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

Adaptive interventions for advancing in situ wildlife disease management

There is a critical need for advancements in disease management strategies for wildlife, but free-living animals pose numerous challenges that can hinder progress. Most disease management attempts involve fixed interventions accompanied by post hoc outcome assessments focused on success or failure. Though these approaches have led to valuable management advances, there are limitations to both the rate of advancement and amount of information that can be gained. As such, strategies that support more rapid progress are required. Sarcoptic mange, caused by epidermal infection with Sarcoptes scabiei mites, is a globally emerging and re-emerging panzootic that exemplifies this problem. The bare-nosed wombat (Vombatus ursinus), a marsupial endemic to southeastern Australia, is impacted by sarcoptic mange throughout its geographic range and enhanced disease management capabilities are needed to improve upon existing in situ methods. We sought to advance in situ wildlife disease management for sarcoptic mange in free-living bare-nosed wombats, implementing an adaptive approach using fluralaner (Bravecto, MSD Animal Health) and a structured process of learning and method-optimisation. By using surveillance of treated wombats to inform real-time management changes, we have demonstrated the efficacy of topically administered fluralaner at 45 and 85 mg/kg against sarcoptic mange. Importantly, we observed variation in the effects of 45 mg/kg doses, but through our adaptive approach found that 85 mg/kg doses consistently reduced mange severity. Through modifying our surveillance program, we also identified individual-level variation in wombat observability and used this to quantify the level of surveillance needed to assess long-term management success. Our adaptive intervention represents the first report of sarcoptic mange management with fluralaner in free-living wildlife and evaluation of its efficacy in situ. This study illustrates how adapting interventions in real time can advance wildlife disease management and may be applicable to accelerating in situ improvements for other host-pathogen systems.

Pharmacokinetics of a topical application of moxidectin in bare-nosed wombats (Vombatus ursinus)

Sarcoptic mange is a debilitating disease that affects bare-nosed wombats (Vombatus ursinus). One of the drugs currently used for treatment is moxidectin, as it has a relatively high efficacy against endo and ectoparasites and side effects are uncommon in domestic species, thus it is considered a relatively safe drug to use at the recommended doses. Developing further understanding of the pharmacokinetics of moxidectin will aid in developing treatment regimens for sarcoptic mange in wombats. Here we analyzed the pharmacokinetic parameters of using 100 ml of moxidectin (5 g/l) applied topically. We found that mean peak plasma concentration was 0.50 ng/ml and half-life was 8 days. Moxidectin was excreted in scats with the mean peak concentration of 2461.43 ng/g (on a dry matter basis). Our study has provided the pharmacokinetic parameters of a commonly used treatment for sarcoptic mange in wombats. There were no adverse side effects recorded in the wombats after applying moxidectin topically. This study replicated real-world conditions using topical application on free-living wombats. The relatively low plasma concentration suggests the drug is not accumulating in the blood stream and is excreted via scats.

Diseases of Iberian ibex (Capra pyrenaica)

Iberian ibex (Capra pyrenaica) is an ecologically and economically relevant medium-sized emblematic mountain ungulate. Diseases participate in the population dynamics of the species as a regulating agent, but can also threaten the conservation and viability of vulnerable population units. Moreover, Iberian ibex can also be a carrier or even a reservoir of pathogens shared with domestic animals and/or humans, being therefore a concern for livestock and public health. The objective of this review is to compile the currently available knowledge on (1) diseases of Iberian ibex, presented according to their relevance on the health and demography of free-ranging populations; (2) diseases subjected to heath surveillance plans; (3) other diseases reported in the species; and (4) diseases with particular relevance in captive Iberian ibex populations. The systematic review of all the information on diseases affecting the species unveils unpublished reports, scientific communications in meetings, and scientific articles, allowing the first comprehensive compilation of Iberian ibex diseases. This review identifies the gaps in knowledge regarding pathogenesis, immune response, diagnostic methods, treatment, and management of diseases in Iberian ibex, providing a base for future research. Moreover, this challenges wildlife and livestock disease and wildlife population managers to assess the priorities and policies currently implemented in Iberian ibex health surveillance and monitoring and disease management.

Pharmacokinetic and pharmacodynamic considerations for treating sarcoptic mange with cross-relevance to Australian wildlife

Sarcoptes scabiei is the microscopic burrowing mite responsible for sarcoptic mange, which is reported in approximately 150 mammalian species. In Australia, sarcoptic mange affects a number of native and introduced wildlife species, is particularly severe in bare-nosed wombats (Vombatus ursinus) and an emerging issue in koala and quenda. There are a variety of acaricides available for the treatment of sarcoptic mange which are generally effective in eliminating mites from humans and animals in captivity. In wild populations, effective treatment is challenging, and concerns exist regarding safety, efficacy and the potential emergence of acaricide resistance. There are risks where acaricides are used intensively or inadequately, which could adversely affect treatment success rates as well as animal welfare. While reviews on epidemiology, treatment strategies, and pathogenesis of sarcoptic mange in wildlife are available, there is currently no review evaluating the use of specific acaricides in the context of their pharmacokinetic and pharmacodynamic properties, and subsequent likelihood of emerging drug resistance, particularly for Australian wildlife. This review critically evaluates acaricides that have been utilised to treat sarcoptic mange in wildlife, including dosage forms and routes, pharmacokinetics, mode of action and efficacy. We also highlight the reports of resistance of S. scabiei to acaricides, including clinical and in vitro observations.

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

Sarcoptic scabiei is an invasive parasitic mite that negatively impacts wombats, causing sarcoptic mange disease, characterized by alopecia, intense pruritus, hyperkeratosis, and eventual mortality. Evidence suggests that wombats may be unable to recovery from infection without the assistance of treatments. Transdermal drug delivery is considered the most ideal route of administration for in situ treatment in free-ranging wombats, as it is non-invasive and avoids the need to capture affected individuals. Although there are effective antiparasitic drugs available, an essential challenge is adequate administration of drugs and sufficient drug retention and absorption when delivered. This review will describe the implications of sarcoptic mange on the physiology of wombats as well as discuss the most widely used antiparasitic drugs to treat S. scabiei (ivermectin, moxidectin, and fluralaner). The prospects for improved absorption of these drugs will be addressed in the context of pathophysiological and pharmaceutical considerations influencing transdermal drug delivery in wombats with sarcoptic mange.