When Anti-Parasitics Meet Wild Hosts: Rethinking Veterinary Treatments in Aquatic Species

While veterinary anti-parasitic treatments are a cornerstone of livestock and aquaculture management, their effects on wild species and naturally occurring parasites are largely unexplored. A recent experimental study focused on bithionol, a widely used anthelmintic and algaecide, to investigate how standard aquaculture treatments influence both European chub (Squalius cephalus) and their acanthocephalan parasites.

Researchers assessed behavioral changes, physiological responses, and parasitic metrics, including abundance, size, and reproductive output. The findings revealed that bithionol altered fish behavior—with increased opercular movements and shifts in spatial positioning—but surprisingly had minimal impact on physiological markers. Even more striking, the acanthocephalan parasites persisted unaffected, suggesting potential resistance or environmental factors that diminish drug efficacy in natural populations.

The study also highlights the complex dynamics between host and parasite. While acanthocephalans can influence host immunity and behavior, their presence neither amplified nor mitigated the effects of bithionol on fish. These results challenge assumptions about the universal efficacy of anti-parasitics and underscore the need for careful evaluation of veterinary treatments beyond target species.

This research not only informs aquaculture management practices but also raises important questions about environmental contamination, drug resistance, and the broader ecological consequences of anti-parasitic use. For veterinarians, aquaculture specialists, and wildlife managers, these findings stress the importance of balancing parasite control with host and ecosystem health, while monitoring behavioral and physiological impacts in non-target species.

Read journal article here: How are host-parasite interactions affected by veterinary anti-parasitic treatment? An experimental approach