DNA viruses Flashcards
List of DNA viruses
herpesviridae
asfarviridae
Hepadnaviridae
Poxviridae
Adenoviridae
Papillomaviridae
Parvoviridae
Circoviridae
herpes viruses shape and size
- 200-250nm in diameter
- double stranded DNA in icosahedral capsid
herpes viruses cell entry and replication
- enter cells by fusing with membrane
- replicate in nucleus (DNA virus)
herpes virus once in body is:
- latent in sensory ganglia, disease manifests when stressed
herpes virus in the environment is
- labile in environment (need close contact for transmission)
- quarantine is effective for control
herpes virus infects what types of cells?
Infect epithelial or endothelial cells
* Skin
* Mucous membranes
* Tracheal mucosa
* Liver
* Brain
active infections of herpes virus results in?
Active infection results in cell death
* Ulcers
* Erosions
* Hepatocellular necrosis
* Vasculitis
bovine herpesvirus 1 subtypes
Three Subtypes: BHV1.1, 1.2 (1.2a, 1.2b)
* BHV1.1: Respiratory (infectious bovine rhinotracheitis- IBR) and reproductive (abortion)
* BHV 1.2: Genital (infectious pustular valvovaginitis)
* 1.2a: abortions/1.2b: no abortions
infectious bovine rhinotracheitis (IBR)
- BHV-1 (bovine herpes virus) subtype 1.1
- Aerosol transmission (nose-to-nose contact)
- Virus replicates in the mucous membranes of the upper respiratory tract
- Becomes latent in the trigeminal ganglia
- Reactivated in times of stress
- Large amounts of virus are shed in nasal secretions
- Strong immunity develops but secondary bacterial infections can result in severe disease
Respiratory disease
* Rhinitis
* Tracheitis
* Predisposes to secondary bacterial pneumonia – bovine respiratory disease complex
Reproductive disease
* Viremia in pregnant cows and infection of the fetus results in abortion
* Multifocal hepatic necrosis in the fetus with intranuclear inclusions
Equine herpesvirus 1 strains
Two strains: EHV1 D752, N752
* A single nucleotide change results in more severe disease
* D752 – respiratory (rhinopneumonitis)/reproductive (abortion)/ neurologic
* N752 – respiratory/reproductive/non-neurologic
equine rhinopneumonitis
- EHV-1 and EHV-4
- Aerosol transmission (nose-to-nose contact)
- Virus replicates in the mucous membranes of the upper respiratory tract and regional lymph nodes
- Becomes latent in the trigeminal ganglia
- Reactivated in times of stress
- Large amounts of virus are shed in nasal secretions
equine rhinopneumonitis respiratory disease
- rhinitis
- tracheitis
- may extend into lungs especially in young animals
Equine Rhinopneumonitis reproductive disease
- Viremia in pregnant mares results in abortion
- EHV-1 has a predilection for vascular endothelium resulting in placental vasculitis and thrombosis
- Multifocal hepatic necrosis in the fetus with intranuclear inclusions
Equine Herpes Myeloencephalopathy
- Typically associated with the D752 strain EHV-1
- Follows an outbreak of respiratory disease or abortion on the farm
- The neurologic form is reportable in Virginia to the State Veterinarian
- Vasculitis, necrosis, and hemorrhage in the spinal cord and brain
Canine herpesvirus 1
- Aerosol or in utero transmission (through the placenta)
- Virus replicates in the mucous membranes of the upper respiratory tract, pharynx, and tonsils
- Becomes latent in the trigeminal ganglia
- Reactivated in times of stress
- Large amounts of virus are shed in nasal and vaginal secretions
- DIFFERENCE: Replication is most efficient in temperatures BELOW body temperature
Canine herpesvirus 1 and whelping/puppies
- Neonatal pups are most susceptible, especially in the first 3 weeks of life (hard time regulating body temp)
- If the dam is infected within 3 weeks of whelping, the puppies will be infected through the placenta
- The entire litter may be affected
- Morbidity and mortality are high
- The dam will develop immunity and subsequent litters will be unaffected
- Dead puppies will have multifocal necrosis in multiple organs, and hemorrhage in the kidneys with intranuclear inclusions
feline herpesvirus 1
- Aerosol transmission (nose-to-nose contact)
- Virus replicates in the mucous membranes of the upper respiratory tract and conjunctivia
- Becomes latent in the trigeminal ganglia
- Reactivated in times of stress
- Large amounts of virus are shed in nasal secretions
feline viral rhinotracheitis
Accounts for 40% of respiratory disease in cats
Acute upper respiratory tract infection
* Sneezing
* Hypersalivation
* Conjunctivitis
Can lead to ulcerative keratitis
Secondary bacterial infections can result in pneumonia
feline viral rhinotracheitis
Accounts for 40% of respiratory disease in cats
Acute upper respiratory tract infection
* Sneezing
* Hypersalivation
* Conjunctivitis
Can lead to ulcerative keratitis
Secondary bacterial infections can result in pneumonia
porcine herpesvirus 1
“Aujeszky’s disease” in pigs
“Pseudorabies” in other species
* PHV-1 is the only one of these alphaherpesviruses that can infect other species but it is not zoonotic (not people)
* Pseudorabies eradication has been successful in US swine herds, but wild pigs may still be infected
Aujeszky’s Disease
Porcine herpesvirus 1
* Aerosol transmission (nose-to-nose contact)
* Virus replicates in the epithelium of the oropharynx and tonsils
* Spreads to regional lymph nodes and brain via the cranial nerves
* Becomes latent in the trigeminal ganglia
* Reactivated in times of stress
* Large amounts of virus are shed in nasal secretions, milk, and semen
* Mortality can reach almost 100% in suckling pigs
* Neurologic signs predominate in young pigs
* Infections of sows can result in abortion with hepatic necrosis and intranuclear inclusions in the fetus
* Pseudorabies in other species manifests as severe neurologic disease and pruritis (itchiness) and death within a few days
gammaherpes viruses similarities
- Infect lymphocytes
- Produce latent infection in lymphocytes
- Can cause neoplastic transformation
- dont cause disease in HOST species
malignant catarrhal fever
gammaherpes virus
Types:
* Ovine gammaherpesvirus 2 (Sheep associated)
* Alcelaphine gammaherpesvirus 1 (Wildebeest) associated
* Caprine gammaherpesvirus 2 (Goat associated)
There is no clinical disease in natural reservoir hosts
Severe disease can occur in susceptible hosts
Transmission between susceptible hosts does not occur
Species affected:
* Cattle
* Deer
* Giraffes
* Pigs
* Bison
malignant catarrhal fever clinical signs
Vasculitis (hemorrhage) and primary necrosis of epithelium
Corneal edema (blue eyes)
Mucopurulent nasal discharge
Gastrointestinal and bladder hemorrhage
Neurologic disease
Cutaneous disease
Fatal lymphoproliferative disease
parvoviruses similarities
- Replicate in the nucleus of rapidly dividing cells (ex: crypt epithelial cells, leukocytes, and the developing fetus), Forms intranuclear inclusion bodies
- Stable in the environment (Does not require direct contact with infected animals to transmit)
- Resistant to heat, solvents, disinfectants, pH changes
- Biosecurity is key to limiting transmission to healthy animals
- SMALL (Range in size from 18 – 26 nm in diameter)
- Linear, single stranded DNA genome
- DNA is converted to double stranded DNA by host DNA polymerase
- Canine parvovirus, mink enteritis virus, and raccoon parvovirus are host-range mutants of feline panleukopenia virus
feline panleukopenia
feline parvovirus
* Endemic in unvaccinated cats
* Disease occurs primarily in weaned kittens after maternal antibody wanes
* Seasonal pattern is related to the birth of kittens
* Transplacental infection results in
* Fetal death (abortion) or
* Cerebellar hypoplasia
* Virus shedding through feces results in contaminated environments
* Transmission is through inhalation or ingestion
* Viral replication in the oropharynx and regional lymph nodes
* Viremia develops in 24 hours and the virus infects mitotically active cells (Intestinal crypts, Bone marrow, Thymus, Lymph node, Spleen)
* Destruction of infected cells results in villous atrophy and panleukopenia (low macrocytes)
feline panleukopenia clinical signs
- depression vomiting
- diarrhea
- fetal death/abortion
- intention tremors (cerebellar ataxia)
- death secondary to dehydration and secondary infection
canine parvovirus
- High morbidity and mortality
- Pups infected in utero died of myocarditis and heart failure until the adults developed immunity
- most common disease seen is acute enteric disease in dogs between weaning and 6 months of age
- mutates, new variants emerge (2a, 2b, and 2c)
- Transmission is through ingestion
- Viral replication in the oropharynx and Peyer’s patches
- Viremia develops in 24 hours and the virus infects mitotically active cells (Intestinal crypts, Bone marrow, Thymus, Lymph node, Spleen)
- Destruction of infected cells results in villous atrophy and immune suppression
canine parvovirus clinical signs
- Clinical signs
- Depression
- Vomiting
- Bloody diarrhea
- Fetal death through myocardial necrosis
- Death occurs secondary to dehydration and endotoxemia (toxins from bacteria)
porcine parvovirus
- An important cause of reproductive failure worldwide
- Sows are immune in endemic farms but gilts may be susceptible to infection during mating and pregnancy
- The virus targets mitotically active cells in the fetus
- Transplacental infection occurs 10-14 days after infection
- Damage to the fetus usually occurs before 70 days gestation (before the fetus develops immunity)
No diarrhea, just abortion
porcine parvovirus and age of fetus infection
The age of the fetus determines the outcome
* Infection of embryos – resorption and infertility
* Before day 70 – still birth or mummification
* After day 70 – pigs are born alive and healthy
SMEDI: Stillbirth Mummification Early embryonic Death Infertility
General parvovirus similarities for All
Virus infects rapidly dividing cells
Virus is extremely stable in the environment
canine and feline parvovirus similarities
Primarily enteric
May be some fetal death/abortion
Cats are more likely to have panleukopenia
In utero infection in cats can result in cerebellar hypoplasia
key concepts pox viruses
- Unlike other DNA viruses, pox viruses replicate in the cytoplasm
- Intracytoplasmic inclusions instead of intranuclear
- Poxviruses are the largest viruses that cause disease in domestic animals
- Enveloped, double stranded DNA viruses
- Stable in the environment under dry conditions
- Generalized infections result in cell-associated viremia
- Systemic infection results in life-long immunity
- Local infections develop transient immunity and recurrence is possible
pox viruses transmission
- Aerosol
- Direct contact
- Mechanical (insects)
general pox virus infection clinical signs
Infection usually results in raised skin lesions that progress to scabs
* Viral proteins are released (including epidermal growth factor) resulting in epidermal proliferation
* Endothelial infection results in vasculitis
capripox viruses
- Causes generalized infection and characteristic skin lesions
- Eradicated from the US (foreign animal/reportable diseases)
- Sheep pox and goat pox
- Lumpy skin disease in cattle
avipox viruses types
Fowl pox
* Affects chickens and turkeys
* Causes lesions on the head and oral mucous membranes
* Transmitted by biting arthropods
Pigeon pox
Turkey pox
suipoxvirus
pigs
mild skin disease
transmitted by pig louse
parapoxvirus
All parapoxviruses are transmissible to humans
Orf
* Affects young sheep
* Lesions around the muzzle and lips
Bovine papular stomatitis
* Affects young calves
* Lesions on the muzzle, tongue and esophagus
Pseudocowpox
* Lesions are common on the teat
* Causes milker’s nodules in people
Orf
parapox virus, transmissable to humans
Affects young sheep
Lesions around the muzzle and lips
bovine papular stomatitis
parapoxvirus, transmissable to humans
Affects young calves
Lesions on the muzzle, tongue and esophagus
pseudocowpox
parapoxvirus, transmissable to humans
Lesions are common on the teat
Causes milker’s nodules in people
leporipoxviruses
effect squirrel and rabbit
effect mesenchymal cells (connective tissue)
rabbit myxoma virus
leporipoxvirus
* Cottontail rabbits are the natural host and develop only mild disease
* effect mesenchymal cells (connective tissue)
* European rabbits develop severe disease with swelling of the facial and periocular tissues
* The virus was introduced to Europe, Australia, and Chile as a biological control measure
squirrel fibroma virus
leporipoxvirus, effect mesenchymal cells (connective tissue)
cause fibromas in squirrels
