Non Technical Summary
"Wool sucking" is a behavioral condition that involves the repetitive searching, suckling, chewing and ingestion of non-food items. While items made of wool can be the preferred substrate, cats may also seek out and chew items made of cotton, rubber, nylon, paper, cardboard and plastic (e.g. plastic grocery bags, plastic wrap). A negative consequence of this behavior is breakdown of the human-animal bond due to owners' frustration with property damage and restricting their cats' access to favored items. In its most severe form, the cat cannot be maintained safely as an indoor cat. While wool sucking behavior can occur in any cat breed, the incidence is higher in oriental breeds, suggesting a genetic susceptibility. To identify potential genetic components of the compulsive "wool sucking" behavior in cats, DNA samples will be collected via saliva from normal and affected Siamese and Birman cats. Since "wool sucking" is an excellent model in a domesticated animal of human obsessive-compulsive behaviors, the identification of a genetic susceptibility locus could lead to novel cellular pathways that facilitate development of carrier testing, as well as better treatment options for both cats and humans with these disorders.
Animal Health Component
Research Effort Categories
Goals / Objectives
There is a lack of scientific evidence on the causes and appropriate treatments for "wool sucking" in cats. The goal of this study is to determine whether the condition has a genetic basis and whether the same genetic area of interest in Dobermans, exhibiting a similar oral compulsion, will be found in cats. Given the predisposition for oriental breeds to exhibit "wool sucking", it is our hypothesis that the condition is inherited and that a significant genetic susceptibility component will be identified that is associated with Siamese and Birman cats exhibiting this compulsive behavior, and will further uncover the physiological mechanisms and lead to better treatments for compulsive disorders in domestic animals and humans. To date our veterinary research efforts regarding the efficacy of treatment and genetic components has focused on canine compulsive disorder. Recently we identified a significant susceptibility association between a region on chromosome 7 containing the neural cadherin gene (Cdh2) and blanket and flank sucking compulsive behaviors in Doberman Pinschers (Dodman et al, 2010). This finding represents the first genetic locus identified for any animal compulsive disorder and has lead researchers to examine this chromosome 7 locus in humans affected with OCD. Neural cadherin, as well as other cadherin family members, have been implicated as genetic components in the etiology of autism spectrum disorders, which also often manifest repetitive behaviors (Wang et al, 2009). While consumption of non-food items (pica) has been correlated with nutritional deficiencies and intestinal disorders in some species, these factors do not appear to play a role in feline "wool sucking." (Hart et al, 2006). It has been hypothesized that early weaning of cats may predispose them to this behavior. While "wool sucking" can occur in any cat breed, Siamese cats are especially predisposed to the condition (Bamberger, 2006). Bradshaw et al, (1997) reported an early age of onset (typically 18 months or less). Furthermore, 34% of owners in this study reported that their pleasure in owning their cat had been adversely altered by its wool sucking behavior, with 8% reporting a substantial reduction. The amount of monetary damage caused by the cat directly correlated with the reduction in owner's pleasure. Cats affected with "wool sucking" are currently treated with protocols originally developed for treatment of human obsessive compulsive disorder (OCD), which include but are not limited to stress reduction techniques, identifying and limiting exposures to triggers of bouts, and pharmacological strategies. No studies have been reported on the efficacy of treatments for feline wool sucking. However, in a study of 11 cats with psychogenic alopecia, an over-grooming compulsive disorder, treatment with the antidepressants clomipramine and amitriptyline, and the anxiolytic buspirone, plus behavior modification was reported to produce improvement in symptoms in 9 of these cases (Sawyer et al, 1999).
We expect to identify the same associated chromosome region in each Siamese breed for wool sucking. If this is not the case we are still well powered to detect unique associated loci in each studied breed. Single nucleotide polymorphisms (SNPs) will be tested for association using a logistical regression approach in the genome data analysis software. The use of regression to detect association will allow us to include population structure vectors (as determined using multi-dimensional scaling), gender, age, spay/neuter status, and any other variable as covariates. In the past this approach has resulted in the most robust association results in the cat and dog. Statistics - Sample size calculations are difficult for genome wide association studies since the effect size of the associated variants are unknown and largely variable. In the purebred feline we expect the effect sizes to be larger than what has been uncovered in human studies and much more in accordance with what has been found in the canine. As a conservative assumption we are over 90% powered to detect an association within each studied breed as long as the associated locus has an odds ratio greater than 2. We fully expect this to be the case for the feline model therefore we consider our design to result in a more than adequately powered study.