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Who’s Who in Dirofilaria Species

Clinician's Brief (Capsule)


April 2014

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The two most common causes of canine filariasis are Dirofilaria immitis and D repens, both transmitted by mosquitoes. D immitis is associated with heartworm disease; D repens is localized to subcutaneous tissues and is associated with nodular disease. Both are considered zoonotic diseases, and treatment regimens differ. Differentiation between these two using morphological characteristics and existing ELISA assays can be difficult, especially where both parasites are found. A high-resolution melting (HRM) analysis coupled to real-time PCR was developed. This can be used to target sequence polymorphisms of the same gene in different species without performing DNA sequencing or using species-specific probes. The test was found to reliably discriminate between the two species in single- and mixed-blood samples.


In most areas of the world, D immitis is the only or primary cause of dirofilariasis, but there are regions where D repens is associated with disease, causing nodular dermatitis because of the subcutaneous location of the worms. These species can be difficult to differentiate with standard microfilarial or heartworm antigen testing, but differentiation is critical, as treatment and prognosis differ, and some patients in endemic regions may have mixed infections. The real-time PCR and HRM described is inexpensive, fast, reliable, and both detects and discriminates between Dirofilaria spp. This PCR–HRM analysis technique has important implications for both human and veterinary medicine, but is likely only practical for regions in which both parasitic diseases are prevalent. Throughout North America, the standard D immitis antigen test is adequate for most patients.—Laura A. Nafe, DVM, MS, DACVIM


Rapid differentiation of Dirofilaria immitis and Dirofilaria repens in canine peripheral blood by real-time PCR coupled to high resolution analysis. Albonico F, Loiacono M, Gioia G, et al. VET PARASITOL 200:128-132, 2014.

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