Human obsessive-compulsive disorders (OCD) and canine compulsive disorders (CCD) manifest as time-consuming, repetitive behaviors that may cause emotional distress and functional impairment, frequently arise between pre-pubescence and early social maturity and may be precipitated by anxiety or stress. The behavior soon becomes ingrained and may be performed even in the absence of obvious stressors.

Results from 2 longitudinal canine studies focusing on phenotypic, pedigree and molecular genetic data have identified two proposed models of CCD; blanket/flank sucking in Doberman pinschers and tail chasing in bull terriers, which appear to have compelling parallels with human obsessive-compulsive disorder and possibly autism spectrum disorder (ASD).

Owners of Doberman pinschers with blanket sucking, flank sucking, or both and bull terriers with tail chasing behavior were surveyed regarding the age of onset, triggers, frequency, duration, interruptibility, degree of disruption to the dogs' normal functioning and the owners' relationship with the dog, and associated medical and physical consequences. A putative association of blanket sucking and flank sucking with pica was examined by comparison of affected dogs with unaffected dogs. Association of tail chasing with various behavioral and physical characteristics (sex, coat color, trancing, fears and phobias, sound sensitivity, owner-directed aggression, episodic sudden onset aggression, seizure events, skin allergies) were examined by comparison of dogs with tail chasing behavior with unaffected dogs.

Apart from the difference in the object of oral activity between blanket and flank suckers, age of onset was the only variable that significantly differed between the 2 conditions with blanket sucking behavior expressed at a slightly younger age. Dogs with blanket or flank sucking behavior had a higher prevalence of pica than the unaffected population. The results suggest that blanket and flank sucking are apparently related conditions that can occur with sufficient intensity to cause medical sequelae requiring veterinary attention. We concluded that these non-nutritive suckling behaviors share similarities with other canine compulsive behaviors and are associated with pica.

A close association of tail chasing with sex, trance-like behavior (fixed stare and associated immobility), and episodic explosive aggression (putatively a partial seizure event) was identified. In bull terriers with tail chasing behavior, there was a slight (8%) increase in the susceptibility of males to develop tail-chasing behavior, compared with females. Environmental, social and situational phobias and low level owner-directed aggression did not significantly associate with tail chasing in the final log-linear model, but did have significant associations in earlier analyses that did not include the behaviors of episodic aggression and trance-like behavior.

In reviewing these results, a "syndrome of symptoms" beyond those typically reported for compulsive disorders became apparent. Some bull terrier owners voluntarily reported that their dogs were "socially withdrawn" and some specifically used the term "autistic" to describe their dog's personality. The repetitive nature of the behavior, potential for self-injurious behavior as a result of tail chasing, early onset life occurrence, and precipitating events triggering onset is consistent with the literature reported for both OCD and autism. Upon re-evaluation of reports from owners of affected bull terriers, a recurring theme describing impaired social interactions including lack of responsiveness to human and conspecific communicative signals, difficulty training, and a general inability to focus on tasks and relationships became apparent. The end result was often reduced or complete social isolation for these dogs. Affected dogs were often unable to cope with normal daily stressors and exhibited noise sensitivities, unusual fears and phobias, and a lack of self control. Fixation and fascination with objects was a recurring theme in owner reports. Owners of tail chasers often offer balls to redirect the dog from tail chasing, but the behavior with the ball becomes equally as consuming as the tail chasing. Finally, the incidence of tonoclonic seizures in a small percentage of dogs in our bull terrier pedigree adds further credence to the hypothesis that this constellation of behavior and health symptoms could pose as a model for autism spectrum disorder, a neurodevelopmental disorder characterized by difficulties in communication and social interactions, stereotypic behaviors, as well as learning defects.

Pedigree analyses support a familial pattern of inheritance for flank/blanket sucking in Doberman pinschers and tail chasing in bull terriers. Complex segregation analyses for the incidence of tail chasing in bull terriers is underway as are molecular studies. Preliminary results published for blanket/flank sucking in Doberman pinschers identified a highly significant association of flank/blanket sucking in Doberman pinschers with the CDH2 region on chromosome 7. To our knowledge this was the first genetic locus identified for any animal compulsive disorder and raises the intriguing possibility that CDH2 and other neuronal adhesion proteins are involved in human OCD. A genetic association of cadherins with autism spectrum disorder also has been reported.

In summary, although there are many parallels between tail chasing in bull terriers, flank/blanket sucking in Doberman pinscher and human obsessive-compulsive disorder, if clinical signs and genetic data suggest that these canine conditions are more closely related to autism, a new channel of translational research could be pursued relative to this common and extremely debilitating condition.

References

1.  Moon-Fanelli AA, Dodman NH, Cottam N. Blanket and flank sucking in Doberman pinschers. J Am Vet Med Assoc 2007;231(6):907–912.

2.  Moon-Fanelli AA, Dodman NH, Famula TR, Cottam N. Characteristics of compulsive tail chasing and associated risk factors in bull terriers. J Am Vet Med Assoc 2011; 238(7):883–889.

3.  Dodman NH, Karlsson EK, Moon-Fanelli A, Galdzicka M, Perloski M, Shuster L, Lindblad-Toh K, Ginns EI. A canine chromosome 7 locus confers compulsive disorder susceptibility. Mol Psychiatr 2010; 15:8–10.