Despite the abundance of readily-available and easy-to-use parasite-control products, intestinal parasite infections remain common in companion dogs.
According to Dr. Jason Drake, DVM, DACVM-Parasitology, Elanco Animal Health, factors that contribute to intestinal parasite infections in dogs include:
- Pet parents who do not take their dogs to the veterinarian regularly (or at all)
- Pet parents who are not fully compliant with treatment recommendations (not using products properly or not using them year-round)
- Untreated or improperly treated dogs contaminating public places like parks
- Exposure to wildlife (e.g., foxes, rabbits, squirrels, rats, coyotes, wolves)
“Additionally, pet dogs on quarterly or monthly parasite control programs may not be on product combinations that cover all common parasitic risks,” Drake says.
To complicate matters further, tapeworms and whipworms can be difficult to diagnose with traditional diagnostics. So what’s the solution? Let’s take a closer look at the limitations posed by passive flotation fecal examination, how to test for worms in dogs, and effective methods for protecting against parasites
Diagnosing Intestinal Parasites: Fecal Flotation Limitations
Providing routine intestinal parasite screening and offering broad-spectrum parasite protection products is good for the health of pets, as well as the veterinary clinic’s bottom line. The Companion Animal Parasite Council recommends that all pets be tested and protected year-round for internal and external parasites.
Although passive fecal flotation remains common practice in veterinary hospitals for detecting parasite infections, this diagnostic tool has significant limitations.
In a recent study, published in the journal Veterinary Parasitology, an alarming number of intestinal helminths in dogs were missed using traditional, passive flotation fecal examination (1).
To carry out the study, a team of researchers (which included Drake) examined the contents of the entire gastrointestinal tract of 97 naturally infected adult dogs.
Fecal samples from each study dog were examined by passive flotation with sodium nitrate solution and centrifugal flotation with sucrose solution. Fecal antigen detection assays were used to detect the presence of nematode antigens in frozen fecal samples from 92 dogs.
Approximately two-thirds of the dogs in the study were infected with nematodes, and more than half were infected with tapeworms. “While these were dogs from an animal shelter, this is representative of what dogs are exposed to, and can be infected with, if not routinely dewormed,” Drake says.
The most common intestinal helminths found were Dipylidium caninum, Ancylostoma caninum, and Trichuris vulpis. According to the study, fecal flotation alone failed to detect as many as 15.6 percent to 93.7 percent of infections with intestinal helminths, depending on the species.
Approximately 96 percent of Dipylidium caninum tapeworm infections and 86 percent of Taenia spp. tapeworm infections went undetected in the study dogs. “The majority of tapeworm infections were missed by diagnostic methods used by most veterinarians and diagnostic laboratories,” Drake says. “Existing testing technology is not good at detecting tapeworm infections.”
One-third of whipworm infections in the study dogs were also missed by passive flotation fecal examination.
Another study, which was published in the journal Veterinary Therapeutics, looked specifically at the accuracy of passive fecal flotation testing, commercial assay, and various centrifugation techniques and three common flotation solutions to identify helminth eggs and oocysts from canine feces. The study concluded that passive fecal flotation testing was less accurate than centrifugation, especially when proper technique for fecal flotation is not followed (2).
The bottom line? “Veterinary hospitals utilizing traditional passive flotation techniques are missing many parasitic infections,” Drake says. “Utilization of centrifugation techniques can improve sensitivity of fecal examinations.”
Fecal Flotation Pitfalls
Common misconceptions about fecal flotation tests may lead to false negatives in the clinic. According to Drake, here are some missteps veterinary staff should be aware of:
Not using enough feces: Most fecal diagnostic techniques require at least 2 to 3 grams of feces for testing. However, fecal loops, which are commonly used for obtaining fecal samples in veterinary hospitals, only obtain about 0.1 gram of feces.
Relying only on passive flotation: Although passive fecal flotation is the more common in-clinic test, centrifugation is far more sensitive. Adding fecal antigen testing in addition to centrifugal flotation from a diagnostic laboratory can further improve sensitivity.
Not understanding the rate of false negatives: “Currently available clinical tests for tapeworms are terribly inaccurate,” Drake says. “Tapeworms are very difficult to find using flotation or even centrifugation techniques.”
Identifying Intestinal Parasite Infection in Patients
The ideal method for diagnosing parasites depends upon the kind of parasite you are looking for, Drake advises. “The most accurate testing for common GI nematodes like whipworm, roundworm, and hookworm performed within the hospital is centrifugation with modified Sheather’s solution,” he says. “IDEXX Laboratories has also recently commercialized fecal antigen tests with high sensitivity for whipworm, roundworm, and hookworm.”
When looking for Giardia spp. in a dog with diarrhea, centrifugation with zinc sulfate may be a better option, he says.
“Sedimentation is better for heavier parasite ova,” he continues, “while the Baermann technique improves sensitivity of many lungworm larvae like Crenosoma vulpis and Angiostrongylus vasorum.”
Broad-Spectrum Parasite Protection
The fact that diagnosis of intestinal parasites is often difficult serves as an important reminder for veterinary staff to speak to their clients regularly about year-round, broad-spectrum parasite protection.
Since tapeworms and whipworms are common in dogs but difficult to diagnose, Drake recommends parasite control programs that include a monthly treatment for both tapeworms and whipworms. While some heartworm preventives or dewormers treat hookworms and roundworms, tapeworms and whipworms are only covered by a select few products, such as Interceptor® Plus (milbemycin oxime/praziquantel).
Protecting dogs from external parasites is also key for helping prevent parasitic diseases, Drake stresses. An oral product like Credelio® (lotilaner) can be prescribed to kill adult fleas, treat and prevent flea infestations, and treat and control tick infestations in dogs.
See important safety information for Interceptor® Plus and Credelio® below.
“Good parasite control keeps pets comfortable and healthy, and allows pet owners to take their pets with them around town and to parks with the reassurance that their pets are well protected against parasites they are likely to be exposed to when going to places frequented by dogs and wildlife,” Drake says.
While parasites have always been an issue for pets, parasitic threats are rapidly evolving and showing up in new areas, Drake warns. “Even areas with a history of low parasite risk are seeing significant increases in parasite prevalence, putting all dogs at increased risk,” he says. “Adoption of parasite control protocols which include external parasite protection and internal parasite protection, including tapeworm coverage, is key for allowing dogs to enjoy the active lifestyles we see today.”
Disclaimer: The author received compensation from Elanco US Inc., the maker of Interceptor Plus and Credelio, for her services in writing this article.
Credelio kills adult fleas and is indicated for the treatment and prevention of flea infestations (Ctenocephalides felis) and the treatment and control of tick infestations [Amblyomma americanum (lone star tick), Dermacentor variabilis (American dog tick), Ixodes scapularis (black-legged tick) and Rhipicephalus sanguineus (brown dog tick)] for one month in dogs and puppies 8 weeks of age and older, and weighing 4.4 pounds or greater.
Credelio® Important Safety Information
Lotilaner, is a member of the isoxazoline class. This class has been associated with neurologic adverse reactions including tremors, ataxia, and seizures. Seizures have been reported in dogs receiving this class of drugs, even in dogs without a history of seizures. Use with caution in dogs with a history of seizures or neurologic disorders. The safe use of Credelio in breeding, pregnant or lactating dogs has not been evaluated. The most frequently reported adverse reactions are weight loss, elevated blood urea nitrogen, increased urination, and diarrhea. For full prescribing information see Credelio package insert.
Interceptor® Plus Indications
Interceptor Plus is indicated for the prevention of heartworm disease caused by Dirofilaria immitis and for the treatment and control of adult roundworm (Toxocara canis, Toxascaris leonina), adult hookworm (Ancylostoma caninum), adult whipworm (Trichuris vulpis), and adult tapeworm (Taenia pisiformis, Echinococcus multilocularis, Echinococcus granulosus and Dipylidium caninum) infections in dogs and puppies six weeks of age and older and two pounds of body weight or greater.
Interceptor® Plus Important Safety Information
Treatment with fewer than 6 monthly doses after the last exposure to mosquitoes may not provide complete heartworm prevention. Prior to administration of Interceptor Plus, dogs should be tested for existing heartworm infections. The safety of Interceptor Plus has not been evaluated in dogs used for breeding or in lactating females. The following adverse reactions have been reported in dogs after administration of milbemycin oxime or praziquantel: vomiting, diarrhea, depression/lethargy, ataxia, anorexia, convulsions, weakness, and salivation. For full prescribing information see Interceptor Plus package insert.