Strongylus vulgaris : samband med äggurskiljning, ålder och bekämpningsåtgärder
Abstract: Strongylus vulgaris, or large strongyles, is the most dangerous of the equine endoparasites. Its larvae can cause lethal intestinal infarctions when they move through the horse’s blood vessels. Because of its pathogenicity, deworming is recommended when infection is confirmed, regardless of quantity (compare with small strongyles where a small number of worms is tolerated at an individual level). Single deworming of the infected horse may not, however, be enough to eliminate infection entirely. The aim of this study was to explore correlations between occurrences of S. vulgaris and egg per gram faeces, age, number of horses on the farm, and number of months between deworming and faecal sample, respectively. The aim was also to observe 16 S. vulgaris-positive farms during one year to explore which strategy was the most effective in eliminating the parasites, what suggestions horse owners received regarding parasite control, and which advise they chose to follow and why. The study was performed as two sub-studies. In sub-study one, data from over 700 horses were analysed regarding correlation between occurrence of S. vulgaris, EPG and age. Data from 568 S. vulgaris-positive horses from January 2016 to March 2017 was collected from Equippo lab. Data from an additional 149 horses was collected from sub-study two which showed that S. vulgaris can be found in horses from all categories of age and EPG. In sub-study two, 16 farms were studied, all S. vulgaris-positive in the spring of 2017. During the spring of 2018, new faecal samples were collected and analysed regarding EPG and occurrence of S. vulgaris. 12 of the 16 farms were S. vulgaris-negative in 2018. The participants also answered a questionnaire regarding what advise they had been given regarding parasite control, what advise they had followed, and what parasite controlling routines the farm had before entering the study. The result of the questionnaire study shows that different veterinarians gave consistent advice regarding deworming, but inconsistent or non-existing advice regarding pasture hygiene and mucking of paddocks. The horse owners had most commonly used macrocyclic lactones for deworming, dewormed all horses in the stable multiple times, mocked out the paddock rarely or not at all, and had not performed any measures for pasture hygiene. The majority of the horse owners stated that their veterinarian was the most important influence when choosing parasite control routines. The most common reason for not following the veterinarian’s advice was lack of fields or lack of time. All of the farms that did not manage to eliminate S. vulgaris during the study period did not perform any measure of pasture hygiene and had not analysed faeces for S. vulgaris routinely before entering the study. In sub-study two, the number of horses on the farm and the time between deworming and faecal samples were also analysed. Farms with large numbers of horses had more difficulties eliminating S. vulgaris. On S. vulgaris-positive farms the time from deworming to faecal sample was on average shorter. The result of this study shows that S. vulgaris could be found on horses of any age and EPGlevel. Stables with many horses had more difficulties eliminating S. vulgaris. The horse owners stated that recommendations from veterinarians where important when determining a course of action, but that is also depended on individual the veterinarians. However, not everyone followed the recommendations. The major focus was on mucking of paddocks and only a few of the horse owners performed any anti-parasite measures on pastures.
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