Purified metallo-protease from the pathogenic haemoflagellate Cryptobia salmositica and its in vitro proteolytic activities

Self Cite

At 10°C, rainbow trout Oncorhynchus mykiss (n = 13 per group) infected with Cryptobia salmositica Katz, 1951 became anorexic at 3 wk post-infection (w.p.i.), with feed-intake decreasing significantly from 1.33 to 0.94% body weight (b.w.). Anorexia was most severe at 4 w.p.i. (0.80% b.w.), coinciding with peak parasitemia (9.2 × 10 6 parasites ml blood -1) and anemia. At 8 w.p.i., fish had recovered their appetite although they still had contained detectable parasites (6.8 × 10 5 parasites ml ) and low PCV (10.8%). Fish at 5°C had lower gastric evacuation (GE) rates (GE 48h ) than 10°C fish, however there were no differences between infected and naïve fish at both temperatures. Before anorexia, there was no significant correlation between mean share of meal (MSM, a measure of how food was partitioned within a group) and coefficient of variation in feeding but this became significant during anorexia (p = 0.02 and p = 0.0002 at 10 and 5°C respectively). Significant correlations were detected between b.w. and MSM before onset of anorexia at 10°C (p = 0.005) and 5°C (p = 0.02); this was maintained at 10°C (p = 0.001) but not at 5°C (p = 0.98). Fish on an anorexic diet (0.93% b.w.) responded well at 10°C to a live C. salmositica vaccine; this could partly be due to constant antigenic stimulation by the live vaccine.

Section: Discussionsupporting

confidence: 81%

Effect of Cryptobia salmositica-induced anorexia on feeding behavior and immune response in juvenile rainbow trout Oncorhynchus mykiss

Chin¹,

Guo²,

Bernier³

et al. 2004

Self Cite

“…This is the haemolysin that was identified earlier as 1 of the causes of anaemia in C. salmositica-infected fish (Thomas & Woo 1988, 1989. The metalloprotease is also collagenolytic as it degrades various collagens (types I, IV and V) and laminin (Zuo & Woo 1997b). Since its in vitro secretion by the C. salmositica is significantly increased in the presence of either type I or type IV collagen (Zuo & Woo 1998b), this histolytic enzyme is a major virulent factor.…”

Section: Discussionmentioning

confidence: 99%

“…The cysteine protease is a metabolic enzyme while the metalloprotease is an important contributing factor to the anaemia in salmonid cryptobiosis (Zuo & Woo 1998a). The purified metalloprotease lyses fish erythrocytes under in vitro conditions (Zuo & Woo 2000) by digesting the erythrocyte membrane proteins (Zuo & Woo 1997b). This is the haemolysin that was identified earlier as 1 of the causes of anaemia in C. salmositica-infected fish (Thomas & Woo 1988, 1989.…”

Section: Discussionmentioning

confidence: 99%

Relations between histopathology and parasitaemias in Oncorhynchus mykiss infected with Cryptobia salmositica, a pathogenic haemoflagellate

Bahmanrokh

Woo

2001

Self Cite

One group (n = 50) of juvenile rainbow trout Oncorhynchus mykiss was inoculated intraperitoneally with 2000 (low dose [LD]) and another group (n = 50) with 20 000 (high dose [HD]) Cryptobia salmositica fish -1 . The histopathology was a generalised inflammatory reaction, and lesions were in connective tissues and in the reticulo-endothelial system. In the LD group, the first lesions were observed in the liver, gills and spleen at 2 wk post infection (pi) while in the HD group they were in the liver and gills at 1 wk pi. Endovasculitis and mononuclear cell infiltration were observed at 3 wk pi in the HD group. These were followed by tissue necrosis and extravascular infiltration of parasites at 4 wk pi. The severity of lesions was directly related to parasitaemias in the blood and extravascular location of parasites. In the HD group, the most extensive tissue necrosis was at 4 wk pi and in the LD group it was 6 to 7 wk pi. Necrosis in the vital organs (liver, kidney and depletion of the haematopoeitic tissues) and anaemia were probably in part responsible for mortality of fish during acute disease. Regeneration and replacement of necrotic tissues were seen at 7 to 9 wk pi in the HD group, and it was most noticeable in haematopoietic and reticular tissues. These occurred during the recovery phase of the disease and were associated with significant reduction in blood parasitaemia. KEY WORDS: Cryptobia salmositica · Oncorhynchus mykiss · Histopathology · Parasitaemias Resale or republication not permitted without written consent of the publisherDis Aquat Org 46: [41][42][43][44][45] 2001 MATERIALS AND METHODSTwo groups (n = 50 in each group) of hatchery-raised juvenile rainbow trout (about 6 to 8 cm in length) were maintained in 2 fibre glass tanks at about 8°C for 2 wk before they were experimentally infected with Cryptobia salmositica. The inocula were prepared with blood from an infected rainbow trout and diluted with appropriate volumes of PBS (pH 7.4). The low dose (LD) group was inoculated intraperitoneally (ip) with 2000 parasites fish -1 and the high dose (HD) group with 20 000 parasites fish -1 . At weekly intervals, 4 fish from each group were anesthetised with MS-222 (100 ppm), bled and necropsied. In the first week after infection the parasitaemias in the blood were detected using the haematocrit centrifuge technique and wet mount method (24 microscopic fields examined, 10× objective). In subsequent weeks, the haemocytometer was used to estimate parasitaemias (Woo 1979). For histopathology, samples of visceral organs, skin, eye, brain and gills were fixed in 10% formalin, embedded in paraffin, sectioned into 4 µm thick pieces, and stained with haematoxylin and eosin. Smears of ascites fluid or blood were air dried, fixed in 100% Ethanol and stained with Giemsa's stain. A third group of uninfected fish (controls) was also sampled. RESULTS LD groupThe haematocrit centrifuge technique detected parasites in the blood of all fish at 1 wk post infection (pi).The parasitaemia increased rapidly, p...

“…The parasite secretes a 200 kDa metalloprotease, and this is an important disease-causing factor in salmonid cryptobiosis (Zuo & Woo 1997). An attenuated strain of Cryptobia salmositica has been developed (Woo & Li 1990), and it does not produce/secrete the metalloprotease (Zuo & Woo 1997).…”

Section: Introductionmentioning

confidence: 99%

“…An attenuated strain of Cryptobia salmositica has been developed (Woo & Li 1990), and it does not produce/secrete the metalloprotease (Zuo & Woo 1997). The strain has remained avirulent for the last 16 yr and is used routinely as an experimental vaccine because it does not cause disease and circulates in the blood for at least 6 mo (e.g.…”

Section: Introductionmentioning

confidence: 99%

Use of a live vaccine to modulate Cryptobia salmositica infections in Salmo salar

Davy¹,

Crispo²,

Woo³

2007

Self Cite

The vaccine strain of Cryptobia salmositica multiplies in Atlantic salmon Salmo salar. and it can modulate the severity of the disease in Cryptobia-infected individuals. Fish injected with the vaccine 3 d post-infection with C. salmositica had lower peak parasitaemias and higher antibody titres than infected fish given the vaccine 7 d post-infection or those infected fish that were not given the vaccine.