Allergic dermatitis by Dirofilaria repens in a dog: clinical picture and treatment

Abstract

Adult stages of Dirofilaria repens (Nematoda, Filarioidea) reside in the subcutaneous tissues of the definitive or occasional host as dogs, other animals, and humans, and it is transmitted by mosquitoes. Canine infections with adults and circulating larvae of D. repens are often considered asymptomatic, although in some cases, the parasite causes subcutaneous nodules, diffused dermatitis, skin lesions, and itching. This report provides a complete clinical description of an unusual case of allergic diffused dermatitis caused by D. repens in a naturally infected dog and its successful treatment with the use of a spot-on solution containing imidacloprid 10%/moxidectin 2.5%. The dog presented multiple pustules and alopecic areas with lichenification, hyperpigmentation, and erythematous scaling margins without pruritus. Histological examination was compatible with allergic dermatitis. After being unsuccessfully managed for suspected food hypersensitivity, with a significantly worsening of the lesions, a Knott’s analysis detected nematode larvae in the blood. Morphological and molecular identification showed them to be D. repens. The dog was then treated with a single administration of a spot-on formulation containing imidacloprid 10%/moxidectin 2.5%, and the dermatological signs completely resolved within 2 months after treatment. The dog showed no recurrence of the lesions, and no circulating microfilariae were found upon microscopic and molecular examination for six consecutive months after treatment. This report indicates the apparent primary role of D. repens in causing hypersensitivity-like skin disease without pruritus in a dog. It also confirms, as recently shown elsewhere, the efficacy of imidacloprid 10%/moxidectin 2.5% in the treatment of dermatitis caused by D. repens.

Field clinical study evaluating the efficacy and safety of an oral formulation containing milbemycin oxime/praziquantel (Milbemax®, Novartis Animal Health) in the chemoprevention of the zoonotic canine infection by Dirofilaria repens

“…In fact, minimizing the number of infected dogs acting as reservoirs of the parasite is central to avoid infective blood meals for the mosquitoes and to reduce the occurrence of D. repens in their vectors, in dogs and humans. From a practical standpoint, the prevention of D. repens infection is important in canine clinical practice, as adult parasites and/or circulating mff may induce different cutaneous signs in infected dogs and pose challenging issues for the diagnosis and treatment of these dog dermatopathies [3–6]. …”

“…In dogs, the infection may be asymptomatic although cutaneous signs of varying severity, such as dermatitis, (sub)-cutaneous nodules and lesions, itching and various allergic reactions could be caused by both adult stages and/or circulating mff [3–6]. Importantly, this nematode has a zoonotic potential and the human infection usually presents with subcutaneous nodules, pruriginous urticarioid patches, transient swellings and eosinophilia, although photophobia, conjunctival irritation and nodules or cysts in the eye or in the periocular tissues have also been reported [7, 8].…”

Microfilaricidal efficacy of a single administration of Advocate® (Bayer Animal Health) in dogs naturally infected with Dirofilaria immitis or Dirofilaria repens

“…cough, exercise intolerance, dyspnea, tachypnea, syncope, respiratory failure and death (Simón et al, 2012). Subcutaneous dirofilariosis is either subclinical or presents with dermatitis, (sub)cutaneous nodules and lesions, pruritus and allergic reactions (Bredal et al, 1998;Hargis et al, 1999;McCall et al, 2008;Rocconi et al, 2012).…”

Dirofilariasis in Russian Federation: a big problem with large distribution

“…The L3 larvae molt first into fourth-stage larvae (L4) and then adults within the vertebrate host [15,16]. Canine dirofilariasis, caused by D. repens, induces such clinical signs as a pruritus, dermal swellings, subcutaneous nodules, alopecia and erythema [17][18][19][20]. Canine infestation caused by D. immitis is frequently asymptomatic, depending on worm burden and duration of infection [21,22].…”