Summer is such a wonderful time of year. For me, there’s nothing better than firing up the grill, spending those warm nights outside and enjoying all that this great season has to offer. This summer is set to be as warm as ever, leaving us plenty of opportunities to get out for some fun in the sun!
It’s a great time of year for our pets as well. The warmer weather and longer days mean more walks, more playing fetch and more trips to the lake. As we head out to play with our furry friends, it’s important to make sure that we’re protecting them from illnesses they can catch while enjoying the great outdoors. Most pet owners are great at keeping up with our pets’ immunizations against such diseases as Rabies and Leptospirosis, but there is another threat to our pets’ health that we may not realize: parasites! According to the Companion Animal Parasite Council, less than 50% of pet owners administer parasite preventions to their pets as recommended by their veterinarian. Today, I’d like to talk about why parasite prevention is important to the health of our pets.
Heartworms and Roundworms and Hookworms, Oh My!
The parasites that affect our dogs and cats fall into one of two categories: internal parasites which live inside the body of your pet and external parasites which live on the surface of your pet’s skin. I’ll talk first about internal parasites such as heartworms and gastrointestinal worms such as roundworms, hookworms and whipworms.
Heartworms (Dirofilaria immitis) are transmitted by mosquitoes which carry the heartworm larvae in their mouths, injecting them into the dog’s bloodstream when they feed. Six months after this the larvae grow into adult heartworms, lodging in the right ventricle of the heart and the pulmonary artery, causing disruption of blood flow to the lungs.
Initially, dogs infected with heartworms may show no signs of illness at all. As the disease progresses, your dog may show some very subtle signs such as reluctance to exercise and a mild cough. As time goes on, damage is done to the heart and lung tissue. Some severely affected dogs will develop Caval Syndrome, in which the sheer number of heartworms (we’re talking hundreds here!) result in near blockage of not only the pulmonary artery, but also the vena cava, the largest vein in the body. Dogs with Caval Syndrome are invariably in severe cardiac and respiratory distress and are often in liver failure as well, resulting in a very guarded to poor prognosis. Thankfully, heartworm disease is treatable. However, the treatment is quite expensive and not without risk. Dogs being treated for heartworm disease must be watched very closely and restricted from vigorous exercise throughout the course of treatment and for at least 6 weeks after. This is because the dying heartworms must be broken down by the body. Vigorous exercise can result in the formation of emboli (clusters of dead heartworms) which can partially or completely occlude the pulmonary arteries, which is often fatal to the dog. Cats are also affected by heartworms, though their disease results in chronic asthma-like syndrome rather than the progressively worsening disease we see in dogs. Another important difference: no effective treatment for heartworms in cats exists, resulting in a disease that requires lifetime management. As you can see, it is far better to prevent heartworm disease than it is to treat it.
Intestinal worms such as hookworms, roundworms and whipworms are extremely common, particularly in warm, humid areas. 
Pets are generally infected with these parasites by ingesting their eggs, which are passed into the soil via the feces of infected animals. In the space of a few weeks these eggs hatch into larvae, and the larvae grow into adult worms that attach to the intestinal wall of its host, feeding on its blood. Female worms release their eggs into the stool, which are passed into the environment, beginning the cycle all over again. Dogs and cats that are infected with intestinal worms may show no signs at all, or may have diarrhea, poor appetite, or vomiting. Severely affected pets may have weight loss, anemia, severe diarrhea resulting in dehydration, and extreme lethargy. In very young animals and those with weak immune systems, intestinal parasite infections can even be fatal. What is even more concerning about intestinal parasites to us as pet owners (particularly those of us with young children) is that some of them are zoonotic, meaning that they can be passed from animals to people. Roundworms, for example, cause diarrhea and weight loss in people, as well as a syndrome called Visceral Larval Migrans, in which roundworm larvae migrate throughout the body, often causing damage to the liver, lungs and eyes. Hookworms can also cause diarrhea and weight loss, as well as a syndrome called Cutaneous Larval Migrans, in which hookworm larvae migrate under the skin, causing a painful rash.
Fleas and Ticks Make Your Pet’s Skin Crawl!
Our focus now turns to external parasites, which are not only a source of irritation to us and our pets, but can also be involved in the transmission of more severe disease. We’ve all heard of fleas, for example. The most common flea found in dogs and cats is the Cat flea (Ctenocephalides felis). They are a nuisance to dogs and cats the world over, particularly in warm, humid parts of the world. It seems like they’re everywhere, doesn’t it? That’s because of their ability to reproduce quickly and in great numbers. In fact, if you see an adult flea on your pet, here’s a sobering fact: it represents just 1% of the total flea population on your pet and in your house. Just think: for every flea that you see, there are hundreds of his friends that you can’t see, each with dozens of offspring just waiting to wreak havoc! A female flea produces 20-50 eggs at a time, totaling 500 throughout her life. These eggs are laid on the host then fall into the environment. They can survive outdoors in the grass, and indoors in carpeted areas. With the proper temperature and humidity, it will take about 12 
days for that egg to hatch into a larva. In 7-14 days, the larva will form a cocoon (pupae). The adult flea will emerge from its cocoon in as little as 7 days with the proper temperature and humidity. They then attach to a host and begin to feed on its blood. It is this that causes your pet to itch. Some pets are even allergic to flea saliva, causing a severe condition known as Flea Allergy Dermatitis, a syndrome in which pets are so severely itchy that they will often chew their skin raw, causing secondary bacterial infections. While flea infestations generally do not cause severe illness, they can cause severe anemia and even death in very young animals as well as those with pre-existing illness.
Another important external parasite in dogs and cats is the tick. There are hundreds of species of ticks, but those most commonly found in the Kansas City area are the American Dog Tick (Dermacentor variabilis), the Brown Dog Tick (Rhipicephalus sanguineus, right), the Lone Star Tick (Amblyomma americanum, left), and the Blacklegged tick (Ixodes scapularis). Ticks are generally found in highly wooded areas and fields with a great deal of brush.Most species of tick will go through four stages in its life cycle: egg, larva, nymph, and adult. During each
life stage after hatching from the egg, the tick must feed on blood to survive. Most ticks will feed on a different host at each life stage, dropping off each host to move on to the next life stage and then seeking out another host when that metamorphosis is complete. In contrast to fleas, which complete their life cycle in as little as three weeks, ticks can take up to three years to complete their life cycle, with most of them dying due to a lack of ability to find a host. This is why ticks tend to be found in specific environments (areas with a lot of plant and tree life with an abundance of hosts such as squirrels, deer and the like) whereas fleas can be found anywhere there is a warm, humid environment. Despite this, ticks are most certainly a threat to our pets’ health as well as our own. Most concerning is the tick’s ability to transmit infectious diseases to our pets, such as Lyme disease, Ehrlichiosis, Anaplasmosis, and Rocky Mountain Spotted Fever. These infections can cause a myriad of serious and potentially deadly complications, including bleeding disorders, hemolytic anemia, kidney failure, heart failure and immune mediated arthritis. Of even greater concern is the notion that these diseases (particularly Lyme disease and Rocky Mountain Spotted Fever) are transmissible to people, causing much the same medical problems.
So How Do I Keep These Bugs Away?
We’ve talked a lot about some scary parasites in this article. Obviously these are pests that we want to keep far away from our pets and homes! Well, I’m glad to tell you that advances in our understanding of parasite biology in the past 20 years have given way to the development of exquisitely effective, yet very safe, medicines that do just that. We at Mill Creek Animal Hospital recommend year-round administration of external and internal parasite prevention to all dogs and cats, whether they reside primarily indoors or outdoors. Your options for doing this are numerous and diverse, and we’re here to help you make an informed decision as to what will be best for you and your pet. After performing a physical examination of your pet and talking with you about his/her environment and lifestyle, we can tailor a parasite prevention program specific to your needs. This may 
entail using the traditional monthly tablets for internal parasites, all-in-one topicals for internal parasites and fleas (pictured at left), or the new injectable heartworm prevention that lasts six months (pictured at below). We at Mill Creek are passionate about keeping your pet free of parasites,
allowing you to go enjoy the best that spring and summer have to offer. So get out there and play: we’ve got you covered!