Diagnosing internal parasites in cats

May 01, 2003

Table 1: Overview of selected internal parasites of cats
Most of us are aware that numbers of cats have surpassed dogs as pets in United States households. The same is true in many European countries. Even in countries where cats are less common pets than dogs, the numbers of cats appear to be increasing. As stated by Bowman and co-authors (Feline Clinical Parasitology, Iowa State University Press, 2002), "regardless of national boundaries, with the ever-increasing limitations of time, money and space, the cat is rapidly becoming the cosmopolitan pet of the 21st century". Interestingly, even with these evident trends, often little attention or effort is given to determining or defining prevalences, disease problems or control strategies for internal parasites of cats (See "Possble reasons why ...," p. 21). Many are unaware that cats and dogs often harbor different parasites that are sometimes acquired in different ways. More importantly, feline internal parasites may vary in their susceptibilities to available canine parasite control products, often requiring different dosages or regimens. This article addresses prevalences of feline internal parasites, perceptions of their importance (including zoonotic potential), and diagnostic techniques and control strategies. I also will suggest methods to increase accuracy and sensitivity of fecal diagnostic techniques. Perhaps an increased awareness of feline parasites, improved fecal examination procedures and a knowledge of feline parasite control products will enhance our capability to control major feline intestinal parasites.

Analyzing feline parasiteprevalence data Unlike dogs, few recent comprehensive internal parasite surveys have been conducted in cats. However, a review of available survey results indicates that the roundworm, Toxocara cati, and the hookworm Ancylostoma tubaeforme are the more common worm parasites. The feline roundworm usually ranks as the most common parasite recovered, regardless of the geographic region in which the surveys were conducted. This can be explained by the variety of routes by which T. cati can be acquired, and the capability of the embryonated egg to survive under a variety of adverse environmental conditions (Table 1, p. 17). The hookworm, A. tubaeforme, occurs with greater frequency and often predominates in areas where climatic conditions are mild - a reflection of the susceptibility of free-living larval stages to extremes of temperature and humidity.

Table 2: Selected feline internal parasiticides
Results of recent surveys provide interesting insights into prevalences of parasites in cats of different ages and habits (shelter animals vs. pet animals). A survey published by researchers at Cornell University reported prevalences of T. cati in shelter and pet cats less than 1 year of age. The overall prevalence of T. cati was 33 percent. As expected, the prevalence in shelter kittens (37 percent) exceeded that of pet kittens (27 percent). However, the latter rate of 27 percent in pet kittens reminds us that the feline roundworm remains a prevalent and potentially dangerous zoonotic parasite. Pet owners and some veterinarians are not aware that the feline roundworm can also be a significant cause of larva migrans, an ocular, visceral or neural disease of humans resulting from migration of ascarid larvae. We at Auburn University recently initiated a fecal survey of internal parasites of shelter cats in East Central Alabama. Results of our survey again support the predominance of T. cati and A. tubaeforme in the survey population. After completion of 52 fecal examinations from cats of different ages, T. cati eggs were observed in 23 percent of the samples. Ancylostoma tubaeforme eggs were recovered from 27 percent. We concluded that hookworm eggs were those of A. tubaeforme, because A. braziliense is restricted to the coastal areas of the southeast. As mentioned above, these prevalences reflect the capability of hookworm larvae to survive in the milder climates that prevail in the deep South. What is perhaps most surprising about our results thus far is that 8 of 12 cats that harbored T. cati and 11 of 14 cats that harbored A. tubaeforme were 2 years old or older. No differences in prevalence of these parasites were observed between spayed or neutered, and intact cats. Certainly, available prevalence data, limited as it is, should encourage veterinarians to be more aggressive in conducting fecal examinations on cats, and not to presume that these parasites occur too infrequently to deserve our attention.

The importance of fecal examination procedures Skill in the conduct and interpretation of fecal examinations is important if feline internal parasites are to be diagnosed accurately and effectively treated. The performance of reliable and accurate fecal examinations requires a knowledge of the procedures, a thorough familiarity with the important parasites of cats (see Table 1), and how to use this information in a reliable strategy. In this section, I will review in-clinic fecal examination procedures and make specific recommendations about improvements in the conduct and sensitivity of feline fecal examination procedures. In most cases, a few simple improvements will result in marked increase in sensitivity of tests and the diagnostic proficiency of clinic staff.