Effect of water temperature on life history traits of Radix natalensis, the intermediate host of Fasciola gigantica.

BACKGROUND

Radix natalensis, a gastropod, serves as an intermediate host of Fasciola gigantica in tropical and subtropical regions, causing fascioliasis, a disease of public health and veterinary importance worldwide. Predicting disease burden requires understanding how climate change influences its life-history traits. This study investigated the effects of temperature on the life-history traits of R. natalensis. Snails were exposed to six temperature treatments (15.5 ℃, 19.5 ℃, 20.3 ℃ (control), 24.6 ℃, 29.8 ℃, and 35.1 ℃). For each treatment, 10 jars served as replicates, each containing two snails. Observations were conducted over two follow-up periods (2 weeks and 9 weeks). Data analysis was performed using repeated-measures ANOVA, the Kruskal -Wallis test, and the log-rank test.

RESULTS

In the first two weeks of the study, shell height was highest among snails exposed to 24.6 °C (4.14 ± 0.56 mm) and least among those at 35.1 °C (3.90 ± 0.50 mm. A significant increase in shell height was observed to be associated with the interaction between temperature and time (RM Anova F6,72 = 4.51, p < 0.001). In contrast, the effect of temperature alone was not statistically significant (RM Anova F5,72 = 1.95, p = 0.092). For the duration of the experiment, snails maintained at 19.5℃ attained a higher mean shell height (5.43 ± 1.04 mm) compared to those at 15.5 °C (4.85 ± 0.89 mm); however, the overall effect of temperature on shell height was not statistically significant (F3,512 = 0.07; p = 0.978). On the other hand, there were notable differences in reproductive production between temperature treatments. Egg masses were substantially higher in snails kept at 19.5 °C: 22 (11) than in those kept at 15.5 °C: 6 (8); (z = - 2.762; p = 0.003). Survival probability declined with increasing temperature, particularly at 29.8 °C and 35.5 °C. Overall, survival rates differed significantly across the temperature treatments (Log-rank test: p < 0.0001).

CONCLUSION

Radix natalensis's survival and reproductive performance are temperature-dependent, whereas snail growth is influenced by the combination of incubation conditions and time. These findings imply that temperature fluctuations will play a critical role in shaping the future transmission dynamics of fascioliasis.