Drug dose and animal welfare: important considerations in the treatment of wildlife

Abstract

A recent publication in Parasitology Research by (Old et al. Parasitol Res 120:1077-1090 raises the topical and often controversial issue of the treatment of wildlife by personnel with little or no formal scientific training (e.g. wildlife carers). In a valuable contribution to the subject, Old and colleagues document a wide range of topical (pour-on) application doses and frequencies of moxidectin (Cydectin®) administered in situ to bare-nosed wombats (Vombatus ursinus) by members of the wildlife carer/treater community in southeast Australia to treat sarcoptic mange disease. This treatment occurred under minor use permits issued by the Australian Pesticides and Veterinary Management Authority (APVMA). These permits do not require veterinary supervision, although carers are registered and are expected to comply with the guidelines of this permit. The prevalence and severity of sarcoptic mange in wildlife is influenced by a variety of factors including mite biology, environmental conditions, population density, animal behaviour and immune susceptibility (Browne et al. Bioscience, 2021). In bare-nosed wombats, combinations of these elements play a substantial role in making the treatment of an already difficult disease more complex. (Moroni et al. Parasit Vectors 13:471, 2020) comment that any pharmacological treatment of freeranging wildlife must consider these factors when assessing their feasibility and implications, especially in the context of emerging drug resistance and potential long-term ecological impacts. As individuals with significant interest in sarcoptic mange and representing a range of professional research and veterinary expertise, we see value in providing expert commentary on this issue.

Diseases of Iberian ibex (Capra pyrenaica)

“…Moreover, ivermectin plasma concentration decreased below 20% in 72 h after experimental administration in Iberian ibexes (Moroni et al 2022a ), further demonstrating the lack of efficacy of this measure. On the other hand, massive administration of topic macrocyclic lactones can lead to overdosing (Old et al 2021 ; Mounsey et al 2022 ). Moreover, such inadequate dosage and massive release of antiparasitic drugs in the environment increase the probability of the mite generating resistance against the treatment (Tabashnik 1994 ; Vermunt 1996 ; Currie et al 2004 ; Bliss et al 2008 ; Terada et al 2010 ; Andriantjoanirina et al 2014 ), which adds to the detrimental environmental consequences for coprophagous arthropods and other non-target invertebrates (Sommer et al 1992 ; Herd et al 1996 ; Verdú et al 2015 , 2018 ).…”

Annual short-burst mass anthelmintic administration reduces tuberculosis severity but not prevalence in a wildlife reservoir

“…In our study the amount of medicated feed required for deworming was 2.4 g, and individual over-dosing is therefore likely to have occurred. Such over-dosing has been reported for topical applications of macrocyclic lactones in wombats (Old et al, 2021;Mounsey et al, 2022). Overdosing of some drugs may be harmful to the host and/or result in release of the drug into the environment while underdosing may result in incomplete removal.…”

Pathophysiological and Pharmaceutical Considerations for Enhancing the Control of Sarcoptes scabiei in Wombats Through Improved Transdermal Drug Delivery

“…As a result, free drug molecules have difficulty permeating through the wombat skin in significant amounts, especially during moderate-to-severe sarcoptic mange infections, likely leading to reduced therapeutic efficacy and incomplete recovery ( 14 , 26 ). Higher doses have been administered in an attempt to provide adequate systemic drug concentrations following transdermal drug delivery in an already more compromised animal ( 31 ). However, administering higher doses does not always equate to increased efficacy and can instead increase the risk of adverse effects such as skin irritations and dermal toxicity.…”

“…For this indication, it is usually applied topically as a pour-on treatment. The optimal dose and dosing frequency are still areas of contention, with multiple recommended dosing regimens used over the years ( 31 ). For example, Table 1 shows one of the recommended weekly application regimens that has a treatment duration of several months.…”