CASES/YEAR
40 (US); 800 (Global)
OTHER NAMES
Zoonotic filariasis caused by Difilaria species;
INCUBATION
3-6 months for filariasis;
INITIAL SYMPTOMS
Subcutaneous mass (most common); Lung nodule (coin lesion on chest x-ray or chest pain, cough, and hemoptysis); Eye infection (presence of worm, blurry vision, or eye pain); [Guerrant, p. 750-8]
COMMENTS
Various Difilaria species infect domestic and wild animals. Humans are accidental hosts. Mosquitoes transmit the infection. Microfilaraemia rarely occurs. The infection may cause a pulmonary fibrotic nodule, which is most commonly asymptomatic. Eosinophilia is infrequent. [CCDM, p. 215] Dirofilariasis is the most commonly recognized zoonotic filarial infections in humans. Human infections are derived from a wide variety of mammalian hosts. Dogs are the natural hosts for D. immitis and D. repens. Raccoons are the natural hosts for D. tenuis. Subcutaneous infections present as 0.5 to 1.5 cm nodules. In some eye infections, worms may be identified in the conjunctiva. About 50% of patients with lung nodules by radiography are asymptomatic. Low grade fever may occur in cases with lung involvement. [Guerrant, p. 750-8] D. repens (dogs) and D. tenuis (raccoons) cause subcutaneous nodules. D. immitis (dogs) usually causes a solitary pulmonary nodule. Cheat pain, cough, and hemoptysis are uncommon. Eosinophilia is rare. [Harrison ID, p. 1144] D. immitis causes dog heartworm. In humans the worm dies in the right side of the heart and pulmonary vessels, causing pulmonary infarcts (cough, chest pain, and hemoptysis). [PPID, p. 3471]
DIAGNOSTIC
Identification of worms in tissue sections; Eosinophilia in less than 15% of cases; [PPID, p. 3471]
SCOPE
D. immitis, the dog heartworm, is widespread in metropolitan areas of the world. D. repens infects dogs and cats in Europe, Africa, SE Asia, and elsewhere. D. tenuis has been identified in North America. [Guerrant, p. 751]
SIGNS & SYMPTOMS
-
>fever
-
H eosinophilia
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R chest pain
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R cough
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R hemoptysis
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S skin or subcutaneous nodule
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X cystic or cavitary lesions
RESERVOIR
Cats, Dogs, Wild Animals
TREATMENT
Often cured by the surgical removal of a single worm; [Guerrant, p. 758]
REFERENCES FOR CASES/YEAR
1. (US) Most of these accidental infections occur in the southeastern US; [PPID, p. 3477]
2. (Global) There are probably hundreds of cases of Dirofilariasis every year; [Guerrant, p. 752] Guesstimate: 800 worldwide and 40 cases/year in the US;