September 2007
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• New research on feline heartworm disease
• Cat eyes
• September is Senior Pet Health month

Feline Heartworm Disease
Recent research done at Auburn University has shown conclusively that heartworms do not need to grow to maturity to cause pathology in cats.  This research has shown feline heartworm disease to be more insidious than previously thought.  It also emphasizes the importance of preventing heartworm disease in cats.  Outdoor cats are more likely to contract heartworm disease due to their increased contact with the mosquito, however it is believed that as many as 25% of heartworm infected cats never leave the house. 
Cats get heartworm disease the same way dogs get it, but the disease is very different between the two species.  It is transmitted through the bite of a mosquito carrying the L3 stage of the heartworm larvae.  The most common signs of heartworm disease in cats – coughing, breathing difficulties, vomiting, lethargy, and weight loss – are often mistaken for other conditions such as asthma and digestive problems.  Most heartworm-infected cats exhibit signs that very closely resemble bronchial asthma.  Some cats show no symptoms and the diagnosis of heartworm disease is made after a sudden death.  Diagnosis of heartworm disease in dogs involves a simple blood test only.  Diagnosis in cats is difficult and involves physical examination, blood tests, x-rays, and cardiac ultrasound.  Treatment options in cats are very limited.  Heartworm-infected cats that are not demonstrating clinical signs are allowed time for their immune system to clear the infection.  Chest x-rays are generally taken every 6 months during this “treatment”.  Cats with more severe symptoms of heartworm disease may need supportive therapy while their body clears itself of the heartworm.  This therapy may include IV fluids, cage confinement, oxygen therapy, bronchial dilators, cardiovascular medications, and antibiotics.  Occasionally, infected cats die quickly without time to make a diagnosis or offer treatment options.
Since heartworm is definitely a problem in central Ohio, we highly recommend use of heartworm prevention in your cat(s).  We suggest either Heartgard© Chewables for Cats, a once-monthly oral medication, or Revolution© Feline, a once-monthly topical medication.  Speak with your veterinarian regarding heartworm preventive medications at your next visit.

Cat Eyes
Have you ever wondered about the shape of your cat’s eyes?  The shape is unique to the feline species and is meant to maximize vision in low light.  Cats can see at eight times dimmer illumination than humans.  Your pet cat’s ancestors hunted from dusk to dawn thus the need for good night vision. Scientists have found that the elliptical-shaped pupil can open larger and more quickly than a circular pupil.  The elliptical pupil allows more light into the back of the eye. 
A cat’s retina is also different from humans.  There are two types of photoreceptor cells in the retina: rods and cones.  Cones respond to a wide range of light wavelengths which allow color vision, however they require a large amount of light.  Rods on the other hand are very sensitive to light but only allow a narrow range of wavelengths.  A cat’s retina has mostly rods so they can see very well in low light but can only see a limited range of colors.
Light reflection is another unique characteristic of a cat’s eye.  This is due to a specialized reflecting layer behind the retina.  When light passes through the pupil not every light photon strikes a photoreceptor.  The photons that fail to interact with a rod or cone are “recycled”.  The reflecting layer behind the retina allows these photons to be reflected back giving them a second chance to interact with a photoreceptor.
Your cat comes from a long line of nocturnal carnivores whose physical adaptations like the elliptical pupil increased their chances of survival.

September is Senior Pet Health Care Month
Thanks to advances in animal nutrition and veterinary medicine, the life expectancy of our pets continues to rise.  Our goal with senior pet care is to help the pet owner differentiate the normal changes that occur in the aged pet and the age-related conditions that would benefit from veterinary care.  The goal is to keep your pet comfortable throughout the senior years.  It is important to realize that aging is not a disease process.  Don’t assume that a physical or behavioral change is due simply to aging.  While there are age-related health problems, age itself is not a disease.
What changes might you expect to see in your senior pet?

• Sensory loss
• Stiffness
• Weight changes
• Cognitive dysfunction (senility or Alzheimer’s-like symptoms)
• A decrease in normal organ function

Should you bring your pet to the veterinarian for these signs?  What can you do to reduce the affects of these conditions?  Let’s look at each individually. 

• Decreasing vision, hearing, and scent detection often affects older pets.  Senior dogs and cats may sleep through an event that normally would have their undivided attention.  They may be startled by things that wouldn’t have bothered them before and a startled animal can sometimes respond inappropriately.  Biting, scratching, urinating, and emptying of the anal glands are common responses.  Learn to approach your sensory-challenged pet cautiously.  Creating a vibration by stomping on the floor or simply a gentle touch will let them know that you are close by.  Increased vocalizations or a change in the sound of their vocalizations can also occur in animals with sensory loss.  While there may not be much your veterinarian can do to reverse age-related hearing and vision loss, be sure to let the doctor know what you’re seeing.  There are several disease processes that your pet can be screened for that may be causing the sensory loss symptoms.
• Cartilage in the joints deteriorates with age.  Bones get brittle and joint tissues lose moisture.  Generally, these arthritic changes occur very gradually and create chronic pain.  Because the changes are so gradual it is often difficult for the pet owner to recognize.  Arthritis is most common in the hip joints in our pets, but it can occur in any joint.  There are nutritional supplements and pain control medications specifically formulated for animals that have given relief to millions of senior pets.  A few changes around the house may help also.  Adding a ramp or a couple of steps near the bed or couch, placing a litter box on every level of the house, elevating the food and water bowls; all these can help the arthritic patient.  See your veterinarian for medications that can ease your pet’s painful arthritis.
• Weight loss in senior dogs and cats might just be due to old age but is more likely due to a disease process.  Don’t allow weight loss to continue for long before consulting with your veterinarian. 

Conversely, while there are some disease processes that can cause weight gain, it is more likely to be associated with the less active lifestyle of the older pet.  Maintaining a healthy weight will help the older pet live longer and remain active.  See your veterinarian if your senior pet’s weight is increasing.

• Cognitive dysfunction syndrome (CDS) is caused by physical and chemical changes that affect brain function.  Signs may include aimless wandering, disrupted sleep cycles, confusion, impaired mental function, and/or inappropriate elimination.  Your veterinarian has diets, medications, and nutritional supplements that can help manage CDS in senior pets.
• Pets age much more rapidly than humans.  A 10 year old cat is equivalent to a 63 year old person and a 10 year old dog would be 56-78 (large breed dogs age faster than small breed dogs do).  Just as people over the age of 50 have more health concerns, many disease processes are more common in the older pet.  Their internal organs just aren’t functioning as well. 
• Kidney disease (renal insufficiency or renal failure) signs include increased thirst/urination, dehydration, weight loss, vomiting, anemia, and poor hair coat. 
• Diabetes signs can be very similar to kidney disease with weight loss, increased thirst, and increased urination. 
• An insatiable appetite with weight loss could indicate hyperthyroidism (usually seen in cats – rarely in dogs).  These patients may also be hyperactive. 
• Decreased energy levels and weight gain could be due to hypothyroidism (usually seen in dogs - rarely in cats).
• Heart disease can remain hidden for many years.  Symptoms may include decreased energy levels, exercise intolerance, weight loss, and fluid retention.
• Cancer is much more common in the elderly patient.  Symptoms of cancer may include weight loss, loss of appetite, pain, lameness, lumps or swelling, and difficulty eating, breathing, defecating, or urinating.

As you can see, many of these symptoms are repeated in several disease processes.  A visit to your veterinarian for a complete physical examination and a senior workup (which may include bloodwork, urine tests, ECG, blood pressure measurement, and an x-ray) will help detect changes that can indicate early signs of disease.  Early detection and early treatment can provide a better quality of life for your senior pet.

Try to maintain a routine in the life of your senior pet.  Changes can be very stressful.  Keep the surroundings familiar and encourage moderate exercise.  Be sure to provide regular grooming.  Self-grooming generally decreases in the senior cat.  Grooming sessions also give you a chance to check for lumps or lesions that you may not have noticed.  Provide cushioned beds in a warm and draft-free area and don’t leave your senior pet out for long periods in cold or hot weather.  Observe your older pet closely for changes in behavior or any signs of discomfort. 

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