17-07-2025
Fever, Anaemia, or Heart Failure? A Rare Tick Case
A 74-year-old woman presented with fever, chills, fatigue, and shortness of breath 2 weeks after a tick bite of unknown attachment duration. Initial testing for tick-borne illnesses, including Borrelia, Ehrlichia , Anaplasma , and Babesia , was negative. As her condition progressed, she developed haemolytic anaemia. A repeat peripheral blood smear revealed 4.5% parasitaemia, confirming severe babesiosis. Despite treatment with atovaquone and azithromycin, no clinical improvement was observed. Echocardiography alone led to a complete diagnosis.
Marie Yung-Chen Wu, MD, MPH, and colleagues at MetroWest Medical Center in Framingham, Massachusetts, reported the case of a complex parasitic infection.
The Patient and Her History
The patient had a history of asthma and giant cell arteritis and presented to the emergency room with fever, chills, fatigue, exertional dyspnoea, and a nonproductive cough lasting 1 week. She denied experiencing chest pain, palpitations, dysuria, changes in bowel movements, or flank pain. Her family history was significant for liver failure in her father and pancreatic cancer in her mother. She was a former smoker and did not use alcohol or substances other than marijuana. Two weeks before the presentation, she had sustained a tick bite.
Findings and Diagnosis
On admission, she was febrile with a temperature of 39.4 °C, tachycardic with a heart rate of 124 beats/min, hypertensive with a blood pressure level of 151/67 mm Hg, tachypnoeic with a respiratory rate of 22 breaths/min, and had an oxygen saturation of 94% on room air.
Initial laboratory tests showed leucocytosis (16.5 K/μL) with a left shift, normal haemoglobin, and a normal platelet count. Renal function was within normal limits, while liver transaminases were elevated (alanine transferase, 70 U/L; aspartate transaminase, 84 U/L), along with an increased total bilirubin (1.3 mg/dL). Polymerase chain reaction tests for SARS-CoV-2 and influenza A and B were negative.
An elevated D-dimer level (4.85 µg/mL) prompted evaluation for thromboembolism, which was excluded by CT angiography of the chest.
CT also showed no evidence of consolidation or pleural effusions. Testing for tick-borne diseases, including peripheral smears for Ehrlichia , Anaplasma , and Babesia ; Lyme antibodies; and blood cultures, was initially negative.
Empiric doxycycline was initiated to treat potential tick-borne illnesses and atypical respiratory infections.
Despite this, the patient's condition worsened, with persistent fever and worsening shortness of breath. Haemoglobin and platelet counts declined.
Persistently elevated liver enzymes led to an abdominal ultrasound, which revealed nodularity of the liver capsule but no abnormalities in the gallbladder or biliary tract.
A CT scan of the abdomen and pelvis confirmed nodular changes in the liver contour, while magnetic resonance cholangiopancreatography ruled out biliary duct dilation.
Additional testing for HIV, Epstein-Barr virus, cytomegalovirus, fungi, and hepatitis viruses was negative. Doxycycline was discontinued, and empiric broad-spectrum antibiotics with piperacillin/tazobactam were initiated.
Despite treatment, the patient remained febrile and developed progressive anaemia. A haemolysis panel revealed an elevated lactate dehydrogenase level of 658 U/L. A repeat set of thin and thick blood smears for parasites showed 4.5% Babesia parasitaemia. Atovaquone and azithromycin were started, and piperacillin/tazobactam was discontinued. However, her haemolytic anaemia worsened, with haemoglobin levels dropping to 8 g/dL, prompting the need for exchange transfusion.
Laboratory tests showed a markedly elevated pro-B-type natriuretic peptide level of 15,716 ng/mL. Chest x-ray revealed cardiomegaly, engorged pulmonary vasculature, and bilateral pleural effusions, consistent with acutely decompensated heart failure. Echocardiography demonstrated global hypokinesis with an estimated left ventricular ejection fraction between 15% and 20%. Despite prompt diuresis, her respiratory distress progressed, necessitating intubation and mechanical ventilation. She subsequently developed refractory cardiogenic shock, requiring vasopressor support with norepinephrine and inotropic support with dobutamine. Parasitaemia responded well to atovaquone and azithromycin, achieving complete clearance after 5 days. Antimicrobial therapy was continued for an additional 14 days until the patient's symptoms improved.
Discussion
'This case illustrates shortness of breath resulting from stress-induced cardiomyopathy triggered by severe babesiosis, an uncommon and diagnostically challenging presentation. Clinicians should remain alert to rare presentations like this one to enable timely recognition and appropriate management of this potentially life-threatening infection,' the authors wrote.
