First report on proliferative kidney disease (PKD) in marble trout (Salmo trutta marmoratus, Cuvier 1817)

Proliferative kidney disease is a hyperplastic response of the principal lymphoid tissue of salmonid fish infected by Tetracapsidoides bryosalmonae, a myxozoan parasite. This parasite affects many rainbow trout farms in Europe and North America. The disease has also been reported in other salmonids as well as in pike (Esox lucius) and grayling (Thymallus thymallus). In autumn 2000, an outbreak of PKD induced mortality in a group of marble trout (Salmo trutta marmoratus) juveniles reared in a farm in north-east Italy. The fish were intended to restock public waters. Diseased fish showed a lethargic behaviour, skin darkening, abdominal dilatation, gill anaemia and, after necroscopy, increase in volume and a pale colour of the kidney. All fishes subjected to histological examination showed a marked granulomatous interstitial nephritis, as well as foci of pancreatic and hepatic necrosis. The immunohistochemistry and PAS stain allowed visualisation of the extrasporogonic phase of the parasite Tetracapsuloides bryosalmonae in several tissues of the host. This is the first reported outbreak of PKD in marble trout, and should receive full attention since this species is potentially under risk of extinction

Red mark syndrome of trout (Oncorhynchus mykiss; Walbaum, 1792): Histopathological scoring and correlation with gross lesions

Red mark syndrome (RMS) is a skin disorder affecting rainbow trout (Oncorhynchus mykiss). The present work aimed to correlate the gross skin lesions affecting 46 fish sampled from farms surveyed for RMS with their microscopic features, identifying histological parameters that may be suggestive of disease progression. Skin lesions were grossly included in one of three categories (types I, II and III) according to the progressive degree of severity. Histological parameters and anti-proliferating cell nuclear antigen (PCNA) tissue immunoreactivity were semi-quantitatively assessed. In the dermis, PCNA-positive lymphocytes, fibroblasts and endothelial cells were indicative of active phlogosis. A significant increase in PCNA-immunoreactive lymphocytes, from gross type I to type III cases, was found only in the hypodermis. The histological parameters significantly associated with the gross lesion severity were progressive loss of the epithelium and scales, recruitment of inflammatory cells in the stratum compactum, loss of architecture of the stratum compactum, perivascular and perineural granulomatous inflammation and increase in lymphocyte infiltration of the muscular layer. In the type II and type III categories, inflammation in the hypodermis and muscle displayed a granulomatous pattern, reinforcing the hypothesis of an immunopathological mechanism. The morphological diagnosis of “deep chronic dermatitis associated to panniculitis and myositis, characterised by lympho-histiocytic and granulomatous reaction” is suggested

Red Mark Syndrome/Cold Water Strawberry Disease: emergence in Italy and histopathological investigations.

RMS/CWSD is a severe dermatitis affecting rainbow trout (O. mykiss), firstly described in Scotland in 2003. In the present paper we document for the first time some outbreaks occurring in Italy, by providing an accurate histological description of the lesions. The disease was signalled and surveyed in two farms located in north Italy, during spring period 2011. The water temperature 9\ub0C. The percentage of affected fish ranged between 10-15%, and their size was 450 g. Fish did not present other apparent concomitant signs of diseases, and mortality was absent. The necropsy findings allowed to classify based on the severity, the skin lesions as follows: PATTERN 1, flat and small lesions, characterised by slight desquamation and rare haemorrhages; PATTERN 2, larger than the previous, further sub-divided in 2a, round, slightly protruding, with serous/fibrinous exudates, various intensity of reddening, centrally ulcerated, and 2b, irregular shape, flat or poorly protruding, scarce presence of exudates, marked reddening, centrally ulcerated; PATTERN 3, large, markedly haemorrhagic, swollen, with presence of marginal exudates and deeply ulcerated. Skin tissue samples representative of each pattern were collected, as well as internal organs (heart, liver, kidney and spleen). The specimens were fixed with 4% buffered formalin or Bouin solution, then addressed to histology. Sections were stained with H.E., Toluidine blue, Masson\u2019s Trichrome, Giemsa. Moreover immunohistochemistry (IHC) was performed using antibodies specific for: pan-cytokeratin, AE1-AE2 cytokeratins, cadherin, myeloperoxidase, lysozyme, CD3, CD68. The histological description of patterns is the following. PATTERN 1, slight loss of epidermis, with moderate necrosis, severe monocyte-lymphocyte infiltration in the dermal layer and dermal-epidermal junction, severe lymphocyte infiltration in the subcutaneous layer, involving also the muscle. PATTERN 2a, loss of epidermis in the centre of the lesion, presence of lymphocyte infiltrate and necrosis, in the dermal-epidermal junction presence of necrosis with detachment of the layers. In the dermis spongiosum presence of congestion, haemorrhages, massive infiltration of macrophages and lymphocytes, multinucleated cells, high mitotic index and necro-fibrinuous exudate. In the subcutaneous tissue presence of a monomorphic histiocyte-like infiltrate, high mitotic index. The infiltrate involves the adipose tissue displaying granulomatous aspects (panniculitis-like), and involves also the muscle. Often the infiltrate is neurotrophic. PATTERN 2b, in the epidermal layer the pattern is similar to the one observed in PATTERN 2a. In the stratum spongiosum, presence of lymphocyte infiltrate in proximity to scales and within the scale pockets, dermal necrosis, congestion and haemorrhages, presence of histiocyte-like cells. In the stratum compactum presence of a mononuclear infiltrate. In the sub-cutaneous layer evidence of a strong lymphocyte-histiocyte infiltrate, being the latter more abundant. The architecture of the skin and muscular layers is deeply modified. PATTERN 3, the lesions are similar to the previous, but are more severe in terms of ulcerative-necrotic processes affecting skin. The antibody markers did not reveal any positivity, except for cytokeratins and E cadherin at epidermis. The histopathological patterns are dominated by a severe cellular infiltrate, initially composed by lymphocytes and subsequently partially replaced by histiocytes, located in the subcutis. Histiocytosis seems to be the prevalent feature. The dynamic of the lesion proceeds from subcutus, towards the derma to the epidermis (that can be considered an epiphenomenon). It is however interesting the flogistic lesion localized in the dermal-epidermal junction, assimilable to lichenoid-dermatitis features already described in mammals

Red mark syndrome in trota iridea (O. Mykiss) allevata in italia: descrizione anatomoistopatologica.

La Red Mark Syndrome (RMS) è una dermatite che colpisce la trota iridea (O. mykiss), descritta per la prima volta in Scozia nel 2003; in Italia, da alcuni anni, la malattia è sporadicamente segnalata e colpisce soggetti adulti a temperature inferiori a 15°C. L’eziologia della malattia non è ancora stata accertata, anche se, di recente, un organismo rickettsia-like (RLO) è associato alle lesioni eritematose. Finalità di questo contributo è documentare alcuni episodi di malattia intercorsi, da maggio a dicembre 2011, in 4 allevamenti del nord Italia con morbosità tra il 10 e il 15%. Macroscopicamente le lesioni cutanee sono state classificate in: morfotipo I, lesioni poco estese e non rilevate, caratterizzate da scarsi fenomeni emorragici e desquamativi; morfotipo II, lesioni più estese, leggermente rilevate, con vari livelli di arrossamento e centralmente ulcerate; morfotipo III, lesioni molto estese, marcatamente emorragiche e rilevate, profondamente ulcerate. Campioni di cute di ciascun morfotipo e organi interni sono stati fissati in formalina tamponata al 4%/in Bouin per le indagini istologiche e in glutaraldeide al 2% per la TEM. Le lesioni infiammatorie, in sintesi, sono caratterizzate dal reclutamento di un forte infiltrato cellulare, costituito prevalentemente da linfociti, plasmacellule e macrofagi. La dinamica della lesione lascia ipotizzare un’origine nell’ipoderma e successiva progressione verso il derma e l’epidermide, con coinvolgimento del tessuto muscolare. Oltre alla descrizione delle lesioni, alcuni aspetti relativi alla eziopatogenesi della malattia saranno discussi

Red Mark Syndrome in trota iridea (O. mykiss) allevata in Italia: descrizione anatomoistopatologica

La Red Mark Syndrome (RMS) \ue8 una dermatite che colpisce la trota iridea (O. mykiss), descritta per la prima volta in Scozia nel 2003; in Italia, da alcuni anni, la malattia \ue8 sporadicamente segnalata e colpisce soggetti adulti a temperature inferiori a 15\ub0C. L\u2019eziologia della malattia non \ue8 ancora stata accertata, anche se, di recente, un organismo rickettsia-like (RLO) \ue8 associato alle lesioni eritematose. Finalit\ue0 di questo contributo \ue8 documentare alcuni episodi di malattia intercorsi, da maggio a dicembre 2011, in 4 allevamenti del nord Italia con morbosit\ue0 tra il 10 e il 15%. Macroscopicamente le lesioni cutanee sono state classificate in: morfotipo I, lesioni poco estese e non rilevate, caratterizzate da scarsi fenomeni emorragici e desquamativi; morfotipo II, lesioni pi\uf9 estese, leggermente rilevate, con vari livelli di arrossamento e centralmente ulcerate; morfotipo III, lesioni molto estese, marcatamente emorragiche e rilevate, profondamente ulcerate. Campioni di cute di ciascun morfotipo e organi interni sono stati fissati in formalina tamponata al 4%/in Bouin per le indagini istologiche e in glutaraldeide al 2% per la TEM. Le lesioni infiammatorie, in sintesi, sono caratterizzate dal reclutamento di un forte infiltrato cellulare, costituito prevalentemente da linfociti, plasmacellule e macrofagi. La dinamica della lesione lascia ipotizzare un\u2019origine nell\u2019ipoderma e successiva progressione verso il derma e l\u2019epidermide, con coinvolgimento del tessuto muscolare. Oltre alla descrizione delle lesioni, alcuni aspetti relativi alla eziopatogenesi della malattia saranno discussi