Dirofilaria immitis

Canine heart-worm can rarely infect humans.

A filarial nematode with the dog as the primary host.

Female adult parasites release microfilaria into the dog’s blood stream and mosquitoes transmit these to secondary hosts.

The microfilaria reside in subcutaneous tissue and muscle sheaths and then migrate via the capillaries to the right heart.

Worms in soft tissues reach sexual maturity by six months when they propagate and begin the cycle again.

In dogs worms can live in the heart and vascular space causing pulmonary, cerebral, liver, extremity infarct along with vena caval thromboses.

Can cause lung lesions that resemble malignant tumors.

Removal of the worm is the usual treatment.

Humans are accidental hosts, acquiring the worms after bites by infected mosquitoes.

Usually the worms die in the subcutaneous tissues, but occasionally survive and migrate to the right ventricle where they die and embolize to the pulmonary arteries causing thromboses.

95% of cases involve a solitary lung lesion in humans.

Fewer than 100 cases of human disease reported in the U.S.

Number of human cases increasing secondary to uncontrolled infection in dogs.

Most cases asymptomatic, but can have cough, chest pain, hemoptysis eosinophilia and fever.

Evaluation is typical for pulmonary nodules.

The pulmonary nodule in humans usually results from an underdeveloped dead worm, and resection is the usual treatment.

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