Alleviating lesions of chronic progressive lymphedema in Belgian draft horses by successfully treating Chorioptes bovis infestation with moxidectin 0.5% pour-on. 2023

Marieke Brys, and Edwin Claerebout, and Koen Chiers
Laboratory of Veterinary Pathology, Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium. Electronic address: Marieke.Brys@UGent.be.

The aim of this prospective, randomized, single-blinded, and placebo-controlled clinical trial was to investigate the efficacy of a moxidectin pour-on solution for the treatment of Chorioptes bovis infestation in Belgian draft horses, and in addition, to evaluate the effect of this treatment on the clinical signs and lesions associated with chronic progressive lymphedema (CPL). Nineteen privately owned Belgian draft horses were randomly assigned to either a treatment group (moxidectin pour-on formulation, n = 10) or a placebo group (phosphate-buffered saline (PBS), n = 9). On Day 0, all 19 horses tested positive for the presence of C. bovis in superficial skin scrapings. Prior to treatment, all feathering on the distal limbs of the horses was clipped. Treatment was applied twice (Day 0 and 7). Pour-on moxidectin (Cydectin 0.5% Pour-On; Zoetis) was evenly distributed over the distal legs of the horses at a dose of 1.5 mg moxidectin/kg body weight. Animals in the placebo group were treated with PBS. Pretreatment and follow-up examinations consisted of counting living mites in superficial skin scrapings, scoring pruritus, and scoring mange-associated and CPL-associated lesions (skinfold score and skin lesion score). Horses in the placebo group and moxidectin group were followed up to 8 weeks and 24 weeks after the first treatment, respectively. On Day 14, no living mites were found in any of the horses in the moxidectin group (p = 0.013). These horses continued to remain free of mites, until the final sampling conducted at 24 weeks following the initial application of moxidectin, when three horses again showed living mites in skin scrapings. Treatment with moxidectin resulted in a significant reduction of both CPL-associated skin lesion scores (p = 0.003) and pruritus scores (p = 0.001) after only seven days. By Day 56, still no signs of pruritus (p < 0.0001) were detected, with significant improvement of mange-associated lesions (p < 0.0001). Although the skinfold score did not show a significant reduction by Day 56, the score for skin lesions associated with CPL had significantly improved (p < 0.0001). In conclusion, the results of this study demonstrate that pour-on moxidectin, at a high dose and applied directly to the mite predilection site, was an effective treatment for C. bovis infestation in feathered draft horses, providing positive effects on CPL lesions, pruritus and mange-associated lesions. Furthermore, these findings emphasize the therapeutic significance of addressing mange in the management of CPL-affected draft horses.

UI MeSH Term Description Entries
D007306 Insecticides Pesticides designed to control insects that are harmful to man. The insects may be directly harmful, as those acting as disease vectors, or indirectly harmful, as destroyers of crops, food products, or textile fabrics. Insecticide
D008209 Lymphedema Edema due to obstruction of lymph vessels or disorders of the lymph nodes. Milroy's Disease,Congenital Familial Lymphedema,Congenital Hereditary Lymphedema,Early Onset Lymphedema,Hereditary Lymphedema,Hereditary Lymphedema 1,Hereditary Lymphedema Type I,Lymphedema, Early-Onset,Lymphedema, Hereditary, Ia,Milroy Disease,Nonne-Milroy Disease,Nonne-Milroy Lymphedema,Nonne-Milroy-Meige Disease,Primary Congenital Lymphedema,Congenital Hereditary Lymphedemas,Congenital Lymphedema, Primary,Congenital Lymphedemas, Primary,Early Onset Lymphedemas,Early-Onset Lymphedema,Early-Onset Lymphedemas,Hereditary Lymphedema 1s,Hereditary Lymphedema, Congenital,Hereditary Lymphedemas,Hereditary Lymphedemas, Congenital,Lymphedema, Congenital Hereditary,Lymphedema, Early Onset,Lymphedema, Hereditary,Lymphedema, Nonne-Milroy,Lymphedema, Primary Congenital,Lymphedemas,Lymphedemas, Congenital Hereditary,Lymphedemas, Early Onset,Lymphedemas, Early-Onset,Lymphedemas, Hereditary,Lymphedemas, Primary Congenital,Milroys Disease,Nonne Milroy Disease,Nonne Milroy Lymphedema,Nonne Milroy Meige Disease,Primary Congenital Lymphedemas
D008924 Mite Infestations Infestations with arthropods of the subclass ACARI, superorder Acariformes. Acariasis,Mange,Infestation, Mite,Infestations, Mite,Mite Infestation
D008925 Mites Any arthropod of the subclass ACARI except the TICKS. They are minute animals related to the spiders, usually having transparent or semitransparent bodies. They may be parasitic on humans and domestic animals, producing various irritations of the skin (MITE INFESTATIONS). Many mite species are important to human and veterinary medicine as both parasite and vector. Mites also infest plants. Acarus,Mite
D011446 Prospective Studies Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group. Prospective Study,Studies, Prospective,Study, Prospective
D011537 Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Itching,Pruritis
D002908 Chronic Disease Diseases which have one or more of the following characteristics: they are permanent, leave residual disability, are caused by nonreversible pathological alteration, require special training of the patient for rehabilitation, or may be expected to require a long period of supervision, observation, or care (Dictionary of Health Services Management, 2d ed). For epidemiological studies chronic disease often includes HEART DISEASES; STROKE; CANCER; and diabetes (DIABETES MELLITUS, TYPE 2). Chronic Condition,Chronic Illness,Chronically Ill,Chronic Conditions,Chronic Diseases,Chronic Illnesses,Condition, Chronic,Disease, Chronic,Illness, Chronic
D006734 Horse Diseases Diseases of domestic and wild horses of the species Equus caballus. Equine Diseases,Disease, Equine,Disease, Horse,Diseases, Equine,Diseases, Horse,Equine Disease,Horse Disease
D006736 Horses Large, hoofed mammals of the family EQUIDAE. Horses are active day and night with most of the day spent seeking and consuming food. Feeding peaks occur in the early morning and late afternoon, and there are several daily periods of rest. Equus caballus,Equus przewalskii,Horse, Domestic,Domestic Horse,Domestic Horses,Horse,Horses, Domestic
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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