Control of helminth parasites in juvenile horses

Parasite control in juvenile horses remains a substantial challenge for veterinary practitioners and their clients. This age group is at risk for various types of parasitic disease because their worm burdens tend to be larger and more diverse than in mature horses. This contrast is largely attributable to marked differences in relative levels of acquired immunity. Frequent, perennial anthelmintic treatment is not a sustainable approach for parasite control in this age group, but the simple, surveillance‐based parasite control strategies recommended for mature horses are not appropriate for juveniles either. Maneuvering through the early years of a horse's life requires up‐to‐date knowledge about biology and epidemiology of the parasite species in play as well as local evidence regarding the anthelmintic resistance status of each herd. This article provides an overview of the most important helminth parasites to target in a control programme for juvenile horses, and highlights how the target species change as horses age. Young foals (<2 months) are exposed to Strongyloides westeri and Parascaris spp., whereas the primary target parasite in foals between age 2 months and weaning is Parascaris spp. Beyond weaning, the focus shifts away from ascarids, and the targets instead are strongyles and tapeworms. Gasterophilus spp. and Oxyuris equi are also discussed.     

Caecal intussusceptions and typhlocolitis in horses with severe Gastrodiscus aegyptiacus infestation

The intestinal trematode Gastrodiscus aegyptiacus (G. aegyptiacus) has been recognised in equids around the world for many years, but its pathogenicity is yet to be confirmed. This report describes seven cases of severe G. aegyptiacus infestation, including six cases of caecal intussusception.     

Glanders and the risk for its introduction through the international movement of horses

Glanders is the contagious zoonotic disease caused by infection with Burkholderia mallei. It affects primarily horses, donkeys and mules. The disease was eradicated from large areas of the Western world in the early 20th century, but, over the last 10–20 years, has emerged and re‐emerged in areas in which it was previously unknown or had been eradicated. Although glanders was previously thought to manifest in only acute or chronic presentations, it now appears that B. mallei can produce latent infections similar to those caused by Burkholderia pseudomallei. These latent infections may or may not be detectable by current diagnostic tests. The diagnostic test currently recommended by the World Organisation for Animal Health (Office International des Epizooties [OIE]) for international trade in equids is the complement fixation test (CFT). This test has been shown to have varying sensitivities and specificities depending on the antigen and methodology used. False positives are problematic for the horse‐owner and veterinary authority, whereas false negatives may allow the reintroduction of B. mallei into B. mallei‐free areas. These gaps in knowledge of the epidemiology of glanders, and weaknesses in its diagnosis, coupled with the increased movement of equids, indicate that infection with B. mallei remains a major risk in the context of international movement of equids.     

Parasites observed in the proximal alimentary tract of a Przewalski's horse in China

This article reports a Przewalski's horse from the Kalamaili Nature Reserve (KNR) in China transported to our institute to determine the cause of death. The animal had been subjected to necropsy before being transported to our institute; the entire digestive tract was removed but not opened to reduce the possible loss of parasites. During examination, ascarids in the intestines and bots in the oral cavity and stomach were observed. The parasites were identified according to an identification key and enumerated. The ascarids were identified as Parascaris spp. and were associated with a volvulus, resulting in intestinal obstruction. A total of two (stomach), one (duodenum) and 106 (intestines) Parascaris spp. were counted. Bots in the digestive tract were identified as third stage larvae of Gasterophilus pecorum (G. pecorum), Gasterophilus nigricornis (G. nigricornis) and Gasterophilus nasalis (G. nasalis), which may have been associated with stomach ulcers suffered by the horse. Attached to the lining of the oral cavity and stomach were 331 and 2014, respectively, larvae of G. pecorum, while in the duodenum there were 23 third stage larvae of G. nigricornis and 20 third stage larvae of G. nasalis. Therefore, the possibility of the presence of these parasites should not be overlooked in Przewalski horses as these parasites may be responsible for severe clinical signs in infected animals.     

Dietary effect of lemon verbena extract on selected blood parameters and on plasma oxidative profile in Avelignese horses

The effect of Lippia citriodora extract on selected blood parameters and on plasma oxidative markers in Avelignese horses was evaluated. Twenty‐four horses were divided into three groups, consisting of eight animals each. Results of two experimental groups, 0.5 mg of verbascoside per kg of metabolic body weight (bw^0.75) in the low‐dose group (LVB) and 1.0 mg of verbascoside per kg of metabolic body weight (bw^0.75) in the high‐dose group (HVB), were compared to the control group (CON). Groups fed L. citriodora extract (HVB and LVB) showed a significant decrease in triglycerides, total cholesterol and LDL cholesterol (p < .01), bilirubin, and transaminases (p < .05), and an increase in HDL cholesterol (p < .01) compared to the CON group. Oxidative status was improved due to significant decrease in plasma concentration of ROMs and TBARS (p < .01) and increase in levels of vitamin A and vitamin E (p < .01). Based on obtained results, it is assumed that dietary supplementation with L. citriodora extract might find a useful application in horse feeding, with positive impact observed in blood parameters and plasma oxidative markers, with beneficial effects on the physiological welfare of livestock animals.     

Pharmacokinetics of harpagoside in horses after intragastric administration of a Devil's claw (Harpagophytum procumbens) extract

Devil's claw is used for the treatment of inflammatory symptoms and degenerative disorders in horses since many years, but without the substantive pharmacokinetic data. The pharmacokinetic parameters of harpagoside, the main active constituent of Harpagophytum procumbens DC ex Meisn., were evaluated in equine plasma after administration of Harpagophytum extract FB 8858 in an open, single‐dose, two‐treatment, two‐period, randomized cross‐over design. Six horses received a single dose of Harpagophytum extract, corresponding to 5 mg/kg BM harpagoside, and after 7 days washout period, 10 mg/kg BM harpagoside via nasogastric tube. Plasma samples at certain time points (before and 0–24 hr after administration) were collected, cleaned up by solid‐phase extraction, and harpagoside concentrations were determined by LC‐MS/MS using apigenin‐7‐glucoside as internal standard. Plasma concentration‐time data and relevant parameters were described by noncompartmental model through PKSolver software. Harpagoside could be detected up to 9 hr after administration. C_max was found at 25.59 and 55.46 ng/ml, t_1/2 at 2.53 and 2.32 hr, respectively, and t_max at 1 hr in both trials. AUC_0–inf was 70.46 and 117.85 ng hr ml^?1, respectively. A proportional relationship between dose, C_max and AUC was observed. Distribution (V_z/F) was 259.04 and 283.83 L/kg and clearance (CL/F) 70.96 and 84.86 L hr^?1 kg^?1, respectively. Treatment of horses with Harpagophytum extract did not cause any clinically detectable side effects.     

Endogenous mycotic endophthalmitis in a dog with candiduria and Evans syndrome

This report describes the clinical presentation, diagnosis, histologic lesions, and outcome of endogenous mycotic endophthalmitis secondary to candiduria in a three‐year‐old female spayed Dachshund. The dog was being treated for Evans syndrome for one month prior to being diagnosed with candiduria and fibrinous uveitis OS. The left eye was enucleated due to secondary glaucoma, and the fungal urinary tract infection was treated successfully. Uveitis developed in the contralateral eye with relapse of the urinary tract infection in the following weeks. The right eye was medically managed until secondary glaucoma developed and was subsequently enucleated. Histopathology of both eyes showed evidence of endophthalmitis with intralesional fungal organisms, consistent with Candida spp. Ocular candidiasis is rare in dogs. To the authors' knowledge, this is the first report of endogenous mycotic endophthalmitis with concurrent candiduria in a dog.