Changes

Also known as: ''''' Nematode in fish '''''—'''''Nematoda ''''.

Also known as: ''''' Nematode in fish '''''—'''''Nematoda ''''.

==Introduction==

==Introduction==

Nematodes infect freshwater, marine and brackish water fish species.  Pathology normally occurs within the intestines but can infect all organs and substantial damage to the host can occur. Some nematodes cause high levels of fish mortality in wild fish populations.  

Nematodes infect '''freshwater, marine''' and '''brackish water fish species'''.  Pathology normally occurs within the '''intestines''' but can infect all organs and substantial damage to the host can occur. Some nematodes cause high levels of fish mortality in wild fish populations. Nematodes can infect fish as adults but larval stages of piscivorous birds, mammals or reptiles, or less frequently of predatory fishes nematodes can also infect fish species.  

''Anguillicola'', ''Philometra'', ''Skrjabillanus'', ''Anisakis'' are a few of the species that are '''zoonotic'''.  Adult stages of ''Anisakis spp''., ''Pseudoterranova spp''., ''Phocascaris spp''. and ''Contracaecum spp'' occur in whales and seals, whereas their third-stage larvae occur in fish musculature. '''Ingestion of uncooked infected fish meat''' poses a zoonotic threat to humans.  Following ingestion by humans the larvae are activated by high temperatures, acidic pH and pepsinogen within the stomach. They penetrate the gastric or intestinal mucosa, resulting in '''stomach cramps and abdominal pain'''. The worms can also migrate to other areas of the body.  Nematodes also cause an economic threat to the market value of fish, through consumer attitudes towards the presence of these parasites within food products.  Infected fillets are rejected and can increase production costs.  Disease is mainly found within wild fish populations as captive fish are feed non-infected feed.

Some nematodes are '''zoonotic''' and include species such as ''Anguillicola'', ''Philometra'', ''Skrjabillanus'', and ''Anisakis''.   '''Ingestion of uncooked infected fish meat''' poses a zoonotic threat to humans.  Following ingestion by humans the larvae are activated by high temperatures, acidic pH and pepsinogen within the stomach.  

 

Nematodes also cause an economic threat to the market value of fish, through consumer attitudes towards the presence of these parasites within food products.  Infected fillets are rejected and can increase production costs.  Disease is mainly found within wild fish populations as captive fish are feed non-infected feed.

==Signalment==

==Signalment==

Nematodes can infect fish as adults but larval stages of piscivorous birds, mammals or reptiles, or less frequently of predatory fishes nematodes can also infect fish species.  Fish within niche habitats tend to have a narrow host range compared to fish species found all over the world.  Severe disease can arise when a nematode colonises a new host species for example nematodes of Japanese eel, ''A. crassus'' causes mild disease but  in  European and American eel species it causes more severe pathology.  ''Skrjabillanid'' genera (''Skrjabillanus tincae'', ''Skrjabillanus cyprini'', ''Molnaria Intestinalis'', ''Sinoichthyonema amuri'', infect only one host, whereas ''Capillaria'' species can colonise numerous fish species.   

Fish within niche habitats tend to have a narrow host range compared to fish species found all over the world.  Severe disease can arise when a nematode colonises a new host species for example nematodes of Japanese eel, ''A. crassus'' causes mild disease but  in  European and American eel species it causes more severe pathology.  ''Skrjabillanid'' genera (''Skrjabillanus tincae'', ''Skrjabillanus cyprini'', ''Molnaria Intestinalis'', ''Sinoichthyonema amuri'', infect only one host, whereas ''Capillaria'' species can colonise numerous fish species. 

 

Adult stages of ''Anisakis spp''., ''Pseudoterranova spp''., ''Phocascaris spp''. and ''Contracaecum spp'' occur in whales and seals, whereas their '''third-stage larvae''' occur in '''fish musculature'''.   

Nematodes can affect a wide range of species including eels, sturgeons, bream, pike, cod, trout, carp,bass, rays, skate, bleaks, arapaima, perches, piranha zander, lingcod, viviparous blenny (European eelpout) and aquairium species such as guppy (millionfish) and discus fish.  They can also infect mammals such as ''Cetacea'' (Whales, dolphins and  Porpoises) and ''Phocidae'' (seals).  

Nematodes can affect a wide range of species including eels, sturgeons, bream, pike, cod, trout, carp,bass, rays, skate, bleaks, arapaima, perches, piranha zander, lingcod, viviparous blenny (European eelpout) and aquairium species such as guppy (millionfish) and discus fish.  They can also infect mammals such as ''Cetacea'' (Whales, dolphins and  Porpoises) and ''Phocidae'' (seals).  

==Clinical Signs==

==Clinical Signs==

The nematodes deprive their host of food and can feed of host tissues, sera and blood causing emaciation and anaemia.  Clinical signs of fish nematodes vary and can range from deformed body shape, haemorrhage, mortality, traumatic enteritis ,loss of balance through damage to their swim bladder, reduced swimming performance, lethargy, reduced sexual display rate, ulceration of gill cover, fraying of fins, large nodules on the ventral surface of the skin and fish can be seen on swimming or floating on their sides. Infected fish can be more susceptible to decreased oxygen content in the water. Pathogen such as Philonema and Philometra can cause atrophy or destruction of gonads, ascites and distension of the abdomen.

The nematodes deprive their host of food and can feed of host tissues, sera and blood causing '''emaciation and anaemia'''.  Clinical signs of fish nematodes vary and can range from deformed body shape, haemorrhage, mortality, traumatic enteritis ,loss of balance through damage to their swim bladder, reduced swimming performance, lethargy, reduced sexual display rate, ulceration of gill cover, fraying of fins, large nodules on the ventral surface of the skin and fish can be seen on swimming or floating on their sides. Infected fish can be more susceptible to decreased oxygen content in the water. Pathogen such as Philonema and Philometra can cause atrophy or destruction of gonads, ascites and distension of the abdomen.

 

==Epidemiology==

==Epidemiology==