Stress is a widely used term that broadly refers to complex cognitive, emotional and physical responses to stimuli (both pleasant and aversive). Unfortunately, stress is commonly experienced by feline patients, leading to a host of problems. Stress confounds and complicates diseases and even contributes to the occurrence of some diseases. Stress changes the behavior of cats, often making them challenging as patients and as pets.
The stress response is diverse but there are common pathways that become stimulated and lead to physiologic and behavioral changes. The sympathoadrenal system releases epinephrine and norepinephrine, the catecholamines responsible for the classic "fight, flight, or freeze" responses. These hormones cause an increase in heart rate and cardiac output, an increase in respiratory rate, and peripheral vasoconstriction to move blood from less important organ systems. Epinephrine stimulates glycolysis, gluconeogenesis, and lipolysis - all necessary to supply energy for fleeing or defending oneself. The hypothalamic-pituitary-adrenal response stimulates various changes, some of which have catabolic and immunosuppressive effects.
Understanding Cats
Understanding stress in the feline context requires an understanding of the natural biology of this species. It is often said that "cats are not small dogs," and nor are they people. Their position in the natural world, their social organization, and their life style is unique. They are often misunderstood, even by "experienced" cat owners.
Our efforts to keep cats entirely or mostly as indoor pets have been well intentioned. We are trying to protect this family member from disease and trauma. However, this shift to a small indoor environment is a radical one for the cat. The skill set of cats was developed in a different context and confinement indoors limits their ability to display normal behaviors and so may be stressful. We have also taken this highly intelligent and competent animal and removed its need to "work." House cats are typically sterilized so they cannot reproduce, have a very small territory to patrol, and no need to hunt. What can they do all day? Boredom is itself a form of stress. This is why environmental enrichment has become a well-recognized component of treatment for some diseases and for behavior problems.
The highly territorial nature of cats becomes a problem when the cat is removed from its home range (e.g., a trip to the veterinary clinic or a boarding facility). Any number of things may make a cat feel territorially threatened, such as a neighborhood cat seen from a window, a new pet in the home, changes to the home, etc. A common response of cats to stress is to hide - most cats would rather flee than fight. Indoor environments, including veterinary clinics, often neglect to provide enough hiding and perching areas for cats.
Physiologic Effects of Stress
Undesirable physical effects of stress can be seen in feline patients, making interpretation of their true health status difficult. These changes confound our clinical evaluation and treatment, and may prolong hospitalization. Changes include increased blood pressure ("white coat" hypertension), increased heart rate, cardiac murmurs (via catecholamine induced dynamic narrowing of the right ventricular outflow tract), and increased respiratory rate. Chronic stress, whether intermittent or constant, makes animals more prone to infection and more susceptible to certain diseases. In addition, stressed cats may have erratic responses to sedation and anesthesia. Certain physiologic changes in response to stress can complicate interpretation of laboratory data. These include decreased serum potassium, increased serum creatinine phosphokinase, stress hyperglycemia, stress leukogram, and transient alkaline urine.
Stress also plays a role in causing or contributing to certain diseases and problem in cats such as
Upper respiratory tract disease and associated anorexia and weight loss in shelter cats
Idiopathic cystitis
Behavior problems: inappropriate elimination, overgrooming, aggression
Effects of Stress on Veterinary Care and Hospitalization
Cats seldom leave their home environment or home range willingly so that being forced into a strange environment makes a cat uncertain about its safety and may cause anxiety and distress. Many things in veterinary clinics can induce stress and fear in cats, such as the presence of unfamiliar people, other animals, noises (e.g., medical equipment, telephones, dogs barking, etc.), odors (e.g., other animals, disinfectants), and unfamiliar food and feeding routines. Cats prefer to avoid danger and confrontation by running away or hiding, strategies that are not easy to employ during veterinary visits. Hospitalized patients may not be able to express normal behaviors (e.g., resting, feeding) and will suffer from increased vigilance and dysfunctional signs such as anorexia, vomiting, diarrhea, or even lack of elimination.
Veterinary hospitals should have procedures in place for monitoring of food intake, body weight (BW), and body condition scores (BCS) of hospitalized cats, as well as guidelines for intervention. Cats should be weighed and body condition scored at admission; this should be repeated regularly during the hospital stay. More frequent evaluation is indicated for sick cats and those on medications (many drugs cause hyporexia/anorexia or vomiting in cats).
Use of feline facial pheromone (FFP) was shown to be beneficial for hospitalized cats in two studies. In one study, FFP had an additional calming effect on cats receiving premedication. In another study, using FFP in cages was associated with increases in grooming behaviour, increased food intake, more lying and sitting behaviour, and less sleeping. Placing a cat carrier in the cage to provide a hiding or perching spot produced further benefits in food intake.
References
1. Buffington CAT. What cat owners can learn about captivity. Clinician's Brief. 2011;9:55–58.
2. Carney HC, Little S, Brownlee-Tomasso D, et al. AAFP and ISFM feline-friendly nursing care guidelines. J Feline Med Surg. 2012;14:337–349. www.catvets.com/guidelines/practice-guidelines/nursing-care-guidelines.
3. Chan DL. The inappetent hospitalised cat: clinical approach to maximising nutritional support. J Feline Med Surg. 2009;11:925–933.
4. Ellis SLH, Rodan I, Carney HC, et al. AAFP and ISFM feline environmental needs guidelines. J Feline Med Surg. 2013;15:219–230. www.catvets.com/guidelines/practice-guidelines/environmental-needs-guidelines.
5. Rodan I, Sundahl E, Carney H, et al. AAFP and ISFM feline-friendly handling guidelines. J Feline Med Surg. 2011;13:364–375. www.catvets.com/guidelines/practice-guidelines/handling-guidelines.