Plasma disposition, milk excretion and parasitological efficacy of mebendazole in donkeys naturally infected by Cyathostominae

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.

Metabolism and pharmacokinetics of mebendazole in Japanese pufferfish (Takifugu rubripes)

As a typical and broad-spectrum benzimidazole, mebendazole (MBZ) has long been used in human and veterinary medicine to treat parasitic infestations, and is widely employed in the aquaculture of Japanese pufferfish (Takifugu rubripes). However, there have been no studies examining the pharmacokinetic characteristics of MBZ in Japanese pufferfish. Furthermore, the presence of MBZ and its metabolites in animal-derived raw food represents a notable safety concern. Here, we investigated the metabolism of MBZ using a UPLC-Q-TOF system. Additionally, we evaluated the pharmacokinetics of MBZ and two metabolites, 2-amino-5(6)-benzoylbenzimidazole (MBZ-NH₂) and 5-hydroxymebendazole (MBZ-OH), in Japanese pufferfish following intramuscular injection of 20 mg/kg MBZ. We detected three metabolites of MBZ (M1-M3), among which, 2-amino-5(6)-(a-hydroxybenzyl) benzimidazole (M3) was detected in an aquatic animal for the first time. The plasma dispositions of MBZ, MBZ-NH₂, and MBZ-OH were characterized by low plasma clearance, medium distribution volume, and long terminal half-life. Moreover, these compounds were widely distributed in the muscle, from which they were rapidly cleared. The pharmacokinetics and metabolism of mebendazole in Japanese pufferfish are described for the first time in this study. Our findings provide a basis for the rational application of MBZ in Japanese pufferfish farming and contribute to our understanding of the metabolism of MBZ in cultured fish.

Cyathostomin fecal egg count and milk quality in dairy donkeys

This study was performed to assess the possible relationship between gastrointestinal strongylid infections and milk quantity and quality in donkeys used for milk production. Individual fecal and milk samples were collected from 16 multiparous lactating jennies of Amiatina breed at their 6th month of lactation. Statistical analysis was carried out between strongylid eggs per gram of faeces (EPG) and milk parameters. All animals were found to shed cyathostomin eggs, with EPG ranging from 150 to 1900. A higher milk production was observed in animals showing an EPG< 250, but this result was statistically not significant. Conversely, significant higher concentrations of milk urea and pH values, and lower concentrations of milk lactose, were observed in jennies with an EPG >1000. In conclusion, results from this study suggest that cyathostomin EPG values > 1000 may affect milk quality in dairy donkeys. Considering the novelty of these findings, more data needs to be collected to determine EPG thresholds to be used as a good marker for parasite infections influencing milk performance and quality in donkeys.

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.

Intestinal Strongyle Genera in Different Typology of Donkey Farms in Tuscany, Central Italy

Intestinal strongyles are common helminths of donkeys, in which they may be responsible for disease and poor performance. This study aimed to identify intestinal strongyle genera in 55 naturally infected donkeys from three different farm typologies in Tuscany, central Italy, using morphological and metrical analysis of third stage larvae (L3) obtained from faecal cultures. Larvae were identified using two previous reported morphological identification keys. Moreover, eggs per gram (EPG) data were also evaluated to assess differences, if any, according to the farm typology, sex, and age of the examined donkeys. The results showed that small strongyles were prevalent in all donkey farms. In all examined farms, most (92–100%) of L3 were identified as cyathostomin species of the genera Cylicocyclus spp. and Cylicostephanus spp. Large strongyles of the genera Strongylus spp. and Triodontophorus spp., were identified at low percentage (8%), only in the single organic farm included in the study. A high agreement was observed between the two different morphometric keys used. No significant differences were found for EPG according to farm typology, and sex and age from the examined donkeys. This is the first report about genera identification of intestinal strongyles infecting donkeys in Tuscany, Italy.

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.

Clinical Pharmacology in Donkeys and Mules

Donkeys and mules show several pharmacodynamic and pharmacokinetic idiosyncrasies that have to be fully considered by any clinician dealing with these species. Because they possess an increased metabolic rate and cellular water content compared with horses, higher doses (or shorter dosing intervals) are usually recommended for those drugs where pharmacologic studies have been performed. Nonetheless, owing to the lack of species-specific information, this assumption cannot be arbitrarily applied. Thus, when a drug protocol published for horses is extrapolated to a donkey or a mule, a close monitoring is required to detect any secondary effect or subdosing.

In Vitro Anthelmintic Activity of Saponins Derived from Medicago spp. Plants against Donkey Gastrointestinal Nematodes

With the aim to find new effective natural compounds for the control of nematodes, the in vitro anthelminthic properties of purified 1% saponins showing different chemical compositions and derived from Medicago sativa (MS), Medicago arborea (MA), Medicago polymorpha cultivar 'Santiago' (MPS), M. polymorpha cultivar 'Anglona' (MPA), and 1% prosapogenins from M. sativa (MSp), were evaluated and compared. As a source of nematode eggs, pooled fresh fecal samples taken from dairy donkeys naturally infected by gastrointestinal nematodes were used. From fecal samples, eggs were recovered, suspended in deionized water, and used immediately in the bioassay (egg hatch test). The activity of the tested compounds was compared to positive (0.1% thiabendazole) and negative (deionized water and 1% DMSO) controls. All experiments were repeated in triplicate and the obtained data were statistically analyzed. All the tested plant compounds caused a significant (p < 0.05) inhibition of nematode egg hatching (>80%). Moreover, all saponins and prosapogenins showed in vitro anthelmintic properties statistically comparable to that of the reference drug (p < 0.05), except for MPS extract. Obtained results showed that the different Medicago saponins evaluated in this study possess high anthelmintic properties against gastrointestinal nematodes of dairy donkeys, although to a different extent depending on their composition.

Anthelmintic drugs used in equine species

Internal parasites of horses comprise an intractable problem conferring disease, production and performance losses. Parasitism can rarely be controlled in grazing horses by management alone and anthelmintic drugs have formed the basis of therapy and prophylaxis for the last sixty years. The pharmacology of the anthelmintic drugs available dictate their spectrum of activity and degree of efficacy, their optimal routes of administration and characteristics which prevent some routes of administration, their safety tolerance and potential toxicities and as a consequence of their persistence in the body at effective concentrations their use in epidemiological control programmes. Their use has also resulted in the selection of parasites with genetically controlled characteristics which reduce their susceptibility to treatment, characteristics which are often common to whole chemical classes of anthelmintics. Pharmacological properties also confer compatibility in terms of safety and persistence with other anthelmintic drugs and thus the potential of combinations to treat parasites from different phylogenetic groups such as nematodes, cestodes and trematodes and also the potential by agency of their different molecular mechanisms of action to delay the selection of resistant genes. The major groups of anthelmintics now available, the benzimidazoles (BZD), macrocyclic lactones (MLs) and tetrahydropyrimidines are all highly effective against their targeted parasites (primarily nematodes for BZD's and ML's and cestodes for tetrahydropyrimidines) easily administered orally to horses and are well tolerated with wide margins of safety. Nevertheless, some parasitic stages are inherently less susceptible such as hypobiotic stages of the small strongyles (cyathostomins) and for some such as the adult stages of cyathostomins resistance has developed. Furthermore, for some less common parasites such as the liver fluke unlicensed drugs such as the salicylanilide, closantel have been used. A deep understanding of the pharmacology of anthelmintic drugs is essential to their optimal use in equine species.

Plasma pharmacokinetics and muscle residue dynamics of mebendazole in Carassius auratus

Mebendazole is approved for use in aquatic animals and is widely used in Chinese aquaculture. We developed a pharmacokinetic and residue analysis for mebendazole levels in the goldfish (Carassius auratus). Plasma and muscle samples of C. auratus were taken after oral administration of 10 mg/kg mebendazole. The maximal drug plasma concentration of 0.55 mg/L was achieved at 48 hr and then declined with the elimination half-life (T_1/2β ) of 7.99 hr. Administration of 10 mg/kg by oral gavage for 5 successive days resulted in a peak mebendazole concentration of 0.70 mg/kg in muscle at 96 hr after the last dose. The drug was then eliminated at a relatively slow rate from muscle with T_1/2β of 68.41 hr. There was no detectable mebendazole in any muscle samples at 24 days postadministration. The AUC_last in plasma and muscle was 19.42 and 105.33 mg hr/L, respectively. These data provide information for dosage recommendations and withdrawal time determinations for mebendazole use in aquariums.