# Intestinal parasite prevalences in dogs and cats: a decade of retrospective data from a reference veterinary laboratory in Madrid, Spain

## TL;DR

This study analyzed over 15,000 pet fecal samples in Madrid to track intestinal parasite trends in dogs and cats over a decade, finding high prevalence of zoonotic parasites like Giardia and Toxocara.

## Contribution

The study provides the first comprehensive, decade-long analysis of intestinal parasite prevalence in pets in Madrid using modern diagnostic techniques.

## Key findings

- Giardia duodenalis was the most prevalent parasite in dogs, while Cystoisospora spp. was most common in cats.
- Puppies and kittens had higher infection rates, and seasonal patterns were observed for different parasites.
- Infection rates increased in shelter animals and over time for Giardia, while Cystoisospora decreased.

## Abstract

Spain’s recent abrupt rise in numbers of registered pet dogs and cats 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, Cryptosporidium spp. and Toxocara spp. This study was designed to assess intestinal parasite prevalence in dogs and cats along with epidemiological trends.

Between 2013 and 2023, a total of 15,899 faecal samples from dogs and cats submitted to a reference laboratory of parasitology in Madrid (Spain) were analysed using Mini-FLOTAC®, merthiolate–iodine–formalin (MIF), Baermann–Wetzel (for lungworms and S. stercoralis when indicated) and direct immunofluorescence assays, with molecular confirmation by polymerase chain reaction (PCR) when required. Epidemiological variables were statistically analysed.

Overall, 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 as T. cati (7.6%) were more frequent in cats than in 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 being frequently involved.

Puppies and kittens were more susceptible to infection, likely owing 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, the prevalence of G. duodenalis increased, while that of Cystoisospora spp. declined.

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.