Fasciola hepatica: surfaces involved in movement of miracidia and cercariae

Ecology of free-living metacercariae (Trematoda)

The presence of trematodes with a free-living metacercarial stage is a common feature of most habitats and includes important species such as Fasciola hepatica, Parorchis acanthus and Zygocotyle lunata. These trematodes encyst on the surface of an animal or plant that can act as a transport host, which form the diet of the target definitive host. Although these species are often considered individually, they display common characteristics in their free-living biology indicating a shared transmission strategy, yet in comparison to species with penetrative cercariae this aspect of their life cycles remains much overlooked. This review integrates the diverse data and presents a novel synthesis of free-living metacercariae using epibiosis as the basis of a new framework to describe the relationship between transport hosts and parasites. All aspects of their biology during the period that they are metabolically independent of a host are considered, from cercarial emergence to metacercarial excystment.

Two new species of cosmocercids (Ascaridida) in the toad Chaunus arenarum (Anura: Bufonidae) from Argentina

Aplectana tarija n. sp. and Cosmocercoides lilloi n. sp., intestinal parasites of the toad Chaunus arenarum, are described. Of the 41 nominal species of Aplectana, A. tarija n. sp. represents the 22nd Neotropical species and the second species reported from Argentina. Of the 14 nominal species of Cosmocercoides, C. lilloi n. sp. represents the 15th species and the first species reported from South America.

The co-occurrence of Toxocaraocular and visceral larva migrans syndrome: a case series

Introduction

Ocular toxocarosis associated with high peripheral eosinophilia and together with systemic signs of visceral damage has been reported sporadically. Eye infections caused by numerous migrating larvae of Toxocara parasites, probably due to re-invasion or delayed reactivation, and leading to a progressive loss of vision is relatively rare. We report three atypical cases of toxocarosis with the co-existence of ocular larva migrans syndrome and generalized signs of Toxocara infection in schoolboys.

Case presentation

Two children aged 8 and 14 years respectively, with symptomatic ocular and visceral larva migrans syndromes, and one 16-year-old adolescent with chronic multifocal eye invasion, characterized by severe granulomatous retinochoroiditis with unilateral blindness, chronic abdominal pain and generalized synthesis of total immunoglobulin E antibody are described. The three patients, heavily infected with Toxocara species were boys of Polish origin. Ocular location of the parasite was confirmed by the detection of intraocular synthesis of specific anti-Toxocara immunoglobulin G antibody in aqueous humour samples from the affected eyes. Immunological parameters of tissue eosinophilia, allergy or hypersensitivity reactions to the presence of the migrating Toxocara parasites were analysed. Irreversible eye complications were observed in the patients with high level of exposure to Toxocara species in a contaminated environment, with a suggestion of possible re-activation or re-infection by different species or strains of the parasite.

Conclusions

Wide promotion of sanitary education is strongly justified in children and adolescents in Toxocara endemic areas in order to reduce the potential risk of primary invasion or re-infection with the parasites, which can lead to a severe course or progression of the disease. A long-term clinical follow-up and more intensive anti-parasitic treatment is recommended in patients with subclinical and overt forms of toxocarosis to prevent later reactivation of the migrating larvae in tissues.

Identification of life cycle stages of Cyathocephalus truncatus (Cestoda: spathebothriidea) using molecular techniques

Morphological identification of tapeworm species at larval stages (procercoids and cysticercoids) is often difficult because few diagnostic characters are available. In the present study, a molecular approach (sequencing of partial 18S rDNA gene) was used to evaluate the genetic similarity between adult specimens of Cyathocephalus truncatus (Pallas, 1871) (Cestoda: Spathebothriidea) found in fish, its definitive host, and procercoids of the same species recovered from amphipod, Echinogammarus stammeri (Karaman, 1931). Furthermore, cestode cysticercoids of uncertain species were found in the amphipod's hemocoel. The sequences obtained from adults and procercoids were identical, and even very similar to those of C. truncatus available in GenBank, whereas the sequences obtained from cysticercoids differed significantly from those of adults and procercoids, indicating that these larvae belong to another species; later it was demonstrated that they were cysticercoids of Microsomacanthus pachycephala (Linstow, 1972), a cestode of the Hymenolepididae (Cyclophyllidea). The results of this investigation show that the comparison of nucleotide sequence data may avoid misclassification of developmental stages of parasites, which use the same intermediate host.