Can a worm parasite cause neutropenia (low neutrophil count)?

Worm Parasites Can Cause Neutropenia

Yes, worm parasites can cause neutropenia (low neutrophil count) through several mechanisms, including direct consumption of neutrophils and immune-mediated destruction.

Mechanisms of Parasite-Induced Neutropenia

Direct Evidence from Research

Certain parasitic worms directly influence neutrophil counts and function. For example:

• Filarial worms containing Wolbachia endobacteria can cause significant neutrophil accumulation around the worms, potentially depleting circulating neutrophils 1
• The neutrophil response is characteristic of endobacteria-containing filariae, as demonstrated by studies showing neutrophil chemotaxis and activation induced by endobacterial products 1

Pathophysiological Mechanisms

Neutropenia in parasitic infections can develop through:

1. Increased peripheral destruction - Immune complexes formed during parasitic infections can lead to increased destruction of neutrophils
2. Sequestration - Neutrophils may be sequestered at sites of infection rather than circulating in peripheral blood
3. Bone marrow suppression - Chronic parasitic infections can suppress bone marrow production of neutrophils

Clinical Significance of Neutropenia

The severity of neutropenia is classified as:

• Mild: 1000-1500 cells/mm³
• Moderate: 500-1000 cells/mm³
• Severe: <500 cells/mm³ 2

The risk of infection increases with:

• Severity of neutropenia (particularly when ANC <500 cells/mm³)
• Duration of neutropenia (especially >7 days)
• Rapid decline in neutrophil count 3

Diagnostic Approach for Suspected Parasitic Neutropenia

When evaluating neutropenia in a patient with suspected parasitic infection:

1. Complete blood count with differential is essential for confirming neutropenia 3
2. Blood films should be examined for malaria parasites, with thrombocytopenia or malaria pigment in neutrophils and monocytes serving as potential clues to malaria, even if films are initially negative 4
3. Travel history is crucial, as patients returning from endemic areas are at risk for parasitic causes of neutropenia 4

Management Considerations

For patients with neutropenia potentially related to parasitic infection:

1. Treat the underlying parasitic infection:

   • For malaria, rapid blood malaria antigen tests and three thick and thin blood films should be performed 4
   • If cerebral malaria is suspected and there will be a delay in obtaining results, anti-malarial treatment should be initiated promptly 4

2. Monitor for infectious complications:

   • Fever (>38.5°C) in a neutropenic patient requires prompt evaluation 4
   • Empiric antibiotics may be necessary if febrile neutropenia develops 4

3. Consider hematopoietic growth factors in cases of severe neutropenia with increased risk of infection, but avoid in infections not directly related to neutropenia 3

Important Caveats

• Neutropenia in returning travelers may be due to various parasitic infections including malaria, which is a medical emergency requiring prompt diagnosis and treatment 4
• The presence of malaria pigment in neutrophils can be a diagnostic clue even when blood films are negative for parasites 4
• Testing for malaria is important even in patients who have taken anti-malarial prophylaxis or residents from endemic areas who are thought to be immune 4

Prompt identification and treatment of the underlying parasitic infection is the most effective approach to resolving parasite-induced neutropenia.