Biological control of soil transmitted helminths (STHs) in a zoological park by using saprophytic fungi

Toxascaris leonina and Trichuris sp. are soil-transmitted helminths (STHs) infecting domestic and wild mammals. The antagonistic effect of the saprophytic filamentous fungi Mucor circinelloides and Verticillium sp. was examined on eggs of T. leonina passed in the feces of captive lynxes (Lynx lynx) kept in a zoological park. The activity of M. circinelloides and Trichoderma atrobrunneum was tested on eggs of Trichuris sp. shed by captive dromedaries (Camelus dromedarius). The parasiticide activity was assessed by measuring the ovistatic (delayed development) and ovicidal (non-viability) effects on eggs placed in Petri plates, and by spraying spores directly onto fecal samples. Based on the observation of that hyphae of M. circinelloides, Verticillium sp. and T. atrobrunneum adhered to the eggshells, penetrated and destroyed the inner embryo, an ovicidal type 3 effect was concluded. Development of eggs of T. leonina and Trichuris sp. in the feces was delayed in the presence of all fungi, and one third remained at the stage of zygote. A significant reduction of T. leonina viable eggs was recorded in the feces sprayed spores of M. circinelloides (58%) or Verticillium sp. (67%). Fifty percent of the eggs of Trichuris sp. became into non-viable by 30 days after the exposure to either M. circinelloides or T. atrobrunneum. It is concluded that distribution of the filamentous fungi M. circinelloides, Verticillium sp. and T. atrobrunneum constitutes a novel approach to conduct the biological control of the STHs (T. leonina and Trichuris sp.) affecting wild animals captive in a zoological park.