self‐mutilation has been studied much more in humans and non‐human primates than in domestic animals. In non‐human primates, it is believed by many to be a maladaptive coping mechanism. Rearing in a suboptimal environment, and specifically social isolation, is considered a risk factor (Dellinger‐Ness and Handler 2006). Stressors such as relocation have also been known to lead to self‐injurious behavior (SIB) in some primates (Davenport et al. 2008). SIB in dogs and cats is often but not always associated with tail chasing, circling, and subsequent tail tip mutilation. Self‐mutilation is most likely to be associated with pain, dysesthesia, or paresthesia. One case has been documented of a 30‐month‐old Labrador retriever that presented with acute onset tail mutilation (Zulch et al. 2012). Radiographs of the tail revealed some soft‐tissue swelling and a mineralized ossicle in one intervertebral space that may have caused discomfort. Administration of analgesics led to complete resolution of the behavior. Self‐mutilation has been documented in several other species secondary to nerve injury, pain, and altered sensation, so self‐mutilation behaviors should always lead to a thorough physical exam and imaging, if possible, to rule out underlying medical causes. Empirical treatment with analgesics or anti‐inflammatories may be warranted in some patients before determining that self‐mutilation is a primary behavioral problem. Box 4.5 lists some of the most important medical rule‐outs for common repetitive behaviors (often referred to as compulsive disorders) in dogs and cats.
4.6.6 Endocrine Disease
Endocrine imbalances have the potential to change many aspects of an animal’s behavior because they usually result in altered motivation for meeting particular bodily needs (see Table 4.3). For example, an animal with diabetes mellitus will demonstrate increased thirst and hunger. The subsequent drive to acquire more food or water can lead to unusual behaviors such as attempting to drink water left on the floor during cleaning procedures.
4.6.6.1 Dogs
Hypothyroidism is one of the endocrinopathies most often mentioned as being associated with behavioral changes in dogs. However, there are minimal data supporting any causal association between hypothyroidism and aggression. One study compared the analytes commonly used to evaluate thyroid function between dogs with and without aggression toward people and found no difference between the two groups (Radosta et al. 2012). A double‐blind placebo‐controlled trial evaluated the effect of six weeks of thyroid replacement on owner‐directed aggression in 29 normal dogs with borderline low thyroid values and found no difference between the treatment and control groups (Dodman et al. 2013). In another study of 20 hypothyroid dogs without diagnosed behavior problems, treatment with levothyroxine resulted in no behavioral change other than increased activity levels (Hrovat et al. 2018). Serotonin and prolactin levels were also measured prior to, at six weeks, and six months after the initiation of levothyroxine therapy, and no significant changes in levels were noted (Hrovat et al. 2018). Thus, at this time, there are no data to support the proposal that thyroid supplementation may benefit behavioral therapy in dogs.
4.6.6.2 Cats
Hypothyroidism rarely occurs naturally in cats but is a common sequela to treatment for hyperthyroidism. Clinical signs are similar to those seen in dogs with hypothyroidism. Congenital hypothyroidism, while also rare, has been well documented in cats, as it is the most common cause of disproportional dwarfism (Jones et al. 1992). While the physical changes associated with congenital hypothyroidism are numerous, mental dullness and lethargy are the most commonly mentioned behavioral changes.
Box 4.5 Medical Conditions That May Result in Repetitive Behaviors
Tail chasing
Intervertebral disc disease
Injury of the tail
Anal sac disease
Spinal cord disease including neoplasia
Cauda equina syndrome
Focal seizures
Flea allergy
Fly snapping
Viral diseases such as distemper
Tick‐borne diseases such as Lyme, ehrlichiosis, and Rocky Mountain spotted fever
Focal seizures
Central nervous system neoplastic disease
Gastroesophageal reflux
Lymphocytic, eosinophilic, or plasmacytic enteritis
Delayed gastric emptying
Chiari malformation
Chorioretinitis or other ocular abnormalities
Acral lick dermatitis
Allergic dermatitis
Peripheral neuropathy
Orthopedic disease or arthropathy
Osteosarcoma or other neoplasia
Foreign body (retained pin, grass awns)
Infection: bacterial, fungal, or parasitic
Trauma (laceration)
Endocrinopathies
Pica
Pyruvate kinase deficiency and other blood abnormalities
Feline infectious peritonitis
Lead poisoning
Portosystemic shunts and other forms of liver disease
Gastrointestinal infections (Campylobacter, Clostridium)
Ehrlichia
Iron‐deficiency anemia
Psychogenic alopecia in cats
Allergies including atopy, food‐based and hypersensitivity reactions
Bacterial, fungal, or parasitic skin infections
Hyperthyroidism
Pain (from multiple causes and multiple sources)
Table 4.3 Endocrinological disorders that may lead to behavioral changes.
| Conditions | Possible behavioral changes |
|---|---|
| Dogs | |
|
Hyperadrenocorticism
| |
