In vitro development and hatching success of Alaria spp. miracidia (Trematoda: Diplostomidae)

The complex life cycle of the trematode Alaria spp. begins with eggs produced in the intestine of the definitive host and excreted into the environment. Abiotic factors such as temperature, light, and environmental conditions may influence egg development and hatching; however, data on Alaria spp. egg development under varying conditions remain limited despite their zoonotic potential. This study investigated the effects of light, temperature, desiccation, and dynamic conditions on the development and hatching of Alaria spp. eggs and miracidia under controlled in vitro conditions. Fresh faecal samples were collected from red foxes (Vulpes vulpes), and purified eggs were allocated to eight experimental conditions: natural light, permanent light, darkness, freezer, refrigerator, incubator, desiccation, and dynamic conditions. Egg size ranged from 0.105 to 0.128 mm in length (mean 0.117 ± 0.005 mm) and 0.070–0.090 mm in width (mean 0.083 ± 0.004 mm). Development from unembryonated eggs to hatched miracidia occurred within 3–16 days (mean 11 days), depending on conditions. Temperature was the key factor affecting development and hatching. Eggs remained viable after freezing at − 20 °C and resumed development under optimal conditions, whereas exposure to 37 °C resulted in development without successful hatching and high mortality. Light had no detectable effect on egg development or hatching. Desiccation exceeding four minutes markedly reduced egg viability, while dynamic conditions significantly enhanced hatching success. These findings provide new insights into the environmental resilience of Alaria spp. eggs and contribute to understanding their persistence, transmission potential, and associated zoonotic risk.