Zygocotyle lunata as a model for in vivo screening of anthelmintic activity against paramphistomes: Evaluation of efficacy of praziquantel, albendazole and closantel in experimentally infected mice.

Paramphistomes are important parasites in veterinary medicine. There are few anthelmintic drugs available against them. The development of new drugs is urgently needed and this process can be accelerated through the development of rodent models for in vivo testing. Among the few paramphistomes that develop in rodents is the caecal fluke Zygocotyle lunata, a species with which several biological studies have been performed over several decades. Nevertheless, its use as a model for evaluation of anthelmintic drugs had not yet been evaluated. In the present study, we evaluated the efficacy of praziquantel (PZQ 300 mg/kg 5x), albendazole (ABZ 200 mg/kg 5x) and closantel (CLO 50 mg/kg single dose, 50 mg/kg 3x and 25 mg/kg 3x) for treatment of mice experimentally infected with Z. lunata. The animals were infected with 20 metacercariae of the parasite and were treated 30 days post-infection. Untreated groups were maintained as controls. Seven days after the treatments, the animals were euthanized for recovery and counting of parasites. We found that PZQ and ABZ, at the dosages and therapeutic schedule employed here, did not cause significant alterations in worm burden [worm counts 16.0 ±â€¯2.8 (13-19), 17.6 ±â€¯2.1 (14-19) and 16.2 ±â€¯1.9 (13-18) (p = 0.51) in PZQ, ALB and control, respectively]. CLO 50 mg/kg in a single dose caused significant reduction in the number of parasites [treated: 1.8 ±â€¯0.9 (1-3); control: 15.6 ±â€¯2.5 (12-19)], although it did not result in complete elimination of the parasites in any animal. Despite the fact that three doses of CLO 50 mg/kg or CLO 25 mg/kg caused complete elimination of the parasites in most surviving animals, there was significant host mortality. In general, results here obtained are concordant with those of studies performed on ruminant paramphistomes. Given that Z. lunata can be maintained in laboratory rodents, it is a suitable model for screening anthelmintic drugs against paramphistomes.

A molecular phylogenetic study of the caecal fluke of poultry, Postharmostomum commutatum (= P. gallinum) (Trematoda: Brachylaimidae).

Postharmostomum commutatum (Dietz, 1858), a parasite of the caeca of poultry, has been reported from many different parts of the world. Despite its importance, there are no molecular sequences available and its phylogenetic position is unknown in relation to other members of Brachylaimoidea, a group in which taxonomic confusion reigns. Here, morphological and molecular techniques were used to study digeneans from the caeca of free-range chickens found naturally infected in the municipality of Viçosa, state of Minas Gerais, Brazil, between August 2017 and May 2018. The specimens were identified as P. commutatum, with Postharmostomum gallinum Witenberg, 1923 herein considered a junior synonym. Sequences obtained for the 28S, ITS2, and cox-1 genes were compared with sequences available from other species of Brachylaimoidea. Phylogenetic analysis of the three markers indicates P. commutatum formed an isolated lineage from other brachylaimoids, supporting the distinct status of the genus. The topology of phylogenetic trees obtained suggests that the morphology-based classification of families of Brachylaimoidea is artificial and new rearrangements of some genera or creation of new families may be necessary. The sequences newly obtained here will be useful for testing the cosmopolitan distribution of P. commutatum.