Prevalence of internal parasites in North American domestic cats

The prevalence of endoparasites (internal parasites) affecting domestic cat in North America interests me, and it might (just) interest other cat owners too. America is the dominant domestic cat region and therefore they lead the world in terms of information on domestic cat ownership. This makes America the starting point, in my mind, when looking at details of this nature. The infestation rate by endoparasites of domestic cats in America ultimately comes down to the quality of their caregiving.

Prevalence of endoparasites affecting North American domestic cats
Prevalence of endoparasites affecting North American domestic cats. Image: Pixabay.
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You can keep endoparasites down through deworming and keeping cats indoors so that they don’t have the opportunity to feed on mice and other rodents and birds which can carry transmissible endoparasites.

Fortunately, we have a study from the Department of Veterinary Pathobiology, College of Veterinary Medicine, Oklahoma State University and the Department of Statistics from the same university. It looked at parasites in faeces of client-owned cats in North America from 2007 through 2018. It’s quite recent, therefore. I’m able to present the results in general terms below.

They found that there was a higher prevalence of parasitic infection in younger cats. Also, as expected, infestations increased during summer through fall (autumn in the UK). Commonly detected parasites were: Cystoisospora, this, Giardia, and Alaria. The first listed is an intestinal coccidian parasite. As I understand it a different subspecies of this parasite can infect humans. Toxocara cati is a nematode which is found worldwide. The adult worms live in the small intestine. The females produced eggs that are passed in the faeces. Infested kittens have stunted growth and their loss of condition. It is commonly called the roundworm.

Giardia is a minute one-celled organism which lives in the small intestines of cats. It can cause serious illness and the symptoms are diarrhoea, dehydration and sluggishness. Alaria are trematodes. The adults live in the small intestine of their host. Eggs leave the host via faeces. Cats and dogs can be infested. They are called ‘flukes’. Preventing cats and dogs from hunting can prevent the acquisition of this parasite.

List of internal parasites in cats in N. America and prevalence

The most common parasite stage observed was:

Cystoisospora oocysts (9.4%; 243/2586);
Toxocara cati eggs (7.8%; 202/2586);
Giardia cysts (4.0%; 104/2586);
Alaria eggs (3.5%; 91/2586);
Ancylostoma eggs (1.2%; 32/2586);
Taeniid proglottids/eggs (1.2%; 30/2586);
Dipylidium caninum proglottids/egg packets (1.1 %; 29/2586);
Eucoleus aerophilus eggs (0.7%; 18/2586).

Less commonly:

Physalopetra eggs (0.19%; 5/2586);
Toxascaris leonina eggs (0.19%; 5/2586);
Tritrichomonas blagburni trophozoites (0.15%; 4/2586);
Ollulanus tricuspis larvae/adults (0.12%; 3/2586); Platynosomum fastosum eggs (0.12%; 3/2586);
Aelurostrongylus abstrusus larvae (0.08%; 2/2323);
Sarcocystis sporocysts (0.08%; 2/2586);
Spirometra eggs (0.08%; 2/2586);
Mesocestoides proglottids/eggs (0.08%; 2/2586);
Trichuris felis eggs (0.08%; 2/2586);
Cryptosporidium oocysts (0.04%; 1/2586);
Toxoplasma-like small coccidian oocysts (0.04%; 1/2586).

The study

The objective was to measure the prevalence of these parasites. They analysed faecal samples from domestic cats diagnosed at Oklahoma University over a 12-year period.

In general, they state that “parasites, eggs, oocysts, larvae or cysts were not detected in the majority of cases, namely 75.5%. In other words, three quarters of the cats did not have parasites inside their bodies. About 19% of the cats had one parasite inside them. And 5.7% of the cats “were infected by multiple parasites”.

Comparison with stray cats in the Middle East

Fortuitously, I have just written an article on a subdomain website about the prevalence of endoparasites in stray cats in Iran (link to article). The information provides a nice comparison; an important comparison, really. Domestic cats in North America are, in general, well looked after. You might argue that these cats are at the top of the tree in terms of the caregiving received. And you might argue that the stray and feral cats of the Middle East are at the bottom of the tree in terms of caregiving by humans.

The stray cats of Iran are almost universally infested with endoparasites. In fact, 95.6% of the 108 cats checked in the Iran study were infested with endoparasites inside the gastrointestinal tract. Quite a contrast which I guess is to be expected.

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