ArticlePDF Available

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

January 2016
Bulletin of the European Association of Fish Pathologists 36(2):95-100

Authors:

José M Aller-Gancedo

University of Leon

Juan M Fregeneda-Grandes

University of Leon

María José García-Iglesias

University of Leon

Show all 5 authorsHide

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.

Content uploaded by Juan M Fregeneda-Grandes

Content may be subject to copyright.

Content uploaded by Juan M Fregeneda-Grandes

Content may be subject to copyright.

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).

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

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.

Mortalities in cultured Pangasianodon hypophthalmus due to oomycete Saprolegnia parasitica infection in Uttar Pradesh, India

Article

Full-text available

Apr 2022

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.

Distribution and environmental preferences of Saprolegnia and Leptolegnia (Oomycota) species in fish hatcheries in Hungary

Article

Full-text available

Oct 2024
AQUACULTURE

We studied for the first time the abundance and species distribution of water molds (Oomycota, Saprolegniales) in fish hatcheries in Hungary, with a focus on Saprolegnia and Leptolegnia spp. A total of 182 water mold isolates were obtained from different developmental stages of fish (eggs, fry, and adults) and water samples collected during the spawning season of cyprinids and salmonids. Of the ten water mold species identified based on their ITS–rDNA sequences, S. parasitica, S. ferax, and S. australis were the most abundant. Statistical analyses of species proportions in relation to the sample source and host preference revealed that S. parasitica was significantly more abundant in the host than in water samples, whereas the opposite trend was observed for S. ferax and S. australis. In addition, our results confirmed previous findings that S. australis and S. ferax prefer warm water (+21–24 °C) and that S. parasitica has a wide temperature tolerance (+3–24 °C). The DNA sequence identity analysis showed that the species demarcation criterion for Saprolegnia spp. was approximately 98 % identity, based on ITS–rDNA sequences. Furthermore, our phylogenetic analyses suggest that taxonomic revision of Leptolegnia spp. is necessary.

Molecular Epidemiology, Virulence Traits and Antimicrobial Resistance Signatures of Aeromonas spp. in the Critically Endangered Iberochondrostoma lusitanicum Follow Geographical and Seasonal Patterns

Article

Full-text available

Jun 2021

Despite the fact that freshwater fish populations are experiencing severe declines worldwide, our knowledge on the interaction between endangered populations and pathogenic agents remains scarce. In this study, we investigated the prevalence and structure of Aeromonas communities isolated from the critically endangered Iberochondrostoma lusitanicum, a model species for threatened Iberian leuciscids, as well as health parameters in this species. Additionally, we evaluated the virulence profiles, antimicrobial resistance signatures and genomic relationships of the Aeromonas isolates. Lesion prevalence, extension and body condition were deeply affected by location and seasonality, with poorer performances in the dry season. Aeromonas composition shifted among seasons and was also different across river streams. The pathogenic potential of the isolates significantly increased during the dry season. Additionally, isolates displaying clinically relevant antimicrobial resistance phenotypes (carbapenem and fluroquinolone resistance) were detected. As it inhabits intermittent rivers, often reduced to disconnected pools during the summer, the dry season is a critical period for I. lusitanicum, with lower general health status and a higher potential of infection by Aeromonas spp. Habitat quality seems a determining factor on the sustainable development of this fish species. Also, these individuals act as reservoirs of important antimicrobial resistant bacteria with potential implications for public health.

The Importance of Baseline Health Surveillance Efforts in Freshwater Fish Conservation Using the Threatened Iberian Leuciscids as an Example

Article

May 2024
J WILDLIFE DIS

Freshwater fish species are experiencing the highest decline among vertebrates in this century. Although a great effort has been made to identify and tackle threats to the conservation of this taxa, several knowledge gaps still exist particularly for noncommercial endangered species, including considerations regarding fish health status. These species face deteriorating environmental conditions in their natural habitats that may lead to stress and increased risk for infectious disease outbreaks. Establishing health surveillance is crucial to identify and predict physiologic disruption in fish populations. Additionally, information retrieved may be used to direct targeted efforts to contribute to improving the conservation status of these species. We used threatened Iberian leuciscids as a case study to discuss the current knowledge regarding their health surveillance and to suggest recommendations for the establishment of practical health assessments that can benefit conservation plans for these species and be implemented in threatened or endangered freshwater fish species plans globally.

Winter saprolegniosis in channel catfish

Article

Full-text available

Sep 1992

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'.

Electron Microscopy of Infection by Saprolegnia spp. in Channel Catfish

Article

Full-text available

Jan 1991
J AQUAT ANIM HEALTH

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.

Prevalence of serum antibodies against Saprolegnia parasitica in wild and farmed brown trout Salmo trutta

Article

Full-text available

Feb 2009

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.

Saprolegnia and other Oomycetes

Book

Feb 2011

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.

Saprolegnias of salmonid fish in Windermere: A critical analysis

Article

Apr 2006
J FISH DIS

L. G. WILLOUGHBY

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.

The pathology of Saprolegnia infection of Anguilla anguilla L. elvers

Article

Apr 2006
J FISH DIS

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.

Experimental pathogenicity in rainbow trout, Oncorhynchus mykiss (Walbaum), of two distinct morphotypes of long‐spined Saprolegnia isolates obtained from wild brown trout, Salmo trutta L., and river water

Article

Dec 2001
J FISH DIS

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.

Observations on saprolegniasis of adult sockeye salmon, Oncorhynchus nerka (Walbaum)

Article

Jan 2006
J FISH BIOL

Gordon Neish

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.

Rapid preliminary screening of Saprolegnia on fish

Article

Apr 2006
J FISH DIS

L. G. WILLOUGHBY

Ultrastructural analysis of Saprolegnia secondary zoospore cyst ornamentation from infected wild brown trout, Salmo trutta L., and river water indicates two distinct morphotypes amongst long‐spined isolates

Article

Oct 2008
J FISH DIS

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.