Gastrointestinal parasites in Slovak horses

© Jozef Mikat | Dreamstime.com

Gastrointestinal parasitism remains a significant health concern in equine populations worldwide. Horses commonly host a wide range of intestinal helminths (parasitic worms), some of which can cause serious disease, reduced performance, and compromised welfare.

In recent years, growing resistance to anthelmintic (deworming) medications has become a major challenge for effective parasite control. This resistance has largely developed due to management practices such as frequent blanket deworming, incorrect dosing, and repeated use of the same drug classes. As a result, current parasite control strategies are shifting toward evidence-based approaches that rely on monitoring infection levels and targeting treatment appropriately.

Slovakia has a well-established horse breeding industry, with over 22,500 horses representing approximately 40 breeds.

To support improved management strategies, recent research conducted by Kuzmina and colleagues aimed to evaluate the distribution and prevalence of gastrointestinal helminths in horses in eastern Slovakia, while also examining management factors that may influence infection levels.

The study involved analysis of 392 faecal samples collected from horses across 24 farms, representing a range of ages, breeds, and management systems. Coprological diagnostic techniques were used to identify parasite eggs. The McMaster method, with a sensitivity of 50 eggs per gram (EPG), was employed to detect nematode infections, while a double-centrifugation sedimentation-flotation method was used to identify tapeworm (Anoplocephala spp.) eggs. Additional information regarding horse age, breed, stocking density, and parasite control practices was collected to allow assessment of risk factors associated with infection.

Results indicated that strongylid nematodes were the most prevalent parasites identified, with 65.6% of horses testing positive. Egg counts ranged widely from 50 to 2800 EPG, demonstrating substantial variation in parasite burdens between individual animals. Notably, approximately 29.8% of horses were responsible for 80% of the total strongylid egg output, supporting previous evidence that parasite burdens are typically unevenly distributed within equine populations. This finding reinforces the principle behind targeted selective treatment, where only horses with higher egg counts are treated to reduce drug resistance and maintain refugia (untreated parasite populations).

Parascaris spp., which primarily affect younger horses, were detected in 4.5% of samples. Tapeworm infections caused by Anoplocephala spp. were relatively uncommon, being detected in only 0.3% of horses, and no additional helminth species were identified. These results confirm that strongylids and Parascaris spp. remain the dominant equine gastrointestinal parasites in Slovakia.

Statistical analysis revealed that horse age and stocking density were significant predictors of strongylid infection levels. Younger horses and animals kept at higher stocking densities were more likely to exhibit higher parasite burdens. In contrast, infection with Parascaris spp. was influenced solely by horse age, with younger horses demonstrating greater susceptibility due to their developing immune systems.

Overall, this study provides valuable insight into the current epidemiology of equine gastrointestinal parasites in Slovakia. The findings highlight the importance of regular faecal egg count monitoring and demonstrate that parasite burdens vary significantly between individuals. Incorporating targeted selective treatment strategies, alongside improved pasture management and reduced stocking density, may help slow the progression of anthelmintic resistance.

 

For more details, see:

Tetiana A. Kuzmina, Alžbeta Königová, Ludmila Burcáková, Yaroslav Syrota, Michal Babják, Marián Várady,

Gastrointestinal parasite occurrence in Slovak horses and factors affecting Strongylidae and Parascaris spp. egg shedding,

Veterinary Parasitology: Regional Studies and Reports,(2025)  Vol 64, 101328,

ISSN 2405-9390,

https://doi.org/10.1016/j.vprsr.2025.101328

UConn study links poor coat condition to higher parasite loads

A student works with a horse in the UConn stables
(c) Jason Sheldon / UConn)

Poor coat condition in horses has long been associated with heavy parasite burdens. A new
study from the University of Connecticut provides fresh evidence supporting this link and introduces a new tool to help assess it.

Led by Associate Professor Jenifer Nadeau in UConn’s Department of Animal Science, researchers developed a skin and coat condition scoring system to evaluate horses alongside their parasite levels. The work, published in the Journal of Equine Veterinary Science, builds on ideas that suggest that outward appearance may reflect an animal’s parasite resistance.

In the study, UConn’s herd of Morgan and Thoroughbred horses was regularly evaluated by students as part of the university’s hands-on equine science program. Faecal egg counts were collected to measure strongyle parasite loads, while separate teams of students, blinded to those results, scored each horse’s skin and coat condition.

The findings showed a clear trend: horses with higher parasite loads were significantly less likely to have good hair lustre. Although factors such as breed, age, housing, and season also influenced coat condition, parasite burden remained a strong predictor. Thoroughbreds, for example, tended to score lower than Morgans across several skin and coat categories.

The new scoring system may provide horse owners, managers, and even animal control agencies with a practical tool to help identify horses struggling with parasite-related issues or neglect. It can complement existing faecal testing by offering a quick visual assessment that may signal when further investigation is needed.

Nadeau plans to continue investigating how parasite levels change throughout a horse’s life and how coat condition can be used as an additional indicator of health. The study reinforces a message well known to equine professionals: paying close attention to coat quality can provide valuable clues about what’s happening inside the horse.

For more details, see:

N. DeBel, J. Johnson, A. Simoneau, B. Sweeney, G. Stearns, M. Amalaradjou, E. Gibbs, T. Moore, J. Nadeau,

The effect of parasitic load on skin and hair coat condition in Morgan and Thoroughbred horses,

Journal of Equine Veterinary Science, (2025) Vol 148, 105546

 

https://doi.org/10.1016/j.jevs.2025.105546

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Study on Deworming Practices

 The University of Connecticut Equine Extension Program has announced a study to better understand how horse owners and equine professionals manage deworming. Through a brief 10-minute survey, the team aims to gather real-world insight into current parasite-control practices and the industry’s overall awareness of effective deworming strategies.

Participation is voluntary, and all responses will remain confidential and used solely for educational purposes. The survey asks for basic information about respondents’ horses and their deworming experiences. Once started, answers cannot be revisited, and participants may stop at any time.

Those interested in contributing to this research can complete the survey at: https://s.uconn.edu/deworming-survey

Systemic Immune-Inflammatory Index: A new non-invasive tool for predicting nematode infections in horses?

 Routine monitoring for gastrointestinal nematodes remains a cornerstone of equine health management.
Traditionally, diagnostic methods such as faecal egg counts (FEC) and faecal culture are used to assess infection status and guide treatment decisions. However, these approaches are not without limitations. FEC lacks sensitivity in detecting low-burden infections, may not reflect larval stages, and shows poor correlation between egg counts and actual worm burdens. Faecal cultures can help identify parasite species but are time-consuming and technically demanding. 

A recent study by Falmata Kyari and colleagues from the Departments of Veterinary Parasitology and Veterinary Medicine at the University of Maiduguri, Nigeria, explored whether a novel blood-based index could provide a more accurate, non-invasive, and cost-effective diagnostic option. Their work focused on the Systemic Immune-Inflammatory Index (SII), a parameter calculated from routine haematological values: platelet count, neutrophil count, and total white blood cell count.

 

The SII is a composite biomarker reflecting the balance between pro-inflammatory and anti-inflammatory immune responses. It is calculated as:

 

SII = (Platelet count × Neutrophil count) ÷ Total white blood cell count

 

In human medicine, SII has been widely studied as a prognostic marker for systemic inflammation, sepsis, cardiovascular disease, and cancer progression. Elevated values typically indicate heightened inflammatory activity and a poorer clinical outlook.

 

In horses, however, the application of SII as a diagnostic tool is still in its infancy. Kyari’s study represents one of the first attempts to apply this marker in equine parasitology.

 

The research team conducted a cross-sectional study involving 164 apparently healthy horses. All animals underwent clinical examination to confirm baseline health and were excluded if they had received recent anthelmintic treatment.

 

Blood and faecal samples were collected. Based on faecal egg counts and faecal culture, the horses were classified as Infected (n = 66) and Non-infected (n = 98).

 

The SII was then calculated for each horse using routine haematology. Receiver Operating Characteristic (ROC) curve analysis was applied to assess the diagnostic accuracy of SII in predicting nematode infection status.

 

Key Findings:

 

• Prevalence: Overall nematode prevalence was 40.2%. Interestingly, cyathostomin infections were detected in only 14 horses (7 single infections and 7 mixed), a figure much lower than typically reported in temperate regions. This discrepancy may reflect climatic influences, differences in parasite ecology, or management and deworming practices in Nigerian equine populations.
• Infection severity: Horses with mixed nematode infections carried the heaviest burdens, averaging 1,805 ± 293 eggs per gram (epg). Cyathostomum spp. infections were particularly striking, with mean egg counts of 2,264 ± 133 epg.
• SII values: Surprisingly, SII values were lower in infected horses (0.06) compared to non-infected horses (0.19), a reversal of the pattern seen in human inflammatory conditions. This suggests that equine immune regulation during nematode infection may differ fundamentally from human responses.
• Correlation with egg counts: There was a significant negative correlation between SII and epg (r = -0.6023; P < 0.0001).
• Diagnostic performance: The SII demonstrated exceptional predictive accuracy, with an area under the ROC curve (AUC) of 0.990. An SII cut-off value of ≤0.108 offered 98.5% sensitivity and 100% specificity, validated by a high Youden index of 0.985.

 

This study suggests that SII, derived from simple blood parameters already included in routine haematology panels, could serve as a powerful adjunct tool for diagnosing nematode infections in horses.

 

However, certain caveats remain. The study was region-specific, and prevalence data differ markedly from findings in Europe and North America, where cyathostomins are often the dominant nematodes. Furthermore, the inverse SII response compared to human data highlights the need for further research into equine-specific immune mechanisms.

 

The work of Kyari and colleagues supports the potential of the Systemic Immune-Inflammatory Index as a novel diagnostic tool for nematode infections in horses. If validated across different populations and climates, SII could help veterinarians identify infected animals more reliably, enabling targeted anthelmintic treatment and better parasite management strategies.

 

For more details, see: 

Kyari F, Pogu CJ, Mairiga IA, Adamu L. 

The use of systemic immune inflammatory index as a predictor for nematodes infections in horses. 

Parasite Epidemiol Control. (2025) 30:e00453. 

doi: 10.1016/j.parepi.2025.e00453 

UF researchers seeking Central Florida horses for arthritis pain study

(c) Virgonira Dreamstime.com

 Do you own a horse with osteoarthritis, especially in the fetlock joint? Researchers at the
University of Florida are inviting horse owners to take part in a new study that could lead to better ways of identifying and managing joint pain — both in horses and in humans.

This research effort is a collaboration between UF’s Institute of Food and Agricultural Sciences (UF/IFAS), the UF College of Veterinary Medicine, the UF College of Dentistry, and the UF Department of Biomedical Engineering. Their goal is to improve how veterinarians detect joint pain in horses before it becomes visibly severe — giving your horse a better shot at long-term joint health and comfort.

Osteoarthritis is a leading cause of lameness and discomfort in horses. Like humans, horses develop arthritis from repetitive stress on the joints — often due to performance activities like racing, jumping, or even frequent trail work. While joint pain in horses is common, it's often not diagnosed until the horse shows clear signs of discomfort. By that point, valuable joint function may already be lost.

Dr. Samantha Brooks, associate professor of equine physiology and genetics at UF/IFAS, says this new study uses a non-invasive screening process designed to catch signs of pain earlier and more objectively than traditional evaluations.

“We tend to treat symptomatically when horses show obvious clinical signs of pain, but if we can detect subtle joint pain sooner, we might be able to start pain treatments in time to better preserve joint function, and tailor that treatment for each horse,” Brooks said. “And our horses undergo a lot of the same joint diseases that we have. Any tools that we can build to better understand the discomfort caused by arthritis in horses gives us a better understanding of arthritis pain in people.”

Because horses can’t tell us when or where it hurts, the UF team is aiming to build a more accurate way to assess pain — something that could ultimately improve not only equine care but also the way doctors understand arthritis pain in humans.

For this field study, UF is recruiting horses already diagnosed with osteoarthritis — ideally in the fetlock joint — who live in Central Florida. Horses enrolled in the study will receive a free initial screening, which includes:

• A basic lameness exam (e.g., walk/trot in a straight line)

• Radiographs (X-rays) of the fetlocks

• A simple blood draw

After the initial evaluation, the research team will make follow-up visits a few times a year over a two-year period. These visits are designed to observe the horses in their usual environment — there’s no change expected in your horse’s routine. Researchers will track movement patterns and behaviors using new, non-invasive technologies to better understand the signs of discomfort.

Kaylee Young, research coordinator in UF’s Animal Sciences department, emphasized how important horse owners are to this work.

“Participating in this study could lead to better pain management and care for not only our horse companions but for people,” she said. “This research could be something that could be life changing not only for horses but for humans.”

Interested in participating?
If your horse meets the criteria and you’d like to be part of this important study, email uf-gallop@ufl.edu with the subject line “Study Participation.” Be sure to include your location and a few details about your horse’s health, including whether they’ve been diagnosed with fetlock osteoarthritis.

New tool to aid worm control

  

A free online tool to help horse owners evaluate the risk of worm infection has been launched. 

 

This simple, user-friendly resource, titled ‘What’s Your Worm Risk?’, has been developed by Austin Davis Biologics in collaboration with equine industry.

 

Anthelmintic resistance poses a significant threat to equine health and welfare, with cases now reported in all common horse worms. Effective worm control begins with assessing a horse’s risk of infection, providing essential information for decisions regarding management, testing, and treatment.

 

The tool uses widely accepted principles of equine worm control to classify each horse's risk of infection as low, moderate, or high, based on details provided by the owner. It also accounts for the potential impact of grazing companions, where applicable.

 

Jacqui Matthews, a specialist in parasitology and director of veterinary science at Austin Davis Biologics, explains: “The tool is designed to support horse owners in assessing their horse’s risk of infection, helping them make informed decisions about testing and treatment.”

 

To reduce the risk of wormer resistance, experts recommend combining excellent pasture management—reducing worm transmission from paddocks—with regular testing to guide treatment decisions.

• Faecal worm egg count (FEC) tests provide an insight into worm egg shedding levels in manure.
• Antibody tests reveal the horse’s exposure to worm infections.

 

This approach minimizes the need for blanket wormer treatments, which are known to promote resistance and reduce the effectiveness of essential drugs.

 

The ‘What’s Your Worm Risk?’ tool has been optimised for use on smartphones, laptops, and desktop computers and is tailored specifically to UK conditions.

 

By integrating testing and evidence-based treatments into worm control plans, horse owners can protect their animals while reducing the risk of drug resistance in the equine population.

 

For more details, see: 

 

https://www.whatsyourwormrisk.com

New reporting initiative for clinical redworm disease in the UK

 Equine Infectious Disease Surveillance (EIDS) has launched RedWatch, a new initiative designed for vets to report cases of redworm disease in horses.

 

Based at Cambridge University, EIDS collects and analyses national disease data from diagnostic laboratories and veterinary practices across the UK. Their work provides valuable insights into the prevalence of equine infectious diseases. In addition to operating various surveillance programs, EIDS offers disease control advice and shares critical disease information through platforms like the International Collating Centre (ICC), EquiFluNet, and the Equine Quarterly Disease Surveillance Report, a collaborative effort with BEVA, Defra, and APHA.

 

Historically, large redworm infections—most notably caused by Strongylus vulgaris—have been significantly reduced in the UK due to the widespread use of anthelmintics. However, the overuse of these treatments has led to growing resistance, especially in small redworms (cyathostomes). As a result, there has been a shift towards reducing anthelmintic use and focusing on management-based strategies to control parasitic diseases.

 

Concerns remain, however, that reduced anthelmintic use could unintentionally alter the patterns of parasite-associated diseases. To address this, EIDS has introduced RedWatch, a targeted surveillance initiative.

 

RedWatch will collect and disseminate case data on diseases caused by small and large strongyles, including cyathostominosis and Strongylus vulgaris. Veterinary surgeons are encouraged to submit information via an online form, recording:

·       Vet and practice details

·       Case-specific information

·       Diagnostic methods

·       Clinical signs observed

·       Data about the premises and equine population

·       Potential risk factors

All submitted data will be securely stored and anonymised for public reporting. This will support education, awareness, and ongoing research into equine parasitology.

 

Large strongyles are often only detected during post-mortem examinations (PME) and are likely to be captured mainly through the Equine Quarterly Disease Surveillance report’s post-mortem surveillance section.  However, RedWatch will allow veterinary surgeons to report large strongyle cases that have not undergone an official PME.

 

"RedWatch is an exciting step in equine parasitology surveillance," said Fleur Whitlock, veterinary surgeon and epidemiologist at EIDS. "This initiative relies on veterinary surgeons sharing data and their engagement is key to filling knowledge gaps. By contributing case reports, vets can directly support efforts to prevent these devastating diseases and help pave the way for new tools like real-time reporting and risk warnings.”

 

EIDS is generously funded by the UK’s Thoroughbred industry and is based at Cambridge University.

 

For more details, download the latest Equine Quarterly Disease Surveillance report

https://equinesurveillance.org/landing/resources/reports/dsr20243.pdf

 

Veterinary surgeons can record cases at

www.equinesurveillance.org/redwatch

Effect of PPID on egg shedding after deworming

It has been suggested that horses with hormonal disorders, such as insulin dysregulation and
Pituitary Pars Intermedia Dysfunction (PPID), may be more susceptible to worm infections. 

Horses with PPID often have a weakened immune system, which can allow worms, such as cyathostomes, to thrive more easily compared to healthy horses. These horses may also not respond as effectively to standard deworming treatments due to their altered immune function.

 

A study conducted in Australia aimed to determine whether horses with PPID had increased strongyle faecal egg counts (FEC) compared with control horses.

 

The study, led by Adelaina Horner, took place over a fourteen-week period and involved adult horses and ponies over eight years old in Victoria, Australia. All horses lived on pasture and had not been dewormed for at least three months prior to the study. A total of 45 privately owned horses and ponies met the criteria for inclusion, with 14 horses diagnosed with PPID and 31 serving as controls. PPID diagnosis was confirmed by elevated plasma ACTH concentrations (above 120 pg/mL) along with at least one clinical sign of the disorder.

 

All horses were dewormed with a standard dose of a commercially available ivermectin product. Faecal egg counts were taken before treatment and then every two weeks for 14 weeks. A FEC of 200 eggs per gram (EPG) or higher was used as the cutoff for significant worm burden.

 

The results showed that the egg reappearance period (ERP) after deworming was shorter in PPID horses, and cumulative FEC after deworming was higher in these horses. However, the researchers noted that some PPID horses consistently had no detectable eggs or low EPG (≤ 200) throughout the study, and this could not be explained by observed husbandry practices.

 

Worm eggs collected during the study were cultured in the laboratory, and examination of the larvae confirmed that all worms were cyathostomin species.

 

The researchers advise monitoring egg shedding before anthelmintic treatment in PPID horses, in line with sustainable worm management guidelines, as some PPID horses consistently showed low FEC results.

 

While hormonal disorders like PPID do not directly cause an increase in parasitic infections, they can impair the horse’s immune system and overall health, making them more vulnerable to worm infections and potentially reducing the effectiveness of treatments. Effective management of both the hormonal disorder and parasitic infections is crucial for maintaining the health of affected horses.

 

 

For more details, see: 

 

Strongyle egg shedding and egg reappearance periods in horses with pituitary pars intermedia dysfunction

Adelaina Horner, Nicholas J. Bamford, Michael J. Stear, David Piedrafita, Abdul Jabbar, Kristopher J. Hughes, Charles M. El-Hage, Sarah Preston

Veterinary Parasitology (2024) Vol 328, 110176

 

https://doi.org/10.1016/j.vetpar.2024.110176

New internal parasite guidelines from AAEP

The American Association of Equine Practitioners (AAEP) has issued revised Internal Parasite Control Guidelines to help minimise the risk of parasitic disease and maintain the effectiveness of current drugs for as long as possible by delaying further development of anthelmintic resistance.

The guidelines, originally created in 2013 and last revised in 2019, account for recent advances in knowledge concerning increased anthelmintic resistance and optimisation of parasite control management practices. They also address common misconceptions and offer parasite control program recommendations for senior horses (over 15 years old), mature horses (between 5 and 15 years old), and young horses (under 5 years old).

The guidelines were reviewed and updated by the AAEP Internal Parasite Control Guidelines Task Force, chaired by Dr. Nielsen and comprised of 10 AAEP members predominantly board certified in veterinary internal medicine, veterinary parasitology and/or veterinary microbiology. 

“We have seen dramatic development in the field of equine parasite control over the past 10 years, since we first launched these guidelines, and we work hard to keep our recommendations up to date,” said Martin Nielsen, DVM, PhD, DVSc, DAVCM, DEVPC, Schlaikjer Professor of Equine Infectious Diseases at the University of Kentucky.

Important conclusions to be drawn from the revised guidelines are to:

• Perform fecal egg count reduction tests annually to ensure that you are using effective dewormers in every herd or barn.
• Recognize that no anthelmintic will eliminate all parasitic stages from a horse.
• Continue using fecal egg counts once or twice per year to stratify horses into low, medium and high shedders to reduce pasture contamination.
• Deworm all horses at a baseline rate and target selected horses more often based on fecal egg counts.
• Not use fecal egg counts to diagnose disease in horses as there is no correlation between fecal egg counts and disease-causing parasite life stages.
• Discontinue deworming all horses with fixed intervals year-round and stop blindly rotating anthelmintic classes.

View the guidelines at https://aaep.org/resource/internal-parasite-control-guidelines.

You can access the entire guidelines document by clicking the Download Resource button.

Effect of diet on strongyle infection and gut microbiome

Recent research from France suggests that the first step in controlling intestinal worm infections inanimals should be providing them with diets that maintain a healthy gut ecosystem. 

Horses’ intestines can harbour many different worms, some of which can cause severe disease. It's concerning that some of these worms are becoming resistant to deworming medications. This resistance has emerged through factors such as incorrect dosing or frequent use of the same medications.

 

It's clear that we need to adopt a more sustainable approach to managing equine  intestinal parasites.

 

To address this challenge, scientists are exploring different methods, including dietary changes. These diets might enhance the body's defences, regulate gut bacteria, or directly combat parasites. For example, certain foods containing plant compounds might hinder worm reproduction in the body.

 

A study by Noémie Laroche and colleagues, at Lab to Field, Dijon, and the University of Bourgogne Franche-Comté, investigated how diet affects strongyle infection in horses, focusing on immune-mediated, microbiota-mediated, or direct deworming mechanisms. The work is reported in PLos ONE.

 

They studied twelve adult French Trotter geldings naturally infected with strongyles. These horses were divided into two groups and fed either a high-fibre or high-starch diet, along with supplements containing polyphenol-rich pellets from dehydrated sainfoin or control pellets made from sunflower and hay.

 

The study revealed that horses on a high-starch diet had higher strongyle egg excretion compared to those on a high-fibre diet. However, adding sainfoin to the high-starch diet reduced egg excretion. What’s more, sainfoin supplementation decreased larval motility, regardless of the diet.

 

Moreover, the high-starch diet was associated with lower faecal bacterial diversity, changes in faecal microbiota structure, lower faecal pH, reduced blood acetate levels, and lower haematocrit compared to the high-fibre diet.

 

Overall, these findings suggest that dietary changes can be an alternative strategy for managing helminth infections. 

 

The study highlights the importance of considering broader ecological mechanisms in parasite management strategies. The researchers emphasize that eradicating helminth infections entirely is unrealistic and could have negative effects. 

 

They write: “… pursuing a goal of eradicating helminth infection (zero infection) is not only illusionary but also likely to produce more negative effects than benefits. Mammals have coevolved with helminths during millions of years, and in most cases, the infection does not produce severe symptoms.’

 

“We therefore suggest that a safer strategy to control helminth infection would be to improve host tolerance to the infection rather than pursuing a hopeless, environmentally toxic, strategy of drug-based eradication.”

 

For more details, see:

 

Laroche N, Grimm P, Julliand S, Sorci G (2024) 

Diet modulates strongyle infection and microbiota in the large intestine of horses. PLoS ONE 19(4): e0301920. 

https://doi.org/10.1371/journal.pone.0301920

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

 

Revealing the silent reservoir: Horses and the potential threat of Leishmaniosis

 Leishmaniasis, a zoonotic disease capable of transmission from animals to humans, has long
been acknowledged as a significant public health concern. The World Health Organisation reports that over one billion people reside in areas endemic to leishmaniasis, placing them at risk of infection. The disease manifests in three distinct syndromes in humans: cutaneous, mucocutaneous, and visceral. Annually, there are approximately 30,000 new cases of visceral leishmaniasis and over one million new cases of the cutaneous form. Remarkably, leishmaniasis ranks as the second leading parasitic cause of death worldwide, following malaria.

The causative agent of leishmaniasis is an intracellular protozoan parasite known as Leishmania spp., transmitted through sandflies. Traditionally, dogs have been identified as the primary reservoir, but recent research suggests the involvement of other species in the transmission cycle. 

 

Infected horses may exhibit signs of cutaneous leishmaniasis, manifesting as nodules on various body parts such as the head, ear, scrotum, legs, and neck. These lesions, which can be singular or multiple, often present with ulceration. However, some horses may carry the infection without displaying any visible signs, potentially serving as silent reservoir hosts

 

As our understanding of the dynamics of leishmaniasis transmission expands, it becomes increasingly important to consider a variety of animal species, including horses, in efforts to mitigate the impact of this disease on both animal and human populations.

 

Researchers from the Veterinary Faculty at Universidad Cardenal Herrera-CEU Valencia, Spain, conducted a study aimed at elucidating the potential role horses may play in the transmission of leishmaniosis, a parasitic disease. Lola Martínez-Sáez and her colleagues undertook an analysis of the prevalence and factors associated with L. infantum infection in seemingly healthy horses. A full report of the work is published in the online journal Animals.

 

The team gathered epidemiological data and serum samples from 167 apparently healthy horses in the Valencia region of eastern Spain. They used an enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (PCR) to assess the presence of L. infantum during two distinct periods: December 2022 to January 2023 and May 2023 to June 2023.

 

The results revealed that 27.5% of apparently healthy horses tested positive for anti-leishmania antibodies, and infection was confirmed through real-time PCR. Interestingly, horses with a calm temperament and those residing outdoors exhibited a higher prevalence of infection.

 

Additionally, the study unveiled a seasonal variation in equine Leishmania spp. infections, with a notable spike during the spring months, aligning with higher average temperatures. This observation underscores the significant influence of climate on the prevalence of leishmaniosis, raising concerns about the potential impact of climate change on the disease's future trajectory.

 

From a One Health perspective, the researchers emphasize the need for a holistic approach to combat leishmaniosis. Given the close contact between horses and humans, horses may act as silent reservoirs, facilitating parasite transmission. As a result, the study advocates for the incorporation of preventive measures for horses, such as regular use of repellents, to control the spread of leishmaniosis across species.

 

For more details, see:

 

Prevalence and Factors Related to Leishmania infantum Infection in Healthy Horses (Equus caballus) from Eastern Spain. 

Martínez-Sáez L, Dulac Q, Montaner-Angoiti E, Marín-García PJ, Llobat L. 

Animals. 2023; 13(18):2889. 

https://doi.org/10.3390/ani13182889

Careful use of anthelminitcs can help limit resistance

 Recent research suggests that employing selective treatment regimens can significantly reduce the
development of anthelmintic resistance. This is particularly relevant in the context of parasites such as the cyathostomins (small redworms), which are among the most common internal parasites of horses. These parasites have developed resistance to various deworming drugs over the years due to their widespread and indiscriminate use.

In Sweden, a country known for its controlled approach to anthelmintic use, a study was conducted to investigate the presence of resistance to ivermectin, a commonly used deworming medication. The research found no evidence of resistance to ivermectin in cyathostomes in Sweden.

 

ML resistance has been observed in cyathostomins worldwide. However, the current situation in Sweden is unclear. Routine anthelmintic treatment of horses without prior diagnostic tests is rare in Sweden, since anthelmintic drugs were restricted to being available on prescription only in 2007. What effect would this have had on the development of ML resistance in the country?

 

To assess the effectiveness of deworming treatments, two common tests are used: the faecal egg count reduction test (FECRT) and the egg reappearance period (ERP) after treatment. FECRT evaluates whether a dewormer successfully reduces the number of internal parasite eggs in the horse's faeces. Samples are taken before treatment and around 10 to 14 days after deworming, and the two egg counts are compared. A high reduction percentage indicates that the dewormer is effective, while a low reduction percentage suggests potential resistance.

 

As internal parasites develop resistance to dewormers, the egg reappearance period (ERP) shortens, meaning that eggs reappear in the faeces more quickly after treatment.

 

A study led by Ylva Hedberg Alm and her colleagues aimed to assess FECRTs and ERPs following ivermectin (IVM) treatment in Swedish horses. Sixteen equestrian establishments, each with at least six horses excreting a minimum of 150 eggs per gram of faeces (EPG) during screening, were included in the study. FECRTs and ERPs were evaluated in faecal samples before and after IVM treatment (200 µg/kg) and for eight weeks afterward.

 

The questionnaire responses revealed that 69% of establishments administered anthelmintic treatments based on faecal diagnostics. All establishments achieved a high FECRT, exceeding 99.0%, and ERPs ranged from six to over eight weeks. Notably, younger horses were found to excrete cyathostomin eggs earlier after treatment than older horses.

 

The researchers also observed that riding schools, stud farms, and those not segregating summer and winter paddocks had shorter egg reappearance periods.

 

In conclusion, this study in Swedish equestrian facilities employing selective anthelmintic treatment revealed that the establishments maintained longer ERPs and showed no confirmed resistance to ivermectin. These findings support the use of selective deworming strategies as a means of reducing the risk of anthelmintic resistance in horses. The full report is available in Veterinary Parasitology.

 

For more details, see:

 

Retained efficacy of ivermectin against cyathostomins in Swedish horse establishments practicing selective anthelmintic treatment

Ylva Hedberg Alm, Eva Osterman Lind, Frida Martin, Rebecca Lindfors, Nina Roepstorff, Ulf Hedenström, Isabelle Fredriksson, Peter Halvarsson, Eva Tydén

Veterinary Parasitology (2023) Vol 322, 110007

 

https://doi.org/10.1016/j.vetpar.2023.110007