Effect of anthelmintics on the gut microbiome

 While anthelmintic treatments are invaluable for controlling parasitic worm infections, new research shows they can also have unintended consequences on the gut microbiota. 

Michel Boisseau and colleagues conducted a study to explore how helminths, particularly cyathostomins, interact with the gut microbiota in their host animals. 

 

The research team observed naturally infected ponies to track changes in this relationship over time, both before and after treating them with pyrantel. (Pyrantel targets adult cyathostomins without affecting larval stages in the gut wall.) 

 

They also looked at how the ponies' blood gene expression responded to the anthelmintic treatment. Their work is reported in iScience.

 

The study involved 40 naturally infected Welsh pony mares, divided into four groups based on their worm burden and whether they received pyrantel treatment. 

 

Among the high shedding ponies, the researchers identified 14 species of cyathostomins, the most abundant of which was Cylicocyclus nassatus. They found that ponies with high cyathostomin egg counts had a richer and more dynamic gut microbiota. The presence of butyrate-producing Clostridia seemed to play an important role in maintaining stability within the ecosystem, while also bolstering host tolerance towards cyathostomin infections. Genes involved in B-cell activation and IgA synthesis were upregulated in high shedding ponies.

 

The administration of anthelmintic treatment induced a dramatic shift in the gut environment and microbial community dynamics, with the population being less stable. These changes were still present 7 days after treatment, and to a lesser extent after 15days. Anthelmintic treatment only had a limited effect on the host blood gene expression.

 

The researchers conclude: “These observations highlight how anthelmintic treatments alter the triangular relationship of parasite, host, and gut microbiota and open new perspectives for adding nutritional intervention to current parasite management strategies.”

 

 

For more details, see:

 

Michel Boisseau, Sophie Dhorne-Pollet, David Bars-Cortina, Élise Courtot, Delphine Serreau, Gwenolah Annonay, Jérôme Lluch, Amandine Gesbert, Fabrice Reigner, Guillaume Sallé, Núria Mach,

Species interactions, stability, and resilience of the gut microbiota - Helminth assemblage in horses,

iScience, Vol 26, 2, (2023), 106044.

 

https://doi.org/10.1016/j.isci.2023.106044

 

Assessing the impact of blindfolding on equine handling

Blindfolding horses is thought to make them easier to handle in stressful situations. By covering their eyes, blindfolds can reduce distractions that might make them anxious, especially in new or tense environments. However, there has been limited research in this area so far.

A study conducted by Caleigh Copelin, Bryn Hayman, Renée Bergeron, and Katrina Merkies at the University of Guelph investigated this topic. Their research suggests that blindfolding might offer benefits when encountering visually intimidating stimuli, especially in situations where time constraints are not present.

 

However, in emergency situations, such as barn fire evacuations, blindfolding is likely to prolong lead time and exacerbate handling difficulties. This could impede successful rescue efforts and potentially jeopardize the safety of both humans and animals.

 

The study involved thirty-three riding school horses led through a course of obstacles, both blindfolded and unblindfolded. Parameters such as time taken, lead rope pressure, heart rate, and frequency of avoidant or resistant behaviour were recorded and compared between the two groups.

 

Overall, blindfolded horses required more time and exerted greater lead rope pressure when led from a stall compared to unblindfolded horses. They also exhibited higher frequencies of avoidant and refusal behaviours and experienced higher heart rate increases during the process. 

 

However, when navigating a visually frightening obstacle (a gate made of pool noodles that brushed their flanks), blindfolded horses needed less time, exerted less lead rope pressure, and displayed fewer avoidant or refusal behaviours, than they did when not blindfolded.

 

The researchers suggest that blindfolding may be beneficial in situations involving visually frightening stimuli and where time constraints are not a concern. Nevertheless, further research is necessary to evaluate more realistically the effectiveness of blindfolds in simulated emergency scenarios.

 

For more details, see:

 

Copelin, C, Hayman, B, Bergeron, R, Merkies, K,.

Compliance or confusion? The usefulness of blindfolding horses as a handling technique,

Applied Animal Behaviour Science, (2024)

Vol 271,106180,

 

https://doi.org/10.1016/j.applanim.2024.106180

Iron-related inflammatory markers in colic

 

Colic is a major concern for horse owners, with two main types: those treatable with medicine
and those needing surgery. Quickly identifying which cases need surgery is crucial. 

 

In the early stages of inflammation, the liver releases acute phase proteins (APPs) like haptoglobin, fibrinogen, and serum amyloid A. Recent studies propose that blood iron levels could also indicate inflammation severity in colic cases.

 

Paulo Canola and colleagues evaluated serum ferritin, transferrin and iron levels as acute phase inflammatory markers in horses admitted to the hospital with colic. 

 

Ferritin, which stores iron in a non-toxic form, helping to regulate iron levels in the body, is recognized as a positive inflammatory marker, increasing in the acute phase

 

Transferrin, a glycoprotein found in blood plasma that binds to iron and transports it throughout the body, decreases in acute inflammation.

 

The researchers analysed these markers alongside total protein, fibrinogen, ceruloplasmin, albumin, and haptoglobin levels in blood samples from 12 colic surgery cases and 10 healthy horses. They compared healthy horses with colic cases, small and large intestinal obstructions, and survival rates. The work is published in the Journal of Equine Veterinary Science.

 

They found higher transferrin and haptoglobin levels and lower serum iron in colic cases compared to healthy horses. Large intestinal obstruction cases had lower transferrin levels than small intestinal obstruction cases. Fibrinogen levels were higher in horses more likely to die from strangulating lesions.

 

The researchers suggest that the acute phase proteins examined in the study could be used to evaluate the acute inflammatory response in horses with colic requiring surgery. 

 

 

For more details, see: 

 

P.A. Canola, R.F. de Salles, E.R. Daneze, M.F.R. Sobreira, B.E. de Oliveira, M.L. Favero, M.L. Antonioli.

Iron-related markers of inflammation in horses with colic.

Journal of Equine Veterinary Science, (2024) vol 134, 105010,

https://doi.org/10.1016/j.jevs.2024.105010

When. to treat melanoma?

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 A recent report suggests that a more pro-active approach to melanomas in horses could bejustified.

Melanomas are common in horses. They are usually found underneath the dock of the tail, in the anal, perianal and genital regions, and on the lips, eyelids, and sometimes around the salivary glands. Typically, they present as rounded black nodules.

 

Grey horses are far more susceptible to melanoma than horses of any other coat colour, with up to 80% of grey horses developing a melanoma at some point in their lives.

 

Despite their prevalence, our understanding of various aspects of this disease remains incomplete.

 

Prevailing attitudes among some owners and veterinarians suggest a reluctance to intervene early, guided by the belief that these tumours progress slowly, and that surgical intervention may exacerbate the horse's condition. But is this approach justified? 

 

Researchers in Portugal conducted a study to evaluate the effect of delayed excision on the clinical, histological, and immunohistochemical characteristics of equine melanoma. Their findings are published in Animals.

 

For this retrospective investigation, the research team reviewed tissue samples and clinical records of horses whose melanoma tissues had been submitted between 2010 and 2023. An analysis was conducted on data from 34 horses, encompassing a total of 42 melanomas, of which 13 were benign and 29 were malignant. The primary objective was to explore the clinical and histological variances between tumours that underwent prompt excision versus those left untreated for an extended duration.

 

The study found significant correlations between delayed excision and adverse outcomes, shedding light on the potential repercussions of postponing surgical intervention in equine melanomas.

 

Tumours excised at later stages were significantly larger than those subjected to earlier intervention. Additionally, delayed excision correlated with a higher incidence of multiple tumours, particularly among horses harbouring melanomas for over six years.

 

But more importantly, the interval between excision and diagnosis demonstrated a pronounced link with tumour malignancy, Melanomas excised at later stages were five times more likely to exhibit malignant characteristics compared to those removed earlier. 

 

These findings highlight the impact of delayed excision on the progression and severity of equine melanomas.

 

The report’s authors conclude that early intervention not only facilitates easier tumour removal but also mitigates the risk of future complications. 

 

“With this work, we provide scientific and objective evidence that time significantly influences equine melanomas, contributing to an increase in their size, number, and malignancy. As such, this work clarifies the importance of early intervention in preventing future complications caused by these tumours. This data may help clinicians in advising horse owners.”

 

 

For more details, see: 

 

Pimenta J, Prada J, Pires I, Cotovio M. 

The Impact of Excision Interval on Equine Melanoma Progression: Time Matters? 

Animals. 2024; 14(8):1244.

https://doi.org/10.3390/ani14081244

Investigating cabergoline for treating equine Cushing’s disease

 Cabergoline shows promise as a treatment option for equine Cushing’s disease, according to a recent report.

Cushing’s disease or Pituitary Pars Intermedia Dysfunction (PPID) is a common condition in older horses, resulting from increased activity in the intermediate lobe of the pituitary gland. This excessive activity has been attributed to nerve damage impairing its regulation, with dopamine acting as the crucial neurotransmitter. When dopamine levels are deficient, the pituitary gland becomes overactive, leading to the release of various hormones, such as adrenocorticotropic hormone (ACTH).

 

Clinical manifestations associated with PPID are well-documented and include hypertrichosis, laminitis, polyuria, polydipsia, lethargy, muscle wastage, and delayed wound healing.

 

Dopaminergic agonists, medications that mimic the action of dopamine, function by stimulating dopamine receptors in the pituitary gland. This stimulation results in the inhibition of the release of certain hormones, including ACTH, thereby mitigating clinical signs such as abnormal hair coat, muscle wasting, and laminitis.

 

Pergolide, a dopamine agonist, stands as the primary treatment for managing PPID and is approved for oral administration in equines. However, some horses may exhibit resistance to daily oral dosing. Cabergoline, another dopamine agonist like pergolide, currently is not licenced for use in horses.

 

A recent retrospective study conducted by Tania Sundra of Avon Ridge Equine Veterinary Services in Brigadoon, WA, Australia, along with colleagues, explored the efficacy of intramuscular extended-release cabergoline (ERC) injection in treating PPID. Despite being unlicensed, this treatment modality is increasingly utilized off-label in clinical practice for managing PPID. The study examined clinical records of privately-owned horses with PPID that had undergone intramuscular cabergoline treatment at Avon Ridge Equine Clinic.

 

The study examined the short-term (5–8 days) and longer-term (12 months) clinical and endocrinological responses to two doses of cabergoline: a low dose (0.005mg/kg) extended-release cabergoline (LDERC) and a high dose (0.01mg/kg) extended-release cabergoline (HDERC).

 

Results showed that although both doses of ERC led to a decrease in median ACTH concentration, the levels remained above the seasonal reference range in about half of the treated horses. However, similar responses had been noted in previous studies involving pergolide treatment for PPID.

 

Owners reported clinical improvement in 78.3% and 100% of horses treated with LDERC and HDERC, respectively. 

Common side effects of dopamine agonists, such as decreased appetite, lethargy, gastrointestinal upset, and behavioural changes, were observed. Notably, partial, self-limiting inappetence was reported in 30.0% of LDERC cases and 60% of HDERC cases, with seven horses exhibiting lethargy.

 

In cases of partial anorexia, owners noted that horses preferred long-stem forage (hay or grass) over cereal-based feeds. The clinical and endocrinological responses observed were consistent with previous reports of oral pergolide treatment.

 

The authors suggest that weekly injection of ERC may serve as an effective alternative to pergolide. The 0.005 mg/kg dose appeared to be as effective as the 0.01 mg/kg dose but with a lower risk of inappetence.

 

While cabergoline shows promise as a treatment option for PPID in horses, further research is necessary to fully establish its efficacy, safety profile, and optimal usage protocols.

 

 

For more details, see: 

 

Sundra T, Kelty E, Rossi G and Rendle D (2024) 

Retrospective assessment of the use of extended-release cabergoline in the management of equine pituitary pars intermedia dysfunction. 

Front. Vet. Sci. 11:1332337. 

https://doi.org/10.3389/fvets.2024.1332337