Ch.43DzesoftheReproTract.PT2 Flashcards
What is the most prevalent viral cause of equine pregnancy loss?
equine herpesvirus 1 (EVH-1)
What is the primary route of transmission of EHV-1?
via respiratory tract
Once EHV-1 invades the respiratory epithelium, what is the next step in pathogenesis?
-establishes a leukocyte associated viremia
–>establishesa chronic, possibly life long latent infection
During the initial infection with EHV-1, placental endothelial cells are infected by the virus and transiently present targets to the immune system.
What major part of the immune system is inactivated by EHV-a?
inactivates MHC-1 (major histocompatibility complex-1)– which allows EHV-1 to evade the immune system b/c it stops the ability of cells to present viral particles
In pregnant mares, what is the pathophysiology of reproductive loss/abortion caused by EHV-1?
-after resp infection
-viremia
-infects fetus via transplacental migration of virus bearing leukocytes
-abortion occurs d/t rapid separation of the placenta, causing suffocation of the fetus
What is the time period between infection with EHV-1 and abortion?
Variable: between less than 2 weeks and several months
As with all herpesviruses, EHV-1 establishes a latent infection that makes recrudensce after what?
-after stressful events, such as:
-weaning
-translocation
-introduction of a new animal
-other illnesses
What material is highly contagious from an EHV-1 abortion?
aborted, infected fetal materials are highly contagious
What is the primary lesion of EHV-1?
necrotizing vasculitis and thrombosis resulting from lytic infection of the capillary endothelium
Stage of pregnancy at which abortion occurs with EHV-1
variable: vasculitis is most pronounced from fifth to ninth months of gestation
**95% of abortions occur in the last trimester of pregnancy
What are gross lesions seen on the fetus aborted d/t EHV-1 infection?
-minimal signs of autolysis
-inc fluid in the thoracic and abdominal cavities
-congestion and edema fo the lungs
-hepatomegaly with multifocal, small (~1mm), yellow to white necrotic foci
-subcutaneous edema
-icterus
Histologically, what lesions are seen on the fetus aborted due to EHV-1?
-areas of necrosis in lymphoid tissue, liver, adrenal cortex and the lung
**large intranuclear eosinophilic inclusion bodies0hyperplastic necrotizing bronchiolitis
-Other poss lesions: mild multifocal, necrotizing lesions int eh liver and adrenal cortex
-hyperplastic, necrotizing bronchiolitis
What tissues should be submitted for testing from an aborted fetus, that is to be suspected to aborted d/t EHV-1?
-placenta
-lung
-liver
-spleen
-thymus
When should vaccination to pregnant mares be administered, targeting protection against EHV-1?
5, 7 and 9 months of gestation
If an abortion is caused by EHV-1, what preventative measures should be taken?
-fetal membranes transported away from area w/o contaminating the surrounding environment
-the stall which the mare aborted should be disinfected with a phenolic or iodinophilic compound
-prevent bedding from contaminating other areas on farm
**all pregnant mares on infected farm should remain until foaled
-no horse should leave the farm until 3 to 4 weeks after last abortion
Causative agent of equine viral arteritis?
equine viral arteritis virus (EAV)
What is the primary target of equine viral arteritis virus (EAV)?
vascular endothelial cells and macrophages
Shortly after infection with equine viral arteritis virus (EAV), where can it be found within the horse?
-infects macros and later lymph nodes
-then infects circulating monos
**systemic distribution in 3 days after primary infection–> carrier state
-w/in 1 week EAV infects BV endothelium
abortion caused by equine viral arteritis virus (EAV) is likely due to?
myometritis and vasculitis–> fetal anoxia/placental hypoxia
(secondary to compression of myometrial vessels by edema and decreased progesterone production by the placenta
equine viral arteritis virus (EAV) C/S
+/- absent or highly variable
-pyrexia
-depression
-anorexia
-leukopenia
-limb edema
-stiffness of gait
-rhinorrhea and epiphora
-conjunctivitis
-rhinitis
-urticarial rash
-localized or diffuse edema
-abortion
After infection with equine viral arteritis virus (EAV), when does abortion typically occur?
3 to 10 months of gestation, follows onset of C/S several days up to 2 months
is infection with equine viral arteritis virus (EAV) fatal?
-rarely fatal in adults
-typically fatal to neonates d/t interstitial pneumonia & secondary bacterial infections
What clinical pathological lesions are seen with equine viral arteritis virus (EAV)?
**variable and inconsistent & nonspecific
-hypoxia, hypercapnia
-respiratory or metabolic acidosis
-lymphocytosis or lymphopenia
-neutrophilia or neutropenia
-thrombocytopenia
-hyperfibrinogenemia
What are the most common gross lesions seen with equine viral arteritis virus (EAV)?
edema
congesetion
hemorrhage of the subcu and lymphoid tissues and viscera