Parasites & How to Prevent Them!


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Starting December 2023

When we ring in a new year, many of us make pledges to live a healthier lifestyle. But what about a healthier lifestyle for our furry friends? Many pet owners take their dogs and cats to a veterinarian for annual wellness exams, and during those visits vaccinations and parasite prevention/control are often discussed. Most owners are familiar with the importance of vaccination, but some may not be aware of how crucial providing effective parasiticides might be.

What are parasiticides?

Parasiticides are a group of drugs used in the management and treatment of infections caused by parasites. They are often referred to as parasite prevention or parasite control.

When I speak with clients about parasite prevention, I am strictly referring to heartworm prevention. Our goal with these products is to completely prevent the dog or cat from ever contracting heartworms. For our canine friends, there are injectable, oral, and, topical options. For the felines, there are oral and topical options available.

The products that control the lifecycle and populations of fleas, ticks, and intestinal parasites are often referred to as parasite control. These products are designed to terminate parasites at a certain life stage or several life stages. Some products will only sterilize the adult parasite while others will kill the adult, juvenile, and eggs. There are oral and topical options available for dogs, but only topical options available for cats.

Why are parasiticides important?

Now you might be thinking “I’ve never seen a flea or tick on my dog (or cat)!” Well, did you know that the majority of people diagnosed with Lyme disease never saw the tick that infected them? This is because most infections are caused by immature ticks (nymphs), and they are very small (2mm in diameter). Could you imagine trying to find those on an animal covered with fur? Just because you cannot see a problem does not mean there is not a problem. Fleas, ticks, intestinal parasites, and heartworms can all cause devastating and life-threatening diseases.

  • Fleas
    • The Black Plague is caused by a bacteria carried by fleas. Cases are still seen today in the rural Southwest.
    • Cat scratch disease is caused by a bacteria that is found in flea feces (flea dirt). People can become infected after being scratched by a dog or cat that also has a flea infestation.
    • Tapeworms are intestinal parasites that dogs, cats, and sometimes people can contract after ingesting an infected flea (or other crunchy bug).
    • Since fleas feed on blood, a heavy flea burden (infestation) can cause life-threatening anemia which will require hospitalization, blood transfusions, and supportive care for a favorable outcome.
  • Ticks
    • Since there are so many tick-borne diseases out there, I am only going to focus on the more common ones:
      • Lyme disease is caused by a bacteria that is most commonly spread by the deer tick (black-legged tick). It can take 2-5 months after the bite before symptoms begin to show. Symptoms may include fever, lameness, limping, joint pain/swelling, enlargement of lymph nodes, and lethargy. In some cases, Lyme disease can lead to kidney failure which can become fatal.
      • Ehrlichiosis is also caused by a bacteria, but is most commonly spread by the brown dog tick. The early symptoms of ehrlichiosis may include fever, swollen lymph nodes, respiratory distress, or weight loss. Oftentimes, the immune system is able to eliminate the organism, but if it is unable to do so more severe symptoms can be seen. These may include anemia, spontaneous bleeding, lameness, eye problems, neurologic conditions, limb swelling, and bone marrow suppression.
      • Anaplasma is another bacteria that is most commonly spread by the deer tick and the brown dog tick. The symptoms for anaplasma can sometimes be vague, but may include decreased appetite, lethargy, neck pain, bruising, and spontaneous bleeding.
    • Intestinal Parasites
      • Roundworms are parasites that live in the small intestines of dogs and cats. Most puppies and kittens are infected with roundworms at birth. The majority of pets do not show symptoms of a roundworm infection. However, if there is a heavy burden, we can see vomiting, diarrhea, coughing, weight loss, and potbellied appearance. Sometimes, roundworms can be passed in the stool or coughed up. They are long, white, and have a spaghetti-like appearance. Roundworms are zoonotic which means we can catch them from our pets. Humans can become infected via fecal-oral transmission (swallowing eggs from infected feces, sand, or soil).
      • Hookworms are another parasite commonly seen in puppies and kittens. Hookworms attach themselves to the intestinal wall to feed. While feeding they secrete an anticoagulant. This causes continued bleeding once the hookworm detaches. Heavy hookworm infections can cause life-threatening anemia. It is rare to see the parasite passed in the feces, but symptoms of infection may include weakness, lethargy, bloody diarrhea, pale gums, weight loss, and failure to grow. These parasites are also zoonotic. Humans can become infected by fecal-oral transmission or cutaneous larval migranes (larva penetrating the skin).
      • Whipworms live in the cecum (where the small intestines meet the large intestines) and colon (large intestines) of dogs. The adult worms embed in the intestinal lining which causes irritation and discomfort. Whipworm eggs can remain viable in the soil for up to five years. Oftentimes, dogs do not show any signs of whipworm infection, but if they suffer from a heavy burden, diarrhea, dehydration, and weight loss can be seen. Whipworms can also cause anemia which can be life-threatening if left untreated. These parasites do not have zoonotic potential as dogs are their primary host.
      • Tapeworms are typically transmitted by fleas that are infected with tapeworms. Tapeworm infections are rarely of serious concern in healthy adult animals, but have been known to cause intestinal blockages in young puppies or kittens. Unlike other intestinal parasites, tapeworm infections are typically diagnosed by the observation of tapeworm segments (proglottids) found in the feces or on the rear end of the infected animal. These proglottids typically have a rice-like or sesame seed appearance. Zoonotic potential is low for these parasites with children being the most likely to become infected.
    • Heartworms
      • Heartworm disease is a serious and life-threatening disease that is caused by twelve-inch long worms that live in the heart and lungs of infected animals.
      • Heartworms are transmitted by infected mosquitos.
      • Both dogs and cats are affected by heartworm infections.
      • Studies have shown that 15-25% of cats (regardless of if they are indoor or outdoor) have been exposed to heartworms.
      • Heartworm infections should be treated as quickly as possible once detected. Permanent damage to pulmonary vasculature begins before heartworms can even be detected by standard tests.
      • Heartworm disease has been documented in every state but Alaska.
      • Year-round prevention is recommended for all dogs and cats in all regions of the country.
      • Missing just one dose of prevention could cause your pet to become infected with heartworms.
      • There is no treatment for heartworm infections in cats. Since cats are not a primary host for heartworms, they are often unable to reproduce and thrive; therefore dying off on their own, but not before permanent damage is done to the heart, lungs, and associated vasculature.
      • An anti-parasitic drug that is derived from an arsenic compound is most commonly used to treat heartworm infections in dogs. It is often given in a series of three intramuscular injections. This treatment can cause discomfort, pain, and swelling at the injection site. However, more severe complications, including death, can arise from treatment especially with advanced stages of heartworm disease.
      • When it comes to heartworms, PREVENTION IS THE BEST MEDICINE.

How are these parasites and diseases diagnosed?

Fleas and ticks are most often diagnosed by the visualization of the organism or signs of its presence (flea dirt) on the pet.

Heartworm infections and the tick-borne diseases that I listed can be diagnosed via blood tests. Most veterinary practices screen for heartworms and these tick-borne diseases using a single test. It is recommended that this test be performed annually despite consistent administration of a parasiticide. This is to ensure that the medication being prescribed is effective, and the earlier we detect a disease process, the easier it is to treat with fewer complications.

The majority of intestinal parasites are diagnosed via microscopic observation of parasite ova (eggs) in a fecal sample. However, there can still be an intestinal parasite infection even if no ova are seen. This can be due to an inadequate sample size or because the parasites are not shedding eggs at the time of the screening. In these cases, antigen (which tests for the presence of specific antibodies) tests can be performed at a reference lab to determine if there is an infection or not.

How do I choose a parasiticide?

Generally, effective parasite prevention and control are going to be obtained from your veterinarian. After performing a physical exam, diagnostic tests, and reviewing your pet’s medical history and lifestyle, your veterinarian can recommend safe and effective products. For example, a topical product may not be effective for a dog who swims or is bathed frequently.

Pet stores and online stores are full of over-the-counter (OTC) flea and tick control options, but unfortunately, many of these products are not effective and/or can be harmful to your pet. If you prefer to use OTC products, your veterinarian can guide you towards effective and safe options. Also, be sure you are getting these products from a reputable source as there are many counterfeit products being sold that may be ineffective and/or unsafe. You also want to ensure these products are being stored properly before hitting the shelves if you are purchasing from a feed or pet store.

What are your New Year’s resolutions? What else can you do to provide a healthier lifestyle for your pet(s)? Let us know in the comments. Here’s to a happy, healthy, and prosperous New Year!

About the author:

Jennie is a veterinary technician who has nearly twenty years of experience in veterinary medicine. She graduated from Fairmont State University in 2006 with an AAS in Veterinary Technology. Since that time, most of her experience has been in emergency and critical care where she has worked alongside board certified specialists in surgery and internal medicine.

Photo by Erik Karits on Unsplash

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