Equine BacterialDiseases

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

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

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/

Mare Sampling

CEM

CEMStallion 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

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

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