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New page: {{unfinished}} {{toplink |linkpage =Viruses |linktext =VIRUSES |sublink1=Herpesviridae |subtext1=HERPESVIRUSES |pagetype =Bugs }} <br> ====Antigenicity==== *Isolates vary in virulence ba...
{{unfinished}}
{{toplink
|linkpage =Viruses
|linktext =VIRUSES
|sublink1=Herpesviridae
|subtext1=HERPESVIRUSES
|pagetype =Bugs
}}
<br>
====Antigenicity====
*Isolates vary in virulence based on tropism
*Note:
** [[Viral skin infections - Pathology#Herpesviruses|Genital pustules]] are caused by '''EHV3'''
**''EHV4'' is serotypically identical to EHV1, but can be distinguished via monoclonal antibodies, PCR and RE (restriction enzyme) profiling
====Pathogenesis====
*Entry via '''aerosol'''
*Initial replication in the [[Respiratory Viral Infections - Pathology#Equine rhinopneumonitis|upper respiratory tract]]
*By 24hrs, '''coughing''' is induced once virus has reached bronchi and pulmonary lymph tissue
*Cell-associated '''viremia''', with virus predominantly in the T cells
*'''Abortion''' can follow:
**Virus transfers from leukocytes to placental endothelium, causing '''thrombosis and ischemia'''
**95% of abortions are in the '''last trimester''', when chorionic placentomes have created an end-artery system vulnerable to ischemia
*Foals born will be weak and virus-positive
*'''Paresis''' is a rare clinical symptom caused by lesions in the CNS and resulting thrombosis
*'''Latency''' always follows infection, and the virus can be reactivated under stress
====Epidemiology====
*Aerosol infection occurs despite maternal antibody
*Over 60% of horses are latently infected and show antibody as yearlings
*Greatest threat or reinfection is to mares in late-term pregnancy
*Infected horses (coughing) can shed virus for up to 10 days
====Diagnosis====
*In the case of abortion:
**Whole fetus should be sent for testing
**Immunostaining of fetal tissues
*Nested PCR for envelope glycoproteins in '''nasal swab''': more sensitive than virus isolation
*Paired serum samples to show increase in CFT titre
====Control====
*Isolation of pregnant mares in last trimester
*No movement for at least 1 month after last abortion
*'''Vaccination''' every 6 months
**Inactivated vaccine may reduce respiratory disease but cannot protect against abortion
{{toplink
|linkpage =Viruses
|linktext =VIRUSES
|sublink1=Herpesviridae
|subtext1=HERPESVIRUSES
|pagetype =Bugs
}}
<br>
====Antigenicity====
*Isolates vary in virulence based on tropism
*Note:
** [[Viral skin infections - Pathology#Herpesviruses|Genital pustules]] are caused by '''EHV3'''
**''EHV4'' is serotypically identical to EHV1, but can be distinguished via monoclonal antibodies, PCR and RE (restriction enzyme) profiling
====Pathogenesis====
*Entry via '''aerosol'''
*Initial replication in the [[Respiratory Viral Infections - Pathology#Equine rhinopneumonitis|upper respiratory tract]]
*By 24hrs, '''coughing''' is induced once virus has reached bronchi and pulmonary lymph tissue
*Cell-associated '''viremia''', with virus predominantly in the T cells
*'''Abortion''' can follow:
**Virus transfers from leukocytes to placental endothelium, causing '''thrombosis and ischemia'''
**95% of abortions are in the '''last trimester''', when chorionic placentomes have created an end-artery system vulnerable to ischemia
*Foals born will be weak and virus-positive
*'''Paresis''' is a rare clinical symptom caused by lesions in the CNS and resulting thrombosis
*'''Latency''' always follows infection, and the virus can be reactivated under stress
====Epidemiology====
*Aerosol infection occurs despite maternal antibody
*Over 60% of horses are latently infected and show antibody as yearlings
*Greatest threat or reinfection is to mares in late-term pregnancy
*Infected horses (coughing) can shed virus for up to 10 days
====Diagnosis====
*In the case of abortion:
**Whole fetus should be sent for testing
**Immunostaining of fetal tissues
*Nested PCR for envelope glycoproteins in '''nasal swab''': more sensitive than virus isolation
*Paired serum samples to show increase in CFT titre
====Control====
*Isolation of pregnant mares in last trimester
*No movement for at least 1 month after last abortion
*'''Vaccination''' every 6 months
**Inactivated vaccine may reduce respiratory disease but cannot protect against abortion