Fly biting in dogs calls for a broad diagnostic workup
Bottom line
Fly biting in dogs isn’t a diagnosis so much as a clinical sign, and that’s the key takeaway from PetMD’s latest explainer for pet parents. The behavior, also called fly snapping or air biting, describes dogs suddenly snapping at the air as if catching invisible flies. PetMD notes that the episodes can stem from several different categories of disease, including focal seizures, gastrointestinal disease, anxiety, or canine compulsive disorder, and that workups and treatment plans should be tailored to the underlying cause rather than the behavior alone. That framing is consistent with the veterinary literature, which has moved away from treating fly biting as primarily neurologic in every case. (petmd.com)
Why it matters: For veterinarians, fly biting is a reminder to keep a broad differential list. A small prospective case series from the University of Montreal found all seven dogs evaluated for fly-biting behavior had gastrointestinal abnormalities, and the behavior resolved completely in five after GI-directed treatment. Other sources, including VCA and Merck Veterinary Manual, emphasize that focal seizures remain an important differential, but so do GI disease and compulsive disorders, which means history, video review, neurologic assessment, GI screening, and behavior evaluation may all be relevant depending on the case. (petmd.com)
What to watch: Expect continued emphasis on multimodal workups, especially referral pathways to neurology or behavior, and closer attention to post-prandial patterns that may point clinicians toward GI disease first. (petmd.com)
Key facts
- Behavior
- Fly biting, also called fly snapping or air biting, is sudden snapping at the air as if catching invisible flies.
- Clinical meaning
- It is a clinical sign, not a diagnosis.
- Possible causes
- Focal seizures, gastrointestinal disease, anxiety, and canine compulsive disorder.
- Study
- A 2012 prospective case series from the University of Montreal Veterinary Teaching Hospital.
- Sample size
- Seven dogs.
- Study finding
- All seven dogs had gastrointestinal abnormalities.
- Treatment response
- Fly biting resolved completely in five dogs after GI-directed treatment.
- Workup
- History, video review, neurologic assessment, GI screening, and behavior evaluation may all be relevant.
Fly biting in dogs is getting renewed attention through a PetMD explainer aimed at pet parents, but the bigger clinical message for veterinary teams is that the behavior can reflect several very different underlying disorders. PetMD describes fly biting as sudden snapping at the air, often with no visible trigger, and highlights seizure disorders, gastrointestinal disease, anxiety, and compulsive behavior among the main causes. (petmd.com)
That broader view reflects how the profession’s understanding has evolved. Historically, fly biting was often taught as a classic sign of a focal or partial seizure. VCA still notes that fly-biting seizures are a type of focal seizure and that definitive confirmation would require EEG, though that’s often impractical in routine cases. At the same time, more recent clinical discussion has stressed that seizure activity is only one possible explanation, and that the syndrome is often a diagnosis of exclusion. (vcahospitals.com)
One reason for that shift is a 2012 prospective case series from the University of Montreal Veterinary Teaching Hospital that remains central to discussions of the syndrome. As summarized by PetMD’s Jennifer Coates, DVM, all seven dogs in the study had some form of gastrointestinal disease, including delayed gastric emptying, inflammatory GI disease, gastroesophageal reflux, or gastric distention. In five of the seven dogs, fly-biting resolved after treatment of the GI disorder. The report also noted that some dogs showed episodes after meals and that head raising and neck extension often preceded jaw snapping, raising comparisons to Sandifer-like posturing associated with reflux discomfort. (petmd.com)
The literature, however, doesn’t point to a single explanation. A retrospective multicenter study of 24 dogs described fly-catching syndrome as a rare condition with multiple possible etiologies, including epileptoid disorders and obsessive-compulsive disease. Merck Veterinary Manual likewise advises clinicians to rule out physical disease before labeling the behavior as canine compulsive disorder, specifically naming GI and metabolic differentials for jaw snapping or fly biting. PetMD’s more recent canine compulsive disorder coverage also includes fly biting among repetitive behaviors that may warrant referral when severe or difficult to interrupt. (sciencedirect.com)
Expert-facing guidance is similarly pragmatic. VCA recommends a workup that may include screening bloodwork and, depending on the case, infectious disease testing, abdominal ultrasound, MRI or CT, cerebrospinal fluid analysis, and GI evaluation. Because EEG confirmation is rarely practical, clinicians often end up relying on exclusion of other causes plus treatment response. That means case videos from pet parents, timing of episodes, meal association, concurrent GI signs, mentation during events, and response to distraction can all become useful pieces of the puzzle. (vcahospitals.com)
Why it matters: For general practitioners, fly biting is less about identifying a quirky behavior than about avoiding premature closure. If the case is treated as neurologic only, clinicians may miss reflux, delayed gastric emptying, inflammatory GI disease, or a compulsive disorder. If it’s dismissed as behavioral, they may miss focal seizure activity or structural neurologic disease. The practical implication is a staged but broad workup, with referral to neurology, internal medicine, or a veterinary behaviorist when the history or response to initial therapy points that way. (vcahospitals.com)
The message for client communication matters, too. Pet parents often arrive having seen videos or social posts that frame fly biting as either definitely seizures or definitely anxiety. The available evidence supports a more careful answer: it can be either of those, it can be GI-related, and in some dogs more than one process may be involved. Setting expectations around diagnostic uncertainty, trial therapy, and the value of home video can help keep cases moving forward instead of stalling after an unrevealing initial exam. This is an inference drawn from the range of differentials and workup recommendations across the available sources. (vcahospitals.com)
What to watch: Future discussion will likely focus on better phenotyping of cases, especially which dogs should move first toward GI investigation versus neurology or behavior referral, because the current evidence base remains clinically useful but limited by small series and retrospective data. (pmc.ncbi.nlm.nih.gov)