VOLUME 19 NUMBER 1 (January to June 2026)

Companion animals as potential contributors to parasite contamination in lakeshore ecosystems of San Pablo, Laguna, Philippines

The Seven Lakes of San Pablo, Laguna are vital freshwater systems that are ecologically and socio-economically important but increasingly vulnerable to contamination and public health risks. While intestinal parasites have been detected in these lakes, their sources remain unclear. Companion animals residing near lakeshores may serve as potential reservoirs of zoonotic parasites, although their role as direct sources of lake contamination has not been confirmed. Therefore, a cross-sectional study was conducted in communities surrounding Lakes Sampaloc, Calibato, and Bunot to assess parasite occurrence and zoonotic potential in companion animals. Previous studies documented the presence of waterborne protozoa in the lakes, including Cryptosporidium spp. (30.5%), Giardia spp. (14.3%), Blastocystis spp. (20.0%), and Acanthamoeba spp. (19.1%), with all four protozoan genera detected in Lake Calibato. These findings provided the rationale for investigating companion animals living near the lakes as potential sources of parasite contamination. A total of 71 fecal samples were collected from dogs (n = 52) and cats (n = 19) residing within a 200 m radius of the lakeshores. Helminths were detected in 57.7% of dogs and 63.2% of cats, predominantly hookworms/strongylids, followed by Trichuris spp. and Toxocara spp. Protozoan infections were identified in 53.8% of dogs and 52.6% of cats, including Cryptosporidium spp. and Giardia spp.

In univariate analyses, free-ranging behavior and lack of deworming were associated with any infection. In the multivariable model, place of defecation was significantly associated with infection status, with outside defecation showing lower odds of any infection than inside defecation (OR = 0.1442, 95% CI: 0.0216–0.7448, p = 0.0282), a counterintuitive finding that should be interpreted cautiously. Deworming showed a borderline association with infection status.

These findings highlight the need for responsible pet ownership, regular deworming, community education, and integrated environmental management to reduce zoonotic parasite transmission risks in lakeshore communities.