Isoxazolinas no tratamento da demodicidose canina ­ Revisão de literatura / Isoxazolines in the treatment of canine demodicosis ­ literature review / Isoxazolinas en el tratamiento de la demodicosis canina ­ revisión de la literatura

A demodicidose canina é uma dermatopatia parasitária inflamatória comum na rotina clínica. Ela é causada pela proliferação exacerbada do ácaro Demodex spp., e a espécie mais frequentemente encontrada e que causa a doença clínica é o Demodex canis. A doença pode ser classificada conforme a distribuição das lesões e a idade em que elas surgem. Os sinais clínicos mais comuns incluem alopecia, eritema, hiperpigmentação e descamação, e o diagnóstico mais preconizado é o exame parasitológico do raspado cutâneo. Diversos protocolos terapêuticos para a demodicidose canina têm sido estudados, e por muito tempo utilizou-se o amitraz, sendo ao longo dos anos substituído por fármacos da classe das lactonas macrocíclicas, pela praticidade de sua administração. Contudo, mais recentemente, as isoxazolinas (fluralaner, afoxolaner e sarolaner) foram descobertas como miticidas, e nos últimos anos têm demonstrado excelentes resultados. O presente trabalho tem como objetivo realizar uma revisão de literatura sobre as isoxazolinas no tratamento da demodicidose canina.(AU)

Canine demodicosis is an inflammatory parasitic skin disease common in clinical routine. It is caused by the exacerbated proliferation of the Demodex spp., and the most frequently encountered species that causes clinical disease is Demodex canis. The disease can be classified according to the distribution of lesions and the age at which they appear. The most common clinical signs include alopecia, erythema, hyperpigmentation and desquamation, and the most recommended diagnosis is the parasitological examination of the skin scraping. Several therapeutic protocols for canine demodicosis have been studied, and for a long time the main therapeutic of this disease was amitraz, being replaced over the years by drugs of the macrocyclic lactone class due to the practicality of its administration. However, more recently the isoxazolines (fluralaner, afoxolaner and sarolaner) were discovered as miticides, and in recent years they have shown excellent efficacy results, coming to revolutionize the therapy of canine demodicosis. The present study aims to review the literature on isoxazolines in the treatment of canine demodicosis.(AU)

La demodicosis canina es una enfermedad inflamatoria parasitaria de la piel común en la rutina clínica. Es causada por la proliferación exacerbada de Demodex spp., y la especie más frecuente que causa enfermedad clínica es Demodex canis. La enfermedad se puede clasificar según la distribución de las lesiones y la edad en que aparecen. Los signos clínicos más frecuentes incluyen alopecia, eritema, hiperpigmentación y descamación, y el diagnóstico más recomendado es el examen parasitológico del raspado cutáneo. Se han estudiado varios protocolos terapéuticos para la demodicosis canina, y durante mucho tiempo la principal terapéutica de esta enfermedad fue el amitraz, siendo reemplazada con el paso de los años por fármacos de la clase de las lactonas macrocíclicas debido a la practicidad de su administración. Sin embargo, más recientemente se descubrieron las isoxazolinas (fluralaner, afoxolaner y sarolaner) como acaricidas, y en los últimos años han mostrado excelentes resultados de eficacia, llegando a revolucionar la terapia de la demodicosis canina. El presente estudio tiene como objetivo revisar la literatura sobre las isoxazolinas en el tratamiento de la demodicosis canina.(AU)

Albendazole is effective for controlling monogenean parasites of the gills of Piaractus brachypomus (Serrasalmidae) and Megaleporinus macrocephalus (Anostomidae) / Albendazol é eficaz no controle de parasitos monogenéticos das brânquias de Piaractus brachypomus (Serrasalmidae) e Megaleporinus macrocephalus (Anostomidae)

Monogenean infestations can cause high mortality in farmed fish and therefore significant economic losses. The present study investigated the efficacy of albendazole in therapeutic baths against monogeneans of Piaractus brachypomus Cuvier, 1818 and Megaleporinus macrocephalus (Garavello & Britski, 1988). For both fish, a 24 hours therapeutic bath with albendazole concentrations of 150, 300 and 500 mg/L were tested against monogeneans from the gills. The baths had an efficacy from 61.4 ± 32.9 (95%CI=64.5) against monogeneans of P. brachypomus, and from 95.4 ± 5.6 (95%CI=10.9) against monogeneans of M. macrocephalus. In P. brachypomus, the hepatosomatic index (HSI) in fish exposed to 150 mg/L of albendazole was higher than in fish exposed to 300 mg/L. The splenosomatic index (SSI) values in fish exposed to 150 mg/L of albendazole were lower than in fish exposed to 300 mg/L. In M. macrocephalus, the HSI and SSI values decreased in treatments with 150, 300 and 500 mg/L of albendazole to control and treat infestations by monogeneans. For M. macrocephalus, 150 mg/L of albendazole can be used to control and treat infestations by monogeneans, while for P. brachypomus 500 mg/L of albendazole can be used in a 24 hours bath.(AU)

Infestações por monogenéticos podem causar alta mortalidade entre os peixes cultivados e, portanto, perdas econômicas significativas. O presente estudo investigou a eficácia do albendazol em banhos terapêuticos contra monogenéticos de Piaractus brachypomus Cuvier, 1818 e Megaleporinus macrocephalus (Garavello & Britski, 1988). Para ambos os peixes, um banho terapêutico de 24 horas com concentrações de albendazol de 150, 300 e 500 mg/L, foi testado contra monogenéticos nas brânquias. Os banhos tiveram eficácia 61,4 ± 32,9 (IC95%=64,5) contra monogenéticos de P. brachypomus, e de 95,4 ± 5.6 (IC95%=10.9) contra monogenéticos de M. macrocephalus. Em P. brachypomus, o índice hepatossomático (IHS) em peixes expostos a 150 mg/L de albendazol foi maior do que em peixes expostos a 300 mg/L. Os valores do índice esplenossomático (IES) em peixes expostos a 150 mg/L de albendazol foram menores do que em peixes expostos a 300 mg/L. Em M. macrocephalus, os valores de IHS e IES diminuíram nos tratamentos com 150, 300 e 500 mg/L de albendazol, para controlar e tratar infestações por monogenéticos. Para M. macrocephalus, 150 mg/L de albendazol pode ser usado para controlar e tratar infestações por monogenéticos, enquanto para P. brachypomus, 500 mg/L de albendazol pode ser usado em um banho de 24 horas.(AU)

Importation of cats and risk of parasite spread: a Caribbean perspective and case study from St Kitts.

BACKGROUND: In more recent years, international travel with cats has increased. The distribution of cat parasites can change with this movement. Already, subtropical and tropical parasites have been reported by veterinarians in areas where they are not naturally present. Understanding the prevalence of tropical and subtropical parasites in Caribbean islands and the risk of importation to temperate areas could enable improved prevention recommendations and border control import requirements. METHODS: We present a study focused on cat owning students enrolled in a Doctor of Veterinary Medicine (DVM) programme on St Kitts. Owners were interviewed about their cats and their use of parasiticides. Cats were examined for Trichuris felis and Platynosomum fastosum using sugar flotation, Lynxacarus radovskyi using an adhesive tape test, and Dirofilaria immitis using commercial antigen and antibody tests. RESULTS: Data on 115 cats owned by 87 DVM students were collected and 90 cats, all expected to travel to the USA, were examined. Most of the cats were adults and born in St Kitts. Prevalence was reported as 6.8% (95% confidence interval (CI): 2.2-15.1%) for T. felis, 16.2% (95% CI: 8.7-26.6%) for P. fastosum and 6.8% (95% CI: 2.5-14.3%) for L. radovskyi. All D. immitis tests were negative. DVM students reported a high level of deworming (83.3% of the cats), but the number of cats treated per recommendations were low (56.1% for endoparasites and 70.8% for ectoparasites). Also, there was a lack of clarity regarding the purpose of the treatments used and treatments did not appear to be targeted for the parasites present. CONCLUSION: Our results indicate a low prevalence of the parasites of interest in the DVM student cat population compared to other prevalence studies from the Caribbean. However, a degree of non-compliance with parasiticide uses and the high number of cats traveling to the USA indicate a medium risk of importation of tropical and subtropical cat parasites to temperate areas. We recommend stronger health inspections and health screening requirements at the borders including the development of specific parasiticide protocols for cat importation.

Moxidectin residues in tissues of lambs submitted to three endoparasite control programs.

The indiscriminate and continuous use of anthelmintic drugs has promoted the selection of resistant parasites population, the presence of drug residues in food products, and heavy environmental contamination. The aim of the present study was to determine the presence of antiparasitic drug residues in 42-days old lamb serum and tissues, submitted to three endoparasite control programs: preventive treatment (PT) using moxidectin (MOX) at every 28days; selective treatment (FEC) using MOX when fecal egg count was greater than or equal to 700; and selective treatment (FMC), using MOX when FAMACHA/FMC score was 3 and above. For this purpose, MOX residues were quantified in serum, muscle, fat, liver and kidney. Lambs were slaughtered when reaching 30kg of body weight, and after a 28-day MOX withdrawal period. Before slaughter, blood was collected to determine the concentration of MOX in serum. Tissues and organ samples were collected at slaughter. The quantitation of MOX residues was performed using liquid chromatography tandem mass spectrometry (LC-MS/MS). From the 756 tissue samples analyzed, only one sample of fat from the PT group showed residue levels (586.3µg/kg) above the maximum residue limit (MRL) of 500µg/kg. No treated lambs presented traces of MOX residues in fat and liver, suggesting possible environmental contamination. In conclusion, all weaned lambs, produced in continuous grazing and subjected to gastrointestinal parasite control programs via selective (FEC and FMC) or preventive (PT) treatment, displayed a low risk (<1%) of MOX residues above the MRL in muscle, fat, kidney, and liver.

FAMACHA© system assessment by previously trained sheep and goat farmers in Brazil.

The aim of this study was to evaluate the degree of adoption and the correct use of the FAMACHA© system amongst sheep and goat farmers trained in a previous hands-on course. A survey was carried out with 1375 people who received FAMACHA© training from July 2009 to May 2011 in Paraná State, Brazil. The survey was conducted from March 2012 to May 2013. Firstly, a questionnaire was applied with specific questions for farmers about their anthelmintic (AH) treatment practices before and after the FAMACHA© training. In a second step, eight of the questionnaire respondents classified as sheep or goat farmers were contacted for an in loco visit during which the application of the FAMACHA© system was evaluated in the respective farms and blood samples were collected from 20 animals to calculate sensitivity and specificity. A total of 124 farmers responded the questionnaire (9% of project participants). Farmers accounted for 48.4% of total responses. Half of these farmers (51.6%) reported losses related to parasites in their property before the training. Antiparasitic treatments, at fixed intervals, were responsible for 93.1% of deworming practices before the training project. FAMACHA© was unknown for 51.7% of the respondents, and 31% knew the chart, but did not use it. After the project, 69% had adopted the system and 83% assessed the animals at regular intervals. However, 18.9% did not evaluate all animals. During the in loco visits, problems reported included the incorrect exposure of the ocular mucosa (50% of farmers) and not using the chart (87.5%). Also, 62.5% did not keep records of the FAMACHA© assessment history of the flock. However, sensitivity was 100%, with 0% false negatives. We conclude that, amongst farmers who adopted the system, despite some methodological errors regarding its use, the objectives were met in terms of reducing the number of anthelmintic treatments and providing anemic animals with AH treatment. Trained farmers seemed to require technical guidance post-training to promote effective use of the FAMACHA© system.

Weight gain and control of endo- and ectoparasites of beef heifers treated with allopathic, herbal and homeopathic drugs / Ganho de peso e controle de endo e ectoparasitas de novilhas de corte tratadas com medicamentos alopáticos, fitoterápicos e homeopáticos

The aim of this study was to evaluate the efficacy of herbal, homeopathic and allopathic treatments for parasites in beef heifers during two experimental cycles of 318 and 313 days. Treatments: NC - negative control (untreated); HH - treated with homeopathic preparation Homeo bovis Parasitário®; PC - (positive control) - treated with 10% moxidectina® and an acaricide formulation of cypermethrin, chlorpyrifos and piperonyl butoxide®; HF ­ treated with homeopathic preparation Fator C&MC®; and FN - treated with neem cake (torta de neem®) and with neem oil (óleo de neem®). Parasite egg count (EPG), horn fly (Haematobia irritans) and tick (Rhipicephalus (Boophilus) microplus) assessment and animal weighting were performed at 28-day intervals. Blood samples were collected at the first cycle to assess the immune response. Horn fly infestation was not affected by any treatment (P>0.05). The mean number of ticks, which was low in both cycles, was lower (P<0.05) in the first cycle in animals that received PC treatment. In both experimental cycles, the mean EPG of the PC-treated animals was lower (P<0.05) than the animals receiving other treatments. Treatments had no effect on the immune response (P>0.05). The animals treated with allopathic drugs were 22 to 30 kg heavier (P<0.05) than untreated animals or animals treated with alternative drugs.

O objetivo do trabalho foi avaliar a eficácia de tratamentos fitoterápicos, homeopáticos e alopáticos contra ecto e endoparasitas na recria de novilhas, em dois ciclos experimentais subsequentes de 318 e 313 dias. Tratamentos: CN - controle negativo - não tratado; tratamento HH - tratado com homeopático Homeo bovis Parasitário®; tratamento CP ­ controle positivo ­ tratado com moxidectina 10%® e uma formulação acaricida contendo cypermetrina, clorpirifós e butóxido de piperonila®; tratamento HF - tratado com homeopático Fator C&MC® e tratamento FN - tratados com torta de neem® e com óleo de neem®. A contagem de ovos nas fezes (OPG), a infestação por Haematobia irritans, Rhipicephalus (Boophilus) microplus e pesagem dos animais foram realizadas em intervalos de 28 dias. No primeiro ciclo foi coletado sangue para avaliar a resposta imume. A infestação por mosca-dos-chifres não foi influenciada por nenhum dos tratamentos (P>0,05). Nos dois ciclos o número médio de carrapatos foi baixo e apenas no primeiro foi menor (P>0.05) no tratamento CP em relação aos demais. A média de OPG no tratamento CP foi mais baixa que nos demais tratamentos nos dois ciclos experimentais (P<0,05). Não houve efeito de tratamentos na resposta imune. Os animais do tratamento CP ganharam entre 22 a 30 kg de peso vivo a mais (P<0,05) que os não tratados ou tratados com medicamentos alternativos.

Weight gain and control of endo- and ectoparasites of beef heifers treated with allopathic, herbal and homeopathic drugs.

UNLABELLED: The aim of this study was to evaluate the efficacy of herbal, homeopathic and allopathic treatments for parasites in beef heifers during two experimental cycles of 318 and 313 days. TREATMENTS: NC - negative control (untreated); HH - treated with homeopathic preparation Homeo bovis Parasitário®; PC - (positive control) - treated with 10% moxidectina® and an acaricide formulation of cypermethrin, chlorpyrifos and piperonyl butoxide®; HF - treated with homeopathic preparation Fator C&MC®; and FN - treated with neem cake (torta de neem®) and with neem oil (óleo de neem®). Parasite egg count (EPG), horn fly (Haematobia irritans) and tick (Rhipicephalus (Boophilus) microplus) assessment and animal weighting were performed at 28-day intervals. Blood samples were collected at the first cycle to assess the immune response. Horn fly infestation was not affected by any treatment (P>0.05). The mean number of ticks, which was low in both cycles, was lower (P<0.05) in the first cycle in animals that received PC treatment. In both experimental cycles, the mean EPG of the PC-treated animals was lower (P<0.05) than the animals receiving other treatments. TREATMENTS had no effect on the immune response (P>0.05). The animals treated with allopathic drugs were 22 to 30 kg heavier (P<0.05) than untreated animals or animals treated with alternative drugs.

Parasite control in the age of drug resistance and changing agricultural practices.

The benefits of using antiparasitic drugs in farm animals are unquestionable. However, despite anthelmintic use as the predominant control strategy, extreme parasite infection cases are appearing in sheep and goat production; these impact productivity and have show mortality rates reaching pre-drug use levels. This was a predictable situation resulting from the loss of efficacy by all available products, particularly when some products were used as the sole intervention. The concepts of agroecology and holistic agriculture, which advocate the use of integrated management strategies, such as target selected treatment, herbal medicine, and the application of other parasite control alternatives, are not completely new, but are undergoing a resurgence because of their more sustainable appeal. The objective of this review article is to examine the problem of parasite control in the face of parasite drug resistance and to outline some strategies that may be used in parasite control programmes. Before they are accepted and recommended by the WAAVP, agroecological methods such as those listed above and described in detail herein should be validated based on scientific evidence of their efficacy for parasite control and should be tested for both host and environmental safety.

Effects of faecal residues of moxidectin and doramectin on the activity of arthropods in cattle dung.

Dung invertebrate colonization and degradation levels of faeces from cattle treated with endectocides were studied. Faeces of control and doramectin (DRM) (subcutaneous) and moxidectin (MXD) (subcutaneous and topical) treated animals were deposited on the field from 3 to 21 days post-treatment (pt). Pats were recovered after 6 to 42 days post-deposition (pd). Faecal weight, dry matter, arthropods number, and drugs concentrations were determined. Total arthropods number was higher in control (P<0.0001) than in the other groups from days 3 to 21 pt. Total number of insects recovered on days 3, 11, and 21 pt from control pats was significantly (P<0.001) higher than in treated-animal pats during all the trial. At day 21 pt, the insects' number in dung voided by DRM-treated cattle was (P<0.05) lower than in the other groups. Comparisons of dung degradation among treatments were inconclusive. A lower adverse effect was observed for MXD compared with DRM. No significant degradation of MXD or DRM was observed during the present trial.

Potencial anti-helmíntico da raiz de Solanum paniculatum Linnaeus (1762) em ovelhas do semi-árido paraibano / Anthelmintic potencial of Solanum paniculatum Linnaeus (1762) root for sheep from semi-arid of Paraíba state, Brazil

Objetivou-se avaliar a atividade anti-helmíntica da planta Solanum paniculatum Linnaeus (1762), Jurubeba, bem como sua associação com Operculina hamiltonii (G.DON) D.F. Austin & Staples (1983), Batata de purga, em ovelhas Santa Inês, naturalmente infectadas no semi-árido paraibano. Foram utilizadas 24 fêmeas distribuídas em quatro grupos de seis animais: Grupo 1, controle positivo, tratado com Albendazole 10%; Grupo 2, tratado com o Farelo da raiz da Jurubeba (FRJ); Grupo 3, tratado com o Farelo da raiz da Jurubeba associado ao Farelo da raiz da Batata de purga (FRJ e FRB); Grupo 4, controle negativo que recebeu como tratamento água destilada. As coletas de fezes foram realizadas no dia zero e sete, 14, 21 e 28 dias pós-tratamentos. A contagem do número de ovos por grama de fezes (OPG) foi obtida pela técnica de Gordon & Whitlock (1939). A avaliação da eficácia dos tratamentos foi realizada pelo teste de redução na contagem de ovos fecais (RCOF). As coproculturas foram realizadas de acordo com a metodologia descrita por Robert's & O'Sullivan (1950). A RCOF dos tratamentos para os dias sete, 14, 21 e 28, foi respectivamente: 52,3%, 81,32%, 72,79% e 66,73% para o Albendazole; 31,22%, 30,37%, 58,58% e 72,28% para o FRJ; e 35,04%, 57,84%, 76,93% e 87,06% para o FRJ e FRB. O Haemonchus sp. foi o gênero mais prevalente nas coproculturas pós-tratamentos.

The objective was to evaluate the anthelmintic action of Solanum paniculatum Linnaeus (1762), "Jurubeba", and its association with Operculina hamiltonii (G.DON) D.F. Austin & Staples (1983), "Batata de purge", in Santa Inês sheep naturally infected from semi-arid of Paraíba state, Brazil. Were used 24 females divided in four groups of six animals: Group 1, positive control, treated with Albendazol 10%; Group 2, treated with the root bran of Jurubeba (FRJ); Group 3, treated with the root bran of Jurubeba associated with the root bran of Batata de purga (FRJ and FRB); Group 4, negative control that received distilled water as treatment. The collections of feces were realized on day zero and seven, 14, 21 and 28 days after treatments. Egg counts in feces were obtained by the technique of Gordon & Whitlock (1939). The effectiveness evaluation of the treatments was realized by the test of reduction on the counting of fecal eggs (RCOF). The larvae cultures were realized according to the methodology described by Robert's & O'Sullivan (1950). RCOF of the treatments to the days seven, 14, 21 and 28 was respectively: 52,3%, 81,32%, 72,79% and 66,73% to Albendazol; 31,22%, 30,37%, 58,58% and 72,28% to the FRJ; and 35,04%, 57,84%, 76,93% and 87,06% to the FRJ and FRB. Haemonchus sp. was the most prevalent gender on the larvae cultures after treatments.

Strategies for the elimination of taeniasis/cysticercosis.

Advances in the field of neurocysticercosis continue to shape our understanding of the disease and our efforts to control it. Several attempts have been made to eradicate the disease with active interventions such as changing domestic pig-raising practices, mass chemotherapy of porcine cysticercosis and taeniasis, selective detection and treatment of taeniasis, and community health education. Moreover, ongoing progress in the diagnosis of taeniasis and the development of a porcine vaccine against cysticercosis in Australia, Mexico and Peru has yielded at least one effective vaccine that is currently available. Thus far, however, attempted interventions have only been successful in temporarily disrupting transmission of the disease. Controlled data on the efficacy and acceptability of the different interventions is urgently needed to provide a base-line schematic for intervention which could later be tailored to each particular endemic scenario.

Efecto del toltrazuril al 2.5% durante el periodo prepatente de la sarcocistiosis intestinal canina / Effect of toltrazuril 2.5% during the prepatent period of canine sarcocystiosis

El objetivo del estudio fue determinar el efecto del toltrazuril al 2.5% en dosis única para el tratamiento de la sarcocistiosis intestinal de perros infectados experimentalmente con Sarcocystis lamacanis. Se utilizaron 24 cachorros cruzados de ambos sexos, de 2.5 meses de edad, previamente desparasitados y alimentados con dieta libre de carne cruda. Los perros fueron infectados con cerca de 95,000 quistes de S. lamacanis, presentes en 100 g de músculo cardiaco de alpaca. Se les distribuyó en un grupo control no tratado de 4 cachorros y cuatro grupos de 5 animales c/u tratados con toltrazuril al 2.5% en dosis única de 10 ó 20 mg/kg de peso vivo, administrado oralmente al 5º ó 7º día post-infección. Las muestras fecales fueron recolectadas diariamente, a partir del 10º día post-infección y por 11 días. Se analizó las heces por el método de concentración por flotación con solución Sheather para determinar la presencia de esporoquistes, y las muestras positivas se analizaron con el método de Stoll modificado para determinar el número de esporoquistes por gramo de heces. El toltrazuril no logró controlar la infección por S. lamacanis en caninos en ninguno de sus tratamientos.

The aim of the study was to determine the effect of toltrazuril (2.5%) in a single dose for the treatment of canine sarcocystiosis. Twenty-four crossbred puppies, both sexes, 2.5 months of age, were used. All puppies were dewormed prior to the study and fed throughout the study with a diet free of raw meat. Animals were experimentally infected with nearly 95,000 cysts of S. lamacanis, contained in 100 g of alpaca heart, and distributed in a control (untreated) group of 4 puppies and 4 groups of 5 puppies each which were treated with toltrazuril (2.5%) with a single dose of 10 or 20 mg/kg body weight on day 5 or 7 post-infection. Fecal samples were daily collected during 11 days and starting on day 10 post-infection. Feces was analyzed by the flotation method with the Sheather solution to determine the presence of sporocysts of Sarcocystis sp. and positive samples were analyzed by the modified Stoll method to determine the number of sporocysts per gram of feces. The toltrazuril did not control the infection of S. lamacanis in none of the treated groups.

Pharmacological approaches towards rationalizing the use of endoparasitic drugs in small animals.

Parasitic diseases are an important health concern to small animal veterinarians worldwide, and their zoonotic potential is also of relevance to human medicine. The treatment and control of such conditions relies heavily on pharmaceutical intervention using a range of antiparasitic drugs and/or their biologically active metabolites. Broad spectrum agents have been produced, although narrow and even monospecific drugs are used in some situations. Their efficacy may depend on dosage, the target pathogen(s), the host species and/or the site of infection. Optimal use of antiparasitics requires a detailed consideration of the pharmacokinetic and pharmacodynamic properties of the drugs in specific clinical contexts. This review summarizes the present status of knowledge on the metabolism, and physicochemical and pharmacological properties of the major antiparasitic drugs currently used in small animal veterinary practice. In addition, data relevant to therapeutic dosage, efficacy and clinical indication/contraindication, particularly in relation to combination drug therapy, are included.

Doramectin concentration profiles in the gastrointestinal tract of topically-treated calves: Influence of animal licking restriction.

Endectocide compounds are extensively used for broad-spectrum parasite control and their topical administration to cattle is widespread in clinical practice. Pour-on formulations of moxidectin, ivermectin, eprinomectin and doramectin (DRM) are marketed internationally for use in cattle. However, variability in antiparasitic efficacy and pharmacokinetic profiles has been observed. Although the tissue distribution pattern for different endectocide molecules given subcutaneously to cattle has been described, only limited information on drug concentration profiles in tissues of parasite location after topical treatment is available. Understanding the plasma and target tissue kinetics for topically-administered endectocide compounds is relevant to optimise their therapeutic potential. The current work was designed to measure the plasma and gastrointestinal (GI) concentration profiles of DRM following its pour-on administration to calves. The influence of natural licking behaviour of cattle on DRM concentration in mucosal tissue and luminal content of different GI sections was evaluated. The trial was conducted in two experimental phases. In Phase I, the DRM plasma kinetics was comparatively characterised in free-licking and in 2-day licking-restricted (non-licking) calves. The pattern of distribution of topical DRM to mucosal and luminal contents from abomasum, duodenum, ileum, caecum and spiral colon was assessed in free-licking and non-licking calves restricted over 10 days post-administration (Phase II). The prevention of licking caused marked changes on the plasma and GI kinetics of DRM administered pour-on. In 2-day licking restricted calves, DRM systemic availability was significantly lower (29%) than in free licking animals during the first 9 days post-treatment. Following a 10-day long licking restriction period, DRM concentrations profiles in both mucosal tissue and luminal contents of the GI tract were markedly higher in animals allowed to lick freely. This enhancement in drug concentrations in free-licking compared to non-licking calves, was particularly pronounced in the abomasal (38-fold higher) and duodenal (six-fold higher) luminal content. As shown earlier for ivermectin, licking behaviour may facilitate the oral ingestion of topically-administered DRM in cattle. This would be consistent with the marked lower drug concentration profiles measured in the bloodstream and GI tract of the animals prevented from licking. The work reported here provides relevant information on the pattern of DRM distribution to the GI tract after pour-on treatment, and contributes to understand the variability observed in the antiparasitic persistence of topically-administered endectocides in cattle. The implications of natural licking in topical treatments are required to be seriously assessed to achieve optimal parasite control and to design parasitological and pharmacological studies within the drug approval process.