Showing papers in "Journal of Helminthology in 1998"

Mitochondrial DNA diversity in nematodes.

Abstract: The relatively small literature on mitochondrial DNA (mtDNA) diversity in nematode species is summarized here. Nematodes show a wide range of overall genetic diversities and population genetic structures. Species-wide levels of diversity correlate strongly with the breeding system and other life cycle features that control effective population size. Obligate outcrossers that parasitize mobile vertebrate hosts are the most diverse, species having hermaphroditic stages are less so, and species having asexual reproductive stages appear even less diverse. Nevertheless, these conclusions are preliminary because there exist so few data on DNA diversity in nematodes. What is needed are more comparative studies using similar sampling designs and the same DNA markers, including nuclear loci and further work with mtDNA.

Prevalence of cystic echinococcosis in camels (Camelus dromedarius) in Libya.

Abstract: In an abattoir study, 514 camels, slaughtered for meat production in different areas of northern Libya were examined for the presence of cystic echinococcosis (CE). In addition, 367 sheep and 184 goats were examined. The overall prevalence of infection with CE was 48% in camels, 15.8% in sheep and 3.8% in goats. The infection rate, number and size of cysts were significantly higher in older camels. In six city abattoirs across northern Libya, i.e. Zawia, Tripoli, El-Khumes, Mesurata, Sirt and Benghazi, the prevalence rate of infection in camels ranged from 38.7% to 55.2%, in comparison with sheep and goat rates which were between 0% and 37.9% and 0% and 8.2%, respectively. In camels, the lungs were the most frequently infected organs (85.4%) with liver cysts occurring at a significantly lower rate (33%). In contrast, the liver was the predominant infected site with prevalence values of 86% and 100% in sheep and goats, respectively. More than 90% of camel hydatid cysts were fertile. The possible role of camels in the transmission of CE in Libya is discussed.

A novel method for the recovery of Toxocara canis in mice

Abstract: Acid-isolating and acid digestion techniques were used to recover the larvae of T. canis from the tissues of mice and the acid-isolating technique in particular proved to be an effective method.

Biological control of Haemonchus contortus infective larvae in ovine faeces by administering an oral suspension of Duddingtonia flagrans chlamydospores to sheep

Abstract: A single oral dose of an aqueous suspension containing 11,350,000 chlamydospores of a Mexican isolate of Duddingtonia flagrans (FTHO-8) given to sheep, resulted in a maximum reduction of 88% (range 86.7-90.4%) of the population of Haemonchus contortus infective larvae in the faeces. The effect of this treatment continued for 4-5 days after administration of the suspension. The possible use of this treatment as a method of control of ovine haemonchosis is discussed.

Morphological and developmental characteristics of Echinococcus granulosus derived from sheep, cattle and camels in Iran.

Abstract: Echinococcus granulosus is widely distributed throughout Iran, where a variety of animals act as intermediate hosts. In this study, the development and morphological characteristics of E. granulosus of sheep, cattle and camel origin were compared and, overall, the characteristics of larval and adult isolates from sheep and cattle, although similar, showed significant differences from those of the camel isolates, especially with respect to the size of rostellar hooks. Differences in the fertility rates of hydatid cyst in sheep, cattle and camel were recorded as 88%, 19% and 70% respectively. In dogs experimentally infected with the three 'strains' of E. granulosus, the rate of development was more rapid in the camel than in the sheep and cattle 'strain'. In addition, adult E. granulosus derived from the camel demonstrate differences in worm length, segmentation and size, shape, number and arrangement of the genitalia when compared with worms derived from sheep and cattle. The epidemiological significance of these findings is discussed in relation to human hydatid infections in Iran.

Helminth fauna of the Iberian lynx, Lynx pardinus.

Abstract: Specimens of 12 helminth species were collected from carcasses of eight Lynx pardinus (Temminck, 1827), a carnivore endemic to the Iberian Peninsula. These species included: Brachylaima sp. (12.5%) (Trematoda); Taenia pisiformis (12.5%), T. polyacantha (25%), T. taeniaeformis (25%) and Mesocestoides litteratus (37.5%) (Cestoda); Eucoleus aerophilus (12.5%), Ancylostoma tubaeforme (12.5%), Toxocara cati (37.5%), Toxascaris leonina (62.5%), Vigisospirura potekhina potekhina (12.5%), Mastophorus muris (12.5%) and Physaloptera praeputialis (12.5%) (Nematoda). The helminth fauna in Iberian lynx is compared with that of L. canadensis and L. rufus in America, and for L. lynx in Eurasia. The potential relationships between the parasitological data and some geographical, historical and dietary factors are discussed.

Descriptive epidemiology of Heligmosomoides polygyrus in Apodemus sylvaticus from three contrasting habitats in south-east England

Abstract: Seasonal fluctuations in the prevalence and intensity of infection with Heligmosomoides polygyrus (Nematoda) were studied in Apodemus sylvaticus (wood mouse, n = 399), sampled from three contrasting habitats in southern England, to test the hypothesis that both intrinsic (host sex, age) and extrinsic (season, site) factors influence parasite burdens. Maximum likelihood techniques based on log linear analysis of contingency tables were employed to generate a minimum sufficient model for prevalence of infection and 3-way ANOVA with negative binomial errors was used to evaluate the relative contribution of the principal factors and their interactions in explaining variation in worm burdens. Host age could not be entered into either statistical model because of some incomplete subsets of data. However, it was evident that in general juvenile mice carried lower worm burdens compared with adults, although these increased towards the winter season. Host sex was not a significant factor, other than in making a contribution to a weak significant interaction between sex and site, arising from male bias in one site and female bias in the remaining two. The principal determinants of variation in worm burden were the extrinsic factors, site and season, with an approximately equal weighting, and their interaction. These effects arose because worm burdens were lower at Dungeness and showed quite different seasonal patterns to the Egham and Isle of Wight sites. We propose that the unique character of the Dungeness habitat was not conducive to optimal transmission of H. polygyrus throughout most of the year (excepting spring) and we suggest possible explanations for these observations.

Resistance of chlamydospores of nematophagous fungi to the digestive processes of sheep in Mexico

Abstract: Following oral administration to sheep, chlamydospores of a Mexican isolate of Duddingtonia flagrans (FTHO-8) survived passage through the digestive tract and subsequently grew on corn meal agar plates. The fungus was able to catch and destroy free-living nematodes and third-stage larvae of Haemonchus contortus added to these plates. Chlamydospores of Arthrobotrys sp. showed a poor resistance to the digestive processes of sheep, although conidia of A. superba survived following oral inoculation in one of two animals.

Different levels of Schistosoma mansoni infection induce changes in drug-metabolizing enzymes

Abstract: Most carcinogens and xenobiotics are metabolized primarily by the mixed function oxidase system which includes cytochrome P450, cytochrome b5, NADPH-cytochrome c reductase and aryl hydrocarbon [benzo(a)pyrene] hydroxylase. The present study investigates the influence of infection with different levels of Schistosorna mansoni cercariae on the hepatic levels of reduced glutathione, glutathione S-transferase and glutathione reductase in addition to the enzymes of mixed function oxidase. Cercariae infection levels of 60, 120, 180, 300 and 600 per mouse increased: (i) the hepatic content of cytochrome P450 by 27%, 38%, 72%, 57%, 48% respectively; (ii) the aryl hydrocarbon hydroxylase activity by 44%, 64%, 76%, 90%, 51% respectively; and (iii) the hepatic level of reduced glutathione by 67%, 83%, 103%, 60%, 38% respectively. The cytochrome b5 content did not change at the lowest level of infection but increased at the other four levels by 45%, 76%, 49% and 38% respectively. The activity of glutathione S-transferase increased at the first three levels by 42%, 40%, 27% respectively and decreased at the last two levels by 28% and 52% respectively. On the other hand, the activity of glutathione reductase did not change at any level, whereas, NADPH-cytochrome c reductase activity decreased at the last two levels by 44% and 54%. The alterations in the activities of phase I & II of drug-metabolizing enzymes as a result of infection with different levels of S. mansoni may thus change the liver's capacity to detoxify many endogenous compounds and may also potentiate the deleterious effects of aromatic hydrocarbons, e.g. benzo(a)pyrene, upon the liver and probably other organs. Such alterations may also change the therapeutic actions of drugs that are primarily metabolized by the P450 system, when administered to patients with schistosomiasis.

Temperature dependent population growth of Gyrodactylus derjavini on rainbow trout, Oncorhynchus mykiss

Abstract: Rainbow trout were experimentally infected with the ectoparasitic monogenean Gyrodactylus derjavini at three temperatures, 5.5 degrees C, 11.6 degrees C and 18.7 degrees C. Subsequently, the infection level was monitored during the following 6 weeks. The population growth was positively correlated with temperature in the initial part of the investigation. At 18.7 degrees C growth of the parasite population was fast reaching a peak abundance within 3 weeks, whereafter the infection level decreased significantly. Peak abundance was recorded in week 5 at 11.6 degrees C. A very slow but steady parasite reproduction was noted at 5.5 degrees C, but no peak abundance was reached within 6 weeks. The decline in parasite population after reaching peak levels is likely to be caused by a host response. The host response is also indicated by the parasites' active selection of particular microhabitats. This anti-monogenean response developed fastest at 18.7 degrees C, more slowly at 11.6 degrees C and was not recorded within 6 weeks at 5.5 degrees C.

Epidemiology of trichinellosis in lynx in Finland.

Abstract: Three hundred and twenty seven European lynx (Lynx lynx) were examined for Trichinella sp. larvae using the muscle digestion method. The animals were of both sexes, various ages, and collected between 1989 and 1994 in different locations in Finland. Forty percent of them (132) were found to be infected. Infection was overdispersed, so that the majority of infected lynx only harboured small amounts of larvae, while a minority had higher densities of infection, but never significantly exceeding 40 larvae per gram of muscle (lpg). The median density of infection was 1.04 lpg. To find factor statistically associated with the risk of infection, multivariate logistic regression analysis was performed. Male sex, increasing age, and the density of raccoon dog population in the area were all significantly associated with infection. However, the association with age was not linear and prevalence did not increase after middle age. The mean density of infection decreased slightly with age. The association with the density of the raccoon dog population leads to a tentative hypothesis that the raccoon dog might be an important reservoir of sylvatic trichinellosis in Finland.

Intestinal helminth communities in the green lizard, lacerta viridis, from bulgaria

Abstract: A data set comprising individual host/parasite lists from 100 Lacerta viridis (Reptilia: Lacertidae) belonging to four isolated populations in Bulgaria was studied. A total of seven helminth species was recovered (Leptophallus nigrovenosus, Plagiorchis molini, Oswaldocruzia filiformis, Spauligodon extenuatus, Skrjabinelazia hoffmanni, Physaloptera clausa and Mesocestoides sp.). Lacerta viridis is a new host record for the first five of these species. Communities of intestinal helminths of L. viridis consist of a few species which resulted in a low species richness, abundance and diversity of infracommunities, which exhibit substantial homogeneity among the four samples. A similar pattern of dominance of two nematode species leading to a relatively high community similarity at both infra- and component community levels was observed. While intestinal helminth communities in lizards from ‘marginal’ habitats were dominated by the host generalist, O. filiformis, those in hosts from ‘typical’ habitats were dominated by the lizard specialist S. extenuatus. The results indicate that the characteristics of the host's habitat are important in determining the composition rather than structure of intestinal helminth communities in L. viridis.

Nematode population genetics.

Abstract: Population genetics seeks to understand the genetic relationships within and between populations of a species and the processes that generate these patterns. Little is known about the population genetics of parasitic nematodes. This is a notable gap in our knowledge since understanding the population genetic patterns and processes of parasitic nematodes has profound implications for our ability to fully understand this important group of pathogens. For example, it is only possible to begin to understand how a parasite population will respond to an imposed selection pressure (such as an anthelmintic drug, a vaccine, or resistant hosts) when the population genetic structure and patterns of gene flow of that population is known. Equally, the epidemiology of many nematode parasites is well known empirically and theoretically, yet this epidemiological information is of limited use without a good understanding of the genetic structure of those populations (Anderson & May, 1992).

Larval trematode infections in freshwater gastropods from the Albufera Natural Park in Spain

Abstract: Malacological samplings were made from January 1994 to December 1996 in the Albufera Natural Park (Valencia, Spain) to trace the dynamics of molluscan populations and the prevalence and intensity of infection by larval trematodes. A total of 10,533 freshwater gastropods belonging to seven species (Lymnaea auricularia, L. truncatula, L. palustris, L. peregra, Bithynia tentaculata, Physa acuta and Gyraulus chinensis) was examined, and 110 (1.04%) were found to harbour some of the nine distinguishable types of cercariae, namely four echinostome cercariae (Hypoderaeum conoideum, Echinoparyphium recurvatum, Euparyphium albuferensis, and Echinostoma sp.), four furcocercous cercariae, and one xiphidiocercous cercaria. This study shows that the composition of the snail and trematode communities may be determined by the particular environmental conditions present and the human intervention in the area.

Composition and diversity of helminth communities in eels Anguilla anguilla in the River Tiber: long-term changes and comparison with insular Europe

Abstract: Most studies of helminth communities in the European eel Anguilla anguilla have been undertaken in the British Isles, and there are very few analyses of community composition and structure from continental Europe. To fill this gap and test the hypothesis that helminth communities in freshwater eels in the British Isles are not typical of those of continental Europe, helminth communities of eels in the River Tiber below Rome were analysed by season using data collected in 1980 and new data from 1996. The intestinal helminth communities in the Tiber eels were species poor and characterized by low diversity. Most eels harboured one or no parasite species and communities were heavily dominated by the acanthocephalan Acanthocephalus clavula. Intestinal helminth infracommunity richness and diversity did not differ between seasons within a year or between the same seasons in 1980 and 1996, although some changes in composition were apparent. Intestinal infracommunities from Tiber eels were very similar in characteristics to those analysed from the British Isles, and their temporal changes also showed close similarities to those reported from rivers in the UK. It seems likely therefore that conclusions derived from British studies can be applied to helminth communities of eels on the continent.

Characterization of Fasciola hepatica redial generations by morphometry and chaetotaxy under experimental conditions

Abstract: Morphometric and chaetotactic studies were carried out on the body and cephalic regions of the rediae of Fasciola hepatica (Trematoda: Fasciolidae) in order to precisely identify the different redial generations of this trematode in Lymnaea truncatula under experimental infection. At day 49 post-exposure at 20 degreesC, the length of the redia was significantly higher in the first group of the first generation (R1a) compared with successive generations, R1b, R2a and R2b/R3a. The width of the body was similar in the R1a, R1b, and R2a rediae, but was significantly lower in the R2b/R3a groups. The intrapharyngeal cavity of R1a rediae was significantly wider compared with the R1b, R2a, and R2b/R3a groups, whereas the pharyngeal wall was significantly thicker in the R2b/R3a rediae compared with the R1b and R2a groups. Four other measurements, namely the maximum length and width of the pharynx, diameter of the mouth, and width of intestine, also showed significant variations in relation to pharyngeal morphology and age of infection. Discriminant analysis based on these measurements demonstrated that 98% of the rediae were readily categorized into the four groups identified. The number of perioral sensillae ranged from 126 to 160 but a significant difference was only noted between the mean values of the first generation and those of the group R2b/R3a. From these parameters, the maximum width of the pharyngeal lumen was found to be the best characteristic in the identification of the redial generations.

Parasites in paradise: patterns of helminth distribution in hawaiian stream fishes

Abstract: Of the 13 species of helminths that parasitize stream fishes in Hawai'i, seven species are considered to be native to the archipelago and the remaining six species to be introduced by man. Sources of colonization for native species are piscivorous birds for three species, and marine fishes for four species. Non-native helminths have been brought to Hawai'i in association with the importation of parasitized exotic species of poeciliids introduced into streams for mosquito control and as aquarium releases. Many of these introduced parasites have broad host specificity and now infect the five species of native gobioid stream fishes. Exotic parasites, including a roundworm Camallanus cotti , a tapeworm Bothriocephalus acheilognathi and a leech Myzobdella lugubris , are more widely distributed among Hawaiian streams than are native species.

The structuring process of the macroparasite community of an experimental population of cichlasoma urophthalmus through time

Abstract: The structuring process of the macroparasite community of caged Cichlasoma urophthalmus was studied over time using sentinel fish. Three thousand uninfected cichlids were stocked in floating cages introduced into a quarry in which a wild population of the same species was present. Caged and wild cichlids were sampled monthly over 6 and 7 months, respectively. Seventeen macroparasite species were found in the wild C. urophthalmus population, ten of which were detected in the caged population after 6 months. Early infections were by those species that were more frequent and abundant in the wild population, while helminths with a low prevalence and abundance in the wild appeared later in the caged fish population. The results suggested that the structuring process of the macroparasite community of caged C. urophthalmus followed a predictable pattern, in which those species that were most frequent and abundant in the wild were the first to establish in sentinel fish.

Evaluation of excretory/secretory products of larval Taenia solium as diagnostic antigens for porcine and human cysticercosis

Abstract: Excretory/secretory antigens (ES) of larval Taenia solium were obtained by maintaining the bladder worms in Medium 199 for 3 days. Analysis by SDS-PAGE showed that ES antigens consisted of at least 19 polypeptides, with M(r) ranging from 14-116 kDa. Analytical isoelectric focusing revealed eight bands with acidic pI. An immunocytolocalization study using the peroxidase method demonstrated the presence of ES epitopes on the tegument of the wall of the spiral canals of bladder worms. The specificity of ES antigens was evaluated by EITB, ELISA and FAST-ELISA using antisera against the common parasites of Chinese pigs and man. ES antigens cross-reacted with the antiserum against larval T. hydatigena of pigs. However, these antigens were generally more specific in diagnosing human cysticercosis. Three host-like molecules with molecular masses 43, 58 and 66 kDa were present in the ES products.

Histochemical glycogen and neutral lipid in Echinostoma trivolvis cercariae and effects of exogenous glucose on cercarial longevity

Abstract: Histochemical glycogen and neutral lipid studies were conducted on Echinostoma trivolvis cercariae maintained in artificial spring water (ASW) at 24-25 degrees C for up to 24 h after emergence from host snails. Treatment of whole cercariae by the periodic acid Schiff (PAS) reagent with or without 1% malt diastase showed that cercariae depleted glycogen mainly from the tail by 6 to 24 h postemergence. The posterior tip of the tail remained PAS positive and diastase fast suggesting the presence of mucopolysaccharides there. Fresh cercariae or those stained up to 24 h postemergence with Oil Red O showed the presence of neutral lipid droplets in the excretory system. There was no discernible difference in the size, abundance, or distribution of these droplets in fresh or aged cercariae. Cercariae maintained in ASW plus 1% glucose for 12 or 23 h showed no evidence of resynthesizing glycogen. Nevertheless, cercariae survived longer in 1% glucose than in either 0.0, 0.1 or 0.5% glucose; but only at 23 h were any differences statistically greater (one way ANOVA, P < 0.05).

Some histochemical characteristics of the mucous microenvironment in four salmonids with different susceptibilities to gyrodactylid infections

Abstract: Skin mucous cells and mucus from four salmonids (rainbow trout, brown trout, Conon salmon, Iijoki salmon) with different susceptibilities to infection with Gyrodactylus derjavini and G. salaris were partly characterized by cytochemistry, immunoblotting and immunocytochemistry. Mucous cell densities in various fin types were partly correlated with resistance to infection with G. derjavini but not with G. salaris. Lectin binding assays indicated slight differences in carbohydrate composition of mucus from the four salmonids but serum antigens specific for salmonids were found in mucus from all of them. Antisera against salmon immunoglobulin and rainbow trout complement factor C3 reacted with mucus from all of the salmonids but not with mucus from phylogenetically unrelated fish. Antisera raised against ACTH reacted with mucus components from rainbow trout, brown trout and Conon salmon but not with mucus from Iijoki salmon. These findings are discussed in relation to the host specificity of ectoparasites and susceptibility to infection.

Tests on the centrifugal flotation technique and its use in estimating the prevalence of Toxocara in soil samples from urban and suburban areas of Malaysia

Abstract: The influence of soil texture (silt, sand and laterite) and flotation solutions (saturated NaCl, sucrose, NaNO3 and ZnSO4) upon the recovery of Toxocara ova from seeded soil samples with the centrifugal flotation technique was investigated. Soil samples of different texture were artificially seeded with Toxocara spp. ova and subjected to a centrifugal flotation technique which used various flotation solutions. The results showed significant (P<0.001) interactions between the soil types and the flotation solutions. The highest percentage of ova recovery was obtained with silty soil (34.9−100.8%) with saturated NaC1 as the flotation solution (45.3−100.8%). A combination of washing of soil samples with 0.1% Tween 80, and flotation using saturated NaCl and a 30 min coverslip recovery period was used to study the prevalence of contamination of soil samples. Forty-six soil samples were collected from up to 24 public parks/playgrounds in urban areas of Petaling Jaya and suburban areas of Serdang. The prevalence of Toxocara species in the urban and suburban areas was 54.5% and 45.8% respectively.

Intestinal parasites of the grey fox ( Pseudalopex culpaeus ) in the central Peruvian Andes

Abstract: The intestines of 20 grey Peruvian foxes (Pseudalopex culpaeus) were examined for the presence of Echinococcus granulosus and other intestinal parasites. Echinococcus granulosus was not found in foxes but Taenia hydatigena and T. multiceps were found in 7 and 4 animals respectively. The grey fox may not be a suitable definitive host for E. granulosus. However, it may act as a sylvatic reservoir of T. hydatigena and T. multiceps in the central Peruvian Andes.

Polymorphic DNA markers in the genome of parasitic nematodes

Abstract: Polymorphic molecular markers are being identified to characterize the genomes of parasitic nematodes. The aim is to construct a map with markers evenly spread over the six chromosomes. With such a map, regions can be identified that are under selection pressure when attempts are being made to eradicate worms, be it by drugs, vaccines or genetic resistance in the sheep. Several types of markers have been developed, microsatellites, transposon-associated markers, amplified fragment length polymorphism (AFLP) and expressed sequence tag (EST) markers. Linkage groups can be constructed using several generic crosses between inbred and drug resistant strains. EST markers will be especially important for comparative mapping with the genome of Caenorhabditis elegans, and therefore localization of the linkage group on a chromosome. It will then be possible to identify functional genes close to markers that have changed allele frequencies under selection pressure and identify the mechanisms of resistance to parasite control.

Quantitative characterization of texture used for identification of eggs of bovine parasitic nematodes

Abstract: This study investigates the use of texture, i.e. the grey level variation in digital images, as a basis for identification of strongylid eggs. Texture features were defined by algorithms applied to digital images of eggs from the bovine parasitic nematodes, Ostertagia ostertagi, Cooperia oncophora, and Oesophagostomum radiatum. The resulting data served to establish classification criteria by linear discrimination analysis, and the criteria were subsequently evaluated by cross-validations. From 25 texture features, ten features were selected by their significant discriminatory powers. Using a classification criterion based on these ten texture features, an average of 91.2% of eggs from the three species were correctly classified. All O. radiatum eggs were correctly classified, 11.8% of O. ostertagi and C. oncophora were reciprocally misclassified, and 2.9% of O. ostertagi were identified as O. radiatum. When the ten texture features were used singly an average of 51.2 to 37.9% of the species could be classified correctly. When texture was used together with the shape and size features, a higher percentage of eggs were correctly classified compared with the classification based on either texture, or shape and size. Hence, all O. radiatum were correctly classified as well as 88.3% of O. ostertagi and 91.2% of C. oncophora, resulting in an average of 93.1% correctly classified eggs. The rapid and accurate measurements of texture features may serve as a basis for identification or enhance performance of classification criteria based on egg shape/size.

The ultrastructure of the cuticle and sheath of infective juveniles of entomopathogenic steinernematid nematodes.

Abstract: The ultrastructure of the cuticle of infective juveniles (IJs) of Steinernema carpocapsae (newly emerged and 80-day-old) and newly emerged IJs of S. riobravis, S. feltiae and S. glaseri was examined using transmission electron microscopy. The thickness of four distinctive layers of the cuticle was measured: epicuticle, cortical and median layer, striated layer and fibrous mat. The thickness of the cuticle was correlated with the size of the IJ. In the case of newly emerged IJs, the smallest species, S. carpocapsae, had a cuticle thickness of c. 270 nm compared with c. 460 nm for S. glaseri, the largest of the four species. The overall thickness of the cuticle or the thickness of the cuticle layers was not correlated with the ability of the IJs of the four species to survive desiccation per se. The major difference between newly emerged IJs of the four species was that S. carpocapsae had a proportionately thicker striated layer compared with the other three species. The significance of this is not known but it may be an adaptation involving the nictation behaviour of this species. A substantial change was observed in the cuticle of aged (80-day-old) IJs of S. carpocapsae, whereby the thickness of the cortical and median layer increased by more than 100% and the overall thickness of the cuticle increased by about 50%. Two possible explanations for this increase are: (i) new material was synthesized; or (ii) the fluid content of this layer increased due to an increase in the permeability of the outer layers of the cuticle. The ultrastructure of the sheaths of S. feltiae and S. glaseri was also examined and, apart from S. glaseri having a thicker sheath, the structure of the sheath in both species was similar, with the epicuticle and striated layer still visible.

Population dynamics of and larval trematode interactions with Lymnaea tomentosa and the potential for biological control of schistosome dermatitis in Bremner Bay, Lake Wanaka, New Zealand.

Abstract: Lymnaea tomentosa, the intermediate host of a schistosome which causes schistosome dermatitis in Lake Wanaka, was found to depths of 16 m. The snail recruits in January, lives for up to 21 months, is associated with all water plant species and is found in areas devoid of macroscopic plants. It is host to several trematode species. Avian schistosome infections appear in the spring when echinostome prevalence is low, and a decrease in schistosome prevalence may be correlated with an increase in echinostome prevalence during the summer. A multiple-kind lottery model analysis of parasite species richness implies that interspecific interactions may be occurring in the host snail during the months of December and January.

Analysis of T cell populations and IL-3 mRNA expression in mesenteric lymph node cells and intestinal intraepithelial lymphocytes in Strongyloides ratti-infected mice.

Abstract: T cell populations and IL-3 mRNA expression were analysed in mesenteric lymph node cells and intestinal intraepithelial lymphocytes (IEL) in Strongyloides ratti-infected mice. On days 7 and 12 post-infection, 2.6 times as many mesenteric lymph node cells were present in S. ratti-infected mice compared with uninfected mice. Although the percentages of CD3+, CD4+ and CD8+ cells decreased during infection, the absolute numbers of these cell types increased on day 7 due to an overall increase in the mesenteric lymph node cell number. The CD4/CD8 ratio in IEL was increased on day 5, whereas no significant change in the CD4/CD8 ratio was observed in the mesenteric lymph node cells. Expression of IL-3 mRNA, which is an important cytokine for the induction of murine mucosal mastocytosis and S. ratti-expulsion, was examined in mesenteric lymph nodes and IEL of uninfected and infected mice. IL-3 mRNA was detected in mesenteric lymph nodes of S. ratti-infected mice but not detected in the lymph nodes of uninfected mice. IL-3 mRNA was detected in IEL from both infected and uninfected mice with an 20-fold increase in expression in IEL of infected mice. Overall, IL-3 mRNA levels were higher in IEL than in mesenteric lymph nodes following S. ratti-infection. Expression of IL-4, IL-10, stem cell factor (SCF or c-kit ligand) and IFN-gamma mRNA was also examined in these two tissues. IL-10 mRNA was not detected in any tissue examined and IFN-gamma mRNA levels were unaltered as a result of an S. ratti-infection. Elevated expression of mRNA for SCF (5-fold) and IL-4 (20-fold) was observed in the mesenteric lymph nodes of infected mice. In contrast, SCF mRNA levels were similar in IEL of uninfected and infected animals and only a modest increase in IL-4 mRNA was observed in IEL of infected mice.

Plagiorchis muris: recovery, growth and development in albino rats.

Abstract: Metacercariae of Plagiorchis muris, obtained from naturally infected dragonflies, Sympetrum eroticum, successfully established in 4-week-old albino rats up to 14 days post-infection (p.i.) but by day 28 p.i. the recovery rate had significantly decreased. The genital primordia in excysted metacercariae were differentiated into those of metraterm, Mehlis' gland, ovary and cirrus pouch, with the primordial testes appearing on day 1 p.i. The vitellaria and eggs in the uterus were present in flukes on days 2 and 4 p.i., respectively. Mature flukes were established in the lower part of the small intestine on day 5 p.i., with the peak of egg production occurring on day 14 p.i. Growth of the flukes continued up to day 28 p.i.

Comparison of the trapping ability of Arthrobotrys robusta and Monacrosporium gephyropagum on infective larvae of Strongyloides papillosus.

Abstract: In an in vitro trial, the trapping ability of Arthrobotrys robusta and Monacrosporium gephyropagum against Strongyloides papillosus infective larvae on corn meal agar plates, was evaluated after seven days of interaction at 25 degrees C. Monacrosporium gephyropagum trapped 93.1% of the larvae whereas A. robusta trapped only 32.3%. Variability in the capture of S. papillosus infective larvae by both trapping fungi is discussed.