Ceratomyxa shasta
Encyclopedia
Ceratomyxa shasta is a myxosporea
n parasite that infects salmonid
fish
on the Pacific coast of North America. It was first observed at the Crystal Lake Hatchery, Shasta County, California
, and has now been reported from Idaho
, Oregon
, Washington, British Columbia
and Alaska
(Bartholomew et al. 1989).
worm
(Bartholomew et al., 1997). Actinospores are released from the worm, and infect fish, on contact, in the water column. Neither horizontal (fish to fish), nor vertical (fish to egg) transmissions have been documented under laboratory conditions, suggesting that the worm host is necessary for completion of the life cycle.
Spores are released back into freshwater system after its fish host dies, however the complete life cycle, host and vector interaction is not fully understood (especially the ecology of the polychaete host).
Research indicates that the potential for infection is enhanced when water temperatures are high, water flow is low, or numbers of infectious C. shasta are relatively high. Infection rates appear to be higher in or below still water environments than river
ine ones.
, ascites
, exopthalmia
and kidney
pustules, These symptoms vary from one salmonid species to another, and also depend on life stage of the host.
Internally, infection with C. shasta affects entire digestive tract, liver
, gall bladder, spleen
, gonads, kidney
, heart
, gill
s, and muscle
tissues. Infection with C. shasta in adult chinook salmon
causes mortality through intestinal perforations and co-occurring bacterial infections.
Cold temperatures and salinity may reduce progress of disease, but do not eliminate infection. Progression of infection and mortality is temperature dependent, with higher temperature increasing disease progression and resulting in quicker mortality.
.
Myxosporea
The Myxosporea are a class of microscopic parasites, belonging to the Myxozoa. They have a complex life cycle which comprises vegetative forms in two hosts, an aquatic invertebrate and an ectothermic vertebrate, usually a fish. Each host releases a different type of spore...
n parasite that infects salmonid
Salmonidae
Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes and graylings...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
on the Pacific coast of North America. It was first observed at the Crystal Lake Hatchery, Shasta County, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, and has now been reported from Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....
, Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, Washington, British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
and Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
(Bartholomew et al. 1989).
Life history
In addition to the fish host, C. shasta infects a freshwater polychaetePolychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
worm
Worm
The term worm refers to an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, and stems from the Old English word wyrm. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical...
(Bartholomew et al., 1997). Actinospores are released from the worm, and infect fish, on contact, in the water column. Neither horizontal (fish to fish), nor vertical (fish to egg) transmissions have been documented under laboratory conditions, suggesting that the worm host is necessary for completion of the life cycle.
Spores are released back into freshwater system after its fish host dies, however the complete life cycle, host and vector interaction is not fully understood (especially the ecology of the polychaete host).
Research indicates that the potential for infection is enhanced when water temperatures are high, water flow is low, or numbers of infectious C. shasta are relatively high. Infection rates appear to be higher in or below still water environments than river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
ine ones.
Pathology of infection
Clinical indications of infection in salmons include lethargy, loss of body mass, darkening of the skinSkin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
, ascites
Ascites
Ascites is a gastroenterological term for an accumulation of fluid in the peritoneal cavity.The medical condition is also known as peritoneal cavity fluid, peritoneal fluid excess, hydroperitoneum or more archaically as abdominal dropsy. Although most commonly due to cirrhosis and severe liver...
, exopthalmia
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
and kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
pustules, These symptoms vary from one salmonid species to another, and also depend on life stage of the host.
Internally, infection with C. shasta affects entire digestive tract, liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, gall bladder, spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
, gonads, kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
, gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s, and muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
tissues. Infection with C. shasta in adult chinook salmon
Chinook salmon
The Chinook salmon, Oncorhynchus tshawytscha, is the largest species in the pacific salmon family. Other commonly used names for the species include King salmon, Quinnat salmon, Spring salmon and Tyee salmon...
causes mortality through intestinal perforations and co-occurring bacterial infections.
Cold temperatures and salinity may reduce progress of disease, but do not eliminate infection. Progression of infection and mortality is temperature dependent, with higher temperature increasing disease progression and resulting in quicker mortality.
Disease Resistance
Salmonid stocks exhibit variable resistance to C. shasta (Bartholomew 1998). Resistance is variable and may be compromised by environmental conditions which enhance infectivity. Salmonid stocks which are resistant to C. shasta are not necessarily resistant to other myxosporean infections, such as Myxobolus cerebralisMyxobolus cerebralis
Myxobolus cerebralis is a myxosporean parasite of salmonids that causes whirling disease in farmed salmon and trout and also in wild fish populations...
.