Signalment

A 1-year-old 7.0-kg castrated male Shiba Inu dog.

History

The dog was presented for tail chasing, self-injurious behavior, and fearful behavior when having a collar placed onto him or when he sensed a mobile phone vibration. He was obtained from a breeder at 12 weeks of age and lived with a couple in a single-family home. The dog’s tail-chasing behavior, without the presence of any triggers, was noticed immediately after acquisition. At first, the behavior lasted 1 minute in duration twice daily, but over 8 months, the frequency and duration increased to approximately 10 minutes in duration 5 times daily; clapping would stop the behavior. At 11 months of age, the tail-chasing behavior worsened, and the dog would growl while chasing his tail, then chew on it when it was caught. The owners were no longer able to distract the dog by clapping and needed to physically restrain him to stop the behavior; he reverted to the behavior once released. No triggers for the behavior were identified.

The dog was sent to be boarded at a training facility to resolve this behavior. At the facility, the trainer was reported to have used a shock collar, which emitted a vibration before the shock, to stop the dog’s tail-chasing behavior. After 1 week, the trainer found him in the bloodied kennel, with two-thirds of the tail chewed off, presumably eaten. The dog was taken to a veterinary clinic, where a portion of the tail was amputated, leaving 2 inches of the tail. After surgery, the referring veterinarian prescribed trazodone (50 mg [7.1 mg/kg], PO, q 12 h) for the tail-chasing behavior and carprofen (18.7 mg [2.6 mg/kg], PO, q 12 h) for pain management.

After discharge, the surgical site had healed well, but the tail-chasing behavior continued. No longer able to reach his tail, the dog began chewing his hindlimb instead. Moreover, at home, he began showing new behaviors such as retreating, screaming, panting, freezing, trembling, urinating, and defecating. These behaviors were seen whenever he sensed vibrations from a smartphone and also when the owners tried to place a collar on his neck for walks, and the owners described the anxiety as severe (9/9).

Ten days after discharge, the dog was taken to the referring veterinarian for suture removal. Because the tail-chasing behavior had not improved with trazodone, it was discontinued. The veterinarian suspected that the screaming, panting, and trembling behaviors were due to pain, although the pain was not localized during a physical examination. Carprofen (18.7 mg [2.6 mg/kg], PO, q 12 h) was continued, and gabapentin (50 mg [7 mg/kg], PO, q 12 h) was prescribed. Acupuncture was performed every other day for 1 week. One week later, no improvements were seen so further diagnostics were performed, including a neurological examination, dermatological examination, MRI (SIGNA Creator 1.5T MRI scanner; GE Healthcare) of the brain and spine, CSF analysis, CBC, and serum chemistry. The results were all unremarkable.

Physical Examination Findings and Laboratory Results

On physical examination, the surgical site of the tail had healed without complications. No significant findings were noted during either of the physical examination and neurological examination, and no evidence of pain was identified by physical examination. During the consultation, the dog displayed a tense body position with dilated pupils. He leaned on the owner for the entire visit and never fully relaxed. Suddenly, he screamed and stuck his head between the owner and the sofa when the owner’s phone vibrated. He panted for 30 minutes and never fully recovered.

Diagnosis

The differential diagnosis for the dog’s tail-chasing and mutilating included medical and behavioral causes.^1,2 Medical differentials, including pain (bruising, fracture of the tail, and vertebrae injury) and neurological disease (seizures, vestibular disease, and encephalitis), were ruled out.^1,2 Due to lack of abnormal findings, despite extensive medical examinations, the clinical signs were attributed to a behavioral cause. Behavior differentials for tail-chasing and mutilating behavior included compulsive disorder (CD), displacement behavior, and attention-seeking behavior.^2,3 Displacement behaviors (normal behaviors that are shown at an inappropriate time or out of context for the situation) were considered less likely because there were no identifiable triggers that initiated the tail-chasing behavior.^3,4 Attention-seeking behavior was ruled out because the behavior showed no relation to the owners’ presence, proximity, or responses.⁵ The dog presented with a repetitive, ritualistic pattern of tail-chasing behavior with no change in mentation, which was consistent with CD.^3,6,7 The age of onset and breed, without apparent triggers, may have explained some genetic predisposition in his CD.⁸

In addition, he was diagnosed with canine post-traumatic stress disorder (C-PTSD), due to his retreating, screaming, panting, freezing, trembling, urinating, and defecating behaviors associated with putting on a collar and phone vibrations.^9,10 Literature on C-PTSD is limited, but C-PTSD is defined as a profound, nongraded, extreme response that manifests as intense avoidance, escape, or anxiety elicited in response to exposure to an identifiable, unavoidable stimulus when these behavioral and physical signs were first felt.^9–11 His extreme fear and anxiety behaviors started only after being sent to the board and train facility where a shock collar was used. It is likely that his C-PTSD was caused by a traumatic experience, specifically the vibration preceding the electric jolt emitted from the shock collar.

Treatment

The owners were instructed to avoid using any forms of aversive training, especially a shock collar, to minimize the dog’s fear and stress.^3,7 The use of phones in vibration mode was to be stopped. The owners were instructed to use a body harness rather than a neck collar for walks.

As a part of pharmacological treatment, the drugs that indicate both CD and C-PTSD were considered. Selective serotonin reuptake inhibitors and tricyclic antidepressants (TCAs) have been reported to be effective treatment for CD in dogs.^12–16 Fluoxetine, a selective serotonin reuptake inhibitor (5 mg [0.7 mg/kg], PO, q 24 h), was prescribed because it was indicated for both CD and C-PTSD.^4,9,17 Fluoxetine blocks the presynaptic reuptake of serotonin and downregulates postsynaptic serotonin receptors long term.¹⁷ Since fluoxetine takes about 4 to 6 weeks to see the full effects, gabapentin, a structural analog of γ-aminobutyric acid, was increased to 100 mg (14.3 mg/kg), PO, every 12 hours.^9,18–21 In dogs, gabapentin has also been indicated as an adjunctive treatment for CD and C-PTSD.⁹ In addition, in humans, gabapentin has been reported to be effective for neuropathic pain, anxiety, or PTSD.²² The owners were informed of potential side effects of fluoxetine, including reduced appetite, sedation, vomiting, diarrhea, anxiety, and tremors,¹⁷ and gabapentin, including sedation, ataxia, lethargy, and vomiting.²¹

To increase predictability and consistency in the dog’s environment, a command-response-reward program that consistently rewarded desirable behaviors and ignored undesirable behaviors was recommended.^3,15 Also, a hand target, in which the dog was to touch the palm of the owner’s hand with his nose when the cue was given, and eye contact cues were to be used to help interrupt and redirect undesired behaviors.³ Next, the dog was to be encouraged to lie down on a mat comfortably; this behavior was to be positively reinforced with treats and praise, and over time, the duration was to be increased with continued reinforcement and praise.⁹ The owners were also informed about classical counterconditioning, the process of giving high-value treats to the dog in the presence of an unexpected trigger such as mobile phone vibrations, as a possible method for future behavior modification.

Follow-up

No significant behavior changes or side effects from medications were noted 4 weeks postappointment. However, attaching the body harness for walks went smoothly without any issues. His fearful behavior had also significantly improved (2/9), and he was able to respond to cues successfully, such as the hand target, and eat given treats when he sensed vibrations from the owners’ phones. Contrastingly, the tail-chasing behavior had not improved, but seemed to be as severe as it was just prior to the traumatic experience at the training facility. Eight weeks postappointment, no sign of improvement was reported for the tail-chasing behavior, but his fearful behaviors seemed to be fully resolved.

Fluoxetine was increased to 1.5 mg/kg, PO, every 24 hours for the dog’s tail-chasing behaviors. One week later, the owners reported that he had lost his appetite and hadn’t eaten for 3 days. Fluoxetine was changed back to the previous dosage, and gabapentin was increased to 200 mg (28.6 mg/kg), PO, every 12 hours.

At 12 weeks, the tail-chasing behavior was still reported as severe (7/9), so a new medication, clomipramine, was recommended. Clomipramine is a TCA that affects both serotonergic and noradrenergic neural transmission in the CNS and the most serotonin-specific among commercially available TCAs.²³ Clomipramine has been used successfully in cases of CD.^14–16 Fluoxetine was weaned gradually over 2 weeks; 5 days after fluoxetine was discontinued, clomipramine was begun at 10 mg (1.4 mg/kg), PO, every 12 hours. The owners were informed of potential side effects, including anorexia, sedation, lethargy, vomiting, diarrhea, anxiety, irritability, insomnia or hyperactivity, and panting.²³

At the 7-month follow-up, the owners reported that the tail-chasing behavior had improved significantly to 2/9, occurring 3 to 4 times/wk, and they were able to redirect him easily with a hand target cue. The dog no longer showed fear-related behaviors to unavoidable phone vibrations. The dog’s behavioral and medical care was transferred to the referring veterinarian with recommendations for annual CBC and chemistry panels, along with other medical treatment as necessary.