Equine Viral Diseases
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Transcript Equine Viral Diseases
Equine
Bacterial
Diseases
INAG 120 – Equine Health Management
September 14, 2011
What is a bacterium?
Bacteria = single-celled organism, no
nucleus, single strand of DNA
REPRODUCTION
Contain all necessary parts for self-reproduction
Normally reside in the animal!
What is a bacterium?
BACTERIUM
Structure
Rigid cell wall + cell
membrane
Cytoplasm within
1 chromosome + plasmids
Ribosomes
Flagella (for movement)
Routes of bacterial
infection…
1. Physical breakdown of skin (cuts/bites)
Aerobes
E. coli
Pseudomonas
Staphylococcus
Streptococcus
Aneaerobes –
Clostridium septicum
C. tetani
Routes of bacterial
infection…
2. Access to sensitive tissue
Respiratory
Venereal
“Picked up”
Anthrax (soil)
Brucellosis (water)
Rain scald (skin)
Routes of bacterial
infection…
3. Infection of normal flora
E. coli raging out of control
Salmonella
Examples:
Dental problems
Abscesses
Etc…
Bacterial Diseases
Salmonella
Strangles
Potomac Horse Fever
Clostridia
Botulism
Tetanus
Rhodococcus Equi
Anthrax
Lyme Disease
Contagious Equine
Metritis
Bacterial Diseases
Salmonellosis
Mostly S. typhimurium
2200 serotypes
Infectious diarrhea in adults
Most commonly diagnosed infectious cause!
Clinical Signs:
Diarrhea, abscesses, septicemia and other
ailments
Subclinical carrier Acute
Stress plays important role
Salmonellosis
Diagnosis
Treatment =
antibiotics,
rehydration
Very resistant
© Merck Veterinary Manual
Control = isolation,
disinfectant
Live in soil and
manure
© Merck Veterinary Manual
Strangles
Streptococcus equi
A.k.a. distemper
Upper respiratory
infection/abscessed lymph
nodes
Purulent discharge
Can get from contaminated
feed, water equipment
Affected animals infective ≥
4 wks after onset
Can be a chronic carrier
state if gutteral pouches
involved
© Thorn Biosciences
Strangles
Clinical Signs
3-6 day incubation
Inappetance
Fever up to 106º
Inflammation of
respiratory system
and lymph tissue
w/in 1-2 days
Nasal discharge
follows
10-14 days until
abscesses rupture
© Merck Veterinary Manual
Strangles – other
problems
1. Bastard strangles
2. Guttural pouch empyema
3. Purpura hemorrhagica
4. Myocarditis
5. Inhalation pneumonia
6. Laryngeal hemiplegia
7. Septic arthritis
Strangles
Morbidity vs. mortality
Diagnosis
Clinical signs often easy to recognize
Nasal or abscess swab
Diagnostic Test in UK
Treatment
Rest and nursing care
Hot packs over abscesses incision and drained
Antimicrobials if sensitivity test indicates
Prevention
Strangles Control Plan
Isolate all incoming horses, 2 weeks
Quarantine affected horses
Take temperature daily of all in-contact,
for 2-3 weeks, separate if elevated
Nasal-pharyngeal swab affected horses 3
times, 4-7 day interval
Treat only severely affected
Potomac Horse Fever
Caused by erlichial bacterium,
Neorickettsia risticii
Linked to parasites of fresh water snails
First reported along Potomac R. in Maryland
and Virginia, and Susquehanna R. in
Pennsylvania
Has now been reported in both Canada and
Europe
Occurs between late spring and early fall
Potomac Horse Fever
Disease Transmission
Detected N. risticii in trematode stages found in snail secretions
and in aquatic insects
Horses feet in water w/ PHF-snails tranmission of PHF did not
occur.
Horses drink water with PHF-snails transmission of PHF did
not occur.
Horses fed PHF-snails
transmission of PHF DID occur
PHF infection caused by accidental
ingestion of insects such as
caddisflies or mayflies containing
infected larvae.
Potomac Horse Fever…
Symptoms
Lethargy
Anorexia
Fever
Colitis
Mild colic severe diarrhea
Laminitis
Abortion
up to 80% of confirmed
PHF cases eventually die
Potomac Horse Fever…
Treatment: treat the symptoms
Antibiotics of choice:
Oxytetracycline**
(6.6 mg/kg once a day for 5
days ) – improvement in
symptoms within 12 hours
if treated early
Demeclocycline
Doxycycline
Minocycline
Prevention:
Vaccination – effective???
Two-dose primary series 3-4 weeks apart
Re-vaccinate 4-6 months as control is short-lived!
Vaccine contains only one strain
Clostridia - C. botulinum
Spore-forming bacteria (anaerobic)
Spore produces potent neurotoxin
7 different neurotoxins
Routes of Infection:
Ingestion of toxin (type C – found in animal carcass
contamination of feed)
Ingestion of bacteria internal production of toxins
(type B – inadvertently picked up in soil)
Shaker Foal Disease
Wound contamination (least common)
C. Botulinum – Shaker Foal
Affects young foals
Generally those born to dams recently
moved to an endemic area
or that weren’t vaccinated
during pregnancy
Muscle trembling is
predominant clinical sign
Clostridia - C. botulinum
Clinical signs:
Toxin blocks communication between
nerves and muscles (“flaccid paralysis”)!
Neurological symptoms
Inability to swallow
Drooling
Lying down/inability to stand
Colic symptoms
Inability to breathe
Only motor neurons affected
Clostridia - C. botulinum
Treatment and prevention
Hyperimmune plasma or UPenn anti-toxin
Contains high amounts of anti-toxin
Irreversible bond between toxin and nerve cell but cell can
repair itself (7-10 days)
Supportive care
IV fluids, frequent rolling or sling, urinary catheter, eye
ointment
Vaccination
Proper hay curing
Clostridia - C. Tetanus
Spore-forming bacteria
Produces toxins that block neurotransmission
Breeds in low oxygen wounds,
punctures
3-21 day incubation (avg = 8 days)
Clinical Signs:
Unopposed muscle contraction and spasm (tetany)
Lockjaw
Stiffness
Third eyelid protrusion
Death
Clostridia - C. Tetanus
Treatment
Clean wound with hydrogen peroxide (except in
puncture!)
Tetanus antitoxin
Muscle relaxants
Prevention
Vaccinations
Clean safe environment
Bacteria are present in feces and intestinal tracts of horses
and humans.
Common for soil contaminated with feces to have C. tetani
spores
Rhodococcus Equi
Leading cause of foal pneumonia
Predominantly a disease of newborn foals
2-6 mos old
> 6 mos
considered
resistant
Diarrhea
Respiratory
signs
© Merck Veterinary Manual
Rhodococcus Equi
Lives in soil – growth is enhanced by constituents of
equine manure
Amount and type of R. equi in soil foal pneumonia cases!
Higher density of mares and foals increased cases
Grows best in heat – can multiply by thousands in the
summer!
Resists sunlight and most disinfectants
Inhalation of contaminated dust
Treatment and Control:
Prophylactic azithromycin?
Antimicrobial therapy for 4-10 weeks
Removal of manure from foal areas
Rotational grazing, reduce dusty conditions, low stocking rates
Anthrax
Transmitted by direct contact
or, on rare occasion, by the air
(biting flies?)
Acute disease in cattle
Disease onset within 96 hours in
horses
RAPID ONSET:
High fever, severe colic, swelling
on underside of neck and chest,
difficulty breathing, rapidly
followed by death
Zoonotic Disease!
Anthrax
Diagnosis via blood
sample
Treatment:
Penicillin if started early
Supportive care (iv fluids, antibiotics, antiinflammatories)
Control: quarantine area, destruction of
carcasses (burning), vaccination during
outbreak
“Cursed Fields” – spores can remain infective in soil
for years
Lyme Disease
Spirochete bacteria – Borrelia burgdorferi
Transmitted by blood of infected tick
Non-vector transmission by contact with
infected urine or across placenta
Arthritis/stiffness, lameness,
hot/painful/swollen joints, fever
Treatment: high dose of antibiotics
Control: control ticks
Lyme Disease
Contagious Equine
Metritis
Acute, highly contagious
venereal disease
Clinical signs
Vaginal discharge
10-14 days after infection
Remains infected for
several months
Failure to conceive
Treatment/Control:
Thoroughly clean stallion
© University of Sydney
Importing a horse?
Horse has been in region for at least 60 days. OR
horse must be accompanied by a health certificate
issued by a full-time salaried veterinary officer of the
National Government
The horse has been inspected and found free of
contagious diseases
The horse has not been vaccinated for 14 days
immediately preceding exportation
The horse has come from a clean premises (60 days
immediately preceding exportation)
The horse has been inspected and found to be free
from external parasites
Before Export…
Mares and stallions over the age of 2 years MUST go
through CEM testing
If any specimen collected is found to be positive for
CEM, the stallion or mare must be treated for CEM in a
manner approved by the National Veterinary Service of
the region of export.
At least 21 days must pass before the horse will be
eligible to be tested again.
The horse must not have been bred naturally or by
artificial insemination from the period of time after
specimen collection of the date of export
Once in the US: http://www.rigbiefarm.com/quarantine/
CEM
Mare
Sampling
CEM
Stallion
Sampling
CEM Outbreak in KY
2008/2009
December 10, 2008: CEM reported in
Quarter Horse Stallion through routine
testing
Part of the process for shipping frozen
semen to Europe
Stallion moved from TX to KY in February
2008
All exposed horses put under quarantine
CEM Outbreak…
During 2008, original stallion was bred to 44
mares both on the farm and via shipped semen
Of the 22 stallions at the farm, 13 had been
moved to other states
December 23, 2008: FOUR total stallions
positive for CEM
Expands exposed mare population to over 150
20 states involved!
All must be quarantined and tested
CEM Outbreak…
By March, 2009:
686 horses exposed to T. equigenitalis
Located in 46 states
121 exposed or positive stallions in 19 states
565 exposed or positive mares in 44 states
March 30, 2009: 16 stallions including all
4 KY stallions released from quarantine
CEM Outbreak…
By May 2009:
More than 820 exposed or positive horses in
the US
Positive horses included 18 stallions and 5
mares
Located in 47 states
121 exposed/positive stallions – 27 states
649 exposed/positive mares – 45 states
CEM Outbreak…
By June 2009:
21 stallions positive for CEM organism
One in Georgia, three in Illinois, three in Indiana,
one in Iowa, four in Kentucky, one in Texas, and
eight in Wisconsin
Thoroughbred, Appaloosa, Quarter Horse, Paint,
Dutch Warmblood, Fjord, Friesian, Hackney and
Saddlebred
939 total exposed or positive horses
Found in all states except Hawaii and Rhode
Island
CEM Outbreak…
May 2010
Arabian stallion in CA
Imported from a country not known for CEM
23 horses exposed; 22 later tested negative
July 2011
Arabian stallion in AZ
At least 25 horses exposed; currently
undergoing testing