Saturday, April 15, 2017

Fleas and Flea Control in Cats

Summer is over, and a lot of cats are rejoicing. It may be a fun season for people, but it can be miserable for cats, because warm and humid weather is paradise for fleas.  Few creatures living on Earth today have had as much impact on world history as the common flea.  From the black plague during the 14th century to the present, fleas have been the cause of much grief. 

            To better understand how fleas torment cats and humans, and how best to combat them, it is important to understand the life cycle of the flea.  Once a flea jumps on a cat, it stays there for its entire life.  Contrary to popular belief, fleas do not jump from one cat to another. Although the flea spends its entire life on the cat, the majority of the flea’s life cycle occurs while off the cat.  When a female flea hops on a cat, it begins feeding on blood within minutes.  Ingestion of blood is required for the flea to be fertile and reproduce.  Approximately 24 hours later, the flea begins to lay eggs, about 40-50 per day.  As the cat moves around the house, it acts like a living salt-shaker, disbursing the flea eggs in the environment, mainly in the areas where the cat sleeps or rests.  Within a week, larvae hatch from flea eggs. The larvae try to avoid light and burrow into carpets, cracks in hardwood floors, and other humid areas such as concrete floors in damp basements.  Five to twelve days after that, larvae spin a cocoon in which they develop into pupae. One to three weeks later, baby fleas emerge from pupae.  These newly hatched fleas wait for the cat to pass by, and then they hop on, and the life cycle starts all over again. The entire flea life cycle takes 3 to 6 weeks.  If you were to assess all of the life stages of the flea as a population, adult fleas comprise only about 5 per cent.  Eggs make up 50% of the population, with larvae at 35% and pupae at 10%.  In other words, if you’re seeing adult fleas on your cat, you can be sure that there is a veritable flea factory looming nearby. Even if a cat spends its entire life indoors, it is not immune from these pesky critters.  Fleas are hitchhikers – they jump onto your clothing, and you bring them back home, where they hop onto your unsuspecting cat.

            At best, fleas can make your cat itchy and uncomfortable.  At worst, they can transmit dangerous diseases.  While dogs usually bite or scratch at fleas, cats use their barbed tongues to remove them, often abrading the skin in the process. The most prevalent skin disorder in small animals is flea allergic dermatitis (FAD). This is more than just a mechanical irritation from the flea.  When fleas bite the cat, they deposit their saliva into the skin before ingesting blood.  Proteins in the flea saliva can induce a hypersensitivity reaction in some cats.  This allergic reaction causes severe itching, and cats often develop small crusty papules and hair loss on their neck and face, and most notably down their back, in the classic “racing stripe” pattern.

            Fleas are responsible for transmitting tapeworms to cats. Heavily parasitized cats, especially kittens, can develop anemia due to blood loss from flea bites.  Fleas also transmit Bartonella, the organism responsible for cat-scratch disease in humans.  Most cases of cat-scratch disease are self-limiting, however, Bartonella infections can cause very serious illnesses in people with immune deficiency disorders. Fleas can also pass Bartonella from one cat to another.  Most cats infected with Bartonella are clinically normal, however, infection in cats can sometimes lead to fever, lethargy, lymph node enlargement, eye inflammation, and other disorders in cats.                
            Because some of the infectious agents transmitted by fleas may affect humans, the American Association of Feline Practitioners recommends year-round flea control.  Historically, the most effective approach was the three-step method:  treatment of the yard, home, and cat.  The newer flea and tick control products, however, are so effective that treatment of the premises is rarely necessary, especially if the cat resides totally indoors.

            Fleas sprays, flea dips, and flea shampoos have become obsolete.  Flea control is now achieved through the use of products that are either given orally or topically once a month.  Some of these products are effective not only against fleas, but other parasites as well, including ticks, heartworms, ear mites, hookworms, and roundworms. 

            A variety of flea control products are available to cat owners. Common products include those that contain either imidacloprid (Advantage), fipronil (Frontline), dinotefuran (Vectra), spinetoram (Cheristin) or selamectin (Revolution).  These products are applied to the skin on the back of the neck.  They  sink into, and then spread through, the layer of fat beneath the skin, killing any adult fleas that are present on the cat.  The advantage of these products is their residual activity; they continue to kill fleas for at least thirty days.  After 30 days, a new dose is applied.  These products are very safe, and very effective.   Oral flea control products are also available. Nitenpyram (Capstar) is an oral medication that is good for heavy flea infestation.  A single oral dose of nitenpyram will kill all of the adult fleas on a cat. It starts to work within 30 minutes of administration.  Nitempyram has no residual effect, so if the cat gets re-infested with fleas, an additional dose may be required.  It can be given safely as often as every day.  Nitenpyram can be used together with other flea products.  Spinosad (Comfortis) is an oral formulation that kills 100% of adult fleas on a cat by 24 hours after administration.  Spinosad has residual effect; it continues to kill adult fleas for 30 days before the next oral dose is required. Lufenuron (Program) is an insect growth regulator – a product that works by interfering with the growth and development of fleas, but has no effect on adult fleas.  It is given orally once a month, however, an injectable form is available that is effective for six months.  When a female flea ingests blood from a cat treated with lufenuron, the eggs she produces will be infertile.  Because lufenuron does not kill adult fleas, it is better suited to prevent a continual flea problem.  It does not stop a flea from biting, so it is not ideal for cats with flea allergic dermatitis.  If quicker results are needed, a product that kills adult fleas should be used.

            For cat owners who prefer to use flea collars, there is a collar (Seresto) that contains a sustained release formulation of the flea-killing compound imidacloprid, in combination with flumethrin, which kills ticks.  The collar kills fleas and ticks for 8 months, reducing the need for monthly application of topical products. The collar also has a “break-away” mechanism, so if it gets caught on something, it will release, rather than cause injury to the cat. 

            Cat owners should be aware that in an effort to tap into the lucrative flea-control market, some manufacturers have produced flea control products with packaging similar to the veterinary products, i.e. in small, single dose tubes for topical application.  These products contain permethrin, an insecticide commonly found in low concentrations in a variety of canine and feline flea sprays and shampoos.  In low concentrations, cats tolerate these products with minimal adverse effects.  These small single-dose tubes, however, contain concentrated permethrin (45% to 65%) as the active ingredient.  Concentrated permethrin spot-on products are labeled for use in dogs only, and may cause severe and often fatal toxicosis if applied to cats. 

            Fleas have been a source of much misery for pet cats and dogs. They can transmit diseases to cats, as well as to humans.  Fortunately, modern flea control products can provide an amazing level of efficacy. Understanding the flea life cycle is critical in formulating a comprehensive flea-and-tick control strategy.  Talk to your veterinarian about which products are right for you, as different products offer different benefits.  Be aware, however, that improper use of these products can result in treatment failure, and use of unsuitable or mislabeled products can have dire health consequences.

Monday, April 3, 2017

Body Parts - The Feline Brain

Body Parts – The Brain

            The brain is the main organ that comprises the central nervous system of the cat.  It is the control center for receiving and interpreting information that comes from the cat’s own body, and from the outside world.  Learning and perception takes place in the brain, and all of the sensations – sight, sound, smell, taste, touch, and pain – are processed through here. I’ve been a veterinarian for over 28 years, and despite examining and treating thousands of cats, I’ve come to accept one thing for certain: I will never truly understand the feline brain.  (I do enjoy trying, though.)

            The brain is a lump of spongy pink nerve tissue located within the skull. It can be divided into three major parts: the cerebrum, the cerebellum, and the brainstem.  The cerebrum makes up the majority of the brain tissue. It can be divided into two major portions: the right cerebral hemisphere, and the left cerebral hemisphere.  The hemispheres are connected to each other by a piece of tissue called the corpus callosum, which allows messages to be transported from one side to the other.  The cerebellum is found at the back of the brain, attached to the cerebrum.  It is responsible for physical coordination, balance, and posture.  The brainstem is located at the base of the brain. It regulates important functions such as blood pressure, breathing, and heartbeat.  The brain is covered with several membranes, called meninges.  A fluid, called cerebrospinal fluid, is found beneath the meninges, bathing the brain and protecting it from injury.

            Like any other organ, the brain may become diseased or disordered.  The list of potential brain disorders is pretty long: infections, inflammations, hereditary disorders, metabolic disorders, toxic conditions, tumors, and trauma, to name a few.   A few of the more common ones I encounter as a feline practitioner include seizures, cerebellar hypoplasia, and brain tumors.

            Seizures occur when neurons in the brain begin to fire all at once, in an uncoordinated fashion. Seizures are seen less commonly in cats compared to dogs.  Seizures can be divided into primary seizure disorders and secondary seizure disorders.  Primary seizure disorders are those for which there is no underlying cause.  This is better known as epilepsy.  In dogs, there tends to be a genetic basis for epilepsy, but this doesn’t seem to be the case in cats.   Secondary seizure disorders are those for which there is a known cause.  The list of disorders that can cause seizures in cats is extensive, and includes infections (such as feline leukemia virus and toxoplasmosis), metabolic disorders (low blood sugar, low blood calcium, liver disease, thiamine deficiency), brain tumors, toxins (lead, antifreeze) and trauma.  In most cases of secondary seizures, if the cause is addressed, the seizures will resolve.  Cats with epilepsy may require anticonvulsant medication, depending on the frequency and severity of the seizures.  The most commonly prescribed anticonvulsant is phenobarbital.

            As noted above, the cerebellum is responsible for coordination and fine motor skills in the cat.   Cerebellar hypoplasia is a condition in which a kitten is born with an underdeveloped cerebellum at birth.  The most common reason for this is an infection with the feline panleukopenia virus while the mother is pregnant.  Affected kittens will have mobility issues as a result.  The severity of the condition varies from cat to cat, even among littermates.  Some cats are mildly affected, while others really have difficulty getting from point A to point B.  These cats may also have head tremors, sometimes called “intention tremors” because they’re more pronounced when the cat is deliberately intending to do something with its head, like eat or drink.  Although cats with cerebellar hypoplasia may look like they’re struggling, we should bear in mind that these cats have no idea that they’re any different from other cats.  Because they were born this way, they think they’re normal.  The condition is not painful, and it is not progressive – it won’t get worse over time.  There is no treatment for cerebellar hypoplasia, and there really is no need for one.  What these cats lack in mobility, they make up in personality. 

            Sadly, just like any other organ, the brain is also susceptible to cancer.  Brain tumors may be classified as primary or secondary.  Primary brain tumors are those that arise from cells found within the brain or the membranes surrounding the brain.  Secondary brain tumors are those that have metastasized (spread) to the brain as a result of a primary tumor elsewhere in the body.  The clinical signs of a brain tumor can vary and include abnormal mental status or behavior such as stupor, head-pressing (the cat relentlessly presses its head against a wall or other surface), walking in circles, or seizuring.

The three main treatment options for brain tumors are surgery, radiation, and chemotherapy.  Surgical removal of the tumor is rarely attempted, although meningiomas (tumors arising from the membranes that cover the brain) are sometimes surgically amenable.  The goal of chemotherapy and/or radiation is to reduce the size of the tumor and control the symptoms.  The prognosis for cats with brain tumors is poor.


Wednesday, March 22, 2017

Ascites (abdominal effusion) in Cats


Accumulation of fluid in the abdomen is an important sign of illness in cats

            Ascites (pronounced “a-site-eez”) is the accumulation of fluid in the abdominal cavity.  It is a sign of disease, rather than a diagnosis.  Unfortunately, there are very few benign causes of ascites. 

            Because there are so many possible causes of ascites, the historical findings vary in each individual case.  For example, a cat with ascites and a history of trauma (falling from a height, or hit by a car) could have internal bleeding, the fluid in the abdomen being blood, or a ruptured bladder, the fluid being urine.  Cats with labored breathing and exercise intolerance could be suffering from heart disease, another potential cause of abdominal fluid accumulation.  It is therefore important to get an accurate history from the cat owner as to the cat’s appetite, behavior, travel history, potential for trauma, etc.

            Cats with ascites are usually presented to the veterinarian with a complaint of abdominal distention.  However, there are other causes for a big belly in cats besides fluid accumulation, for example, abdominal tumors, enlarged organs such as a big liver or a big spleen, or an enlarged bladder due to a urinary obstruction.  The physical examination may yield other clues as to the cause of the ascites.  Cats with a heart murmur and weak pulses may have heart failure as the cause of their ascites.  Cats with peripheral edema (swelling of the limbs) may indicate that a low protein level in the bloodstream, another cause of fluid accumulation.   Some cats don’t seem to be bothered by ascites, while others are clearly uncomfortable.  Much depends on the volume of fluid that has accumulated.  Large amounts of fluid can put pressure on the diaphragm, limiting the expansion of the lungs and making it difficult to breathe.

            Determining the cause of the ascites requires various diagnostic tests.  X-rays of the abdomen are not very useful because the presence of fluid obscures the details of the other abdominal organs.  Abdominal ultrasound, however, allows for confirmation of the presence of fluid, and allows the veterinarian to evaluate the other abdominal organs, e.g. the liver, spleen and pancreas for potential causes of ascites.

            Analysis of the abdominal fluid can be very helpful in determining a cause for the ascites.  A fluid sample can be obtained by inserting a 20 or 22-gauge needle into the abdomen and withdrawing a sample with a syringe.  This technique is more successful when there’s a large volume of fluid present.  If there’s only a small volume of fluid present, ultrasound may help localize the fluid, allowing for successful sampling.  Most cats with ascites do not require complete removal of all fluid.  In some patients, the increase in pressure inside the abdomen from the fluid build-up actually prevents further accumulation, and if a lot of fluid is removed, it may re-form rapidly.  This can lead to a rapid decrease in the blood volume, leading to cardiovascular collapse and shock.  If the amount of fluid present is causing respiratory difficulty, enough fluid should be removed so that breathing is no longer compromised.  Fluid samples should be sent to a clinical pathologist for evaluation.

            If the underlying cause of the fluid can be identified and corrected, the fluid may be partially reabsorbed back into the bloodstream.  In cases of hemorrhage, as many as 50% the red blood cells can go back into the circulation. 

            Clinical pathologists often classify the fluid into one of three major categories: exudate, transudate, or modified transudate, based on the amount of protein and cells in the fluid.  Most samples end up being modified transudates, however, there is a lot of overlap between categories, and most practitioners don’t fine this classification very useful.  A more practical classification attributes the ascites to one of 7 disease categories:  cardiac, cancer, liver, kidney, urinary tract trauma, feline infectious peritonitis (FIP), and peritonitis (inflammation of the lining of the abdomen).

            Heart disease isn’t a major cause of ascites in cats, compared to dogs.  Prior to 1987, heart disease was a significant cause of ascites in cats, mainly due to the disease dilated cardiomyopathy (DCM), which was fairly prevalent.  Once it was discovered that a deficiency in the amino acid taurine was the primary cause of feline DCM, pet food manufacturers corrected the deficiency in the food and the incidence of DCM dropped dramatically. 

            Sadly, cancer is a common cause of abdominal effusion in cats, and is more common as cats get older.  In most cases, the initial tumor is a carcinoma, typically involving the gastrointestinal tract or pancreas.  The tumor metastasizes throughout the entire abdomen, a condition called carcinomatosis, and this often leads to ascites. 

            Feline infectious peritonitis (FIP) is a terrible viral disease that commonly causes abdominal fluid accumulation.  Any age cat is susceptible, although young cats are more commonly affected.  Unfortunately, FIP is not treatable and cats invariably succumb to the disorder. 

            Severe liver disease may cause ascites in cats.  The liver produces albumin, a protein that is important in helping maintain fluid within the circulation.  If the liver is very diseased, it may produce inadequate amounts of albumin, resulting in hypoproteinemia, a reduced level of protein in the blood.  This can lead to ascites.

            Pancreatitis is a common cause of ascites in cats.  In acute, severe cases of pancreatitis, fluid leaks through the vessels within the inflamed pancreas, into the abdominal cavity.  Pancreatitis used to be difficult to diagnose in cats, however, better ultrasound equipment and the development of a blood test called the fPLI test has made pancreatitis less difficult to diagnose. 

            Unfortunately, the disorders that cause ascites in cats tend to be bad, and the prognosis is usually guarded or poor.  Cat owners who think their cat might have a distended or enlarging abdomen should seek veterinary advice immediately, as early detection and prompt diagnosis may lead to a better outcome. 

Possible causes for ascites

Trauma and internal bleeding
Blood clotting disorder
Bleeding tumor
Urinary tract rupture
Feline infectious peritonitis
Heart disease
Liver failure

Hypoproteinemia (low serum blood protein)

Wednesday, March 8, 2017

Feline Hyperparathyroidism

Feline Primary Hyperparathyroidism

The little parathyroid glands play a big role in calcium regulation. 

            When it comes to glandular problems in the cat, the thyroid gets all the glory.   Hyperthyroidism in the most common feline endocrine disorder, and every cat-centric publication regularly features articles about it.  Adjacent to the thyroid gland, however, are four small glands called the parathyroid glands.  These little glands are immensely important in finely regulating the blood calcium level.

            There are two pairs of parathyroid glands in the cat, the external and the internal parathyroids.  The external glands are located external to the capsule that surrounds the nearby thyroid gland.  The internal parathyroids are actually embedded within the thyroid gland. 

The parathyroid glands produce a hormone called, not surprisingly, parathyroid hormone (PTH).  This hormone is the principal hormone involved in the precise, minute-to-minute regulation of the blood calcium concentration.  The goal of the body is to maintain the blood calcium level within a narrow range.  The parathyroid glands are exquisitely sensitive to changes in the calcium level, especially when the calcium level drops.  When this happens, the parathyroids release PTH.  This causes several complicated things to happen:

·      PTH causes the bones to release calcium (and phosphorus) into the blood stream.
·      PTH causes the kidney to produce increased amounts of an enzyme that promotes production of a hormone called calcitriol.  Calcitriol causes the intestines to absorb more calcium (and phosphorus) from the diet.
·      PTH causes the kidneys to absorb more calcium from the urine, (and excrete all that extra phosphorus that came from the bones and the intestinal tract.)

            The end result is the restoration of a normal calcium level.  When the calcium level returns to normal, it signals to the parathyroids “mission accomplished”, and tells them to reduce PTH secretion.

            Sometimes, the parathyroid glands produce too much PTH.  This condition is called, as you might imagine, hyperparathyroidism. Hyperparathyroidism exists in two forms, primary and secondary.  Secondary hyperparathyroidism can be further divided into nutritional secondary hyperparathyroidism (pretty rare) and renal secondary hyperparathyroidism (rather common).  The focus of this article in on primary hyperparathyroidism, as the complex physiology behind secondary hyperparathyroidism is probably beyond the scope of the typical cat owner.

            Primary hyperparathyroidism occurs as a result of one of the parathyroid glands secreting excessive amounts of PTH on its own.  The cause of the excessive secretion is usually due to a benign tumor of one of the glands, called an adenoma, although in rare instances, the tumor is a malignant carcinoma.   Affected cats tend to be older, the age range in reported cases being somewhere between 8 and 15 years of age. Clinical signs tend to be non-specific and include lethargy, poor appetite, and vomiting.   Physical examination of the cat tends to be unremarkable, the only consistent finding is the detection of the enlarged parathyroid gland in the neck in about 50% of the cases.  Routine blood tests show an elevated calcium level.  Because PTH causes the kidneys to excrete phosphorus, some cats with primary hyperparathyroidism will have low serum phosphorus levels. In some cats, the elevated calcium levels results in the formation of calcium oxalate stones in the bladder, and some cats will have sign related to this, such as increased frequency of urination, straining to urinate, urinating in inappropriate places, and blood in the urine. 

            Definitive diagnosis if primary hyperparathyroidism requires measurement of the serum level of PTH along with measurement of serum ionized calcium (iCa). Ionized calcium provides a more accurate assessment of the calcium status.   If the PTH level and the iCa level are both high, the diagnosis is obvious.  If the iCa is high and the PTH is in the upper half of the reference range, the cat probably still has hyperparathyroidism because when the calcium level is high, the proper response of the parathyroid gland is to shut down production of PTH.  A PTH level in the upper half of the reference range in the face of an elevated calcium is an inappropriate response and suggests that the parathyroid gland has gone haywire and is secreting the hormone autonomously.  A diagnosis is trickier when the iCa is high and the PTH level is in the lower half of the reference range.  There’s no real consensus on what is an appropriately low PTH level in the face of an elevated iCa.  Certainly, if the iCa is high and the PTH level is undetectable, then hyperparathyroidism is probably not the cause of the high calcium.  But a low normal PTH level in the face of high iCa is a diagnostic dilemma.  Ultrasound of the thyroid region of the neck may reveal a single enlarged parathyroid gland, which would be highly supportive of the diagnosis.  Not finding an enlarged gland, however, doesn’t rule it out. 
            The most commonly recommended treatment of primary hyperparathyroidism is parathyroidectomy – surgical removal of the abnormal gland.  Ultrasound of the neck helps identify the exact location of the tumor, i.e. whether it is one of the external parathyroids or the internal parathyroids.  This allows for proper pre-surgical planning.   Anesthetic complications related to elevated calcium levels include abnormally slow heart rate, high blood pressure, and cardiac arrhythmias, so careful anesthetic planning is a must.  At surgery, one large parathyroid gland is usually found.  As a result of that one gland producing such high amounts of PTH, the other three glands have shut off production of PTH completely, causing them to atrophy and making them impossible to identify.  A tumor of one of the external parathyroid glands is usually easy to identify (unless it is embedded in fat, making the identification a bit trickier).  Parathyroid tumors involving one of the internal parathyroids are harder for the surgeon to identify.  If an internal parathyroid is affected, removal of that entire lobe of the thyroid gland is required.  In dogs, a method of treatment called chemical ablation that involves the injection of ethanol into the abnormal gland has been described, however, studies of the effectiveness of this method of treatment in cats are lacking.

            Post-operative complications occur occasionally, the most common being, ironically, a low calcium level.  (This is a bigger problem in dogs than in cats.) As mentioned above, excessive production of PTH by a tumor in one parathyroid gland results in atrophy of the remaining parathyroid glands.  Removal of the offending gland will cause a rapid drop in blood PTH levels.  It takes a while (typically two to three weeks) before the remaining parathyroid glands “wake up” and start producing PTH again.  Until that happens, it is essential that the cat be monitored for clinical signs of hypocalcemia (low calcium).  Cats that experience low calcium post-operatively can be treated with a combination of calcium supplements and vitamin D. The supplementation can be tapered over a few weeks as the remaining parathyroid glands begin to function normally. 

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