Quiz: How much do you really know about feline parasites?


Put your parasitology chops to the test with these 11 questions. 

Azaliya (Elya Vatel) / stock.adobe.com

Azaliya (Elya Vatel) / stock.adobe.com

Content sponsored by Vetoquinol

Many feline parasitesare only a nuisance, but many can be life-threatening or have serious public health implications. With prevalence rates as high as 45% in some populations1 and some gastrointestinal parasites transmissible to humans,1,2 parasitology is not a topic that can be taken lightly.

Below are 11 questions that will reactivate your knowledge and perhaps challenge your preconceived notions. Assess these parasitology pearls.

1. The cat is a dead-end or atypical host for heartworms.

True—Cats are not a preferred host for heartworms. Therefore, infected cats may have only 1 or 2 adult worms in their bodies, and sometimes no heartworms reach the adult stage.3 This often makes diagnosis difficult, but it is important to note that even immature worms can cause significant illness, such as Heartworm Associated Respiratory Disease (HARD).3

2. Cats can spontaneously clear heartworm infection.

True—Because the cat is an atypical host, many heartworms do not reach maturity inside cats. However, immature worms can cause permanent damage. HARD can lead to coughing, wheezing, and other respiratory symptoms. Histopathologic lesions, most notably occlusive medial hypertrophy of the small pulmonary arterioles, are evident even in cats that clear the infection.3

3. Serious clinical signs of heartworm infection occur only when adult worms die in an infected cat.

False—Clinical signs occur in cats at 2 distinct stages: when juvenile heartworms arrive in the pulmonary vasculature, 3 to 4 months after infection, causing acute inflammation, and when adult heartworms begin to die. Degenerating heartworms lead to pulmonary thromboembolism and acute inflammation, often causing fatal lung injury.3

4. No drug has been approved for the treatment of heartworm infection in cats.

True—Melarsomine, the drug approved for adulticide therapy in dogs, is not safe for cats. Thus, prevention of infection is critical.

5. Because cats are considered to be at lower risk for HARD than dogs, the American Heartworm Society does not recommend chemoprophylaxis in cats.

False—AHS recommends monthly prevention for all domestic cats in any area where heartworms are endemic in dogs.3 NB: Canine heartworm infection has been diagnosed in all 50 states.

6. Topical moxidectin is approved for the prevention of feline heartworms.

True—A monthly topical application of moxidectin has been approved as a safe and effective way to prevent feline heartworm infection. A monthly application of IMOXI Topical Solution for Cats (imidacloprid + moxidectin) offers internal and external parasite prevention.

7. Unlike in dogs, roundworm and hookworm infections in cats are not considered zoonotic.

False—Feline roundworms and hookworms are zoonotic. In humans, roundworms can cause visceral and ocular larva migrans, and hookworms can cause cutaneous larva migrans.1,2

8. The flea is the most common external parasite in cats.

True—Flea infestation is still very common in cats and can lead to life-threatening anemia, especially in kittens, severe dermatological disease, and tapeworm (Dipylidium caninum) infection. The cat flea, Ctenocephalides felis, can also transmit Rickettsia typhi, Rickettsia felis, Bartonella henselae, Mycoplasma spp (formerly Hemobartonella spp), Yersinia pestis (plague), and Francisella tularensis (tularemia).4,5

9. One pregnant flea on a cat can lead to a severe infestation in the home.

True—A single flea can typically lay at least 20 eggs every 24 hours, half of which will also be females and thus lead to more than 20,000 adults in 2 months. The Companion Animal Parasite Council recommends that cats be treated with flea control products year round throughout their lives to prevent infestations on pets and in the home.4,5

10. Otodectes cynotis (ear mites) are a significant ectoparasite only in stray and free-roaming cats.

False—Studies have shown that up to 25% of pet cats4 are infested with the Otodectes cynotis species. Although most cats show clinical signs, up to 10%4 harbor subclinical infections.4,6,7

11. Nothing can prevent heartworms, roundworms, hookworms, fleas, and ear mites in cats.

False—IMOXI Topical Solution for Cats (imidacloprid + moxidectin) is a once-a-month topical solution that can prevent these pests in cats and kittens 9 weeks and older that weigh at least 2 lbs.

Wrapping it up

How did it go? Although internal and external parasites are a major concern for cat owners, these questions hopefully served as a timely refresher that will help you make the best recommendations for feline patients.


  1. Cornell Feline Health Center. Gastrointestinal parasites of cats. Accessed January 4, 2021. www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/gastrointestinal-parasites-cats
  2. Companion Animal Parasite Council. CAPC Guidelines. Accessed December 29, 2021. https://capcvet.org/guidelines/
  3. American Heartworm Society. Current feline guidelines for the prevention, diagnosis, and management of heartworm (Dirofilaria immitis) infection in cats. Accessed December 29, 2021. www.heartwormsociety.org/images/pdf/2014-AHS-Feline-Guidelines.pdf
  4. Akucewich LH, Philman K, Clark A, et al. Prevalence of ectoparasites in a population of feral cats from north central Florida during the summer. Vet Parasitol. 2002;109(1-2):129-139. doi:10.1016/s0304-4017(02)00205-4
  5. Dryden MW, Rust MK. The cat flea: biology, ecology and control. Vet Parasitol. 1994;52(1-2):1-19. doi:10.1016/0304-4017(94)90031-0
  6. Milley C, Dryden M, Rosenkrantz W, et al. Comparison of parasitic mite retrieval methods in a population of community cats. J Feline Med Surg. 2017;19(6):657-664. doi:10.1177/1098612X16650717
  7. Sotiraki ST, Koutinas AF, Leontides LS, et al. Factors affecting the frequency of ear canal and face infestation by Otodectes cynotis in the cat. Vet Parasitol. 2001;96(4):309-315. doi:10.1016/s0304-4017(01)00383-1
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