Nonstrangulating intestinal infarctions associated with Strongylus vulgaris: Clinical presentation and treatment outcomes of 30 horses (2008-2016)

BACKGROUND

Strongylus vulgaris is re-emerging in horses kept under surveillance-based parasite control regimens. Information on nonstrangulating intestinal infarction associated with S. vulgaris is needed to improve recognition of the condition.

OBJECTIVE

To describe the typical clinical presentation, laboratory findings, gross pathology, treatment and outcome of horses with nonstrangulating intestinal infarction.

STUDY DESIGN

Retrospective case series.

METHODS

Nonstrangluating intestinal infarction was diagnosed in 30 horses with a localised intestinal infarction with concurrent signs of S. vulgaris migration and no signs of intestinal strangulation or enterocolitis. Data were obtained from medical records in the period 2008-2016. Long-term follow-up information was obtained by telephonic interviews. Levels of S. vulgaris-specific antibodies were retrospectively assessed. Associations between nonstrangulating intestinal infarction and selected variables were evaluated using Fisher's exact and Mann-Whitney U tests.

RESULTS

The most consistent findings at admission were mild colic of >24 h duration without signs of shock or strangulated intestine, increased peritoneal fluid WBC (>5 × 10⁹ /L), increased serum amyloid A (SAA) concentration and a positive S. vulgaris-specific antibody titre. Medical treatment was attempted in nine horses with none surviving. Exploratory laparotomy was performed in 21 horses. Eleven horses were subjected to euthanasia intraoperatively due to the presumed poor prognosis. Of the nine horses, three (33%) undergoing intestinal resection survived to discharge. The surviving horses were alive and returned to athletic function for at least 2 years following discharge.

MAIN LIMITATIONS

Only nine of the 30 horses underwent resection of the infarcted intestine, and the prognosis for surgical intervention in nonstrangulating intestinal infarction is, therefore, difficult to estimate.

CONCLUSIONS

In areas where S. vulgaris is prevalent, nonstrangulating intestinal infarction should be considered as a differential diagnosis in horses presenting with mild colic and peritonitis. Survival of nonstrangulating intestinal infarction is possible in cases where surgical intervention with resection of the infarcted intestine is feasible. The summary is available in Spanish - see Supporting Information.

Physiologic and systemic acute phase inflammatory responses in young horses repeatedly infected with cyathostomins and Strongylus vulgaris

Migrating Strongylus vulgaris and encysted cyathostomin larvae cause a localized inflammatory response in horses. It is unknown whether these larvae elicit a systemic acute phase response (APR), evidenced by changes in serum amyloid A (SAA), haptoglobin (Hp), iron (Fe), albumin, or albumin/globulin (A/G) ratio. In this study, 28 horses were randomly allocated to receive either pyrantel tartrate or a pelleted placebo formulation in their daily feed. Concurrent with treatment, all the horses were administered 5000 pyrantel-susceptible cyathostomin infective larvae once daily, 5 days a week, for 24 weeks. Beginning in the fifth week, the horses also received 25 S. vulgaris larvae once weekly for the remainder of the study. At regular biweekly intervals, fecal samples were collected for quantitative egg counts, and whole blood and serum samples were collected for measurement of packed cell volume, total protein, albumin, globulin, A/G ratio, SAA, Hp, and Fe. On days 161-164, all the horses were euthanatized and necropsied. Samples were collected for enumeration of total luminal worm burdens, encysted cyathostomin larval populations, and migrating S. vulgaris larvae. Concentrations of Hp, Fe, and A/G ratio were associated significantly with strongyle burdens. Only treated male horses had significant increases in serum albumin. Larval S. vulgaris did not associate with Fe, whereas Fe was associated negatively with both total cyathostomin burdens and encysted L4s. The A/G ratios differed significantly between the two treatment groups. Significant differences between groups and individual time points were also observed for Hp and Fe, whereas SAA concentrations remained low throughout the study. In general, this study illustrated that experimental inoculations with S. vulgaris and cyathostomins may be associated with changes in Hp, Fe, and serum proteins, but not with SAA. Overall, these changes suggest that mixed strongyle infections elicit a mild acute phase reaction.

Effects of osmolytes on hexokinase kinetics combined with macromolecular crowding

We investigated the effect of compatible and non-compatible osmolytes in combination with macromolecular crowding on the kinetics of yeast hexokinase. This was motivated by the fact that almost all studies concerning the osmolyte effects on enzyme activity have been performed in diluted buffer systems, which are far from the physiological conditions within cells, where the cytosol contains several hundred mg protein ml(-1). Four organic (glycerol, betaine, TMAO and urea) and one inorganic (NaCl) osmolyte were tested. It was concluded that the effect of compatible osmolytes (glycerol, betaine and TMAO) on V(max) and K(M) was practically equivalent in pure buffer and in 200-250 mg BSA ml(-1) supporting the view that these small organic osmolytes do minimal perturbance on enzyme function in physiological solutions. The effect of urea on enzyme kinetics was not independent of protein concentration, since the presence of 250 mg BSA ml(-1) partly compensated the perturbing effect of urea. Even though the organic osmolytes glycerol, betaine and TMAO are generally considered compatible with enzyme function, especially glycerol did have a significant effect on hexokinase kinetics, decreasing both k(cat), K(M) and k(cat)/K(M). The osmolytes decreased k(cat)/K(M) in the order: NaCl>Urea>TMAO/glycerol>betaine. For the organic osmolytes this order correlates with the degree of exclusion from protein-water interfaces. Thus, the stronger the exclusion the weaker the perturbing effects on k(cat)/K(M).

Strongyle egg shedding consistency in horses on farms using selective therapy in Denmark

Knowledge of horses that shed the same number of strongyle eggs over time can lead to the optimization of parasite control strategies. This study evaluated shedding of strongyle eggs in 424 horses on 10 farms when a selective anthelmintic treatment regime was used over a 3-year period. Faecal egg counts were performed twice yearly, and horses exceeding 200 eggs per gram (EPG) of faeces were treated. The results are presented as probabilities of the egg count outcome, when two previous egg counts are known. A horse with no strongyle eggs detected in the two previous faecal examinations had an 82% probability of a zero, and a 91% of being below 200 eggs per gram in the third examination. A horse with the two previous egg counts below 200 EPG had an 84% probability of being below 200 EPG the third time as well. When faecal egg counts exceeded 200 EPG on the previous two counts, the probability for a horse exceeding 200 EPG the third time was 59%. In conclusion, these data demonstrate consistent shedding from one grazing season to another in a majority of horses despite treatment of horses exceeding 200 EPG.

Prescription-only anthelmintics--a questionnaire survey of strategies for surveillance and control of equine strongyles in Denmark

In 1999, legislation in Denmark made anthelmintic drugs available only by prescription, and prohibited their use for routine, prophylactic treatment. A questionnaire survey was conducted in 2004 to determine current strategies for surveillance and control of equine strongyles used in Danish equine veterinary practices. Eighty-seven of 170 (51.2%) registered equine veterinary practices responded. Ninety seven percent of the respondents used faecal egg counts for diagnosis and surveillance, and 41% used larval cultures. Logistic regression revealed that the use of larval cultures was positively correlated with numbers of employees (P = 0.013) and the proportion of equine caseload in the practice (P < 0.000). Performing faecal egg counts and treating horses was most frequent during spring, summer and early autumn. Veterinary practices made treatment decisions based on cut-off values ranging from 20 to 500 eggs per gram (EPG) faeces. Ages of horses, clinical suspicions of parasitic disease, or requests by the owners were the most important factors in the strategies for faecal sampling. Less commonly, sampling strategies included all horses on the premises and random sampling. Ninety five percent of the respondents reported treating certain groups of horses without prior faecal analysis, including horses with clinical signs of parasitic disease (77%), foals (84%), horses less than 3 years of age (52%), and pregnant mares (51%). The respondents regarded the cyathostomin group as the most prevalent cause of parasitic disease and ill-thrift, followed by large strongyles and Parascaris equorum. Sixty seven percent rotated regularly between drugs, while 11% performed routine screening for anthelmintic resistance. Results of this survey suggest that limiting equine anthelmintics to prescription-only availability has increased the level of strongyle surveillance. Veterinary practitioners play a central role in equine parasite management with indications of a lowered intensity of treatment. However, screening for anthelmintic resistance remains uncommon.

Risk factors for faecal sand excretion in Icelandic horses

REASONS FOR PERFORMING STUDY

Sandy soil is often mentioned as a risk factor in the development of sand-related gastrointestinal disease (SGID) in the horse. There are other variables, but few studies confirm any of these.

OBJECTIVE

To investigate soil type, pasture quality, feeding practice in the paddock, age, sex and body condition score as risk factors for sand intake in the horse.

METHODS

Faeces were collected from 211 Icelandic horses on 19 different studs in Denmark together with soil samples and other potential risk factors. Sand content in faeces determined by a sand sedimentation test was interpreted as evidence of sand intake. Soil types were identified by soil analysis and significance of the data was tested using logistic analysis.

RESULTS

Of horses included in the study, 56.4% showed sand in the faeces and 5.7% had more than 5 mm sand as quantified by the rectal sleeve sedimentation test. Soil type had no significant effect when tested as main effect, but there was interaction between soil type and pasture quality. Significant interactions were also found between paddock feeding practice and pasture quality.

CONCLUSION

To evaluate the risk of sand intake it is important to consider 3 variables: soil type, pasture quality and feeding practice. Pasture quality was identified as a risk factor of both short and long grass in combination with sandy soil, while clay soil had the lowest risk in these combinations. Feeding practice in the paddock revealed feeding directly on the ground to be a risk factor when there was short (1-5 cm) or no grass. Also, no feeding outdoors increased the risk on pastures with short grass, while this had no effect in paddocks with no grass. More than 50% of all horses investigated in this study had sand in the faeces.

POTENTIAL RELEVANCE

The identification of risk factors is an important step towards prevention of SGID. Further research is necessary to determine why some horses exhibit more than 5 mm sand in the sedimentation test and whether this is correlated with geophagic behaviour.

Risk factors for high endoparasitic burden and the efficiency of a single anthelmintic treatment of Danish horses

A questionnaire survey regarding endoparasite control practices in Danish horse herds was carried out in 1995. The participating veterinarians and herd owners were sampled using convenience and purposive sampling. In the analysis of risk factors for development of a high endoparasitic burden (> 200 eggs per gram faeces) 903 horses were sampled and the analysis of the efficiency of a single anthelmintic treatment was based on 605 horses. The following factors had a significant effect on the endoparasitic burden: herd type, age of the horses, use of pasture rotation, anthelmintic treatment of horses visiting the herd, use of an adviser in the planning of endoparasite control and advice regarding pasture rotation. An interaction between pasture rotation and advice regarding pasture rotation was found, but due to high colinearity this was not reported. The factors influencing significantly on the reduction of the faecal egg count after a single anthelmintic treatment were the type of herd, the age of the horse, the drug used, and the anthelmintic-resistance-status of the herd. A negative effect of permanent pastures was observed. If pasture hygiene was performed on the advice of the veterinarian, the effect of a single anthelmintic treatment was less compared to a single anthelmintic treatment without any advice. An interaction between the treatment group and the resistance-status of the herd was found. Additional factors, normally accounted for, when endoparasites and anthelmintic resistance is discussed, were investigated, but not found significant in this study.

A questionnaire survey on nematode control practices on horse farms in Denmark and the existence of risk factors for the development of anthelmintic resistance

A questionnaire survey to obtain information on endoparasite control practices and management on 68 Danish horse farms was undertaken in 1995. The study revealed that foals, young horses and adults were on average, annually treated 4.3, 4.0 and 3.7 times, respectively. The most commonly used drug from 1993-1995 was ivermectin. On average 2.4 different drugs were used annually. The most used method of weight estimation was eye measure: for foals by 78%, for youngsters by 81% and adults by 82% of the herd owners. The most commonly used weight in the dosing of anthelmintics was individual weights of the horse: 72% of the herd owners dosed their foals this way. 76% their youngsters and 75% their adults. Sixty two percent of the herd owners treated at turn out, 47% at housing, 57% treated when buying new horses, 26% treated when stabling visiting horses, 78% applied pasture change and 18% performed alternate/mixed grazing. Sixty one percent of the herds had experienced problems with diarrhoea and in 18% of the cases the suspected cause was considered to be endoparasites. 33% of the farms performed disease registration and on 25% Faecal Egg Count Reduction tests had been performed before entering this study. The herd owners obtained their formation about endoparasite control from veterinarians, meetings and papers in that order of importance.

Ocular tuberculosis in a horse

This paper is the first report of systemic tuberculosis involving the eyes in a horse. The animal lost condition and gradually became increasingly blind in both eyes; it was eventually euthanased. The pathological findings included bilateral, mycobacterial granulomatous uveitis with unilateral retinal detachment and necrosis, and disseminated, mycobacterial granulomatous foci in the myocardium, lungs, bronchial lymph nodes, kidneys, liver, pancreas, colon and visceral serosal surfaces, with the most extensive lesions in the myocardium. The mycobacteria were identified as Mycobacterium avium.

Gastrointestinal aspergillosis and zygomycosis of cattle

Gastrointestinal mycosis was diagnosed in 73 lesions of 32 cattle without a history of engorgement, and tissues of 29 animals were examined histopathologically. The omasum was the target organ for infection, followed by the rumen and reticulum. Acute necrohemorrhagic lesions dominated, with infiltration of neutrophils and thrombosis. The etiologic diagnosis was accomplished by indirect immunohistochemical staining of fungal elements with a panel of mono- and polyclonal antibodies raised against fungal antigens. Aspergillosis and zygomycosis were diagnosed in one or more organs of 11 (34.4%) and 20 (62.5%) cattle, respectively, and dual infections were found in three lesions of two animals. Candidosis was diagnosed in only one case. Hematogenous spread of fungi predominantly to the liver was seen in nine animals. Lymphogenic spread of aspergilli to mesenteric and omasal lymph nodes occurred in one and two animals, respectively. Factors that seemed to predispose to mycotic infection included presence of other diseases and intense antimicrobial therapy. These factors and post-partum status, which included 23 of 29 (79.3%) cows, predisposed to mycosis in several ways, e.g., reflux of acidic abomasal contents into the forestomachs, stasis of proventricular content, metabolic dysfunctions, and stress.

Squamous cell carcinoma of the equine stomach: a report of five cases

Five horses with squamous cell carcinoma of the stomach are described. The clinical findings included anorexia, weight loss, abdominal distension, abnormal chewing and swallowing behaviour and abdominal masses palpable per rectum in four cases. Haematological studies revealed a normocytic anaemia in three horses, and neutrophilia and hypoalbuminaemia in two. Analysis of peritoneal fluid revealed abnormal effusions in all five horses and neoplastic cells were identified in three of them. The tumours originated in the cardia and metastases were present in all the horses. Three of them had many small nodules covering the entire peritoneum.