Fungal Infections in Some Economically Important Freshwater Fishes

Abstract

Aim of this study was to investigate fungal infections in four species of carps
including goldfish, Carassius (C.) auratus L.; silver carp, Hypophthalmichthys (H.)
molitrix Richardsons; rahu, Labeo (L.) rohita Hamilton and Ctenopharyngodon (C.)
idella Valenciennes. Nine specimens of each species were studied for the presence
of fungal infections. Infected fishes showed clinical signs such as fungal growth on
skin, fins, eyes, eroded fins and scales, hemorrhages on body surface and abdominal
distension. The specimens from infected organs of fish were inoculated on each,
malt extract, Sabouraud dextrose and potato dextrose agars. The fungal colonies of
white, black, green, grey and brown colors were observed in the agar plates. Slides
were prepared and stained with 0.05% Trypan blue in lactophenol. C. auratus
showed the highest infection rate (44.4%) followed by H. molitrix and L. rohita
(11.1% each). Five fungal species viz. Aspergillus (33.3%), Penicillium (22.2%),
Alternaria (27.7%), Blastomyces spp (11.1%) and Rhizopus (5.5%) were isolated.
Posterior part of the fish had significantly (P=0.05) higher (62.5%) infection as
compared to anterior part (37.5%). The caudal fin with 31.25% infection was the
single most affected area. This study showed that most of the fungi isolated from
fishes are considered as normal mycoflora, yet many fungi can cause natural
infections in ponds and aquarium.

Full text

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Pakistan Veterinary Journal
ISSN: 0253-8318 (PRINT), 2074-7764 (ONLINE)
Accessible at: www.pvj.com.pk
Fungal Infections in Some Economically Important Freshwater Fishes
Zafar Iqbal*, Uzma Sheikh and Rabia Mughal
Department of Zoology, University of the Punjab, Lahore, 54590, Pakistan
*Corresponding author: dr.zafariqbal.pu@gmail.com
ARTICLE HISTORY
ABSTRACT
Received:
Revised:
Accepted:
September 12, 2011
January 22, 2012
February 18, 2012
Key words:
Carassius auratus
Ctenopharyngodon idella
Fungal infections
Hypophthalmichthys
molitrix
Labeo rohita
Aim of this study was to investigate fungal infections in four species of carps
including goldfish, Carassius (C.) auratus L.; silver carp, Hypophthalmichthys (H.)
molitrix Richardsons; rahu, Labeo (L.) rohita Hamilton and Ctenopharyngodon (C.)
idella Valenciennes. Nine specimens of each species were studied for the presence
of fungal infections. Infected fishes showed clinical signs such as fungal growth on
skin, fins, eyes, eroded fins and scales, hemorrhages on body surface and abdominal
distension. The specimens from infected organs of fish were inoculated on each,
malt extract, Sabouraud dextrose and potato dextrose agars. The fungal colonies of
white, black, green, grey and brown colors were observed in the agar plates. Slides
were prepared and stained with 0.05% Trypan blue in lactophenol. C. auratus
showed the highest infection rate (44.4%) followed by H. molitrix and L. rohita
(11.1% each). Five fungal species viz. Aspergillus (33.3%), Penicillium (22.2%),
Alternaria (27.7%), Blastomyces spp (11.1%) and Rhizopus (5.5%) were isolated.
Posterior part of the fish had significantly (P=0.05) higher (62.5%) infection as
compared to anterior part (37.5%). The caudal fin with 31.25% infection was the
single most affected area. This study showed that most of the fungi isolated from
fishes are considered as normal mycoflora, yet many fungi can cause natural
infections in ponds and aquarium.
©2012 PVJ. All rights reserved
To Cite This Article: Iqbal Z, U Sheikh and R Mughal, 2012. Fungal infections in some economically important
freshwater fishes. Pak Vet J, 32(3): 422-426.
INTRODUCTION
Freshwater fishes are an important protein source for
people of many countries (Hussain et al., 2011; Rubbani
et al., 2011). However, globally fish from freshwater and
marine sources are in severe decline, driven in large part
by economic and human population growth (Limburg et
al., 2011). Fish farming in various parts of the world has
increased many folds in the last decade. As a result, fish
culture has now become commercially an important
industry worldwide. In the Punjab province of Pakistan,
five species of carps including H. molitrix, C. idella, L.
rohita, Catla catla Hamilton and Cirrhinus mrigala
Hamilton are cultured. The establishment of 7829 fish
farms (area 45650 acres) in private sector is an indicator
of rapid growth of fisheries sector (Khan et al., 2011).The
growth of fish culture has also raised issues of fish health.
Bacterial hemorrhagic septicemia, lernaeasis, saprolegnia-
sis and anoxia are the most commonly occurring fish
diseases in pond fishes in Punjab (Iqbal et al., 2001).
Ornamental fish keeping has become an increasingly
popular hobby worldwide. The trade of ornamental fish is
a multi-million dollar industry now. Twenty species of
ornamental fishes are imported from Southeast Asian
countries into Pakistan (Ahmad, 1996). These fishes are
transported alive and sold to the hobbyists by the pet
shops. Fungi are known to attack fish eggs, fry,
fingerlings and adult fish. Water molds infections cause
losses of freshwater fishes and their eggs in both natural
and commercial fish farms (Bangyeekhun and Sylvie,
2001). The fungal diseases occur in brood stock and all
life stages of fish and eggs. Fungal infection cause low
productivity of fry and low production in fish culture
(Kwanprasert et al., 2007). The mortality rate due to
fungal infection may reach some time up to 80-100% in
incubated eggs (Chukanhom and Hatai, 2004). According
to Akande and Tobor (1992) post-harvest handling of
fishes may also result in infection with microorganisms
such as bacteria and fungi. The ubiquitous fungi are
part of the normal mycoflora of fresh and estuarine
ecosystems and have a worldwide distribution. However,
there are certain fungi which cause fish diseases.
Shahbazian et al. (2010) isolated Penicillium expansum,
Penicillium citrinium; Aspergillus terruse, Aspergillus cli-
RESEARCH ARTICLE

Pak Vet J, 2012, 32(3): 422-426.
423
vatus; Alternaria spp; Saprolegnia parasitic, Saprolegnia
lapponica, Saprolegnia ferax and Saprolegnia hypogyna
and 7 other species of fungi from infected eggs of rainbow
trout, Oncorhynchus mykiss in Iran. However, Fadaeifard
et al. (2011) isolated 8 species of fungi from eggs and
brood stock of rainbow trout O. mykiss. These isolates
were Penicillium spp, Acreomonium spp, Alternaria spp,
Fusarium solani, Aspergillus spp, Mucor spp,
Saprolegnia spp. and Cladosporium spp. Primary
infections in fishes and fish eggs by oomycetes are also
reported (Walser and Phelps, 1993). Although, infection
as a result of microbial contamination does not usually
result in disease but environmental stress may upset the
balance between the potential pathogens and their hosts.
Under such conditions the chances of infection increases.
This study was aimed to investigate the mycoflora
associated with apparently healthy as well as diseased
ornamental and culturable fishes.
MATERIALS AND METHODS
Nine goldfish, C. auratus were collected from a pet
fish shop in Lahore and nine specimens each of culturable
carps, grass carp (C. idella), silver carp (H. molitrix) and
rahu (L. rohita) were obtained from Fish Research Farms,
University of the Punjab, Lahore, Pakistan. The fishes
were transported immediately to laboratory in sterile
polyethylene bags in aerated aquarium/pond water. The
fishes were kept separate in glass aquariums with
continuous air supply at ambient temperature. Total length
(TL) and weight (Wt) of each specimen was measured and
health status of every individual fish was also observed.
The fish body was divided into two parts; Anterior part
(head, eyes and gills) and posterior part (all fins and rest
of the body) to note the infection site and data thus
obtained was analyzed by Chi-square test.
For culturing of fungal specimens, three different
types of media including malt extract agar (MEA),
Sabouraud dextrose agar (SDA) and potato dextrose agar
(PDA) were prepared and streptomycin sulphate was
supplemented to each preparation of media to avoid
bacterial contamination. The body surfaces of all the
fishes under study were disinfected by dipping each fish
in 1% formaldehyde for 1 to 5 minutes followed by 70%
alcohol and finally in sterile water in which it was
thoroughly rinsed. The fungal isolates were collected from
infected organs of fish with sterile needle and inoculated
on malt extract (Oxoid, UK), Sabouraud dextrose (Oxoid,
UK) and potato dextrose (M096-India) agars. The agar
plates were incubated at 28-30°C and fungal growth was
observed after 4-7 days. The fungal colonies of various
colors were observed in the agar plates. For microscopic
examination, slides were prepared from each colony and
stained with 0.05% Trypan blue in lactophenol. The slides
were observed under Digipro-labomed microscope and
photographed. The fungi were identified with the help of
available fungal identification keys and literature
(Willoughby, 1994).
RESULTS AND DISCUSSION
A total of 36 fishes of four species were examined
(Table1). Fungal infection was observed in C. auratus, H.
molitrix and L. rohita. However, no fungal infection was
observed in C. idella (Table 1). The clinical picture of
infected C. auratus showed fungal growth on head, gills,
eyes and fins. Additionally, infected fishes had eroded
scales and hemorrhages over body surface and moderate
body distension. Tips of caudal fin were eroded in H.
molitrix. Early infection was seen on caudal fin of L.
rohita. Posterior part of the fish had 62.5% had
significantly (χ2=3.38; P=0.05) more infection than
anterior part (37.5%) infection and Hence, the attack on
both anterior and posterior part of the fish was not equal.
The attack on the posterior part was always recorded
higher because of having 85-90% more surface area. The
single most affected site was caudal fin (31.25%). The
infection on head, gills and eyes of fish may lead to
serious pathological conditions as extensive growth of
fungal hyphae in eyes may cause complete blindness and
from eyes may penetrate into brain and in such condition
the treatment is impossible and eventually the fishes die
(Srivastava, 2009). Fin infection is considered less
pathogenic as such fishes survive but this infection may
lead to complete damage of the fins.
Table1: Infection level and site of infection in fishes.
Fish
Species
Fish
Infection
Mean
TL(cm)
Mean Wt
(g)
Site of infection in
fish
C. auratus (44.4%) 10.75±3.32 19.46±8.10 Head, eyes, gills,
fins, abdomen
H.molitrix (11.1%) 19.78±5.33 146.33±99.80 Head, Abdomen,
Caudal fin
L.rohita (11.1%) 23.56±3.61 183.89±105.71Caudal fin
C. idella (0%) 21.50±3.41 127.44±56.76 No infection
Table 2: Fungal species isolated from different organs of fishes.
Fish
species
Organ Fungal
colonies
Fungi isolated
Head a (1) Penicillium spp. C. auratus
CdF a (2) Aspergillus spp.
PcF a & b (2) Penicillium spp.
PvF and AnF a & b (2) Alternaria spp.;
Blastomyces spp.
Eye a & b Aspergillus spp.;
Alternaria spp.
Gills a (1) Alternaria spp.
C. auratus
Head a (3) Aspergillus spp.;
Penicillium spp.
CdF a (1) Rhizopus spp. C.auratus
Ab a (1) Penicillium spp.
CdF a (1) Aspergillus spp. C.auratus
Gills a (2) Blastomyces spp.
CdF a (1) Alternaria sp.
Head a (2) Alternaria spp.
H.molitrix
Ab a (1) Aspergillus spp.
L.rohita CdF A Aspergillus spp.
Note: fungal colony a (3) means, 3 colonies of which one ‘a’ was
processed for identification; colony a&b (2) means, 2 colonies and both
were processed. Abbreviations of organ studied: PcF = pectoral fin;
PvF= pelvic fin; Anf = anal fin; CdF = caudal fin; Ab = abdomen.
Five fungal genera viz. Aspergillus spp. (33.3%);
Penicillium spp. (22.2%); Rhizopus spp. (5.5%) (Fig. 1, 2,
3), Blastomyces spp. (11.1%) and Alternaria spp. (27.7%)
were isolated from C. auratus. Two genera Aspergillus
spp. and Alternaria spp. were isolated from H. molitrix.
From L. rohita only Aspergillus spp. was isolated (Table
2). Mixed fungal infection was also observed in C.
auratus, in three combinations as Alternaria spp.,
Blastomyces spp., Aspergillus spp., Alternaria spp. and
Aspergillus spp. Penicillium spp. The most prevalent
genus was Aspergillus spp. It was isolated from C.

Pak Vet J, 2012, 32(3): 422-426.
424
Fig 1: A, Colonies of Rhizopus on MEA,(fish 4,C.auratus).B, C, Rhizopus
(from plate–A) showing long branched sporangophore with sporangium
bearing spores.
auratus; H. molitrix and L. rohita. Alternaria spp. was
isolated from C. auratus; H. molitrix and Penicillium spp.,
Blastomyces spp., and Rhizopus spp. were isolated from
C. auratus only (Table 2).
Aspergillomycosis has been principally described in
African fish, especially the tilapia Oreochromis sp.
(Olufemi, 1983). A number of Aspergillus species such as
A. flavus, A. japonicus, and A. terreus are involved in this
infection. These species presumably cause infection via
entry into the fish through contaminated feed. Jalilpoor et
al. (2006) reported infection of Aspencer percicus eggs
with Penicillium spp., Fusarium spp., Mucor spp. and
Saprolegnia spp. which caused 7 and 22% mortality of
these eggs.
Fig 2: A, colonies of Aspergillus on PDA, (fish 5, C.auratus). B. Aspergillus
spp. (isolated from plate A) with round head and black conidia.
Fayioye et al. (2008) isolated five different species of
fungi including Fusarium, Aspergillus, Rhizopus, Mucor,
and Penicillum from 8 edible smoke-dried freshwater
fishes. Junaid et al. (2010) isolated 7 fungal species from
stockfish in Nigeria and these included A. flavus, A.
fumigatus, A. niger, Trihophyton verrucosum, Rhizopus
Mucor and Penicillum spp. and among these Mucor spp.
showed the highest occurrence. In another study, fungi of
eight different genera; Saprolegnia, Aspergillus,
Fusarium, Mucor, Pencillium, Rhizopus, Scopulariopsis
and Curvularia were isolated from two fish species,
Oreochromis spp. and Claris gariepinas (Refai et al.,
2010). Shahbazian et al. (2010) isolated Penicillium
expansum, Penicillium citrinium; Aspergillus terruse,
Aspergillus clivatus; Alternaria spp. and 11 other fungal
species from infected eggs of rainbow trout. Moreover,
Fadaeifard et al. (2011) reported the occurrence of
different fungal species of genera including, Penicillium,
Acreomonium, Alternaria, Fusarium, Aspergillus, Mucor,
Saprolegnia and Cladosporium from the eggs and brood
stock of rainbow trout.
Shabana (2002) reported Alternaria eichhorniae in
Nile tilapia, Oreochromis spp. A fatal behavioral disorder
of carp was attributed to cerebral infection with Alternaria
spp. probably following exposure to adverse
environmental conditions (Sharaburin and Bazderkina,
A
B
C
B

Pak Vet J, 2012, 32(3): 422-426.
425
1990). Blastomycosis is caused by Blastomyces
dermatitidis. This infection occurs by inhaling fungal
spores and it is increasingly recognized in immuno-
compromised hosts (Pappas et al., 1993).
Fig 3: A. Colonies of Penicillium on SDA, (fish 1, C. auratus). B, C,
Penicillium sp. showing brush like arrangement of fruiting head.
Findings of the present study are comparable to the
findings of Refai et al. (2010), Shahbazian et al. (2010)
and Fadaeifard et al. (2011). However, Refai et al. (2010)
has characterized Aspergillus spp., Penicillium spp. and
Rhizopus spp. as normal mycoflora and these spp. may be
regarded as opportunistic pathogens (Refai et al., 2004) as
many of them possess virulence factors which enable
them to cause disease (Refai et al., 2010), especially
under favorable predisposing conditions. Ecological
differences play an important role in species diversity of
fungi that develop on both fish and eggs (Hussein et al.,
2001). Interaction of physiochemical factors generally has
influence on the diversity of water molds (Paliwal and
Sati, 2009).
Lack of good aquarium keeping in pet shops and fish
farms increases the chances of fungal infection in fishes.
The basic health management practices may be easily
over looked due to dearth of trained personal or resources.
This study indicates that although most fungi isolated
from fishes are considered as normal mycoflora, yet they
can cause infections. This is confirmed by the presence of
fungal hyphae in the lesions on the body of the fish. These
findings point our attention to the possible role of fungi in
affecting both ornamental and culturable fishes.
Acknowledgement: We are thankful to Dr. Abdul Nasir,
Associate Professor, Department of Botany, University of
the Punjab, Lahore for authentication of fungal species
identified in the present study.
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