Challenges in parasite management

Have you ever had one of those days when even the simplest case sends you to your reference library for a diagnostic or treatment review? When it comes to common parasites in cats and dogs, it can happen to anyone.

These cases can be frustrating to manage and challenging to explain to pet owners, who expect a simple deworming or a single flea treatment to have their pets cleared up and parasite-free.

Client communication: Taking the time to explain to clients how a parasitic infection develops, what expectations to have and the importance of treatment compliance is essential to producing a good outcome. (Photo: Dean Golja/Getty images)

There are two challenges here. The first is to manage the patient's medical condition. The second is to manage the client's expectations and experience so he or she is prepared as the treatment plan moves forward.

Multiple GI parasites in kittens

It is not uncommon to be presented with a kitten of unknown origin experiencing ongoing diarrhea. Often, these kittens are somewhat immunocompromised, either from concurrent viral disease or just malnutrition or neglect. Fecal analysis results can be positive for Giardia species, Isospora species, roundworms, hookworms, Cryptosporidium species or a combination thereof. Trying to identify which parasite is the root of the problem is difficult, and, in fact, it may be that the combination is resulting in the severity of clinical signs.

A standard diagnostic database including feline leukemia virus and feline immunodeficiency virus status, basic blood work, an external parasite examination and a centrifugal fecal flotation along with a Giardia species ELISA will help identify the range of concerns.

To satisfactorily resolve the diarrhea, communication with the client regarding an appropriate diet, the use of probiotics if indicated and the details of an adequate deworming schedule will be crucial. Inform clients that it may be necessary to have several fecal samples evaluated over a period of weeks or months, that they need to ensure that all prescribed medications are given in full as directed and that their pets should be kept apart from other household pets until the parasites are cleared. "Being transparent with your client and setting the proper expectations are critical," says Cathy Lund, DVM, of City Kitty Veterinary Care for Cats in Providence, R.I.

You might recommend products such as imidacloprid-moxidectin, emodepside-praziquantel, selamectin or others. Supplemental dewormers such as praziquantel-pyrantel pamoate, fenbendazole or pyrantel pamoate may be used between the monthly products to help clear parasites with shorter prepatent periods.

Although Isospora species infections are often self-resolving, severely affected kittens may benefit from sulfadimethoxine, which is primarily a coccidiostat used daily for 10 to 20 days at an oral dose of 50 mg/kg, or extralabel use of ponazuril, which is noted to be coccidiocidal and can be dosed at 20 mg/kg orally once daily for two or three days.

Don't forget to rule out infection with Cryptosporidium species and Tritrichomonas foetus if the diarrhea persists and traditional treatments are unrewarding or incomplete.

Occasionally, these kittens continue to experience diarrhea, even after their fecal test results are negative and they appear to be bright, active and healthy. They may have residual GI issues requiring ongoing dietary or supplement therapy until their systems fully recover. There is some discussion among experts that underlying viral disease may be damaging the GI mucosa and predisposing these kittens both to the parasitic infections and to ongoing diarrhea once the parasites are cleared. A PCR panel is available for both dogs and cats that evaluates a combination of parasitic and viral diseases. The canine panel includes Giardia, Cryptosporidium and Salmonella species; Clostridium perfringens enterotoxin A gene; canine enteric coronavirus; canine parvovirus 2 and canine distemper virus. The feline panel includes Tritrichomonas foetus; Giardia, Cryptosporidium and Salmonella species; Toxoplasma gondii; Clostridium perfringens enterotoxin A gene; feline coronavirus and feline panleukopenia virus.

Jay Stewart, DVM, a Companion Animal Parasite Council (CAPC) member from Aumsville Animal Clinic in Aumsville, Ore., reminds us that the key in these kittens is to give them time to stabilize their immune systems. Once a pet is stable, "tincture of time is often the cure," says Stewart. "So don't overwhelm the kittens with medications, but treat the most pathogenic parasites first (such as hookworms, which result in anemia), and provide a healthy diet."

Don't forget about environmental control as well, which includes fastidious litter box maintenance (cleaning with diluted bleach) and bathing cats after deworming treatments to prevent reinfection. This is also an ideal time to communicate the need for year-round, lifelong parasite control.

Chronic hookworm infection in dogs

These infections in dogs are frustrating for pet owners as well as veterinarians. Because the prepatent period is so short (two weeks), many monthly applied products will not clear a dog from a persistent infection or will allow the dog to become reinfected between doses. These dogs might be coprophagic, visiting a dog park or walking in a contaminated environment. They could also be experiencing larval leak, which involves constant migration of larva from the intestinal wall or tissues into the intestines, according to Susan Little, DVM, PhD, Dipl. EVPC, a professor of parasitology at Oklahoma State University's Center for Veterinary Health Sciences. Discuss these potential environmental issues with the owner, and work to eliminate any potential sources of reinfection.

If the dog is receiving a monthly heartworm preventive, then add an appropriate dewormer in between at the two-week interval at least twice for a total of four deworming treatments. Remember that many monthly heartworm preventives contain dewormers that will kill hookworms, but they do not prevent intestinal parasites. They only eliminate what is in the system at that time. It is heartworm disease they are preventing, by being used on a monthly basis, due to the extended prepatent period of the Dirofilaria immitis parasite. This concept is difficult for clients to understand and is worthy of a few minutes of your time to explain.

In addition, bathing dogs (wearing gloves) the day after the deworming and being fastidious about fecal cleanup in the environment may also contribute to treatment success since hookworm eggs are generally not as environmentally fastidious as roundworm or whipworm eggs. Of course, avoiding potentially contaminated environments may also be required to prevent reinfection.

Persistent canine whipworm infection

Whipworms have the longest prepatent period of the common intestinal parasites seen in dogs, lasting 74 to 90 days. In addition, Trichuris species ova can live for years in the environment, making it difficult to prevent reinfection in dogs.

A typical case might present as an adult dog with recurrent diarrhea. The dog improves after appropriate deworming treatment but returns to the clinic several months later and once again has positive results for whipworms. Clients can get frustrated and may not understand that the dog is getting reinfected and that the treatments probably are working.

Stewart recommends letting dog owners know that whipworms may need to be treated on and off for life in a dog that has access to a contaminated environment.

Using a monthly heartworm preventive with an approved whipworm treatment claim year round will help provide this type of patient with good control. The monthly treatment may limit the disease to a subclinical nature if the dog continues to get reexposed regularly by keeping the parasite load minimized.

Giardiasis, again?

There are several frustrating issues with Giardia species infection, including a pet that has a positive fecal or ELISA test result for Giardia species but that is exhibiting no clinical signs of the disease. The CAPC recommends treating these pets and any in-contact housemates with a single course of therapy. Then, if all pets continue to remain asymptomatic but still have positive test results, additional treatments are not warranted. Giardiasis is not considered to be a major zoonosis in the United States, so this a serious concern only in households with immunocompromised persons.

Fenbendazole dosed at 50 mg/kg or febantel given at labeled doses has the best efficacy against Giardia species and should be used once daily for five consecutive days. Treatment in combination with metronidazole (25 mg/kg twice daily for five days) can also be used, according to CAPC guidelines.

Little also advises environmental management, including clipping or bathing after deworming and identifying and cleaning up potentially contaminated water supplies to control ongoing problems with giardiasis, especially in kennel or shelter situations.

Roundworms making the rounds

"Not too long ago, I treated a household with three cats — two adults and a newly rescued shelter kitten — that repeatedly came up positive for roundworms on their fecal exams," Lund says. The cats were receiving monthly preventives and had undergone repeated deworming treatments with known effective medications but continued to shed roundworm eggs.

Lund recommended litter box cleaning, considered whether the cats were getting the appropriate dosages and finally achieved successful resolution. "I asked the owner to isolate the cats from each other and provide each with their own litter box, and I treated them monthly with imidacloprid-moxidectin and in between with pyrantel pamoate," Lund says.

As with other parasites discussed in this article, reinfection is a common issue, and creative management of the environment, as Lund noted, is often needed to achieve successful resolution of the disease.

Fleas, fleas, fleas

With the plethora of available and effective flea prevention and treatment products on the market, it may be surprising that this parasite found a place in the current discussion. However, it continues to be one of the most common parasites that veterinarians and clients struggle to manage effectively.

Potential reasons behind this difficulty may include:

> Confusion about the available products

> The standard monthly application recommended for a parasite whose life cycle is closer to three weeks than to four weeks

> Noncompliance by clients in application protocol

> Veterinarians failing to spend the necessary amount of time with clients discussing fleas and flea control.

"Having protocols in place in your hospital for diagnosis, treatment and control of parasitic diseases is as important as having them for vaccinations or any other disease veterinarians manage," Stewart says.

The owner of a cat with flea allergic dermatitis who doesn't comply with flea treatment recommendations may not realize that fleas are not the result of having a dirty household or even from the cat going outside. In fact, another pet or even the owner could be bringing fleas in to the house and, while the owner may never see an actual flea on the cat, it may be grooming them off while chewing on itself.

Having a frank discussion with the cat owner and explaining the need for monthly, year-round flea prevention will go a long way toward resolving this pet's discomfort.

According to Little, many of the pets with chronic flea problems are actually getting reinfected. The owner is failing to treat effectively, and the result is a pet not only with fleas but also potentially with ongoing tapeworm issues.

So what are the issues you need to address in the frustrating flea cases? Sit down with the pet owner, and use the following checklist to identify any potential gaps in prevention:

> Is the product being administered at the recommended interval? (Check the client's purchase history to help identify gaps.)

> Is the product being given properly (i.e., on the skin and not on the hair for a topical; actually ingested vs. being spit out for an oral)?

> Is the dosage correct? Is the owner sharing product between pets?

> If using a topical product, what is the pet's water immersion history (e.g., frequency of swimming, medicated baths)?

> Are all household pets being treated, including the outdoor cat that eats on the porch?

> If using a topical, is the product actually being applied? Is the tube properly opened?

In persistent cases, you may also want to discuss environmental management (treating the house and yard).

Parting advice

"Don't forget about regional differences," Stewart says. "Taking a good history is just as important in parasitic disease management as it is for everything else we treat."

Lund recommends year-round parasite control for her feline patients regardless of their indoor or outdoor status and has her staff trained to communicate this message to clients. According to Lund, prevention is simply better healthcare for cats and dogs.

Silene Young, DVM, is a freelance medical writer and editor in Costa Mesa, Calif.