Anthelmintic drugs used in equine species

Repositioning anthelmintics for the treatment of inflammatory-based pathological conditions

Acute, uncontrolled and/or long-lasting inflammation causes a breakdown in immunological tolerance, leading to chronicity and contributing to a series of significant local or systemic tissue changes. Anti-inflammatory efficacy, fewer adverse effects, improved selectivity, and curative action are imminent issues for patients suffering from chronic inflammation-related pathologies. Then, we performed a complete and critical review about anthelmintics, discussing the main classes and the available preclinical evidence on repurposing to treat inflammation-based conditions. Despite low bioavailability, many benzimidazoles (albendazole and mebendazole), salicylanilides (niclosamide), macrocyclic lactones (avermectins), pyrazinoisoquinolones (praziquantel), thiazolides (nitazoxanide), piperazine derivatives, and imidazothiazoles (levamisole) indicate that repositioning is a promising strategy. They may represent a lower cost and time-saving course to expand anti-inflammatory options. Although mechanisms of action are not fully elucidated and well-delineated, in general, anthelmintics disrupt mitogen-activated protein kinases, the synthesis of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8, IL-12, and IFN-γ), the migration and infiltration of leukocytes, and decrease COX-2 expression, which impacts negatively on the release of prostanoids and leukotrienes. Moreover, some of them reduce nuclear accumulation of NF-κB (niclosamide, albendazole, and ivermectin), levels of nitric oxide (nitazoxanide and albendazole), and mucus, cytokines, and bronchoconstriction in experimental inflammatory pulmonary diseases (ivermectin and niclosamide). Considering the linking between cytokines, bradykinin, histamine, and nociceptors with algesia, anthelmintics also stand out for treating inflammatory pain disorders (ivermectin, niclosamide, nitazoxanide, mebendazole, levamisole), including for cancer-related pain status. There are obstacles, including the low bioavailability and the first-pass metabolism.

Chemical contaminants in donkey milk: A review of literature on sources, routes and pathways of contamination, regulatory framework, health risks, and preventive measures

Donkey milk has garnered increasing attention due to its potential health benefits and nutritional properties, positioning it as a valuable alternative to cow's milk for specific consumer groups, such as individuals with allergies, young children, elderly populations, and those with compromised immune systems. However, the presence of chemical contaminants in donkey milk presents a significant concern for food safety and public health. This review aims to provide an assessment of the types and sources of chemical contaminants in donkey milk, including heavy metals, mycotoxins, pesticides, polychlorinated biphenyls, and antimicrobial and antiparasitic veterinary drugs. Through a comprehensive analysis of available literature, we examine the routes and pathways through which these contaminants enter the milk, their prevalence, and the associated health risks. The review also briefly discusses analytical methods for detecting these contaminants and the existing legislative framework that regulates these contaminants, underscoring its critical role in safeguarding public health and promoting safe consumption of donkey milk products. By identifying gaps in existing research and suggesting areas for further study, this review seeks to contribute to the development of more effective strategies for monitoring and mitigating chemical contamination in donkey milk, ultimately safeguarding consumer health and supporting the sustainable production of this niche dairy product.

Assessment of worm control practices recommended by equine veterinarians in Australia

This study aimed to assess Australian veterinarians' knowledge, perceptions and treatment strategies for worm control in horses with an online questionnaire. The questionnaire comprised 64 questions covering various aspects of: (i) veterinary practice; (ii) the veterinarian's knowledge of gastrointestinal nematodes (GINs) and the importance of parasites in different age groups of horses; (iii) the diagnosis and control of worms; (iv) anthelmintics and anthelmintic resistance (AR); (v) grazing management; and (vi) the means of communication and the discussion between veterinarians and their clients regarding worm control. Following a pilot survey, a link for the questionnaire survey was sent to all (n = 1,148) registered members of Equine Veterinarians Australia in April 2020. The response rate for the questionnaire was 10% (118 of 1,148). The findings of this study illustrate veterinarians' good understanding of aspects of equine parasites, including control. However, respondents mainly recommended frequent, interval-based prophylactic deworming in young horses, and only 40% (96 of 239) diagnosed GIN infections based on faecal egg count (FEC) results in all age groups of horses. Furthermore, only 27% (88 of 330) of the respondents made deworming decisions based on FECs. Most of the respondents recommended macrocyclic lactones (MLs) for all age groups of horses (71%, 481 of 677), and the most frequently used method to calculate the dose of anthelmintics was by estimating the weight of animals visually (53%, 63 of 118). Although the majority of respondents (97%, 115 of 118) perceived AR to be a critical issue in managing worms in horses, 58% (67 of 118) of them were unaware of the status of AR on their clients' properties. Forty-two percent (50 of 118) of the respondents perceived the presence of AR in worms, including pinworms (16%), strongylins (15%), species of Draschia and Habronema (6%), Strongyloides westeri (2%) and tapeworms (1%). Twenty-seven percent (32 of 118) of the respondents rarely discussed equine worm control practices with their clients. This study provides insights into the perception and worm control practices recommended by Australian veterinarians to manage equine parasites. The findings highlight the importance of continued education and awareness of AR, and the use of non-chemical methods as well as consideration of the legislation of prescription-only use of anthelmintics based on FECs to achieve sustainable control of GINs in Australian horses.

Horse and donkey parasitology: differences and analogies for a correct diagnostic and management of major helminth infections

In June 2022, at the XXXII Conference of the Italian Society of Parasitology, the parallels of the main endoparasitic infections of horses and donkeys were discussed. Although these 2 species are genetically different, they can be challenged by a similar range of parasites (i.e. small and large strongyles, and Parascaris spp.). Although equids can demonstrate some level of resilience to parasites, they have quite distinct helminth biodiversity, distribution and intensity among different geographical locations and breeds. Heavily infected donkeys may show fewer clinical signs than horses. Although parasite control is primarily provided to horses, we consider that there may be a risk of drug-resistance parasitic infection through passive infection in donkeys when sharing the same pasture areas. Knowing the possible lack of drug efficacy (<90 or 80%), it is advocated the use of selective treatment for both species based on fecal egg counts. Adult horses should receive treatment when the threshold exceeds 200–500 eggs per gram (EPG) of small strongyles. Moreover, considering that there are no precise indications in donkeys, a value >300 EPG may be a safe recommendation. We have highlighted the main points of the discussion including the dynamics of helminth infections between the 2 species.

Detection of SNPs and benzimidazole resistance in strongyle nematode eggs of horses by allele-specific PCR

This study was conducted to determine single nucleotide polymorphisms (SNPs) and the benzimidazole (BZ) resistance in strongyle nematode egg populations in horses using molecular techniques. A total of 200 fecal samples were collected from horses in 26 farms in two provinces (Kayseri and Nevşehir) of the Central Anatolia Region of Türkiye between May and August 2022. The flotation method was used to detect strongyle nematode eggs in the fecal samples of the horses. Afterward, strongyle nematode eggs were collected, and the allele-specific polymerase chain reaction (AS-PCR) technique was used to detect the BZ resistance. BZ-susceptible and BZ-resistant PCR products were sequenced to determine single nucleotide polymorphisms (SNPs) in the β-tubulin isotype 1 gene. The strongyle nematode eggs were determined in 85 (42.5%) out of 200 fecal samples. AS-PCR detected 50.58% (43/85) BZ-resistant (homozygous resistant) and 36.4% (31/85) BZ-susceptible (homozygous susceptible) genes in the strongyle eggs. Both BZ-resistant and BZ-susceptible genes (heterozygous) were determined in 11 samples. BZ-resistant and BZ-susceptible allele frequencies were determined as 57.0% (48.5/85) and 43.0% (36.5/85), respectively. SNPs were detected only in codon 200 of the β-tubulin isotype 1 gene in four sequenced isolates of the two resistant and two susceptible isolates. This study is the first molecular report on BZ resistance in strongyle nematode eggs in horses in Türkiye. The widespread prevalence of BZ-resistant alleles in equine strongyle nematodes shows the requirement for the immediate usage of other anthelmintics instead of the BZ group drugs for the effective management and control of equine strongyle nematodes.

Prevalence of intestinal nematodes in equines with an assessment of the therapy using Albendazole and Doramectin.. [DOI: 10.21203/rs.3.rs-2889716/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: Intestinal nematode parasites of equines have emerged as a pressing and urgent challenge due to their significant impact on the health and performance of these animals worldwide; therefore, implementing a deworming regimen has become vital to keeping a horse's parasite load at an acceptable level. Thus, the current study aimed to estimate the prevalence of nematodes infection , associated risk factors and evaluate the chemotherapeutic efficacy of different anthelmintic drugs by enrolling 195 fecal matter samples of working equines using flotation concentration techniques. Equines treatment were divided into four groups; Group 1 standard treatment (Albendazole orally), Group 2 intervention treatment (Doramectin injection), Group 3 intervention treatment (combination of Albendazole and Doramectin), and Group 4 was left untreated as a positive control. Results: The overall prevalence of intestinal nematode parasites in working equines was 70.25%. The recovered nematodes were Strongylus species, with 87.17% followed by Parascaris equorum 30.76%, and Oxyuris equi was 12.82%. Concerning treatment efficacy, the highest cure rate was among Group 3 (77.14%), followed by Group 2 (68.57%) and Group 1 (40%), but the difference between Groups 2 and 3 is statistically insignificant. Interestingly, the effect of Doramectin injection is highly significant than other, especially for the reduction of Strongylus spp. and Parascaris equorum eggs according to Cohen's D test. Conclusions: Translating such a potent combination of drugs into endemic areas will provide significant support for deworming and control programs against intestinal parasites of equines, especially those in the migratory phase, more than Albendazole alone, which has poor absorption as it requires a full stomach during administration.

Moringa oleifera as a Natural Alternative for the Control of Gastrointestinal Parasites in Equines: A Review

Studies have shown a wide variety of parasites that infect horses, causing major gastrointestinal damage that can lead to death, and although the main method of control has been synthetic anthelmintics, there are parasites that have developed resistance to these drugs. For generations, plants have been used throughout the world as a cure or treatment for countless diseases and their symptoms, as is the case of Moringa oleifera, a plant native to the western region. In all its organs, mainly in leaves, M. oleifera presents a diversity of bioactive compounds, including flavonoids, tannins, phenolic acids, saponins, and vitamins, which provide antioxidant power to the plant. The compounds with the greatest antiparasitic activity are tannins and saponins, and they affect both the larvae and the oocytes of various equine gastrointestinal parasites. Therefore, M. oleifera is a promising source for the natural control of gastrointestinal parasites in horses.

Improving meat qualities of pigs after deworming against ascariasis with administered glycyrrhizic acid

The present paper describes the effect of glycyrrhizic acid contained in licorice roots on the quality of pork produced. The study uses advanced research methods as ion-exchange chromatography, inductively coupled plasma mass spectrometry, drying of an average sample of muscle, and pressing method. The paper set out to investigate the effect of glycyrrhizic acid on the pig meat quality after deworming. Of particular concern is the animal body restoration after deworming that results in metabolic disorders. The nutrient content of meat reduces, the output of bones and tendons rises. This is the first report on the use of glycyrrhizic acid to increase the meat quality of pigs after deworming. The findings from this study indicated higher pork quality resulted from a favorable effect of GA on the chemical and amino acid composition of meat. The resulting data demonstrated that glycyrrhizic acid in the piglets' diet had a beneficial effect on the biochemical processes in their body. The main scientific provisions of this paper and its findings have several practical implications for veterinary specialists. They can also be recommended for the educational process. Another possible implication is the development of new drugs, methods, and treatment plans.

Application of Mesoporous Silica Nanoparticles in Cancer Therapy and Delivery of Repurposed Anthelmintics for Cancer Therapy

This review focuses on the biomedical application of mesoporous silica nanoparticles (MSNs), mainly focusing on the therapeutic application of MSNs for cancer treatment and specifically on overcoming the challenges of currently available anthelmintics (e.g., low water solubility) as repurposed drugs for cancer treatment. MSNs, due to their promising features, such as tunable pore size and volume, ability to control the drug release, and ability to convert the crystalline state of drugs to an amorphous state, are appropriate carriers for drug delivery with the improved solubility of hydrophobic drugs. The biomedical applications of MSNs can be further improved by the development of MSN-based multimodal anticancer therapeutics (e.g., photosensitizer-, photothermal-, and chemotherapeutics-modified MSNs) and chemical modifications, such as poly ethyleneglycol (PEG)ylation. In this review, various applications of MSNs (photodynamic and sonodynamic therapies, chemotherapy, radiation therapy, gene therapy, immunotherapy) and, in particular, as the carrier of anthelmintics for cancer therapy have been discussed. Additionally, the issues related to the safety of these nanoparticles have been deeply discussed. According to the findings of this literature review, the applications of MSN nanosystems for cancer therapy are a promising approach to improving the efficacy of the diagnostic and chemotherapeutic agents. Moreover, the MSN systems seem to be an efficient strategy to further help to decrease treatment costs by reducing the drug dose.

Occurrence of Strongylid Nematode Parasites on Horse Farms in Berlin and Brandenburg, Germany, With High Seroprevalence of Strongylus vulgaris Infection

The infection of horses with strongylid nematodes is highly prevalent, with multi-species infections being the rule. Strongylus spp. and in particular Strongylus vulgaris are amongst the most pathogenic strongyle equine parasites. Presumably due to regular strategic anthelmintic treatments in combination with long prepatencies, prevalence of these worms was severely reduced in past decades. In this study, 484 horses from 48 farms in Berlin/Brandenburg, Germany were sampled between May 2017 and January 2018. Mini-FLOTAC and combined sedimentation/flotation were used to analyse faecal samples and larval cultures were carried out from individual strongyle infected horses for molecular testing for Strongylus spp. infection. Additionally, for Strongylus vulgaris, antibodies against a recombinant larval antigen were quantified in an ELISA. Strongyle type eggs were detected in 66.7% of the individual faecal samples. Nematode DNA was amplifiable from 311 samples and S. vulgaris and Strongylus edentatus were detected in four (1.3%) and 10 (6.3%) of these, respectively, the latter using a novel high-resolution-melt PCR targeting S. edentatus, Strongylus equinus, and Strongylus asini. On the farm level, prevalence for Strongylus spp. by PCR was 12.5%. Applying a conservative cut-off (sensitivity 0.43, specificity 0.96), 21.2% of all serum samples were positive for antibodies against S. vulgaris larvae (83.3% prevalence on farm level). Newly developed pyrosequencing assays to analyse putatively benzimidazole resistance associated polymorphisms in codons 167, 198, and 200 of the isotype 1 β-tubulin gene of S. vulgaris did not detect such polymorphisms in the four positive samples. Low age and increasing access to pasture were risk factors for egg shedding and seropositivity for S. vulgaris. Time since last treatment increased whereas use of moxidectin and ivermectin for the last treatment decreased the risk for strongyle egg shedding. Noteworthy, horses under selective treatment had significantly higher odds to be seropositive for anti-S. vulgaris antibodies than horses treated four times per year (odds ratio 4.4). The serological findings suggest that exposure to S. vulgaris is considerably higher than expected from direct diagnostic approaches. One potential explanation is the contamination of the environment by a few infected horses, leading to the infection of many horses with larvae that never reach maturity due to regular anthelmintic treatments.

A validated high-throughput method for assaying rat lungworm (Angiostrongylus cantonensis) motility when challenged with potentially anthelmintic natural products from Hawaiian fungi

Parasitic nematodes devastate human and animal health. The limited number of anthelmintics available is concerning, especially because of increasing drug resistance. Anthelmintics are commonly derived from natural products, e.g. fungi and plants. This investigation aimed to develop a high-throughput whole organism screening method based on a motility assay using the wMicroTracker system. Anthelmintic activity of extracts from Hawaiian fungi was screened against third-stage larvae of the parasitic nematode Angiostrongylus cantonensis , categorized according to the degree of motility reduction. Of the 108 crude samples and fractionated products, 48 showed some level of activity, with 13 reducing motility to 0–25% of the maximum exhibited, including two pure compounds, emethacin B and epicoccin E, neither previously known to exhibit anthelmintic properties. The process of bioassay-guided fractionation is illustrated in detail based on analysis of one of the crude extracts, which led to isolation of lamellicolic anhydride, a compound with moderate activity. This study validates the wMicroTracker system as an economical and high-throughput option for testing large suites of natural products against A. cantonensis , adds to the short list of diverse parasites for which it has been validated and highlights the value of A. cantonensis and Hawaiian fungi for discovery of new anthelmintics.

Pharmacological characterization of novel heteromeric GluCl subtypes from C. elegans and parasitic nematodes

BACKGROUND AND PURPOSE

Macrocyclic lactones (MLs) are the most widely used broad-spectrum anthelmintic drugs for the treatment of parasitic nematodes impacting both human and animal health. MLs are known to act as agonist of the nematode glutamate-gated chloride channels (GluCls). However, for many important nematode species, the GluCls subunit composition and pharmacological properties remain largely unknown. In order to get new insights about the GluCl diversity and MLs mode of action, we identified and pharmacologically characterized receptors made of highly conserved GluCl subunits from the model nematode Caenorhabditis elegans, the human filarial nematode Brugia malayi and the horse parasite Parascaris univalens.

EXPERIMENTAL APPROACH

AVR-14, GLC-2, GLC3 and GLC-4 are the most conserved GluCl subunits throughout the Nematoda phylum. For each nematode species, we investigated the ability of these subunits to form either homomeric or heteromeric GluCls when expressed in Xenopus laevis oocytes and performed the detailed pharmacological characterization of the functional channels.

KEY RESULTS

Here, a total of 14 GluCls have been functionally reconstituted and heteromers formation was inferred from pharmacological criteria. Importantly, we report that the GLC-2 subunit plays a pivotal role in the composition of heteromeric GluCls in nematodes. In addition, we describe a novel GluCl subtype, made of the GLC-2/GLC-3 subunit combination, for which a high concentration of the anthelmintics ivermectin and moxidectin reversibly potentiate glutamate-induced response.

CONCLUSION AND IMPLICATIONS

This study brings new insights into the diversity of GluCl subtypes in nematodes and promote novel drug targets for the development of next generation anthelmintic compounds.

Action of Carvacrol on Parascaris sp. and Antagonistic Effect on Nicotinic Acetylcholine Receptors

Parascaris sp. is the only ascarid parasitic nematode in equids and one of the most threatening infectious organisms in horses. Only a limited number of compounds are available for treatment of horse helminthiasis, and Parascaris sp. worms have developed resistance to the three major anthelmintic families. In order to overcome the appearance of resistance, there is an urgent need for new therapeutic strategies. The active ingredients of herbal essential oils are potentially effective antiparasitic drugs. Carvacrol is one of the principal chemicals of essential oil from Origanum, Thymus, Coridothymus, Thymbra, Satureja and Lippia herbs. However, the antiparasitic mode of action of carvacrol is poorly understood. Here, the objective of the work was to characterize the activity of carvacrol on Parascaris sp. nicotinic acetylcholine receptor (nAChR) function both in vivo with the use of worm neuromuscular flap preparations and in vitro with two-electrode voltage-clamp electrophysiology on nAChRs expressed in Xenopus oocytes. We developed a neuromuscular contraction assay for Parascaris body flaps and obtained acetylcholine concentration-dependent contraction responses. Strikingly, we observed that 300 µM carvacrol fully and irreversibly abolished Parascaris sp. muscle contractions elicited by acetylcholine. Similarly, carvacrol antagonized acetylcholine-induced currents from both the nicotine-sensitive AChR and the morantel-sensitive AChR subtypes. Thus, we show for the first time that body muscle flap preparation is a tractable approach to investigating the pharmacology of Parascaris sp. neuromuscular system. Our results suggest an intriguing mode of action for carvacrol, being a potent antagonist of muscle nAChRs of Parascaris sp. worms, which may account for its antiparasitic potency.

The Use of Molecular Profiling to Track Equine Reinfection Rates of Cyathostomin Species Following Anthelmintic Administration

Simple Summary

Cyathostomins (small strongyles) are a multispecies group of intestinal parasites in horses and the main target of deworming efforts by horse owners. It is not known whether species of cyathostomins have individual responses to dewormers. The objective of this study was to identify differences between cyathostomin species in reemergence rates following commercial dewormer treatment. This study used gene sequencing to profile the presence/absence of cyathostomin species in fecal samples at 2-week intervals following deworming to determine how quickly each species reinfected horses. Moxidectin was found to be the most effective at slowing the overall reemergence of these parasites, followed by Ivermectin, then Pyrantel. Seven species were resistant to all three deworming products. This study demonstrates that dewormer sensitivity differs between cyathostomin species, which could lead to more targeted control measures.

Abstract

Cyathostomins are a multispecies parasite ubiquitous in Equids. Cyathostomins have developed resistance to all but one class of anthelmintics, but species-level sensitivity to anthelmintics has not been shown. This study measured reinfection rates of cyathostomin species following the administration of three commercial dewormers. Nine treated horses were compared with 90 untreated controls during June-September 2017–2019. Ivermectin (IVM) (n = 6), Moxidectin (MOX) (n = 8) or Pyrantel (PYR) (n = 8) were orally administered. Fecal samples were collected every 14 d for 98 d. Fecal egg count reductions (FECR) were calculated using a modified McMaster technique. Nineteen cyathostomin species were identified by 5.8S-ITS-2 profiling using amplicon sequencing. Data were analyzed in QIIME1 and R statistical software using presence/absence methods. MOX had the lowest numbers of species present over the time course, followed by PYR then IVM (7.14, 10.17, 11.09, respectively); however, FECR was fastest for PYR. The presence of seven species: Coronocyclus labiatus, Cyathostomum catinatum, Cyathostomum tetracanthum, Cylicocylus elongatus, Cylicodontophorus bicoronatus, Cylicostephanus minutus, and Cylicostephanus goldi were unaffected by treatment (p > 0.05) points to species-specific differences in dewormer sensitivity and environmental persistence. Identifying resistance patterns at the species level will enable mechanistic understandings of cyathostomin anthelmintic resistance and targeted approaches to control them.

Oxidative stress in Strongylus spp. infected donkeys treated with piperazine citrate versus doramectin

Background:

Parasitic infection is one of the main problems in equidae, particularly donkeys.

Aim:

This study evaluated the oxidative stress in donkeys infected with Strongylus spp by determining the correlation between antioxidants levels; malondialdehyde (MDA), total antioxidant capacity (TAC), and the severity of parasitic infection. It also compared the therapeutic efficacy of piperazine citrate as an oral anthelmintic drug and Doramectin as an injectable one.

Methods:

The study was conducted on 40 donkeys naturally infected with Strongylus spp. These donkeys were divided into two groups (20 donkeys each) according to treatment; One group was treated with piperazine citrate (P_ipTG) and the other with doramectin (D_oraTG). Thorough clinical examination, hematological, biochemical, and parasitological assays were performed before (Day 0) and after treatment (Days 7, 14, 21, and 28). All data were statistically analyzed by independent-sample t-test or paired t-test.

Results:

In both groups, mean values of MDA were significantly reduced, while those of TAC were significantly elevated after treatment on days 7, 14, 21, and 28. These significant changes were reported after treatment between P_ipTG and D_oraTG in favor of D_oraTG. Serum concentrations of MDA were significantly reduced, while those of TAC were significantly elevated for D_oraTG treatment group when their values were compared with those of P_ipTG either on days 7, 14, 21, or 28. Significant correlations were reported in P_ipTG and D_oraTG. Negative significant correlations were reported between fecal egg count (FEC) and each of whole blood picture indices (RBCS, Hb, and PCV), serum TAC and faecal egg count reduction percentage FECR%. A positive correlation was seen between FEC and MDA. MDA exhibited a negative correlation with both blood picture and TAC; hence, TAC was positively correlated with these blood picture indices in both P_ipTG and D_oraTG. In P_ipTG, anthelmintic resistance (R) was present on days 7 and 14, while it was suspected (S) at day 21 then it was absent (N) at day 28. In D_oraTG, anthelmintic resistance was suspected (S) on day 7, then it became absent (N) on days 14, 21, and 28 post therapy.

Conclusion:

The immunological status of the infected donkeys had greatly improved after treatment. The therapeutic efficacy of injectable doramectin was more efficient than that of oral piperazine citrate in Strongylus spp. infected donkeys.

Anthelmintics for drug repurposing: Opportunities and challenges

Drug repositioning is defined as a process to identify a new application for drugs. This approach is critical as it takes advantage of well-known pharmacokinetics, pharmacodynamics, and toxicity profiles of the drugs; thus, the chance of their future failure decreases, and the cost of their development and the required time for their approval are reduced. Anthelmintics, which are antiparasitic drugs, have recently demonstrated promising anticancer effects in vitro and in vivo. This literature review focuses on the potential of anthelmintics for repositioning in the treatment of cancers. It also discusses their pharmacokinetics and pharmacodynamics as antiparasitic drugs, proposed anticancer mechanisms, present development conditions, challenges in cancer therapy, and strategies to overcome these challenges.

Pharmacokinetic properties of abamectin after oral administration in dogs

As the introduction of concentrated cattle pour-on products containing abamectin, there have been veterinary reports of both fatal and non-fatal poisoning in New Zealand working dogs. Because these products are highly palatable to dogs, a toxic dose is readily ingested. The pharmacokinetic properties of abamectin in dogs are not published in the public domain. This information is important in understanding the processes of absorption and elimination when treating poisoned dogs and is useful in determining an appropriate treatment for poisoned dogs. The pharmacokinetic properties of abamectin administered orally to six healthy dogs (3 male and 3 female) at a dose of 0.2 mg/kg were established. Plasma concentrations of abamectin were determined by high-performance liquid chromatography (HPLC) coupled with a fluorescence detector. The maximum plasma concentration (C_max ) for abamectin was 135.52 ± 38.6 ng/ml at 3.16 ± 0.75 h. The elimination half-life (T1/2 elim (h)) was 26.51 ± 6.86 h. The area under the curve (AUC 0-∞) was 3723.50 ± 1213.08 ng h/ml. The mean residence time (MRT) was 38.82 ± 8.93 h. These pharmacokinetic data provide helpful information regarding the treatment of poisoned dogs.

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

Donkeys have been used as working animals for transport and farm activities worldwide. Recently, in European countries, there has been an increasing interest in donkeys due to their use as pets, onotherapy or milk production. During 2014-2016, a countrywide survey was conducted to determine prevalence and risk factors of principal helminth infections in 1775 donkeys in 77 Italian farms. A questionnaire on management and parasite control practices was filled out for each farm. Faecal samples were examined using a modified McMaster technique, a centrifugation/flotation method and a sedimentation technique. Pooled coprocultures were performed for differentiation of strongylid eggs. Strongyles were the most common parasites detected (84.9%), followed by Dictyocaulus arnfieldi (6.9%), Oxyuris equi (5.8%), Parascaris spp. (3.6%), Anoplocephala spp. (1.0%), Strongyloides westeri (0.3%). Coprocultures revealed an omnipresence of cyathostomins (100%), followed by Strongylus vulgaris (31.0%), Poteriostomum spp. (25.0%), Triodontophorus spp. (9.0%), Strongylus edentatus (7.0%), Strongylus equinus (5.0%). Logistic regression analysis identified breed, co-pasture with horses, living area, herd size and number of treatments as significantly associated with strongyles. Sex, age, living area and herd size were significantly associated with Parascaris spp. Dictyocaulus arnfieldi was significantly associated with sex, grass, co-pasture with horses, living area and herd size. Strongylus vulgaris was significantly associated with living area and herd size. The mean number of anthelmintic treatments/year was 1.4; most of the donkeys (71.8%) were dewormed using an ivermectin drug. It is important to design parasite programs to specifically address both D. arnfieldi and S. vulgaris in donkeys, and this is especially important if donkeys co-graze with horses.

Gastrointestinal Strongyles Egg Excretion in Relation to Age, Gender, and Management of Horses in Italy

Simple Summary

Horses worldwide are plagued by gastrointestinal parasites that can lead to severe health problems. The occurrence and intensity of these worm infections vary based on the geographical location, season, and animal management strategies applied. One of these strategies is to monitor the parasite situation in different parts of the world. This research investigates the abundance, proportions, and risk factors of strongyle egg shedding of horses in Italy. Overall, the results showed that approximately 40% of all horses in Italy shed strongyle eggs and that almost 90% of stables have at least one infected animal. In addition, most parasite eggs are found in just a small fraction of the horse population, confirming the need for improved parasite control strategies.

Abstract

Current equine helminth control strategies play a key role in strongyle epidemiology and anthelmintic resistance and have led to the recommendation for new treatment plans, which include diagnostic and efficacy surveillance. Assessing the equine strongyle distribution patterns would thus be useful and this study describes the strongyle prevalence in the equine population in Italy through coprological analysis and coproculture. In addition, individual data on each animal were collected in order to identify risk factors associated with strongyle egg shedding. Of the total number of stables investigated, 86.4% were found to have at least one positive animal and a 39.5% prevalence of strongyle egg shedding with a mean eggs per gram (EPG) of 245. A total of 80% of the total recorded EPG was shed from 12.8% of positive horses, thus confirming the need for new targeted intervention strategies. Significant differences in parasite prevalence were found based on season, sex, geographical distribution, management and rearing system, and breed. Significantly lower EPG values were found in horses that had received anthelmintic treatment, and macrocyclic lactones (MLs) were the most effective. Lastly, although large strongyles are more pathogenic, horses in Italy are mainly burdened by small strongyles, which pose an important animal health risk requiring continuous parasitological monitoring.

Equine Drug Transporters: A Mini-Review and Veterinary Perspective

Xenobiotic transport proteins play an important role in determining drug disposition and pharmacokinetics. Our understanding of the role of these important proteins in humans and pre-clinical animal species has increased substantially over the past few decades, and has had an important impact on human medicine; however, veterinary medicine has not benefitted from the same quantity of research into drug transporters in species of veterinary interest. Differences in transporter expression cause difficulties in extrapolation of drug pharmacokinetic parameters between species, and lack of knowledge of species-specific transporter distribution and function can lead to drug–drug interactions and adverse effects. Horses are one species in which little is known about drug transport and transporter protein expression. The purpose of this mini-review is to stimulate interest in equine drug transport proteins and comparative transporter physiology.

Anthelmintic Efficacy and Pharmacokinetics of Ivermectin Paste after Oral Administration in Mules Infected by Cyathostomins

Ivermectin (IVM) is an anthelmintic compound commonly used off-label in mules due to its broad-spectrum of activity. Despite the general use of IVM in mules with the same dose and route of administration licensed for horses, significant pharmacokinetic differences might exist between horses and mules, as already observed for donkeys. The aim of the present study was to evaluate the pharmacokinetic profile and anthelmintic efficacy of an oral paste of IVM in mules naturally infected with cyathostomins. Fifteen adult mules with fecal egg counts (FEC) ≥200 eggs per gram (EPG), with exclusive presence of cyathostomins, were included in the study. All mules were orally treated with IVM according to the manufacturer's recommended horse dosage (200 µg/kg body weight). FECs were performed before (day-10 and day-3) and after treatment at days 14 and 28 by using a modified McMaster method. The FEC reduction (FECR%) was also calculated. Blood samples were collected from five animals at various times between 0.5 h up to 30 days post treatment to determine pharmacokinetic parameters. The maximum IVM serum concentration (Cmax) was 42.31 ± 10.20 ng/mL and was achieved at 16.80 ± 9.96 hours post-treatment (Tmax), area under the curve (AUC) was 135.56 ± 43.71 ng × day/mL. FECR% remained high (>95%) until the 28th day.

In Vitro Inhibiting Effects of Three Fungal Species on Eggs of Donkey Gastrointestinal Strongyles

Recently, donkeys have gained popularity mainly due to the use of donkey milk by the cosmetic industry and for human consumption. Gastrointestinal strongyles (GIS) are considered a potential cause of disease and reduced production in infected donkeys. European laws limit the use of anthelmintic drugs for the control of GIS in dairy donkey farms, thus the need to develop alternative control methods. This study aimed to test the in vitro inhibiting effects of three chitin degrading fungi (Scopulariopsis brevicaulis, Metarhizium anisopliae, and Beauveria bassiana) on the hatch and viability of donkey GIS eggs by using the egg hatch test, and to compare their activity to that of Pochonia chlamydosporia. About 150 eggs were added to 0.5 mL of sterile saline solution containing about 1.4 × 10⁸ spores of each fungal species or with 0.5 mL of sterile saline solution only (untreated controls). After incubation, the percentage of egg hatch reduction was calculated, and data were statistically analyzed. All fungi were able to significantly reduce (p < 0.05) the hatch of GIS eggs compared to the untreated controls. Further studies that aim to investigate the efficiency of these fungi in reducing donkey GIS eggs in contaminated environments are encouraged.

Wild horse populations in south-east Australia have a high prevalence of Strongylus vulgaris and may act as a reservoir of infection for domestic horses

Australia has over 400,000 wild horses, the largest wild equid population in the world, scattered across a range of different habitats. We hypothesised that wild horse populations unexposed to anthelmintics would have a high prevalence of Strongylus vulgaris infections. Verminous endarteritis and colic due to migrating S. vulgaris larvae is now absent or unreported in domestic horses in Australia, yet wild horses may pose a risk for its re-emergence. A total of 289 faecal egg counts (FECs) were performed across six remote wild horse populations in south-east Australia, of varying densities, herd sizes and habitats. Total strongyle egg counts ranged from 50 to 3740 eggs per gram (EPG, mean 1443) and 89% (257/289) of faecal samples had > 500 EPG, classifying them as 'high level shedders'. There were significant differences in mean total strongyle FECs between different locations, habitats and population densities. Occurrence of S. vulgaris was not predictable based on FECs of total strongyle eggs or small (<90 μm) strongyle eggs. A high prevalence of S. vulgaris DNA in faecal samples was demonstrated across all six populations, with an overall predicted prevalence of 96.7%. This finding is important, because of the ample opportunity for transmission to domestic horses. The high prevalence of S. vulgaris suggests vigilance is required when adopting wild horses, or when domestic horses graze in environments inhabited by wild horses. Appropriate veterinary advise is required to minimize disease risk due to S. vulgaris. Monitoring horses for S. vulgaris using larval culture or qPCR remains prudent. Gastrointestinal parasites in wild horse populations may also serve as parasite refugia, thus contributing to integrated parasite management when facing emerging anthelmintic resistance.

Preliminary Observations of the Effect of Garlic on Egg Shedding in Horses Naturally Infected by Intestinal Strongyles

Intestinal strongyles are the most common endoparasites of horses, and anthelmintic treatments are the main strategy to control these nematodes. However, the development of anthelmintic resistance has led to a decreased efficacy of synthetic drugs, and for this reason, there is a growing interest in alternative control strategies as the use of medicinal plants. The aim of the present study was to determine the in vivo efficacy of garlic (Allium sativum) in horses naturally infected by intestinal strongyles. The field trial was conducted in a horse trotter farm in Southern Italy. Fifteen mares were selected based on fecal egg count >200 eggs per gram and allocated into three groups of five animals: fresh garlic group (FG group), animals received 40 g of fresh crushed garlic once daily for 15 days; dry garlic group (DG group), animals received 40 g of commercial dry garlic flakes food supplement once daily for 15 days; and control group (C group), not treated. Two weeks after the first administration of garlic, fecal egg count reduction test showed failure of garlic to reduce intestinal strongyles egg shedding (-11.7% and -19.4% for FG and DG groups, respectively). Red blood cell count values were in the normal ranges over the entire period of garlic administration. In our study model, the oral administration of garlic formulations has no effect on reducing the egg shedding of intestinal strongyles, and the garlic supplementation over a short period of time is not responsible for hematological changes in horses.