Detection and molecular diversity of Giardia duodenalis and Cryptosporidium spp. in sheltered dogs and cats in Northern Spain

Abstract Domestic dogs and cats may act as natural reservoirs of a large number of zoonotic pathogens, including the enteric parasites Giardia duodenalis and Cryptosporidium spp., the most relevant protozoan species causing gastrointestinal disease worldwide. A cross-sectional epidemiological study aiming to assess the prevalence and molecular diversity of G . duodenalis and Cryptosporidium spp. was conducted in an animal rescue centre in the province of Alava (Northern Spain). A total of 194 and 65 faecal dropping samples from individual dogs and cats, respectively, were collected between November 2013 and June 2016. G . duodenalis cysts and Cryptosporidium spp. oocysts were detected by direct fluorescence microscopy and PCR-based methods targeting the small subunit ribosomal RNA gene of these parasites. Overall, G . duodenalis and Cryptosporidium spp. were detected in 33% (63/194) and 4.1% (8/194) of dogs, and 9.2% (6/65) and 4.6% (3/65) of cats, respectively. G . duodenalis and Cryptosporidium co-infections were observed in 1.5% (3/194) of dogs, but not in cats. No significant differences in infection rates could be demonstrated among dogs or cats according to their sex, age group, status, or geographical origin. Multi-locus sequence-based genotyping of the glutamate dehydrogenase and β-giardin genes of G . duodenalis allowed the characterization of 19 canine isolates that were unambiguously assigned to sub-assemblages AII ( n  = 7), BIII ( n  = 1), and BIV ( n  = 7), and assemblages C ( n  = 3) and D ( n  = 1). Two feline isolates were genotyped as assemblages A and F, respectively. No mixed assemblage or sub-assemblage infections were identified. C . canis ( n  = 5) and C . hominis ( n  = 1) were the Cryptosporidium species found in dogs, whereas C . felis ( n  = 1) was identified in cats. The finding of G . duodenalis sub-assemblages AII, BIII, and BIV circulating in dogs (but not cats) may have zoonotic potential, although most of the AII and BIV isolates sub-genotyped corresponded to genetic variants not previously found in Spanish human populations. Dogs may also act as novel suitable hosts for C . hominis . We recommend to considerer companion animals as sentinel surveillance system for zoonotic giardiasis and cryptosporidiosis in order to minimize the risk of spreading of these parasitic diseases among the human population.