINICAL MANIFESTATIONS



  • The incubation period is usually about 4 weeks. Many patients appear to be asymptomatically infected.


  • A self-limited, flu-like illness appears to be the most common infection.


  • A “chronic fatigue” syndrome has been reported in patients after infection with acute Q fever. This may have a genetic predisposition.


  • Pulmonary



    • May present as an atypical pneumonia, often with fever, pleurisy, myalgias, diarrhea, and a severe headache



    • Cough is nonproductive and may be absent despite the presence of pneumonia.


    • Usually, Coxiella pneumonia is of mild-to-moderate severity, but it can be rapidly progressive and cause respiratory failure.


    • Multiple rounded opacities may be seen.


    • Pleural effusions in 1/3 of patients


    • Hilar lymphadenopathy


    • Thirty days is the average resolution time for the radiographs.


    • If an lumbar puncture (LP) is performed for the headache, it is usually normal at this time.


  • Liver



    • “Doughnut granulomas” on liver biopsy in patients with an fever of unknown origin (FUO)


    • Q fever hepatitis



      • Fever, abdominal pain, anorexia, nausea, vomiting, and diarrhea


      • Alkaline phosphatase, AST, and ALT levels are usually elevated to two to three times the normal level.


      • Autoantibodies are often present.


  • Central nervous involvement



    • Meningoencephalitis occurs in 1% of cases.


    • Lumbar puncture will primarily show mononuclear cells, elevated protein, and normal glucose.


    • Patients with CNS involvement do not demonstrate differences in predisposing conditions but more frequently have occupational exposure to goats than patients with acute Q fever but no neurologic involvement.


    • Headache is the most common symptom, but Q fever can manifest in a variety of neurologic syndromes including aseptic meningitis and radiculitis.


  • Pregnancy



    • Obstetric complications, such as spontaneous abortion, intrauterine growth retardation, intrauterine fetal death, and premature delivery, occur.


    • Pregnant women are at risk of developing of chronic Q fever.


    • A review suggested that the outcome was found to depend on the trimester.



      • Abortions occurred in 7 of 7 insufficiently treated patients infected during the first trimester as opposed to 1 of 5 patients infected later.


      • Co-trimoxazole given until delivery protected against abortion (0/4) but not against the development of chronic infections and did not significantly reduce the colonization of the placenta (2/4 vs. 4/4) in one study.


      • Endocarditis was not observed among any of the patients who received long-term co-trimoxazole therapy in another study.


  • Heart



    • Myocarditis



      • One percent of Q fever cases


      • T-wave changes


      • Tachycardia, respiratory failure, and cardiac failure


      • May lead to death of the patient


      • Diagnosis by serology to phase II antigen, culture, and biopsy


    • Pericarditis



      • One percent of cases


      • Often associated with endocarditis or myocarditis


      • Effusions and T-wave changes are noted.


      • Chest pain



  • Endocarditis



    • One of the causes of “culture-negative” endocarditis


    • Seventy percent of all chronic Q fever cases


    • More common in Europe than in the United States


    • Abnormal native valves (congenital, rheumatic, degenerative, or syphilitic)


    • Prosthetic valves can also be infected.


    • Mostly males


    • Age >40



      • Immunosuppression is a risk factor.



        • Organ transplant recipients


        • Cancer


        • Lymphoma


        • Rare in HIV patients


    • Symptoms are often related to heart failure.


    • Fever, often low-grade or remittent


    • Weight loss, chills, anorexia, and night sweats


    • Malaise


    • Hepatosplenomegaly


    • Marked clubbing


    • Purpuric rash


    • Embolic phenomena in 20%


    • Immune complex glomerulonephritis and microscopic hematuria


    • LVH on EKG can be seen.


    • Elevated erythrocyte sedimentation rate


    • Polyclonal increase in IgG, IgM, and IgA levels


    • Anemia and thrombocytopenia are often seen.


    • Most patients present with abnormal LFTs.


    • Lactate dehydrogenase and creatine phosphokinase levels may be abnormal.


    • Rheumatoid factor, circulating immune complexes, and cryoglobulin abnormalities can be found.


    • Anti—smooth muscle antibodies, circulating anticoagulant antibodies, antimito-chondrial antibodies, antinuclear antibodies, and a positive Coombs test have also been reported.


    • Histologically, one may see significant fibrosis and calcifications, slight inflammation and vascularization, and small or absent vegetations.



      • These pathologic features might be confused with noninfectious valvular degenerative damage.


      • These histologic features are very similar to that observed with other blood culture —negative types of endocarditis, such as bartonellosis and Whipple disease. Meaning that the histologic features of Q fever endocarditis may be confused with degenerative damage.


  • Usually, Q fever endocarditis is diagnosed serologically.



    • High levels of anti—phase I antibodies are found in chronic Q fever, whereas anti—phase II antibodies predominate during acute Q fever.


    • Note that the diagnosis of Q fever endocarditis can also be made by other means including C. burnetii isolation in cell culture, polymerase chain reaction (PCR), or immunohistochemical examination.


    • Patients should be serologically monitored for at least 5 years because of the risk of relapse.



  • Vascular infections



    • Aortic aneurysms


    • Vascular grafts


    • Mortality (25%)


    • Surgery helpful

Jun 22, 2016 | Posted by in INFECTIOUS DISEASE | Comments Off on Q Fever

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