Viral Diseases of Aquatic Mammals and Fish

Which viruses of aquatic mammals occur occasionally or are of little importance?

• papillomaviruses of dolphins and manatees

• influenza

• San Miguel sea lion virus

What is the parent virus of influenza?

orthomyxovirus

What is the parent virus of San Miguel sea lion virus?

calicivirus

What viruses of aquatic mammals are of moderate importance?

• pinniped and cetacean parapox

• cetacean herpesvirus

What is the parent virus of Pinniped and Cetacean Parapox?

Poxvirus

What virus of aquatic mammals is of high importance?

Morbillivirus

What is the parent virus of Morbillivirus?

phocine distemper

The following properties match which parent virus:

• cytoplasmic replication, eveloped virions released by exocytosis, non-enveloped virions released by cell lysis

• virus is resistant to environment

• lesions proliferative and some “tumor like”

• diagnosis by clinical appearance confirmed by electron microscopy or virus isolation

• transmission by contact and mechanically by arthropods

• several are zoonotic

poxviruses

Which virus is described:

• large DNA virus

• genus parapoxvirus

• virus strains have affinity for particular host species

• zoonotic

Poxviridae

How do poxvirus infections manifest clinically?

as proliferative lesions, 2-3cm in diameter, on the skin or the mucosal surface of the mouth and nasal passages

What is commonly seen as a complication in the treatment of debilitated, stranded pinnipeds in specialized marine mammal rehab centers?

Pox lesions

Which poxvirus affects seals and walruses, and has zoonotic capability?

pinniped parapoxvirus

Since pinniped parapoxvirus has zoonotic capability, what is recommended to caretakers and handlers of seals and sea lions?

wear gloves and personal protective gear

Which poxvirus infection affects dolphins and whales?

cetacean poxviruses

In cetaceans, what is the cutaneous manifestation of reported poxvirus infections?

hyperpigmented skin lesions, variously described as “ring,” “pinhole,” and “tattoo” lesions (tattoo skin disease)

It has been suggested that poxvirus infections in cetaceans may be associatd with what?

stressful conditions, such as poor water uality, environmental contamination and underlying ill health

The following characteristics match which parent virus:

• infection rsults in characteristic eosinophilic intranuclear inclusion bodies

• infection becomes latent, with recrudescence and intermittent or continuous virus shedding

• virus is unstable in environment

• wide range of clinical presentations

• latent infections in presence of serum antibody

• diagnosis confirmed by virus isolation and PCR

• transmission by direct contact and droplet/aerosol

• mostly species specific, but some are zoonotic

herpesviruses

Which herpesvirus is associated with mucosal lesions in digestive, genital, and respiratory tracts?

Cetcean gamma herpesvirus

Which virus is described:

• Plagues on penile mucosa and vulvar mucosa

• likely transmitted by sexual contact

• history of abortion and perinatal mortality

genital herpesvirus

The following characteristics matches which parent virus:

• virus is resistant to environment

• lesions proliferative and some tumor like “warts”

• no serum antibody response

• chronic infections and do not induce long lasting immunity

• diagnois by clinical appearance confirmed by electron microscopy or PCR

• difficult to isolate in cell culture

• transmission by contact and fomites

papillomaviruses

The following characteristics matches which parent virus:

• virus is unstable in environment

• respiratory and systemic clinical presentations

• diagnosis by clinical presentation confirmed by ELISA, PCR, or virus isolation

• transmission by direct contact and droplet

paramyxoviruses

What aquatic mammal diseases are caused by paramyxoviruses?

• dolphin porpoise morbillivirus

• phocine distemper virus

Characterization of vial isolates from phocine distemper outbreaks have shown that phocine distmper virus is related but clearly distinct from what?

canine distemper virus

What clinical signs are noted in young seals affected by phocine distemper virus?

• depression

• anorexia

• crusting conjunctivitis

• nasal discharge

• dyspnea

• pneumonia develops

What vaccine was used in seals and was successful in developing protective antibodies?

canine distemper virus

Cetacean morbillivirus is also known as?

delphinoid distemper virus

Cetacean morbillivirus (delphinoid distemper virus) is closely related to what in ruminants?

rinderpest and peste de petits

Cetacean morbillivirus targets what organs primarily?

brain and lungs

What are the most common symptoms of cetacean morbillivirus?

• skin lesions

• pneumonia

• brain infections

• secondary infections due to compromised immune system

The following properties match which viruses:

• virus is relatively unstable in the environment

• predominantly cause respiratory disease but sometimes systemic

• exhibits antigenic shift and drift with many serotypes and type specific immunity

• diagnosis by clinical presentation confrimed by ELISA, PCR, or virus isolation

• transmission by direct contact, fomites, and droplet infection

influenza viruses

Which strain of influenza was responsible for the death of 162 New England harbor seals from September to December 2011 in an outbreak of pneumonia?

avian H3N8 influenza A virus

Which strain of influenza were isolated from the lung of whales?

influenza A subtypes H13N2 and H13N9

The following characteristics match which parent virus:

• virus is resistant to environment and many disinfectants

• affect many species with several clinical presentations

• viruses are heterogeneous

• chronic infections occur in the cat

• diagnosis by PCR, some difficult to isolate in cell culture

• transmission by contact and fomites

caliciviruses

Marine caliciviruses appear to be serotypes of what?

vesicular exanthema of swine virus (VESV)

What virus of aquatic mammals causes skin vesicles that erode and leave shallow, fast healing ulcers?

San Miguel Sea Lion Virus (Calicivirus)

How do we treat San Miguel Sea Lion Virus?

supportive treatment only, skin lesions resolve without treatment

San Miguel Sea Lion Virus can cause premature parturition and these affected pups have what?

interstitial penumonitis and encephalitis and fail to thrive

Which disease is economically important in the saltwater farming industry?

Infectious pancreatic necrosis

How do we diagnose infectious pancreatic necrosis in fish?

• virus isolation

• PCR

What are the clinical signs of infectious pancreatic necrosis in fish?

• abdominal swelling, abnormal swimming

• not eating

• darkening of skin

• feces trailing from vent

What can be found on necropsy of fish that were affected by infectious pancreatic necrosis?

• necrosis to pancreas

• thick mucus inside intestines

Which disease of fish is described:

• disease of young fish <6 inch fry and fingerlings of trout and salmon

• adults can carry virus without showing symptoms

• spread via infected water, also vertically

• high mortality, but some survive

• multivalent vaccine available

• breed for resistant gene

Infectious Pancreatic Necrosis

What fish are affected by infectious pancreatic necrosis?

salmonid fish (atlantic salmon in pacific NW, maine, Norway, denmark)

Which diseases of fish are econonmically important in freshwater farming industry?

• channel catfish virus disease

• Koi herpesvirus disease

• spring viremia of carp

Which disease of fish is described:

• caused by Ictalurid herpesvirus I

• very virulent in young naive populations of cultured channel catfish, <6 inch fry and fingerlings

• mortality near 100%

• latent carriers

• no vaccine

channel catfish virus disease

What are the clinical signs of channel catfish virus disease?

• distended abdomen (pot bellied)

• convulsive swimming with a head up posture

• lethargy

• exophthalmia

• hemorrhages at the base of the fins

What can be found on necropsy of fish affacted by channel catfish virus disease?

• red or yellow tinged peritoneal fluid

• enlarged spleen

• petechial hemorrhages on kidney, liver, and visceral fat

How do we diagnose channel catfish virus disease?

• virus isolation

• PCR

What are the clinical signs of Koi Herpesvirus Disease?

• excessive mucus production on gills

• gill necrosis

• sloughing of scales

• sunken eyes

• refusal to eat

How do we diagnose Koi Herpesvirus Disease?

• q-PCR

• vius isolation

• ELISA antibody

Koi herpesvirus disease is caused by what virus?

Cyprinid herpesvirus 3

What can be used to control Koi Herpesvirus disease?

dropping water temperature since the virus is dependent on warmer water

Is there a vaccine for Koi Herpesvirus disease?

Not in the US

Which fish disease is considered a foreign animal disease and must be reported?

Spring viremia of carp

Which virus causes spring viremia of carp?

Rhabdovirus carpio

How is spring viremia of carp spread/transmitted?

• blood sucking parasites, leeches and fish lice

• aquatic birds and mammals

• ovarian transmission possible

Is there a vaccine for spring viremia of carp?

not in the US

What are clinical signs of spring viremia of carp?

• often non specific but usually affects young fish

• lethargic

• decreased respirations

• loss of equilibrium

• lie on bottom of tank or along bank

• darkening of skin

• hemorrhages on body wall

• exophthalmia (pop eye)

• dropsy

• pale gills

• protruding vent

How do we diagnose spring viremia of carp?

• q-PCR

• virus isolation

• ELISA antibody

How do we treat viral diseases of fish?

• not many therapeutic approaches, avoidance and prevention are major tools

• culling

• vaccines if available

• genetically resistant fish via breeding

• understanding biology of virus