Fever and back pain in a herder family
A 43-year-old herder from a rural bag presents to the aimag hospital with 3 weeks of undulant fever, drenching night sweats, fatigue, low back pain and knee pain. He has helped ewes deliver and drinks unpasteurized mare's milk and cow's milk; his wife has similar milder symptoms. He has no cough, no weight loss, and no travel outside the province. Temperature 38.4°C, pulse 88, BP 120/75. Examination shows tenderness over the lumbar spine and both knees without swelling; no rash, no lymphadenopathy, no murmur. WBC 6,800, hemoglobin 118 g/L, ESR 48 mm/h, ALT 45 U/L. Blood culture is unavailable; Brucella agglutination is available. The hospital also has rifampicin, doxycycline, streptomycin and ceftriaxone. The physician must decide about diagnosis, treatment and public health reporting.
1. What is the most likely diagnosis and what tests would you use? How would you interpret a single agglutination titre?
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The combination of herding, lambing, unpasteurized dairy, undulant fever, night sweats and back or joint pain makes brucellosis the leading diagnosis. I would send a serum agglutination test and, if possible, blood cultures, although culture is often negative and is unavailable here. In an endemic setting, a titre of at least 1:160 with a compatible illness is supportive; a lower or single titre does not exclude early disease, so repeat testing in 2 to 4 weeks may be needed. I would also consider tuberculosis of the spine, endocarditis and reactive arthritis, especially if fever persists or a murmur develops. Because he has lumbar tenderness, imaging of the spine is warranted if available. His wife should be assessed and tested as a household contact.
2. What treatment regimen would you start and what would you avoid? Explain the rationale.
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I would start combination therapy to reduce relapse: doxycycline 100 mg orally twice daily for 6 weeks plus rifampicin 600 to 900 mg daily, about 15 mg/kg/day, for 6 weeks. An alternative is doxycycline plus streptomycin 1 g intramuscularly daily for 2 to 3 weeks. I would avoid monotherapy because relapse rates are high. Adherence counselling is essential for a 6-week course. Rifampicin interacts with many drugs, including oral contraceptives and some antiretrovirals, so I would review her medicines. If there is evidence of spondylitis or endocarditis, treatment should be prolonged and specialist input obtained. Doxycycline is avoided in pregnancy and young children, so the wife would need a different regimen if she is pregnant.
3. What public health and communication actions are required?
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Brucellosis is a zoonosis and should be reported to the public health service so the herd and household can be investigated. I would advise the family to stop drinking unpasteurized milk, boil milk before use, use gloves when assisting lambing or calving, and wash hands afterwards. Symptomatic household members should be tested, and the local veterinary service should assess the animals. I would explain that person-to-person transmission is rare, which reduces stigma, but that completing the full course is necessary to prevent relapse and complications. Documentation should include the occupation, animal contact, dairy exposure and reported contacts, because these details guide outbreak response as well as individual care.