Demonstration of reduced efficacy against cyathostomins without change in species composition after pyrantel embonate treatment in Swedish equine establishments.

Consisting of approximately 50 different species, the cyathostomin parasites are ubiquitous in grazing horses. Co-infection with several species is common, and large burdens can cause the fatal disease of larval cyathostominosis. Due to intense anthelmintic drug use, cyathostomin resistance has developed to all available anthelmintic drug groups. Resistance to the anthelmintic drug pyrantel (PYR) has been documented in over 90% of studies published over the past two decades. In Sweden, a study performed in the early 2000s only confirmed resistance in 4.5% of farms. Further, prescription-only administration of equine anthelmintic drugs was enforced in Sweden in 2007. However, it is unknown if this conservative drug use has maintained PYR efficacy in cyathostomins. The aim of the present study was to investigate the effect of PYR on cyathostomin infection in Sweden using fecal egg count reduction tests (FECRTs). Further, the effect of PYR treatment on cyathostomin species composition was studied using metabarcoding. Sixteen farms with at least six horses excreting a minimum of 100 eggs per gram feces were included. Using the current World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines, PYR resistance was demonstrated in nine of farms, with seven farms showing full susceptibility. Farms with low biosecurity measures had significantly lower efficacy of PYR treatment. The most common cyathostomin species were Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cys. calicatus, Cys. goldi, Cys. minutus, Coronocyclus coronatus and Cya. pateratum, accounting for 97% of all sequence reads prior to treatment. Of these, Cyc. nassatus and Cya. catinatum had the highest occurrence, accounting for 68% of all sequence reads prior to PYR treatment. Treatment did not significantly affect the species composition. The results highlight the importance of drug efficacy testing when using PYR to treat cyathostomin infection, even when selective anthelmintic treatment and thus low treatment intensity, is used on the farm.

Efficacy of an oral combination of moxidectin, afoxolaner, and pyrantel pamoate for the prevention of heartworm disease in dogs.

Dirofilaria immitis, the mosquito-borne agent of dirofilariosis, a chronic and sometimes fatal cardiopulmonary canine disease, is endemic in most warm and temperate regions in the world. The efficacy of an oral endectoparasiticide product (test product or TP) combining moxidectin, afoxolaner, and pyrantel pamoate was evaluated for the prevention of heartworm disease in dogs, in two laboratory and one field studies. In each laboratory study, 20 D. immitis-naïve beagle dogs were experimentally infected with D. immitis. Ten control dogs were sham-treated, and ten dogs were administered the TP targeting the minimum effective dose, six times monthly and starting 30 days post infection. At necropsy seven months after inoculations, no heartworms were found in any of the TP treated dog, whereas 19 to 42 live heartworms were found in the control dogs. In each study, treatment efficacy was 100% and the difference between treated and untreated groups was highly significant (p < 0.0001). A field study was conducted through the full transmission season in several heartworm-endemic regions of the United States. One hundred and twenty client-owned dogs that were negative for D. immitis at enrollment were administered twelve monthly oral doses of the TP at label dose. Blood tests for D. immitis antigen and modified Knott's tests for microfilariae remained negative through the full duration of the study, demonstrating that all dogs were protected from heartworm infection during the full transmission season. These studies demonstrated that TP administered monthly for at least six doses is effective at preventing dirofilariosis.

MANAGEMENT OF A FATAL OUTBREAK OF STRONGYLOIDIASIS IN A CAPTIVE POPULATION OF PANTHER CHAMELEONS (FURCIFER PARDALIS) WITH IVERMECTIN.

An outbreak of the nematode Strongyloides sp. occurred in a population of 18 male and 29 female panther chameleons (Furcifer pardalis) at the Singapore Zoo. The parasite was first detected in one individual during routine microscopic examination of feces using the direct examination and magnesium sulfate flotation methods. The parasite was later found to have a closest match (98.96%) with Strongyloides sp. Okayama by DNA sequencing. Over a period of 6 mon, 97.9% (46/47) of the panther chameleons tested positive for the parasite, and 25.5% (12/47) of the animals died due to the disease. All the animals that died were female. Of the positive tests, magnesium sulfate flotation identified the parasite 98.1% (105/107) of the time, compared to direct fecal microscopy, which identified the parasite only 43.9% (47/107) of the time. Parasite eggs were detected in 100% (105/105) of the positive magnesium sulfate flotation tests but only 66.0% (31/47) of the positive direct fecal microscopy tests. Parasite larvae were detected in 61.7% (29/47) of the positive direct fecal microscopy tests but only 9.5% (10/105) of the magnesium sulfate flotation tests. Treatments with fenbendazole and pyrantel pamoate at published doses were ineffective at eliminating the parasite. Ivermectin (0.2 mg/kg PO q2wk for two doses) was successful at treating the parasite, with all animals testing negative for the parasite at the end of the treatment course without any observed adverse reactions. However, complete eradication of the parasite could not be achieved, as Strongyloides sp. could still be detected in the population on routine coproscopy intermittently over 3 yr. There were no further mortalities due to the disease with prompt treatment with ivermectin. Strongyloidiasis may cause high morbidity in panther chameleons, but severe disease leading to mortality can be prevented with the use of ivermectin.

Apparent treatment failure of praziquantel and pyrantel pamoate against anoplocephalid tapeworms.

Anoplocephalid tapeworms are commonly occurring in grazing horses around the world. Two currently available anthelmintics have documented high efficacy against Anoplocephala perfoliata; praziquantel in various dosages ranging from 1.0 to 2.5 mg/kg and pyrantel pamoate administered at 13.2 mg base/kg. Anthelmintic resistance has not been reported in A. perfoliata, but anecdotal reports made during 2022 have suggested a possible loss of efficacy for both actives. This paper reports fecal egg count data from a Thoroughbred operation in Central Kentucky in 2023. Fifty-six yearlings were first dewormed with a combination of ivermectin (200 µg/kg) and praziquantel (1.5 mg/kg) and subsequently treated with pyrantel pamoate (13.2 mg base/kg). Fecal egg counts were determined at the day of treatment and again 14 days post-treatment. Two groups of mares (n = 39 and 45) were also treated with ivermectin/praziquantel and examined pre- and post-treatment. Low efficacy of ivermectin and pyrantel pamoate was demonstrated against strongylid parasites in the yearlings with mean Fecal Egg Count Reductions (FECRs) at 75.6% or below and upper 95% credible interval (CI) limits below 90% in all cases. Overall anti-cestodal FECR levels in the yearlings were 23.5% (95% CI: 11.2-48.0) for praziquantel and 50.9% (20.5-72.0) for pyrantel pamoate. Praziquantel eliminated anoplocephalid eggs from three of 17 yearlings, but another 5 yearlings went from negative to positive status following treatment. Pyrantel pamoate failed to eliminate anoplocephalid eggs from any of 14 treated tapeworm-positive yearlings. Nine of 84 mares tested positive for anoplocephalid eggs, and seven of these were still positive post praziquantel treatment. These findings sharply contrast data from historic field efficacy studies conducted for both actives and raise concern about anthelmintic resistance having possibly developed. This emphasizes the need for developing and refining antemortem methodologies for evaluating anti-cestodal treatment efficacy and for searching for possible alternative treatment options.

Clinical and Parasitological Evaluation of Ivermectin and Ivermectin + Pyrantel Against Oxyuris Equi in Equines.

The equine pinworm could become an increasingly common problem, as there are reports of failure in the control of this parasite. The aim of this study was to evaluate the effects of ivermectin (IVM) and IVM combined with pyrantel pamoate (PYR). Thirteen parasitological positive equines were treated with oral IVM (200 µg/kg) and therapeutic efficacy, clinical recovery and the egg reappearance period (ERP) were evaluated. In cases for which ERP was shorter than the pre-patent period (PPP), a second treatment was performed with IVM (200 µg/kg) + PYR (6.6 mg/kg), followed by the same evaluation criteria described above. Therapeutic efficacy was 100% with IVM + PYR and 53.84% with IVM. The mean ERP was shorter than the PPP with both formulations, 77.55 days with IVM + PYR and 50 days with IVM. The presence of egg mass was always associated with a least one clinical sign. The reduction in the number of clinical signs per animal from Day 0 to Day 30 was greater in equines treated with IVM + PYR compared to those treated with IVM alone. The animals treated with IVM were 4.5-fold more likely to present clinical signs 30 days after treatment than those treated with IVM+PYR. A negative correlation was found between ERP and the number of clinical signs at 30 days in the animals treated with IVM. This clinical and parasitological evaluation demonstrated that the combination of IVM+PYR was more effective than IVM alone to control Oxyuris equi.

Multiple anthelmintic drug resistance in hookworms (Ancylostoma caninum) in a Labrador breeding and training kennel in Georgia, USA.

OBJECTIVE: To evaluate the efficacy of the 3 major classes of anthelmintics used for the treatment of hookworms in dogs in the US and an extralabel treatment with an FDA-approved product for use in cats in a Labrador kennel with a history of persistent hookworm infections. ANIMALS: 22 dogs housed in a single kennel comprised of the following breeds: 19 Labrador Retrievers, 1 English Cocker Spaniel, 1 Chesapeake Bay Retriever, and 1 Boykin Spaniel. PROCEDURES: We performed a fecal egg count (FEC) reduction test using 22 dogs that were allocated randomly to 1 of 5 treatment groups: pyrantel pamoate (Pyrantel pamoate suspension), fenbendazole (Safe-Guard suspension 10%), milbemycin oxime (Interceptor), moxidectin plus imidacloprid (Advantage Multi), and emodepside plus praziquantel (Profender topical solution for cats). FEC was performed on samples collected on days 0 and 11. RESULTS: FEC reductions for the milbemycin oxime, moxidectin plus imidacloprid, and emodepside plus praziquantel groups were 43.9%, 57.4%, and 100%, respectively. The FEC increased following treatment for the pyrantel and fenbendazole groups. CLINICAL RELEVANCE: These data demonstrate that the Ancylostoma caninum infecting the dogs in this kennel are highly resistant to all major anthelmintic classes approved for use in dogs in the US but are susceptible to emodepside. This was the first report of multiple anthelmintic drug-resistant A caninum in a dog kennel that does not involve Greyhounds.

Gastrointestinal helminths in dogs: occurrence, risk factors, and multiple antiparasitic drug resistance.

Helminth infections are detrimental to the overall health of dogs; therefore, this study aimed to identify antiparasitic-resistant helminths and evaluate the infection rate and risk factors for parasitism in canines. For this purpose, a parasitological evaluation of 38 randomly selected animals was performed, followed by the evaluation of the anthelminthic efficacy of three drugs: pyrantel pamoate with praziquantel (Canex Composto®), fenbendazole (Fenzol Pet®), and milbemycin oxime with praziquantel (Milbemax C®). Among the evaluated animals, 22/38 (57.89%) tested negative and 16/38 (42.71%) tested positive for Ancylostoma caninum infection. Evaluation of the efficacy of antiparasitic drugs showed that 12/16 (75%) dogs were infected with helminths that were susceptible to pyrantel pamoate with praziquantel. Among those for which pyrantel pamoate with praziquantel was not effective, 3/4 (75%) were susceptible to fenbendazole, while the remaining case resistant to both pyrantel pamoate with praziquantel and fenbendazole was sensitive to milbemycin oxime with praziquantel (100%). The odds ratio of infection in dogs inhabiting environments containing soil or grass was 6.67 times higher than that in dogs inhabiting impermeable environments. Mixed-breed dogs (SRD) were 6.54 times more likely to be infected compared to purebred dogs. A. caninum resistant to pyrantel pamoate with praziquantel (4/16, 25%) and fenbendazole (1/4, 25%) were detected. The results of this study demonstrated the importance of coproparasitological monitoring by professionals before and after treatments to assess antiparasitic drug effectiveness, ensure animal health and welfare, and minimize animal exposure to risk factors.

In vivo efficacy of pyrantel pamoate as a post-exposure prophylactic for rat lungworm (Angiostrongylus cantonensis).

Rat lungworm (Angiostrongylus cantonensis) is a neurotropic nematode, and the leading cause of eosinophilic meningitis worldwide. The parasite is usually contracted through ingestion of infected gastropods, often hidden in raw or partially cooked produce. Pharmaceutical grade pyrantel pamoate was evaluated as a post-exposure prophylactic against A. cantonensis. Pyrantel pamoate is readily available over-the-counter in most pharmacies in the USA and possesses anthelmintic activity exclusive to the gastrointestinal tract (GIT). Administering pyrantel pamoate immediately after exposure should theoretically paralyze the larvae in the GIT, causing the larvae to be expelled via peristalsis without entering the systemic circulation. In this study, pyrantel pamoate (11 mg/kg) was orally administered to experimentally infected rats at 0, 2-, 4-, 6-, or 8-h post-infection. The rats were euthanized six weeks post-infection, and worm burden was evaluated from the heart-lung complex. This is the first in vivo study to evaluate its efficacy against A. cantonensis. This study demonstrates that pyrantel pamoate can significantly reduce worm burden by 53-72% (P = 0.004), and thus likely reduce the severity of infection that is known to be associated with worm burden. This paralyzing effect of pyrantel pamoate on the parasite may also be beneficial for delaying the establishment of infection until a more suitable anthelmintic such as albendazole is made available to the patient.

Preclinical and Clinical Characteristics of the Trichuricidal Drug Oxantel Pamoate and Clinical Development Plans: A Review.

Soil-transmitted helminths (Ascaris lumbricoides, hookworm and Trichuris trichiura) infect about one-fifth of the world's population. The currently available drugs are all highly efficacious against A. lumbricoides. However, they are only moderately efficacious against hookworm and poorly efficacious against T. trichiura. Oxantel, a tetrahydropyrimidine derivative discovered in the 1970s, has recently been brought back to our attention given its high efficacy against T. trichiura infections (estimated 76% cure rate and 85% egg reduction rate at a 20 mg/kg dose). This review summarizes the current knowledge on oxantel pamoate and its use against T. trichiura infections in humans. Oxantel pamoate acts locally in the human gastrointestinal tract and binds to the parasite's nicotinic acetylcholine receptor (nAChR), leading to a spastic paralysis of the worm and subsequent expulsion. The drug is metabolically stable, shows low permeability and low systemic bioavailability after oral use. Oxantel pamoate was found to be safe in humans, with only a few mild adverse events reported. Several clinical trials have investigated the efficacy of this drug against T. trichiura and suggest that oxantel pamoate is more efficacious against T. trichiura than the currently recommended drugs, which makes it a strong asset to the depleted drug armamentarium and could help delay or even prevent the development of resistance to existing drugs. We highlight existing data to support the use of oxantel pamoate against T. trichiura infections.

Evaluation of Commercially Available Anthelminthics in Laboratory Models of Human Intestinal Nematode Infections.

Drug repurposing from veterinary to human medicine has been the main strategy to develop the four recommended human anthelminthics, albendazole, mebendazole, levamisole, and pyrantel pamoate, for the treatment of soil-transmitted helminthiasis. A systematic, head-to-head comparison of the anthelminthic activity profile of derivatives of these drugs and other anthelminthics developed in succession has not been conducted to date. We studied eight benzimidazoles, five macrocyclic lactones, tribendimidine, levamisole, and pyrantel pamoate in laboratory models of human intestinal nematode infections. In vitro studies were performed on Trichuris muris L1 larval stage and adults, as well as Ancylostoma ceylanicum, Necator americanus, Heligmosomoides polygyrus, and Strongyloides ratti L3 larvae and adults. The benzimidazoles showed pronounced differences against larval and adult stages, with low activity against larvae and the highest activity observed against adult N. americanus (IC50 of flubendazole 1.1 µM). The macrocyclic lactones, on the other hand, revealed a higher activity on the larval stages, with the lowest IC50 values observed against N. americanus L3 (IC50 values of 0.03-3 µM). In vivo studies were performed in the T. muris and H. polygyrus mice models, with moxidectin and milbemycin oxime showing the highest activity against H. polygyrus (ED50 values of 0.009 and 0.006 mg/kg, respectively) and moxidectin and abamectin being the most effective drugs against T. muris (ED50 values of 0.2 and 0.5 mg/kg, respectively). Laboratory models for soil-transmitted helminthiasis can assist characterizing potential drug candidates. Drugs should be evaluated against different species, and both the adult and larval stages as activities could differ considerably.

Risk factors for equine intestinal parasite infections and reduced efficacy of pyrantel embonate against Parascaris sp.

Gastrointestinal parasites, Parascaris sp. and strongyles, are common in young horses worldwide and control of these parasites is challenged by increasing anthelmintic resistance. Our aim was to identify risk factors for these infections as well as to assess the efficacy of fenbendazole (dose 7.5 mg/kg) and pyrantel embonate (dose 19 mg/kg) against Parascaris sp. We also evaluated association between owner observed symptoms and patent infections with these parasites. Fecal samples were collected from 367 young horses in Finland and a questionnaire study was conducted. Fecal egg counts were performed by Mini-FLOTAC® method. Univariable logistic regression models using patent infection status (Yes/No), separately for Parascaris sp. and strongyle infections as an outcome were run initially to screen potential risk factors collected by the questionnaire. After the initial screening, multiple logistic regression models were constructed and run to account for correlated data structure, risk factors and potential confounders simultaneously. Two significant risk factors for a patent Parascaris sp. infection were found: breeding farm size (p = 0.028) and frequency of horse movements (p = 0.010). Horses originating from large breeding farms were more likely (OR = 2.47, 95% confidence interval (CI) 1.10-5.51) to shed Parascaris sp. eggs upon relocation to training stables compared to horses originating from small breeding farms. Horses living in farms with frequent horse movements to other premises had higher odds (OR = 3.56, 95% CI: 1.35-9.39) of a patent Parascaris sp. infection compared to farms with less frequent horse movements. Risk factors for patent strongyle infection included age (p < 0.001) and season (p = 0.017). Horses were less likely (OR = 0.27, 95% CI: 0.10 - 0.66) to shed strongylid eggs during the spring compared to the winter. Horses excreting over 200 ascarid eggs per gram were included in the anthelmintic efficacy trial. A mean FECR less than 90% was interpreted as presence of anthelmintic resistance. The mean FECR was 98.5% (95% CI: 95.8-100) and 68.0% (95% CI: 52.7-83.3) in the fenbendazole (n = 31) and pyrantel (n = 26) treatment groups, respectively. In conclusion, we identified two new risk factors for patent Parascaris sp. infection; breeding farm size and frequency of horse movements. Reduced efficacy of pyrantel against Parascaris sp. was observed for the second time in Europe. A relatively high Parascaris sp. prevalence in yearlings (34%) and two-year-olds (20%) was observed, which has not been reported earlier. An association between symptoms and a patent Parascaris sp. infection was observed in foals.

The importance of anthelmintic efficacy monitoring: results of an outreach effort.

Anthelmintic resistance in equine cyathostomin parasites is widespread. A surveillance-based parasite control program using fecal egg counts (FECs) and fecal egg count reduction tests (FECRTs) to decrease anthelmintic use and monitor treatment efficacy is recommended. The purpose of this study was to examine shifts in equine parasite control program management practices via a short course presented by the Penn State Extension, and to highlight how data collected from these programs is useful for monitoring anthelmintic efficacy on a large scale. Horse owners were enrolled after participating in a short course and filled out questionnaire surveys about their parasite management programs pre and post study, horse information, and farm information. FECs were performed at three time points, and horses above a 300 strongyle eggs per gram cut-off were treated with pyrantel pamoate, fenbendazole, or ivermectin. Two weeks post-treatment, FECRTs were performed to determine treatment efficacy, which included 29 farms with 513 individual treatments. Prior to the study, only 30.6% of farms used FECs, but after the study, 97.3% of farms said they would use FECs in the future. Horses were given an average of 4.1 anthelmintic treatments per year before the study, and post study 89.2% of farms were able to reduce the number of anthelmintic treatments used. Fenbendazole was effective on zero farms, pyrantel pamoate on 7.4% of farms, and ivermectin on 92.9% of farms. This outreach project helped generate information about anthelmintic efficacy levels, causing a shift in practices on participating farms, and collected useful anthelmintic resistance data.

Diagnóstico de las infecciones por geohelmintos. Un problema sin resolver en la era de las ómicas / Diagnosis of soil-transmitted helminth infections. An unsolved problemin the omics era

Las infecciones producidas por Strongyloides stercoralis y otros geohelmintos, como las uncinarias (Necator americanus y Ancylostoma duodenale), representan un importante problema a nivel mundial, especialmente en áreas en vías de desarrollo. Clínicamente son difíciles de sospechar ya que producen cuadros inespecíficos y muchas veces solapados entre ellos. Asimismo, los largos períodos prepatentes que presentan dificultan la detección de las formas parasitarias. El diagnóstico microscópico continúa siendo la herramienta más utilizada en los laboratorios asistenciales, pero aún dista mucho de ser la herramienta ideal para detectarlos debido a su baja sensibilidad. Además, morfológicamente estos nematodos presentan similitudes importantes, por lo que el diagnóstico microbiológico aún es un reto. La serología ha permitido avanzar en cuanto al diagnóstico de la infección por S. stercoralis, pero esta opción no está disponible todavía para las uncinarias. Las técnicas de biología molecular han demostrado aumentar discretamente esta falta de sensibilidad, pero al igual que en otras infecciones parasitarias, actualmente no están disponibles para su uso en los laboratorios de microbiología clínica. Información sobre el suplemento: este artículo forma parte del suplemento titulado "Programa de Control de Calidad Externo SEIMC. Año 2016", que ha sido patrocinado por Roche, Vircell Microbiologists, Abbott Molecular y Francisco Soria Melguizo, S.A

Infections caused by Strongyloides stercoralis and other soil-transmitted worms such as hookworms (Necator americanus and Ancylostoma duodenale) represent a major problem worldwide, especially in developing areas. They are difficult to suspect clinically since they produce non-specific and often overlapping signs and symptoms. Likewise, their long prepatent periods hamper the detection of parasitic structures. Microscopic diagnosis is still the most commonly used tool in healthcare laboratories but it is still far from being the ideal technique to detect these infections due to its low sensitivity. In addition, these nematodes have strong morphologic similarities and consequently microbiological diagnosis remains a challenge. Serology has made progress in the diagnosis of S. stercoralis infection but this option is not yet available for hookworms. Molecular biology techniques have been shown to slightly increase this lack of sensitivity, but as with other parasitic infections, they are not currently available for use in clinical microbiology laboratories. Supplement information: This article is part of a supplement entitled "SEIMC External Quality Control Programme. Year 2016", which is sponsored by Roche, Vircell Microbiologists, Abbott Molecular and Francisco Soria Melguizo, S.A

Pharmacokinetics of Albendazole, Albendazole Sulfoxide, and Albendazole Sulfone Determined from Plasma, Blood, Dried-Blood Spots, and Mitra Samples of Hookworm-Infected Adolescents.

Albendazole is an effective anthelmintic intensively used for decades. However, profound pharmacokinetic (PK) characterization is missing in children, the population mostly affected by helminth infections. Blood microsampling would facilitate PK studies in pediatric populations but has not been applied to quantify albendazole's disposition. Quantification methods were developed and validated using liquid chromatography-tandem mass spectrometry to analyze albendazole and its metabolites albendazole sulfoxide and albendazole sulfone in wet samples (plasma and blood) and blood microsamples (dried-blood spots [DBS]; Mitra). The use of DBS was limited by a matrix effect and poor recovery, but the extraction efficiency was constant throughout the concentration range. Hookworm-infected adolescents were venous and capillary blood sampled posttreatment with 400 mg albendazole and 25 mg/kg oxantel pamoate. Similar half-life (t1/2 = ∼1.5 h), time to reach the maximum concentration (tmax = ∼2 h), and maximum concentration (Cmax = 12.5 to 26.5 ng/ml) of albendazole were observed in the four matrices. The metabolites reached Cmax after ∼4 h with a t1/2 of ca. 7 to 8 h. A statistically significant difference in albendazole sulfone's t1/2 as determined by using DBS and wet samples was detected. Cmax of albendazole sulfoxide (288 to 380 ng/ml) did not differ among the matrices, but higher Cmax of albendazole sulfone were obtained in the two microsampling devices (22 ng/ml) versus the wet matrices (14 ng/ml). In conclusion, time-concentration profiles and PK results of the four matrices were similar, and the direct comparison of the two microsampling devices indicates that Mitra extraction was more robust during validation and can be recommended for future albendazole PK studies.

Resistance to pyrantel embonate and efficacy of fenbendazole in Parascaris univalens on Swedish stud farms.

The aims of this study were to determine the species of Parascaris present in foals in Sweden and to establish whether anthelmintic resistance to pyrantel and fenbendazole is present on Swedish stud farms. Ascarid eggs collected from different regions in Sweden were karyotyped and were all identified as Parascaris univalens, characterized by one chromosomal pair. Faecal egg count reduction tests were performed on a total of 142 foals on 9 farms between September 2016 and May 2017. Healthy foals with at least 150 eggs per gram faeces (EPG) were included in the study and treated with oral pastes of pyrantel embonate or fenbendazole according to manufacturer instructions. The efficacy of the drugs was calculated by a Bayesian model using the R package "eggCounts". In accordance with the American Association of Equine Practitioners, parasites were classified as resistant to pyrantel if the reduction in EPG was ≤ 85% and to fenbendazole if the observed efficacy was ≤ 90%. Four of eleven groups treated with pyrantel had an observed efficacy of ≤ 85%, and as many as 43% of the foals treated with pyrantel excreted eggs 10-16 days after treatment. In contrast, one of the six groups treated with fenbendazole had an observed efficacy of ≤ 90%, and only 6% of all foals were excreting eggs 10-16 days after treatment. Since resistance to ivermectin has earlier been shown to be widespread in Parascaris spp. in Sweden it is likely that multiresistant populations are present on Swedish stud farms. This is the first study showing the existence of pyrantel-resistant Parascaris spp. in Europe, and the first ever study where anthelmintic resistance has been shown in P. univalens.

Off-target effects of tribendimidine, tribendimidine plus ivermectin, tribendimidine plus oxantel-pamoate, and albendazole plus oxantel-pamoate on the human gut microbiota.

Soil-transmitted helminths infect 1.5 billion people worldwide. Treatment with anthelminthics is the key intervention but interactions between anthelminthic agents and the gut microbiota have not yet been studied. In this study, the effects of four anthelminthic drugs and combinations (tribendimidine, tribendimidine plus ivermectin, tribendimidine plus oxantel-pamoate, and albendazole plus oxantel-pamoate) on the gut microbiota were assessed. From each hookworm infected adolescent, one stool sample was collected prior to treatment, 24 h post-treatment and 3 weeks post-treatment, and a total of 144 stool samples were analyzed. The gut bacterial composition was analyzed using 16S rRNA gene sequencing. Tribendimidine given alone or together with oxantel-pamoate, and the combination of albendazole and oxantel pamoate were not associated with any major changes in the taxonomic composition of the gut microbiota in this population, at both the short-term post-treatment (24 h) and long-term post-treatment (3 weeks) periods. A high abundance of the bacterial phylum Bacteroidetes was observed following administration of tribendimidine plus ivermectin 24 h after treatment, due predominantly to difference in abundance of the families Prevotellaceae and Candidatus homeothermaceae. This effect is transient and disappears three weeks after treatment. Higher abundance of Bacteroidetes predicts an increase in metabolic pathways involved in the synthesis of B vitamins. This study highlights a strong relationship between tribendimidine and ivermectin administration and the gut microbiota and additional studies assessing the functional aspects as well as potential health-associated outcomes of these interactions are required.

Efficacy and tolerability of triple drug therapy with albendazole, pyrantel pamoate, and oxantel pamoate compared with albendazole plus oxantel pamoate, pyrantel pamoate plus oxantel pamoate, and mebendazole plus pyrantel pamoate and oxantel pamoate against hookworm infections in school-aged children in Laos: a randomised, single-blind trial.

BACKGROUND: Albendazole and mebendazole are commonly used to control hookworm, but have shortcomings in their efficacy profiles. We assessed whether triple drug therapy (TDT) with albendazole, pyrantel pamoate, and oxantel pamoate was more effective than the co-administration of two drugs for the treatment of hookworm infections. METHODS: A randomised, single-blind trial was done from Sept 27 until Nov 17, 2017, in Laos. Children (6-15 years) from six schools were invited to participate. Hookworm-positive children were randomly assigned (2:2:1:1) by a computer stratified list (block sizes of six and 12) to TDT with albendazole (400 mg), pyrantel pamoate (20 mg/kg), and oxantel pamoate (20 mg/kg); albendazole plus oxantel pamoate; pyrantel pamoate plus oxantel pamoate; or mebendazole (500 mg) combined with both pyrantel pamoate and oxantel pamoate (used as proof of concept to compare the two TDTs). Two stool samples were collected at baseline and follow-up (17-30 days after treatment) and analysed with the Kato-Katz method. The primary outcome was the proportion of hookworm egg-negative children at follow-up in all Kato-Katz slides (cure rate [CR]) in the TDT with albendazole, pyrantel pamoate, and oxantel pamoate group compared with the albendazole plus oxantel pamoate and pyrantel pamoate plus oxantel pamoate groups. Secondary outcomes were tolerability 3 h and 24 h after treatment, egg reduction rates (ERRs) against hookworm, and efficacy against concomitant soil-transmitted helminth infections. Participating children and field and laboratory technicians were masked to treatment allocation. All children with follow-up data were included in the primary analysis. This trial is registered with ClinicalTrials.gov, number NCT03278431. FINDINGS: 1529 children were assessed for eligibility, of whom 533 provided complete baseline data and 414 provided complete outcome data. The CR was higher for the TDT albendazole, pyrantel pamoate, and oxantel pamoate (116 [84%] of 138) than with albendazole plus oxantel pamoate (73 [53%] of 138; odds ratio 4·7, 95% CI 2·7-8·3; p<0·0001) and pyrantel pamoate plus oxantel pamoate (36 [52%] of 69; 4·8, 2·5-9·3; p<0·0001). The geometric ERR of the TDT albendazole, pyrantel pamoate, and oxantel pamoate (99·9%) was higher than that for albendazole plus oxantel pamoate (99·0%; difference in ERR 0·9 percentage points, 95% CI 0·5-1·4), and pyrantel pamoate plus oxantel pamoate (99·2%; 0·7 percentage points, 0·3-1·3). Adverse events were reported by six (1%) children 3 h and none 24 h after treatment, without any difference across treatment groups. INTERPRETATION: TDT with albendazole, pyrantel pamoate, and oxantel pamoate could make a difference, in particular in the context of soil-transmitted helminth elimination. Pyrantel pamoate might be a useful alternative to prevent benzimidazole resistance; however, larger trials are needed to confirm this finding. FUNDING: Swiss National Science Foundation.

Longitudinal study for anthelmintic efficacy against intestinal helminths in naturally exposed Lithuanian village dogs: critical analysis of feasibility and limitations.

The efficacy of anthelmintic treatment at 1, 3, and 6 month intervals was evaluated in a prospective controlled field study with naturally exposed Lithuanian village dogs by monthly coproscopy during 1 year. A placebo-treated control group (C) (n = 202) and groups treated with two broad-spectrum anthelmintics, febantel/pyrantel-embonate/praziquantel (Drontal® Plus, Bayer) (D1, D3, D6; n = 113-117) and emodepside/praziquantel (Profender®, Bayer) (P1, P3, P6; n = 114-119), were included. At the beginning of the study, eggs of Toxocara canis (4.02%) and T. cati (0.44%) identified morphometrically and/or molecularly and eggs of taeniid- (0.78%) and Capillaria-like eggs (5.03%) were present in the feces without significant differences in prevalence between groups. Significant decreases in excretion of T. canis eggs was found 1 month after the treatment with Drontal® Plus in February (D1) and with Profender® in October (P1), November (P1), December (P3), February (P1), and March (P1, P3), as compared to controls in the same months. The incidence of egg excretion per dog at least once a year was significantly lower in group P1 for T. canis (4.24%; p < 0.01) and in groups D1, P1 for taeniid eggs (0%; p < 0.01 and p < 0.001), when compared to controls (16.96 and 6.70%, respectively). A critical analyses of factors possibly responsible for intestinal passage of canine helminth eggs revealed that chained dogs excreted T. canis eggs more frequently 1 month after treatment compared to dogs in pens, particularly from November to March (p = 0.01). The incidence of single detection of T. cati eggs was significantly increased in chained dogs (12.46%) as compared to fenced dogs (1.08%; p = 0.0001).

Combination deworming for the control of double-resistant cyathostomin parasites - short and long term consequences.

Equine cyathostomin are pervasive gastrointestinal parasites with wide-spread resistance to the benzimidazole and tetrahydropyrimidine drug classes worldwide. Combination deworming has been proposed as a more sustainable parasite control strategy. Simulation studies have found combination deworming to be effective in controlling drug resistant ovine trichostrongylid parasites. One equine study demonstrated an additive effect of a combination of oxibendazole and pyrantel pamoate against cyathostomins. However, this is the only equine study evaluating combination therapy, and the effects of repeated combination treatments administered over time remain unknown. The purpose of this study was to observe the efficacy of repeated oxibendazole/pyrantel pamoate combination therapy administered over one year against a cyathostomin population with resistance to benzimidazole and pyrantel products. Fecal egg counts were determined for the entire herd (N = 21) at the day of anthelmintic treatment and at two-week intervals for eight weeks post treatment. Starting efficacies of oxibendazole (OBZ, 10 mg/kg) and pyrantel pamoate (PYR, 6.6 mg base/kg) were 66.7% and 63.3%, respectively. Hereafter, the herd was treated four times with an oxibendazole/pyrantel pamoate combination, eight weeks apart, followed by repeating the single active treatments before concluding the study. While the first combination treatment exhibited an additive effect of the two active ingredients, this efficacy was not sustained over the course of the study. Mean fecal egg count reduction (FECR) was significantly greater for the first combination treatment (76.6%) than the second (42.6%, p = 0.0454), third (41.6%, p = 0.0318), and fourth (40.7%, p = 0.0372) combination treatments. The final single active mean FECRs were 42.3% for oxibendazole, and 42.7% for pyrantel pamoate. These efficacies were not significantly different from the initial single active efficacies (OBZ, p = 0.4421; PYR, p = 0.8361). These results suggest that combination therapy against double resistant equine cyathostomin populations is not sustainable, when using actives with markedly decreased starting efficacies.

Efficacy of nitazoxanide to treat natural Giardia infections in dogs.

BACKGROUND: Giardia parasites cause gastrointestinal disease in humans, dogs, and many other animals worldwide. The treatment of dogs for giardiasis requires further investigation to ascertain levels of drug efficacy and the possibility of adverse side effects. Nitazoxanide (NTZ) has shown good clinical anti-Giardia activity in humans, yet it has not been evaluated for the treatment of giardiasis in dogs. METHODS: Thirty-five dogs, naturally infected with Giardia were divided into five groups (n = 7): dogs in group NTZ1, NTZ2, and NTZ3 were treated with a single oral dose of 37.5 mg/kg, 75 mg/kg, and 150 mg/kg, respectively, of NTZ on days 0 and 14. The fourth group was treated with a commercially available regimen that includes a combination of pyrantel, praziquantel, and febantel (FEB) administered orally for three consecutive days. Additionally, an untreated control group was established. Giardia cysts from the stool of each dog were quantified on days -3, 0, 5, 7, 9, 11, 14, 18, 25, and 28. Biochemical parameters were evaluated in all dogs, before the first treatment and after concluding the experiment. RESULTS: Shedding of Giardia cysts was reduced in all treated groups when compared to untreated controls (P < 0.01). However, NTZ2, NTZ3, and FEB had a lower risk during the study. Furthermore, NTZ was also effective against another protozoan, Cryptosporidium spp. at doses of 75 mg/kg and 150 mg/kg, in contrast to the combination of febantel + pyrantel + praziquantel. Biochemical parameters of treated animals, namely, aspartate transaminase and alanine transaminase enzymes, remained within physiological ranges. CONCLUSIONS: Based on these results, the implementation of NTZ as a treatment for giardiasis in dogs is proposed. The administration of a single dose is an important advantage of NTZ because it reduces workload, particularly in animals placed in shelters and kennels, where handling of large numbers of animals is required, and personnel is frequently scarce.