equine bacterial diseases inag 120 – equine health management september 14, 2011
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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
Control = isolation, disinfectant Live in soil and
manure
© Merck Veterinary Manual
© 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 systemand lymph tissue w/in 1-2 days
Nasal discharge follows
10-14 days untilabscesses rupture
© Merck Veterinary Manual
1. Bastard strangles
2. Guttural pouch empyema
3. Purpura hemorrhagica
4. Myocarditis
5. Inhalation pneumonia
6. Laryngeal hemiplegia
7. Septic arthritis
Strangles – other problems
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 hoursif 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
consideredresistant
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, anti-
inflammatories) 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
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 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
2008All 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
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