Intestinal parasites prevalence in dogs and cats: a decade of data from a retrospective study at a reference veterinary laboratory in Madrid, Spain

Background: Pet ownership rises globally in Spain; registered pet dogs and cats now outnumber children. This rise has intensified the need for proper animal health care, as 60% of infectious diseases are zoonotic. While pathogen detection has improved through advances in molecular techniques, pet owners often fail to adhere to veterinary guidelines, increasing infection risks. Among the diagnostic tools available, faecal analysis plays a key role in detecting zoonotic parasites such as Giardia duodenalis , Toxocara spp. and Cryptosporidium spp. This study was designed to assess intestinal parasite prevalence in dogs and cats along with epidemiological trends. Results: Over the period 2013 to 2023, 15,899 faecal samples from dogs and cats in a reference parasitology laboratory in Madrid (Spain) were analysed. According to our results, 26% of dogs and 21.4% of cats tested positive for at least one parasite. Protozoan infections were more prevalent overall, particularly G. duodenalis in dogs (16.0%), and Cystoisospora spp. in cats (7.8%). In contrast, helminth infections such us T. cati (7.6%) were more frequent in cats than dogs. Dogs were more commonly infected by protozoa than helminths, while cats showed a more balanced distribution between both groups. Co-infections occurred in 13.6% of positive samples, with G. duodenalis frequently involved. Puppies and kittens were more susceptible to infection, likely due to an immature immune system. In animals from shelters, infection rates were higher than in owned pets. Seasonal variations were clearly observed such that G. duodenalis peaked in winter and helminths in autumn. Over time, G. duodenalis prevalence increased, while that of Cystoisospora spp. declined. Conclusions: These findings highlight the importance of parasite control for purposes of both animal and public health and emphasize a need for regular faecal testing, deworming and improving owner awareness of parasites. To minimize zoonotic risks and improve pet health management, we would recommend standardizing diagnostic procedures and designing suitable veterinary interventions.