Which organism is the etiologic agent of a hemorrhagic fever disease occurring in the Andes region of South America?

• A. Bartonella bacilliformis
• B. Burkholderia mallei
• C. Haemophilus aegyptius
• D. Yersinia pestis

Answer: (A)

In this scenario, the organism responsible for a hemorrhagic fever in the Andes is Bartonella bacilliformis, the cause of Carrión’s disease. This pathogen is transmitted by sandflies in the Andean highlands and produces two forms: an acute phase called Oroya fever, with fever and severe hemolytic anemia caused by bacteremia of erythrocytes, and a later cutaneous phase known as verruga peruana, with characteristic vascular skin lesions. The bacterium is a Gram-negative, intracellular organism that invades red blood cells and endothelial cells, making diagnosis possible by blood smears or skin lesion biopsy. The other organisms listed cause different diseases or occur in different regions (for example, Burkholderia mallei causes glanders, Haemophilus aegyptius is linked to Brazilian purpuric fever, and Yersinia pestis causes plague), so they do not fit the Andes hemorrhagic fever scenario.