Heartworm in Dogs: Symptoms, Treatment, and Prevention

Heartworm is a potentially lethal parasite that is transmitted only by mosquitos, which pick up larval heartworms, called microfilaria, circulating in the bloodstream of infected animals.

Dogs and other canids, such as foxes, wolves, and coyotes, are considered the primary heartworm hosts, but these parasites can also affect other mammals, including your cats and ferrets.

There are treatments available for dogs, but prevention is the wisest approach to dealing with heartworms.

What is Heartworm Disease?

The heartworm in dogs that’s prevalent in the U.S. goes by the scientific name Dirofilaria immitis or D. immitis. It does not spread from dog to dog, but requires an intermediary—the mosquito—to infect new hosts.

The worms enter their host through a mosquito bite when it is taking a blood meal. Residue on the mosquito’s mouthpiece carries immature worms called microfilaria (which are only about 1/100th of an inch long) from an infected animal to an uninfected one. The immature worms travel through the bloodstream and, after about two months, settle in the right side of the heart and begin to grow.

They mature after six months and can live in the dog’s body for seven years, each reaching up to one foot in length, and constantly producing offspring. After about a year, a dog may harbor hundreds of these worms, although 15 is the average burden. The worms cause inflammation and damage the heart, arteries, and lungs.

How widespread are heartworms?

The first canine heartworms in the U.S. were discovered in the southeast in 1856. While it was once more common in the Atlantic and Gulf coast states, the American Heartworm Society, in its first update since 2014, reports that heartworm is increasing throughout the country and worldwide. In the report, Cassan Pulaski, DVM, MPH states that, “…While southern regions of the country have historically been associated with heartworm, we now know pets all over the country are potentially at risk for heartworm disease throughout the year.” According to U.S. Food & Drug Administration, incidents of the disease have been reported in all fifty states. This is especially important to keep in mind if your dog travels.

Areas with large populations of wild or stray animals also pose an enhanced risk, but even dogs that stay inside most of the time are not totally safe from a mosquito’s bite. Also, pets being shipped from state to state may introduce heartworm into regions where it was historically not a problem. This is especially notable due to the bringing in of shelter dogs from heartworm endemic states and from disaster relief efforts. After Hurricane Katrina in 2005, for example, about a quarter of a million pets traveled from the New Orleans area to new homes around the country. Some brought heartworm with them. AHS estimates that more than a million pets in the U.S. are infected. The AHS notes that climate and environmental change also contribute to the spread of the disease.

Should your dog be tested for heartworm?

• All dogs should be tested annually, even those on heartworm prevention medication year round.

• Puppies under seven months old may be started on heartworm prevention even though it can take six months or more for blood work to test positive. After that, they should be tested in six months and again, six months later.

• Adult dogs over seven years old that have not previously been on a heartworm prevention regimen should be tested.

• Dogs that have missed a treatment, or for whom treatment has lapsed, need to be tested. If you’ve missed even one dose, or been late to administer, your dog should be tested.

What are the symptoms of heartworms?

In the early stages, there may be no signs of disease. As the worms grow and multiply, symptoms will become evident, increasing in severity as the disease progresses. There are four classes of infection:

• Class one has no symptoms or just a mild cough.

• Class two is marked by mild exercise intolerance and persistent cough.

• Class three will result in greater exercise intolerance, abnormal lung sounds, weak pulse, syncope (fainting caused by impaired blood flow to the brain), decreased appetite, weight loss, and ascites (swollen belly due to heart failure).

• Class four is known as caval syndrome, a life-threatening cardiovascular collapse, which is marked by labored breathing, pale gums, and dark coffee-colored urine, leading to complete organ failure and death.

How is heartworm diagnosed?

Early diagnosis important; the earlier heartworm is detected, the better the chances for recovery. In many cases, a blood test can determine the presence of the parasite. The blood is tested for the presence of antigens (proteins) even if there is no evidence of microfilariae. If your dog is diagnosed with heartworm through a blood test, your veterinarian will use additional tests for confirmation and make sure your dog can safely undergo treatment. These include:

• Radiographs to pinpoint abnormalities in the right side of the heart and pulmonary arteries.

• Ultrasounds to show abnormal organ shape as well as wriggling worms.

• Echocardiography to see inside heart chambers and visualize worms.
  

How to treat heartworms in dogs

Confirm diagnosis

Treatment is expensive and complex, so your vet may want to perform additional tests to confirm the diagnosis.

Restrict activity

Although it may be difficult to restrict normal activity, especially in active dogs, this is crucial. Exertion will increase the rate of damage to the heart and lungs. Crate confinement may be necessary.

Stabilize the disease

If your dog has advanced symptoms or other medical conditions, preliminary therapies may be required.

Kill worms

The drug that is FDA-approved for treatment in the U.S., is melarsomine dihydrochloride, which is sold under the brand names Immiticide and Diroban.

It is administered by deep intramuscular injection into the dog’s lumbar region of the lower back and is recommended for disease that has not progressed past class three. Another FDA-approved drug, Advantage Multi for Dogs (imidacloprid and moxidectin), rids the bloodstream of microfilariae. In addition, other drugs such as heartworm preventives, antibiotics, and steroids may be part of your veterinarian’s protocol.

Surgery

In extreme cases, veterinarians will resort to surgery, physically pulling the worms out.

Follow-up testing

The first test should take place six months after successful treatment.

Preventing heartworm

Treatment for heartworm is hard and sometimes dangerous for the dog and very expensive, which is why veterinarians are so adamant about yearly testing and administration of preventative compounds — what scientists call chemoprophylaxis. The current AHS guidelines include the following:

• Year-round administration of a heartworm prevention medication.

• Strict compliance to the schedule of dosing recommended by your vet.

• Application of FDA-approved mosquito repellants.

• Environmental control to reduce or eliminate mosquito breeding grounds, such as pools of standing water; the use of mosquito traps; and avoiding your dog’s exposure by limiting outdoor activities at dawn and dusk, mosquitos’ prime feeding time.

• These medications, used for prevention, are also effective against other parasites, such as roundworms, hookworms, fleas, and tapeworms. Make sure to use a formulation specifically intended for dogs.

For more information on heartworm prevention relevant to your doggo, speak directly with your veterinarian.

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Cannabis (Marijuana) Intoxication in Cats and Dogs

Marijuana (or cannabis) refers to the dried parts of the Cannabis plant. Cannabis has been used since 500 BC as cannabisan herbal medicine, and for products such as rope, textiles, and paper. Today, cannabis is primarily used for medicinal or recreational purposes. Cannabis can be smoked like a cigarette, inhaled via vaporizers, or ingested via food and drink.

Cannabis contains more than 100 different chemicals (or compounds) called cannabinoids. Tetrahydrocannabinol (THC) is the cannabinoid that has the most psychoactive effects. It is also the compound responsible for some of cannabis’ medicinal uses, such as treating nausea and improving appetite in cancer patients. Other compounds, such as cannabidiol (CBD), have shown promise for medicinal use and do not have psychoactive effects.

"The increased accessibility to the drug has led to an increase in accidental exposure in pets."

While cannabis use is not new, its use for recreational purposes is more recent. In the 1970s, cannabis was criminalized in the US when it was labeled a Schedule 1 (Class I) drug. In the 1990s, individual states began legalizing cannabis for medicinal use, and more recently, 9 states have legalized it for recreational use. Legalization for recreational use in Canada occurred in 2018. As with any other medication, the increased accessibility to the drug has led to an increase in accidental exposure in pets.

How do cats and dogs become intoxicated?

Cats and dogs can become intoxicated by cannabis in various ways; by inhaling second-hand smoke, eating edibles (baked goods, candies, chocolate bars, and chips containing cannabis), or ingesting cannabis directly (in any form). Most exposures are accidental when curious pets discover access to the drug or when they are present in the same room with a person smoking cannabis. Dogs have more cannabinoid receptors in their brains, which means the effects of cannabis are more dramatic and potentially more toxic when compared to humans. A small amount of cannabis is all it takes to cause toxicity in cats and dogs.

Regardless of the method of exposure, accurate and complete information is imperative to treat the patient successfully. For example, ingestion of a 'pot brownie’ needs different treatment than inhalation, because eating the brownie requires treatment for cannabis and chocolate toxicity, whereas inhalation may require additional treatment for respiratory irritation.

How does cannabis affect cats and dogs?

Like most drugs, the effects of cannabis are based on chemistry. The drug enters the body via inhalation or ingestion and binds with specific neuroreceptors in the brain, altering normal neurotransmitter function. THC interacts with neurotransmitters such as norepinephrine, dopamine, serotonin, and acetylcholine. Humans and pets have two types of receptors in their bodies. One type, CB1, affects the central nervous system, and the other, CB2, affects the peripheral tissues. Although not all the pharmacologic mechanisms triggered by cannabinoids have been identified, it is thought that CB1 is responsible for most of the effects of cannabis.

Everything that enters the body has to exit the body. THC is very lipid-soluble, which means that it is easily stored in the fatty tissue in the liver, brain, and kidneys before being eliminated from the body. THC is metabolized in the liver and the majority (65-90%) is excreted in the feces, while a small percentage (10-35%) is eliminated through the kidneys. The drug has to be metabolized and excreted for the effects to wear off.

How toxic is cannabis?

Cannabis is considered to have a high margin of safety for people; however, not all people, and certainly not all pets follow a single pattern of intoxication. A small amount may affect one pet more than another, so there is no official safe level of exposure. Differences in age, health status, and body size are some of the factors that can lead to toxicity differences.

Luckily, cannabis intoxication is seldom fatal. The average marijuana cigarette contains about 150 mg of THC. The minimum lethal oral dose of THC in pets is fairly high; however, deaths have been noted after ingestion of foods containing highly concentrated cannabis, such as medical-grade THC. In fact, fatalities were very rare until the development of medical-grade products.

What are the signs of cannabis intoxication?

Many of the signs of intoxication are neurological. Pets may become wobbly and uncoordinated. They may be hyperactive, disoriented, and very vocal. Their pupils may dilate, giving them a wild-eyed appearance, and they may drool excessively or vomit. They may also develop urinary incontinence (i.e., urine leakage). In severe cases, tremors, seizures, and coma can result.

Side effects are usually short-lived, but they can still be dangerous. Physical signs include low or elevated heart rate and blood pressure and slowed respiration rate (breathing rate). Lethargy and increases or decreases in body temperature may also be observed. Fortunately, these side effects are usually short-lived, but they can still be dangerous and make the pet quite miserable.

How is intoxication diagnosed?

Diagnosis is based on an accurate history and clinical signs. Although there are tests to determine the level of THC in the urine, the results take time, making them impractical. Human urine drug-screening tests are quicker but are not dependable in pets. The diagnosis is made much more quickly and treatment initiated when responsible pet owners provide accurate information regarding the pet's exposure.

How is intoxication treated?

When a toxin enters the body, often the first line of defense is to get it out. If the toxicity is discovered shortly after ingestion, your veterinarian may induce vomiting to prevent further absorption of the toxin. Two factors may interfere with this early defensive strategy. First, the signs of toxicity may manifest only after the drug has been absorbed, meaning it is already in the system. Second, cannabis has an anti-emetic effect that inhibits vomiting. In life-threatening cases, the stomach may be pumped (gastric lavage). Activated charcoal may be administered every 6-8 hours to neutralize the toxin. Enemas are also used to reduce toxin absorption from the GI tract.

The second line of defense in cannabis toxicity involves providing supportive care until the effects of the drug wear off. Medications and supportive care to regulate the pet's heart rate, respiration, and body temperature are used if needed. Since the pet may be lethargic, with no desire to eat or drink, IV fluids can help prevent dehydration, support blood pressure, and maintain organ function. Anti-anxiety medications can minimize agitation. To prevent self-trauma while the pet is disoriented and uncoordinated, confine them in a safe, comfortable space. Noise should be kept to a minimum to decrease sensory stimulation.

The Bottom Line

The bottom line, when it comes to cannabis use and pets, is similar to that with other drugs in the home: Be careful. Keep all forms of cannabis, medical or recreational, out of reach of your pet. Consider storage in high cabinets or in locked drawers when not in use. Keep pets in a separate and well-ventilated room, away from second-hand smoke. Remember that pets have a good sense of smell and will be tempted to eat candies, chips, chocolates, and cannabis directly if accessible. If you notice suspicious behavior in your cat or dog and cannabis exposure is a possibility, take your pet to your veterinarian or the nearest emergency veterinary hospital for treatment.

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Rainy Season Dangers for Dogs

Each year, certain parts of North America are bombarded with rain. While this may be good for the garden, high rainfall can potentially pose some real threats to your dog.

Mushrooms

During the rainy season, mushrooms may pop up in your yard with more frequency. There are thousands of species of mushrooms, but thankfully only about 100 are poisonous. That said, mushroom identification is very difficult, so it's hard to tell which are poisonous versus which are benign. As a result, whenever you see mushrooms growing in your yard, make sure to remove them immediately and throw them away to prevent accidental ingestion by your dog. If your dog does get into a mushroom, contact your veterinarian immediately about inducing vomiting to get any potential toxin out.

Certain types of mushrooms may cause organ injury including:

• Gastrointestinal injury (signs include drooling, not eating, vomiting, diarrhea)

• Liver linjury (signs include vomiting, black tarry stool, yellow skin)

• Kidney injury (signs include abnormal urination and thirst)

• Cardiovascular injury (signs include a very slow or rapid heart rate)

• Neurologic injury (signs include hallucinations, tremors, seizures)

When in doubt, get to your veterinarian immediately as it's easier - and less expensive - to treat early on versus once clinical signs have developed.

Leptospirosis

Leptospirosis, a bacteria-like spirochete, is carried naturally by wildlife, like rodents and raccoons. In high rainfall situations, it’s prevalent in the environment. In dogs that have exposure to water sources, contaminated by wildlife urine (puddles, streams, ponds, etc.), transmission can occur. Canine leptospirosis can result in liver injury and acute kidney injury.

Signs of leptospirosis include:

• Vomiting

• Not eating

• Malaise

• Yellow skin

• Excessive thirst

• Urination

As leptospirosis can accidentally be transmitted to humans, it's important to talk to your veterinarian about prevention, including vaccines.

Click here to learn more about leptospirosis.

Mosquitoes

While mosquitoes may seem like just a pesky insect to you, they can be life-threatening to your dog. That's because mosquitoes can carry Dirofilaria, which transmits heartworm infection to your dog. Thankfully, there is a very effective preventative in either a topical or oral form. When in doubt, use year-round control to prevent problems from mosquitoes. If your dog has thin fur or skin and is more predisposed to getting bitten, use a vet-approved topical insect repellent that repels mosquitoes or talk to your veterinarian to be safe before applying anything.

Click here to learn more about heartworm disease in dogs.

Toads and frogs

Depending on where you live in the United States, certain types of toads - specifically the Bufo marinus or Bufo alvarius - can be poisonous to dogs. In fact, a dog drinking water from an outside dog bowl, that had a poisonous toad sitting in it, can result in clinical signs of drooling, panting, walking drunk, a racing heart rate, a very slow heart rate, or even seizures. Frogs are not toxic, but can cause gastrointestinal upset when ingested.

To be safe, supervise your dog outside to prevent accidental ingestion of dangers like toads and frogs. When in doubt, contact your veterinarian or ASPCA Animal Poison Control Center at 888-426-4435 if you think your dog is ill or could have ingested something poisonous.

Click here to learn more about toad toxicity to dogs.

If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.

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Dealing With a Shedding Dog

Dog shedding can be frustrating for all of us, no matter how much we love our dogs. The mess of dog hair can be enough to drive dog owners nuts. All dogs shed to some degree, with the exception of completely hairless dogs. Certain breeds (so-called hypoallergenic dogs) shed very little, while others (namely heavily double-coated breeds) shed large amounts.

Year-Round Shedding

All animals with hair shed on a regular basis. This is part of the natural life cycle of hair shafts within the follicles. All hair shafts go through phases of growth and shedding. The phases affect the rate of hair growth and will vary by breed, age, hormones, environment and overall health of the dog. These factors also contribute to the length and texture of the hair, though genetics is the predominant factor.

Dogs with continuously growing hair, like Poodles and Yorkshire Terriers, have hair shafts with longer life spans and shed very little. On the other hand, dogs like Labradors and Huskies have a shorter hair shaft lifespan and more abundant undercoats, resulting in greater shedding.

Shedding Season

In general, most dogs will shed extra during spring and fall. Most dogs have two coats; they have undercoats and top coats. The top coat is what you see and feel on the outside. The undercoat is made up of secondary hairs that grow around the primary hairs and tend to be shorter and softer. Seasonal shedding occurs as a result of temperature change. This process is sometimes called "blowing coat." When the weather warms, dogs shed their old winter undercoats to make way for a lighter summer coat. Then, when it begins to get cool again, dogs shed their lighter undercoats and grow thicker, warmer coats for winter.

Not all coat types are affected the same way by temperature changes. For example, dogs like Bichons and Shih Tzus have less undercoat, so they shed less when seasons change. The old coat must still be removed by grooming the dogs. However, dogs like Newfoundlands and Malamutes have heavy, thick undercoats that make shedding much more obvious. Basic brushing is important for both coat types.

Other Reasons for Shedding

Your dog's health can affect the shedding rate, so it is important to take note of unexplained excessive shedding. Skin problems, endocrine diseases, nutritional or vitamin deficiencies, and other metabolic disorders can cause hair loss or change the rate of hair growth. It is important to contact your veterinarian if the rate of shedding seems unusual for your dog. Keep your dog healthy with routine vet visits and proper nutrition. Contact your vet immediately if you notice any signs of illness.

Get Control Over Shedding

There's no way to completely stop shedding. It's a healthy and natural process that is necessary for dogs. Shaving your dog down is not a good idea, as it can interfere with your dog's natural self-cooling and self-warming mechanism. In the long run, it will not make shedding occur any less. In rare cases, the hair in shaved areas will grow back abnormally or not at all. The key to preventing excessive shedding is to keep up with it with brushing.

Routine grooming is absolutely essential for all dogs. Brushing or combing your dog helps to remove dead hairs before they can fall on your carpet, bedding, and upholstery. It will also prevent those dead hairs from forming mats on your dog's coat that can eventually harm the skin. Brushing also distributes the natural, healthy oils produced by the skin throughout the hair coat. Using the right grooming tools can make a great difference. For heavy shedders, a special shedding tool like the FURminator can work wonders. For some coat types, the dead hairs don't shed as much, but they cause the dog's coat to appear ragged and can eventually become matted. Some owners prefer to take these dogs to a professional groomer periodically for coat care. For some coat types, hand-stripping is a technique that is often preferred over trimming the dog's hair.

Managing the Aftermath of Shedding in Your Home

Shedding makes a mess, no doubt about it. As a dog owner, you have probably come to terms with the fact that regular house cleaning is the norm, especially during shedding season. The key is to remove hair before it has a chance to embed itself into your carpet and upholstery. Keeping a pet hair tape roller around for touch-ups throughout the day is an excellent idea.

For a deeper cleaning of upholstery and small areas, consider using a handheld vacuum designed to pick up pet hair, like the Dyson DC31 Animal. When it comes to cleaning carpets, Panasonic's Pet-Friendly JetSpin Cyclone does the job well. For non-carpeted floors, some excellent options include the Swiffer, the Fur-Be-Gone Broom, and similar style products.

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Dog Eye Allergies: Symptoms and Treatment

If you notice that one or both of your dog’s eyes are red, you may be wondering what the cause could be.

Dogs with allergies more commonly show symptoms related to the skin or intestinal tract, but it is possible that allergies may be causing the irritation in your dog’s eyes—just like in people with seasonal allergies.

The medical term “allergic conjunctivitis” is used to describe inflammation of the eye that’s usually caused by environmental allergens like pollen and mold. Dogs with skin-based allergy symptoms (allergic dermatitis) are more likely to experience allergic conjunctivitis than dogs with no history of allergies.

If you believe that your dog is suffering from allergic conjunctivitis, it’s important to have them seen by a veterinarian to rule out other more serious diseases that can have similar symptoms.

Here’s what you need to know about dog eye allergies.

Symptoms of Dog Eye Allergies

In dogs, redness of the eyes is a vague symptom that can be caused by a wide variety of underlying diseases.

For allergic conjunctivitis, redness is usually seen in both eyes. You may also notice symptoms like:

• Squinting of the affected eye(s)

• Pawing at the face

• Discharge coming from one or both eyes

Dog Eye Allergies and Itchy Skin

If your dog has a history of itchy skin, it's worth mentioning to your veterinarian.

Dogs with itchy skin will more commonly experience allergic conjunctivitis than the general dog population.

Affected dogs are usually under 3 years of age when they first become symptomatic. Although all dog breeds have the potential to develop allergic dermatitis, common breeds with a predisposition for this condition include:

• Boxer

• Cocker Spaniel

• French Bulldog

• German Shepherd

• Golden Retriever

• Labrador Retriever

• Poodle

• West Highland White Terrier

How Do Vets Diagnose Dog Eye Allergies?

Although a test called “conjunctival cytology” may reveal inflammatory cells that will confirm a diagnosis of allergic conjunctivitis, the cells are not always present. As a result, many veterinarians will diagnose eye allergies through the process of elimination.

Your veterinarian may perform several brief tests to rule out diseases with similar symptoms, like eye infections, dry eye, or corneal ulcers. Other details, like your dog’s age, breed, and history of itchy skin, can also help point your veterinarian to this diagnosis.

In rare cases, a biopsy of the conjunctival tissue around the eyes—taken while your dog is under general anesthesia—may be needed to achieve a definitive diagnosis, or to rule out other, more serious causes of red eyes.

An emerging test called the conjunctival provocation test has shown promise as a quick and easy test to definitively diagnose allergic conjunctivitis. However, it’s currently not widely available and would likely be performed by veterinary dermatologists—not your general practice veterinarian.

What Can You Give Dogs With Eye Allergies?

In mild cases, simply flushing the eyes with sterile saline once or twice a day may be enough to remove the allergen and resolve the symptoms.

You should not use contact solution for this purpose.

Although antihistamines provide relief for people with eye-related allergies, antihistamines have a variable effect in dogs with this condition. Therefore, eyedrops containing steroids are often the treatment of choice for dogs with allergic conjunctivitis.

It’s important to note that steroid-based eyedrops can be very harmful to dogs with other, similar diseases in the eyes, so you should never start treatment without first consulting your veterinarian.

Severe cases may require the use of oral medications in addition to eyedrops.

Follow-Up Testing and Treatments

Generally, a recheck is recommended after one to two weeks of treatment so that your veterinarian can assess how well the medications have worked.

If minimal improvement is seen, it’s possible to be seen by a veterinary dermatologist, who can perform allergy testing and other diagnostics to uncover which allergens may be triggering your dog’s allergic conjunctivitis.

If possible, the allergens are removed, often by changing the diet. If removing allergens is not possible, your dog’s dermatologist may suggest immunotherapy for long-term treatment.

If the allergen can’t be removed or treated with immunotherapy, it is very likely that a dog with allergic conjunctivitis will experience flare-ups throughout her life. Fortunately, the symptoms caused by allergic conjunctivitis are fairly mild, and with proper treatment and management, affected dogs generally live long and happy lives.

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