A low molecular weight fraction (30 KDa) of the cattle filarial parasite Setaria digitata that was earlier demonstrated to have allergenic activity was characterized to be a zinc-dependent cysteine proteinase. Immediate type hypersensitivity (ITH) reaction to the proteinase was evaluated in lymphatic filariasis patients and in endemic controls from Orissa, India. The extent of ITH positivity to the proteinase in infected individuals ranged from 20% in chronic filariasis (CP) patients group to 56% in asymptomatic microfilaraemic carriers (AS). About 62% of endemic normals (EN) were also ITH positive. The serum levels of IgG subclasses were compared in ITH positive and ITH negative filarial patients (AS and CP) as well as in endemic normals (EN) respectively. IgG4 levels were found to be inversely dependent on ITH reaction only in AS groups. Asymptomatic patients (AS) with positive ITH reactivity had lower IgG4 than ITH negative individuals from the same group. The serum levels of other IgG subclasses except IgG2 did not correlate with ITH reactivity. IgG2 levels were higher in ITH negative EN and CP patients but not in the AS group.

The subchronic effect of mercury on selected immunological parameters was studied in guinea pigs with experimental Ascaris suum infection. HgCl2 given for 28 days reduced significantly T- and B-cell populations in the lymphoid organs and the phagocytic ability of peritoneal macrophages. The subsequent infection of HgCl2-intoxicated animals elevated the studied immunological parameters, but in comparison with infected non-intoxicated guinea pigs they remained significantly suppressed. The mercury compound in infection stressed animals caused a slight alteration of the complement CH50 and AH50 activity. The specific circulating antibody level in infected and HgCl2 treated animals rose a little by day 12 p.i. and then again decreased significantly, compared with untreated guinea pigs. The mean intensity of infection with migrating Ascaris larvae in HgC12 -treated animals increased by 15%, compared with controls.

Cytochrome c oxidase in the mitochondria of the tegument and tegumental and parenchymal cells was examined cytochemically in Echinostoma trivolvis, Zygocotyle lunata, Schistosoma mansoni, Fasciola gigantica and Paragonimus ohirai, trematodes that inhabit different sites in their vertebrate hosts. Clear differences in enzyme activity occurred in the mitochondria of these species, probably reflecting the different energy metabolisms of these worms. Marked aerobic metabolism occurred in S. mansoni and P. ohirai adults that inhabit the host mesenteric veins and the lungs, respectively. The tegument and parenchymal cells of S. mansoni possess relatively few, small mitochondria with tubular cristae which are heavily reactive for cytochrome c oxidase. In P. ohirai, the activity for cytochrome c oxidase in tegumental mitochondria increased gradually from juveniles to adults, reflecting that the respiratory activity increased with growth and the aerobic metabolism is activated when the worms reach the lung. P. ohirai juveniles and adults had two types of mitochondria with different shapes and enzyme activities that were located in two different types of parenchymal cells. The intestinal species, E. trivolvis had mitochondria in the basal aspect of the tegument, and some variations in enzyme activity of their mitochondria in the tegumental and parenchymal cells were observed, suggesting that they possess both aerobic and anaerobic metabolic systems. Z. lunata that live in rodent caeca are devoid of mitochondria in the tegument and have many characteristic mitochondria with undeveloped cristae in the parenchymal cells. Mitochondria of F. gigantica showed weak or no activity for cytochrome c oxidase, suggesting that the worm is well-adapted to an anaerobic environment in the host bile duct.

For the first time the development of the excretory system Levinseniella brachysoma metacercariae (Trematoda: Microphallidae) obtained experimentally from Gammarus oceanicus has been described. The bladder wall of 8-day post-infection (P.I.) larvae consists of a syncytium covered with microvilli. Its cytoplasm contains well-developed rough endoplasmic reticulum (RER), free ribosomes, small oval dense mitochondria and numerous large membrane-bounded (about 5 μm in diameter) spherical granules. Later the size of the excretory bladder and the number of nuclei and RER cisternae increases. The large spherical granules disappear completely but spherical dense bodies (up to 4 μm in diameter) devoid of limiting membranes appear. The bladder lining forms thick columnar projections directed towards its lumen. Accumulations of microlamelli occur only on the lumen surface between adjacent projections. By the 42nd day P.I. the bladder wall has two separate components: the columnar projections and the syncytium between them.

The parasite burden in the liver and peritoneal cavity and antibody levels directed to whole worm extract, have been monitored in serum from ICR-strain mice, infected orally with 55 tetrathyridia of Mesocestoides corti (Cestoda, Cyclophyllidea). The subcurative doses (3x or 6x) of praziquantel (PZQ) (10 mg.kg−1 body weight) were administered to mice from day 14 post infection (p.i.) in two drug formulations: as PZQ suspended in Dorfman vehicle, or as PZQ incorporated in liposomes (lip.PZQ). The appearance of antibodies was time-dependent and correlated with the rate of reduction in numbers of tetrathyridia. PZQ in three and six doses caused the highest fall of parasite numbers in the liver on day 1 post therapy (p.t.). In the peritoneal cavity, a similar reduction in worm burden occurred but only after six doses of the drug. The worm count in the peritoneal cavity from groups of mice injected with lip.PZQ decreased most markedly on day 7 p.t., in the group treated with six doses of the drug. In the liver, the highest larvicidal effect, compared with the controls, was observed 6 days later (i.e. day 13 p.t.), following three doses of lip.PZQ. In all treated groups, two peak values of antitetrathyridial antibody levels were detected between days 1 and 13 p.t. (i.e. days 17 to 29 p.i.), after which there was a gradual but continuous increase in antibody titre. After treatment with six doses of both drug formulations (PZQ and lip.PZQ), the occurrence of the first maximum and minimum of antibody serum levels was delayed 6 days, compared to those groups treated with three doses of the drugs. Empty liposomes had some immunomodulatory effect on the antibody response, with significant decrease in antibody titres after three doses over the experimental period, but not after six doses.

The cyst wall of the metacercaria of Gynaecotyla adunca (Microphallidae: Digenea) was subjected to comprehensive histochemical analysis. At the light microscope level, a uniformly thick, bipartite cyst wall, probably wholly of parasite origin, was evident. Structural modification of the cyst wall to provide an escape aperture was not apparent. The thicker, inner layer was comprised of phospholipid and glyco- and/or mucoproteins, possibly similar in structure to collagen. The outer layer was highly proteinaceous and contained additional amounts of acidic and neutral mucosubstances. The results are discussed in the context of previous observations regarding the excystment requirements of this microphallid species.

Since Ireland is the only country in which Pomphorhynchus laevis (Acanthocephala) uses brown trout (Salmo trutta) as its preferred definitive host, the population biology of the parasite in this host was investigated thus enabling a comparison to be made with data collected on P laevis from other hosts, particularly the cyprinids, chub and barbel. Over a period of 12 months, 549 brown trout were caught from two lakes, Lough Feeagh and Bunaveela Lake, in the Burrishoole River system, Co. Mayo, Ireland. The parasite component community was dominated by a single species, P laevis. Fifty eight percent of the trout sample were infected with the acanthocephalan and the mean abundance (± SD) was 3.1 ± 5.1. The relationships between the prevalence and abundance of P laevis and season and site of host capture and host age and sex were explored. As single factors none of these parameters emerged as significant contributors to changes in parasite abundance although some interaction terms proved to the significant. A random sample of over 700 P laevis parasites were subjected to further investigation and their size, position in the intestine and maturity status are described. Parasites attained an average weight of 7 mg and occupied the posteriad positions within the fish intestine (77%). Parasites from this sample of Irish brown trout attained a similar average size to those found in chub and barbel from England. 42.3% of the total parasites examined contained ovarian balls only and 17% contained fully mature acanthors. Therefore only a moderate proportion of female worms contained mature acanthors in these trout whereas the majority of worms recovered from a sample of chub were gravid. Utilizing a logistic regression model, parasite size, season, and site of host capture emerged as particularly significant factors which contribute to whether a parasite contains mature eggs.

A total of 549 brown trout were caught from two lakes, Lough Feeagh and Bunaveela Lake, in the Burrishoole system, Co. Mayo, Ireland. Seven species of metazoan parasite were detected but only four species occurred in ≥10% of the sample. The parasite community of the trout was dominated by a single species, Pomphorhynchus laevis, with a prevalence of 58%. Only one allogenic helminth species was recorded from the trout, Diphyllobothriurn ditremum, with the community mainly comprising autogenic species. Few differences were found between the two lakes, although the larger lake, Lough Feeagh, did contain some trout which harboured more parasite species and had, on average, fish with higher numbers of individual parasites. Measures of species richness and diversity were very low, indicating an impoverished helminth community with little potential for interspecific interactions. Host age was found to significantly influence these indices of infracommunity structure.

Adults of Echinostoma caproni, F. paraensei, and E. trivolvis were processed for starchgel electrophoresis. Ten enzyme systems representing 12 structural loci were examined using three different buffer systems. E. paraensei and E. caproni were found to be genetically inbred as indicated by the lack of heterozygosity in individual worms. All three taxa showed fixed differences indicating they are distinct species. Fixed differences were found between E. paraensei and E. caproni in six enzyme systems, between E. paraensei and E. trivolvis in five enzyme systems, and betweenE. trivolvis and E. caproni in five enzyme systems. Phenic relationships among the three species showed E. caproni was genetically more similar to E. trivolvis than to E. paraensei.

The ultrastructure of the reproductive organs of adult female T. spiralis was described on the basis of extensive observation under an electron microscope. The organisms were recovered from the host intestine 7 days after oral infection. The organs consisted of a single ovary, seminal receptacle, uterus and vagina, confirming the reports described by previous authors at light microscopical level. All the organs were surrounded by a basal lamina and epithelial cells, and were bathed in haemolymph. Ova were formed in a germinal zone on the ovary wall exhibiting a half-moon shape, and spread to other sides of the ovary Mature ova exhibited a smooth cell surface, cuboidal shape, prominent cytoplasmic polysomes, a clear nucleus and a well-developed nucleolus. Embryos in early stage of development consisted of numerous small cells and were surrounded by a sheath.As they matured they shed the sheath and left a pool of sheaths in the uterus. During oogenesis and embryogenesis of adult worms in normal development, there occurred lipid droplets and the degradation of embryos; reportedly signs of worm damage.

Light microscopy was used to study excystation of Echinostoma caproni metacercariae in various media. Optimal excystation was observed in an alkaline trypsin-bile salts medium (TB) at 40 ± 1°C. The percentage of excystation in TB medium declined following either acid pepsin or acid saline pretreatment. Excystation rarely occurred in either trypsin or bile salts alone. Dissolution of the outer cyst occurred in TB medium thus facilitating excystation. Activation of the larva within the inner cyst led to its eventual release through an aperture in the mucoid plug region. Excystation of this species was facilitated by both intrinsic and extrinsic factors. There were considerable differences in excystation events between this species and the related allopatric species, E. trivolvis

The distribution of cobalt in parasitic helminths belonging to the trematodes, cestodes or nematodes was determined by the use of an atomic absorption spectrophotometer. The results of these analyses have demonstrated that growing trematodes (smaller forms) with active oogenesis and spermatogenesis contained more cobalt than older forms (large or very old adults) with empty uteri and large lobulated testes. In cestodes, the neck region of cysticerci and immature proglottids of adults showed more cobalt than the cyst portion of cysticerci and hydatid or mature and gravid proglottids of worms. Similarly, the youngest endogenous daughter cysts of Echinococcus granulosus showed more cobalt in their walls than those of larger forms. The element was found more concentrated in nematode eggs than in adult females, irrespective of species of host.

The random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) technique was applied to two closely-related echinostome species, Echinostoma trivolvis and E. caproni, to demonstrate interspecffic polymorphisms of genomic DNA. Band patterns generated using five individual primers showed that these two echinostomes were genetically distinct, although they share genomic DNA to some extent.

Larval Echinococcus multilocularis was found in Clethrionomys rex in Hokkaido, Japan. C. rex is a new host record for E. multilocularis. The cysts were filled with numerous protoscoleces suggesting a potential role of this vole in a natural cycle of transmission.

Infection of Salamandra salamandra larvae (Amphibia: Urodela) with the fish acanthocephalan Pomphorhynchus laevis was detected in a fish-free mountain brook. Gammarus fossarum was found to be the intermediate host. The parasites were probably inadvertently introduced through fish breeding practices. Evidence was obtained that Pomphorhynchus laevis persists, at least for several months, in postmetamorphic fire salamanders.

Errata

Volume 69 Pages 113–117 For “mm” read “μm” throughout