Moroni et al. Parasites Vectors (2020) 13:471 https://doi.org/10.1186/s13071-020-04347-0 Parasites & Vectors LETTER TO THE EDITOR Open Access Comment on: “The treatment of sarcoptic mange in wildlife: a systematic review” Barbara Moroni1, Marta Valldeperes2, Emmanuel Serrano2, Jorge Ramón López‑Olvera2, Santiago Lavín2 and Luca Rossi1* Abstract This letter comments on the article “The treatment of sarcoptic mange in wildlife: a systematic review” published in Parasites & Vectors 2019, 12:99, and discusses the limitations in the use of endectocides for scabies control in free- ranging wildlife. The ecological impact and drug resistance to ivermectin are also discussed. In our view, scabies control in free-ranging wildlife should be based preferably on population management measures, and whether to apply individual treatments to free-ranging populations should be considered very carefully and avoided where not absolutely warranted. Keywords: Sarcoptes scabiei, Wildlife diseases, Ivermectin, Drug resistance, Soil pollution Letter to the Editor treatment approach rather than population-based disease Recently, Rowe and colleagues have published an inter- management. esting review of the treatment of sarcoptic mange (here- Since the availability of ivermectin formulations for after “scabies”) in wildlife [1]. This review highlighted the animal use in 1975, this drug became the most effec- impact of this worldwide distributed parasitic disease tive and safe treatment for a broad range of endo- and and pointed out the need for consensus in the implemen- ectoparasites including Sarcoptes scabiei [2–4]. In fact, tation of effective treatment of captive and free-ranging ivermectin is included amongst the election drugs to wildlife affected by scabies. treat scabies not only in humans [5, 6] but also in domes- Although we fully agree on the need for a conven- tic [7] and wild mammals [8]. This macrocyclic lactone tion on scabies control in wildlife, we would like to draw is mainly delivered orally (e.g. in the form of drenching), attention to the challenges and risks of implementing pour-on or subcutaneously [2, 7] in physical or chemical protocols based on pharmacological treatments in the restrained individuals. Based on our professional experi- wild. In this letter, we will set out some reasons for the ences and field research using ivermectin and drugs with incongruency of such drug-based approach. related treatment regime methods, ivermectin treat- After the systematic review of 2205 publications, ments may be feasible for target individuals but highly Rowe et al. [1] kept 28 relevant articles reporting phar- challenging to unrealistic for whole populations in most macological effective treatments of scabies in wildlife, instances. notably ivermectin delivered multiple times via subcu- Most of the studies reviewed by Rowe et al. [1] were taneous injection. Most of these studies share a clinical focused on captive wildlife and only six out of the 28 papers were supposed to describe the output of ivermec- tin to control mange in free-ranging wildlife. Neverthe- *Correspondence: luca.rossi@unito.it less, and after a careful reading of these articles, we noted 1 Dipartimento di Scienze Veterinarie, Universitá di Torino, Grugliasco, that none of them was about the use of ivermectin to Torino, Italy control an ongoing scabies outbreak in wild free-ranging Full list of author information is available at the end of the article © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat​iveco​ mmons​.org/licen​ses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/publi​cdoma​in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Moroni et al. Parasites Vectors (2020) 13:471 Page 2 of 4 populations. For example, the studies of Skerratt et al. [9] of reaching the required percentage of the population and Ruykys et al. [10] were largely conducted on wom- with any specific treatment or measure [23]. Individual- bats (Vombatus ursinus and Lasiorhinus latifrons, respec- ized pharmacological therapies, however, are desirable tively) kept in captivity until their recovery. On the other for vulnerable or endangered species where the com- hand, Kalema-Zikusoka et al. [11] worked with a group plete recovery of specific individuals is decisive for spe- of four free-ranging gorillas (Gorilla beringei) habitu- cies recovering (e.g. see an example for the Iberian lynx, ated to human presence which facilitated their approach Lynx pardinus [24], or for the black bear, Ursus ameri- and treatment. Similarly, Chhangani et al. [12], treated canus [25]). However, in abundant non-threatened and a troop of Hanuman langurs (Semnopithecus entellus) widespread populations with a high prevalence of sca- living close to human habitations and religious places. bies, it is unlikely that any individual approach would Expanding urbanization and habitat loss, are leading to reach the necessary proportion of the population to increasingly common human-wildlife interfaces [13], and prevent transmission and reinfection. This is even as a result, much of the free-ranging wildlife identified as more evident for ivermectin due to the need for mul- suffering from sarcoptic mange and becoming candidates tiple doses to achieve a complete recovery and the total for treatment might be habituated to humans to varying elimination of all mites from the host and the environ- degrees. ment, although other long-acting drugs could be a bet- Rajkovic-Janje et al. [14] focused on the use of ivermec- ter option. Nevertheless, the environmental and public tin for endoparasite control in the wild boar. Sarcoptic health concerns of massive antiparasitic drug release in mange was detected only in skin samples collected after the environment would still persist [23]. the necropsy of four piglets. Moreover, sarcoptic mange While of recognized limited efficacy, selective culling can occur subclinically in this species [15] and others, of clinically affected individuals is also a common strat- and therefore the lack of clinical signs after the ivermec- egy in epizootic outbreak scenarios in free-ranging wild- tin treatment is not always a reliable indicator of recov- life [26]. However, this population management measure ery. Gakuya et al. [16], however, showed the outcomes is not free of disadvantages, such as the culling of indi- of successful ivermectin treatment of endemic scabies viduals recovering from scabies [27] in detriment of the in Thomson’s gazelles (Eudorcas thomsonii) and chee- host population viability, as well as the possible objec- tahs (Acinonyx jubatus) from the Masai Mara National tions from the public opinion in some particular species Park. The peak of scabies prevalence here ranged from considered national icon, such as koalas (Phascolarctos 7.4% (n = 10 scabietic gazelles) to 28% (n = 2 scabietic cinereus) and wombats in Australia. cheetahs) affecting a small number of individuals that It is also important to acknowledge the potential for were captured and ear-tagged for potential re-treatment. non-target environmental effects of mass administra- Even though that work was representing an outbreak in tion of ivermectin. Avermectins are excreted during four free-ranging wildlife, the numbers of affected individuals days post-treatment and it can be detected in feces for are far from those recorded during scabies outbreaks in up to 40 days post-defecation [28] and for more than one European fauna, e.g. the Northern chamois (Rupicapra year in reindeer pastures [29]. In soil, ivermectin shows rupicapra; n = 1696 affected individuals, 16.6% of the a half-life degradation between 7 and 217 days, depend- chamois population [17, 18]), or the Iberian ibex (Capra ing on the solar radiation [3]. Once on the environment, pyrenaica; c.7695 scabietic individuals, 80% of the ibex this drug has pre-lethal consequences for dung beetles population in Sierra de Cazorla [19] and 3382 scabietic [30] and for other dung-dwelling invertebrates [3]. If the individuals, 23% of Sierra Nevada ibex population [20]). drug is delivered orally in feeding stuff, as per common Pharmacological treatment of mange in wild animals practice in game ungulate populations in Spain, soil con- mostly produces individual healing, but its effects on tamination and thus the potential effects of ivermectin achieving control or eradication in a population are on other terrestrial fauna, and possibly food chain effects, mostly inconclusive [21]. Therefore, gathering more could be expected not only through fecal contamination information on the population and environmental but through the drug preparation itself. On the other effects and on the consequences of massive antipara- hand, game treatment would limit venison consump- sitic treatments has been recently recommended, tion, as ivermectin withdrawal time in edible tissues may approaching the management of sarcoptic mange in vary from 18 to 48 days depending on the administration wildlife populations from a wider ecological perspec- route [7, 23, 31]. Finally, another concern about the use tive [22]. As opposed to the individual approach revised of ivermectin for scabies control in wildlife is the drug by Rowe et al. [1], the success of scabies control in resistance phenomenon recently described in human sca- free-ranging wildlife depends on the size of the tar- bies [32, 33] and also suspected in companion animals get population, scabies prevalence, and the feasibility [34]. Moroni et al. Parasites Vectors (2020) 13:471 Page 3 of 4 In line with Rowe et al. [1], little is known about the References 1. Rowe ML, Whiteley PL, Carver S. 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