Canine ocular onchocerciasis in New Mexico: Risk factors for disease

Cutaneous filarioid nematodes of dogs in the United States: Are they emerging, neglected, or underdiagnosed parasites?

Filarioid nematodes, which are vector-borne parasites of cosmopolitan distribution, of dogs are medically important. They are represented by species in which microfilariae were found to be circulating in the bloodstream (e.g., Dirofilaria sp., Acanthocheilonema sp., and Brugia sp.) or skin-dwelling (e.g., Cercopithifilaria sp. and Onchocerca sp.). Those species whose microfilariae are detected in blood have been extensively studied, especially Dirofilaria immitis, due to their clinical importance. In recent decades, there has been an increased interest by the scientific community in filarioid nematodes whose microfilariae are detected in the skin because of the zoonotic aspect of Onchocerca lupi. In the United States (US), although D. immitis has been considered the main filarioid infecting dogs, the intense animal movement and global canine filarioid diversity may indicate that the likely presence of cutaneous filarioid nematodes is more common than previously expected. Hence, a question remains: Are these canine filarioid nematodes emerging, neglected, or simply underdiagnosed in the US? In this review, we provide an overview of pertinent information that briefly summarizes the biology of the different canine filarioid nematode species, clinical signs associated with infections, and currently available diagnostic tools using molecular and microscopy-based methods and highlight knowledge gaps where research and surveillance efforts remain necessary. The data herein presented serve as an alert to the scientific community about the importance of filarioid nematodes infecting dogs other than D. immitis. Additionally, the zoonotic potential of several filarioid species reinforces the necessity of a proper diagnosis and the need for broader surveillance to understand their diversity and distribution, to highlight the potential introduction of certain species, and mitigate their establishment in the country and new animal and human cases.

Extensive Aberrant Migration of Onchocerca lupi in a Dog

A 13-year-old Labrador retriever mixed breed dog from Arizona was presented for evaluation of an acute onset of a head tilt as well as vocalization and head shaking upon palpation of the ears. The dog was previously treated for ocular onchocercosis associated with the right eye 10 years earlier. Ophthalmic examination at presentation revealed irregular, tan-colored, masses on the sclera of both eyes. Otoscopic evaluation of the left ear was limited because the canals were stenotic and inaccessible. Cytology did not reveal any infectious etiologies and the dog was subsequently treated with an anti-inflammatory dose of prednisone for 10 days. Two weeks later the dog developed a mild dysphonia and stridor that eventually progressed to include difficulty breathing. The dog was euthanized and postmortem examination revealed white-to-tan nodules identified in the episclera, trachea, subcutis around the nares, external ear canals, and within the fascia overlying the temporalis muscle, as well as in the parietal pleura, and pericardium. There was also a large mass that obliterated the laryngeal cartilage that partially occluded the laryngeal opening. Microscopically, the described nodules consisted predominately of lakes of abundant mineralized debris, admixed with granulomatous inflammation centered around degenerate nematodes that were subsequently confirmed by PCR and sequence analysis to be Onchocerca lupi. The veterinary literature is comprised of only 2 reports that describe aberrant O. lupi migration to the trachea and larynx. Here, we provide the first detailed description of a dog with extensive aberrant onchocercosis.