Ovicidal activity of Pochonia chlamydosporia and Paecilomyces lilacinus on Toxocara canis eggs.

Abstract

An assessment was made of the ovicidal activity of egg-parasitizing fungi Pochonia chlamydosporia (isolates VC1 and VC4) and Paecilomyces lilacinus on Toxocara canis eggs in vitro. The fungal isolates were inoculated onto Petri dishes with 2% water-agar (2% WA) and stored at 25 degrees C for 10 days in an incubator, in the dark. The control group was comprised of Petri dishes without fungi, containing the 2%WA medium only. Later, 1000 embryonated eggs were placed on the surface of the plates with fungal isolates and also on the control plates, and were then incubated at 25 degrees C for 7, 14 and 21 days. At these intervals, the eggs were retrieved and underwent percentage assessment according to the following parameters: no changes; type 1 effect, physiological and biochemical effect without morphological damage to eggshell, with visualization of hyphae adhered to eggshell; type 2 effect, lytic effect with morphological changes in embryo and eggshell, without hyphal penetration through the eggshell; type 3 effect, lytic effect with morphological changes in embryo and eggshell, with hyphal penetration and internal egg colonization. All the fungal isolates showed ovicidal activity (type 3 effect) on T. canis eggs, with 13.8%, 20.5% and 20.3% of ovicidal activity using P. chlamydosporia isolate VC1 after 7, 14 and 21 days, whereas isolate VC4 showed 15.2%, 19.0% and 21.7% of ovicidal activity at the same time intervals. P. lilacinus showed ovicidal activity of 12.3%, 18.8% and 20.0% after 7, 14 and 21 days. P. chlamydosporia and P. lilacinus were effective in vitro on T. canis eggs and can be considered a potential candidate to biological controller of those nematodes.