In search of fecal parasites—and a better way to find them
In order to ensure the health of our patients, screening for intestinal parasites has become a well-established and important part of routine preventive care. In small-animal practice, whipworms, hookworms and roundworms may be the most commonly encountered intestinal parasites in canine and feline patients.
The prevalence of infection with each intestinal parasite varies from region to region; infections tend to occur more frequently in shelter animals than in well-cared for dogs and cats that visit the veterinarian on a regular basis.1 Outdoor pets and those that consume prey with possibly infective larvae in their tissues are also more likely to be infected, but all dogs and cats are at risk.
The zoonotic potential of these parasites, most commonly roundworm and hookworm, is also a concern. To protect the health of both humans and pets, the Centers for Disease Control and Prevention (CDC), the Companion Animal Parasite Council (CAPC) and the American Animal Hospital Association (AAHA) each recommend fecal screenings 2–4 times per year during the first year of life and 1–2 times per year in adult pets.2, 3, 4 Immediate disposal of feces is also important to reduce the likelihood of reinfections in pets, as well as for the prevention of human infections.
Four drawbacks to the current diagnostic method
Currently, the most common method for diagnosing intestinal parasite infections is fecal flotation (fecal O&P), either passive or by centrifugation. There are many issues that may complicate the diagnosis of infections with this method.
- Misidentification: Pollen and other debris may be misidentified as eggs. In addition, the misidentification of eggs from other species because of coprophagy may also occur. One study researching this occurrence found that 31.5% of Toxocara-positive canine fecal specimens were in fact Toxocara cati eggs.5
- Choosing the best solution: Another common problem concerns the varying density of the different eggs, which makes it difficult for a clinician to select the ideal fecal flotation solution to ensure adequate recovery of eggs from all potential parasites.
- Identification during the prepatent period: Fecal flotation relies on identifying eggs, limiting the ability to detect infections during the prepatent period (the time in which adult worms infect a host before laying eggs) or when there is a single-sex infection because eggs are simply not present in the infected animal. Each of these parasites has a unique life cycle, with prepatent periods that range from 14–21 days in hookworms to 14–30 days in roundworms to as long as 74–90 days in whipworms. Prepatent parasite infections will go undetected by fecal flotation, increasing the chance for the appearance of clinical signs prior to evidence of eggs in the stool.
- Potential for false negatives: Fecal flotation may not always be reliable as a single test. Because many parasites shed eggs intermittently, a specimen from an infected animal may still generate a false-negative diagnosis if only a single fecal flotation is examined.
These reasons highlight the need for an additional tool to diagnose the most common intestinal parasites of dogs and cats. It also bears mentioning that in the busy, fast-paced environment of small-animal practice, the processing of pungent fecal specimens in-clinic with fecal flotation can be time-consuming and unpleasant for your staff. IDEXX Reference Laboratories offers fecal O&P testing by centrifugation and also has recently added enhanced diagnostic options for the detection of hookworms, roundworms and whipworms.
More fecal testing options
Antigen detection is routinely used to diagnose heartworm and Giardia infections, and now IDEXX Reference Laboratories has developed enzyme-linked immunosorbent assays (ELISAs) for the detection of hookworm, roundworm and whipworm antigens in feces. The fecal antigens are secreted from the adult worm rather than the egg, allowing detection of prepatent stages as well as overcoming the challenge of intermittent egg-laying. Early detection and treatment during the prepatent period will reduce the frequency of environmental contamination with potentially infectious eggs; it will also help to limit reinfection and infection of other pets and people.
Detect more infections
IDEXX tested a 1,000-member population of canine and feline fecal specimens for intestinal parasites using both fecal flotation by centrifugation and fecal antigen ELISA methods for hookworm, roundworm and whipworm. The IDEXX Reference Laboratories fecal panels, which combine both fecal O&P and antigen ELISA testing, detected more infections.6
Find more parasites earlier
In an experimental infection study, the fecal antigen ELISA was able to detect infection by hookworm, roundworm and whipworm during the prepatent stage. Below is a graphic example of the whipworm ELISA identifying an infection approximately 30 days before a fecal O&P test.7
In order to provide the highest standard of care in intestinal parasite screening, IDEXX Reference Laboratories offers fecal panels that combine fecal O&P and antigen ELISA testing for improved diagnostic accuracy. By detecting intestinal parasites earlier in the infection and overcoming the challenges of fecal O&P testing alone, you can now initiate more timely treatment and reduce risks to both people and pets.
There are many issues that may complicate the diagnosis of infections with fecal flotation (fecal O&P) . . . the most common method for diagnosing intestinal parasite infections.
Sarah Tasse, DVM
Dr. Tasse received her DVM from Colorado State University in 1997. After graduation she worked in a variety of small-animal private practices in both Colorado and New England. She joined IDEXX in August 2011 as a medical affairs marketing manager for Companion Animal Group, Rapid Assay.