Environmental risk assessment of veterinary parasiticides used in cattle

Abstract

All veterinary medicines have to undergo a rigorous environmental risk assessment before gaining a marketing authorisation; post-marketing pharmacovigilance ensures constant surveillance for any environmental impacts that had not been anticipated from earlier research. Products are labelled to reflect any potential risk points. Despite these procedures, some compounds, notably parasiticides of the macrocyclic lactone class that are used in large animal practice, have gained a reputation among some scientists, the general public and the media for having adverse effects on dung insect fauna and for causing delays in the degradation of faeces on pasture. While the toxicity of faecal residues of insecticides to non-target insect fauna, when measured under controlled conditions in short-term experiments is indisputable, the consequences of such activity at ecological scales are much less well defined. Dung provides an ephemeral habitat for an enormous array of macro- and micro-invertebrates, fungi and bacteria, whose composition changes as pats age and disintegrate. Perturbations to such complex systems inevitably have a variety of outcomes and this is reflected in field trials, which can produce conflicting results. This article summarises pertinent aspects of the underlying biology and ecology of the bovine faecal pat and the evidence for significant impact of veterinary medication.

Season‐Long Simplification of Insect Communities in Dung From Cattle Treated With an Extended‐Release Formulation of the Parasiticide Eprinomectin

“…Extrapolating these results to assess the risk to insect populations and ecosystem function at the level of the pasture is challenging and needs to consider mitigating factors. The complexity of this challenge is examined by Forbes (2021), who identifies the importance of refugia to protect insect populations. Not all cattle in a pasture may be treated such that a percentage of dung pats may remain residue free.…”

Ethnoveterinary data in Britain and Ireland: can native herbal medicine promote animal health?

“…The use or adaptation of traditional ethnoveterinary practices could promote sustainable management or animal healthcare and minimize the impacts on the environment (Mayer et al 2014, Oliveira et al 2021, Wanzala et al 2005. The impact of veterinary antibiotics, anthelmintics, parasiticides and insecticides on the environment, including on insects, earthworms, and resistance of bacteria and helminths, is a major and growing problem (Forbes 2021, Goodenough et al 2019, Menz et al 2019. To develop and broaden the use of herbal remedies in livestock will require the development of well-funded, longterm research by all partners in the sector, and the development of appropriate regulatory frameworks .…”