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First record of an outbreak of saprolegniosis by Saprolegnia parasitica in Pseudochondrostoma duriense (Coelho, 1985) (Cyprinidae)

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Abstract

An outbreak of saprolegniosis by Saprolegnia parasitica in the cyprinid fish Pseudochondrostoma duriense is described here for the first time. P. duriense is endemic to the Iberian Peninsula. Hundreds of sick and dead fish appeared in the River Bernesga (Spain). Skin and subcutaneous skeletal musculature were infected. Fish showed multi-focal dermatitis with loss of the epidermis, degeneration and necrosis of the skeletal muscle fibres, ulcerative keratoconjunctivitis and anterior uveitis.
Bull. Eur. Ass. Fish Pathol., 36(2) 2016, 91
* Corresponding author’s email: jmallg@unileon.es
NOTE
ȱȱȱȱȱȱȱ
by Saprolegnia parasitica in Pseudochondrostoma
duriense (Coelho, 1985) (Cyprinidae)
ǯȱǯȱȬȘǰȱǯȱǯȱȬǰȱǯȱ£¤£Ȭ
Palacios, M. J. García-Iglesias and L. I. Pérez-Ordoyo
Animal Health Department. Veterinary Faculty. University of
àǯȱȱȱ£ǰȱȦǯȱŘŚŖŝŗȱàǯȱ
Abstract
ȱȱȱȱ¢ȱSaprolegnia parasiticaȱȱȱ¢ȱęȱPseudochondrostoma duriense
ȱȱȱȱȱęȱǯȱP. durienseȱȱȱȱȱȱǯȱȱȱȱ
ȱȱęȱȱȱȱȱȱǻǼǯȱȱȱȱȱȱ
ȱǯȱȱȱȬȱȱȱȱȱȱǰȱȱȱ
ȱȱȱȱȱęǰȱȱȱȱȱǯ
Saprolegnia parasiticaȱȱȱȱȱSap-
rolegnia (Kingdom Chromista, Class Oomy-
ǼȱȱȱȬȱęǰȱȱǰȱ
ȱȱȱǯȱȱȱȱ
by Neish and Hughes (1980), Bruno et al. (2011)
ȱ£ȱȱǯȱǻŘŖŗŚǼȱȱȱȱȱ
ęȱȱȱȱȱȱȱǯȱ
ȱȱ¢ȱȱȱęȱȱ
ȱȱȱȱȱPseudochon-
drostoma duriense (Coelho, 1985), the northern
straight-mouth nase whose Spanish name is
“boga del Duero”.
ȱȱȱ¢ȱȱŘŖŗŗȱȱȱȱ
ȱȱęȱȱȱȱȱǰȱ
ȱ¢ȱȱȱȱǰȱȱȱĚȱ
ȱȱ¢ȱȱàȱȱȬȱǯȱ
ȱęȱȱȱȱȱĴ¢ȱȱ
spread over their head, trunk, caudal peduncle
ȱęȱȱȱȱȱ¢ȱ¢ȱ
ȱȱę¢ȱ¢ȱSaprolegnia spp. Some
ęȱȱȱȱȱȱȱȱȱȱ¢ȱ
£ǰȱȱȱȱȱ¢ȱěǰȱȱ
ȱȱȱȱȱęȱǻȱ
ŗǰȱǼǯȱȱȱěȱęȱȱȱȱ-
ȱĚȱĚ¡ȱȱ¢ȱȱ£ȱȱ
Ĵȱǯ
ȱěȱęȱǻ¡ȱǰȱȱǼȱ
were caught. Their average length was 17.9 ± 3.4
ȱȱȱşŗȱƹȱŚśǯŘȱǯȱȱȱȱȱ
lesions were observed under the microscope
ȱȱȱȱĴȱǯȱ
Others were cultured on glucose peptone agar
(GPA) with chloramphenicol (0.05 mg mL-1) at
ŘŖȱķȱȱȱȬȱǯȱSaproleg-
92, Bull. Eur. Ass. Fish Pathol., 36(2) 2016
nia isolates were subcultured onto GPA with
hemp seeds (Cannabis sativaǼȱȱ¢ȱ-
ȱȱ£ȱȱȱȱȱȱ
ȱęȱȱȱȱǰȱȱŝȱ
ķȱȱȱŘŖȱķǰȱȱȱȱȱȱ
zoospores and sexual reproduction (oogonia)
(Willoughby, 1978); and to observe the long
hairs and indirect germination on the second-
¢ȱ¢ǰȱ¢ȱȱǰȱȱȱĴȱȱ
ȱȱǻ¢ǰȱŗşŞśǼǯȱęȱȱ
Saprolegnia parasiticaȱȱȱȱȱȱ-
phological characteristics: long hairs on the
secondary cysts, indirect (retracted) germination
ȱȱȱŝȱķȱǻȱǼȱǻ-
loughby, 1985; Diéguez-Uribeondo et al., 2007).
ȱȱȱ¢ǰȱȱȱ
spleen were grown on tryptone soy agar (TSA),
ȱȱȱ¢ȱȱȱȱ
ȱȱȱŗŚȱęǯȱȱȱȱȱ
ęȱ¢ȱȱȱ·¡ȱțȱ
2 System using the GN reagent card and then
ȱęȱȱȱȱ¡ȱ
ȱȱȱȱ¢ȱ¢ȱȱŗŜȱȱ
GyrB genes and using BLAST on GenBank.
A histopathological study was also carried out
on the skin and eyes with lesions, together with
ȱ¢ǰȱǰȱȱȱȱȱȱ
ęǯȱȱȱȱę¡ȱȱŗŖƖȱěȱ
ȱȱȱȱĜǰȱȱȱ
tissue sections were stained with haematoxy-
ȱȱǰȱȱȬěȱǻǼȱȱ
Gomori methenamine silver (GMS).
ȱȱȱ cutaneous lesions
and signs described above, necropsy showed
no lesions in internal organs. Ovaries and
ȱȱ¢ȱȱȱȱęȱȱ
ȱȱȱǯȱȱ¢ȱȱ
ȱȱȱȱȱȱȱ-
ȱĴȱȱȱ¢ȱȱ£-
ȱȱSaprolegnia spp., and Saprolegnia
parasiticaȱǻ¡ȱȱŝȱķȱȱŘŖȱķǰȱȱȱ
hairs and indirect germination on its second-
¢ȱ£ȱ¢Ǽȱȱȱȱȱ
ȱȱȱȱȱȱǯȱȱ
ȱ¢ǰȱȱȱȱȱȱȱ
ȱȱȱǰȱ¢ȱȱ
ȱȱȱȱęȱǻȱȱ
colony morphology). The seven selected iso-
ǰȱȱȱȱȱęǰȱȱęȱȱ
Shewanella putrefaciensȱǻŗȱęǼǰȱAeromonas media
ǻŗȱęǼǰȱAeromonas sobriaȱǻŘȱęǼȱȱAeromonas
bestiariumȱǻŘȱęǼȱȱȱǰȱȱ
Aeromonas sobriaȱȱȱȱ¢ȱǻŗȱęǼǯȱ
ȱȱęȱS. parasiticaȱȱȱȱȱ
Figure 1. ȱȱȱĴ¢ȱȱȱ¢ȱSaprolegnia parasitica on skin (head, trunk, caudal
Ǽǰȱ¢ȱȱęȱȱPseudochondrostoma duriense (A, B).
AB
Bull. Eur. Ass. Fish Pathol., 36(2) 2016, 93
internal organs (kidney, spleen or liver) in bac-
teriological cultures on TSA.
Histopathological examination showed non-
ȱȬȱȱȱȱȱȱ
epidermis (Figure 2A). There was also marked
ęȱ£ȱǰȱ¢ȱ£ǰȱ
¢ȱȱȱȱȱȱȱ
ȱęȱȱȱȱȱǻȱŘǼǯȱ
Additionally, there was ulcerative keratocon-
ȱȱȱǰȱȱȱȱȱ
anterior and posterior corneal epithelium and
ȱĚ¢ȱęȱȱȱǰȱ
conjunctiva, iris, ciliary body and the anterior
ȱȱȱ¢ȱǻȱŘǼǯȱȱȱȱȱ
skin, muscle tissue and eyeball were associated
ȱȱȱȱ¢ȱ¢ȱȱ
with PAS and GMS staining (Figure 2A, B, C).
No histopathological lesions or hyphae were
seen in internal organs (kidney, liver, spleen
and intestines).
ȱȱȱȱȱȱȱȱȱ
¡ȱȱȱSaprolegnia spp. in
ȱȱȱęǰȱȱȱȱǰȱȱ
ȱȱȱȱȱȱȱ
ȱȱȱȱȱ¢ȱȱȱ
ȱȱȱȱȱ¢ęȱ
degenerative changes. They have also noted
ȱȱ¢ȱȱěȱȱȱǰȱ
with any spreading to other internal tissues
being rarer (Bly et al., 1992; Copland and Wil-
loughby, 1982; Fregeneda-Grandes et al., 2001;
Hatai and Hoshiai, 1992; Neish, 1977; Nolard-
Tintigner, 1973; Srivastava et al., 1994; Xu and
Rogers, 1991).
The genus Pseudochondrostoma (Cyprinidae)
contains three species, P. duriense, P. polylepis
and P. willkommii (Robalo et al., 2007), which are
ȱȱȱȱȱȱȱǯȱ
P. durienseȱȱȱęȱȱȱȱȱ
ęǰȱȱȱȱȬȱȱȱȱ
ȱǻȱȱǼȱȱȱȱȱ
the rivers Duero and Miño (Douro and Minho)
ȱȱȱȱȱȱȱȱǰȱ
while the species P. polylepis and P. willkommii
ȱ¢ȱȱȱȱȱȱȱȱ
the Iberian Peninsula, respectively (FishBase,
ŘŖŗśDzȱǰȱŘŖŗśǼǯȱȱȱȱ-
ȱěȱPseudochondrostoma duriense.
ȱȱȱęȱȱȱȱȱȱ
ȱȱȱȱǰȱ¢ȱ¢ǰȱ
ȱěǯȱ¢ȱȱȱ¢ȱ
ȱȱȱȱ¢ȱȱConfederación
¤ęȱȱ yielded values within
ȱȱǻǯȱǯǼǯȱȱęȱȱȱ
ȱȱȱȱȱǰȱȱȱ
having spawned and others being on the point
ȱǯȱȱȱȱȱ-
ȱȱȱȱȱȱȱȱȱȱ
ȱȱǰȱȱȱ
¢ȱȱȱȱȱȱȱȱȱȱ
ȱȱȱȱȱȱȱȱȱ
Ěǯȱȱȱěȱȱȱȱ-
taneous skeletal musculature, but not internal
ǯȱȱȱS. parasiticaȱȱȱȱ
ȱȱęȱȱȱȱȱ¢ȱȱȱ
hyphae or histopathological lesions, so that it
may have been due to S. parasitica being in the
ȱȱȱȱȱȱȱ
ȱȱ¢ǯȱȱȱȱȱ
internal organs belonged to various species
and were not associated with any lesions in the
ȱȱȱȱęǰȱȱȱ¢ȱȱ
ȱȱȱȱȱ¢ȱȱ
ȱȱS. parasitica.
ȱȱȱȱȱȱȱȱ
saprolegniosis in the wild brown trout Salmo
94, Bull. Eur. Ass. Fish Pathol., 36(2) 2016
Ĵ L. caused by Saprolegnia parasiticaȱǻ-
¢ȱęȱȱSaprolegnia sp. asexual or
Saprolegnia diclina Type 1) in the upper stretch
ȱȱȱȱȱȱȱȱȱȱ
ȱȱȱȱȱǻȬȱȱ
¤£ȬÇ£ǰȱŗşŞŝDzȱȬȱȱȱ
al., 2000, 2009), but never in P. duriense. There
ȱȱȱȱǰȱȱȱ
ȱȱSaprolegnia was not isolated or iden-
ęǰȱȱȱȱȱChondrostoma pol-
ylepisȱȱȱȱȱȱ£ȱȱȱ
ȱȱȱȱȱȱǻ£¤£ȱ
de Canales et al., 2001). Currently C. polylepis
ȱęȱȱPseudochondrostoma polylepis
ǻȱȱǯǰȱŘŖŖŝǼȱȱȱȱȱ
ęȱȱ¢ȱȱP. willkommii and not
P. polylepis ȱȱ C. polylepis in the river
Chanza (SIBIC, 2015). It would seem that the
ȱȱȱȱęȱȱȱȱȱ
ȱȱ¢ȱSaprolegnia parasiticaȱ-
ȱȱȱPseudochondrostoma duriense
(“boga del Duero”).
Acknowledgments
This work was supported through research
ȱŘŖŗŖȬŗŞśŜŘȱȱȱȱMinis-
terio de Ciencia e Innovación. C.G.P. received a
ȱȱȱConsejería de Educaciónȱȱ
the Regional Government Junta de Castilla y
LeónǰȱȬęȱ¢ȱȱȱȱǯȱ
Figure 2. Saprolegniosis lesions on skin,
ȱȱȱ¢ȱȱPseudochondrostoma
duriense (GMS stain): (A) Skin: Saprolegnia parasitica
hyphae in the dermis (ÎǼȱ ȱ ¢ȱ
ęȱȱȱȱȱȱȱȱǻƇ)
ȱ¢ȱǻȣǼǯȱǻǼȱȱȱDZȱ
¢¢ȱ£ȱ¢ȱęȱ£ȱȱȱ
£ȱȱȱ¢ȱǻȣǼȱȱȱǻƅǼȱȱ
ȱȱęDzȱ¢ȱȱS. parasitica associated
with muscular lesion (Î). (C) Eye: Ulcerative keratitis
ȱȱȱ£ȱ¢ȱȱȱȱ
the anterior and posterior corneal epithelium (Ƈ)
ȱĚ¢ȱȱęȱȱȱȱǻȣǼǰȱ
ȱȱȱȱȱȱ¢ȱǻƅǼDzȱ¢ȱȱS.
parasitica on the cornea (Î).
A B
C
Bull. Eur. Ass. Fish Pathol., 36(2) 2016, 95
We wish to express our gratitude to the Servicio
Territorial de Medio Ambiente and the Laboratorio
Regional de Sanidad Animal de Leónȱȱȱ-
al Government Junta de Castilla and Leónȱȱȱ
ȱȱȱęȱȱȱȱȱȱ
ȱȱȱŘȱ¢ǯ
References
Ȭȱȱ ȱ ¤£ȬÇ£ȱ ȱ
(1987). Saprolegniosis en la trucha común
(ȱĴ L.) de los ríos de León (España).
Medicina Veterinaria 4, 181-184.
Bly JE, Lawson LA, Dale DJ, Szalai AJ,
Durborow RM and Clem LW (1992). Winter
ȱȱȱęǯȱDiseases
of Aquatic Organisms 13, 155-164.
Bruno DW, Van West P and Beakes GW (2011).
Saprolegnia and other Oomycetes. In “Fish
diseases and disorders, Volume 3: Viral,
bacterial and fungal infections” (P.T.K.
Woo and D.W. Bruno, Eds.), pp. 669-720.
ǰȱǰȱǯȱȬŗřDZȱşŝŞȱŗȱ
84593 554 2.
Copland JW and Willoughby LG (1982).
ȱ¢ȱȱSaprolegniaȱȱȱ
Anguilla anguilla L. elvers. Journal of Fish
Diseases 5, 421-428.
Diéguez-Uribeondo J, Fregeneda-Grandes
JM, Cerenius L, Pérez-Iniesta E, Aller-
Gancedo JM, Tellería MT, Söderhäll K
ȱÇȱȱǻŘŖŖŝǼǯȱȬȱȱ
the enigmatic species complex Saprolegnia
diclina-Saprolegnia parasitica based on
morphological, physiological and molecular
data. Fungal Genetics and Biology 44, 585-601.
FishBase (2015). Available in ǯęǯ
org. [1 June 2015].
ȬȱǰȱȬ£¤£ȱȱ
and Aller-Gancedo JM (2009). Prevalence
ȱȱȱȱSaprolegnia
parasiticaȱȱȱȱȱȱȱ
ȱĴ. Diseases of Aquatic Organisms
83, 17-22.
Ȭȱǰȱ¤£ȬÇ£ȱȱȱ
Aller-Gancedo JM (2000). Ultrastructural
¢ȱȱSaprolegnia secondary zoospore
¢ȱȱ ȱ ȱȱ
brown trout, ȱ Ĵ L., and river
water indicates two distinct morphotypes
amongst long-spined isolates. Journal of Fish
Diseases 23, 147-160.
Ȭȱ ǰȱ ¤£Ȭ
Díez M and Aller Gancedo JM (2001).
Experimental pathogenicity in rainbow
trout, Oncorhynchus mykiss ǻǼǰȱȱ
ȱȱ¢ȱȱȬȱ
Saprolegniaȱȱȱȱȱ
brown trout, ȱĴ L., and river water.
Journal of Fish Diseases 24, 351-359.
£¤£ȱ ȱ ȱ ǰȱ Ȭ£ȱ ǰȱ
£¤£ȱ ȱ ȱ ȱ ȱ ȱ
ȱ ǻŘŖŖŗǼǯȱ ȱ ȱ ȱ ȱ
populations. Ciencias Marinas 27, 125-137.
Gozlan RE, Marshall WL, Lilje O, Jessop CN,
Gleason FH and Andreou D (2014). Current
ȱȱȱȬȱ
ȱ ȱ ęDZȱ ȱ ȱ ǵǯȱ
Frontiers in Microbiology/Aquatic Microbiology
5, article 62, 1-16.
Hatai K and Hoshiai G (1992). Mass mortality
in cultured coho salmon (Oncorhynchus
kisutch) due to Saprolegnia parasistica Coker.
Journal of Wildlife Diseases 28, 532-536.
Neish GA (1977). Observations on saprolegniasis
ȱȱ¢ȱǰȱOncorhynchus nerka
(Walbaum). Journal of Fish Biology 10, 513-
522.
Neish GA and Hughes GC (1980). “Diseases of
ęǯȱȱŜDZȱȱȱȱęȄ.
TFH Publications Inc, Neptune, NJ. ISBN
0 87666 504 0.
Nolard-Tintigner N (1973). Etude experimentale
sur l’epidemiologie et la pathogenie de la
saprolegniose chez Lebistes reticulatus Peters
et Xiphophorus helleri Heckel. Acta Zoologica
et Pathologica Antverpiensia 57, 1-127.
Robalo JI, Carvalho-Almada V, Levy A and
Doadrio I (2007). Re-examination and
¢¢ȱȱȱȱChondrostoma based
on mitochondrial and nuclear data and
96, Bull. Eur. Ass. Fish Pathol., 36(2) 2016
ȱęȱȱśȱȱǯȱMolecular
Phylogenetics and Evolution 42, 362-372.
SIBIC (2015). Carta piscícola española. Available
in www.cartapiscicola.es [5 December
2015].
Srivastava GC, Sinha SK and Prabhuji SK (1994).
ȱȱȱȱȱChela
laubucaȱǯȱȱȱȱȱȱ
mycoses. Current Science 66, 237-239.
¢ȱ ȱ ǻŗşŝŞǼǯȱ ȱ ȱ
ȱęȱȱDZȱȱȱ
analysis. Journal of Fish Diseases 1, 51-67.
Willoughby LG (1985). Rapid preliminary
ȱȱSaprolegniaȱȱęǯȱJournal of
Fish Diseases 8, 473-476.
Xu D and Rogers WA (1991). Electron
¢ȱȱȱ¢ȱSaprolegnia sp.
ȱȱęǯȱJournal of Aquatic Animal
Health 3, 63-69.
... Saprolegniasis has been associated with huge mortalities in several fish species including coho salmon Oncorhynchus kisutch (Hatai and Hoshiai, 1992), Northern straight-mouth nase Pseudochondrostoma duriense (Aller-Gancedo et al., 2016) and salmonids Salmo trutta and Thymallus thymallus (Rocchi et al., 2017). In the present study, we report mortalities in striped catfish due to S. parasitica infection. ...
... In the present study, we report mortalities in striped catfish due to S. parasitica infection. The clinical signs and mortalities observed in the present study are in conformity to previous reports of saprolegniasis in different fish species (Hatai and Hoshiai, 1992;Abd El Aziz et al., 2004;see van West, 2006;Aller-Gancedo et al., 2016;Tandel et al., 2021). The histopathological lesions in the present study comprised of severe destruction of the epidermis and degenerative changes in dermis and muscle fibers, and were similar to published reports of Saprolegnia-infected fishes (Hatai and Hoshiai, 1994;Salih and Mustafa, 2017;Shin et al., 2017). ...
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Mortalities were observed in several Pangasianodon hypophthalmus farms (n = 52) of Uttar Pradesh, North India during December 2020–January 2021. The affected fish were lethargic, swimming near the water surface and had white or grayish cotton-like patches over the body surface. Wet mount examination of the patches revealed presence of non-septate hyphae suggestive of oomycete infection. However, no parasites were observed in skin and gill scrapings. Histopathological examination of the affected skin tissue indicated severe destruction of the epidermis, degenerative changes and penetration of the oomycete hyphae in the dermis and underlying musculature. From the affected skin lesions, oomycete could be isolated which was identified as Saprolegnia parasitica based on morphological characteristics, and amplification and sequencing of the internal transcribed spacer region. Importantly, from the diseased P. hypophthalmus, no bacteria and viruses could be isolated from kidney, and pooled kidney and spleen tissues, respectively. Further, following experimental infection with S. parasitica zoospores by immersion method, 100% mortality was observed in P. hypophthalmus, indicating that the isolate was virulent. From the experimentally-infected striped catfish, S. parasitica could be reisolated and the histopathological lesions were similar to those observed in naturally infected fish, thereby fulfilling Koch’s postulates. Based on the gross and histopathological lesions, isolation of oomycete, molecular identification and bioassay, it was concluded that S. parasitica was responsible for mortalities in P. hypophthalmus farms. This forms the first report of mortalities of striped catfish due to oomycete S. parasitica infection and the findings will pave way for developing control measures for reducing losses in striped catfish farms due to saprolegniasis.
... Investigations regarding the prevalence of specific pathogens are limited and often do not focus on the impact these agents might have for the host. Also, past studies have focused on parasitological and fungal surveys [11,12], neglecting the influence that other pathogenic agents-i.e., bacteria and virus-might have in leuciscids. ...
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Pure cultures of fungus were isolated from commercially raised channel catfish Ictalurus punctatus exhibiting overt signs of a winter syndrome locally termed 'winter kill'. The fungal isolates were identified as members of the genus Saprolegnia. Histopathological examination of fungal associated skin lesions from diseased fish exhibited a complete lack of bacteria or of leukocytic infiltration around the site(s) of hyphal penetration. In order to determine if the fungus was the origin of disease or an opportunistic secondary pathogen, controlled laboratory studies were conducted which conclusively proved that if channel catfish were immunosuppressed by a rapid decrease in environmental water temperature from 22 to 10-degrees-C, the Saprolegnia sp. isolates rapidly infected catfish to cause 92 % infection (skin lesions) and 67 % mortality within 21 d post-challenge. Examination of laboratory-infected fish revealed fungal associated skin lesions with histopathology identical to that obtained from fish in the field, i.e. there was a complete lack of bacterial or leukocytic infiltration around the lesion site. These results strongly suggest that 'winter kill' syndrome in catfish is an immunodeficiency disease of fungal rather than bacterial etiology and is probably better termed 'winter saprolegniosis'.
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Saprolegnia sp. isolated from channel catfish Ictalurus punctatus grew slower than S. parasitica on cornmeal agar (CMA). Oogonia in Saprolegnia sp. appeared frequently, whereas oogonia were rarely seen in S. parasitica on CMA. In experimental exposures of injured channel catfish to fungal spores, infections were apparent after 3–4 d, but were most common after 7–9 d. Multiple lesions were usually seen in naturally infected fish, whereas a single lesion appeared at the injured site of experimentally infected fish. No obvious differences were found between lesions caused by S. parasitica and those caused by Saprolegnia sp. Most of the epidermal cells in fungusinfected lesions were necrotic. In some lesions, the epidermis was completely sloughed and the dermis was exposed. Both Saprolegnia parasitica and Saprolegnia sp. penetrated the dermis, causing damage to fibroblasts and collagen lamellae.
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The prevalence of serum antibodies against Saprolegnia parasitica in wild and farmed brown trout Salmo trutta from the province of Le6n (NW Spain) was studied by enzyme-linked immunosorbent assay (ELISA). Blood samples from healthy and Saprolegnia-infected brown trout were collected over 2 yr with a seasonal periodicity (January, April, July and October) from a hatchery and river with frequent presence of saprolegniosis (River Porma) and from a river in which the disease was rarely observed (River Omaña). The individual prevalence was 30.1%, but statistically significant differences were observed between the prevalence in trout from the hatchery (43.0%), from River Porma (31.8%) and from River Omaña (6.4%) and also between the prevalence observed in October (42.9%) and the values obtained in January (24.8%), April (22.7%) and July (27.5%). There was no difference between the seroprevalence in females (34.8%) and males (38.2%), but a positive correlation between raised serum antibody levels and larger (older) fish was found. The low prevalence of antibodies observed in Saprolegnia-infected trout (18.0%) suggests possible immune suppression and the lack of an effective specific immune response in fish with saprolegniosis.
Book
This second edition of the book Fish Diseases and Disorders, Viral, Bacterial and Fungal Infections volume 3 represents a major update on the viral, bacterial and oomycete disorders of finfish and shellfish. Since publication of the first edition (in 1999), considerable advances have been made and therefore all the chapters have been thoroughly revised. The new and more eloquent research and current techniques have extended our knowledge and understanding of these infectious organisms. Researchers from Europe, North America, Australia and Asia have been involved in updating this book. With the addition of new information, some of the older texts in the original chapters have been condensed; this is to ensure a more focused and comprehensive reviews. For this edition, deletion and/or combination a couple of the original chapters, have been made and added three new chapters (Chapter 6 on 'Alphaviruses', Chapter 7 on 'Oncogenic Viruses' and Chapter 21 on 'Genomics of Finfish and Shellfish Microbial Pathogens'), which have been written by new authors. There are 22 new authors who have offered to write new chapters and/or update many of the original chapters. The aims, philosophy, focus, audience and format of this second edition have remained unchanged, and the authors hoped that this edition will continue to be useful to colleagues.
Article
Fungal cultures attributed to the Saprolegnia parasitica-diclina complex isolated from diseased salmonids, diseased coarse fish and natural water samples, are compared critically. The two species concept is not sustained and only S. diclina Humphrey is conserved. This results in a more flexible framework for comparing isolates within this species and three groups are distinguished here, based on growth characteristics and length/breadth (L/B) ratio of the oogonium. Oospore size is also considered in this connection. In Windermere (English Lake District) only Saprolegnia diclina Type 1 (L/B ratio ≥2≥13%) occurs as a parasite on salmonid fish. Only S. diclina Type 2 (L/B ratio ≥2 ≤12%) occurs as a parasite on perch Perca fluviatilis L. Saprolegnia diclina Type 3 (L/B ratio ≥2≤10%) is purely saprophytic. An attempt is made to fit S. parasitica-diclina isolates from natural water samples into this scheme so that the potential infectivity for a particular kind of fish could be assessed.
Article
The clinical signs and histopathology of Saprolegnia sp. [related to S. diclina Humphrey (syn. S. parasitica Coker)] are described in cultured Anguilla anguilla L. elvers under an intensive production system. The main lesions observed were loss of epithelium leading to ulceration, oedema and myofibrillar degenerative changes of the muscle mass. The oedema resulted in swelling of the inter-myotomal connective tissue, loss of nuclei and minor host reaction. Traumatic lesions with subsequent bacterial infections had a mononuclear inflammatory response. It is suggested that the rapid extension of the lesion is due to the loss of integrity of the integument and the widespread oedema, which altered the viability of tissues and assisted the Saprolegnia infection. The condition was fatal for infected elvers.
Article
Juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), were experimentally infected to investigate the pathogenicity of 20 isolates of two morphotypes of long-haired Saprolegnia obtained from wild brown trout, Salmo trutta L., and river water in Spain. The trout were exposed to 2 × 105 and 3 × 105 L–1 zoospores. Saprolegnia infection could not occur without ‘ami-momi’ treatment. Pathogenicity varied greatly among isolates as mortality ranged from 0 to 100% of the fish. There was a statistically significant difference (P < 0.001) between the mortality caused by morphotype I isolates and that produced by those of morphotype II. The most pathogenic isolates usually belonged to morphotype II, consisting of isolates which had secondary cysts with bundles of hooked hairs which were shorter and less numerous than those of morphotype I; the morphotype I isolates usually had low pathogenicity. Lesions were most frequently found on the fins. Cultures detected the presence of Saprolegnia in internal organs. Histopathology of the intestine suggests that Saprolegnia may reach this and other organs via the blood stream from surface lesions.
Article
Some observations on the mycology and pathology of saprolegniasis of maturing sockeye salmon are reported. Saprolegnia spp. were isolated from all lesions examined. Some isolates did not produce oogonia and could not be identified further. The other isolates have affinities to the S. diclina-S. parasitica complex. Observations on the gross and histo-pathology of the lesions show the fungi can be active pathogens. It is hypothesized that increased levels of plasma corticosteroids and depletion of ascorbic acid reserves in the fish increase the probability that Saprolegnia spp. will initiate infections, either alone or concurrently with other opportunistic parasites.
Article
Transmission electron microscopy was used to study the ornamentation of secondary cysts of 52 long-spined Saprolegnia isolates, with and without oogonia, obtained from wild brown trout, Salmo trutta L., and water samples from various rivers in León (NW Spain). All the isolates had secondary cysts with long hooked hairs grouped in bundles, although significant individual differences were observed. There was a direct relationship between the number of bundles per cyst, the number of hairs per bundle and hair length. The isolates were classified into two morphological groups. The isolates with a higher number of bundles per cyst and bundles with a greater number and length of hairs, were included in cyst morphological Group I. The isolates with a smaller number and shorter length of these bundles and hairs were included in cyst morphological Group II. There was a relationship between the type of ornamentation of the secondary cysts and the origin of the isolates. The isolates from salmonids with saprolegniosis belonged to Group II, whereas most isolates from mucus and water belonged to Group I.