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→Babesia
'''Epidemiology'''
'''Epidemiology'''
*Determined by:
**Number of infected [[Suborder: Metastigmata, ticks|ticks]] seeking a blood mean ('''tick pressure''')
**Calves under 9 months are refractory to disease
***Can develop immunity if exposed without showing clinical signs
**Premunity developes quickly in infected cattle which causes a 'carrier state'
**Immunity can wane in the absense of re-infection
**Uninfected cattle remain susceptible
*Enzootic Instability
**Low rate of transmission
**Few infected [[Suborder: Metastigmata, ticks|ticks]]
**Infrequent exposure
**Immunity wanes or is completely absent in many individuals
**Low levels of herd immunity
**'''Higher''' incidence of disease
*Enzootic Stability
**High rate of transmission
**Many infected ticks
**Frequent exposure boosts immunity
**High level of herd immunity
**'''Lower''' incidence of disease
*Predisposing factors:
**Sucseptible animals introduced into an infected area
**Infected [[Suborder: Metastigmata, ticks|ticks]] are intorduced into a clean area
**Infected cattle are introduced into an area with clean [[Suborder: Metastigmata, ticks|ticks]]
**Temporary reduction in the [[Suborder: Metastigmata, ticks|tick]] population decreasing the transmission rate (causing enzootic instability)
**Infected are transported or stressed in other ways, e.g. parturition
*In the UK:
**Sporadic disease
**Enzootic instability
**Occurs mostly during the spring and autumn during periods of greatest [[Suborder: Metastigmata, ticks|tick]] activity
**Occurs mostly in stressed cattle under 2 years old on rough grazing
**''B. divergens'' the most common species
**[[Suborder: Metastigmata, ticks#Ixodes spp.|''Ixodes ricinus'']] is the vector
**[[Suborder: Metastigmata, ticks#Disease Transmission|Trans-ovarial]] transmission to the next generation occurs
**''B. major'' occurs in South East England but is not pathogenic
***Vector is [[Suborder: Metastigmata, ticks#Important Hard Ticks|''Haemaphysalis'']]
==''Theileria''==
==''Theileria''==