What could be causing anemia in a family living in a rural area with well water and multiple cats, despite having a healthy diet and no symptoms of gastrointestinal disease?

Hookworm Infection from Well Water is the Most Likely Cause

Given the rural setting with well water exposure, multiple cats, healthy diet, absence of GI symptoms, and chronic anemia affecting an entire unrelated family, hookworm infection is the most probable diagnosis and should be investigated immediately. 1

Primary Differential Diagnosis

Hookworm Infection (Most Likely)

• Hookworm is specifically listed as an uncommon but important cause of iron deficiency anemia in the British Society of Gastroenterology guidelines, particularly relevant in settings with well water exposure 1
• Hookworm-related blood loss occurs in the upper gastrointestinal tract and causes chronic occult bleeding without diarrhea or abdominal symptoms 2
• The linear relationship between hookworm infection intensity and intestinal blood loss makes this a highly plausible cause of family-wide anemia 2
• Well water contamination is a known transmission route for hookworm larvae, which penetrate skin or are ingested 2
• The 2+ year duration fits the chronic nature of hookworm-induced iron deficiency 2

Toxoplasmosis from Cat Exposure (Less Likely)

• While multiple cats increase toxoplasmosis risk, this typically causes acute illness rather than isolated chronic anemia
• Toxoplasmosis does not typically present as iron deficiency anemia affecting multiple family members simultaneously

Well Water Contamination with Heavy Metals

• Lead exposure from well water can cause anemia, though typically with additional neurological symptoms
• This would require specific testing of the well water

Immediate Diagnostic Workup

Confirm Iron Deficiency Pattern

• Serum ferritin <12 μg/L is diagnostic of iron deficiency anemia 1, 3
• Check transferrin saturation (<16% suggests iron deficiency) 1
• Complete blood count with red cell indices to assess microcytosis 1

Stool Examination for Parasites

• Quantitative fecal egg counts for hookworm (Necator americanus, Ancylostoma duodenale) 2
• Examine for Trichuris trichiura and Ascaris lumbricoides, though these contribute less to blood loss 2
• Consider Hemoquant testing to quantify fecal heme and confirm upper GI blood loss if available 2
• Multiple stool samples (3 specimens on different days) increase diagnostic yield

Well Water Testing

• Test for bacterial contamination, parasites, and heavy metals
• Assess for fecal contamination that could transmit hookworm larvae

Gastrointestinal Evaluation Considerations

The British Society of Gastroenterology recommends that GI investigations should be considered in all patients with confirmed iron deficiency anemia unless there is significant non-GI blood loss 1, 3. However, in this specific clinical context:

• If hookworm infection is confirmed by stool studies, this explains the anemia and endoscopy may be deferred initially 1
• Upper endoscopy with small bowel biopsies should still be considered to screen for celiac disease (2-3% prevalence in iron deficiency anemia) if hookworm testing is negative 1
• Colonoscopy is indicated if no parasitic cause is found, as dual pathology occurs in 10-15% of cases 1

Treatment Approach

If Hookworm Confirmed

• Antihelminthic therapy (albendazole or mebendazole) for all family members
• Iron supplementation: ferrous sulfate 200 mg three times daily, continued for 3 months after hemoglobin correction to replenish stores 3
• Decontaminate well water source
• Implement proper sanitation and footwear use to prevent reinfection

Concurrent Management

• Iron supplementation should begin immediately while awaiting diagnostic results 3
• Monitor hemoglobin response after 3 weeks to confirm therapeutic response 1
• Address well water safety regardless of parasitology results

Critical Pitfalls to Avoid

• Do not assume dietary deficiency explains the anemia despite "healthy diet" claims—full investigation is required 1
• Do not overlook environmental exposures (well water, soil contact) in rural settings when evaluating unexplained anemia 2
• Do not dismiss parasitic causes in developed countries—hookworm persists in rural areas with poor sanitation 2
• Do not accept upper GI lesions alone (if found) as the sole cause without also investigating the colon, as dual pathology is common 1