The dynamics of gastrointestinal nematodes present in co-grazed host species kept in a Scottish zoological collection

Grazing animal species kept in zoological collections can be at risk of significant gastrointestinal nematode (GIN) infections. Little work has been undertaken to understand GIN species dynamics within co-grazed hosts. This study aimed to describe the species diversity of GINs found in faeces of grazing animals in a Scottish zoological collection.

At a single time-point, freshly voided faecal samples were collected randomly from horses, sheep, goats, alpacas and deer. Faecal worm egg counts (FWECs) were conducted using a saturated saline centrifugal flotation cuvette technique. The nematode species profile was estimated through deep-amplicon sequencing of ITS-2 and mitochondrial ND-4 markers to understand infection dynamics between host-species.

Variations were observed in FWECs across species, ranging from as low as 7epg in alpacas to 461epg in goats. Deep amplicon sequencing identified nine GIN species and some unclassified groups, with notable diversity shown among the hosts. Haemonchus contortus was predominantly found in alpacas and sheep, while Cylicocyclus longibursatus was common in horses. The analysis unveiled substantial genetic diversity in H. contortus across different hosts, with alpacas and sheep showing the highest number of amplicon sequence variants. The mitochondrial ND-4 gene analysis also indicated possible evolutionary pressures with balancing selection evident in alpacas and sheep. A number of unclassified GIN sequences were also identified, particularly in deer.

This study highlights the complexity of GIN dynamics within mixed-species grazing systems and the potential to integrate genomic technologies with faecal parasitology to understand these relationships to develop comprehensive GIN management strategies.