RAPD variation in two trematode species (Fasciola hepatica and Dicrocoelium dendriticum) from a single cattle population

The method of random DNA amplification by PCR with arbitrary primers (RAPD-PCR) was used for the description and estimation of genetic variation in two trematode species, Fasciola hepatica (n = 21) and Dicrocoelium dendriticum (n = 8). The studied trematodes were liver parasites of five cattle individuals belonging to the same herd. To study the F. hepatica population, five primers were selected, which revealed 230 RAPD markers in five samples of parasites isolated from five different host individuals. Using 87 RAPD markers, a comparison of variation was conducted between F. hepatica and D. dendriticum samples from the same host individual. Based on the estimates of RAPD variation for the individual samples of parasites collected from each of five host individuals and for the total F. hepatica population, standard indices of genetic similarity (S), diversity (H), polymorphism (P), and population subdivision (FST) were calculated. From the indices of similarity in pairs (S), dendrograms were constructed, which reflect genetic relationship between the representatives of two species and between F. hepatica individuals isolated from the same or different host individuals. It was revealed that polymorphism level (P) varied within a range of 35.5 to 83.2% in the studied F. hepatica population and reached 95.1% in the studied D. dendriticum population. Two different trematode species that simultaneously parasitize the same host animal were characterized by similar estimates of polymorphism and genetic diversity and by similar topology of genetic similarity dendrograms. The degree of genetic similarity between F. hepatica and D. dendriticum was significantly lower (20%) than between five F. hepatica samples (41.4%) that formed two unequal clusters. Each of these clusters represents a heterogeneous group consisting of parasites collected from three or four host individuals. In the individual samples of parasites related to each of the studied host individuals, the indices of genetic similarity (S) and diversity (H) varied within a range of 43.3 to 64.8% and 25.1 to 56.6%, respectively. In the total F. hepatica sample, the estimates of intraspecific variation, the topology of dendrograms, and the FST index (7.4%) indicate the absence of clear genetic differentiation between the samples of parasites isolated from different host individuals. Possible reasons for the high level of genetic variation in the studied trematode populations and the genetic consequences of host-parasite interaction are discussed.