Investigation of the transcriptomic response in Atlantic salmon (Salmo salar) gill exposed to Paramoeba perurans during early onset of disease.

Amoebic Gill Disease (AGD), caused by the protozoan extracellular parasite Paramoeba perurans (P. perurans) is a disease affecting Atlantic salmon (Salmo salar). This study investigated the gill transcriptomic profile of pre-clinical AGD using RNA-sequencing (RNA-seq) technology. RNA-seq libraries generated at 0, 4, 7, 14 and 16 days post infection (dpi) identified 19,251 differentially expressed genes (DEGs) of which 56.2% were up-regulated. DEGs mapped to 224 Gene Ontology (GO) terms including 140 biological processes (BP), 45 cellular components (CC), and 39 molecular functions (MF). A total of 27 reference pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG) and 15 Reactome gene sets were identified. The RNA-seq data was validated using real-time, quantitative PCR (qPCR). A host immune response though the activation of complement and the acute phase genes was evident at 7 dpi, with a concurrent immune suppression involving cytokine signalling, notably in interleukins, interferon regulatory factors and tumour necrosis factor-alpha (tnf-α) genes. Down-regulated gene expression with involvement in receptor signalling pathways (NOD-like, Toll-like and RIG-1) were also identified. The results of this study support the theory that P. perurans can evade immune surveillance during the initial stages of gill colonisation through interference of signal transduction pathways.

Malpighamoeba infection compromises fluid secretion and P-glycoprotein detoxification in Malpighian tubules.

Malpighian tubules, analogous to vertebrate nephrons, play a key role in insect osmoregulation and detoxification. Tubules can become infected with a protozoan, Malpighamoeba, which damages their epithelial cells, potentially compromising their function. Here we used a modified Ramsay assay to quantify the impact of Malpighamoeba infection on fluid secretion and P-glycoprotein-dependent detoxification by desert locust Malpighian tubules. Infected tubules have a greater surface area and a higher fluid secretion rate than uninfected tubules. Infection also impairs P-glycoprotein-dependent detoxification by reducing the net rhodamine extrusion per surface area. However, due to the increased surface area and fluid secretion rate, infected tubules have similar total net extrusion per tubule to uninfected tubules. Increased fluid secretion rate of infected tubules likely exposes locusts to greater water stress and increased energy costs. Coupled with reduced efficiency of P-glycoprotein detoxification per surface area, Malpighamoeba infection is likely to reduce insect survival in natural environments.

Water-related parasitic diseases in China.

Water-related parasitic diseases are directly dependent on water bodies for their spread or as a habitat for indispensable intermediate or final hosts. Along with socioeconomic development and improvement of sanitation, overall prevalence is declining in the China. However, the heterogeneity in economic development and the inequity of access to public services result in considerable burden due to parasitic diseases in certain areas and populations across the country. In this review, we demonstrated three aspects of ten major water-related parasitic diseases, i.e., the biology and pathogenicity, epidemiology and recent advances in research in China. General measures for diseases control and special control strategies are summarized.

Increased systemic vascular resistance in Atlantic salmon, Salmo salar L., affected with amoebic gill disease.

Previous investigations into the pathophysiology of amoebic gill disease (AGD) have suggested that there are probable cardiovascular effects associated with this disease. In the present study Atlantic salmon, Salmo salar L., were experimentally infected by cohabitation with diseased individuals. Two commonly used vasodilators, sodium nitroprusside (SNP) and captopril, the angiotensin-converting enzyme (ACE) inhibitor, were used as tools to investigate possible vasoconstriction and/or renin-angiotensin system (RAS) dysfunction in AGD-affected animals. Within the SNP trial, results showed that AGD-affected fish exhibited lowered cardiac output (Q), lowered cardiac stroke volume (V(S)) and a significantly elevated systemic vascular resistance (R(S)) compared with non-affected naïve counterparts. These effects were totally abolished following SNP administration (40 microg kg(-1)), however significant cardiovascular effects associated with SNP were not observed. Within the captopril trial, where AGD-affected fish were more diseased compared with the SNP trial, a significant hypertension was observed in AGD-affected fish. Captopril administration (10(-4) mol L(-1) at 1 mL kg(-1)) resulted in a significant drop in dorsal aortic pressure (P(DA)) for both AGD-affected and naïve control fish. In terms of peak individual responses, captopril administration effectively lowered P(DA) in both AGD-affected and naïve control groups equally. The drop in P(DA) following SNP administration however was significantly greater in AGD-affected fish potentially suggesting disease-related vasoconstriction. The lack of significant cardiovascular effects directly associated with both SNP and captopril administrations possibly relate to the 6 h recovery period following surgical procedures. However, while variable, these results do suggest that there are significant cardiovascular effects including vasoconstriction and hypertension associated with AGD.

Cytopathogenicity of acanthamoeba, vahlkampfia and hartmannella: quantative & qualitative in vitro studies on keratocytes.

OBJECTIVES: To compare the cytopathogenicity of Vahlkampfia and Hartmannella clinical isolates with a type culture of Acanthamoeba castellanii. METHODS: The cytopathic effect produced during 24 h co-incubation with cultured keratocytes was assessed at set time intervals. Formal quantative studies involved image analysis of the area of cells remaining after 6 h. The mechanism of cytopathogenicity was elucidated using time-lapse video, light and scanning electron microscopy. The ability to produce cell damage in the absence of physical contact was studied using the transwell apparatus. The role of apotosis was also investigated. RESULTS: All three isolates produced near destruction of the keratocyte monolayer within 24 h, although initial cell destruction was more rapid with Acanthamoeba. For all three genera, the mechanism of cell damage involved physical attack and trogocytosis: cytopathic products were also implicated as cell damage was produced in the absence of physical contact, but apoptosis was not demonstrated. CONCLUSIONS: While the results do not prove that Vahlkampfia and Hartmannella are pathogens, they provide important evidence supporting the thesis that they cause keratitis by demonstrating that their ability to produce a cytopathic effect on keratocytes in vitro is similar in magnitude and mechanism to that of the known pathogen Acanthamoeba castellanii. The mechanisms by which small free-living amoebae produce cell damage is poorly understood. The ability of genera of amoebae other than Acanthamoeba to produce corneal infection remains controversial. In this study, the cytopathogenicity of Vahlkampfia and Hartmannella isolated from a case human keratitis are compared both quantitatively and qualitatively with that to the known pathogen Acanthamoeba castellanii. The results suggest that representatives of each of the 3 genera produce a similar degree of cytopathic effect on keratocytes after 24h of co-incubation and that a combination of physical and chemical factors are responsible.

Seasonal distribution of pathogenic free-living amebae in Oklahoma waters.

Pathogenic free-living amebae cause serious human disease, including infection of the eye and the central nervous system. The purpose of this study was to sample aquatic environments in the Tulsa, Oklahoma, area year-round for the presence of these disease-causing amebae. A total of 34 pathogenic isolates were obtained from 2,016 processed water and swab samples. Pathogenicity was determined by the ability of amebae to cause death in mice after intranasal inoculation. Pathogenic amebae were isolated during every month of the year and were identified as Naegleria australiensis (38%), Acanthamoeba species (35%), N. fowleri (18%), and leptomyxid amebae (9%). Pathogenic leptomyxids have not previously been reported from the environment. The greatest percentage of recovery of pathogens occurred during the spring and autumn. The prevalence of pathogenic free-living amebae in the sampled waters was 1 pathogen/3.4 l water.