Parasites of winter flounder (Pleuronectes americanus) as an additional bioindicator of stress-related exposure to untreated pulp and paper mill effluent: a 5-year field study.

A study was conducted in a marine inlet to assess the effects of untreated discharges from a pulp and paper mill, a municipality, and industries in western Newfoundland on winter flounder (Pleuronectes americanus), a fish species shown previously to be sensitive to environmental contaminants in sediment. The fish were captured by SCUBA divers about 2 km down-current from the mill discharging effluent containing resin acids, and at three reference sites 2 to 11 km away near the opposite shore, each spring in five consecutive years and the fish were necropsied on site. A total of 360 and 339 flounder were examined near the mill and references sites, respectively. Several bioindicators were used to assess fish health including parasites. More fish exhibiting external and microscopic lesions in several tissues, lower condition factors, elevated hepatosomatic index, and delayed reproductive development were observed in samples taken near the paper mill than at the reference sites. A higher prevalence of an ectoparasite, Cryptocotyle lingua, but a significantly lower mean abundance of three metazoans infecting the digestive tract was noted in fish near the mill than in the reference samples. These results, comprising abnormal fish size distribution, low body condition factor, external and internal lesions, enlarged liver, delayed gonadal development, and changes in parasitism, were stress-related, indicative of impaired health, and associated primarily with untreated discharges from the pulp and paper mill. This integrated and multidisciplinary study also provides further evidence on the use of fish parasites as a valid and an additional bioindicator in programs monitoring environmental contaminants.

The effects of Lepeophtheirus salmonis infections on the stress response and immunological status of Atlantic salmon (Salmo salar).

This study was conducted to determine the effects of a high level of infection of the parasitic copepod L. salmonis on the stress response and immunological status of Atlantic salmon. An initial low-level initial infection was carried out 14d prior to a second infection in which twice as many parasites were introduced. Plasma cortisol and prostaglandin E(2) (PGE(2)) levels were monitored concurrent to the expression of six immune-related genes over five sample times (9, 21, 26, 33 and 40days post initial infection, dpii). The mean lice counts on the infected fish increased significantly from the first infection (16.3+/-1.89 at 9dpii) to the second (142.8+/-12.8 at 26dpii). Plasma cortisol levels increased significantly at 26, 33 and 40dpii in infected fish compared to controls. Plasma PGE(2) levels were significantly higher in infected fish at 9, 33 and 40dpii, when compared to controls. At 9dpii, expression of interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNFalpha)-like cytokine, major histocompatibility class II (MH II), transforming growth factor-beta (TGFbeta)-like cytokine and cyclooxygenase-2 genes were increased in infected fish compared to controls. The expression of most of these genes returned to control levels at 21dpii when the highest expression of the MH class I gene was observed in infected fish (significantly higher than controls). Major histocompatibility class I gene expression remained higher in infected fish at 26 and 33dpii compared to controls and this was observed for the TNFalpha-like gene. By 33dpii, MH class II and TGFbeta-like genes had higher expression in infected fish compared to controls. Interleukin-1beta and TNFalpha-like gene were the only genes that showed significantly higher expression in infected fish compared to controls at 40dpii, while MH class I gene expression was significantly depressed in infected fish at this time. The expression of nearly all immune-related genes studied here increased following initial infection with L. salmonis, however, immunological stimulation did not reduce parasite numbers or protect against re-infection.

The presence of predators modifies the larval development of Fasciola hepatica in surviving Lymnaea truncatula.

Experimental infections of Lymnaea truncatula with Fasciola hepatica were performed to study the consequences of the presence of predators (sciomyzid larvae or zonitid snails) on the characteristics of larval F. hepatica development in surviving snails. Controls consisted of infected snails that were not subjected to predators. Compared to controls, the survival rate at day 30 post-exposure, the duration of cercarial shedding, and the number of cercariae shed by surviving snails were significantly lower when predators were present in snail breeding boxes, whatever the type of predator used. In contrast, the prevalences of Fasciola infections in snails, and the length of time between exposure and the onset of cercarial shedding showed no significant variation. The progressive development of a stress reaction in surviving snails against predators during the first 30 days of experimental exposure to F. hepatica would influence snail survival during the cercarial shedding period and, consequently, the number of cercariae shed by the snails.

Induction of stress by the swimbladder nematode Anguillicola crassus in European eels, Anguilla anguilla, after repeated experimental infection.

The purpose of this study was to determine under laboratory conditions over a period of 311 days if infection with the nematode Anguillicola crassus induces stress in European eels (Anguilla anguilla), and stimulates the endocrine stress axis as measured by serum cortisol levels. Eels were experimentally infected with 3rd-stage larvae (L3) in different doses to simulate natural conditions with varying infection pressures. Blood samples were drawn from the caudal vein every 2 weeks and serum cortisol concentrations were determined by radioimmunoassay (RIA). The results showed that the application of L3 resulted in a significant increase in the cortisol levels. The period of time at which elevated cortisol values were observed was consistent with the time of larval development and the appearance of adult A. crassus. Thus, there is a stress response to the larval and young adult stages, but no chronic response to older adults. Therefore, it is likely that infection of eels under natural conditions especially with a high number of larvae may be a considerable stressor, in combination with different environmental factors like water temperature, pH, oxygen concentration, pollution and interindividual relationships.

Effects of osmotic stress on metabolism, shape, and amino acid content of Leishmania.

An acute decrease in osmolality causes a rapid change in the shape of the parasitic protozoan Leishmania donovani as determined by light microscopy and by flow cytometry. Incubation of the cells is an isotonic buffer supplemented with glucose. 2-deoxyglucose (2-DG), alanine, or proline also causes a shape change, presumably due to the swelling caused by the water that accompanies these substrates as they are actively transported into the cells. Hypo-osmolality also causes a rapid release of alanine and several other amino acids via a swelling activated amino acid channel. A sudden increase in osmolality causes a change in shape, an inhibition in the rates of oxidation of alanine, proline, leucine, and glucose, and in the rates of uptake of 2-aminoisobutyrate (AIB) and 2-DG. The protein kinase inhibitors staurosporine and genistein inhibited the rates of oxidation of alanine, glucose, and proline in a culture-age dependent manner and also altered the rate of release of AIB in response to hypo-osmotic stress. The possible roles of protein kinases in the culture-age dependent changes in the uptake, release and metabolism of several amino acids and of glucose are discussed.

Recrudescence of Entopolypoides macaci Mayer, 1933 (Babesiidae) infection secondary to stress in long-tailed macaques (Macaca fascicularis).

Parasites were found in red blood cells of two long-tailed macaques (Macaca fascicularis) imported from Indonesia and housed in the Washington Regional Primate Research Center breeding colony for 7 years or longer. Both macaques developed parasitemias secondary to stress (type D retrovirus in one case and severe trauma in the other). Entopolypoides macaci (Babesiidae) was diagnosed on the basis of morphology from peripheral blood smears stained with Wright's stain. Antibodies against Babesia sp. were detected by immunofluorescence assay (IFA) from one infected macaque, which showed antibody cross-reactions (high titer) to B. bigemina, B. bovis, B. canis, and (low titers) to Plasmodium falciparum. Five feral long-tailed macaques that had been imported recently from the same country had no detectable antibodies. This is the first report of IFA as an aid to diagnose E. macaci in nonhuman primates.