Clinical signs of feline roundworm infections may include an enlarged abdomen, a failure to thrive, vomiting, and diarrhea.
Low T. cati worm burdens can result in low egg numbers in feces, so an accurate diagnosis requires that fecal flotation procedures be
performed properly. Furthermore, T. cati infections are not restricted to kittens. In a survey I conducted, 23 out of 27 cats infected with T. cati were 2 years old or older; 10 out of 27 were 3 years old or older.
Figure 2 Anterior end of Toxocara cati (roundworm). The broad, arrowhead-shaped cervical alae help differentiate this parasite
from other canine and feline roundworms.
Toxocara cati is also a confirmed zoonotic agent and may cause diseases (larva migrans) in people who accidentally ingest embryonated eggs
from the environment. Visceral larva migrans results from larval migration and damage to internal organs, such as the liver,
lungs, kidneys, or brain. Ocular larva migrans occurs when larvae migrate to the posterior chamber of the eye, which can lead
to granulomatous retinitis, retinal detachment, loss of vision, or, in severe cases, blindness. Recent research indicates
that ocular damage caused by T. cati may be as severe as the damage caused by Toxocara canis. In addition, 24 reports document that adult T. cati infections occur more frequently in people than adult T. canis infections.
Hookworms. The prevalence of hookworm (Ancylostoma tubaeforme) infections in cats is exceeded only by roundworms (Figure
4). Cats acquire A. tubaeforme infections by ingesting infective larvae, through skin penetration, and from paratenic hosts, such as rats and mice. Apparently,
neither transplacental nor transmammary transmission of hookworms occurs in cats.
Figure 3 Nonembryonated egg of Toxocara cati (roundworm). This egg is similar to Toxocara canis but smaller.
Experimental study results suggest that hookworm infections in cats can cause weight loss and anemia. Interestingly, another
scientific study shows that a mean infection level of 100 worms was all that was needed to cause death in infected kittens.
Like roundworms, hookworm infections can occur in older cats, too. In another survey I conducted, 22 out of 27 cats infected
with A. tubaeforme were 2 years old or older; 13 out of 27 were 3 years old or older.
Ectoparasites. Of all the ectoparasites that can infest cats in the United States, fleas (Ctenocephalides
felis) and ear mites (Otodectes
cynotis) are the most common. The less common feline ectoparasites include lice (Felicola
subrostratus), face mange mites (Notoedres
cati), walking dandruff mites (Cheyletiella
blakei), and fur mites (Lynxacarus
Fleas are a major cause of dermal irritation and allergy and vectors of such disease agents as Bartonella
henselae (cat scratch disease). Studies also indicate that fleas may carry the infectious agents Rickettsia
felis and Haemoplasma species. The flea's role in actual transmission of these agents is not yet clear. Ear mites are frequent causes or contributors
to otitis involving the external ear canal (Figure
Figure 4 Nonembryonated egg of Ancylostoma tubaeforme (hookworm).