Identification of Fish Identification of Fish ParasitesParasites

Sameer G ChebbiSameer G ChebbiIndustrial Fish and FisheriesIndustrial Fish and Fisheries

Dept. of ZoologyDept. of ZoologyKarnatak Science College,Karnatak Science College,

DharwadDharwad

TrypanosomaTrypanosoma TrypanosomaTrypanosoma is   is  genusgenus of  of kinetoplastidskinetoplastids (class Kinetoplastida), a  (class Kinetoplastida), a 

monophyleticmonophyletic group of unicellular  group of unicellular parasiticparasitic  flagellateflagellate  protozoaprotozoa. . All trypanosomes are heteroxenous (requiring more than one All trypanosomes are heteroxenous (requiring more than one

obligatory host to complete life cycle) and most are transmitted obligatory host to complete life cycle) and most are transmitted via a via a vectorvector.  .  

The majority of species are transmitted by blood-The majority of species are transmitted by blood-feeding invertebrates, but there are different mechanisms among feeding invertebrates, but there are different mechanisms among

the varying species. the varying species. In an invertebrate host they are generally found in the intestine, In an invertebrate host they are generally found in the intestine,

but normally occupy the bloodstream or but normally occupy the bloodstream or an intracellular environment in the vertebrate host.an intracellular environment in the vertebrate host.

T. sinipercaeT. sinipercae, in fishes causes the sucks the blood and it will leads , in fishes causes the sucks the blood and it will leads to secondary infection.to secondary infection.

Piscine Piscine haemoflagellateshaemoflagellates swim freely in the blood. Members of the swim freely in the blood. Members of the genus genus TrypanosomaTrypanosoma are spindle shaped, 25–95 μm long, a single  are spindle shaped, 25–95 μm long, a single

flagellum originating from a usually apical flagellum originating from a usually apical kinetoplastkinetoplast is connected is connected longitudinally to the trypanosome body by an undulating longitudinally to the trypanosome body by an undulating

membrane. membrane. The nucleus is usually single, except in the course of division and The nucleus is usually single, except in the course of division and

centrally positioned.centrally positioned. Natural infection with Natural infection with trypanosomestrypanosomes may be very common, may be very common,

particularly where the leech vector is also common.particularly where the leech vector is also common. At present the only practical means which may be recommended At present the only practical means which may be recommended

is environmental control by elimination of leeches. is environmental control by elimination of leeches.

Ichthyophthiriasis multifilis:Ichthyophthiriasis multifilis:   This is probably the most common parasite of all fishes.  This is probably the most common parasite of all fishes.   The common name for this parasite and disease is “Ich” or “white spot”. The common name for this parasite and disease is “Ich” or “white spot”.

The mature parasite reaches approximately 1 mm in diameter and is The mature parasite reaches approximately 1 mm in diameter and is commonly observed in the gills and/or skin as coalescing white spots, commonly observed in the gills and/or skin as coalescing white spots, hence the common name.  hence the common name.  

The trophont or mature stage of the parasite has a large “horseshoe” The trophont or mature stage of the parasite has a large “horseshoe” shaped nucleus, and the entire surface of the parasite is covered in cilia.  shaped nucleus, and the entire surface of the parasite is covered in cilia.  

The life cycle of this parasite is direct, but is spent, in part, off of the host.  The life cycle of this parasite is direct, but is spent, in part, off of the host.   The trophont is within the epidermis of the host, until it leaves the fish, The trophont is within the epidermis of the host, until it leaves the fish,

encysts and divides to produce many host-seeking tomites.  encysts and divides to produce many host-seeking tomites.   The tomites penetrate the skin and gills of the fish to complete the life The tomites penetrate the skin and gills of the fish to complete the life

cycle.  cycle.   The life cycle is temperature dependent with a shorter life cycle occurring The life cycle is temperature dependent with a shorter life cycle occurring

at warmer water temperatures.at warmer water temperatures. Fish with a cutaneous infection  will “flash”, i.e., turn over and expose their Fish with a cutaneous infection  will “flash”, i.e., turn over and expose their

white underside, whereas fish with a gill infection will “pipe”, i.e., come to white underside, whereas fish with a gill infection will “pipe”, i.e., come to the surface of the water and “breathe” through their mouth.  the surface of the water and “breathe” through their mouth.  

Gill lesions include epithelial hyperplasia with the presence of mature Gill lesions include epithelial hyperplasia with the presence of mature trophonts within the gills.  trophonts within the gills.  

Cutaneous lesions also exhibit focal epidermal hyperplasia, with parasites Cutaneous lesions also exhibit focal epidermal hyperplasia, with parasites being located beneath the hyperplastic epidermis.being located beneath the hyperplastic epidermis.

IchthyophthiriasisIchthyophthiriasis is fatal to fish of all sizes. Chronic infection will cause is fatal to fish of all sizes. Chronic infection will cause serious damage to the skin, fin and gills; corneal infection impairs vision  serious damage to the skin, fin and gills; corneal infection impairs vision  

DactylogyrusDactylogyrus This is a group of trematodes which complete their entire life cycle on This is a group of trematodes which complete their entire life cycle on

the host.  the host.   The adults attach to the host by a haptor or opishaptor  which is a The adults attach to the host by a haptor or opishaptor  which is a

specially adapted structure on the posterior end of the parasite.specially adapted structure on the posterior end of the parasite. This organ has hooks which allow the parasite to attach firmly to the This organ has hooks which allow the parasite to attach firmly to the

host fish.   host fish.    These parasites usually cause minimal damage to fish, but will infest These parasites usually cause minimal damage to fish, but will infest

the skin, fin and gills of pond fishes.  the skin, fin and gills of pond fishes.   Severe infestations may be responsible for poor respiration and/or Severe infestations may be responsible for poor respiration and/or

emaciation.  emaciation.   The two most common monogenetic trematodes The two most common monogenetic trematodes

include:  Dactylogyrus and Gyrodactylus. include:  Dactylogyrus and Gyrodactylus.  This parasite is approximately 0.2 to 0.5 mm in length, reaching a This parasite is approximately 0.2 to 0.5 mm in length, reaching a

maximum length of 2.0 mm.  maximum length of 2.0 mm.   It has seven pairs of marginal hooks and usually one pair of median It has seven pairs of marginal hooks and usually one pair of median

hooks on the opishaptor.  hooks on the opishaptor.   The dactylogrids have two to four pigmented spots (known as “eyes” The dactylogrids have two to four pigmented spots (known as “eyes”

or “eye spots”) in the anterior fourth of the body. or “eye spots”) in the anterior fourth of the body. All dactylogrids are oviparous with no uterus.All dactylogrids are oviparous with no uterus.

ERGASILIDAE (COPEPODA)ERGASILIDAE (COPEPODA) It is crustacean parasite in fish and It will affect many fishes of Freshwater and It is crustacean parasite in fish and It will affect many fishes of Freshwater and

euryhaline fish of many families. euryhaline fish of many families. Common in fish of all major water systems. Common in fish of all major water systems.

Several species occur in cichlids, in siluriforms and also in brackish waters. Several species occur in cichlids, in siluriforms and also in brackish waters.  Only subadult and adult females occur of fish, mostly on the gills, a few of the Only subadult and adult females occur of fish, mostly on the gills, a few of the

genus genus ParaergasilusParaergasilus, may attach to sites other than gills. , may attach to sites other than gills. The cephalothorax constitutes half or more of body length, the first of four The cephalothorax constitutes half or more of body length, the first of four

thoracopodes occurs at about mid-length. thoracopodes occurs at about mid-length. Segmentation of the thorax (except the first segment, fused with the head) and of Segmentation of the thorax (except the first segment, fused with the head) and of

the abdomen is distinct. the abdomen is distinct. The second antenna terminal segment is hook-like in The second antenna terminal segment is hook-like in ErgasilusErgasilus and three clawed  and three clawed

in in ParaergasilusParaergasilus. . Eggs are clustered in a bunch rather than arranged in a single line.Eggs are clustered in a bunch rather than arranged in a single line.

In Ergasilidae only the female is parasitic, and is found on the gills of fish. In Ergasilidae only the female is parasitic, and is found on the gills of fish. Males are free-living and there is a prolonged, free-living larval development which Males are free-living and there is a prolonged, free-living larval development which

includes three to six stages of nauplii and four to six stages of copepodites (lasting includes three to six stages of nauplii and four to six stages of copepodites (lasting from 10 days to over a month).  from 10 days to over a month). 

Ergasilids attached to gill filaments produce small foci of erosion; apparently feeding Ergasilids attached to gill filaments produce small foci of erosion; apparently feeding involves excretion of proteolytic enzymes for external digestion. Such erosion involves excretion of proteolytic enzymes for external digestion. Such erosion

processes occur in processes occur in E. megacheirE. megacheir infections in cichlids. infections in cichlids. Erosion and degradation processes may extend beyond the epithelial lining, resulting Erosion and degradation processes may extend beyond the epithelial lining, resulting

in obstructed branchial blood vessels. in obstructed branchial blood vessels. Irritation often results in responsive hyperplasia of the epithelium, which, as infection Irritation often results in responsive hyperplasia of the epithelium, which, as infection

is prolonged, may extend over large areas of the gills, causing fusion and embedding is prolonged, may extend over large areas of the gills, causing fusion and embedding of lamellae, with a resulting decrease in the respiratory function of the gills  of lamellae, with a resulting decrease in the respiratory function of the gills 

Lernaea cyprinaceaLernaea cyprinacea Lernaea cyprinaceaLernaea cyprinacea, an opportunistic species infecting fish of many families., an opportunistic species infecting fish of many families. The rod-shaped, unsegmented, or partly segmented parasitic stage lernaeid female is The rod-shaped, unsegmented, or partly segmented parasitic stage lernaeid female is

anchored, with the aid of a specialised holdfast organ, to the host skin or buccal anchored, with the aid of a specialised holdfast organ, to the host skin or buccal mucosa. mucosa.

Larval stages, copepodites and copepod-shaped males are attached to the gills.Larval stages, copepodites and copepod-shaped males are attached to the gills. Differentiation to lernaeid genera and to species in the genus Differentiation to lernaeid genera and to species in the genus LernaeaLernaea is based  is based

mainly on the morphology of the holdfast organ (anchors) of the parasitic females. mainly on the morphology of the holdfast organ (anchors) of the parasitic females. The growth and branching of the latter, however, is greatly affected by the The growth and branching of the latter, however, is greatly affected by the

consistency of the tissue into which the holdfast organ is anchored. consistency of the tissue into which the holdfast organ is anchored. Both copepodites infecting gills, and females infecting any site on the fish Both copepodites infecting gills, and females infecting any site on the fish

integument, may harm the fish. integument, may harm the fish. Heavy infection of gills by copepodites of Heavy infection of gills by copepodites of L. barnimianaL. barnimiana or  or L. cyprinaceaL. cyprinacea causes  causes

damage to the tissue which is in immediate contact with the parasite and stimulates damage to the tissue which is in immediate contact with the parasite and stimulates extensive hyperplasia of the entire gill epithelium. extensive hyperplasia of the entire gill epithelium.

Copepodite infections are potentially lethal to small fish, while large fish (such Copepodite infections are potentially lethal to small fish, while large fish (such as as BagrusBagrus) will tolerate extremely heavy gill infections. ) will tolerate extremely heavy gill infections.

The attachment of the adult females to the integument stimulates an intense The attachment of the adult females to the integument stimulates an intense inflammatory response. inflammatory response.

The tissue around the anchor turns into a granuloma or necrotic lesion, and is later The tissue around the anchor turns into a granuloma or necrotic lesion, and is later transformed into a fibrotic encapsulation. transformed into a fibrotic encapsulation.

Economic losses due to infection not only results from direct harm to the fish, but Economic losses due to infection not only results from direct harm to the fish, but also from disfigurement which renders both fish grown for food and ornamental fish also from disfigurement which renders both fish grown for food and ornamental fish unsuitable for sale. unsuitable for sale.

Parasitic females of lernaeids are tolerant to organophosphate and organohalogen Parasitic females of lernaeids are tolerant to organophosphate and organohalogen insecticides. A dip in potassium permanganate.insecticides. A dip in potassium permanganate.

ARGULIDAE (BRANCHIURA)ARGULIDAE (BRANCHIURA) Argulus africanusArgulus africanus and  and Dolops ranarumDolops ranarum are opportunists and occur in diverse fish in all  are opportunists and occur in diverse fish in all

major systems. major systems. Argulids (“fish lice”) are dorso-ventrally flattened and covered dorsally by a rounded or Argulids (“fish lice”) are dorso-ventrally flattened and covered dorsally by a rounded or

horseshoe shaped carapace. horseshoe shaped carapace. Ventrally positioned head appendages are developed for attachment, four thoracic Ventrally positioned head appendages are developed for attachment, four thoracic

segments each bear a pair of bifid swimming legs. segments each bear a pair of bifid swimming legs. The abdomen is comprised of a single bi-lobed unit which contains testes or a round The abdomen is comprised of a single bi-lobed unit which contains testes or a round

seminal receptacle.seminal receptacle. ArgulusArgulus in having the second maxilla armed with a hook rather than a sucker,  in having the second maxilla armed with a hook rather than a sucker,

characteristic of the latter.characteristic of the latter. ChonopeltisChonopeltis are usually the smallest; head appendages are feeble and rudimentary,  are usually the smallest; head appendages are feeble and rudimentary,

the mouth tube found in the other argulids is absent, whereas the cup-like sucker of the mouth tube found in the other argulids is absent, whereas the cup-like sucker of the second maxilla is distinctly developed. The carapace is reduced in size and width. the second maxilla is distinctly developed. The carapace is reduced in size and width. Unlike the above argulids, which are active swimmers, Unlike the above argulids, which are active swimmers, ChonopeltisChonopeltis is not capable of  is not capable of swimming if removed from the host.swimming if removed from the host.

Species of Species of ArgulusArgulus and  and Dolops ranarumDolops ranarum are parasitic throughout life, but leave the host  are parasitic throughout life, but leave the host to moult or to lay eggs, and during this process will also change hosts. Both males and to moult or to lay eggs, and during this process will also change hosts. Both males and females may survive free living for as long as 15 days. females may survive free living for as long as 15 days.

Argulids infecting the skin or mouth of fish induce severe local damage to the Argulids infecting the skin or mouth of fish induce severe local damage to the integument. integument.

Damage is caused by the piercing proboscis stylet which enters deep into the skin's Damage is caused by the piercing proboscis stylet which enters deep into the skin's dermal layer and secretes lytic and toxic substances resulting in acute haemorrhagic, dermal layer and secretes lytic and toxic substances resulting in acute haemorrhagic, inflamed wounds.inflamed wounds.

Attachment to and crawling on the skin also causes irritation and abrasions leading Attachment to and crawling on the skin also causes irritation and abrasions leading first to proliferation and later to desquamation and erosion of the epithelium. first to proliferation and later to desquamation and erosion of the epithelium.

Damage is quickly alleviated where parasites can actively change attachment sites. Damage is quickly alleviated where parasites can actively change attachment sites. When a shift of attachment site is slowed or prevented by overcrowding, in heavy When a shift of attachment site is slowed or prevented by overcrowding, in heavy

infections, particularly with site specific parasite species, chronic inflammation infections, particularly with site specific parasite species, chronic inflammation develops, the infected surface of the integument ulcerates, the epithelium is destroyed develops, the infected surface of the integument ulcerates, the epithelium is destroyed and the dermis becomes exposed. and the dermis becomes exposed.

Both organohalogen and organophosphate insecticides effectively kill agulids with Both organohalogen and organophosphate insecticides effectively kill agulids with reliable safety margins to fish. reliable safety margins to fish. 

  PARASITIC ISOPODAPARASITIC ISOPODA Isopoda are parasites of marine fish and infections have been reported in euryhaline fish Isopoda are parasites of marine fish and infections have been reported in euryhaline fish

in estuaries. Nerocila orbignyi, a common parasite of marine and estuarine fish, including in estuaries. Nerocila orbignyi, a common parasite of marine and estuarine fish, including grey mullets .grey mullets .

A few species of cymothoid isopods (Lironeca spp.) occur in freshwater fish (apparently as A few species of cymothoid isopods (Lironeca spp.) occur in freshwater fish (apparently as marine relics).marine relics).

Opportunistic euryhaline cymothoids of several families and genera infect farmed fish in Opportunistic euryhaline cymothoids of several families and genera infect farmed fish in Southeast Asia, including cultured tilapia.Southeast Asia, including cultured tilapia.

Isopoda are the largest crustaceans found on fish (20–50 mm long). The body consists of Isopoda are the largest crustaceans found on fish (20–50 mm long). The body consists of three regions, the head is unsegmented and bears two pairs of antennae, a pair of three regions, the head is unsegmented and bears two pairs of antennae, a pair of variable sized eyes and a mouth. variable sized eyes and a mouth.

The maxilliped covers all other mouth parts, a second region, the peraeon, of 7 segments, The maxilliped covers all other mouth parts, a second region, the peraeon, of 7 segments, each with a pair of legs (peraeopods) and a six segmented pleon, with pairs of pleopods, each with a pair of legs (peraeopods) and a six segmented pleon, with pairs of pleopods, except the last which together with biramous uropods form a swimming tail pleotelson. except the last which together with biramous uropods form a swimming tail pleotelson.

The ‘cymothoid’ isopods attach to fish early in life and pass through a male stage before The ‘cymothoid’ isopods attach to fish early in life and pass through a male stage before becoming female. becoming female.

The presence of a mature female prevents male stage specimens from further The presence of a mature female prevents male stage specimens from further development. Both males and females remain permanently attached to the fish. development. Both males and females remain permanently attached to the fish.

Egg and larval development takes place in a special brood-pouch on the females ventrum. Egg and larval development takes place in a special brood-pouch on the females ventrum. Another group, the ‘gnathiid’ isopods, are marine and only parasitic during the larval Another group, the ‘gnathiid’ isopods, are marine and only parasitic during the larval

stage. stage. Isopoda may be either highly host specific, opportunistic in their choice of hosts or Isopoda may be either highly host specific, opportunistic in their choice of hosts or

facultative parasites, attaching to fish if they are weak or trapped in nets or cages. The facultative parasites, attaching to fish if they are weak or trapped in nets or cages. The host specific ones are the least harmful to their hosts. host specific ones are the least harmful to their hosts.

Even host specific species attached and causing degenerative changes in the tongue Even host specific species attached and causing degenerative changes in the tongue cartilage do not cause clinical harm to the fish.cartilage do not cause clinical harm to the fish.

With the opportunistic and facultative parasites, the degree of damage to fish varies with With the opportunistic and facultative parasites, the degree of damage to fish varies with the site of attachment and ratio between the isopod and the host. the site of attachment and ratio between the isopod and the host.

Their a priori large size is likely to cause pressure damage and abrasions, if attached to Their a priori large size is likely to cause pressure damage and abrasions, if attached to fish skin, and even more so inside the gill chamber. fish skin, and even more so inside the gill chamber.

Lesion to the integument causes hyperplasia, or desquamation and later on dermal Lesion to the integument causes hyperplasia, or desquamation and later on dermal inflammation and necrosis. Infection in the gill chamber often leads to mechanical damage inflammation and necrosis. Infection in the gill chamber often leads to mechanical damage to the lamellar structure. The parasite can also impede opercular respiratory to the lamellar structure. The parasite can also impede opercular respiratory movements.Organophosphate insecticides used for other piscine crustaceans are likely to movements.Organophosphate insecticides used for other piscine crustaceans are likely to be effective.be effective.

MICROSPORAMICROSPORA Microsporidian infection has been described from many Holarctic Microsporidian infection has been described from many Holarctic

marine and freshwater fish. There are very few reports of marine and freshwater fish. There are very few reports of infections in fish in the tropics. infections in fish in the tropics. 

Microsporidia are obligate intracellular parasites. Infected cells Microsporidia are obligate intracellular parasites. Infected cells usually enlarge to accommodate the proliferating parasite. usually enlarge to accommodate the proliferating parasite.

Such enlarged cells are termed xenomas. Within these xenomas, Such enlarged cells are termed xenomas. Within these xenomas, parasites undergo merogonous and sporogonous development parasites undergo merogonous and sporogonous development which culminates in the production of spores .which culminates in the production of spores .

Hypertrophic infected cells may reach macroscopic sizes and often Hypertrophic infected cells may reach macroscopic sizes and often yield characteristic gross pathological signs; multiple whitish yield characteristic gross pathological signs; multiple whitish nodules in tissues, or in case of the swimbladder, a significant nodules in tissues, or in case of the swimbladder, a significant thickening of the walls. thickening of the walls.

All active stages of the microsporidians develop in the host cell. All active stages of the microsporidians develop in the host cell. Two microsporidia were reported to develop within the host cell Two microsporidia were reported to develop within the host cell nucleus and and in haematopoietic cells.nucleus and and in haematopoietic cells.

The effect of microsporidian infection on the piscine host is The effect of microsporidian infection on the piscine host is variable: fish seem to survive infections, in spite of the presence variable: fish seem to survive infections, in spite of the presence of huge xenomata often pressing on and displacing important of huge xenomata often pressing on and displacing important organs, while infection by some microsporidians undoubtedly has organs, while infection by some microsporidians undoubtedly has a morbid effect on the fish. Intranuclear infection of a morbid effect on the fish. Intranuclear infection of haematopoietic cells was associated with acute anaemia. haematopoietic cells was associated with acute anaemia.

There is no routine treatment. Fumagilin DCH used to There is no routine treatment. Fumagilin DCH used to control control NosemaNosema infections in bees has been tested for efficacy in  infections in bees has been tested for efficacy in treatment of microsporidial infections in fish.  treatment of microsporidial infections in fish. 

THE ASIAN TAPE WORM THE ASIAN TAPE WORM Bothriocephalus acheilognathiiBothriocephalus acheilognathii Known world-wide from fish of the families fishes. Known world-wide from fish of the families fishes. the life history of the life history of B. acheilognathiiB. acheilognathii involves a definitive host, a  involves a definitive host, a

fish and an intermediate host, a copepod.fish and an intermediate host, a copepod. The Asian tape worm seems to be a thermophilic species. The Asian tape worm seems to be a thermophilic species. Low temperatures seem to delay or even interrupt development Low temperatures seem to delay or even interrupt development

and consequently completion of the life cycle. and consequently completion of the life cycle. At 28–30°C, 77% of the eggs hatched in the first day after At 28–30°C, 77% of the eggs hatched in the first day after

release, the remainder during the following five days. release, the remainder during the following five days. At 14–15°C, the incubation period extended to 10–28 days and At 14–15°C, the incubation period extended to 10–28 days and

was for all practical purposes interrupted below 12°C.was for all practical purposes interrupted below 12°C. Heavily infected fish have a distended abdomen. Sometimes Heavily infected fish have a distended abdomen. Sometimes

infected fish also develop a variable degree of aseptic dropsy. infected fish also develop a variable degree of aseptic dropsy. Tapeworm-infected carp suffered from high mortalities.Tapeworm-infected carp suffered from high mortalities. high mortality among heavily infected juvenile carp (90%) and high mortality among heavily infected juvenile carp (90%) and

also report pathological changes in infected fish, which include also report pathological changes in infected fish, which include pressure lesions, inflammation of the intestine and severe pressure lesions, inflammation of the intestine and severe “catarrhal-haemorrhagic enteritis” at the parasite attachment “catarrhal-haemorrhagic enteritis” at the parasite attachment point, with proliferation of the peripheral connective tissue. point, with proliferation of the peripheral connective tissue.

Several chemotherapeutic formulations, when applied in food, Several chemotherapeutic formulations, when applied in food, effectively relieved fish from infection. Drugs should be mixed effectively relieved fish from infection. Drugs should be mixed in oil (corn, soy, fish) and sprayed on to pellets or mixed with in oil (corn, soy, fish) and sprayed on to pellets or mixed with feeds at a rate of one litre per 70kg dry weight. feeds at a rate of one litre per 70kg dry weight.