Herpesviridae (Exam 2) Flashcards
What are the general characteristics of herpesviridae?
Large
Enveloped
Icosahedral
Latency!!!
What are the subfamilies of herpesviridae?
Alphaherpesvirinae
Betaherpesvirinae
Gammaherpresvirinae
What are the general characteristics of alphaherpesvirinae (5)?
Restricted natural host range
Cause more severe disease than in other herpesvirus species
Rapid replication and lysis of tissue
Rapid cytopathic effect in cell culture
Latency established in sensory ganglia and lymphoid tissues
What are the general characteristics of Betaherpesvirinae (4)?
Highly restricted host range
Slow replication
Cytomegalia in cells
Latency in secretory glands, lymphoreticular cells, kidneys
What are general characteristics of Gammaherpresvirinae (4)?
Restricted host range
Replication in lymphoblastoid (T or B) cells, some viruses cause oncogenic transformation
Some viruses can cause lytic infections in epitheloid and fibroblastic cells
Latency in lymphoid tissue
What are the specific structural components of herpesviridae?
Enveloped, lipid, pleomorphic, contains glycoproteins
Tegument, amorphous contains proteins
Icosahedral nucleocapsid
Fragile in the environment, with exceptions
Where does replication occur in herpesviridae?
Nucleus
Describe the 3 types infection for herpesviridae
- Lytic infection
- Latent (persistent) infection)
- Reactivation/recrudescence
What are the steps of the lytic infection of herpesviridae? (5)
- Entry via direct fusion with cell membrane
- Nucleocapsid is transported to and the genome released into the nucleus of the cell
- Early, middle, late gene structures transcribed and translated
- Virus assembles in the nucleus and buds through the nuclear and cell membranes
- Infectious virus is released by cell lysis
What are the steps of the latent infection of herpesviridae? (3)
- Entry of alphaherpesvirus into sensory nerve endings and transport of nucleocapsids to neuronal cell body and nucleus
- Viral DNA occurs as episomes in 1% of neurons in a ganglia
- Latency-associated transcripts (LAT) are expressed during latency
What are the steps of reactivation of herpesviridae? (5)
- Stimulated by stress, UV light, hormonal changes associated with menstrual cycle, pregnancy, parturition, fever, decreased immune function due to age, malnutrition, and immunodeficiencies
- Limited replication occurs in neurons
- Virions are transported down axons and released from neurons
- Lytic replication occurs in epithelial cells/other tissues, produces infectious virus
- Limited by the immune response
What is the etiologic agent of Infectious Bovine Rhinotracheitis?
Bovine herpesvirus-1 (BHV1)
What are diseases/symptoms caused by bovine herpesvirus-1?
Infectious bovine rhinotracheitis (IBR), “rednose”, necrotic rhinitis/tracheitis
Conjunctivitis, pinkeye, keratitis, corneal ulcers
Pustular vulvovaginitis, balanoposthitis
Abortions, neonatal disease
What is the host range of bovine herpesvirus-1?
Bovidae, wild ruminants
How is bovine herpesvirus-1 transmitted?
Nose-to-nose contact, inhalation of aerosolized respiratory secretions
Genital secretions, venereal transmission, AI with contaminated semen
Iatrogenic via administration of MLV vaccines to pregnant cows and neonates
How is bovine herpesvirus-1 shed?
Remains latent in tonsils, lymphoid tissues, trigeminal and sacral ganglia for life, with periodic recrudescence and shedding from the respiratory and reproductive tracts
Describe the steps of infection of an animal with bovine herpesvirus-1 (diagram)
What is one virus associated with bovine respiratory disease complex?
“Shipping fever” aka
Infectious bovine rhinotracheitis (bovine herpesvirus-1)
What are the clinical signs of infectious bovine rhinotracheitis?
Acute onset
Fever
Depression, anorexia
Profuse nasal discharge
Red (hyperemic) crusty nose
Open-mouth breathing, extending neck, “husky” cough
Fibrinonecrotic tracheitis, hemorrhagic, suppurative, and interstitial or bronchopneumonia
When do abortions occur with infectious bovine rhinotracheitis?
From 4-8 months of gestation following infection of dam
Describe how infectious bovine rhinotracheitis abortions can be iatrogenic
2 to 12 weeks following vaccination of pregnant cows with modified live vaccines
What group is primarily infected with infectious pustular vulvovaginitis?
Primarily dairy cows (artificial insemination)
What are the clinical signs of infectious pustular vulvovaginitis?
Acute onset of fever, depression, anorexia
Swollen vulva, pustules progressing to ulcers of the vaginal mucosa
Severe cases: necrotic vaginitis with fatalities
Balanoposthitis in bulls, ulcers on the penis and preputial mucosae
What are symptoms of neonatal disease caused by bovine herpesvirus-1?
Weak calves, failure to thrive
Diarrhea, gastroenteritis
Pneumonia
How is neonatal disease created iatrogenically?
By administration of live BVDV and IBR containing vaccines or combined infections with very young calves
What is the etiological agent of herpesviral meningoencephalitis?
Bovine herpesvirus-5 (or BHV-1)
What are the symptoms of herpesviral meningoencephalitis infection?
Meningoencephalitis
Sporadic cases in feedlot cattle; some in dairy calves
Nonsuppurative, necrotizing meningoencephalitis
Where is BHV-5 found latent?
Trigeminal ganglion, midbrain, thalamus, olfactory nerve
What is the host range of herpes meningoencephalitis?
Domestic cattle
What are the etiologic agents of equine rhinopneumonitis?
Equine herpesvirus-1 and equine herpesvirus-4
What are the symptoms of equine rhinopneumonitis?
Rhinoneumonitis: acute respiratory infection w EHV-1 or EHV-4
Abortion: EHV-1 most commonly
Neurologic disease: EHV-1 (encephalomyelelitis, encephalomyelopathy)
What is the host range of equine rhinopneumonitis?
Horses
More than 90% of horses and infected by 1 year of age
How is equine rhinopneumonitis transmitted?
Respiratory route highly contagious
Aerosolized respiration secretions, direct contact, fomites, hands
How is equine rhinopneumonitis shed?
Latent in trigeminal ganglion and lymphoid tissue
Shed in aerosolized secretions from nasopharynx, inapparent shedding
What are the clinical signs of rhinopneumonitis?
Fever, serous nasal discharge, mucopurulent pneumonia
Subclinical infections common
Abortion 2-8wks post-infection
Where do outbreaks of rhinopneumonitis occur?
In young horses
Introduction of new stock, transport to shows, racetrack or breeding facilities
exposure to acutely or latently infected horses (no clinical signs) during a period of recrudescence and shedding of a virus
Describe the clinical presentation of abortion with equine rhinopneumonitis
Abortions: dead foals 4-11 months gestational age
Cell-associated viremia following respiratory infection of the mare
Abortions occur 2-8 weeks post-infection
Neonatal foal mortality: systemic disease, interstitial pneumonia
May occur regardless of vaccination status of the mare
What is the clinical presentation of herpesviral encephalomyelitis?
Acute onset of neurological signs (however, the disease is a subacute process)
Neuroligic signs depend on the location of lesions in the CNS
Hindlimb “lameness,” ataxia, toe-dragging
Paralysis of bladder, tail, penis
Recumbency
What is the pathogenesis of herpesviral encephalomyelitis?
Virus replicates in nasal/respiratory epithelium
Cell-associated viremia
Virus replication in endothelial cells
Causes vasculitis in CNS
Vascular damage leads to hemorrhage and thrombosis
Focal areas of ischemic necrosis in CNS
What is frequently reported prior to onset of disease of equine herpesviral encephalomyelitis?
Stress (transport, training, competition)