Parasite prevention (fleas, ticks, heartworm)

1. Introduction 

The greatest concern most people have regarding their pet is whether they are feeding them the right diet and have them on a regular schedule for medical check-ups. These are very important things, but what many pet owners do not consider are their pets' exposure to parasites. Pets that live outdoors should make at least two (some authorities recommend more frequent) visits to a veterinary clinic for a stool check and appropriate wormer. Medications are currently available that can be administered annually or at a veterinarian's recommended intervals for the control of certain parasites. Some are relatively safe, effective, and can save the pet owner the unpleasant chore of worming the pet. The gastrointestinal parasitic problem in companion animals is significantly higher than in those of human beings.

The ascarids or nematodes include the roundworm of the dog and cat; the hookworm of the dog and cat; the whipworm of the dog; and the hyostrongylus species that is also seen in the dog, cat, and other hosts in other areas etc. Roundworm eggs and hookworm eggs are the most common nematode ova seen in the stool of cats and dogs. Treatment with a hookworm preventative is a must in the dog in many parts of the world. The problem with toxocara infections in the dog is not adult parasites, but the migration of larvae of the parasite that can occur in the puppy. The whipworm egg is found in nearly all warmer climates but may not be seen in dry areas.

2. Common Parasites Affecting Pets

With the exception of heartworms, all of the most common internal and external parasites pose a zoonotic risk—meaning that both people and pets can become infected. This can be a concern for individuals with immunodeficiency issues, such as those with HIV, for young children, for those undergoing chemotherapy or radiation treatments, and in third-world or overpopulated areas. Parasites can cause significant health issues, resulting in millions of lost work-days each year. They can also cause significant issues for pets, such as causing anemia in hookworm infection, severe diarrhea with roundworms, and lung diseases in both dogs and cats with lungworms.

The most common internal parasites are roundworms, hookworms, whipworms, and tapeworms, while the most common external parasites are ticks, fleas, mosquitoes, and lice. Ticks not only transmit Lyme's disease, Rocky Mountain Spotted Fever, and Ehrlichiosis, but can also transmit other diseases such as Anaplasmosis, Hepatozoonosis, and transmit tick paralysis. In addition to causing Flea Allergy Dermatitis, fleas can also transmit Bartonella, the tapeworm Dipylidium, and Mycoplasma. Heartworm is the most lethal of these parasites but it is preventable with a once-monthly medication.

2.1. Fleas

It is rare for a pet to live its entire life without suffering from at least one parasite. The list is extensive, and apart from direct discomfort to the pet, some of these parasites also have zoonotic potential (can be transmitted directly or indirectly to humans). Prevention is a full-time job, but with such a variety of effective products to choose from, the task is made much simpler. Preventive therapy should not be reserved only for animals in a household that are "on show," but should be applied to all domestic animals and especially to those who can be expected to wander beyond the premises.

Fleas are one of veterinary practice's most frequent visitors. Once-in-a-while itchers are common visitors to veterinary clinics; sometimes biting the owner until blood is drawn while the reason for the pet's scratching is promptly dealt with. Ectoparasitism (parasites living outside of the host) is a direct source of discomfort to the pet. However, in certain animals, a dramatic loss of condition and anemia may follow heavy infestations. In heavily infested pups and kittens, particularly small cats, an infestation with cat and dog flea Ctenocephalides canis and C. felis is frequently accompanied by the closely related rabbit flea, Spilopsyllus cuniculi.

2.2. Ticks

Ticks are tiny, spiderlike, egg-shaped creatures that are found in many areas of the world, especially in brushy and wooded areas. Adult ticks bite onto the skin of warm-blooded animals and gorge on blood. A female tick can increase its body size many times by taking in blood from a host. Depending on the species and environmental conditions, the development from egg to adult tick takes about a year. The two most common types of ticks are the American dog tick and the deer tick (or blacklegged tick). Ticks can transmit deadly diseases, such as Lyme and Rocky Mountain spotted fever, so prevention is key.

Signs of tick infestation: If your pet has adequately been treated and developed sudden paralysis, a tick may be the cause. The neurotoxin in the saliva of some female ticks causes paralysis. However, in North America, it is most often a problem in the western United States. It is not common in dogs in general, and it occurs once every few years. Tick paralysis can occur with or without the presence of a known tick, so be sure to check your pet thoroughly for ticks. Your pet will usually fully recover after the tick is removed.

2.3.  Heartworm

Feline heartworm infection is seen in most parts of the United States, especially in areas with high mosquito populations. Heartworm infection in cats can cause chronic signs such as coughing, rapid or difficult breathing, weakness and listlessness, collapse, occasional vomiting, lack of interest in food, and even sudden death. Cats with heartworm infection may have only very vague signs of illness or at the time of sudden death, there may be no previously detected symptoms. An exact diagnosis can be made in a few cases where the adult heartworm is found. More often, diagnosis is based on a combination of history of exposure, clinical signs, and additional testing such as chest x-rays, echocardiography, and possibly blood tests. Cats do not end up with adult heartworm very often, but those who do can remain ill or die from symptoms of heartworm disease.

Prevention of heartworm disease in areas at risk of heartworm infection is always the best way to protect cats from heartworm disease. If it is clear that cats are at no risk for exposure to heartworm, then prophylaxis can possibly be discontinued. Cats that have previously traveled to an area at risk should receive heartworm prophylaxis and be re-evaluated if they have not received prophylaxis when they return. If a dog with heartworm immunocytes visits your home, it should not be a concern that it is a possible flea carrier. The way to get rid of the flea and heartworm preventive immunocytes should be continued.

3. Preventative Measures for Parasite Control

Parasite preventatives for both endo- and ectoparasites are available for pets. Pet owners are advised to establish a sound relationship with their veterinarian, wherein they can discuss the needs of their pet and come to a mutually agreeable plan of action. This chapter gives an overview of the different classes of anti-parasitic products used to prevent infestations of small animals with internal and external parasites. It describes the mode of action, recommended dosage, and route of administration. Then, the appropriate active substances per parasite species are reviewed. Whether parasite preventatives exert unwanted residues in food is discussed, and finally, the development and registration of those products are detailed.

Ultramicroscopic magnifications and descriptions of parasitic stages of common intestinal parasites of dogs and cats, which are currently known as genera or species with zoonotic potential. These pictures were made "on the bench," and they provide guidance to veterinarians, veterinary students, and pet owners when students are shown parasites during training sessions or when complaints involve veterinarians. No claim for clinical relevance is made in this chapter; particularly young life stages are considered to be less pathogenic.

3.1.  Regular Veterinary Check-ups and Parasite Screening

Taking your pet to a veterinary check-up is necessary for detecting diseases from the early stages. This is also the time to check for intestinal parasites, so having stool samples checked is a type of regular pet ownership responsibility.

The majority of pets come in for checkups, and vets find parasites that need medical care. Therefore, you should resist saving time or money by self-medicating. Many products are not appropriate for your pet or don't work correctly.

Parasites are sometimes difficult to detect. Even though your pet is suffering from parasite diseases, you still cannot find them in the feces/grass on your pet's back because animal fur is not easy to find or easily visible from where you're standing. These diseases can also take a few weeks or months to heal.

To protect your pet's life and health and prevent symptom manifestation, regular veterinary visits (at least once a year) are essential. At such times, the opportunity to verify that your flea/tick/parasite treatment strategy is still valid. If there is no prevention, the vet can provide advice or change the treatment strategy.

3.2. Environmental Management and Hygiene Practices

Environmental management and hygiene practices are an integral part of integrated parasite management protocols because they help to reduce the environmental contamination of parasites, and this may contribute towards reduced parasite exposure levels. The aim is to manage the immediate environment to create a less favorable environment for the parasites and thus help disrupt their life cycle.

The use of anthelmintics has led to the development of resistance by many parasites, so their use must be conducted carefully and monitored regularly. In order to maintain good efficacy, it is important to administer the correct product at the appropriate dose and frequency, and this will often require veterinary advice. Underdosing and poor techniques for administration are some of the reasons why a product may fail. If this occurs, the owner should consult the veterinarian or parasitologist for advice on how best to proceed. If an animal is overdosed, the results may be detrimental, causing an increase in the number of resistant strains.

Some compounds must be used with care in given physiological situations. For instance, there are limitations on the correct use of some compounds, and anthelmintics are contraindicated in puppies and kittens less than 2-3 weeks old and in very weak or severely debilitated animals. It is important to observe periods of withdrawal after treatment with some compounds, particularly when used in sheep and goats for the treatment of external parasites, if they are to be slaughtered for meat. In addition, there are icing periods required for lactating animals if using compounds prone to passing into the milk. Dosage, frequency of administration, and periods of withdrawal are some of the key elements to monitor carefully.

3.3.  Use of Preventative Medications

Use preventative medications properly and consistently to lower the risk of parasites. Many veterinary offices have entire lines of parasite treatments which can be prescribed or sold. They include medications for internal parasites, such as heartworm and intestinal worm infestations, and external parasites, such as flea and tick infestations. Some are available over the counter at pet stores.

What kind of preventative medication use will be best for a pet? If a pet has had infestations before, he will need to take his medications more frequently in the future. High-risk pets, in that case, may need medications all year. Talk with a veterinarian for the best advice. Use the medications as directed, once advised to start them. Year-round; the leading cause of heartworm infestation failure is skipping a dose to re-start during the right season. The threat is present unless it is winter enough at temperatures below 50 degrees F.

Never administer a preventative medication for a cat for a dog. Medication, whether it be an oral pill or a topical treatment product, could have severe side effects, or it may not work at all. Store all parasite prevention medications and drugs in a safe, locked cabinet that can't be reached by kids or pets. Keep them in their original package. If any of them have become stale, never use them.

4. Types of Parasite Preventative Medications

4.1 Spot-on Parasite Preventatives

This type of treatment is applied directly to the animal's skin, usually along the back and/or neck. It is then rapidly absorbed and spreads across the animal's body. It usually contains a combination of ingredients that kill or disrupt life cycles of a broad range of parasites, protecting them for up to several months. This includes preventing flea eggs from hatching within the animal's living environment. This is especially good for pets that are difficult to medicate.

4.2 Oral Medications

Called antiparasitic drugs, these are taken by mouth. They generally have a moderate duration of action compared to spot-on treatments. There are many different types of anti-internal parasite (worm) medications available, and each one targets a particular group of parasites often found in a cat or dog. Be sure to read the label for the specific pests that the product targets. Be warned that dogs may dislike the taste of some worm medications, so do your homework! Some worm medications include humans, which is a good thing.

4.3 Shampoos and Dips

There are many types of medicated shampoos and dips, from standard shampoos that will remove parasites which are already on your pet to dips that will provide a more long-term preventative treatment (but will need fairly regular re-applications). Keep in mind that the use of any foreign substance may not be suitable for pets with open wounds or other skin conditions, so consult your veterinarian before using any treatments.

4.4.  Flea Preventatives

In terms of parasitic diseases, many pet disease conditions can be prevented using modern drugs that are safe, effective, and quite easy to give. There are blood-sucking ecto-parasites, including fleas, ticks, lice, and the mange mite, and helminths or intestinal worms. These are most commonly roundworm, hookworm, whipworm, and tapeworm. More rarely, tapeworm infections are caused by ingestion of infected fleas or lice during grooming. Efficacious drugs are available to prevent fleas, ticks, lice, and sarcoptic (dog) or demodectic (dog) mange. In general, monthly or 12-weekly control is pretty good for these drugs.

It is often the product used to control fleas that gives the best control of lice and mites. The half-life of these products means that they often inhibit any re-population once treatment has developed – it is one way that modern flea control and eradication now differs from classical casual-based sprays. Also, there is a second-generation insect growth regulator that inhibits the development of the egg, larvae, and pupal stages in the environment, which also stifles any attempts by the parasitic population to re-colonize its hosts. However, these products do not work against ticks – hence the two classical administration systems of an injection to control ticks and a collar to control fleas. If the fleas avoid the area of the collar, they can re-colonize the dog – and if this re-colonization occurs early enough, the duration of the treatments and their anti-parasite protection can be substantially shortened.

4.5. Tick Preventatives

Some pets get ticks from their environment just by walking through tall grass or near woods. Ticks may not be a big concern for a pet that never leaves paved areas, but they are a real health risk if a pet can venture into the woods, fields, or other wild areas. Ticks are known vectors of a range of zoonotic diseases, so they can pose a risk to human health as well as the health of a pet. If you live in an area where tick-borne diseases are a danger, or if you and your pet tend to spend time in areas where ticks are known to be a danger, make sure you put your pet on a tick prevention protocol. Tick prevention options include oral, ointment applied, and collar-based treatments. Look into the options to find what is right for your pet, and remember that collars may not be ideal for pets with little ones at home who may spend time on and around their pet.

4.6.  Heartworm Preventatives

Remember, heartworm preventatives are prescription medications, so your pet requires a yearly examination with your veterinarian before you can pick up a refill. You need a prescription in order to purchase this type of preventative medication. Additionally, the medication does not prevent parasites or fleas, so your pets will continue to need other preventative measures. Also of note, during the heartworm test, the veterinarian draws blood and looks for baby larvae (microfilariae). If the mosquito kept up the good work and transmitted the larval stage to your pet, then medication can be toxic. That's why it's so important to get your pet regularly checked with the veterinarian.

However, like flea and tick preventatives, heartworm preventatives are an essential key to preventing a potentially fatal disease and protecting pets against other harmful parasites. There are many options available, all administered either by a top-down or oral method. Some of the prescription oral preventatives are tablets or chews. They are generally given once a month and started around 6 weeks of age, some even earlier depending on when the mosquito season starts. Which medication is best for your pet also depends on your location and when you travel. Resist the urge to save money and buy these medications from an online retailer, and do not give preventatives to your pet intended for other pet species. Double-check with your veterinarian before starting your pets on any medications. Consider using a flea and tick preventative in addition to preventatives for heartworms. This prevents multiple parasites at once, helping to keep pets on a tightly spaced treatment schedule and causing fewer missed doses.

5. Administration and Dosage Guidelines for Preventative Medications

The most common routes of administration for preventive medications are oral and topical, but some can be injected as well. Administering medications orally is easiest when using flavored chewable tablets, which are often designed to mimic the taste and texture of common canine and feline treats. Tablets will be curliquids may be flavored and designed to be administered on their own or added to the animal's food. Injectable prescriptions are liquids that may be an appropriate choice for animals with chronic conditions or poor lipid absorption that oral and topical medications sometimes have. For many pets, such as active dogs, injections may be the most practical method of monthly parasite prevention. Injectable prescription medications often provide a longer period of protection from parasites and need to be stocked more frequently.

Regardless of which method of administration you choose, it is essential to ensure that your pet receives the correct dose at the right time. Dose sizes vary by weight and sometimes age (for puppies and kittens), so many parasite-control products are sold in multiple-sized packages that include several pre-measured doses of the medication to make the appropriate administration easy. If the weight of the pet is on the border between two sizes, it is always better to select the larger size to avoid the possibility of underdosing your pet. Your veterinarian performs a full examination of your pet at every visit, effectively evaluates its health status and clinical presentation, and helps you decide to use the preventative that is right for pets. They may also offer to provide heartworm tests and other laboratory tests at the time requested. Any checkups and testing should be discussed in more detail with your veterinarian before any visit.

6. Combination Products for Multi-Parasite Protection

Some owners might find using a single product quite complicated. They may prefer to use a single product that prevents both internal and external parasites. Thankfully, many veterinarian-recommended combination products prevent a wide variety of both internal and external parasites, which include both oral and topical products. It is important to note that combination products may vary within one particular country or in different countries.

Depending on the combination parasites under prevention, these combination products can prevent several of both internal and external parasites that include fleas, ticks, mosquitoes, sandflies as vectors of Leishmania. Some medications can also work on an intestinal roundworm, blood, and heartworm, ear mites, and sarcoptes mites. There are oral medications for dogs that can act as flea and tick medication, intestinal parasite prevention, and heartworm prevention. On the other hand, there are topical medications for dogs and cats that are flea, tick, and mosquito prevention and also work for Sandfly and for Leishmania parasites. However, the efficacy of these combination products may vary depending on the pet owner's veterinarian approval. Always be sure to consult with a veterinarian for the best and safest combinations of products to use for parasite prevention for your pets.

Ultimately, there is no correct option for every pet. The best product for your pet may vary depending on your veterinarian's recommendation and your pet's particular lifestyle. Different parasites and infections are relatively less or higher in each different area. This comprehensive guide fully provides you with sufficient information needed to monitor or prevent parasites, but this alone can't replace professional medication recommendations and the regular check-ups of a veterinarian. Complete monitoring while using parasite prevention medications can keep your pet safe from all kinds of parasites.

7. Natural and Alternative Approaches to Parasite Prevention

While we have decidedly focused on medication as a primary means of parasite prevention, there are some more holistic and natural ingredients and methods that can be employed to boost your pets' immune systems and make them less amenable hosts to most common parasites. Probiotic-rich foods are essential in a strong immune response as the gut is the largest immune organ in the body. Foods rich in antioxidants, vitamins (especially A, C, and E), and minerals such as copper, zinc, selenium, and iron are important to maintaining a healthy immune response. Various types of so-called "superfoods" are a good choice to include in your pets' diets for immune support. Liver (a few bites, not an entire meal), shellfish, wild-caught salmon oil, turmeric, brewer's yeast (not in yeast-allergic dogs), olive oil, papaya, and chamomile can also be used to support animals naturally. Maintaining optimal health through feeding a high-quality, species-appropriate food designed for your pets' needs will also aid in boosting and maintaining immune health and reduce the risk of host-parasite imbalances. It is important to recognize that while these foods may help in prevention, they are not substitutes for prescribed medication protocols.

In addition to these foods, there are natural supplements that can be used topically in the fight against parasites. Many common parasites, including fleas and ticks, are deterred by the strong smell of garlic and the taste of brewer's yeast. Adding brewer's yeast to your pets' meals will deter most external parasites, and even some internal. The presence of garlic will help deter those internal parasites as well. There are also specialty-made garlic and brewer's yeast supplement chews that your pet can take. Another option is to use topical essential oils to deter parasites residing in or on the fur and skin. Adding a few drops of high-quality essential oils such as neem, citrus, geranium, rosemary, peppermint, sage, cinnamon, or lavender to a spray bottle with water can make up an easy-to-use repellent that can be sprayed on your pet prior to walks or outings as a more natural repellent. Make certain to shake the mixture well before using as oils often sit on the top.

Just as with medications, before using or starting any new dietary or supplemental regimen, consult a holistic or integrative veterinarian or discuss with your pet's primary care provider to discuss special considerations for your pet.

8. Vaccination as a Preventative Measure for Specific Parasites

Vaccination programs for dogs and cats have led to the virtual elimination of several well-known diseases, such as canine distemper and rabies. Vaccination for a few other diseases, for which the owners wish greater protection, would help to prevent significant problems. A few animals and emergent conditions do require vaccination. The canine vaccines currently in use are typically produced via the inoculation of laboratory animals with attenuated virus or with virus grown under altered cultural conditions (i.e., altered temperature). The viruses are inactivated and then diluted to appropriate concentrations just prior to packaging. Cats respond well to vaccinations, especially to those vaccinations that can be given orally or via the use of an intranasal route. However, cats do have a few more problems with vaccinations, particularly to some of the non-protein carriers used in adjuvants, than do dogs.

Dogs are generally vaccinated at six to eight weeks of age, then every three weeks thereafter until they are sixteen weeks old. Dogs do respond better to occasional reimmunization than to frequent re-immunization. Originally, annual vaccinations were recommended as a method of providing yearly exposure to the basic antigens. However, the increased amount of problems seen relating to allergies, anaphylaxis, and vaccine-induced immunosuppression has caused a move away from annual vaccinations to a move towards the use of three-year vaccination programs. Only a few vaccinations are given more frequently. All dogs that have not had appropriate previous immunization histories should receive two vaccinations once they have become adults.

9. Emerging Trends and Technologies in Parasite Prevention for Pets

Understanding and defining the key reasons preventive care is not utilized more rigorously, and making these products and services accessible to a majority of pet owners, should be primary objectives of the companion animal healthcare industry. It is understandable that pet owners forget to deworm their pets or skip dosing, especially if the pet is showing no clinical signs of a parasitic infestation such as diarrhea, vomiting, decreased food consumption, and other digestive problems. This is the first key reason why we should encourage pet owners to adhere to the preventive treatment and encourage more and better user-friendly technology.

It is understandable that pet owners would prefer to leave the responsibility of preventive treatment with a veterinarian, as the veterinary staff can tag the scheduled next dosing event with reminder postcards or recall clients with email or telephone reminders. It is also understandable that pet owners would like to have an automatic treatment system. Wouldn't it be great if the pet's environment could be treated when the pet is out of doors? Or perhaps a treatment system in which the pet could voluntarily seek out a treatment station located somewhere in the home or in the homeowner's garden and initiate treatment would solve the problem? This is not just a pipe dream, and such a system is currently in development. It is undeniable that the capability and expertise of individuals involved in parasite control constitute a long-term trend to improve companion animal welfare.

10. Importance of Consistent and Year-Round Prevention

All pet owners recognize the value of preventing illness in their pets. Regular vaccinations protect against diseases like rabies or parvovirus. Some dogs and cats receive regular deworming against common parasites like roundworms or tapeworms, especially if they hunt or live in rural areas. Many pet owners do not recognize the importance of consistent and year-round prevention for a variety of parasites present in our environment. These parasites can cause dangerous infections that are easily transmitted to humans. Prevention is easy and cost-effective with the large variety of preventive treatments currently available.

Several parasites, such as ticks, are associated with specific times of the year, such as summer or spring. Many pet owners mistakenly believe they can discontinue parasite prevention once cold weather arrives. Several parasites can remain active in cold temperatures and can present a risk to pets and people. For example, the tapeworm Echinococcus is present in the northern United States and Colorado and is closely associated with coyotes. These predators can deposit eggs in the feces near all human settlements. These eggs can survive for several months in the environment. Dogs and cats will ingest these infected eggs by eating contaminated dirt or grooming their feet. Humans become infected with Echinococcus by accidentally ingesting the eggs while handling their pets, preparing or eating food, or through exposure to the contaminated environment. Casual exposure during travel is very likely.

11. Debunking Common Myths and Misconceptions about Parasite Prevention

Myth #1: Parasite prevention is difficult, expensive or time-consuming. The truth is, giving your dog or cat a monthly oral or topical medication costs only pennies a day and takes less than a minute to administer. Improved parasite control has eradicated most of the previously common pet- and people-related problems associated with parasites.

Myth #2: Fleas and ticks go away during the winter months. Simply put, fleas and ticks are there, just waiting for the right moment to hop on your pet. Winter or warmer season, year-round prevention is key. Why take a chance? There are many monthly medications which control fleas and ticks that make prevention easy.

Myth #3: My pet always stays inside so they don't need parasite prevention. Studies indicate that indoor pets are also at risk. Although your pet may stay inside, it only takes walking through a flea-contaminated area to become infested. Fleas also love to hitch a ride on owners into the home and their eggs can be deposited in the home's living spaces.

12. Conclusion and Future Directions in Parasite Prevention Research

In order to provide comprehensive parasite prevention programs, veterinary professionals need a clear understanding of an individual pet’s risk of parasite infection, the severity of an infection if one were to occur, and the benefits, risk, and practicality of the available parasite control options so that recommendations are tailored to the unique characteristics of the pet-owner pair. In this light, the objectives of this paper are to describe: the threats to good health in the pet population posed by parasites, the parasite species which pose the greatest health threats worldwide, the six primary categories of parasites, the various methods that are recommended to prevent parasite infections in pets, the general pros and cons for each method, and the potential problems that pets and pet owners experience. Improving adherence to these recommendations will require a combined effort from manufacturers, veterinary professionals, and pet owners, and future development of effective, practical, and accessible prevention products. Some suggestions for future studies are offered, as is a practical research framework to help guide the development of new products.

Different preventative methods can – and should – be used for different health alerts. The objectives of this review are: to describe the threats to good health in the pet population; the parasite species of most concern; and the recommended methods to prevent infections. Assessment of which parasite prevention products are best for which individual pets requires an understanding of the risks of infection; the parasite prevention options available, including their pros and cons; and which type of prevention use will be a "good fit" with which type of pet owner.