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| − | {{review}}
| + | #REDIRECT[[:Category:Piroplasmida]] |
| − | {{toplink
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| − | |backcolour =
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| − | |linkpage =Parasites
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| − | |linktext =PARASITES
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| − | |pagetype=Bugs
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| − | |sublink1=Protozoa
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| − | |subtext1=PROTOZOA
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| − | }}
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| − | <br>
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| − | ==Introduction==
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| − | | |
| − | The '''piroplasms''' are a group of blood-borne protozoa which are transmitted by [[Ticks|ticks]]. The species of most veterinary importance are ''Babesia'', ''Cytauxzoon'' and ''Theileria''.
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| − | Piroplasms are apicomplexan protozoa which inhabit [[Erythrocytes - WikiBlood|erythrocytes]], and sometimes other cells of vertebrates, but do not form pigment from haemoglobin. All piroplasms are small and round or pear-shaped (erythrocyte forms) and are parasitic to fish, amphibians, birds and mammals.
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| − | ==''Babesia''==
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| − | [[Image:Babesia Life Cycle.jpg|thumb|right|150px|''Babesia'' Life Cycle Diagram - Dennis Jacobs & Mark Fox RVC]]
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| − | [[Image:Alternative Babesia life cycle diagram.jpg|thumb|right|150px|''Babesia'' Life Cycle - Mariana Ruiz Villarreal]]
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| − | *Infects a wide range of host species in different areas of the world
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| − | *Babesiosis has severe effects on cattle production in parts of the world
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| − | **Prevents European breeds from being successful in tropical regions where [[Ticks|ticks]] are endemic.
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| − | **Occurs sporadically in the UK and Ireland causing losses of around £8 million per year
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| − | | |
| − | '''Life Cycle'''
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| − | *Both [[Ticks#Disease Transmission|trans-stadial]] and [[Ticks#Disease Transmission|trans-ovarian]] transmission occurs
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| − | *Each female [[Ticks|tick]] produces 3000 eggs
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| − | *The [[Ticks|tick]] is the definitive host
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| − | *''Babesia'' multiplies in the red blood cells by '''budding'''
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| − | **Forms 2-4 daughter cells (species dependent)
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| − | **Giemsa blood smears can differentiate between species using 'Difquik' stain
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| − | | |
| − | *''Babesia'' species are either small or large depending on the size of the daughter cells
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| − | *Small ''Babesia''
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| − | **E.g. ''B. divergens''
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| − | **E.g. ''B. gibsoni''
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| − | **Peripheral nucleus
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| − | **Obtuse angle
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| − | *Large ''Babesia''
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| − | **E.g. ''B. major''
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| − | **E.g. ''B. canis-complex''
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| − | **Central nucleus
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| − | **Acute angle
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| − | | |
| − | *Daughter cells disrupt the red blood cell and are released
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| − | **Spread and infect other red blood cells
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| − | | |
| − | *Antigen is released which adsorbs onto other red blood cells
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| − | **Causes haemolysis and [[Pigmentation and Calcification - Pathology#Haemoglobin|haemoglobin pigmentation]]
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| − | **Causes haemolytic anaemia, haemoglobinuria and fever
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| − | *Cattle
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| − | **Sudden onset
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| − | **Often fatal if untreated
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| − | **Causes 'pipestem' faeces
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| − | **Clumping of red blood cells in brain capillaries can occur causing neurological signs
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| − | '''Epidemiology'''
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| − | *Determined by:
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| − | **Number of infected [[Ticks|ticks]] seeking a blood meal ('''tick pressure''')
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| − | **Calves under 9 months are refractory to disease
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| − | ***Can develop immunity if exposed without showing clinical signs
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| − | **'Premunity' (a good protective immunity) develops quickly in infected cattle causing a 'carrier state'
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| − | **Immunity can wane in the absence of re-infection
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| − | **Uninfected cattle remain susceptible
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| − | *Predisposing factors:
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| − | **Susceptible animals introduced into an infected area
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| − | **Infected [[Ticks|ticks]] introduced into a clean area
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| − | **Infected cattle introduced into an area with clean [[Ticks|ticks]]
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| − | **Temporary reduction in the [[Ticks|tick]] population decreasing the transmission rate (causing enzootic instability)
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| − | **Infected are transported or stressed in other ways, e.g. parturition
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| − | *In the UK
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| − | **Sporadic disease
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| − | **Enzootic instability
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| − | **Occurs mostly during the spring and autumn during periods of greatest [[Ticks|tick]] activity
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| − | **Occurs mostly in stressed cattle under 2 years old on rough grazing
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| − | **''B. divergens'' the most common species
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| − | **[[Hard Ticks - UK#Ixodes spp.|''Ixodes ricinus'']] is the vector
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| − | **[[Ticks#Disease Transmission|Trans-ovarial]] transmission to the next generation occurs
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| − | **''B. major'' occurs in South East England but is not pathogenic
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| − | ***Vector is [[Hard Ticks - UK#Important Hard Ticks|''Haemaphysalis'']]
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| − | *Overseas
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| − | **''B. bovis'' causes considerable losses in cattle in many tropical and sub-tropical areas
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| − | ***In Australia an attenuated vaccine is used
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| − | ***Vector is [[Hard Ticks - Overseas|''Boophilus'']]
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| − | **''B. bigemina'' causes problems in Africa and South America
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| − | ***Vector is [[Hard Ticks - Overseas|''Boophilus'']]
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| − | *Dogs
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| − | **Complex epidemiology
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| − | **Recognised species are extending their endemic ranges due to the discovery of the small ''Babesia'' species, pet passport scheme and increased overseas travel
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| − | **Large species comprises 3 subspecies
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| − | ***''B. canis canis'' is the most important
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| − | ****[[Hard Ticks - Overseas|''Dermacentor'']] vector
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| − | ****Largely confined to southern Europe but is spreading
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| − | ***''B. canis'' uses [[Hard Ticks - Overseas|''Rhipicephalus'']] as a vector and is spreading northwards through Europe
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| − | ***''B. gibsoni'' is now established in the USA and South-East Asia
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| − | **British dogs have no immunity as no species are endemic to the UK so are highly susceptible if taken abroad
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| − | **Prevention of [[Ticks|tick]] bites by use of an 'Amitraz' collar is currently the best method of protection
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| − | *Horses
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| − | **2 species occur
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| − | **''B. equi'' is the most pathogenic
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| − | **Not endemic to the UK
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| − | **Serology using ELISA or IFAT to diagnose
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| − | *Sheep and goats
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| − | **Several species
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| − | **Little clinical significance
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| − | ===Enzootic Instability===
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| − | *Low rate of transmission
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| − | *Few infected [[Ticks|ticks]]
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| − | *Infrequent exposure
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| − | *Immunity wanes or is completely absent in many individuals
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| − | *Low levels of herd immunity
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| − | *'''Higher''' incidence of disease
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| − | ===Enzootic Stability===
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| − | *High rate of transmission
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| − | *Many infected ticks
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| − | *Frequent exposure boosts immunity
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| − | *High level of herd immunity
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| − | *'''Lower''' incidence of disease
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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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| − |
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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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| − |
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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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| − |
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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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| − |
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| − | *Merozoites are then believed to enter erythrocytes to form the intraerythrocytic stage
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| − |
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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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| − |
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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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| − |
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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''
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| − | ==''Theileria''==
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| − | [[Image:Theileria parva life cycle.jpg|thumb|right|150px|''Theileria parva'' Life Cycle Diagram - Dennis Jacobs & Mark Fox RVC]]
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| − | [[Image:Lymph node smear East Coast Fever.jpg|thumb|right|150px|Lymph node smear of a cow with East Coast Fever - Drs. Elizabeth Howerth and Bruce LeRoy, Department of Pathology, UGA College of Veterinary Medicine]]
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| − | [[Image:H and E stain brain East Coast Fever.jpg|thumb|right|150px|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]]
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| − | [[Image:Theileria cervi.jpg|thumb|right|150px|''Theileria cervi'' (deer) - Drs. Elizabeth Howerth and Bruce LeRoy, Department of Pathology, UGA College of Veterinary Medicine]]
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| − | *Main species of veterinary importance is ''Theileria parva''
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| − | **Causes '''East Coast Fever'''
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| − | ***Severe, proliferative lymphatic disease of cattle
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| − | ***Central and Eastern Africa
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| − | ***Transmitted by [[Hard Ticks - Overseas|''Rhipicephalus appendiculatus'']]
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| − | ***[[Ticks#Disease Transmission|Trans-stadial]] transmission
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| − | *Other ''Theileria'' species cause production losses in cattle and sheep in the Middle East, Mediterranean and in Northern Africa
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| − | '''Life Cycle'''
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| − | *Incubation phase lasts 1 week
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| − | *Lymphoblast proliferation
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| − | **Local [[Lymph Nodes - Anatomy & Physiology|lymph node]] first infected then spreads through body
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| − | **Occurs in week two
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| − | *Lymphoid depletion
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| − | **[[Lymphocytes - WikiBlood|Lymphocytes]] killed
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| − | **Decreases lymphopoiesis
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| − | **Occurs in week 3
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| − | *Total incubation period takes about 18 days
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| − | '''Diagnosis'''
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| − | *Clinical signs
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| − | **Pyrexia
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| − | **Enlarged local [[Lymph Nodes - Anatomy & Physiology|lymph node]]
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| − | ***Usually parotid [[Lymph Nodes - Anatomy & Physiology|lymph node]] as [[Hard Ticks - Overseas|''Rhipicephalus appendiculatus'']] feeds in the ear
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| − | **Loss of condition
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| − | *Examine Giemsa stained smears of:
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| − | **Local [[Lymph Nodes - Anatomy & Physiology|lymph node]] aspirated for schizonts
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| − | **Blood smears for piroplasms in red blood cells
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| − | *Post-mortem
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| − | **Pulmonary oedema
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| − | **Gut mucosal haemorrhages
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| − | **[[Lymph Nodes - Anatomy & Physiology|Lymph node]] and [[Spleen - Anatomy & Physiology|splenic]] cellular atrophy
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| − | '''Control'''
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| − | *Integrated control of both the [[Tick Control|tick vector]] and disease
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| − | **[[Vaccines - WikiBlood|Vaccination]] and [[Ectoparasiticides]]
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| − | *Current [[Vaccines - WikiBlood|vaccination]] is live unattentuated
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| − | **Contains frozen stabilate of ground up tick gut containing infective sporozoites
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| − | **Long lasting oxytetracycline administered at the same time to slow down schizogony giving the immune response time to develop
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| − | ==[[Protozoa Flashcards - Wikibugs#Piroplasmida|Piroplasmida Flashcards]]==
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