Infectious diseases and tropical medicine for MRCPI Part 1

A 44-year-old man from Ireland presents with 3 weeks of fever, night sweats and weight loss. He keeps sheep on a smallholding and drinks unpasteurised milk. Blood cultures are negative at 5 days. He has sacroiliitis on imaging and a mild transaminitis. Which infection is most likely?

1. Typhoid fever Wrong epidemiology. It follows travel to endemic areas with faecal-oral acquisition, and produces relative bradycardia, rose spots and abdominal symptoms rather than sacroiliitis.
2. Q fever A genuine differential with the same livestock exposure, but it more typically produces pneumonia or hepatitis, and culture-negative endocarditis in the chronic form, rather than sacroiliitis.
3. Brucellosis correct Correct. Undulant fever, night sweats, weight loss, sacroiliitis and hepatic involvement in someone with livestock and unpasteurised dairy exposure is classic brucellosis. Cultures are slow and often negative, so the laboratory must be warned to hold them longer and serology is usually how the diagnosis is made.
4. Lyme disease Wrong exposure and wrong syndrome. Tick-borne, with erythema migrans, and the arthritis is typically a large joint mono- or oligoarthritis.
5. Leptospirosis Associated with rodent urine and freshwater exposure, presenting acutely with conjunctival suffusion, jaundice and renal failure, not with a three-week undulant course and sacroiliitis.

The point: Take an occupational and food history in prolonged fever. Brucella grows slowly, so tell the laboratory what you suspect and warn them about the biohazard risk to staff. Treatment is prolonged combination therapy, typically doxycycline plus rifampicin or an aminoglycoside.

Source: HPSC Ireland — Brucellosis; WHO brucellosis guidance Health Protection Surveillance Centre (Ireland) · tier 1, national regulator or guidance