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Created page with '==''Cytauxzoon felis''== *Cytauxzoon is classified in the order ''Piroplasmida'' and family ''Theileriidae'' **This family has both an erythrocytic and a tissue (leukocytic) pha…'
==''Cytauxzoon felis''==
*Cytauxzoon is classified in the order ''Piroplasmida'' and family ''Theileriidae''
**This family has both an erythrocytic and a tissue (leukocytic) phase
*The ''Babesiidae'', a related family, is characterized by having a primarily erythrocytic phase in the mammalian host
**Its morphological features are indistinguishable from the erythrocytic form of Cytauxzoon
*''Cytauxzoon felis'', ''B. equi'', and ''B. rodhaini'' have been linked to both the babesias and theilerias by RNA gene sequence analysis
**It has been suggested that these organisms be reclassified within a separate family
'''Life Cycle'''
*Large schizonts of ''C. felis'' develop in [[Macrophages - WikiBlood|macrophages]]
**In Theileria the exoerythrocytic stage occurs primarily within [[Lymphocytes - WikiBlood|lymphocytes]]
*In ''C. felis'', schizonts develop within mononuclear phagocytes, initially as indistinct vesicular structures and later as large, distinct nucleated schizonts that actively undergo division by true schizogony and binary fission
*Later in the course of the disease, schizonts develop buds (merozoites) that separate and eventually fill the entire host cell
*Each schizont may contain numerous merozoites
**Ultrastructurally, schizonts lack a parasitophorous vacuole, and individual merozoites possess rhoptries
*The host cell ruptures, releasing merozoites into the tissue fluid and blood
*Merozoites are then believed to enter erythrocytes to form the intraerythrocytic stage
*Merozoites appear in [[Macrophages - WikiBlood|macrophages]] one to three days before they are observed in [[Erythrocytes - WikiBlood|erythrocytes]]
'''Pathogenicity'''
*[[Ticks|Ticks]] are implicated as the natural vector for ''Cytauxzoon''
**Most cases of infection have been associated with the presence of these parasites on the hosts
**Experimentally, ''Dermacentor variabilis'' can transmit the organism from bobcats to domestic cats. In a white tiger that developed a natural, fatal infection in Florida, two female Lone Star ticks (''Amblyomma americanum'') were present on the inguinal skin.
*Clinically, the disease in cats is characterized by fever, depression, dyspnoea, anorexia, lymphadenopathy, anaemia and icterus leading to death in three to six days
*Gross findings include pale or icteric mucous membranes, petechiae and ecchymoses in the [[Lungs - Anatomy & Physiology|lung]], [[Heart - Anatomy & Physiology|heart]], [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and on mucous membranes, splenomegaly, lymphadenomegaly, and hydropericardium
*Microscopically, numerous large schizonts are present within the cytoplasm of endothelial-associated [[Macrophages - WikiBlood|macrophages]]
**Infected macrophages become markedly enlarged (up to 75μm) and may occlude the lumen of numerous vessels of many tissues, in particular the [[Lungs - Anatomy & Physiology|lungs]]
**Minimal inflammatory reaction is present in tissues
'''Diagnosis'''
*Merozoites within [[Erythrocytes - WikiBlood|erythrocytes]], best seen on peripheral blood or tissue impressions, are variable in morphology and can occur as round, oval, or signet ring-shaped bodies
**Are 1-5 micrometers in diameter
**Small, peripherally placed basophilic nucleus
*Organisms that must be distinguished from the intraerythrocytic phase of ''C. felis'' include ''Babesia'' and ''Hemobartonella''
**The blood stage may appear similar to the ring forms of ''Hemobartonella'' and to the piriforms of ''Babesia''
**Unlike ''Cytauxzoon'', ''babesiosis'' and ''hemobartonellosis'' do not have a tissue stage of infection
*Differential diagnosis for the tissue phase of ''cytauxzoonosis'' includes other small (less than 5 μm), intrahistiocytic organisms such as ''Toxoplasma'', ''Leishmania'' and ''Histoplasma''[[Category:Piroplasmida]]
*Cytauxzoon is classified in the order ''Piroplasmida'' and family ''Theileriidae''
**This family has both an erythrocytic and a tissue (leukocytic) phase
*The ''Babesiidae'', a related family, is characterized by having a primarily erythrocytic phase in the mammalian host
**Its morphological features are indistinguishable from the erythrocytic form of Cytauxzoon
*''Cytauxzoon felis'', ''B. equi'', and ''B. rodhaini'' have been linked to both the babesias and theilerias by RNA gene sequence analysis
**It has been suggested that these organisms be reclassified within a separate family
'''Life Cycle'''
*Large schizonts of ''C. felis'' develop in [[Macrophages - WikiBlood|macrophages]]
**In Theileria the exoerythrocytic stage occurs primarily within [[Lymphocytes - WikiBlood|lymphocytes]]
*In ''C. felis'', schizonts develop within mononuclear phagocytes, initially as indistinct vesicular structures and later as large, distinct nucleated schizonts that actively undergo division by true schizogony and binary fission
*Later in the course of the disease, schizonts develop buds (merozoites) that separate and eventually fill the entire host cell
*Each schizont may contain numerous merozoites
**Ultrastructurally, schizonts lack a parasitophorous vacuole, and individual merozoites possess rhoptries
*The host cell ruptures, releasing merozoites into the tissue fluid and blood
*Merozoites are then believed to enter erythrocytes to form the intraerythrocytic stage
*Merozoites appear in [[Macrophages - WikiBlood|macrophages]] one to three days before they are observed in [[Erythrocytes - WikiBlood|erythrocytes]]
'''Pathogenicity'''
*[[Ticks|Ticks]] are implicated as the natural vector for ''Cytauxzoon''
**Most cases of infection have been associated with the presence of these parasites on the hosts
**Experimentally, ''Dermacentor variabilis'' can transmit the organism from bobcats to domestic cats. In a white tiger that developed a natural, fatal infection in Florida, two female Lone Star ticks (''Amblyomma americanum'') were present on the inguinal skin.
*Clinically, the disease in cats is characterized by fever, depression, dyspnoea, anorexia, lymphadenopathy, anaemia and icterus leading to death in three to six days
*Gross findings include pale or icteric mucous membranes, petechiae and ecchymoses in the [[Lungs - Anatomy & Physiology|lung]], [[Heart - Anatomy & Physiology|heart]], [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and on mucous membranes, splenomegaly, lymphadenomegaly, and hydropericardium
*Microscopically, numerous large schizonts are present within the cytoplasm of endothelial-associated [[Macrophages - WikiBlood|macrophages]]
**Infected macrophages become markedly enlarged (up to 75μm) and may occlude the lumen of numerous vessels of many tissues, in particular the [[Lungs - Anatomy & Physiology|lungs]]
**Minimal inflammatory reaction is present in tissues
'''Diagnosis'''
*Merozoites within [[Erythrocytes - WikiBlood|erythrocytes]], best seen on peripheral blood or tissue impressions, are variable in morphology and can occur as round, oval, or signet ring-shaped bodies
**Are 1-5 micrometers in diameter
**Small, peripherally placed basophilic nucleus
*Organisms that must be distinguished from the intraerythrocytic phase of ''C. felis'' include ''Babesia'' and ''Hemobartonella''
**The blood stage may appear similar to the ring forms of ''Hemobartonella'' and to the piriforms of ''Babesia''
**Unlike ''Cytauxzoon'', ''babesiosis'' and ''hemobartonellosis'' do not have a tissue stage of infection
*Differential diagnosis for the tissue phase of ''cytauxzoonosis'' includes other small (less than 5 μm), intrahistiocytic organisms such as ''Toxoplasma'', ''Leishmania'' and ''Histoplasma''[[Category:Piroplasmida]]