Saturday, June 15, 2024

Dirofilariasis

Practice Essentials

Human dirofilariasis typically manifests as either subcutaneous nodules or lung parenchymal disease, in many cases asymptomatically. The zoonotic filariae of Dirofilaria immitis and Dirofilaria (Nochtiella) repens have become increasingly recognized worldwide as inadvertent human pathogens,
with the usual hosts of these infective nematodes being domestic and wild carnivores. 

Signs and symptoms

D immitis

Most patients (approximately 60%) with human pulmonary dirofilariasis (HPD), caused by D immitis, are asymptomatic. When they do occur, symptoms can include the following:

Localized retrosternal chest pain

Cough

Hemoptysis

Wheezing

Low-grade fever

Chills

Malaise

D repens

Usually, patients notice a single painful subcutaneous lump in the affected area. The areas most commonly affected include the following:

Face and eyelids

Chest wall

Upper arms

Thighs

Abdominal wall

Male genitalia

Ophthalmic involvement may be periorbital,
subconjunctival,
subtenon,
or intraocular.

See Clinical Presentation for more detail.

Diagnosis

Studies used in the diagnosis and evaluation of dirofilariasis include the following:

Complete blood count (CBC) – Using a CBC, eosinophilia may be detected in up to 20% of cases of HPD

Sputum cytology – The presence of eosinophils may support a diagnosis of HPD in patients with a coin lesion observed on radiography, although the test lacks enough specificity for an accurate diagnosis

Serologic studies – Using ELISA, serologic studies may yield positive results in 75% of patients with HPD

Polymerase chain reaction (PCR) assay – Has been successful in the diagnosis of D immitis and D repens infections

Imaging studies – Including chest radiography, computed tomography (CT) scanning, magnetic resonance imaging (MRI), and ultrasonography

Pulsed-field gel electrophoresis

Biopsy – Including surgical biopsy and fine-needle aspiration

Histology – Diagnosing dirofilariasis based purely on histopathology has its pitfalls, especially when the morphology of the nematode is altered owing to inflammatory response or surgical artifact

See Workup for more detail.

Management

Antifilarial medications

In many cases, antifilarial medications are not administered prior to surgical resection of dirofilarial lesions. One group of authors, however, has recommended a single dose of ivermectin followed by 3 doses of diethylcarbamazine (DEC) if the syndrome is strongly suspected prior to surgery.

Surgery

Surgical excision of lesions and affected areas is the treatment of choice for dirofilariasis.
Patients with subcutaneous dirofilarial lesions can usually be treated as outpatients or undergo day-case surgical procedures.

See Treatment and Medication for more detail.

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