Lethal effect of high temperatures on the eggs of Fasciola hepatica

Fasciolosis is a cosmopolitan parasitic disease with considerable economic and public health importance. Fasciola hepatica is the major cause of fasciolosis in man and domestic animals. Although remarkable research works have been done around the optimum temperature and time required for miracidial development, little is known about the exact susceptibility of Fasciola hepatica eggs to high temperatures. In the present study, Fasciola hepatica eggs were initially incubated at 40°C, 45°C, and 50°C for various times (1, 2, 3, 4 and 5 h), followed by incubation at 28°C for 16 days. Miracidial formation was subsequently investigated on the 16th day of incubation. Even though the rate of miracidial formation in the control group was 52%, in the eggs incubated at 40°C for 1, 3, and 5 h, the miracidial formations were 51.4%, 42.4% and 39.9%, respectively, and these values in the group incubated at 45°C were 46%, 42.5% and 33.7%, as well. However, in the case of incubation at 50°C for 1, 2, 3, 4 and 5 h, these values were recorded as 1.96%, 0.57%, 0.07%, 0.00% and 0.00%, respectively. The results indicated that the eggs were susceptible to high temperatures and incubation of the eggs at 50°C for 4 h was enough to significantly inactivate the eggs and prevent miracidial formation (P 0.001). However, using the livestock faeces as fertilizer in many rural areas may lead to the contamination of pasture. According to the findings of this study, in the areas with a high prevalence rate of Fasciola hepatica, manure storage for a sufficient time or heating the livestock manure before use as fertilizer is strongly recommended.