Fungal ovicidal activity on Toxocara canis eggs

Visceral toxocariasis is a parasitic zoonosis caused by Toxocara canis. The prevalence of this parasite in dogs, soil contamination and the resistance of eggs increase human exposure to the disease. Moreover, the difficulties of the control measures justify the need for alternative ones.

The objective of this study was to evaluate the in vitro ovicidal activity of fungi isolated from soils from public places in the city of Pelotas, Rio Grande do Sul, Brazil, on Toxocara canis.

Samples of soil from ten localities were inoculated onto Petri dishes with 2% water-agar (WA) that contained antibiotics, and incubated at 25°C/21 days. Isolated fungi were tested in vitro for ovicidal activity, with five replicates. One mL of an embryonated Toxocara canis egg suspension (10(3) eggs) was poured over the fungal cultures after 10 days of growth. At intervals of 7, 14 and 21 days, 100 eggs were removed from each plaque and evaluated by optical microscopy.

Acremonium, Aspergillus, Bipolaris, Fusarium, Gliocladium, Mucor and Trichoderma were isolated from the soil. A significant ovicidal type 3 effect was observed in Trichoderma, Fusarium solani complex and Acremonium. Those isolates from the genus Trichoderma showed their ovicidal effect on the 14th day of fungus-egg interaction. The other fungal genera tested showed a type 2 effect.

These results suggest that the use of Trichoderma and Fusarium solani complex in biological control of T. canis is promising; however, further studies should be performed.