Canine Compulsive Behavior: An Overview and Phenotypic Description of Tail Chasing in Bull Terriers

Publishing Author : Alice Moon-Fanelli, PhD
Date Published : Unknown

Recent estimates indicate that between six and fifteen million dogs and cats are
euthanized each year in the United States at shelters alone, with less than five
percent due to medical reasons. Studies inv
dogs is a debilitating condition and many dogs have been euthanized for this
behavioral disorder.
Tail chasing is the most common form of compulsive disorder expressed by Bull
Terriers. Within our preliminary study population of 250 Bull Terriers, 86 had
expressed some degree of tail chasing during their lives. This percentage (34
percent) is an overestimate for the entire breed population since the data were
solicited from first degree relatives of affected dogs and affected dogs presenting
at the Tufts University School of Veterinary Medicine behavior clinic.
Nevertheless, the data suggest that tail chasing is represented in the gene pool
to a marked degree since it is coming to phenotypic expression with a significant
frequency within our study population.
Tail chasing is a repetitive behavior that is expressed as slow to rapid circling
with the dog’s attention directed toward its tail or rapid spinning in tight circles
with no apparent focus on the tail. Within the same dog, these two forms of
expression (slow, focused; rapid, unfocused) are typically expressed
interchangeably. The development of tail chasing behavior differs among
individuals varying from a sudden to a gradual onset. For some dogs, the onset
of tail chasing behavior occurs suddenly with no apparent trigger. For other dogs,
the onset is sudden but coincides with exposure to identifiable yet relatively
benign psychological, physiological or environmental triggers that are interpreted
as increasing anxiety. Other dogs show a gradual onset typically associated with
identifiable eliciting parameters. These dogs show occasional, mild tail chasing
that gradually escalates to daily bouts of tail chasing at clinical proportions. The
onset of tail chasing typically occurs between 6-16 months of age, although it
may present at any age. The range of age of onset we have observed is three
months to ten years of age. Treatment of tail chasing consists of changes in
management and pharmacological therapy. Serotonin re-uptake inhibitors
(clomipramine, fluoxetine) used to treat people with OCD have been the most
effective drug therapy for tail chasing in Bull Terriers.
Pedigree data for a large Bull Terrier family affected with tail chasing indicate the
disorder has a heritable component in this breed. Two subsets of tail chasing
behavior that differ in the degree (frequency, duration, and intensity) of
expression in the Bull Terrier population have been observed. For genetic
analyses, the degrees of manifestation have been separated into two threshold
categories; clinical and sub-clinical. Review of the pedigree data indicates that
“subclinical” tail chasers have produced clinically affected tail chasing offspring
and vice versa. In addition, some sub-clinical tail chasers develop the full blown
“clinical” tail chasing condition in response to changes in their environment.
Based on the segregation of the phenotype within litters and between various
matings, tail chasing is most likely transmitted as a polygenic disorder, possibly
involving a small number of genes.
The American Kennel Club Canine Health Foundation has sponsored a study to
collect blood samples from Bull Terrier families with compulsive tail chasing
behavior. Our goal is to establish a DNA bank for subsequent research intended
to identify genetic markers that are linked to the gene(s) for compulsive tail
chasing in this breed. Dr. Elaine Ostrander and her team will conduct the
molecular aspects of this work. Considering the robust nature of the phenotype,
its familial basis, and the current status of the canine genome map, gene
mapping studies constitute an appropriate approach towards reducing the
frequency of occurrence of compulsive tail chasing in the Bull Terrier breed.
Based on clinical experience the clinical signs, developmental expression and
response to treatment show considerable conformity in the nature of tail chasing
between breeds. Genetic information gleaned from this investigation could be
beneficial for all breeds exhibiting tail chasing behavior and may be applicable to
other forms of compulsive behavior as well. If genes are ultimately identified and
the function of the gene(s) in other species is known, this may facilitate
identifying the actual underlying physiological mechanism that has so far eluded
Dr. Moon-Fanelli’s work is being supported by the following grant from the AKC
Canine Health Foundation:
No. 1871: Bull Terrier Families Affected With Compulsive Tail Chasing Behavior:
Behavioral Diagnosis, Pedigree Collection and DNA Isolation for Future Genetic
Mapping Studies (Sponsored in part by the Bull Terrier Club of America Welfare
Biographical Profile
Alice Moon-Fanelli, PhD, is a behavior geneticist and consultant on companion
animal behavior at Tufts University School of Veterinary Medicine (TUSVM). She
received her MS and PhD from the University of Connecticut in etiology and
canine behavior genetics and completed a postdoctoral fellowship at TUSVM
researching animal models of obsessive compulsive disorder. She is currently
employed as a clinical assistant professor at TUSVM and is actively involved in
research, behavior consultations and teaching. Her research efforts focus on the
inheritance of behavioral disorders in companion animals, with a current
emphasis on the inheritance of compulsive tail chasing in Bull Terriers.

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