Fascioliasis due to Fasciola hepatica (Linnaeus, 1758) is an endemic disease on the Northern Bolivian Altipiano, where human prevalences and intensities arc the highest known, sheep and cattle are the main reservoir hosts, and pigs and donkeys the secondary ones. Investigations were carried out to study the viability of metacercariae experimentally obtained from eggs shed by naturally infected Altiplanic sheep, cattle, pigs and donkeys. A total of 157 Wistar rats were infected with doses of 5, 10, 20 and 150 metacercariae. Metacercariae aged for different number of weeks were used to analyse the influence of age on their viability. The number of worms successfully developed in each rat was established by dissection. Results obtained show that metacercarial infectivity is dependent upon storage time, being lower when metacercariae arc older. The maximum longevity is 31 weeks using doses of 20 metacercariae per rat and 48 weeks with 150 metacercariae per rat, although in the latter case only a very low percentage of worms is recovered. Age-related infectivity of metacercariae from Altiplanic F. hepatica does not significantly differ from that of the liver fluke in lowlands of other countries. Concerning the influence of the isolate according to host species, results indicate that metacercarial viabilities of pig and donkey isolates are similar to the viabilities of metacercariae of sheep and cattle isolates. Thus, pig and donkey have a high transmission potential capacity concerning this aspect. This fact is of great importance for the control of human and animal fascioliasis in this highly endemic zone.
This report addresses the possible impacts of local habitat characteristics on the metacercariae of Clinostomum schizothoraxi Kaw, 1950 infecting crucian carp, Carassius carassius (Linnaeus), from three lakes in Kashmir. The lakes chosen encompass an extremely wide gradient in trophic status - Manasbal (less polluted and mesotrophic), Dal (moderately polluted and eutrophic) and Anchar (strongly polluted and hypertrophic). The results indicate that infrapopulation-level descriptors of abundance of C. schizothoraxi in fish differed between the three lakes and revealed that the infection levels were greater at Anchar Lake. Furthermore, the prevalence, mean abundance and mean intensity of infection also changed during the period of investigation along the seasonal gradient of water temperature. The fact that the abundance patterns of the parasite differed in different populations of the same host provided a unique opportunity for a comparative study on the temporal variations in infection patterns attained during different seasons. In particular, the lake environments showed a high degree of variability in the density profiles of mollusc intermediate hosts and, thus, the differences in the infection status of crucian carp were derived on the basis of intermediate host population size which, in turn, was influenced by the trophic characteristics of the three lakes.
The paper presents a survey of the metacercariae of trematodes found in 581 fishes of 15 species from 39 cenotes (sinkholes) of the Yucatan Peninsula, southeastern Mexico. The following 21 species were found: Echinochasmus sp. 1, Echino-chasmus sp. 2, Echinostomatinae gen. sp. (family Echinostomatidae), Stunkardiella minima (Stunkard, 1938), Alrophecaecum (?) astorquii (Watson, 1976), Peiaezia loossi (Pérez Vigueras, 1957) (Acanthostomidae); Ascocotyle (Ascocotyle) tenuicollis Price, 1935, Ascocotyle (Ascolotyle) sp. 1, Ascocotyle (Phagicola) diminuta (Stunkard et Haviland, 1924), Ascocotyle (Phagicola) sp. 2 (= Phagicola angrense Travassos, 1916 of Salgado-Maldonado and Aguirre-Macedo, 1991), Ascocotyle (Phagicola) sp. 3 (Heterophyidae); Cladocystis trifolium (Braun, 1901) (Opisthorchiidae); Oligogonotylus manieri Watson, 1976 (Cryptogonimidae); Clinostomum cf. complanatum (Rudolphi, 1814) (Clinostomidae); Diplostomum (Auslrodiplostomum) com-paclum (Lutz, 1928), Posthodiplostomum minimum (MacCallum, 1921), Posthodiplostomum sp. (Diplostomidae); Neodiplos-tomidae gen. sp. 1 ; Neodiplostomidae gen. sp. 2 (Neodiplostomidae); and Apharyngostrigea sp. (Strigeidae). All species found are described and figured, and their life cycles are briefly discussed.