Reproductive and feeding ecology of parasitic gnathiid isopods of epaulette sharks (Hemiscyllium ocellatum) with consideration of their role in the transmission of a haemogregarine

Epaulette sharks Hemiscyllium ocellatum were surveyed on Heron Island, Great Barrier Reef, Australia for gnathiid isopods and protozoan (haemogregarine) parasites to determine the prevalence and intensity of infection and to investigate the potential role of gnathiids as vectors of these haemogregarines, the first such study carried out on elasmobranchs. Juvenile gnathiids were collected and quantified using a novel non-invasive and chemical-free technique and gnathiid squashes were examined for haemogregarine developmental stages. The feeding and reproductive ecology of the Gnathia spp. was investigated to better understand the relationship between gnathiids and haemogregarines. Gnathiids were found on all sharks and intensities ranged between two and 66. Only third-stage gnathiid juveniles were found, which fell into two size groups (A and B). These juveniles remained attached to H. ocellatum for up to 17 days, the longest period of attachment yet recorded for gnathiids. Group A female gnathiids produced broods of 45-187 (median = 120) first stage juveniles from between 54 and 82 days (median = 63 days) after detachment. First stage juveniles survived for an average of 15.8 +/- 0.1 (SEM) days without feeding. The prevalence (6.7%) and parasitaemia (usually

Infracommunity structure of parasites of Hemigymnus melapterus (Pisces : Labridae) from Lizard Island, Australia: The importance of habitat and parasite body size

This Study describes the community of all metazoan parasites from 14 individuals of thicklip wrasse, Hemigymnus melapterus, from Lizard Island, Australia. All fish were parasitized, and 4,649 parasite individuals were found. Twenty-six parasite species were identified although only 6 species were abundant and prevalent: gnathiid isopods, the copepod Hatschekia hemigymni, the digenean Callohelmis pichelinae, and 3 morphotypes of tetraphyllidean cestode larvae. We analyzed whether the body size and microhabitat of the parasites and size of the host affected understanding of the structure of the parasite community. We related the abundance, biovolume, and density of parasites with the host body size and analyzed the abundances and volumetric densities of some parasite species within microhabitats. Although the 2 most abundant species comprised 75% of all parasite individuals, 4 species, each in similar proportion, comprised 85% of the total biovolume. Although larger host individuals had higher richness, abundance, and biovolume of parasites than smaller individuals, overall parasite volumetric density actually decreased with the host body size. Moreover. parasites exhibited abundances and densities significantly different among microhabitats; some parasite species depended on the area available, whereas others selected a specific microhabitat. Parasite and habitat size exhibited interesting relationships that should be considered more frequently. Considerations of these parameters improve understanding of parasite community structure and how the parasites use their habitats.

Azurin of pathogenic Neisseria spp. is involved in defense against hydrogen peroxide and survival within cervical epithelial cells

Laz, a lipid-modified azurin of the human pathogens Neisseria gonorrhoeae and Neisseria meningitidis, is involved in defense against oxidative stress and copper toxicity; laz mutant strains are hypersensitive to hydrogen peroxide and copper. The N. gonorrhoeae laz mutant also has decreased survival in an ex vivo primary human ectocervical epithelial assay.

Identification and characterization of non-pathogenic Fusarium oxysporum capable of increasing and decreasing Fusarium wilt severity

Fusarium wilt of banana is a potentially devastating disease throughout the world. Options for control of the causal organism, Fusarium oxysporum f.sp. cubense (Foc) are limited. Suppressive soil sites have previously been identified where, despite the presence of Foc, Fusarium wilt does not develop. In order to understand some aspects of this disease suppression, endophytic Fusarium oxysporum isolates were obtained from banana roots. These isolates were genetically characterized and compared with an isolate of Fusarium oxysporum previously identified as being capable of suppressing Fusarium wilt of banana in glasshouse trials. Three additional isolates were selected for glasshouse trials to assess suppression of Fusarium wilt in two different cultivars of banana, Cavendish and Lady Finger. One isolate (BRIP 29089) was identified as a potential biocontrol organism, reducing the disease severity of Fusarium wilt in Lady Finger and Cavendish cultivars. Interestingly, one isolate (BRIP 45952) increased Fusarium wilt disease severity on Cavendish. The implications of an isolate of Fusarium oxysporum, non-pathogenic on banana, increasing disease severity and the potential role of non-pathogenic isolates of Fusarium oxysporum in disease complexes are discussed. (c) 2006 Published by Elsevier Ltd on behalf of The British Mycological Society.

Macrophage-specific expression of human lysosomal acid lipase corrects inflammation and pathogenic phenotypes in lal(-/-) mice

Lysosomal acid lipase (LAL) hydrolyzes cholesteryl esters and triglycerides to generate free fatty acids and cholesterol in the cell. The downstream metabolites of these compounds serve as hormonal ligands for nuclear receptors and transcription factors. Genetic ablation of the lal gene in the mouse caused malformation of macrophages and inflammation-triggered multiple pathogenic phenotypes in multiple organs. To assess the relationship between macro phages and lal(-/-) pathogenic phenotypes, a macrophage-specific doxycycline-inducible transgenic system was generated to induce human LAL (hLAL) expression in the lal(-/-) genetic background under control of the 7.2-kb c-fins promoter/intron2 regulatory sequence. Doxycycline-induced hLAL expression in macrophages significantly ameliorated aberrant gene expression, inflammatory cell (neutrophil) influx, and pathogenesis in multiple organs. These studies strongly support that neutral lipid metabolism in macrophages contributes to organ inflammation and pathogenesis.

Pathogenic variation of Fusarium isolates associated with head blight of wheat in Australia

This paper examines the level of pathogenic diversity in Australian Fusarium pseudograminearum and Fusarium graminearum isolates for head blight from the assessment of 51 wheat germplasm lines, barley, triticale, rye, maize and sorghum plants. A set of nine putative wheat differentials were selected and assessed with 10 F. graminearum and 12 F. pseudograminearum isolates. Isolates of both species were pathogenic on all the wheat germplasm lines, barley triticale and rye. The isolates differed largely in a quantitative way with only small differential effects and were statistically demarcated into three pathogenicity groups: low, intermediate and high. Such distribution patterns suggest that wheat germplasm lines employ different resistance mechanisms to each group of isolates and the three pathogenicity groups may have different mechanisms controlling pathogenicity. The aggressiveness of F. graminearum and F. pseudograminearum isolates on the wheat germplasm lines were marginally correlated (r = 0.40). Durum wheats were ranked as the most susceptible while Sumai 3, Ituo Komugi, Sotome A, Sotome and Nobeokabouzu komugi were consistently grouped as resistant by both species. These findings reiterate the need to consider pathogen variability in the screening, selection and improvement of resistance to head blight in wheat.

Transmission mode and distribution of parasites among groups of the social lizard Egernia stokesii

We explored patterns of infection of three apicomplexan blood parasites with different transmission mechanisms in 46 social groups across seven populations of the Australian lizard, Egernia stokesii. There was higher aggregation of infections within social groups for Hemolivia, transmitted by ticks, and Schellackia, either tick-transmitted or directly transmitted from mother to offspring, than for Plasmodium, with more mobile dipteran vectors. Prevalence was not related to group size, proximity to other groups or spatial overlap with adjacent groups for any of the parasites. However, for Hemolivia, groups with higher levels of relatedness among adults had higher parasite prevalence. Living in social groups leads to higher risk of infection for parasites with low transmission mobility. An unanswered question is why so few lizard species tolerate these risks to form stable social aggregations.

Overexpression of Leucyl Aminopeptidase in Plasmodium falciparum Parasites. Target for the antimalarial activity of bestatin

Malaria aminopeptidases are important in the generation and regulation of free amino acids that are used in protein anabolism and for maintaining osmotic stability within the infected erythrocyte. The intraerythrocytic development of malaria parasites is blocked when the activity of aminopeptidases is specifically inhibited by reagents such as bestatin. One of the major aminopeptidases of malaria parasites is a leucyl aminopeptidase of the M17 family. We reasoned that, when this enzyme was the target of bestatin inhibition, its overexpression in malaria cells would lead to a reduced sensitivity to the inhibitor. To address this supposition, transgenic Plasmodium falciparum parasites overexpressing the leucyl aminopeptidase were generated by transfection with a plasmid that housed the full-length gene. Transgenic parasites expressed a 65-kDa protein close to the predicted molecule size of 67.831 kDa for the introduced leucyl aminopeptidase, and immunofluorescence studies localized the protein to the cytosol, the location of the native enzyme. The product of the transgene was shown to be functionally active with cytosolic extracts of transgenic parasites exhibiting twice the leucyl aminopeptidase activity compared with wildtype parasites. In vitro inhibitor sensitivity assays demonstrated that the transgenic parasites were more resistant to bestatin (EC50 64 mu M) compared with the parent parasites (EC50 25 mu M). Overexpression of genes in malaria parasites would have general application in the identification and validation of targets for antimalarial drugs.

Host-specificity of monogenean (platyhelminth) parasites: a role for anterior adhesive areas?

Monogeneans (flatworms) are among the most host-specific of parasites in general and may be the most host-specific of all fish parasites. Specificity, in terms of a restricted spatial distribution within an environment, is not unique to parasites and is displayed by some fungi, insects, birds, symbionts and pelagic larvae of free-living marine invertebrates. The nature of cues, how habitats are recognised and how interactions between partners are mediated and maintained is of interest across these diverse associations. We review some experiments that demonstrate important factors that contribute to host-specificity at the level of infective stages (larvae of oviparous monogeneans; juveniles of viviparous gyrodactylids) and adult parasites. Recent research on immune responses by fish to monogenean infections is considered. We emphasise the critical importance of host epidermis to the Monogenea. Monogeneans live on host epidermis, they live in its products (e.g. mucus), monopisthocotyleans feed on it, some of its products are attractants and it may be an inhospitable surface because of its immunological activity. We focus attention on fish but reference is made to amphibian hosts. We develop the concept for a potential role in host-speciality by the anterior adhesive areas, either the specialised tegument and/or anterior secretions produced by monogeneans for temporary but firm attachment during locomotion on host epithelial surfaces. Initial contact between the anterior adhesive areas of infective stages and host epidermis may serve two important purposes. (1) Appropriate sense organs or receptors on the parasite interact with a specific chemical or chemicals or with surface structures on host epidermis. (2) A specific but instant recognition or reaction occurs between component(s) of host mucus and the adhesive(s) secreted by monogeneans. The chemical composition of fish skin is known to be species-specific and our preliminary analysis of the chemistry of some monogenean adhesives indicates they are novel proteins that display some differences between parasite families and species. (C) 2000 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.