# Endoparasites in carnivores in Swiss zoological institutions between 2009 and 2024: evaluation of risk factors and deworming strategies

## TL;DR

This study analyzed parasites in zoo carnivores in Switzerland over 15 years, finding that hunting prey or eating snails increased parasite risk, while on-site food animal slaughter was protective.

## Contribution

The study identifies risk factors and evaluates deworming strategies in zoo carnivores using a 15-year dataset from 30 Swiss institutions.

## Key findings

- 48.9% of 405 faecal samples tested positive for parasites, with ascarids being the most common.
- Hunting prey or eating snails significantly increased parasite occurrence (OR: 2.3).
- On-site slaughter of food animals appeared protective against parasites (OR: 0.5).

## Abstract

Parasitic infections in zoo carnivores pose risks to animal health and zoonotic transmission. Over a 15-year period, endoparasites were detected in faecal samples from Swiss zoo carnivores, with clinical and management data used to identify factors linked to parasite occurrence. The samples, originating from 50 species kept in 30 different institutions, were collected in 2009 (n = 140), 2018 (n = 149) and 2024 (n = 116), and analysed by Baermann-Wetzel technique, combined sedimentation/flotation, Giardia coproantigen detection and Ziehl-Neelsen staining of faecal smears. Fifteen samples were further analysed by biomolecular methods. Odds ratios and 95 % confidence intervals (OR, 95 % CI) were calculated to compare management strategies and assess potential risk factors. Overall, 198/405 (48.9 %) of the samples tested positive. The most frequent parasites were ascarids (n = 73), followed by Capillaria spp. (n = 66), Cystoisospora spp. (n = 50) and Cryptosporidium (n = 43). Most animals were asymptomatic. Among the animals with clinical observations available, diarrhoea was recorded in ten, respiratory signs in two and reduced body condition in four individuals. Of these, intestinal (e.g., ascarids, hookworms, Cystoisospora sp., Cryptosporidium sp.) or respiratory (e.g., Angiostrongylus vasorum, Capillaria boehmi) parasites were identified in seven animals. Hunting mice, birds, rodents or eating snails was significantly associated with positive findings (OR: 2.3, 95 % CI: 1.0–5.0, p = 0.04), whereas on-site slaughter of food animals appeared protective (OR: 0.5, 0.2–1.1, p = 0.09). Zoonotic parasites such as Strongyloides sp. (n = 3) and Baylisascaris sp. (n = 3) were rarely detected. Animals from institutions that did not apply any parasitological management measures (deworming and/or faecal examinations) were more likely to be positive for helminths compared to those from zoos applying such measures (OR: 3.4, 95 % CI: 1.1–10.3, p = 0.03). Although often subclinical, some parasites—especially respiratory helminths—can affect animal health, and stress or anaesthesia may exacerbate diseases in valuable individuals. Targeted, diagnosis-based deworming reduces anthelmintic use, and consequently the risk of resistance and the likelihood of adverse effects.

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•We analysed faecal samples of 50 zoo carnivore species from 30 Swiss institutions.•Over a 15-year period, 198/405 (48.9 %) of samples tested parasitologically positive.•Clinical signs observed in 16 animals; associated parasites in seven of them.•Hunting preys or eating snails was significantly associated with positive findings.•On-site slaughter of food animals appeared protective (OR: 0.5, 0.2–1.1, p = 0.09).

We analysed faecal samples of 50 zoo carnivore species from 30 Swiss institutions.

Over a 15-year period, 198/405 (48.9 %) of samples tested parasitologically positive.

Clinical signs observed in 16 animals; associated parasites in seven of them.

Hunting preys or eating snails was significantly associated with positive findings.

On-site slaughter of food animals appeared protective (OR: 0.5, 0.2–1.1, p = 0.09).