Virology

• submicroscopic particles
• 20 - 150 nm (1 one thousandth of a micron, 1 one millionth of a millimeter)

electron microscope

nanometer

either RNA or DNA

• only in living cells
• can exist in the environment, but can not replicate in the environment

parasites that can only replicate in living cells and can not replicate in the environment

a virus particle

virus in the blood - spreading from point A to point B

from infection till the animal shows clinical signs

about 3 - 5 days

• slower
• faster

• nucleic acids
• protein

individual viral proteins that make up the capsid.

protein covering the nucleic acids

enzymes that allow for take over of hot's biosynthetic apparatus - allows the virus to take over the cell

• RNA reverse transcriptase
• polymerases
• protein kinases

lipid and glycoprotein covering the virus to increase virulence

no

the destructiveness of the virus

from the host cell

glycoprotein spikes on the outside of the virus

helps the virus attach to the membrane of the cell

no

• Reovirus
• Rhabdovirus
• Retrovirus
• Paramyxovirus
• Orthomyxovirus
• Togavirus
• Coronavirus
• Calicivirus
• Arenavirus
• Picornavirus
• Bunyavirus

• Feline calicivirus
• Vesicular exanthema

• upper respiratory infection
• lesions in the mouth

• sheep 
• goats

• Foot and mouth disease
• Swine vesicular disease
• SMEDI
• Rhinovirus in the horse

test and slaughter

it is not seen in our country, only in other countries

upper respiratory infection

rabies

neurologic disease seen in all mammals

• reptiles
• birds

• spread by bites
• virus is in the saliva

• Texas - #1
• Virginia - #2

because we vaccinate our domestic animals

• Canine distemper
• Canine parainfluenza
• Bovine parainfluenza 3 (Bovine PI3)
• Respiratory syncytial virus
• Rinderpest

no, can affect different types of tissue in the body and can affect more than just dogs

upper respiratory infection

Rinderpest (seen in Africa)

• TGE (transmissable gastroenteritis)
• FIP
• Canine coronaviral enteritis
• Feline enteric coronavirus
• Bovine neonatal diarrhea

pigs

• EEE (eastern equine encephalitis)
• WEE (western equine encephalitis)
• VEE (venezuela equien encephalitis)
• BVD
• Hog cholera

arthropod vector

Hog cholera

no

• Rotavirus enteritis
• Bluetongue virus

enteritis and respiratory diseases

deer

no

• Oncornavirus (bovine and feline leukemia)
• Lentivirus (Caprine Encephalitis Arthritis, Equine Infectious Anemia, FIV, Visna-maedi)

by direct contact such as biting

• Pox virus
• Parvovirus
• Herpesvirus
• Adenovirus
• Papovavirus
• Iridovirus

• Cow pox
• Orf (sheep) - Contagious ecthyma
• Horse pox
• Avian pox
• Monkey pox

Avian pox

skin

no

• Infectious Bovine Rhinotracheitis
• IPV (pustular vulvovaginitis)
• Malignant catarrhal fever (hoof stock)
• Equine rhinopneumonitis
• Feline rhinotracheitis
• Canine herpes
• Marek's disease (chickens)

mostly respiratory

• Canine parvovirus
• Feline panleukopenia
• Porcine parvovirus
• Raccoon parvovirus

• Infectious canine hepatitis
• Canine adenovirus 2 (kennel cough)

• Canine adenovirus 2
• Canine parainfluenza
• Bordetella

respiratory/GI diseases

Papillomatosis (warts)

cows and dogs

West Nile virus

encephalitis

by insects

• Porcine circovirus
• Psitticine Beak and Feather Disease

Hemorrhagic diseases in primates (Ebola, Marburg, Reston)

• Attachment:  must get to cell and attach to it first
• Penetration:  penetrates the cell - pinocytosis - brings the cell in
• Uncoating:  protein coat and envelope go away - now it's a "naked cell"
• Biosynthesis:  nucleic acid from the virus gets into the nucleic acid from the cell and makes the cell stop doing it normal function and start making more of the virus
• Maturation and Release:  virus either reassembles  in the cell and destroys the cell or leaves the cell to go to another one and starts the process over again

• clinical
• subclinical
• persistent
• latent
• carrier
• slow

shows signs

does not show any signs

lingers in the body

virus is in equilibrium with the immune system - the virus is not doing anything until soemthing suppresses the immune system

shed the virus even after recovery

long incubation periods

• inhalation
• ingestion
• direct contact
• in utero

spread from animal to animal

spread from mother to offspring

• Interferon
• Macrophages
• Immunoglobulins
• Cell-Mediated Immunity

produced mostly by T-lymphocytes that then produce antiviral proteins which stops the penetration of the virus into other cells and protects the other cells

non-specific which means there isn't one for each specific virus...they work for all the viruses

monocytes

• engulf the virus
• make interleukin - 1 which is a chemical that activates T-lympohocytes to kill cells
• T lymphocytes kill the macrophages

antibodies

specific to each virus

• there is in increase in immunoglobulins M within 7 days of the first exposure to the viruse
• B lymphocytes increase in 10 - 14 days after exposure
• After 2 weeks there is an increase in immunoglobulins G
• Anamnestic (memory) response with a second exposure

• Macrophages process virus for the T cells
• T cells then become cytotoxic

clinical signs 

lab testings

suspicion of what virus it is, tests are very specific - different tests for each virus

• antibody tests
• antigen tests

tests for antibodies, can only tell us if the animal has been exposed to something and has the antibodies - does not tell us if the animal currently has the active form of the virus

determines if the virus is active in the animal

• characteristic history
• characteristic signs/lesions
• changes in CBC
• biochemical changes (relate to organ system that is affected)

• panleukopenia
• lymphopenia

once the animal is dead

intranuclear (in nucleus)

intracytoplasmic (in cytoplasm)

• electron microscopy
• immunostaining (immunofluorescence)
• radial immunodiffusion RID
• polymerase chain reaction (PCR)

in tissue/discharge

research labs

electron rays

50,000X

because they can't grow in the environment

• within 4 days of seeing signs
• within 8 hours after death

• kept cold
• sent to lab quickly
• viral transport medium used to keep bacteria under control

• cell (tissue) culture
• embryonated eggs
• animal inoculation

inject sample into cell/tissue and then look for cytopathic effects

• cell lysis
• cell agglutination
• inclusion bodies

cells that divide indefinitely in vitro for a cell culture

inject virus into specific part and then look for lesions in the embryo

• inject the disease into a live animal and then look for lesions
• mice because they are small and don't take up a lot of space

the type of virus

antibodies (indicates that the virus was present at some point in time)

titers

how great the antibody response is

• take two different types of samples (acute - right when the animal is showing signs and convalescent - after being treated)
• need to see a 4x increase in the titer for the convalescent sample

• hemagglutination
• hemagglutination inhibition
• complement fixation
• virus (serum) neutralization
• immunostaining - IFA
• AGID (agar gel immunodiffusion)
• immunoflurescence
• ELISA
• radioimmunoassay
• immunodiffusion
• complement fixation

• hemagglutination
• hemagglutination inhibition
• hemadsorption
• complement fixation
• virus (serum) neutralization

• immunostaining - IFA
• AGID (agar gel immunodiffusion)
• ELISA

immunofluorescent antibody - this test is not necessarily just an antibody test, it tests for antigens too

• direct
• indirect

• antibody to a specific virus is labeled with a fluorescent dye
• if no virus is present then the fluorescent antibody washes away

both

flurescent microscope

yellow-green fluorescence

• antigen
• antibody

yes

color change

yes

reaction of particular antigen with antibodies to form visible aggregates

• slide tests
• card tests
• tube tests

• start with particle that has antigen bound to it (RBCs, bacteria, latex)
• add sample
• if sample contains antibodies it will bind with the particle and agglutination will occur

• serially dilute sample (dilute more and more for each sample)
• add sensitized RBCs
• titer is the first tube where we see clumping (cloudy bottom) - this is the result of the test

• combine sample and virus and allow to bind
• add RBCs of appropriate species
• if antibodies are present then RBCs will bind with the virus and there will be no agglutination
• if antibodies are not present then the virus is free to attack RBCs and agglutination will be present

yes, the titer is the first tube where clumping is inhibited in the hemagglutination inhibition whereas the titer is the first tube where there is clumping for the hemagglutination test

• latex particles are coated with antibodies agglutinate when mixed with antigen
• easy to perfom
• fast results

• incubate sample with virus
• place in cell culture
• look for effects on plate
• if antibodies are present they neutralize the virus so it cannot infect cells
• if antibodies are not present, the virus infects cells and causes visible damage

• add antigen to sample
• incubate
• add complement
• wait
• add RBCs and anti-RBC serum
• if no antibodies there is hemolysis because complement is available
• if antibodies are present, then no lysis because complement was used by first Ag-Ab reaction, see red dot

• molecules separated by size and electric charge in a gel
• can look at protein and nucleic acid pattern
• nucleic acid bands are then stained

check for specific antibodies

wildlife

electrophoresis

DNA

RNA

polymerase chain reaction (PCR)

probes

• amplifies specific nucleic acids in sample
• can compare base sequence to that of known pathogen

no

antigen or antibodies in sample

special agar plate

Ab and Ag in sample migrates in agar and we see precipitation line

• coggins test
• johne's

• antibody is mixed with agar and poured onto plate - uniform distribution
• samples place in well, cut into agar and will diffuse out into agar
• at point where equal numbers of Ag as Ab the complexes will precipitate out
• size of precipitation ring correlates with amount of Ag in sample

radioactivity

• antibody to hormone is attached to filter
• add serum to the sample
• if hormone is present, it will bind to antibody on the filter
• add radioactive iodine-labeled hormone
• if hormone is not there, iodine binds to antibodies on filter
• wash (all unbounded substances will wash away)
• if hormone is present, no iodine remains

hormones

• proteinaceous infectious particles
• another class of infectious agents

influences proteins in brain cells to turn bad

no

transmissilbe spongiform encephalopathies

• bovine spongiform encephalopathy (BSE) - mad cow disease
• scrapie - sheep disease
• chronic wasting disease of elk, deer, moose
• feline spongiform encephalopathy
• variant creutzfel-jakob disease (CJD) - mad cow disease in people

by ingestion

long...years