Strigea robusta (Digenea: Strigeidae) infection effects on the gonadal structure and limb malformation in toad early development

The anomaly P is a mass morphological anomaly reported in some water frog populations across Europe. It was found that polydactyly is only a mild attenuated form of heavy cases of the anomaly P syndrome, which have strong deformations of the hindlimbs and, partly, forelimbs. It was shown that the anomaly P is caused by the trematode Strigea robusta and this syndrome can be considered as a special case of strigeosis in amphibians. The anomaly P for a long time considered to be specific for water frogs of the genus Pelophylax. Herein, we describe polydactyly and heavy forms of the anomaly P syndrome in toads of the genera Bufo and Bufotes, as a result of exposure to S. robusta cercariae. A total of 150 tadpoles of Bufo bufo, 60 tadpoles of Bufotes viridis, and 60 tadpoles of Bufotes baturae were divided into five experimental and four control groups (30 tadpoles in each group). All anomalies in the toads were similar to those observed in water frogs. The survival of tadpoles in the experimental groups was 76%. The anomaly P was observed in 57.9% of toad tadpoles (51.8% of mild forms and 6.1% of heavy forms). The occurrence of the anomaly P varied among groups from 19% to 78%. Heavy forms of the anomaly P were found in all experimental groups. We described rare asymmetrical cases of the anomaly P. According to severe modification of limb morphology, we supposed changes of gonadal morphology (any modifications of the germ and somatic cells). The gonadal development of infected tadpoles was however the same as in uninfected toad tadpoles, and heterochromatin distribution within gonocytes had no differences as well. It seems like the parasite doesn't have any effect on the gonadal development of the toads. The lack of heavy forms in natural populations of toads, as well as a development of gonads were discussed.

Redescription of Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Nematoda: Philometridae), a gonad-infecting parasite of the red grouper Epinephelus morio (Serranidae) in the Gulf of Mexico

The insufficiently known nematode species Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Philometridae) is redescribed based on light and scanning electron microscopical (SEM) examinations of specimens collected from the gonad of the type host, the red grouper Epinephelus morio (Valenciennes) (Serranidae, Perciformes), in the northern Gulf of Mexico off Florida, USA. Also, new prevalence data for females of P. margolisi were derived from 188 fish, and a subset of these (n = 38) were used to determine prevalence and intensity of male nematodes. The male of this species was studied with SEM for the first time, which revealed some new, taxonomically important morphological features. The male posterior end had a V-shaped caudal mound, four pairs of minute adanal papillae, a pair of large papillae located posterior to the cloacal aperture and a pair of very small phasmids. The distal end of the gubernaculum is unique among all gonad-infecting species of Philometra parasitizing serranids in that its ventral surface is flat, smooth, without the usual two longitudinal grooves; the dorsal lamellate structures on the gubernaculum are also different in this species. In contrast to data in the original species description, the body length of gravid females of P. margolisi was 132-280 mm. Overall prevalence for male nematodes (76.3%) was much higher than for females (15.4%), and female nematode prevalence was higher in samples collected during host spawing season than out of season (27.1% and 3.3%, respectively).

Trypanosoma brucei gambiense Infections in Mice Lead to Tropism to the Reproductive Organs, and Horizontal and Vertical Transmission

Trypanosoma brucei gambiense, transmitted by the tsetse fly, is the main causative agent of Human African trypanosomosis in West Africa and poses a significant health risk to 70 million people. Disease progression varies depending on host immunity, but usually begins with a haemo-lymphatic phase, followed by parasite invasion of the central nervous system.

In the current study, the tropism of T. b. gambiense 1135, causing a low level chronic ‘silent’ infection, was monitored in a murine model using bioluminescence imaging and PCR. A tropism to the reproductive organs, in addition to the central nervous system, after 12–18 months of infection was observed. Bioluminescent analysis of healthy females crossed with infected males showed that 50%, 62.5% and 37.5% of the female mice were subsequently positive for parasites in their ovaries, uteri and brain respectively. Although PCR confirmed the presence of parasites in the uterus of one of these mice, the blood of all mice was negative by PCR and LAMP. Subsequently, bioluminescent imaging of the offspring of infected female mice crossed with healthy males indicated parasites were present in the reproductive organs of both male (80%) and female (60%) offspring.

These findings imply that transmission of T. b. gambiense 1135 occurs horizontally, most probably via sexual contact, and vertically in a murine model, which raises the possibility of a similar transmission in humans. This has wide reaching implications. Firstly, the observations made in this study are likely to be valid for wild animals acting as a reservoir for T. b. gambiense. Also, the reproductive organs may act as a refuge for parasites during drug treatment in a similar manner to the central nervous system. This could leave patients at risk of a relapse, ultimately allowing them to act as a reservoir for subsequent transmission by tsetse and possibly, horizontally and vertically.

Human African trypanosomosis (HAT) caused by Trypanosoma brucei gambiense is a serious disease threatening 70 million people in West Africa. The parasite is transmitted by the tsetse fly, and initially multiplies in the bloodstream of the mammalian host, before progressing to the central nervous system. Using a strain of T. b. gambiense transfected with a gene for luminescent detection that causes a chronic infection with very low parasitaemia, we found that the parasite is capable of entering the reproductive organs of both male and female mice. Subsequently, crossing infected male mice with healthy females resulted in some female mice becoming infected. Furthermore, female mice infected directly with T. b. gambiense parasites and crossed with healthy males, produced offspring which were also shown to be positive for parasites. These experiments demonstrated that T. b. gambiense 1135 is transmitted both horizontally, most probably by sexual contact, and vertically in mice. If these alternate modes of transmission are analogous to the situation in humans, this has drastic implications for future control measures of HAT as parasites may avoid the immune system and treatment by accumulating in the reproductive organs as well as the CNS.

Is an Apicomplexan Parasite Responsible for the Collapse of the Iceland Scallop (Chlamys islandica) Stock?

Due to the total and unexpected collapse of the Iceland scallop, Chlamys islandica, stocks around Iceland during the 2000s, a commercial fishing ban has been imposed on this valuable resource since 2003. Following the initial identification of an apicomplexan parasite in the scallops, a long-term surveillance program was established to evaluate the effect of the parasite on the population. The infections were highly prevalent in all shell sizes throughout the study. However, the parasite only impacts mature scallops where they cause severe macroscopic changes, characterized by an extensively diminished and abnormally coloured adductor muscle. A highly significant relationship was observed between infection intensity and gonad and adductor muscle indices. The first four years of the study, were characterized by high infection intensity and very poor condition of the adductor muscle and gonads, whilst during subsequent years, infections gradually decreased and the condition of the scallops improved. Histopathological changes were restricted to the presence of apicomplexan zoites which were widely distributed, causing varying degrees of pathology in all organs. In heavy infections, muscular and connective tissues were totally necrotized, destroying significant parts of numerous organs, especially the adductor muscle, digestive gland and gonads. The progression of the disease was in good synchrony with the mortality rates and the subsequent decline observed in the scallop stock and recruitment indices. Our findings strongly suggest that the apicomplexan parasite played a major role in the collapse of the Iceland scallop stock in Breidafjordur. In addition to causing mortality, the infections significantly impact gonad development which contributes further to the collapse of the stock in the form of lower larval recruitment. Furthermore, compelling evidence exists that this apicomplexan pathogen is causing serious disease outbreaks in other scallop populations. Similar abnormal adductor muscles and the parasite itself have been identified or observed in association with other mass mortality events in several different scallop species and commercial stocks in the northern hemisphere.

First molecular identification of Ascocotyle (Phagicola) longa in its first intermediate host the mud snail Heleobia australis

This is the first study that used species-specific DNA primers to confirm the presence of the heterophyid Ascocotyle (Phagicola) longa Ransom, 1920 in its first intermediate host. The larval stages (rediae and cercariae) of this parasite were morphologically and genetically identified in the gonad of the intertidal mud snail Heleobia australis (d'Orbigny, 1835) (Cochliopidae) in the Bahía Blanca estuary, Argentina. In addition, we asked whether the prevalence in H. australis varied between seasons. Mullets - the second intermediate host of this heterophyid - migrate in estuaries during the warmer seasons and it is expected that piscivorous birds and mammals - the definitive hosts - prey more intensively on this species at those times. Thus, the number of parasite eggs released into the tidal flat within their feces should be higher, thereby increasing the ingestion of the parasite by H. australis.We therefore expected a higher prevalence of A. (P.) longa in H. australis in the Bahía Blanca estuary during spring and summer than autumn and winter. We found that 16 out of 2,744 specimens of H. australis had been infected with A. (P.) longa (total prevalence of 0.58%). Nonetheless, the prevalence showed no significant variation between seasons. Hence, we discuss an alternative scenario where the lack of seasonal changes might be mostly related to the permanent residence of definitive hosts in the estuary and not to the seasonal recruitment of mullets. Finally, we highlight the need for more experimental and comparative approaches in order to understand the diagnosis and geographical distribution of this worldwide heterophyid.

Detection of a parasitic amoeba (Order Dactylopodida) in the female gonads of oysters in Brazil

The impacts of oocyte parasites on the reproductive success of molluscs are largely unknown. In this study, we evaluated the presence of gonad parasites in 6 species of marine bivalve molluscs native to southern Brazil. Cultured bivalves included the mangrove oyster Crassostrea gasar (sometimes called C. brasiliana), the brown mussel Perna perna, the lion's paw scallop Nodipecten nodosus and the wing pearl oyster Pteria hirundo. Another species of mangrove oyster, C. rhizophorae, and the carib pointed venus clam Anomalocardia brasiliana (syn. A. flexuosa) were collected from the wild. Molluscs were collected in winter 2009 and summer 2010 for histopathological and molecular evaluation. An unknown ovarian parasite (UOP) was observed in histopathological sections of female gonads of C. gasar and C. rhizophorae. The UOP possessed features suggestive of amoebae, including an irregular outer membrane, frothy cytoplasm, a nucleus with a prominent central nucleolus and a closely associated basophilic parasome. PCR analysis was negative for Marteilioides chungmuensis, Perkinsus spp. and Paramoeba perurans. However, real-time PCR successfully amplified DNA from oyster gonads when using universal Paramoeba spp. primers. Also, conventional PCR amplified DNA using primers specific for Perkinsela amoebae-like organisms (syn. Perkinsiella), which are considered as endosymbionts of Parameoba spp., previously thought to be the parasome. Our results suggest that this UOP is a species of amoeba belonging to 1 of the 2 families of the order Dactylopodida, possibly related to Paramoeba spp. This study represents the first report of this type of organism in oysters. We found that C. gasar and C. rhizophorae were the most susceptible molluscs to these UOPs.

Different host exploitation strategies in two zebra mussel-trematode systems: adjustments of host life history traits

The zebra mussel is the intermediate host for two digenean trematodes, Phyllodistomum folium and Bucephalus polymorphus, infecting gills and the gonad respectively. Many gray areas exist relating to the host physiological disturbances associated with these infections, and the strategies used by these parasites to exploit their host without killing it. The aim of this study was to examine the host exploitation strategies of these trematodes and the associated host physiological disturbances. We hypothesized that these two parasite species, by infecting two different organs (gills or gonads), do not induce the same physiological changes. Four cellular responses (lysosomal and peroxisomal defence systems, lipidic peroxidation and lipidic reserves) in the host digestive gland were studied by histochemistry and stereology, as well as the energetic reserves available in gonads. Moreover, two indices were calculated related to the reproductive status and the physiological condition of the organisms. Both parasites induced adjustments of zebra mussel life history traits. The host-exploitation strategy adopted by P. folium would occur during a short-term period due to gill deformation, and could be defined as "virulent." Moreover, this parasite had significant host gender-dependent effects: infected males displayed a slowed-down metabolism and energetic reserves more allocated to growth, whereas females displayed better defences and would allocate more energy to reproduction and maintenance. In contrast, B. polymorphus would be a more "prudent" parasite, exploiting its host during a long-term period through the consumption of reserves allocated to reproduction.

Meagre Argyrosomus regius (Osteichthyes) as host of a gonad-infecting species of Philometra (Nematoda: Philometridae) off the Atlantic coast of Portugal

Subgravid females (up to 439 mm long) of the nematode Philometra sp. were found in meagre Argyrosomus regius (Asso, 1801) (Sciaenidae: Perciformes) off the southern Atlantic coast of Portugal in 2006. The general morphology of these nematodes somewhat resembles that of Philometra lateolabracis (Yamaguti, 1935), but the gravid females of the species from A. regius are apparently much longer. This is the first documented record of a gonad-infecting species of Philometra in marine fishes off the Atlantic coast of Europe. The possible importance of the gonad-parasitizing Philometra spp. as pathogens of marine fishes is stressed.

Evidence for sex ratio distortion by a new microsporidian parasite of a Corophiid amphipod

In this paper, we describe the occurrence of a microsporidian parasite in female-biased populations of an intertidal amphipod,Corophium volutator(Pallas), at mudflat sites in the Bay of Fundy, Canada. Sequence data for the parasite's 16S rDNA indicate that it is a novel microsporidian species. This parasite was found principally in female host gonads, indicating that it might be a vertically transmitted, sex-distorting microparasite. At 4 sites each sampled in early and mid-summer, parasite prevalence varied from 0 to 21%. In the lab, infected mothers gave rise to more female-biased broods, than did uninfected mothers. Infection was not associated with size of females or with lowered survivorship of their young. Surprisingly, infected mothers actually had higher fertility controlling for body length than did uninfected mothers. Taken together, our results suggest that this novel microsporidian is likely a feminizing microparasite and is a contributing factor to local and widespread sex ratio distortion inC. volutator.

Alternative life-history and transmission strategies in a parasite: first come, first served?

Alternative transmission strategies are common in many parasitic organisms, often representing discrete phenotypes adopted in response to external cues. The facultative truncation of the normal 3-host life-cycle to a 2-host cycle in many trematodes provides an example: some individuals mature precociously, via progenesis, in their intermediate host and produce eggs without the need to reach a definitive host. The factors that determine how many and which individuals adopt the truncated life-cycle within a parasite population remain unknown. We investigated the occurrence of progenesis in the trematode Stegodexamene anguillae within its fish intermediate host. Location within the host was a key determinant of progenesis. Although the size and egg output of progenetic metacercariae encysted in host gonads did not differ from those of the few progenetic metacercariae in other host tissues, the likelihood of metacercariae becoming progenetic was much higher for those in the gonads than those elsewhere in the host. Progenetic parasites can only evacuate their eggs along with host eggs or sperm, providing a link between the parasite's transmission strategy and its location in the host. Host size and sex, and the presence of other parasite species in the host, did not affect the occurrence of progenesis in S. anguillae. However, the proportion of metacercariae in host gonads and the proportion of progenetic metacercariae both decreased with increasing numbers of S. anguillae per host. These results suggest that progenesis is adopted mostly by the parasites that successfully establish in host gonads. These are generally the first to infect a fish; subsequent arrivals settle in other tissues as the gonads quickly become saturated with parasites. In this system, the site of encystment within the fish host both promotes and constrains the adoption of a facultative, truncated life-cycle by the parasite.

Reinstatement of Philometra jordanoi (López-Neyra, 1951) (Nematoda:Philometridae): a parasite of the Mediterranean dusky grouper Epinephelus marginatus (Lowe) (Osteichthyes, Serranidae)

Morphological examination of a single male philometrid nematode, recovered from the ovary of a dusky grouper Epinephelus marginatus caught off the north-east Mallorca (western Mediterranean), revealed morphological differences between this specimen and philometrid males from the gonads of other marine fish hosts. These differences, together with discrepancies between the descriptions of philometrid females found in the gonads of Mediterranean E. marginatus and those described to date in various hosts and/or seas, lead us to propose that Philometra jordanoi (López-Neyra, 1951) should be reinstated as a species parasitic in the gonads of the Mediterranean dusky grouper. The male of P. jordanoi is described for the first time.

Phylogenetic relationships of three new microsporidian isolates from the silkworm, Bombyx mori

The pathogenicity, mode of transmission, tissue specificity of infection and the small subunit rRNA (SSU-rRNA) gene sequences of the three new microsporidian isolates from the silkworm Bombyx mori were studied. Out of the three, NIK-2r revealed life cycle features and SSU-rRNA gene sequence similar to Nosema bombycis, suggesting that it is N. bombycis. The other two, NIK-4m and NIK-3h, differed from each other as well as from N. bombycis. NIK-4m was highly pathogenic and did not show any vertical transmission, in accordance with the apparent lack of gonadal infection, whereas NIK-3h was less pathogenic and vertical transmission was not detected but could not be excluded. Phylogenetic analysis based on SSU-rRNA gene sequence placed NIK-3h and NIK-4m in a distinct clade that included almost all the Vairimorpha species and Nosema species that infect lepidopteran and non-lepidopteran hosts, while NIK-2r was included in a clade containing almost all the Nosema isolates that infect only lepidopteran hosts. Thus, we have presented molecular evidence that one of the three isolates is in fact the type species N. bombycis, while the other two isolates are Vairimorpha spp. There was distinct separation of microsporidian isolates infecting only lepidopteran hosts and those infecting lepidopteran and non-lepidopteran hosts, reflecting possible co-evolution of hosts and microsporidian isolates.

Helminth parasites of Girardinichthys multiradiatus (Pisces: Goodeidae) in the upper Lerma River sub-basin, Mexico

Thirteen helminth species were recorded during a helminthological examination of 754 Girardinichthys multiradiatus (Meek) (Pisces: Goodeidae) collected from 20 localities in the upper Lerma River sub-basin on the highland plateau of Mexico. The study constitutes a complete and extensive inventory of the helminth parasites of this freshwater fish species across its entire current geographic distribution. The collected species included one adult trematode, three metacercariae, one monogenean, one adult cestode, three metacestodes, three nematode larvae and one cystacanth. The records of the metacercariae of Tylodelphys sp. and Ochetosoma brevicaecum, the larvae of the nematodes Contracaecum sp. and Falcaustra sp. and the cystacanth of Polymorphus brevis are all new records for G. multiradiatus. The metacercariae of Tylodelphys sp. were the most widespread and prevalent species in the sample, being collected from 15 of the 20 sampling localities, with a prevalence of 3.2-72.2%. The data indicate the helminth parasite community of G. multiradiatus to be relatively poor when compared with the helminth communities of freshwater fish from other parts of Mexico. This community is subject to colonization by generalist helminth species, mostly transported by birds. A further component of this community consists of helminth species that have been introduced anthropogenically.

Parasitic castration of Eurhomalea lenticularis (Bivalvia: Veneridae) by a digenetic trematode: quantitative histological analysis

The clam Eurhomalea lenticularis may be parasitized by digenean trematodes of the family Plagiorchidae, specifically in the gonads (parasitic castration). A quantitative histological analysis of the parasitized gonads demonstrated a significant decrease in gonadal area, in the size of individual acini, and in the numbers of differentiated germ cells compared to unparasitized clams. Castration may be caused by mechanical compression due to trematode sporocyst growth. However, the uniform loss of germ cells in areas without sporocysts suggests that a more generalized mechanism is responsible. We suggest that parasitic castration has a primary effect on the host's neuroendocrine and gametogenic systems that regulate gamete production.

Occurrence of Philometra lateolabracis (Nematoda: Philometridae) in the gonads of marine perciform fishes in the Mediterranean region

Gravid females of the nematode Philometra lateolabracis (Yamaguti, 1935), a parasite of gonads of marine perciform fishes, were found in wild and cultured dusky grouper Epinephelus marginatus (Lowe) from waters near the Balear Islands (Spain, Mediterranean Sea) and Sicily (Italy, Thyrrenean Sea), and in the greater amberjack Seriola dumerili (Risso) in Croatia (south-eastern Adriatic Sea). In wild E. marginatus in Spain, the overall prevalence was 21% and the intensity of infection 1 nematode per fish. The nematodes are briefly described and illustrated. The species Sanguinofilaria jordanoi López-Neyra, 1951, described from the ovary of Epinephelus gigas Brünich from Morocco, is synonymized with P. lateolabracis. This is the first documented record of P. lateolabracis from fishes of the Mediterranean region and its finding in S. dumerili represents a new host record. The possible importance of this pathogenic parasite for cultures of marine perciform fishes in the region is stressed.

A new monorchiid cercaria (Digenea) parasitising the purple clam Amiantis purpurata (Bivalvia: Veneridae) in the Southwest Atlantic Ocean, with notes on its gonadal effect

An unnamed microcercous cercaria (Digenea: Monorchiidae), a parasite of Amiantis purpurata (Lamarck, 1818) (Bivalvia: Veneridae) and its corresponding metacercaria from the province of Buenos Aires and the Patagonian coast of the Southwest Atlantic Ocean, are described. The cercaria described in this paper differs from the three other monorchiid microcercous cercariae, i.e., Lasiotocus minutus (Manter, 1931), Lasiotocus elongatus (Manter, 1931), and Cercaria caribbea XXXVI Cable, 1956, mainly because of the extension of the excretory vesicle and the location of the ventral sucker. Cercariae artificially extracted from sporocysts encyst in a dish and form metacercariae enveloped by a gelatinous sac with two prolongations, which are used to adhere to the substratum. The monorchiid described in this paper has a life cycle similar to those of L. minutus and L. elongatus, although the adult stage of the present species is still unknown. Their larvae are similar in morphology and have venerid clams as their first hosts. The presence of a monorchiid larva is reported for the first time in the Southern Hemisphere. Its monthly prevalence rates, ranging from 0 to 25% (mean: 8.3%), are given from the Patagonian coast. The infection seems to cause castration as it was observed that during March through to May, when most gametes were produced in uninfected individuals, 81% of the infected individuals did not produce gametes.

Impact of a castrating trematode, Neophasis sp., on the common whelk, Buccinum undatum, in the northern Gulf of St. Lawrence

We observed heavy trematode infections of whelks, Buccinum undatum, from the Mingan Islands, eastern Canada, by larval stages of a species of Neophasis. Only sexually mature whelks were infected, 23% of mature females and 15% of mature males, and prevalence increased rapidly with whelk size. In most cases the parasite completely occupied the gonad, causing castration. The digestive gland was also infected, although to a lesser degree (0% to 50% occupation), and a marked reduction in the mass of the penis was associated with the infection. A decrease in the proportion of whelks with a highly infected digestive gland between May and August 1994 suggested mortality of infected individuals. Whelks held for 12 to 15 months in the laboratory retained the infection but did not show significant mortalities (possibly because food was abundant and predators absent). The larval stage of Neophasis sp. found in whelks was a cercaria; however, the tail easily detached. The putative infective stage (metacercaria) was not observed but may be present in whelks in late winter and early spring. Other trematode parasites observed were adult Steringophorus furciger in the stomach and larval Renicola sp. in the digestive gland.

[Histopathology of Kingiella chilenica (bivalvia, cyamiidae) parasitized by rediae and cercariae of the Gymnophallidae family]

Gonadal and digestive gland tissues of Kingiella chilenica specimens, which were infected with trematode larvae, were examined to determine the organs that are normally invaded by these parasites. Rediae containing cercariae of this digenetic trematod, appeared exclusively restricted to the tissues of the digestive gland. Consequently, no damage or alterations were observed in the gonad or other related tissues of the infected specimens. This, linked to the fact that parasitized females may also appear with brooded embryos, supports the conclusion that the reproductive activities of the bivalve mollusc are not affected by the presence of these infecting larvae.

Schistosoma mansoni: influence of infection on levels of translatable mRNA and on polypeptide synthesis in the ovotestis and albumen gland of Biomphalaria glabrata

Larval trematode infection causes a disruption of normal reproductive activity in the molluscan intermediate host. Because relatively little is known about the dynamics of this host-parasite interaction, the effect of Schistosoma mansoni infection on translatable mRNA pools and on polypeptide synthesis was examined in the ovotestis (OT) and albumen gland (AG) of Biomphalaria glabrata. Total RNA was isolated from OTs and AGs from uninfected control snails and snails at 14, 21, and 28 days postinfection (pi) with 20 S. mansoni miracidia and subjected to a rabbit reticulocyte in vitro translation system. Quantitative densitometry of autofluorograms of one-dimensional SDS-PAGE slab gels revealed reductions in quantities of total proteins synthesized in vitro from RNA isolated from infected OTs at 21 and 28 days pi, but not at Day 14 pi. Similar reductions were seen in 10 individual polypeptides selected for a more detailed analysis. In contrast to the OT, Day 14 pi-infected AGs exhibited an initial increase in total protein synthesized in the in vitro translation system utilized, followed by significant reductions at 21 and 28 days pi. Selective modulation of labeled polypeptides was evident in 11 polypeptides chosen for a more detailed analysis. This general pattern of parasite inhibitory effects was also seen in parallel pulse-chase studies using [35S]methionine metabolic labeling of in vitro-cultured OTs and AGs. In these experiments, significant reductions in the amounts of labeled polypeptides found in culture supernatants at 14, 21, and 28 days pi were evident. Total polypeptide synthesis also was solubilized AGs from infected snails at 21 and 28 days pi. Results indicate that larval trematode infection induced a generalized disruption of polypeptide metabolism in OTs and AGs of B. glabrata. Such inhibition may occur at both the transcriptional and the translational levels and is initially manifested early in infection, during the time that daughter sporocysts begin to migrate and colonize the digestive gland and OT.

The effects of Fasciola hepatica on Lymnaea truncatula

Among the functional changes observed in L. truncatula infected with F. hepatica were those of growth, reproduction and mortality. For the first 3 weeks after infection there was no difference between the growth of infected and uninfected groups of snails. Thereafter there was a temporary accelerated growth which occurred between the fourth and seventh weeks after infection. The onset of this period of rapid growth in the different age groups of infected snails coincided with the time of migration of the rediae into the hepatopancreas. Of more significance was the influence of infection on the reproduction of the snail. There was a sharp decline in oviposition 2–3 weeks after infection, followed by a complete cessation of egg production at the end of the fifth week. Once oviposition ceased, it was not resumed and there was no self-cure. Contrary to general belief, infected groups of L. truncatula have been found to live longer than the uninfected controls. With isolated snails, however, there was a tendency for the uninfected snails to live longer than the infected ones. The possible interpretation of the discrepancies between isolated and mass cultured snails are discussed. The hepatopancreas and the gonad (ovotestis) were the two structures directly affected by the infection. Establishment of the rediae in the hepatopancreas invariably resulted in parasitic castration.

Studies on the course of infection of the poultry cestode Raillietina cesticillus (Molin, 1858) in the definitive host

The course of infection of Raillietina cesticllus in the chicken has been studied and information is presented on proglottid output, the dynamics of infection and the distribution and growth of the cestode. A posterior migration of young cestodes during the first 7 days of infection was confirmed and a progressive destrobilization of the worms was observed with complete destrobilization occurring 70 days after infection. No regeneration of strobilae occurs and the scolices are eventually eliminated. A marked difference in the rate of destrobilization in the two host sexes was noted.