Rat-Bite Fever in a Guatemalan Child: A Case Report

Background: Rat-bite fever (RBF) is a rare zoonotic illness caused by Streptobacillus moniliformis or Spirillum minus, typically transmitted through rodent bites or environmental exposure. It commonly presents with fever and migratory polyarthritis, often mimicking autoimmune or other infectious conditions, which may lead to diagnostic delay. Case Presentation: We report the case of a 10-year-old male from Guatemala who presented with acute febrile migratory polyarthritis following exposure to rodents, without a clearly witnessed bite. The Initial presentation included progressive joint pain involving the ankles, knees, and wrists, associated with high-grade fever and impaired ambulation. Physical examination revealed joint tenderness, swelling, and functional limitation, predominantly affecting the lower limbs, without cutaneous manifestations. Laboratory evaluation showed elevated inflammatory markers. Blood cultures were negative. The patient was treated with intravenous penicillin G, resulting in rapid clinical improvement, and was subsequently transitioned to oral doxycycline to complete a 14-day antibiotic course. The clinical diagnosis of rat–bite fever was supported by epidemiological exposure, compatible clinical features, and response to therapy. Conclusion: This case underscores the importance of considering rat-bite fever in children presenting with febrile polyarthritis and relevant environmental exposure, particularly in low-resource settings. Early identification and targeted antibiotic therapy can prevent severe complications.