Reviewing Fasciola hepatica transmission in the West Indies and novel perceptions from experimental infections of sympatric vs. allopatric snail/fluke combinations

Abstract

Fasciolosis is an important food-borne parasitic disease affecting over two million people worldwide with economic losses related to cattle production of up to US$ 3 billion annually. Despite the long known presence of Fasciola hepatica in the Caribbean islands its transmission is not well known. This study reviews historical and recent data on fasciolosis in the West Indies, revealing for the first time the outcomes of sympatric and allopatric fluke/snail interactions in the area by exploring the susceptibility of four lymnaeid species after exposure to F. hepatica isolates from Cuba, the Dominican Republic and France. Overall, Galba cubensis showed a mean prevalence of 71.8% and appears to be the most suitable intermediate host species irrespective of the isolate used. Sympatric combinations (snail and parasite from the same country) were generally more compatible (higher susceptibility, parasite intensity and snail survival post-exposure) and only the allopatric interaction of French G. truncatula/Cuban F. hepatica attained 100% prevalence and mean intensity over 33 rediae/snail. However, certain Dominican populations of Pseudosuccinea columella showed high parasite intensities (>30 rediae/snail) when infected with Cuban flukes, highlighting the potential risks of biological introductions. Overall, high compatibility in most sympatric combinations compared to low or moderate compatibility in allopatric ones, suggests the existence of local adaptation from a long sustained interaction that has led to high rates of transmission. Interestingly, attempts to infect G. schirazensis with sympatric and allopatric flukes failed and coupled with the lowest survival rates which supposes a low risk of fasciolosis transmission in areas where this is the only snail species. Although there are significant gaps in the actual status of fasciolosis transmission from several islands in the West Indies these results show a permanent risk. We conclude that fasciolosis transmission is high in areas where the local snail, G. cubensis, occurs, and will be even higher in the presence of the invasive P. columella.

Genetic diversity and relationships of the liver fluke Fasciola hepatica (Trematoda) with native and introduced definitive and intermediate hosts

“…Overall, we found differences in compatibility regarding their susceptibility, capacity of the parasite to expand inside the snails and survival of the latter after the exposure. The compatibility showed by sympatric G. truncatula is in agreement with the existence of local adaptation in this system (Vázquez et al, 2019). Inversely, the allopatric population of G. truncatula showed low compatibility with F. hepatica.…”

“…Briefly, we collected the content of the bile vesicle from cattle obtained in the abattoir (see Section 2.1) for mass egg retrieval. The bile was sift using pore size‐decreasing set of sieves and continuous washing with saline solution (0.85%) to isolate the eggs that were stored in tubes containing saline solution at 4°C in the dark until use (Vázquez et al., 2019). When the snails were one week old, we changed the eggs to spring water and incubated for 15 days in darkness at 27°C.…”

“…The experimental infection methodology was followed as in Vázquez et al. (2019) individually exposing 30 snails of each population to a dose of five F. hepatica miracidia.…”

“…When the snails were one week old, we changed the eggs to spring water and incubated for 15 days in darkness at 27°C. The experimental infection methodology was followed as in Vázquez et al (2019) individually exposing 30 snails of each population to a dose of five F. hepatica miracidia.…”

Towards the comprehension of fasciolosis (re-)emergence: an integrative overview

“…Experimental infections of intermediate hosts indicate that their interaction with Fasciola parasites is usually characterized by relatively high survival of infected snails during the mid-late days of pre-patent infection and early-patent period (Sorensen and Minchella, 2001; Dar et al ., 2004; Ashrafi and Mas-Coma, 2014; Alba et al ., 2018; Vázquez et al ., 2019). In the definitive hosts, particularly in humans, fasciolosis is frequently non-fatal and clinically mild especially in the case of low-intensity infections (Behm and Sangster, 1999).…”