Efficacy of afoxolaner (NexGard®) for the treatment of myiasis caused by the zoonotic tumbu fly, Cordylobia anthropophaga, in domestic dogs under field conditions.

Abstract

Cordylobia anthropophaga is a major cause of furuncular myiasis in dogs and humans in sub-Saharan Africa, yet evidence for pharmacological control remains limited. Current management relies mainly on mechanical larval removal, and no controlled studies have assessed the efficacy of modern antiparasitic agents. This study evaluated the curative and preventive efficacy of a single dose of afoxolaner (NexGard&#xae;) in dogs with naturally acquired C. anthropophaga infestation under field conditions and explored a possible indirect protective effect in puppies after maternal treatment. A randomized, blinded, negative-controlled field study was conducted in Samburu County, Kenya, and included 104 naturally infested dogs allocated to a treated group (n&#x202f;=&#x202f;53) or an untreated control group (n&#x202f;=&#x202f;51). Clinical evaluations were performed on Days 0, 15 (&#xb1;2), 30 (&#xb1;2), and 45 (&#xb1;2). Efficacy was assessed based on the presence of active nodules and clinical scores. Additional observational data were collected from puppies born to or nursing from treated bitches. Compared to the control group, parasiticide efficacy was 94% on Day 15 and 100% on Day 30. The number of parasite-free dogs reached 86.3% on Day 15, 100% on Day 30, and 95.3% on Day 45. Treated dogs showed a significant clinical improvement from the first post-treatment assessment, whereas infestation persisted in controls (nodules: OR = 0.003, 95% CI 0.001-0.017; skin lesions: OR = 0.010, 95% CI 0.002-0.051; lymph node: OR = 0.013, 95% CI 0.002-0.074; body condition: OR = 0.073, 95% CI 0.027-0.195; all p&#x202f;<&#x202f;.001), with large effect sizes at the final visit for all outcomes (r&#x202f;=&#x202f;0.521-0.793). No C. anthropophaga infestations were detected in examined puppies from treated dams, including puppies exposed during pregnancy or lactation, up to 4 weeks after birth and up to 11 weeks of age, respectively. Afoxolaner appears effective to control canine cordylobiosis and may offer indirect protection to puppies, warranting further investigation.