Midterm 2 Infectious and Non-infecteous Disease Flashcards
How much of the dog population should be vaccinated for rabies to create sufficient herd immunity
70%
Why is Diclofenac –a non-steroidal anti-inflammatory– problematic to use?
The drug is toxic to vultures
How does vulture decline affect humans?
- The corpses become available to the the feral dog population, allowing the population to grow and increasing the amount of dog induced human rabies cases
- Corpses are inefficiently scavenged and they provide excellent breeding grounds for bacterial pathogens
What are common ways that vulture populations are reduced?
Poisoning
-poachers lace animal carcasses (elephants and rhinos) with poison to
intentionally kill vultures that might tip off park rangers
Herders poison felled livestock (killed by predators) to kill the predator
What is the most deadly zoonotic disease?
Rabies
What is the R0 of rabies in humans?
0
-We tend not to bite each other
This is the reason why the emphasis on rabies treatment is on dogs and not humans
What is the R0 of Rabies in dogs?
R0 >1
Structure and shape of rabies virus
RNA virus
-bullet shaped
-enveloped
-species specific variants
hydrophobia
An old term for rabies (specifically in humans)
-refers to a late stage symptom where the infected develops an apparent fear of water
How many human rabies cases occur due to dog bites?
95%
How long does it take for a human to start displaying symptoms of rabies?
3-12 weeks
It takes a long time for the disease to progress up the spinal cord and into the neck
-for this reason you may be vaccinated AFTER the initial infection and develop immunity*
*note that treatment must be administered before clinical signs
How does rabies spread?
Saliva
What was the original rabies vaccine made from?
Ground spinal cord of rabies infected rabbits
-The powder was left to dry to make it less virulent (rabies is very sensitive to hot temperatures and dried conditions)
Parvoviruses
A family of viruses
-Highly contagious (non-enveloped)
-DNA virus
-Type A
-Not spread via vector (must be fomites or environmental infection)
-Diarrheal disease
Type 2 Canine Parvovirus
Not zoonotic
-Very pathogenic
-Wildlife is fairly immune to it (doesn’t usually cause outbreaks)
-Can remain in the environment for up to 7 months
-Common in rescue dogs (if you adopt a “parvo-puppy” of them you aren’t allowed another puppy for a few months)
What makes canine parvovirus so deadly?
It damages the intestinal lining (enterocytes)
-This causes the inflammation and diarrhea
-Bacteria that normally stays in the gut (microbiome) moves into the bloodstream
The electrolyte loss causes problems too
Can Canine Parvovirus get treated?
If it is caught early
Vector
living agents that can transmit disease (mosquito, other animals)
Fomite
A non-living agent that can spread the disease
Valvular Disease
Enlarged heart
Multifactorial
-Genetics
-Diet
-Prior or concurrent health conditions
-Exercise
Many animals are predisposed to this
Has 4 stages (A, B 1 & 2, C, and D)
Stage A of Valvular disease
We may not find it
Stage B of Valvular disease
B1. The heart does not appear enlarged or changed
-You may hear a heart murmur
B2. Heart becomes enlarged
Stage C of Valvular disease
C. Evidence of heart failure is visible and treatment is necessary
-Changes in breathing
-Changes in behaviour
Stage D of valvular disease
Heart failure is getting hard to manage and is not responding to normal treatment
-At this stage euthanasia may be the right call
Dental disease
Multifactorial
-Results in gum disease and tooth loss
-Difficulty eating
-Local and systemic infection
-Weight loss
Dental disease treatments
-Dental cleaning ender GA by or under the supervision of a licensed veterinarian
-Tooth extractions
-No longer treated with antibiotics
-Preventative oral care
“Gentle Dentals”
These are bad
-Done by non-trained people
-Hold dogs down and scrape the teeth
-Harms dogs and gums
-Can cause fractures
Diagnostics for valvular disease
Radiograph
EKG
Echocardiogram (ultrasound)
LISTEN FOR A HEART MURMUR
West Nile virus
- Mosquito borne RNA, enveloped virus that infects and kills birds
- Causes neurological signs and sometimes fever but can be asymptomatic
- Zoonotic but only causes disease in ~20%
- No treatment but effective vaccine
Contagious equine metritis
- Bacterial infection of the uterus (Taylorella equigenitalis)
- Gram (-) bacteria
- Spread by sexual contact (clinical signs appear ~10 days
after breeding) and can be symptomatic or asymptomatic - Causes abortion and uterine inflammation
How to treat and prevent contagious equine metritis
- Active infections in mare cleared up by antibiotics
- Stallions should be cleaned with 4% chlorhexidine prior
to breeding
Equine Protozoal Myeloencephalitis (EPM)
- Caused by Sarcocystis neurona
- Spread by oppossums, cats, skunks and raccoons
- Causes severe neurological signs
- Common in racing and show horses
What are the primary causes of anthelminthic resistance?
Misinformed owners alternate dewormers, deworm too often, maintain unhygienic conditions
What should you always do before deworming an animal
a fecal egg count
TEST THE FECES
How often should you deworm? What should you do to make sure animals don’t get worms?
-deworm according to parasite present
-Don’t just deworm all the time
-maintain clean environment
Which Dewormer is the do worms seem to have the most resistance to
Ivermectin
Treatments for valvular disease
Furosemide (a diuretic)
* Pimobendan (increases cardiac output)
Requires careful monitoring and
commitment by the owner
Side effects can be problematic
Examples of non-human animal Prion diseases
- Scrapie (Sheep and goats)
- Bovine Spongiform Encephalopathy
- Chronic Wasting Disease (cervids)
- Transmissible Mink Encephalopathy
- Feline Spongiform Encephalopathy
- Camel Spongiform Encephalopathy
Examples of human Prion diseases
- Creutzfeldt-Jakob Disease (CJD)
- Variant CJD
- Kuru
- Fatal Familial Insomnia
- Gerstmann-Straussler-Scheinker
- Syndrome
What are traits that are common in all prion diseases
- Spongiform Degeneration
- Transmissible
- Infectious (as in if you put brain matter from one animal into another of the same species, the other animal will get it)
- Accumulation of PrPTSE
- Long Incubation Period
- Extended Preclinical Stage
Cure for Prion disease?
NONE
THE ANIMAL IS JUST GONNA DIE
also you can’t inactivate it easily either
Just how long is Prion disease incubation?
Humans (CJD, vCJD)
Years to decades
Cattle, Deer, Sheep
Years
Rodent Models
Months to a year
Prion Protein (PRP)
A normal host protein expressed on cell surface of neurons, glia, and other peripheral cells
~ 250 Amino Acids with 2 glycans and a GPI anchor
PrP^CWD ( PrP^Sc)
Infectious form of Prion Protein
-Same a.a. sequence as PrPC
-Resistant to degradation
How does Prion Proteins spread through the brain?
Prion replication: Converting PrPC to PrPSc
How do you detect Prion Disease?
Protease Resistance:
-Normal Prions will digest
-Infected Prions will remain
Viewed either though Western Blot Analysis or Obex Staining (CWD)
Will a standard medical sterilization get rid of prion proteins
NOPE
Prions Resist ALL THE THINGS
Chemical inactivation
- Acids
- Base
- Detergent
Extreme conditions (1 N NaOH) will inactivate
Standard Sterilization Methods
- Autoclaving—medical sterilization (120 o C 20 min)
Extreme conditions (autoclaving at 134 C for 1 hour) will inactivate
UV and gamma irradiation levels that inactivate most bacteria and viruses
Scrapie
Prion Disease
-Contagious
-Scrapie infectivity present in fluid and tissue from the placentas of
infected ewes
-Environmentally persistent >15 years
What is the PRNP Gene
Determines a sheep’s susceptibility to Scrapie
ARR resistance to scrapie
VRQ susceptible to scrapie
VRQ/VRQ highly susceptible
ARR/ARR highly resistant
How is Scrapie controlled?
Scrapie is a Reportable Disease
-Suspect cases must be reported to a CFIA veterinarian immediately
Sheep documented with scrapie and all animals exposed to the same birthing environment must be destroyed
-Producers compensated for loss of their animals
Producers that want to minimize the risk of scrapie in their sheep flock can consider selective breeding for genetic resistance
What makes Atypical Scrapie different than scrapie
Harder to identify via protease resistance
Symptoms of Scrapie
Subtle changes in behavior or temperament;
* Intense frequent rubbing against fixed objects to relieve itching; * Gait abnormalities such as incoordination, stumbling, high
stepping of forelegs, hopping like a rabbit and swaying of the
back end;
* Weight loss despite displaying a “normal” appetite;
* Weakness such as difficulty getting up or falling down;
* Biting at feet and legs;
* Lip smacking; or
* Normal behavior at rest, but if stimulated with sudden noises or excessive movement, the animal may tremble or fall down.
What is the cost of BSE to the Canadian cattle industry
7 billion dollars
Bovine Spongiform Encephalopathy
Mad Cow disease
- Prion disease
-zoonotic (causes vCJD)
Classical BSE
Prion Disaese
Classical BSE caused by feeding
cattle contaminated feed
- Rendering
Average age of infected cattle: 4-5
years
Atypical BSE
Prion Disease
-Very old cattle
- 10 years +
- Appears to be sporadic (randomly
occurs)
- Distinguished from classical BSE by
characteristics of the abnormal prion
protein
- NOT linked to animal feed (Meat and
bone meal)!
Chronic Wasting Disease
*Contagious Prion disease
*Central nervous system & lymphatic
*Always fatal/ No treatment/No cure
*Complicated Detection
* Post mortem — No useful live tests
*CWD Strains
Limited to cervids (so far)
- May or may not be zoonotic
How do you control CWD?
No drugs/vaccines/cures
Depopulation?
- Perhaps but attempts have not been completely successful
Reduce population?
-Environmental component makes it so that the disease lingers for years
What animals are susceptible to Chronic Wasting Disease
Cervids
- White-tailed deer
- Mule deer
- elk
- Moose (not common in North America)
Eastern Equine Encephalomyelitis
- Uncommon but 90% fatality rate
- Causes brain inflammation
- Confirmed by IgM antibodies to the virus
- Severe neurological signs
- Mosquito born enveloped RNA virus
- Can be zoonotic
