Can a hookworm infection cause a neutrophil count of 45 and a monocyte count of 52?

Hookworm Infection and Abnormal White Blood Cell Differential

No, a hookworm infection would not typically cause a neutrophil percentage of 45% and monocyte percentage of 52% in a 15-year-old boy—this differential is highly atypical for hookworm and suggests an alternative diagnosis, most likely an intracellular bacterial pathogen or chronic parasitic infection other than hookworm.

Expected Hematologic Findings in Hookworm Infection

Characteristic White Blood Cell Pattern

• Hookworm infection typically causes monocytosis (elevated monocyte count), not monocyte predominance to 52% 1
• Natural hookworm infection induces increased circulating monocytes with a regulatory profile, but the absolute monocyte count elevation (mean 555.2 ± 191.0 cells/mm³) occurs alongside normal differential percentages 1
• The hallmark laboratory finding in hookworm is iron deficiency anemia, not dramatic shifts in white blood cell differential 2

Neutrophil Response in Hookworm

• Hookworms trigger a focal neutrophilic response at sites of tissue attachment and feeding in the intestinal mucosa, characterized by local hemorrhage and tissue cytolysis 2
• However, this localized neutrophil recruitment does not translate to neutropenia (low percentage) in the peripheral blood 2
• Hookworms actively evade neutrophil-mediated immunity by secreting deoxyribonuclease to degrade neutrophil extracellular traps (NETs), allowing larvae to escape neutrophil killing 3

Alternative Diagnoses to Consider

Intracellular Bacterial Pathogens

The differential showing relative neutropenia (45%) with marked monocyte predominance (52%) strongly suggests an intracellular pathogen such as Salmonella or other intracellular bacteria 4

• Monocyte predominance specifically suggests the presence of an intracellular pathogen such as Salmonella 4
• This pattern is characteristic of infections requiring monocyte/macrophage-mediated immunity rather than neutrophil-mediated responses 4

Chronic Parasitic Infections (Non-Hookworm)

Chronic parasitic infections such as amebiasis, giardiasis, or tuberculous GI involvement should be strongly considered, particularly if the patient has epidemiologic risk factors 5

• These infections can cause both neutropenia and monocytosis, especially in patients from endemic areas 5
• Stool studies including examination for ova and parasites, bacterial culture, and specialized testing for amoebae and giardia are essential 5

Ehrlichiosis

• Ehrlichiosis characteristically presents with leukopenia with neutrophil percentages in the normal-to-low range (45-75% is normal, but absolute counts are low) and monocyte involvement 4
• However, monocyte percentages of 52% would be extraordinarily high even for ehrlichiosis 4

Critical Diagnostic Approach

Immediate Evaluation Required

• Complete blood count with absolute values (not just percentages) is essential—percentages can be misleading if total white blood cell count is abnormal 4
• If the absolute neutrophil count is <500 cells/mm³, the patient is at considerably greater risk for serious bacterial infection 4
• Blood cultures should be obtained immediately if the patient is febrile, as approximately 50-60% of febrile neutropenic patients have occult infection 5

Specific Testing

• Stool examination for ova and parasites to confirm or exclude hookworm and identify alternative parasitic causes 5
• Blood smear examination for morulae (intracellular inclusions) if ehrlichiosis is suspected 4
• TB screening with tuberculin skin test or interferon-gamma release assay if epidemiologic risk factors are present 5

Important Clinical Pitfall

The most critical error would be attributing these laboratory findings to hookworm infection and missing a potentially life-threatening intracellular bacterial infection or other serious pathogen. The infection risk is inversely proportional to the absolute neutrophil count, with greatest risk when ANC is below 100/µL 5. Common infection sites in neutropenic patients include the alimentary tract, sinuses, lungs, and skin 5.