Parasite Occurrence and Parasite Management in Swedish Horses Presenting with Gastrointestinal Disease—A Case–Control Study

Abstract

Simple Summary: Abdominal pain, colic, is a common clinical sign in horses, sometimes reflecting life-threatening disease. One cause of colic is parasitic infection of the gut. Various drugs, anthelmintics, can be used to reduce or eliminate such parasites. However, frequent use has led to problems of drug resistance, whereby many countries now allow anthelmintics to be used on a prescription-only basis. In Sweden, this has led to a concern that parasitic-related colic in horses is increasing. This study aimed to investigate whether horses with colic differed in parasitological status compared to horses without colic. A secondary aim was to collect information regarding current parasite control measures used by horse owners. Exposure to S. vulgaris, a parasite with the potential to cause life-threatening disease, appeared high as determined by the presence of antibodies in the blood. Horses with inflammation in the abdominal cavity had higher antibody levels than other causes of colic. Despite new legislation, 29% of owners did not use fecal analyses for parasites and the use of extended methods to diagnose specific parasites was low. Also, owners rarely used alternative methods to reduce the pasture parasite burden. The study suggests a need for education in the use of both fecal analyses and pasture management.Abstract: All grazing horses are exposed to intestinal parasites, which have the potential to cause gastrointestinal disease. In Sweden, there is a concern about an increase in parasite-related equine gastrointestinal disease, in particular Strongylus vulgaris, since the implementation of prescription-only anthelmintics approximately 10 years ago. In a prospective case-control study, parasitological status, using fecal analyses for strongyle egg counts, the presence of Anoplocephala perfoliata eggs and S. vulgaris Polymerase chain reaction (PCR) as well as serology for S. vulgaris, were compared between horses presenting with or without gastrointestinal disease at a University hospital during a one-year period. Information regarding anthelmintic routines and pasture management was gathered with an owner-filled questionnaire. Although the prevalence of S. vulgaris PCR was 5.5%, 62% of horses were positive in the enzyme-linked immunosorbent assay (ELISA) test and horses with peritonitis showed higher antibody levels for S. vulgaris, as compared to other diagnoses or controls. Overall, 36% of the horse owners used only fecal egg counts (FEC), 32% used FEC combined with specific diagnostics for S. vulgaris or A. perfoliata, and 29% dewormed routinely without prior parasite diagnostics. Effective management methods to reduce the parasitic burden on pastures were rare and considering exposure to S. vulgaris appears high; the study indicates a need for education in specific fecal diagnostics and pasture management.

Comparative Analysis of Intestinal Helminth Infections in Colic and Non-Colic Control Equine Patients

“…Noteworthy, neither our data nor that of the latter Swedish study obtained any statistical association between colic and S. vulgaris positivity. This is in agreement with previous investigations on the occurrence of S. vulgaris [ 37 ] and also cyathostomins [ 38 , 39 ] in colic versus control horses. However, there are some publications describing the opposite, such as S. vulgaris -associated colic due to non-strangulating intestinal infarction [ 3 ].…”

“…As a matter of fact, recent studies have shown that, in countries with an increased use of selective treatment approaches such as Sweden and Denmark, the S. vulgaris prevalence increased upon the widespread application of this strategy [ 13 , 14 ]. This is in agreement with recent investigations on the occurrence of cyathostomins [ 38 ] or S. vulgaris [ 37 ] in colic versus control horses.…”

“…The effect of anthelmintic treatment on the strongyle population was documented by the observation that horses receiving treatments less than eight weeks prior were less prone to shedding strongyle eggs. Similar observations were made by Hedberg-Alm et al [ 37 ], who reported that if treatment was more than three months prior, the risk of higher strongyle epg counts were significantly higher.…”

Helminth infections in Italian donkeys: Strongylus vulgaris more common than Dictyocaulus arnfieldi

“…The low anthelmintic treatment intensity reported in this study could be a risk factor for S . vulgaris infection in donkeys as also demonstrated in horses (Nielsen et al ., 2012; Hedberg-Alm et al ., 2020). Considering the high prevalence of S .…”

“…was low (1.0%) but in agreement with data reported in donkeys in few studies on the presence of tapeworms in Europe (Matthews & Burden, 2013). In horses, Anoplocephala perfoliata was detected with higher prevalence (Tzelos et al ., 2019; Hedberg-Alm et al ., 2020). This low prevalence could be correlated with the irregular excretion of tapeworm eggs in the faeces (Gasser et al ., 2005).…”