Difference between revisions of "Piroplasmida"

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'''[[Babesia|''Babesia'']]
 
'''[[Babesia|''Babesia'']]
  
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'''[[Cytauxzoon|''Cytauxzoon felis'']]
  
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==''Cytauxzoon felis''==
 
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*Cytauxzoon is classified in the order ''Piroplasmida'' and family ''Theileriidae''
 
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**This family has both an erythrocytic and a tissue (leukocytic) phase
 
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*The ''Babesiidae'', a related family, is characterized by having a primarily erythrocytic phase in the mammalian host
 
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**Its morphological features are indistinguishable from the erythrocytic form of Cytauxzoon
 
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*''Cytauxzoon felis'', ''B. equi'', and ''B. rodhaini'' have been linked to both the babesias and theilerias by RNA gene sequence analysis
 
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**It has been suggested that these organisms be reclassified within a separate family
 
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'''Life Cycle'''
 
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*Large schizonts of ''C. felis'' develop in [[Macrophages - WikiBlood|macrophages]]
 
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**In Theileria the exoerythrocytic stage occurs primarily within [[Lymphocytes - WikiBlood|lymphocytes]]
 
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*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
 
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*Later in the course of the disease, schizonts develop buds (merozoites) that separate and eventually fill the entire host cell
 
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*Each schizont may contain numerous merozoites
 
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**Ultrastructurally, schizonts lack a parasitophorous vacuole, and individual merozoites possess rhoptries
 
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*The host cell ruptures, releasing merozoites into the tissue fluid and blood
 
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*Merozoites are then believed to enter erythrocytes to form the intraerythrocytic stage
 
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*Merozoites appear in [[Macrophages - WikiBlood|macrophages]] one to three days before they are observed in [[Erythrocytes - WikiBlood|erythrocytes]]
 
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'''Pathogenicity'''
 
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*[[Ticks|Ticks]] are implicated as the natural vector for ''Cytauxzoon''
 
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**Most cases of infection have been associated with the presence of these parasites on the hosts
 
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**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. 
 
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*Clinically, the disease in cats is characterized by fever, depression, dyspnoea, anorexia, lymphadenopathy, anaemia and icterus leading to death in three to six days
 
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*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
 
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*Microscopically, numerous large schizonts are present within the cytoplasm of endothelial-associated [[Macrophages - WikiBlood|macrophages]]
 
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**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]]
 
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**Minimal inflammatory reaction is present in tissues
 
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'''Diagnosis'''
 
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*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
 
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**Are 1-5 micrometers in diameter
 
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**Small, peripherally placed basophilic nucleus
 
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*Organisms that must be distinguished from the intraerythrocytic phase of ''C. felis'' include ''Babesia'' and ''Hemobartonella''
 
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**The blood stage may appear similar to the ring forms of ''Hemobartonella'' and to the piriforms of ''Babesia''
 
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**Unlike ''Cytauxzoon'', ''babesiosis'' and ''hemobartonellosis'' do not have a tissue stage of infection
 
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*Differential diagnosis for the tissue phase of ''cytauxzoonosis'' includes other small (less than 5 μm), intrahistiocytic organisms such as ''Toxoplasma'', ''Leishmania'' and ''Histoplasma''
 
  
 
==''Theileria''==
 
==''Theileria''==

Revision as of 22:29, 9 April 2010

Babesia

Cytauxzoon felis


Theileria

Theileria parva Life Cycle Diagram - Dennis Jacobs & Mark Fox RVC
File:Lymph node smear East Coast Fever.jpg
Lymph node smear of a cow with East Coast Fever - Drs. Elizabeth Howerth and Bruce LeRoy, Department of Pathology, UGA College of Veterinary Medicine
File:H and E stain brain East Coast Fever.jpg
H and E stain of brain and meningal vessels of a cow with East Coast Fever - Drs. Elizabeth Howerth and Bruce LeRoy, Department of Pathology, UGA College of Veterinary Medicine
Theileria cervi (deer) - Drs. Elizabeth Howerth and Bruce LeRoy, Department of Pathology, UGA College of Veterinary Medicine
  • Main species of veterinary importance is Theileria parva
  • Other Theileria species cause production losses in cattle and sheep in the Middle East, Mediterranean and in Northern Africa

Life Cycle

  • Incubation phase lasts 1 week
  • Lymphoblast proliferation
    • Local lymph node first infected then spreads through body
    • Occurs in week two
  • Lymphoid depletion
    • Lymphocytes killed
    • Decreases lymphopoiesis
    • Occurs in week 3
  • Total incubation period takes about 18 days

Diagnosis

  • Examine Giemsa stained smears of:
    • Local lymph node aspirated for schizonts
    • Blood smears for piroplasms in red blood cells
  • Post-mortem

Control

  • Current vaccination is live unattentuated
    • Contains frozen stabilate of ground up tick gut containing infective sporozoites
    • Long lasting oxytetracycline administered at the same time to slow down schizogony giving the immune response time to develop

Piroplasmida Flashcards
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