In vitro susceptibility of nematophagous fungi to antiparasitic drugs: interactions and implications for biological control

Abstract The fast anthelmintic resistance development has shown a limited efficiency in the control of animals endoparasitosis and has promoted research using alternative control methods. The use of chemicals in animal anthelmintic treatment, in association with nematophagous fungi used for biological control, is a strategy that has proven to be effective in reducing the nematode population density in farm animals. This study aims to verify the in vitro susceptibility of the nematophagous fungi Arthrobotrys oligospora, Duddingtonia flagrans and Paecilomyces lilacinus against the antiparasitic drugs albendazole, thiabendazole, ivermectin, levamisole and closantel by using the Minimum Inhibitory Concentration (MIC). MICs ranged between 4.0 and 0.031 µg/mL for albendazole, thiabendazole and ivermectin, between 0.937 and 0.117 µg/mL for levamisole, and between 0.625 and 0.034 µg/mL for closantel. The results showed that all antiparasitic drugs had an in vitro inhibitory effect on nematophagous fungi, which could compromise their action as agents of biological control. D. flagrans was the most susceptible species to all drugs.

Resumo O desenvolvimento rápido da resistência anti-helmíntica demonstrou a eficiência limitada no controle de endoparasitoses em animais, e promoveu a investigação em métodos de controles alternativos. O uso de produtos químicos no tratamento anti-helmíntico animal, em associação com fungos nematófagos utilizados para o controlo biológico, é uma estratégia que tem provado ser eficaz na redução da densidade da população de nematódeos em animais agrícolas. Este estudo teve como objetivo verificar a suscetibilidade in vitro dos fungos nematófagos Arthrobotrys oligospora, Duddingtonia flagrans e Paecilomyces lilacinus frente aos antiparasitários albendazol, tiabendazol, ivermectina, levamisol e closantel, usando a concentração inibitória mínima (MIC). Os MICs variaram entre 4,0 e 0,031 g/mL para albendazol, tiabendazol e ivermectina, entre 0,937 e 0,117 g/mL para o levamisol, e entre 0,625 e 0,034 g/mL para closantel. Os resultados mostraram que todos os antiparasitários tiveram um efeito inibidor in vitro sobre os fungos nematófagos, o que poderia comprometer suas atividades como agentes de controle biológico. D. flagrans foi a espécie mais sensível a todas as drogas.

In vitro susceptibility of nematophagous fungi to antiparasitic drugs: interactions and implications for biological control

Abstract The fast anthelmintic resistance development has shown a limited efficiency in the control of animals endoparasitosis and has promoted research using alternative control methods. The use of chemicals in animal anthelmintic treatment, in association with nematophagous fungi used for biological control, is a strategy that has proven to be effective in reducing the nematode population density in farm animals. This study aims to verify the in vitro susceptibility of the nematophagous fungi Arthrobotrys oligospora, Duddingtonia flagrans and Paecilomyces lilacinus against the antiparasitic drugs albendazole, thiabendazole, ivermectin, levamisole and closantel by using the Minimum Inhibitory Concentration (MIC). MICs ranged between 4.0 and 0.031 µg/mL for albendazole, thiabendazole and ivermectin, between 0.937 and 0.117 µg/mL for levamisole, and between 0.625 and 0.034 µg/mL for closantel. The results showed that all antiparasitic drugs had an in vitro inhibitory effect on nematophagous fungi, which could compromise their action as agents of biological control. D. flagrans was the most susceptible species to all drugs.

Resumo O desenvolvimento rápido da resistência anti-helmíntica demonstrou a eficiência limitada no controle de endoparasitoses em animais, e promoveu a investigação em métodos de controles alternativos. O uso de produtos químicos no tratamento anti-helmíntico animal, em associação com fungos nematófagos utilizados para o controlo biológico, é uma estratégia que tem provado ser eficaz na redução da densidade da população de nematódeos em animais agrícolas. Este estudo teve como objetivo verificar a suscetibilidade in vitro dos fungos nematófagos Arthrobotrys oligospora, Duddingtonia flagrans e Paecilomyces lilacinus frente aos antiparasitários albendazol, tiabendazol, ivermectina, levamisol e closantel, usando a concentração inibitória mínima (MIC). Os MICs variaram entre 4,0 e 0,031 g/mL para albendazol, tiabendazol e ivermectina, entre 0,937 e 0,117 g/mL para o levamisol, e entre 0,625 e 0,034 g/mL para closantel. Os resultados mostraram que todos os antiparasitários tiveram um efeito inibidor in vitro sobre os fungos nematófagos, o que poderia comprometer suas atividades como agentes de controle biológico. D. flagrans foi a espécie mais sensível a todas as drogas.

Accidental and experimental Closantel intoxication in Uruguayan sheep / Intoxicação acidental e experimental por Closantel em ovinos no Uruguai

An outbreak of Closantel intoxication in sheep in Uruguay is described. The outbreak occurred in a group of 1300 weaning lambs treated orally with a 10% solution of Closantel. One hundred forty eight lambs showed clinical signs of intoxication and 14 died. The clinical signs included mydriasis, nystagmus, and negative pupillary reflex, bilateral blindness, bump into objects, and lateral movement of the head. No macroscopic lesions were observed. The histological lesions of the retina were cytoplasmic vacuolization in ganglion cells and in cells of the inner and outer nuclear layers with different degrees of atrophy. Vacuolization and axonal degeneration were observed in the optic nerve, with multifocal areas of fibrosis and infiltration by lymphocytes and Gitter cells. To reproduce the intoxication, four sheep were given two, four and 10 times the therapeutic dose of Closantel (0.1g/kg of BW). Only the animals receiving 10 times the recommended dose showed clinical signs. The histological examination of the lesions in experimental sheep showed similar results to those described in the accidental outbreak, except for the absence of optic nerve fibrosis and inflammation, characterizing an acute phase. Axonal myelin sheaths loss, fibroblasts and collagen fibers were observed in the ultrastructural study of the optic nerve of accidental intoxicated animals. The optic nerve of experimentally intoxicated animals had vacuoles that separated the myelin sheaths of axons. To prevent outbreaks it is suggested to weigh the animals before Closantel administration to avoid errors in dose calculation.(AU)

Descreve-se um surto de intoxicação por Closantel em ovinos no Uruguai. O surto ocorreu em um lote de 1300 cordeiros que foram dosados com uma solução de Closantel 10%, por via oral. Do total, 148 apresentaram sinais clínicos de intoxicação e 14 morreram. Os sinais clínicos incluíam midríase, nistagmo, reflexo pupilar negativo, cegueira bilateral, pressão da cabeça contra objetos e desvio lateral da cabeça. Lesões macroscópicas não foram observadas. Histologicamente havia vacuolização citoplasmática das células ganglionares e nas células das camadas nuclear interna e externa. Na retina havia, também, diferentes graus de atrofia. Vacuolização e degeneração axonal foram observados no nervo óptico, com áreas multifocais de fibrose e infiltrado de linfócitos e células Gitter. Quatro ovinos receberam experimentalmente duas, quatro e 10 vezes a dose terapêutica de Closantel (0,1 g/kg de peso vivo). Apenas os animais que receberam 10 vezes a dose recomendada apresentaram sinais clínicos. O exame histológico nos ovinos experimentais mostrou resultados semelhantes aos do surto, com exceção da ausência de fibrose e infiltrado inflamatório do nervo óptico, caracterizando um quadro agudo. Foram observadas a perda da bainha de mielina dos axônios e a presença de fibroblastos e fibras colágenas no estudo ultra-estrutural do nervo óptico de animais intoxicados espontaneamente. No nervo óptico de animais intoxicados experimentalmente havia vacúolos que separavam as bainhas de mielina dos axônios. Para evitar surtos, sugere-se pesar os animais antes da administração de Closantel para evitar erros no cálculo da dose.(AU)

Intoxicação de ovinos que receberam duas aplicações de closantel, na dosagem terapêutica (7,5mg/kg), com intervalo de 28 dias / Poisoning of sheep that received two treatments of closantel in a therapeutic dose (7.5mg/kg), with an interval of 28 days

This study reports poisoning in sheep wich have received two applications of closantel in therapeutic dosage (7.5mg/kg) within a preestablished 28-day period for effectiveness formulation. A high percentage of efficiency was observed after the first and second treatment, but around 72 hours after the second administration of closantel (D30), three sheep have showed mild apathy, anorexia, diarrhea, bilateral blindness, and dilated pupils without reaction. These three animals, were observed in the following 250 days, and the bilateral blindness remained. Numerous reports of animals poisoned by closantel emphasize that overdose and/or nutritional status of the animals are key factors to occur poisoning due closantel administration. However, in this experiment the signs of poisoning (mild apathy, anorexia, diarrhea and ophthalmic disturbance), observed in the three clinically healthy sheep, occurred when they received two applications of closantel (7.5mg/kg), in a interval of 28 days, highlighting the fact of obtaining a cumulative residual effect of closantel in the animal organism, caused by two consecutive applications, may also be a predisposing factor for sheep to demonstrate irreversible signs of intoxication.(AU)

O presente estudo notifica a intoxicação de ovinos que receberam duas aplicações de closantel, na dosagem terapêutica (7,5mg/kg), com intervalo de 28 dias pré-estabelecido pela eficácia da formulação. Referente aos resultados de eficácia foi possível observar elevado percentual após o primeiro e o segundo tratamento. Cerca de 72 horas após a administração do segundo tratamento (D+30), três animais que receberam closantel demonstraram leve apatia, anorexia, diarréia e cegueira bilateral com ausência de reflexo e midríase bilateral. Estes três ovinos foram observados por cerca de 250 dias após o segundo tratamento, e a cegueira bilateral não regrediu. Os inúmeros casos de animais intoxicados por closantel descritos na literatura enfatizam que a sobredosagem e/ou qualidade nutricional dos animais, são fatores determinantes para que ocorra intoxicação destes animais pelo closantel. Entretanto, no presente trabalho, os sinais de intoxicação (leve apatia, anorexia, diarréia e a alteração oftálmica) observada nos três ovinos clinicamente sadios, ocorreram quando estes receberam duas aplicações de closantel (7,5mg/kg) com o intervalo de 28 dias, evidenciando que o possível efeito residual cumulativo de closantel no organismo animal, desencadeado por duas aplicações consecutivas, também pode ser um fator predisponente para que ovinos demonstrem sinais irreversíveis de intoxicação pelo princípio ativo em questão.(AU)

Oropharyngeal lesions and poisoning by closantel in sheep after antiparasitic treatment

An outbreak of oropharyngeal lesions and poisoning by closantel in sheep after improper handling and anthelmintic drug overdose is described here. Eleven sheep were affected out of 42 that were dewormed. Eight sheep died. Clinically, the animals showed abdominal recumbency, absent pupillary and palpebral reflexes, bilateral blindness, depression, apathy, emaciation, and corneal opacity. Three sheep exhibited swelling on the right side of the mandible. At necropsy, one sheep exhibited a purulent lesion located on the right, next to the root of the tongue. Microscopically, the main finding was status spongiosus in the central nervous system and optic nerve. The retina showed rod and cone degeneration, ganglionic cell layer vacuolation, karyorrhexis, and vacuolation of the outer plexiform layer. The liver of one sheep exhibited diffused coagulative necrosis of hepatocytes in the centrilobular region associated with high infestation of Haemonchus contortus.

Oropharyngeal lesions and poisoning by closantel in sheep after antiparasitic treatment

An outbreak of oropharyngeal lesions and poisoning by closantel in sheep after improper handling and anthelmintic drug overdose is described here. Eleven sheep were affected out of 42 that were dewormed. Eight sheep died. Clinically, the animals showed abdominal recumbency, absent pupillary and palpebral reflexes, bilateral blindness, depression, apathy, emaciation, and corneal opacity. Three sheep exhibited swelling on the right side of the mandible. At necropsy, one sheep exhibited a purulent lesion located on the right, next to the root of the tongue. Microscopically, the main finding was status spongiosus in the central nervous system and optic nerve. The retina showed rod and cone degeneration, ganglionic cell layer vacuolation, karyorrhexis, and vacuolation of the outer plexiform layer. The liver of one sheep exhibited diffused coagulative necrosis of hepatocytes in the centrilobular region associated with high infestation of Haemonchus contortus.(AU)

Alterações oftálmicas associadas à intoxicação experimental por closantel em caprinos / Ophthalmic changes associated with the experimental poisoning by closantel in caprine

Alterações oftálmicas foram experimentalmente induzidas em caprinos após superdosagem com o anti-helmíntico closantel. Foram usados cinco caprinos com sete a oito meses de idade, produtos do cruzamento da raça Saanen com a Pardo Alpino. Os animais mostraram sinais de intoxicação entre quatro e cinco dias após a administração do closantel. Os sinais clínicos caracterizaram-se principalmente por distúrbios neurológicos centrais e cegueira. Ao exame clínico, observaram-se midríase bilateral, perda do reflexo pupilar à luz e cegueira bilateral. À oftalmoscopia indireta, foram observadas degeneração aguda de retina e papiledema. As alterações crônicas mostravam disco óptico acinzentado, atrofia de vasos e da retina. Nos fundos tapetal e não-tapetal notavam-se áreas de despigmentação e lesões irregulares castanho-amareladas. As alterações histológicas consistiam em perda dos neurônios da camada ganglionar e das células da camada nuclear interna e externa da retina. As alterações agudas no nervo óptico e na substância branca do encéfalo foram de degeneração espongiforme. As alterações crônicas do nervo óptico caracterizavam-se por extensa necrose e infiltração de células Gitter.(AU)

Ophthalmic alterations were experimentally induced after overdose with the anthelmintic closantel. Five seven to eight- months-old, Saanen x Alpine caprine were used. The animals showed clinical signs of toxicosis four to five days after the administration of closantel. Clinical signs were primarily characterized by central nervous disturbances and blindness. Clinically, bilateral mydriasis, loss of pupillary light reflex, and blindness were observed. At indirect ophthalmoscopic examination, there was acute retinal degeneration and papilledema. Chronic ocular changes consisted of paleness of the optic disc, vascular atrophy, and retinal atrophy. Areas of pigment loss and irregular yellowish-brown foci were present in the tapetal and non-tapetal fundus. Histological alterations consisted of neuronal loss in the ganglion cell layer and depletion of cells in both the outer and inner nuclear layers of the retina. Acute changes of spongy degeneration were noted in the optic nerve and in the cerebral white matter. Chronic lesions in the optic nerve were characterized by extensive necrosis and infiltration by Gitter cells.(AU)