Abstract
BACKGROUND: Fasciolosis is a food-borne disease that causes major economic losses, globally. This zoonotic disease is caused by Fasciola hepatica and Fasciola gigantica species which employ freshwater snails from the family Lymnaeidae as their intermediate hosts. Thus, a key aspect of understanding the epidemiology of the disease lies in understanding the transmission ecology of the parasite. Therefore, this systematic review and meta-analysis were conducted to assess the experimental susceptibility and prevalence of natural infections of F. hepatica and F. gigantica in lymnaeid snails. METHODS: Relevant peer-reviewed articles published in the past 20 years (2004-2023) were searched and appraised. Prevalence and infection rate estimates were based on 41 studies that met the inclusion criteria. RESULTS: Five thousand five hundred and seventy-five (5,575) lymnaeid snails were subjected to experimental infections and 44,002 were screened for natural infections. The overall pooled infection rate was higher in experimental infections 50% (95% CI [42-58%]) compared to natural infections of field-collected snails 6% (95% CI [0-22%]). The highest pooled infection rate was recorded in South America at 64% (95% CI [48-78%]) for experimental infections while the lowest was recorded for natural infections at 2% (95% CI [0-6%]) in Europe and 2% (95% CI [0-17%]) in Asia. In experimental studies, F. gigantica recorded the highest pooled prevalence at 73% (95% CI [61-84%] compared to F. hepatica which recorded 47% (95% CI [38-56%]). For natural infections, however, F. hepatica had the highest prevalence (12% (95% CI [0-30%]) while the lowest was noted for naturally infected F. gigantica at 2% (95% CI [0-18%]). Based on the snail species, the highest pooled prevalence was recorded for Pseudosuccinea columella infected with F. hepatica and F. gigantica at 47% (95% CI [33-61%]) while the lowest was recorded for F. hepatica naturally infected Galba truncatula at 4% (95% CI [0-10%]). Natural Fasciola spp. infections in intermediate snail hosts decreased in prevalence while experimental infections have increased in prevalence over the past 20 years. CONCLUSIONS: While there seems to be a strong intermediate host specificity between the two Fasciola spp., experimental infection results showed that G. truncatula and R. natalensis are susceptible to F. hepatica and F. gigantica, respectively.