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Infectious Disease. Dr. N. Matthew Ellinwood, D.V.M., Ph.D. Presented by: Schontonia Davis March 3, 2014. Iowa State University College of Agriculture and Life Sciences. Overview. Common or preventable infectious diseases Classifications of organisms Susceptible animals and clinical signs

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Infectious disease

Infectious Disease

Dr. N. Matthew Ellinwood, D.V.M., Ph.D.

Presented by: Schontonia Davis

March 3, 2014

Iowa State University

College of Agriculture and Life Sciences


  • Common or preventable infectious diseases

  • Classifications of organisms

  • Susceptible animals and clinical signs

  • Methods of control or prevention

  • Zoonotic potential


  • Viral

  • Bacterial

  • Protozoal

  • Fungal

  • Parasitic

Viral diseases
Viral Diseases

  • Viruses

    • Incapable of replication outside of host

    • Relatively small genomes

    • Use host cell proteins and structures to replicate

    • RNA versus DNA based viruses

    • Many viral diseases can be successfully prevented with vaccination

    • Some viruses are resistant to successful vaccine based prevention

    • Cannot be treated with antibiotics

    • Newer and virus specific antiviral drugs available for some types


  • Positive sense RNA viruses

  • Club like proteins on membrane give a crown like appearance (corona = crown in Latin)

  • Causes intestinal disease

  • In dogs and cats, fecal oral route

  • Stable in environment

  • Decontamination 10% bleach

Coronavirus in dogs
Coronavirus in Dogs

  • Canine coronavirus

    • >90% of dogs exposed

    • Disease is mild and self-limiting (adults) to fatal (rarely in young pups)

      • Anorexia, vomiting, diarrhea

    • Vaccine (killed virus) exists

      • Will not prevent disease, though may limit clinical signs

      • Antigenic drift in virus makes effective vaccine design difficult

    • Treatment: supportive care of intravenous fluids and electrolytes

Coronavirus in cats
Coronavirus in Cats

  • Feline coronavirus

    • >80% of cats exposed

    • Disease is mild and self-limiting in most cases

    • Rarely cats develop a fatal sequelae

      • Feline infectious peritonitis

        • “Wet form” with abdominal and thoracic fluid accumulation

        • “Dry form”

      • Uniformly fatal and untreatable

      • Associated with stressful and overcrowded conditions

    • Vaccine (killed virus) exists

      • Use of vaccine is very controversial

Herpes virus in dogs and cats
Herpes Virus in Dogs and Cats

  • Herpes virus

    • Linear double stranded DNA genome

    • Remain latent after primary infection

      • Shingles (chicken pox)

      • Cold sores

  • Canine herpes virus

    • Under studied

    • Not recognized as a clinically important disease

    • Exception is bitches with primary periparturient infections

    • Entire litter may be lost due to no preexisting immunity in the dam and viral preference to replicate at below normal temperature

Feline herpes virus
Feline Herpes Virus

  • Cause of upper respirator/ocular disease

  • Feline viral rhinotracheitis (FVR)

  • Can lead to damage of the upper respiratory tract, and chronic upper respiratory disease

  • Vaccination is routine (modified live or killed)

  • Once infected, usually becomes a carrier for life that sheds the virus and infects others

Parvo virus
Parvo Virus

  • Parvo (Latin for small)

  • Single stranded negative sense (usually) DNA genome (~5000 base pairs)

  • Virus codes for very few genes, and requires cell machinery for replication

  • Replicates in dividing cells of host

Canine parvovirus
Canine Parvovirus

  • Species jump, appeared ~1979, and spread world wide

  • Causes intestinal disease (rapidly dividing cells of GI tract

  • May also attach to immune cells (rapidly dividing)

  • Adults, self limiting diarrhea disease

  • Can be fatal in pups ~16 weeks of age or less

    • Anorexia, vomiting, bloody diarrhea, dehydration

  • Treatment: supportive care

  • Easily prevented by good hygiene and vaccination (MLV)

  • Long lasting maternal immunity may interfere with vaccination

    • Last booster ~16 weeks of age

Feline parvovirus
Feline Parvovirus

  • Feline Panleukopenia (Distemper)

  • Causes intestinal disease and immune cell depletion

  • Adults, self limiting diarrhea disease

  • Can be fatal in kittens

  • Easily prevented by good hygiene and vaccination (MLV)

  • Long lasting maternal immunity may interfere with vaccination

    • Last booster ~12 weeks of age


  • Cause of two canine conditions

    • Infectious Canine Hepatitis (CAV-1)

    • Infectious Tracheobronchitis (CAV-2)

      • Other causes of ITB possible

  • ICH now rarely seen due to vaccine usage

  • Oro-nasal transmission

  • Prevention obtained by vaccination with CAV-2

  • CAV-2 provokes cross reacting antibodies


  • ssRNA (-)

  • Canine Distemper virus

  • Airborne exposure from infected animal

  • Epitheliotropic

    • Respiratory and GI tract

  • Severe disease can involve CNS (often fatal)

  • Very rare now

  • Vaccine effective

Feline calicivirus
Feline Calicivirus

  • Cause of respiratory and GI disease

  • Vaccine available

  • Will not prevent infection but may limit disease

  • New form that is highly lethal has been seen

    • First appeared 1998 in California

    • Hemorrhagic GI disease

Parainfluenza virus
Parainfluenza Virus

  • Canine Parainfluenza-3

  • Cause of infectious tracheobronchitis

  • Oro-nasal route

  • Effectively controlled by vaccination (MLV or Killed)

Feline retrovirus
Feline Retrovirus

  • Feline Immunodeficiency Virus (FIV)

    • Lentivirus

    • Kitty AIDS (this virus cannot infect humans)

    • Causes depletion of T cells

    • Spread by cat bites

  • Vaccination available

    • Highly controversial

    • Killed Adjuvanted

    • Not 100% effective

    • Makes later diagnosis difficult

Feline retrovirus1
Feline Retrovirus

  • Feline Leukemia Virus (FeLV)

    • #1 viral killer of cats

    • Oncovirus

    • Cause of infectious feline leukemia

    • Spread by cat bites, shared dishes/litter pans

  • Vaccination available

    • Killed Adjuvanted

    • Not 100% effective

    • Recommended for at risk cats

Rabies virus
Rabies Virus

  • Rhabdovirus

  • RNA genome

  • 100% lethality, no treatment

  • Neurotropic

  • Zoonotic

  • Vaccine

    • Killed virus, adjuvanted, required by law

Misc organisms
Misc Organisms

  • Bacterial

    • Bordetella bronchiseptica

      • Kennel cough, ITB

      • Vaccine only effective for 6 months

    • Leptospira

      • Cause of leptospirosis

        • Vasculitis, uveitis, kidney and liver damage

      • Zoonosis

      • Spread in urine of infected animals (rodents/wildlife)

      • Vaccinate hunting dogs/ratters

      • Many serovars

      • Vaccine is a bacterin (adjuvant)

Misc organisms1
Misc Organisms

  • Chlamydia

    • Cause of URI / IRT

    • Killed vaccine for at risk cats (catteries)

  • Clostridial disease

    • Clostridium perfringens

    • Diarrhea in dogs and cats

  • Cat scratch disease

    • Bartonella henselae

    • Up to 60% of cats may be seropositive


  • Passive/innate: immunity developed when the offspring absorbs antibodies found in colostrum

    • Must be consumed before gut closure.

  • Acquired: immunity developed from exposure to a viral/bacterial pathogen

    • How can an animal be exposed to these pathogens?



  • Edward Jenner first used vaccination in 1796 for treatment of smallpox

    • He found that the cow pox virus protected against smallpox

  • Before 1000 CE this process was used in India

    • Humans were inoculated with small pox and only received 1/10 of the disease

      • Variolization

  • 1885- Pasteur developed a vaccine for rabies

    • Prevented the disease after exposure

Types of vaccines
Types of Vaccines

  • Attenuated virus or modified live

    • Produces an active infection

    • Virus is grown by passing it through something other than the normal host for ~30 generations

      • Duck or chicken eggs

    • Virus can grow but modifies itself to be successful in the eggs

    • Usually will not allow disease to occur after vaccination but elicits an immune response

Type of vaccines
Type of Vaccines

  • Recombinant vaccines

    • “Recombinant vaccines are created by utilizing bacteria or yeast to produce large quantities of a single viral or bacterial protein. This protein is then purified and injected into the patient, and the patient's immune system makes antibodies to the disease agent's protein, protecting the patient from natural disease.”

    • Little chance of the host getting sick from the vaccination

      • Only the protein is injected, not the whole organism

  • Recombinant vectors

    • Replication incompetent viral vectors “expressing” disease agent proteins: e.g. canary pox vectors

Types of vaccines1

Types of Vaccines

  • Killed Virus

    • Very dangerous pathogens

      • Why wouldn’t we want to use attenuated vaccines for dangerous pathogens?

    • May not illicit immune response

    • There can be reversions or mutations that occur that make the pathogen virulent again.

      • Polio

Zoonosis resource
Zoonosis Resource


  • Know:

    • Dogs

    • Cats

    • Birds

    • Pocket Pets

Host susceptibility resources
Host Susceptibility Resources


Biosafety levels and research with infectious agents
Biosafety Levels and Research with Infectious Agents

  • Refers to a laboratory’s rating (BSL rating)

  • Is a designation regarding certain kinds of agents based on how dangerous they are

    • BSL 1 agents – not know to cause disease in healthy humans

    • BSL 2 agents – agents of moderate risk to people/environment (salmonella)

      • Generally transmissible by crossing mucous membranes/injection

    • BSL 3 agents – agent is potentially lethal by inhalation (tuberculosis)

    • BSL 4 agents – Fatal by inhalation (hemorrhagic fevers)