A 65-year-old man comes to the emergency department due to fevers and malaise for the last 48 hours. The patient initially experienced fevers and chills, which subsequently progressed to fatigue to the point that he had difficulty performing routine tasks this morning. He has also had a mild headache. The patient lives in eastern Massachusetts with his wife. He is retired and spends time gardening and swimming at a local public pool. The patient traveled to Thailand 2 years ago with his family and to Florida 2 months ago. Temperature is 38.9 C (102 F), blood pressure is 122/70 mm Hg, and pulse is 114/min and regular. The oropharynx is dry and has no lesions. Lung examination demonstrates coarse crackles bilaterally. The abdomen is soft and mildly tender throughout with palpable splenomegaly. He has no rash or open wounds. Peripheral blood smear is shown in the exhibit.

Which of the following is the most likely source of this patient's infection?

Question

A 65-year-old man comes to the emergency department due to fevers and malaise for the last 48 hours.  The patient initially experienced fevers and chills, which subsequently progressed to fatigue to the point that he had difficulty performing routine tasks this morning.  He has also had a mild headache.  The patient lives in eastern Massachusetts with his wife.  He is retired and spends time gardening and swimming at a local public pool.  The patient traveled to Thailand 2 years ago with his family and to Florida 2 months ago.  Temperature is 38.9 C (102 F), blood pressure is 122/70 mm Hg, and pulse is 114/min and regular.  The oropharynx is dry and has no lesions.  Lung examination demonstrates coarse crackles bilaterally.  The abdomen is soft and mildly tender throughout with palpable splenomegaly.  He has no rash or open wounds.  Peripheral blood smear is shown in the exhibit.
  
Which of the following is the most likely source of this patient's infection?

Quizplus · Accepted Answer

11ec160b_3810_d01a_9249_81c78334802a_MD0001_00 This patient with an acute febrile illness has a peripheral blood smear showing intraerythrocytic ring inclusions. Parasites that can potentially cause disease in red blood cells include Plasmodium (malaria) and Babesia (babesiosis). In this patient, the epidemiology (residence in northeastern United States, outdoor exposure in the summer) is suggestive of babesiosis. This organism is transmitted by the Ixodes scapularis tick, which is also a vector for Borrelia burgdorferi (Lyme disease) and Anaplasma (human granulocytic anaplasmosis). (Choice A) Aedes is the vector for dengue and chikungunya, which have been diagnosed in Florida but have different presentations (eg, rash, arthralgias) and a short incubation period (<14 days). Malaria is transmitted by Anopheles and is endemic in Thailand. Although it can also cause intraerythrocytic ring inclusions, it has a typical incubation period of weeks; this patient visited Thailand 2 years ago. (Choice B) Brown recluse spider bites can cause fever and malaise and, less commonly, anemia; however, they would not be associated with intraerythrocytic organisms. (Choice C) Dog bites can be associated with a variety of organisms causing soft tissue infection, including Pasteurella, streptococci, and staphylococci. (Choice D) Freshwater consumption can be associated with intraintestinal bacterial and parasitic infections such as cryptosporidiosis and giardiasis. However, these infections typically cause gastrointestinal illnesses. (Choice F) Exposure to plants and soil can be associated with bacterial infections, including Nocardia and fungal infections such as sporotrichosis. These most commonly present as soft tissue infections; systemic infections are rare in immunocompetent patients. (Choice G) Fungal spore inhalation can lead to pulmonary infections, including histoplasmosis and blastomycosis. These organisms are not endemic to the northeastern United States and are not associated with intraerythrocytic organisms. Educational objective: Babesiosis should be considered in patients with febrile illness who reside in geographic areas with Ixodes ticks. The diagnosis can be established with identification of intraerythrocytic organisms on peripheral blood smear. __________ References: Babesiosis. (http://www.ncbi.nlm.nih.gov/pubmed/25999229)

A 65-Year-Old Man Comes to the Emergency Department Due to Fevers