S5178 Atypical Giardiasis in a Returning Traveler: Diagnostic Challenges and Clinical Implications

Introduction: Gastrointestinal symptoms are the most common travel-related illness, affecting approximately 40% of travelers from high-income countries visiting resource-limited regions. Giardia duodenalis is the most frequently diagnosed intestinal protozoan worldwide, with prevalence ranging from 2% in developed nations to 70% in endemic areas. Although many cases are mild or self-limited, giardiasis often causes malabsorption with symptoms including abdominal pain, bloating, and its hallmark-watery diarrhea. We present an atypical case of travel-associated giardiasis without diarrhea, underscoring the value of detailed travel history and diagnostic vigilance. Case Description/Methods: A 61-year-old man with diabetes, hypertension, and Barrett’s esophagus presented one day after returning from Mexico with fever, fatigue, bloating, abdominal pain, and night sweats. Initially diagnosed by his primary physician with viral gastroenteritis, his symptoms persisted and he experienced a 16-pound weight loss over 4 weeks - without diarrhea. Laboratory evaluation was unremarkable except for C-reactive protein 7.8 mg/L; no stool ova and parasite (OandP) testing was performed. Abdominal computed tomography (CT) revealed mildly prominent mesenteric lymphadenopathy and misty mesentery, raising concern for malignancy and prompting referrals to gastroenterology and hematology. The patient was subsequently seen in our internal medicine continuity clinic, where a detailed history revealed recent freshwater exposure in a cenote in Mexico, including accidental ingestion. Stool OandP confirmed Giardia duodenalis. Treatment with a single dose of tinidazole led to complete resolution of symptoms. Discussion: Although watery diarrhea is commonly considered the hallmark of giardiasis, up to 50% of cases may present atypically. In this patient, absence of diarrhea and nonspecific imaging findings contributed to diagnostic delay and unnecessary subspecialty referrals. Recognition of a relevant travel history - particularly freshwater exposure - would have supported early stool OandP testing. Clinicians should maintain a high index of suspicion for giardiasis and other travel related infections in patients with persistent gastrointestinal symptoms and travel history, even in the absence of classic features. Early stool testing remains a low-cost, low-risk, and high-yield diagnostic tool.