Prevalence of gastrointestinal parasites in dogs from İstanbul: Comparative analysis of wet mount microscopy and concentration technique in -80 °C frozen fecal samples

Monitoring gastrointestinal parasites of stray dogs is important for both animal and public health within the One Health framework. In regions endemic for zoonotic parasites such as Echinococcus spp., international biosafety guidelines recommend freezing canine fecal samples at -80 °C to prevent laboratory-acquired infections. However, the diagnostic performance of different methods applied to samples subjected to this biosafety procedure has not been sufficiently investigated. This study evaluated gastrointestinal parasites in stray dogs from the Anatolian side of İstanbul and compared the detection performance of saline-iodine wet mount microscopy and the formalin-ethyl acetate concentration technique (FECT) in fecal samples frozen at -80 °C. A total of 110 fecal samples from stray dogs admitted to shelters and veterinary clinics in seven districts were examined. Overall, gastrointestinal parasites were detected in 22 (20.0%) samples. Six taxa were identified, including Toxocara canis (8.2%), Cystoisospora spp. (7.3%), hookworms (5.5%), Trichuris vulpis (1.8%), taeniid eggs (1.8%), and Dipylidium caninum (1.8%). Coinfections were observed in 4.5% of the dogs. FECT detected more hookworm and taeniid eggs, whereas wet mount microscopy identified more Cystoisospora spp. oocysts and slightly more T. canis eggs. No statistically significant differences in parasite detection were observed between the two methods (P>0.05). The percentage agreement between methods ranged from 95.5% to 100%. These findings indicate that stray dogs in İstanbul continue to harbor parasites of zoonotic and veterinary importance. Both methods enabled the detection of parasite stages in fecal samples frozen at -80 °C, suggesting that they may provide complementary diagnostic information for the screening of frozen field samples.