S. Love

Pathogenicity of cyathostome infection

Cyathostomes are now the principle parasitic pathogen of the horse: a remarkable transformation during the last 25 years from virtual obscurity to focus of attention in equine parasitology. This rise to prominence coincides with the marked decrease in prevalence of large strongyle infections as a result of widespread use of modern anthelmintic compounds. On the basis that strongyle-associated diseases continue to commonly occur in the absence of these large strongyle species, clinical attention has turned to the pathogenicity of cyathostomes. Although many horses harbour burdens of tens of thousands of cyathostomes without developing detectable illness, these parasites can result in an inflammatory enteropathy affecting the caecum and colon. Although the principle clinical effect of cyathostomosis is weight loss, affected individuals may exhibit other signs including diarrhoea and/or subcutaneous oedema and/or pyrexia. Clinical cyathostomosis occurs more commonly in young horses in late winter/early spring but there is lifelong susceptibility to cyathostomes and they can cause clinical disease in any age of horse during any season. Animals with cyathostomosis often develop hypoalbuminaemia and/or neutrophilia but there are no clinicopathological features specific for the disease. Experimental infections with cyathostomes have resulted in both clinical and pathological features similar to those of naturally-occuring cyathostomosis cases. From the experimental infection studies, it is evident that cyathostomes are pathogenic at times of both penetration into and emergence from the large intestinal mucosa. An unusual feature of cyathostome biology is the propensity for arrested larval development within the large intestinal mucosa for more than 2 years. From limited studies it appears that this arrested larval development is favoured by: feedback from luminal to mucosal worms; larger size of challenge dose of larvae and trickle (versus single bolus) infection. During arrested larval development cyathostomes have minimal susceptibility to all anthelmintic compounds, thus, limiting the effectiveness of therapeutic and/or control strategies. Although, the relative importance of individual cyathostomes is not known, the development of species-specific DNA methods for identification of cyathostomes provides a means by which the pathogenicity of different species might be established.

Prevalence of obesity in riding horses in Scotland

OBESITY is a serious and largely underreported equine welfare issue. Obese horses are predisposed to the development of pathological conditions including laminitis, hyperlipaemia and strangulating lipoma ([Watson and others 1992][1], [Treiber and others 2006][2]). Obese horses may also be more

Sentinel practice-based survey of the management and health of horses in northern Britain

Details of the management, feeding, level of activity and routine health care of horses in Scotland and the five northernmost counties in England were recorded through a stratified random sample of horse owners who had responded to a previous survey. Sixty-eight per cent of the horses were kept where their owners resided, and 32 per cent were kept away from the owners home. More than 99 per cent were turned out to grazing for at least part of the year and 81 per cent were stabled for at least part of the time, most commonly bedded on straw (50 per cent) or shavings (34 per cent). Hay was fed to 87 per cent, sugar beet pulp to 64 per cent and commercially prepared concentrate mixes to 60 per cent of the horses. Hacking was the most popular activity (52 per cent of horses) followed by riding/pony club events (28 per cent) and showing (21 per cent). The majority of the horses were involved in more than one activity. There were an estimated 0-88 veterinary visits per horse per year and 29 per cent of the horses were reported to suffer from at least one permanent or recurrent health disorder. The median annual numbers of administrations of vaccines (influenza and tetanus) and anthelmintics were one and seven respectively per horse, and each horse was shod a median seven times. There were significant differences in the management of horses kept in different types of premises and in areas of different human population density.

Equine Cushing's disease.

In the horse, adenomata of the pairs intermedia of the pituitary gland have been associated with the distinct clinical entity of Cushings disease which arises largely as a result of excessive secretion of adrenocorticotropin (ACTH) or other proopiomelanocortin (POMC) peptides. Pars intermedia peptide secretion is under dopaminergic control and compounds such as pergolide or bromocriptine, which are dopamine agonists, can palliate the clinical signs. A variety of endocrinological abnormalities, relevant to both pathogenesis and diagnosis, may be demonstrated in equine Cushings disease, including hyperadrenocorticism, peripheral insulin resistance and excessive POMC-peptide secretion from the pituitary gland. Preliminary studies on carbohydrate metabolism suggest that quantification of insulin activity may be a useful prognostic index in cases of equine Cushings disease, and that insulin therapy of secondary diabetes mellitus may be indicated in some cases.

Sequence variants of bovine papillomavirus E5 detected in equine sarcoids

The equine sarcoid, one of the most common dermatological lesions in equids, is a benign, locally invasive dermal fibroblastic lesion. Previous studies have suggested an association with two bovine papilloma virus (BPV) types, BPV-1 and BPV-2. In the present study, we examined sarcoids from horses from two geographical areas, Switzerland and the UK, for the major transforming gene of BPV, E5. We detected BPV DNA for the E5 open reading frame and viral E5 RNA transcripts in most sarcoids. Sequence analysis of the E5 open reading frame of sarcoid-associated BPV detected several unique DNA sequence variants, three of which resulted in sarcoid specific amino acid sequence variations. It is unclear if these sequence variants contribute to the unique clinical presentation of the sarcoid. However, our work provides further evidence of the association between BPV and sarcoid development and the direct involvement of the virus in the pathogenesis of sarcoids.

Clinicopathological features of equine primary hepatic disease: a review of 50 cases

The clinicopathological features of 50 cases of equine hepatic disease were reviewed. There was a wide range of clinical signs and at least 50 per cent of the animals exhibited either dull demeanour, anorexia, abdominal pain, cerebral dysfunction and/or weight loss. Life-threatening complications of hepatic failure recorded were: gastric impaction in 10 cases, bilateral laryngeal paralysis in seven cases and coagulopathy in five cases. All the cases had high activities of gamma-glutamyl transferase (GGT) and most had high activities of glutamate dehydrogenase (GLDH) and high concentrations of bile acids. Fewer of the horses had abnormal concentrations of bilirubin, albumin and globulin. The horses that were euthanased or died had significantly higher concentrations of GGT, GLDH and bile acids than the survivors. There were biochemical data for 18 cases with signs of hepatic encephalopathy, all of them had plasma ammonia levels greater than 90 μmol/litre but this was not significantly correlated with the clinical severity of the condition. Half of the cases with hepatic encephalopathy were hyperglycaemic, none was hypoglycaemic, and none had abnormally low levels of plasma urea.

The development of naturally acquired cyathostome infection in ponies.

Groups of animals of different ages and experience of previous parasite exposure were allowed to graze a single pasture for 5 weeks in autumn (7 October to 11 November). There was evidence that previous exposure modified cyathostome development, as acquired burdens in foals which had previously grazed were smaller and developed more slowly than those of helminth-naive animals of the same age. The burdens acquired by yearling and adult ponies were of a similar size to those of the previously grazed foals, but the incidence of arrested development was higher in the younger groups of foals and yearlings when compared with adults. Further evidence of an effect of age on cyathostome development was that the level of faecal egg output of the adult ponies was lower than in the groups of young animals.

Demographic characteristics of the equine population of northern Britain.

The size, composition and distribution of the equine population of Scotland and the five northernmost counties in England were estimated through a series of mailed questionnaire surveys of sentinel veterinary practices and horse owners. An estimated 96,622 equine animals were kept by an estimated 26,114 owners. The mean (sd) age of the population was 11.0 (7.5) years (range one month to 37 years). Thoroughbred or thoroughbred-cross animals were the most numerous, constituting 30 per cent (95 per cent confidence interval 27 to 33 per cent) of the total population. The ratio of males.females was 1:1.

The effects of xylazine, detomidine, acepromazine and butorphanol on equine solid phase gastric emptying rate

The aim of this study was to measure the effects of specific commonly used sedative protocols on equine solid phase gastric emptying rate, using the 13C-octanoic acid breath test (13C-OABT). The gastric emptying of a standard 13C-labelled test meal was measured once weekly in 8 mature horses over two 4 week treatment periods. Each horse acted as its own control. In treatment Period 1, saline (2 ml i.v.), xylazine (0.5 mg/kg i.v.), detomidine (0.01 mg/kg i.v.) or detomidine/butorphanol combination (0.01/0.02 mg/kg i.v.) was administered in randomised order after ingestion of the test meal. During treatment Period 2, test meal consumption was followed by saline, xylazine (1.0 mg/kg i.v.), or detomidine (0.03 mg/kg i.v.) administration, or preceded by acepromazine (0.05 mg/kg i.m.) in randomised order. The 13C:12C ratio of sequential expiratory breath samples was determined by isotope ratio mass spectrometry, and used to measure the gastric half-emptying time, t 1/2, and duration of the lag phase, t lag, for each of the 64 tests. In treatment Period 1, detomidine/butorphanol prolonged both t 1/2 and t lag with respect to xylazine 0.5 mg/kg and the saline control (P < 0.05). In Period 2, detomidine 0.03 mg/kg delayed each parameter with respect to saline, acepromazine and xylazine 1.0 mg/kg (P < 0.001). Xylazine 1.0 mg/kg also lengthened t lag relative to the saline control (P = 0.0004), but did not cause a significant change in t 1/2. Comparison of treatment periods showed that the inhibitory effect of detomidine on gastric emptying rate was dose related (P<0.05). These findings may have clinical significance for case selection when these agents are used for purposes of sedation and/or analgesia.

Antigen-specific IgG(T) responses in natural and experimental cyathostominae infection in horses

Equine clinical larval cyathostominosis is caused by simultaneous mass emergence of previously inhibited larvae from the mucosa of the colon. Clinical signs include diarrhoea, colic, weight loss and malaise, and in up to 50% of cases, the disease results in death. Cyathostominae spend a large part of their life cycle as larval stages in the intestinal mucosa. Definitive diagnosis is difficult due to the lack of diagnostic methods for pre-patent infection. In the present study, the enzyme-linked immunosorbent assay (ELISA) was used to investigate isotype responses to larval cyathostominae somatic antigen. Measurement of anti-larval IgG(T) responses appeared to have the most immunodiagnostic potential. An increase in IgG(T) response was detected to crude larval antigen by 5 weeks post-infection (PI) in individual infected ponies. Subsequently, IgG(T) responses to larval and adult somatic extracts were examined by Western blotting using sera from experimentally-infected horses and helminth-naive animals (n=6). Two antigen complexes, designated A and B, in larval somatic antigen were recognised specifically by the infected animals by 7 weeks PI. Sera taken from 23 endemically-infected animals, whose cyathostominae burdens had been enumerated, were also used to identify putative diagnostic antigens. Eighteen horses had positive mucosal worm burdens (range 723-3,595,725) and all but two of these animals had serum IgG(T) antibody specific to either complex. Moreover, IgG(T) responses specific to antigen complexes A and B were absent in all five parasite negative horses that were tested. Serum IgG(T) responses to either of the two complexes were identified in five clinical cases tested. IgG(T) responses to adult antigen somatic extracts were more heterogeneous, with no clear pattern between experimentally-infected ponies and helminth-free controls. The results indicate that increases in serum IgG(T) to mucosal larvae occur in the pre-patent period and that two antigenic complexes within somatic preparations of these stages have immunodiagnostic potential.