https://www.journalsajp.com/index.php/SAJP <p style="text-align: justify;"><strong>South Asian Journal of Parasitology</strong>&nbsp;aims to publish high-quality papers (<a href="/index.php/SAJP/general-guideline-for-authors">Click here for Types of paper</a>)&nbsp;all areas of basic and applied parasitology.</p> <p style="text-align: justify;">This is an open-access journal which means that all content is freely available without charge to the user or his/her institution. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This is in accordance with the BOAI definition of open access.</p> South Asian Journal of Parasitology en-US South Asian Journal of Parasitology https://www.journalsajp.com/index.php/SAJP/article/view/308 <p>Sarcoptic mange caused by <em>Sarcoptes scabiei</em> var. <em>canis</em> is a contagious canine dermatosis, and apparent ivermectin treatment failure raises concern about reduced acaricide susceptibility. This study evaluated the clinical response to a three-dose ivermectin protocol and compared <em>in vitro</em> ivermectin susceptibility between mites recovered from clinically refractory dogs and a reference susceptible isolate. Thirty naturally infested dogs received subcutaneous ivermectin at 300 µg/kg on days 0, 14, and 28, with serial skin scrapings and pruritus assessment through day 42. Mites from refractory dogs were pooled as a field-resistant isolate and tested against a susceptible isolate using ivermectin contact bioassays. Twenty-four dogs (80%) became mite-negative with more than 75% pruritus resolution, whereas six dogs (20%) remained mite-positive with less than 25% pruritus reduction and were classified as clinically refractory. At 1% ivermectin, 24-hour mortality was 34% in the field-resistant isolate compared with 91% in the susceptible isolate. The 24-hour LC₅₀ was 0.71% for the field-resistant isolate and 0.09% for the susceptible isolate, corresponding to a resistance ratio of approximately 7.9. LT₅₀ at 1% increased from 2.1 to 9.4 hours. These findings are consistent with a marked phenotypic reduction in ivermectin susceptibility associated with clinical treatment failure and support confirmatory follow-up testing, careful acaricide selection, and continued surveillance.</p> Sirigireddy Sivajothi Bhavanam Sudhakara Reddy Dadireddy Narmada Raghavi Copyright (c) 2026 Author(s). The licensee is the journal publisher. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2026-09-02 2026-09-02 9 4 662 669 10.9734/sajp/2026/v9i4308