Fungos nematófagos no controle biológico de nematoides gastrintestinais de equinos mantidos à pasto

Abstract

Os equinos são apontados como sendo um dos animais mais susceptíveis a uma gama de parasitos e podem abrigar várias espécies em um mesmo momento. O parasitismo ocupa lugar de destaque devido aos prejuízos consequentes da infecção parasitária. Conforme a carga parasitária, os helmintos podem causar desde um pequeno desconforto abdominal, fraqueza, pelagem áspera, retardo de crescimento, hiporexia, anemia, cólicas, diarreias ou constipações até episódios fulminantes de cólica e pode levar o animal a óbito. Devido à alta valorização destes animais e sua relevância na economia mundial, é indispensável a atenção quanto à saúde dos equinos, pois são animais vulneráveis à inúmeras doenças. A principal forma de controle de helmintose, na maioria dos sistemas de criação utiliza-se exclusivamente compostos químicos antiparasitários. Normalmente são administrados antiparasitários comerciais, e os principais grupos químicos utilizados para o controle de helmintose em equinos são os benzimidazóis e as lactonas macrocíclicas. Mas o problema vem sendo o uso de maneira indevida, indiscriminada e sem a associação de estratégias auxiliares de controle. A situação mundial atual é de resistência à maior parte das classes de antiparasitários comerciais disponíveis no mercado. O controle biológico com fungos nematófagos pode ser empregado para diminuir populações de parasitos, já que estes são seus antagonistas naturais. Uma das vantagens na utilização dos fungos nematofágos no controle biológico é devido ao sinergismo no controle químico, o que obtém uma maior atuação sobre as formas infectantes presentes nas fezes, bem como sobre os helmintos adultos que estão parasitando o animal.

Nematophagous fungi and their influences on parasitic control in sheep

“…These microorganisms act in a variety of ways, usually in the form of inert chlamydospores, which under favorable conditions, mainly involving climate, humidity, and food availability (varied larvae in general), develop into mycelium. Despite appearing as a simple denomination, nematophagous fungi have a distinct variation, the main way to distinguish them, is characterized by capture and feeding habits, dividing the genera better known as predators, ovicidal, producers of metabolites, and endoparasites of larvae (Carneiro, 1992).…”

“…Predator fungi exert a "predation" and capture activity in the soil, these hyphomycetes, when they become matured under appropriate conditions, produce adhesive traps, which propagate and spread randomly through the soil, when touched by larvae, immediately occurs a bond and immobilization of them, allowing the said fungus in question to penetrate the cell wall and feed the immobilized prey. Carneiro (1992) characterizes that the formation of adhesive traps can also be divided, according to the genus of fungi, such as the way how it spread and feed specific to its denomination, being for adhesive rings, or traps: Arthrobotrys spp, Duddingtonia spp, Dactylaria spp and Dactylella spp and genera that use adhesive mycelium:…”

“…The influence of temperature can generate suppression of fungal activity, leading to low development and propagation of chlamydospores, in addition, predatory fungi are criticized and doubted due to the lack of selectivity when predicting larvae (Silva et al, 2010). Lack of preference for predation can cause, depending on the situation, only attacks on free-living species, allowing infecting larvae to remain viable in the environment for much longer (Carneiro, 1992). Vilela et al (2012) performed evaluations in which goats kept in confinement were fed pellets containing mycelium of D. Flagrans and had considerable success in reducing the numbers of OPG for groups receiving treatment.…”

“…Some fungal species attack eggs, becoming a practical tool to eliminate soil populations because destroying a significant portion of them, would imply considerably reducing the population of infecting larvae present there (Carneiro, 1992). These variants of fungi act directly by parasitizing the surface of eggs, once this process is performed, penetrate the wall, and perform absorption and transport of nutrients (Araújo et al, 1995).…”

“…These variants of fungi act directly by parasitizing the surface of eggs, once this process is performed, penetrate the wall, and perform absorption and transport of nutrients (Araújo et al, 1995). Despite an agent in the biological control of populations of infecting nematodes, studies denote that the action of these fungi is less active than their similar predators, generally, the preference of attack occurs in soil nematodes, which infect and destroy plant structures, to the detriment of such species depositing their eggs in gelatinous structures, whose are readily vulnerable to the colonization of fungi, different from infectious genera, which eggs in the soil are not present in this type of substance (Carneiro, 1992;Freitas Soares et al, 2018).…”