Download 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