Giardia and Cryptosporidium infections in Danish cats: risk factors and zoonotic potential

Parasitol Res. 2020 Jul;119(7):2275-2286. doi: 10.1007/s00436-020-06715-2. Epub 2020 May 26.


Giardia and Cryptosporidium infections are common in cats, but knowledge is limited about their clinical importance, risk factors, and the role of cats as a reservoir for human infections. Here, we collected faeces and questionnaire data from 284 cats from shelters and veterinary clinics in the Copenhagen Metropolitan Region (= study population). Additionally, 33 samples were analysed separately from catteries with gastrointestinal clinical signs (= cases). (Oo-)cysts were quantified by immunofluorescence microscopy. All Giardia (n = 34) and Cryptosporidium (n = 29) positive samples were analysed by sequencing of the 18S rRNA, gdh and hsp70 loci, and co-infections were detected by McMaster/inverted microscopy. In the study population, 7.0% and 6.7% were positive for Giardia and Cryptosporidium respectively; 48.5% and 36.4% of the breeder cats (cases) were infected. Increased odds of diarrhoea were demonstrated in Giardia (p = 0.0008) and Cryptosporidium (p = 0.034) positive cats. For Giardia, the odds were positively correlated with infection intensity. Co-infection with Cryptosporidium (OR 12.79; p < 0.001), parasitic co-infections other than Cryptosporidium (OR 5.22; p = 0.009), no deworming (OR 4.67; p = 0.035), and male sex (OR 3.63; p = 0.025) were risk factors for Giardia. For Cryptosporidium, co-infection with Giardia was the only risk factor (OR 11.93; p < 0.0001). Genotyping revealed G. duodenalis assemblages A and F, and C. felis, all of them previously detected in humans. In conclusion, excretion of Giardia and Cryptosporidium was associated with clinical disease. Although a public health risk is likely, studies including larger sample sizes, more discriminatory markers and samples from other animals and humans are needed to reveal the full zoonotic potential.

Keywords: Cats; Cryptosporidium; Denmark; Genotyping; Giardia; Risk factors.

MeSH terms

  • Animals
  • Cat Diseases / parasitology*
  • Cats
  • Cryptosporidiosis / epidemiology*
  • Cryptosporidiosis / parasitology
  • Cryptosporidium / genetics
  • Denmark / epidemiology
  • Disease Reservoirs / parasitology
  • Disease Reservoirs / veterinary
  • Feces / parasitology
  • Female
  • Giardia / genetics
  • Giardiasis / epidemiology*
  • Giardiasis / parasitology
  • Giardiasis / veterinary*
  • HSP70 Heat-Shock Proteins / genetics
  • Humans
  • Male
  • RNA, Ribosomal, 18S / genetics
  • Risk Factors
  • Sugar Alcohol Dehydrogenases / genetics


  • HSP70 Heat-Shock Proteins
  • RNA, Ribosomal, 18S
  • Sugar Alcohol Dehydrogenases
  • galactitol 2-dehydrogenase