Parasites Behind Bars: The Hidden Burden of Gastrointestinal (GI) Helminths in Captive Mammals in Sri Lanka

Abstract

Gastrointestinal (GI) helminths pose a significant health threat to captive mammals, particularly in zoological settings where crowding, shared enclosures, and environmental contamination facilitate parasite transmission. This study examines the prevalence and potential risk factors of GI helminth infections in 40 mammal species from 8 taxonomic orders at the Dehiwala National Zoological Garden, Sri Lanka. Faecal samples were analysed using modified salt flotation technique to identify helminth species. Binary Logistic Regression was performed to assess the association between food habit, water source, and helminth prevalence. The overall GI helminth prevalence was 37.5%, with carnivores exhibiting the highest prevalence (81.8%), while Perissodactyla, Lagomorpha, and Proboscidea showed no infections. Strongyle sp. was the most prevalent parasite (80%), followed by Ascaris spp. and Bertiella spp. (13% each), and Toxocara spp. (2.5%). Binary logistic regression revealed that food type is a significant contributor of parasitic infection. Carnivorous species exhibited significantly higher odds of infection compared to omnivores (OR=22.721, p<0.01). However, the water source was not found to be a significant contributor of parasitic helminths among the captive animals (OR = 4.244, p = 0.095.) Captive mammals at the Dehiwala National Zoological Garden exhibit a substantial gastrointestinal helminth burden, with carnivorous species showing significantly higher infection rates. Diet emerged as a key risk factor, while routine deworming every three months proved insufficient in controlling persistent infections. These findings highlight the need for more effective, species-specific parasite management strategies. Parasite control should be tailored to species and dietary habits, with special attention to Carnivores. Meat-based diets must be handled and sourced hygienically to reduce parasite exposure. Faecal examinations should be conducted more frequently and extensively. High-risk groups require intensified interventions, while low-risk orders should remain under regular surveillance.

KEYWORDS: Captive mammals, Gastrointestinal (GI) helminths, Zoo epidemiology, Parasite prevalence, Risk factors