Stomach Tacking

I have seen a few Great Danes come through the office lately, so I thought I would discuss stomach tacking (gastropexy).  Large breed dogs with deep chests (Great Danes, Irish Setters, Saint Bernands, etc) have a lot more room in the front part of their abdomen that allows for more movement in the stomach and ultimately makes them prone to gastric dilatation and volvulus (GDV or bloat).  

The exact cause of GDV is unknown, but many things can predispose to the condition including

1.) rapid eating

2.) eating one large meal daily

3.) overeating and overdrinking

4.) heavy exercise after eating

5.) conformation of the dog

A dog who has GDV will typically be anxious, may be drooling, have a distended abdomen, and are retching without producing anything.  The condition quickly becomes an emergency as the twisting of the stomach compromises blood return to the heart leading to shock.  The treatment involves immediate treatment of the shock (with fluids and pain medications) and then de-rotating the stomach.  Measures can be taken without surgery including passing a tube to deflate the stomach or passing a needle into the stomach through the body wall, but in most cases surgery will eventually be needed.  Even with surgery it is not guaranteed that the pet will pull through because if blood flow is compromised long enough you may get tissues that die and become infected.

X-ray image of stomach with GDV

The surgery involves deflating the stomach, placing the stomach back into normal anatomical position, and then permanently tacking the stomach to the body wall (which prevents recurrence of GDV).  There are many different procedures to tack the stomach; however, I typically perform a simple incisional gastropexy.  This involves making an incision into the outer portions of the stomach and then making a corresponding incision into the body wall.  The incision is then sutured together using two parallel lines of suture material.  The suture material will initially hold the stomach and body wall together, but eventually scar tissue will form and permanently hold the surgery site together.  If caught early enough, many dogs can do well; however some dogs may need more aggressive surgery (removal of a portion of the stomach, accompanying splenectomy) if the condition goes on long enough.

Tacking stomach to body wall

Because of deep chested breeds risk for GDV later in life, some owners may consider performing a preventative gastropexy.  This involves performing the gastropexy before a GDV occurs (typically done during a spay or neuter procedure).  There are some minimally-invasive techniques involving laproscopy, but not all veterinarians can perform these and the cost will likely be more.  A conversation about this procedure with your veterinarian should be made when the puppy is young, so a plan can be made for performing the gastropexy.

Kidney Disease

What are the functions of the kidneys?

The kidneys play a vital role in the body, participating in a number of processes including removing waste products from the body, regulating water balance in the body, regulating calcium and phosphorus levels, and producing certain hormones for the body.  Blood that passes into the kidney is filtered through thousands of small structures called nephrons where waste products are removed and excessive water is released. 

What is chronic kidney disease?

Chronic kidney disease (CKD) is not a singular disease, but more a catch all term for kidneys that are not functioning at full capacity.  The underlying cause for this could include a number of different conditions including:

• Congenital malformation of the kidneys
• Chronic bacterial infection of the kidney (pyelonephritis)
• High blood pressure (hypertension)
• Diseases of the immune system (i.e. Lupus)
• Recovery from acute kidney disease (toxin, infection, etc) leading to chronic disease

In many cases we do not figure out the exact cause of kidney insufficiency, but treat the end result.

Signs of chronic kidney disease:

Pets with chronic kidney disease can manifest many different clinical signs including:

• drinking too much (polydipsia) and urinating large volumes of urine (polyuria)
• vomiting and/or diarrhea
• lack of appetite and weight loss
• general depression related to the elevation of waste products in the blood (uremia)
• anemia resulting in pale gums and weakness due to a low blood count
• overall weakness from low blood potassium         

How is chronic kidney disease diagnosed?

If a pet is having clinical signs consistent with kidney disease, then some tests will be recommended to evaluate kidney function.  A combination of blood work and urine evaluation is used to give a good indication of kidney function.  Two blood values are of particular concern when evaluating kidney function (Creatinine and Blood Urea Nitrogen (BUN)).  Elevations in these values could indicate that the kidneys are not functioning well. 

If creatinine elevations are seen, then the urine is also evaluated.  In particular, we are looking at the concentration of the urine.  Normally, the kidneys try to maintain proper water balance in the body.  They do this by reabsorbing water and maintaining it in the body.  When the kidneys are functioning properly they will make more concentrated urine.  If the creatinine or BUN is elevated and there is dilute urine, then this indicates that the kidneys are not functioning properly and may have chronic kidney disease.  There is also a staging system (stage 1-4) to help indicate the degree of damage to the kidneys

STAGES	CLINICAL SIGNS	FASTED PLASMA CREATININE mg/dl (umol/l)assessed on at least 2 occasions in the stable patient		EVIDENCE FOR RENAL DISEASE
		DOG	CAT
I	Absent but patients should be substaged with urine protein creatinine ratio and blood pressure measurements	< 1.4 (<125)	< 1.6 (< 140)	Inadequate urine concentration, renal proteinuria, or abnormal renal architecture based on palpation, imaging, or histopathology
II	Usually mild or absent but substage as noted above	1.4-2.0 (125-179)	1.6-2.8 (140-249)	As for stage I
III	Usually present and may be related only to kidneys. Substage as noted above	2.1-5.0 (180-439)	2.9-5.0 (250-439)	As for stage I in addition to clinical signs
IV	Present, but may have extra-renal signs. Substage as noted above	>5.0 (>440)	>5.0 (>440)	As for stage I in addition to clinical signs

Other changes on blood work and urine could include:

• Non- regenerative anemia
• Increased phosphorus
• Low potassium levels
• Calcium is often normal but can be elevated in some pets with CKD and rarely is decreased
• Protein or bacteria in the urine

Other tests may also be recommended including:

1. Abdominal radiographs (x-rays) or ultrasound to evaluate kidney size
   What might this test show?  The kidneys in pets with CRD are usually small reflecting the death of a large number of nephrons. If the kidneys are large then certain causes for the CKD should be considered such as lymphoma (cancer) of the kidneys, or an uncommon disease called amyloidosis. Some pets with signs of kidney disease who have large or normal sized kidneys may have acute kidney failure rather than CKD. The treatment and prognosis for pets with acute kidney disease differs from the treatment and prognosis of pets with CKD.
2. Bacterial culture
   What might this test show?  Bacterial infection is not a common cause of CKD but pets with CKD may develop a bacterial infection as several aspects of the pet's immune system may be less functional when the kidneys are failing.  If white blood cells are observed on microscopic examination of the pet's urine, a bacterial culture of the urine should be obtained.
3. Urine protein/creatinine ratio
4. Blood pressure

What are the treatment options for my pet?

Unfortunately, chronic kidney disease is a progressive disease and is not curable.  However, there are many options available to help treat symptoms and signs associated with kidney disease.  There is no treatment combination that is standard for every pet and many times incremental addition to medications is needed as the disease process progresses.  In some cases, pets may need to be hospitalized for a period of time to replenish fluids and in other cases pets are sent home with conservative treatments.  I will list treatment options available, but remember that an individual pet may not need all these treatments.

• Diet modification:  Studies have shown that pets switched to a protein restricted (high quality protein), phosphorus restricted diet have a higher quality of life, fewer uremic crises, and may live longer than pets fed a regular maintenance diet.  There are many commercially available, prescription diets that meet these standards. 
• Phosphorus binders: Even with phosphorus restricted diets some pets still have elevated phosphorus levels.  In these cases, supplements can be added to the food that help bind more phosphorus and restrict levels even more
• Hypertension medications: High blood pressure often accompanies kidney disease and can lead to further damage to the kidneys.  Monitoring for hypertension and adding anti-hypertensive medications (amlodipine, ACE inhibitors) when present may be warranted in some pets.
• Stomach protectors: Build-up of uremic toxins can lead to stomach upset and inappetence.  Protecting the stomach lining with medications that lower the acidity of stomach contents can be helpful.  Medications can include antacids (famotidine or ranitidine), protein pump inhibitors (omeprazole), or stomach lining medications (sucralfate).
• Anti-nausea medication: Pets may also be inappetent because of nausea.  Cerenia or metoclopramide are examples of anti-nausea medications.
• Omega 3 fatty acids: Supplementing with fatty acids has been shown in some studies to improve survival in pets
• Anemia medications: The kidneys produce a hormone called erythropoietin that signals the bone marrow to make more red blood cells.  With kidney disease, this hormone may be depleted, so anemia develops in patients.  There are commercially available erythropoietin supplements that can be given to increase red blood cell counts.  Pros and cons of this medication should be discussed prior to starting the medication.
• Fluid supplementation: Since diseased kidneys are unable to concentrate urine properly, a pet will lose an excessive amount of water in the urine.  Making sure that water is always available and promoting water consumption is important.  In cases where a pet is not keeping up with fluid loses, either periodic subcutaneous fluids (can be done at home) or intravenous fluids may be necessary.
• Potassium supplementation: Excessive potassium is lost with diseased kidneys, which can lead to loss of energy.  Adding a potassium supplement may be needed.
• Calcitriol: Calcitriol is the active form of vitamin D and helps with regulation of calcium and phosphorus.  It is produced in the kidney, so may be decreased in patients with chronic kidney disease.  To help combat renal secondary hyperparathyroidism, calcitriol may be instituted.  Careful and periodic monitoring of calcium and phosphorus levels is recommended. 

As discussed earlier, not every pet needs every treatment and your veterinarian will evaluate blood work and clinical signs before recommending certain treatments.  Also, some pets are more amenable to treatment (especially in the case of cats) as multiple medications may be needed in a day.  Individual owner circumstances can also dictate how aggressive treatment might be.  With cats, combining multiple medications into a single gel cap may be easier than administering multiple medications at a time.

Goal of therapy:

As chronic kidney disease is not curable, our goal is to provide a good quality of life as long as we can.  Some owners may elect to only change the diet in response to diagnosis, whereas others may add as many medications as reasonable and possible to help their pet.  The goal is to find the right balance for both the owner and the patient.  With proper care some pets with early kidney disease can still live a great quality of life for years.

For more information from the perspective of an owner please visit http://www.felinecrf.com.

Parvovirus

I have recently treated a couple of cases of parvovirus and have had a few scares where the owner suspected parvovirus, so I thought it would be a good idea to discuss the virus and how we can prevent and treat the infection.

Parvovirus, as its name implies, is a virus that attacks rapidly dividing cells in dogs.  Two such areas where cells like this occur in the body are the gastrointestinal tract and bone marrow.  The virus attacking these areas leads to severe diarrhea, vomiting, and a decrease in white blood cells (which usually help to fight off infection).  Without treatment a majority of dogs will die from dehydration and infection.  Even with treatment, some animals may not survive.  It hits puppies particularly hard as their immune system is not fully developed and their ability to fight infection is low.  Un-vaccinated adults can also become infected, but may respond to treatment better since their immune system is usually fully developed.

The virus is picked up when a dog ingest infected soil or other contaminated materials.  It is a very hearty virus and can live in the environment (even harsh conditions) for over a year, so may be prevalent in areas of heavy dog traffic.  After the virus is ingested it replicates in the lymph nodes and then escapes into the bloodstream eventually ending up in the intestinal tract and bone marrow.  Infected dogs will typically have acute cases of vomiting, diarrhea, inappetence, and weakness.  In many cases, blood will be seen in the diarrhea or even the vomit.  Most vets have a good bed-side test for parvo that uses a rectal swab and gives a result in less than 10 minutes.

Because it is a virus, there is not much we can do besides provide supportive care to the pet while the virus runs its course.  Supportive care usually involves hospitalization with fluids, antibiotics, vitamins, nutritional support, and pain management.  If finances allow and it is available, some veterinarians will also treat with plasma that is rich in proteins and electrolytes.  In addition, some vets are using an anti-viral medication called Tamiflu (used against human influenza cases) to help treat parvo cases.  The medication does nothing against the parvovirus, but likely helps prevent the secondary infections that are seen with the cases.  Unfortunately, even with the most aggressive supportive care some dogs may not survive the infection.

The good news is there is a good vaccine to help protect against the virus.  Vaccinations typically start around 6 weeks of age and are given every 3-4 weeks until 16 weeks.  Then, the vaccine is boosted at a year of age.  The parvo vaccine is typically part of the "distemper vaccine" series which includes multiple viruses.  Prior to 6 weeks puppies have some protection if they were able to ingest enough colostrum (mother's milk for the first 24 hours).

So the moral of the story is to make sure that your pet starts vaccinations at 6 weeks of age to prevent this aggressive disease.

Glaucoma

What is Glaucoma?

Put simply, glaucoma is an increase in the pressure inside the eye.  The big question is what is causing the increased pressure.  Before talking about this, let’s talk a little about the inside of the eye.  The eye can be divided into structures in front of the lens and behind the lens.  The globe of the eye behind the lens has a chamber that is filled in with a thicker material called vitreous humor.  In front of the lens the eye contains a thinner material called aqueous humor.  Eye pressures are the pressure inside the aqueous humor.  The aqueous is produced by the ciliary epithelium next to the len.  It then flows forward from the posterior chamber through the iris opening into the anterior chamber and then finally drains out through the trabecular meshwork into the aqueous plexus (and back into the blood stream).  The production of aqueous and its drainage is typically well regulated, but when the production exceeds drainage, pressures rise and glaucoma results.

 What are the clinical signs of glaucoma and how is it diagnosed?

When pets have glaucoma you can notice a number of different signs including redness of the eye, abnormal blood vessels on the eye, different sized pupils, squinting, pawing at the eye, and vision problems.  The diagnosis of glaucoma is fairly straightforward and involves measuring the pressures of the eye and documenting an increased eye pressure.  Most veterinarians have a tool called a Tonopen that accurately and quickly measures eye pressures.  The eye is first numbed; then the Tonopen is pressed against the eye multiple times and records the pressure.  Normal pressures for dogs and cats are between 10-25 mm Hg.  Individual pressures above this confirm glaucoma or a major difference (>8 mm Hg) between pressures in either eye may indicate a problem. 

What causes glaucoma?

The causes for glaucoma can be divided into two major categories: primary versus secondary.

1. Primary glaucoma typically means there is an inherent change (typically breed related) in the drainage angle of the eye that causes reduced drainage of aqueous.  A majority of these are caused by abnormal formation of the drainage angle of the eye that results in a narrower angle and poor drainage (closed-angle).  A smaller subset appears to have a normal drainage angle, but the drainage is still impaired (open-angle).  Breeds where primary glaucoma is common include Cocker Spaniels, Basset Hounds, Schnauzers, Beagles, Poodles, as well as many others.
2. Secondary glaucoma occurs when other eye problems occur that alter the drainage of aqueous.  This may occur if the drainage angle of the eye becomes blocked (due to inflammation, cancer, cyst) or the iris opening becomes blocked (lens luxation or chronic inflammation of the anterior eye chamber).  Long term treatment for this glaucoma is more about treating the primary cause while managing the secondary glaucoma.

How do we treat glaucoma?

The first question to ask when treating glaucoma is whether the eye is still visual, as this will determine what options are available for treatment.  Also, with secondary glaucoma, it is important to treat the underlying cause as this may ultimately fix the problem.

1. Visual Eyes: The first goal for visual eyes is to decrease the pressures as quickly as possible.  The longer the pressures stay elevated the better chance at long term damage to the retina and subsequently vision. 

1. Topical medications: Many topical medications are available that help decrease the pressure of the eyes.  With severe cases of glaucoma multiple medications are started that work in different ways.  In most cases of sudden, severe primary glaucoma a medication to open the drainage angle (latanoprost) along with medications to decrease aqueous production (dorzolamide) are used together.  An intravenous medication called mannitol may also be used that helps draw out some of the vitreous of the eye making more room for the aqueous.  Some eyes with glaucoma respond well to these medications and can be managed with just topical medications for a time.  However, a long term solution usually involves surgery.
2. Surgical options: These options are only available through a veterinary ophthalmologist and financial costs can be very high.  With primary glaucoma the recommendation will usually be a combination of two procedures.  The first is cyclophotocoagulation, which is a procedure that destroys part of the ciliary body (tissue responsible for aqueous production) with a laser.  This helps lower aqueous production.  In addition, some ophthalmologists will also recommend placing a shunt that drains the aqueous humor out into the conjunctiva.  Even with these procedures, topical medications may still be needed and complications can occur.

1. Non-visual Eyes: Once eye pressures have been high enough for long enough the retina will degenerate and the eye will become non-visual.  When this is the case, our goal is to make the pet comfortable (as glaucoma is painful).  If topical medications aren’t working, then a few procedures should be considered.

1. Enucleation: Removing the eye eliminates the problem of the high pressures and pain.  This procedure can be performed by most veterinarians; however, if a prosthesis is desired then an ophthalmologist may be needed.  Even without prosthesis, most owners are happy with the cosmetic appearance of an enucleation.

2. Intravitreal gentamicin injection: This procedure is only available for dogs and there cannot be inflammation present in the eye when performed.  Gentamicin is an antibiotic, but for this procedure is being used because it kills the ciliary body and decreases aqueous production.  It works in around 75% of dogs, but cosmetic changes (cataract, small eye, etc) may be undesirable.  It is typically used as an alternative to enucleation when cost is a factor.

What to do about the other eye?

In many cases primary glaucoma develops in one eye before the other; however, the other eye has the same changes that led to glaucoma in the bad eye.  Starting the other, non-glaucomatous eye on a topical medication can lengthen the time before that eye develops glaucoma.  The typical medications used are either dorzolamide (Trusopt) or timolol (Timoptic).

Ultrasound

Sorry about the lack of blogging recently.  With the summer, things have been a little hectic.  I wanted to take some time now to discuss a newer form of testing we have added to our clinics here in Champaign/Urbana.  We have recently started to offer ultrasound services at our clinic in Savoy.  Currently, these are limited to abdominal (stomach, kidney, liver, spleen, etc) imaging, but we hope to offer echocardiogram (heart) imaging in the future.

The question you might be asking is what is ultrasound and when might we need to use it for your pet.  Unlike x-ray, which uses radiation to take images, ultrasound uses sound waves that are directed towards organs and the machine listens for the sound reflections from these organs to make images.  So instead of just being able to evaluate the outline of the liver or intestines (such is done with x-rays), we are able to better evaluate the architecture of organs.

Above are examples of ultrasound images from the intestines of cat.  As you can see, we can observe the different layers of the intestines and effectively evaluate for any thickening of the bowel or possible obstruction.

You might ask what would be a good use for this form of technology?  There are many patients where ultrasound can be helpful.  I will just talk about a couple examples.

Some owners have cats that may vomit periodically or may be losing weight.  We start with blood work and don't find many changes.  The next step may be an abdominal ultrasound.  During the ultrasound we scan all the abdominal organs, but in this case would likely focus on the intestines and pancreas.  With the ultrasound we can evaluate the intestinal wall thickness and see whether it appears thickened.  If the intestine is thickened, we can determine which layer of the intestine is thick and then can make a list of diseases (inflammatory bowel disease, lymphoma, etc) that could be causing the problem.  We can also evaluate the pancreas to see whether any signs of pancreatitis are evident.

Another case that ultrasound may be helpful would be to evaluate elevations in a dogs liver values.  In older dogs elevations of liver values can be benign or could indicate the start of a more serious condition.  With ultrasound we can evaluate the structure of the liver and possibly get an aspirate or biopsy sample to evaluate for a more serious condition.

Ultrasound on a dog

The nice thing about ultrasound is it that it is a non-invasive procedure.  We only have to shave the underside of the belly (and possibly sedate your pet) to get good images and a possible diagnosis.  Like any test, it may not give us all the answers, but many times can give us a lot more information that can benefit your pet greatly.

Ultrasound image of a kidney

Please let me know if you have any questions.

Oh my gosh, is that a Tick?

Nothing creeps people out more than finding a tick on their pet (or themselves for that matter).  Because of pets hair it can be difficult to find ticks on your pets until they have been feeding for a few days and become engorged.  When this is the case we can get concerned because ticks do transmit several diseases that are transferred to animals after the tick feeds.  First, lets talk a little about the tick life cycle.  Ticks have 4 life stages: egg, larva, nymph, and adult.  Depending on the species this cycle can take a year to 2 years to complete.  The larva, nymph, and adults all can feed on mammals.

In Illinois there are numerous tick species, but the most common that may be encountered are the American dog tick, lone star tick, blacklegged (deer) tick, brown dog tick and winter tick.  Most species are active in the spring and early summer and then are more dormant throughout the rest of the year (however, ticks can be active any time of year when temperatures are above 45 degrees).  Ticks hang around on the tips of grasses and scrubs (not trees) and when the plant is brushed by a pet or person they crawl onto the host.  Using their mouth pieces they attach to the skin and feed on the blood of the host.  When they bite, ticks typically secrete saliva that has anesthetic properties, so the bite is not felt.  Ticks can feed for several days and become quite engorged prior to falling off.

Why is it important to try and prevent tick bites?  When ticks feed on blood, they can also transmit diseases to the host they are feeding on.  Common diseases that are passed include Rocky Mountain Spotted Fever, Lyme disease, Erlichia, Anaplasmosis, as well as other blood-borne pathogens.  Many of these organisms attack red blood cells, white blood cells, blood vessel lining cells and other cells in the body and can have serious, and possibly life threatening consequences.  So, it is much more advantageous to prevent attachment of ticks then to treat the diseases that may be passed along by a tick bite.  

How do you go about preventing tick exposure.  There are numerous products available that help repel ticks.  Many of the products are topical spot-on liquids that go on the back of the shoulder blades and last for around a month.  These products also typically protect against fleas.  Frontline and Advantix have been around for awhile and work fairly well.  Be cautious with using Advantix (dog only product) in a household with cats because it contains a permethrin which can cause problems (seizures, tremors) in cats.  Merial (the maker of Frontline) recently came out with another product called Certifect, which is the active ingredient in Frontline plus an added ingredient (amitraz) which helps repel ticks more strongly.  

There is also a very good product called Preventic, which is a collar containing amitraz that is put around the neck.  It starts working within 24 hours of application and lasts for 3 months.  This collar works very well and we don't see many side effects associated with it.  Occasionally, owners of pets with a Preventic collar may have a skin reaction when petting their animal.  Also, if ingested the collar can cause major issues, so if you have a pet who is good at getting collars off, this may not be the product for you.

What if you find a tick on your pet?  If the tick is not attached, simply remove the tick and dispose of it outside or in the garbage.  We will put them in alcohol to kill them prior to throwing them out.  If they are attached, then the tick should be removed.  Grasp the head of the tick as close to the skin as possible and pull straight out.  If you are not comfortable doing this, then contact your veterinarian and they can do it for you.  If the tick is engorged and you are in an area where ticks carry diseases (see above), then watch your pet closely for any signs of sickness (inappetence, lameness, lethargy).  Some veterinarians will start prophylactic antibiotics in this situation to treat tick-borne diseases.  Others may wait and suggest running tick-borne antibody titers in 8-12 weeks after exposure.

Ticks can cause huge problems, so it is best to prevent them in the first place.  Let me know if you have any questions.

So Many Choices...

With the start of Spring (and finally spring weather) it is always a good time to review heartworm and flea protection for your pet.

Heartworm disease is a parasitic infection that is passed by mosquiotoes when they feed on your pet.  Any pet is susceptable even if they don't spend a lot of time outdoors.  If you can imagine those warm summer nights sitting out on the porch (even if just for 5 minutes) and coming back in with what seems like hundreds of mosquito bites.  Well, those mosquitoes don't just feed on you and will look for any warm body to feed on; like your pet.  That being said, it is important that your pet (in particular dogs, but cats as well) be on a montly heartworm prevention.

Same goes for fleas.  You can see the previous post to get a more detailed discussion on fleas.  Basically, the moral of the flea story is it is much easier to prevent them than to treat your house after they have gotten out of control.  Fleas love to feed and love to multiply and if your pet is not protected they are a prime target for fleas.  Even if your pet only goes out for a short time (let's say to use the bathroom), that is long enough for a flea to hop on them and then come into the house and lay its eggs.  Because of this we recommend all pets be on a flea prevention.

Now that you know your pet should be on a heartworm and flea preventative, what preventative should you use?  Recently, it seems like there has been an explosion of different products available for prevention of heartworms and fleas.  Our clinic focuses on a couple of products that we believe work well. 

The first is a product called Trifexis.  The nice thing about this product is it prevents most of your major parasites all in one oral monthly tablet (Heartworms, Fleas, and Intestinal Parasites).  It is well handled by dogs with vomiting being the most common side effect.  We feel that it works very well for fleas; killing adult fleas in as quickly as 30 minutes.  The heartworm prevention in the medication is the same active ingredient as Interceptor, which has proven effective for a very long time.  The one downside with this medication is that it does not prevent against ticks; however, we have been adding in a Preventic collar in dogs at risk for tick exposure.

The other product or combination of products that we use is Heartgard and Frontline.  Heartgard prevents heartworm disease along with intestinal parasites.  It has been around for a long time and works very well.  It comes in a flavored tablet, so administration is easy.  Frontline is a topical flea and tick preventative (goes on the skin over the back).  It also has been around for a long time and works well, but you need to make sure that it is applied correctly.  It uses the natural oils of the skin to spread, so you have to make sure you do not bathe your pet or allow them to swim two days before or after application.  After that time it is water-resistant.  You also have to make sure that when applying the medication it get down to the skin and not just on the hair.  Both products are administered on a monthly basis.

There are numerous other products available, which likely are effective as well.  It is important that your pet be on one of these products as heartworms can be devastating to an animal and fleas not only are a nuisance, but can spread disease as well.