Horses 5 Flashcards
Equine MRI what mainly used for for musculoskeletal injuries
- Again cannot get whole body within
- Just distal limbs and hooves
- Laying down in some machines - GA
- Standing MRI -> can move up and down the limb but cannot have movement - sedation as need to be able to stand
- lots of soft tissue, ligaments and joints
Choke what results from, clinical signs and causes
- A blockage of the oesophagus - produce large volumes of saliva
- Profuse nasal discharge with or without food particles usually with no dyspnoea
Causes - Hay/chaff after prolonged fasting – worse if no water
- Via hay net in transportation and no water
- Rapid eating
- Hay after sedation because of reduced oesophageal motility
- Dry sugar beet that has not been soaked ( and it then expands from the saliva)
Respiratory disease clinical examination what are important respiratory characteristics to look at
○ Rate (normal 12 to 20/min) ○ Depth ○ Effort - normal or increased § Inspiratory vs expiratory ○ Abnormal noise § Stertor/stridor § Inspiratory vs expiratory ○ Patient posture § Elbows abducted - sign of pleural pneumonia
What are he 4 important aspects of the upper respiratory tract examination
- Airflow present at each nostril
- Check sub-mandibular LN
○ Often slightly more prominent in young animals
○ Important for strangles - Sinuses
○ Facial symmetry generally good indicator
§ Also fowl breath, unilateral mucopurulent discharge
○ Percussion - dullness - Induce a cough
○ Easily elicited cough from trachea pressure suggests airway inflammation
Thoracic auscultation what is needed, how sensitive, what listening for and what other diagnostic tool needs to be done at this point
- Quite room is essential
- No very sensitive in adults, more sensitive in foals
○ Absence of abnormal sounds does not indicate absence of disease - Bronchovesicular (normal) sounds often difficult to appreciate in normal horses
- Listen carefully for…
○ Region where bronchovesicular sounds are dull or absent especially in horses with tachypnoea
○ Adventitial sounds (crackles, wheezes, friction rubs) indicate pulmonary pathology
Re-breathing examination is next
Re-breathing examination what does it do, what is the goal and what assessing
○ Increases inspired CO2 -> increasing the depth and rate of respiratory
○ Should be able to appreciate (normal) bronchovesicular sounds throughout entire lung-field
○ Accentuates adventitial sounds/wheezes if present
§ Listen for areas of dullness especially ventrally
○ Also access
§ Tolerance to re-breathing examination
§ Coughing - SHOULD NTO COUGH AFTER
§ Recovery - should recovery within 5 to 6 breaths
Ultrasound evaluation of the lung what is it good at evaluating therefore diseases it can see and what is it not good at evaluating
- Excellent for evaluating pleura and superficial lung
○ Pleural effusion
○ Superficial abscess
○ Consolidation
○ Pneumothorax - lack of glide sign - Does not penetrate aerated parenchyma
○ Unable to image deeper lung structures unless consolidated
Radiogrpahic evaluation of lungs in adults and foals what is needed, what is good and not good about it
- Adults
○ Appropriate equipment
○ Lateral views only - usually aren’t mobile
○ Comparatively poor detail especially in ventral region
○ Large amount of views to see whole lung - Foals
○ More like small animals - Parenchymal lesions
○ Contrast to ultrasound - Not as sensitive for pleural disease
What are the 3 main things radiogrpahic evaluation is used for with respiratory disease
○ Evaluate sinuses and guttural pouches
○ Look for presence of fluid lines or soft tissue opacities
○ Dorsoventral view very useful to evaluate the sinuses but can be difficult to obtain
Tracs-tracheal aspirate or wash what are the 5 steps in the technique
- Aseptically prepare site
- Pass stylet trans-cutaneously into trachea - palpate tracheal rings
- Introduce long catheter - cranial to the U bend within trachea
- Deposit small volume of sterile saline at carina via catheter
- Then begin to aspirate back
Trans-tracheal aspirate or wash what is it appropriate for, therefore what disease would you do for, additionally what part of the lung is sampled and what use sample for
- APPROPRIATE FOR CULTURE - most important way to do - WHEN THINK IT IS INFECTIOUS DISEASE
- Pooled sample from entire lung
○ Good for focal lung disease - due to mucociliary clearance moving everything from distal lung up into trachea
SAMPLE USED FOR
1. Cytology
○ Variable neutrophils in normal horses (3 to 50%) - do get false negatives
○ May be bacteria present in normal TTW
§ Interpret in the light of evidence of inflammation
§ Intracellular more convincing of active infection
○ Fungal hyphae common in normal TTW
2. Culture and sensitivity
3. PCR can be useful for some pathogens
Which wash preferred trans-tracheal or trans-enoscopical and why
Don’t do trans-endoscopically for infectious disease as going through upper respiratory tract and therefore sample will be contaminated - instead - TRANS-TRACHEA ASPIRATE
Bronchoalveolar lavage what are the 5 steps in the echnique
- Moderate sedation (xylazine and butorphanol) and twitch
- Pass BAL tube (or endoscope) via nasal passage into trachea
- Wedge in bronchus and inflate cuff
- Infuse and then aspirate sterile fluid (LRS)
○ Variable volumes used (3 x 120ml) - need to infuse at least 250mls - Mix final sample
Bronchoalveolar lavage where in the lung does it sample therefore which disease is it better for and not appropriate for
- Samples a random, relatively small region of the lung
○ BETTER REFLECTS ALVEOLAR INFLAMMATION
○ Appropriate for global lung disease (RAO, IAD) - not focal disease - NOT appropriate for culture (pharyngeal contamination) - NOT FOR INFECTIOUS DISEASE
What are 3 additional tests that can be done on the lung but aren’t common
- Thoracocentesis
- Lung biopsy
- Pulmonary function testing - not common
○ measure pulmonary compliance in the face of histamine - those with equine asthma have an exaggerated response
If suspect a viral respiratory infection what 4 things in diagnostic approach and what 2 things can also add
- Complete blood count
- Thoracic ultrasound
- Serology
- PCR analysis (viral DNA) - nasopharyngeal swab
Can also add -> thoracic radiograph, transtracheal wash
EVH-1 and 4 when infected, how contagious, age of onset and why
- EHV infection is ubiquitous in horses
○ Most horses infected in first year of life
○ 80% seropositive
○ Highly contagious - Clinical disease common and occurs most frequently in weanlings, yearlings and young adults
○ Disease often seen after entry into a training stable
○ Mixing new animals, stress
EVH-1 and 4 clinical signs and what individually associated with
- EHV-1 and 4 clinically indistinguishable
- Incubation period 3-7 days
- Biphasic fever (up to 41 degrees)
- Depression, inappetence
- Serous (to mucopurulent) nasal discharge
- Cough (inconsistent)
- Disease often confined to upper respiratory tract - immunosuppressive
○ May predispose to secondary bacterial pneumonia - EHV-1 is also associated with Abortion storms (later gestation) and neurological disease
- EHV-4 typically causes less severe respiratory disease
○ Very rarely causes abortion or neurological disease
EHV-1 and 4 diagnosis and pathogenesis
Diagnosis confirmed by
- Rising serum titre (or very high initial titre)
- PCR identification or viral DNA or viral isolation
○ Nasopharyngeal swab, buff coat
Pathogenesis
- Infection via respiratory tract
○ Virus attaches and replicates within mucosal epithelium of the URT
○ Lymphocyte- associated viraemia
- Latent infections are common - initiating new outbreaks
○ Lymph nodes
EHV-1 and 4 treatment and control
Treatment
- Symptomatic (anti-inflammatories to control fever)
- Rest from exercise essential
- Antibiotics
○ Typically not indicated
○ Prolonged (>7 days) or persistent severe clinical signs
Control
- Isolation of affected horses
- Immunity following natural infection not strong
- Vaccine immunity poor (required q3-6monthly booster)
Equine influenza what ages susceptible and typical clinical signs
- All ages susceptible
○ Young (1-3 years) adults commonly affected
○ Weanlings are also particularly susceptible when stressed
○ All age likely affected in naïve population
Clinical signs
○ Sudden onset, short (48 hour) incubation (spreads rapidly)
○ Biphasic fever (up to 41 degrees)
○ Cough: easily elicited by tracheal palpation
○ Serous nasal discharge
○ Pharyngitis, tracheitis, myalgia (muscle pain) - Disease usually restricted to the URT
Equine influenza diagnosis and treatment
Diagnosis
- History of multiple affected horses, rapid spread
- Clinical signs (coughing)
- Rising serum antibody titre
- Viral isolation or PCR detection confirms diagnosis
Treatment
- REST
○ Horses recovering from EI might be unfit for competition for 50 to 100 days
○ Mucociliary clearance might be impaired for over 30 days
- Antibiotics
- Reportable
Hendra virus what need to do if suspect a case and diagnosis
What to do if you suspect a case
- Contact appropriate state department or emergency animal disease hotline
- Personal protective equipment (PPE)
○ Overalls, protective boots, safety eyewear, gloves and respirator or mask
Diagnosis
- PCR and virus isolation of blood, nasal swabs, and tissue
- Samples to submit
○ Nasal swab (preferable in virus transport media)
○ 10ml blood in plain tube
○ 10ml blood in EDTA
Hendra virus outbreak recommendations
- Quarantine affected horses
- Avoid returning to exercise too early
○ Secondary bacterial infection
○ Rest sick horses “one week for every day of fever” - Consider vaccination in future
○ Reduce severity of clinical signs
○ Reduce viral shedding
What are the 5 differentials for Bilateral nasal discharge, lymphadenopathy and fever and which want to rule out first
- Strangles - WANT TO RULE OUT FIRST AS VERY CONTAGIOUS
- Pneumonia
- Sinusitis
- Viral infection
- Pharyngeal/retropharyngeal/pulmonary abscess
Streptococcus equi ssp equi (strangles) type of bacteria, age, how contagious and transmission
- Gram (+) cocci - ALWAYS A PATHOGEN - should not be present
- Mostly affects horses ages 1-3 years
○ However any age can be affected - VERY CONTAGIOUS
○ Spread by inhalation or ingestion - Fomites are very important in epidemiology
○ Buckets, water troughs, humans (veterinarians)
○ Does not persistent in the environment - Some horses will become persistent shedders
○ Reservoir in guttural pouches
○ Asymptomatic
Strangles what are the main clinical signs and diagnosis
Clinical signs
- Lymphadenopathy
○ Submandibular and/or retropharyngeal (harder to see swelling- need to scope and go into the guttural pouch as present on the floor - will be puss present if infected - if don’t treat can get chondroids (puss balls - need to remove))
- Nasal discharge
- Fever
- +/- depression, inappetence - variable but does indicate severity and shape treatment
Diagnosis
- Complete blood count
- FNA of submandibular lymph nodes or sample discharge if ruptured - PCR, culture and cytology
- Endoscope - to look a guttural pouches and ensure don’t have retropharyngeal lymphadenopathy
- Nasopharyngeal swab or lavage - PCR or culture
Strangles treatment for mild fever, anorexia and no respiratory distress - IMPORTANT
○ Drain abscesses (hot packing - will rupture (once rupture very contagious particles released), lancing)
○ Cautious NSAID use -> in general with horses and gastric ulceration, possible dehydration for renal issues as well
○ Antibiotic therapy probably contra-indicated in mild cases and typically of little value once abscessation has occurred
§ Would use penicillin which is inactivated with puss
Strangles treatment for severe respiratory distress with systemic signs of disease - IMPORTANT
○ Often indicates retropharyngeal lymphadenopathy
§ +/- guttural pouch empyema
○ Antibiotics usually required
§ Penicillin is drug of choice
○ Tracheostomy might be required - if very extreme lymphadenopathy
○ Drain abscesses and treat guttural pouch empyema if present
§ Lavage, surgical drainage
○ Feeding tube, oesophagostomy etc might be required if severe, longstanding dysphagia present
Control and prevention of strangles what are the 4 important steps within
1) Strict quarantine
○ Feed/groom horse last
○ Muck out stall last and care with bedding
○ Separate clothing and boots
○ Gloves and wash hand
2) Confirm negative before mixing with other horses
○ PCR/culture of GP washes or nasopharyngeal swabs - 3 x negative then confident
3) Environmental
○ Isolate infected horses until negative
○ Human important fomites -> excellent personal hygiene
○ Care with shared feeding and cleaning equipment, track
○ Identify carriers -> culture/PCR of GP lavage samples
4) Vaccination: 75% are immune after infection
○ Intramuscular -> not very effective but might reduce severity of disease
○ Intranasal (MLV) more efficacious but not available in Australia
List the 4 main complications of strangles
1) metastatic S. equi
2) bastard strangeles
3) pupura haemorrhagica
4) streptococcal myositis
Metastatic S. equi what is it and what does it lead to
Complication of strangles
○ Bastard strangles - approx. 10% of cases
○ Abscesses in the abdomen, brain, liver, spleen, kidneys
○ Guttural pouch empyema - chondroids
Basatrd strangles what is it, diagnosis and treatment
Complication of strangles ○ Diagnosis § Increase strep M protein titre (antibodies detected against SeM) § Inflammatory blood work § History § Ultrasound, abdomenocentesis, CSF tap ○ Treatment § Long term antibiotics (1-6months)
Purpura haemorrhagica what is it, what does it result from and result in and treatment
Complication of strangles
Type III hypersensitivity reaction
○ Immune complex deposition -> vasculitis
§ Severe distal limb oedema -> skin sloughing
§ Petechiation or ecchymosis
§ Glomerulonephritis reported
○ Has been associated with vaccination
○ Treatment - corticosteroids and penicillin
Streptococcal myositis what is it, how common and the 3 main mechanisms
Complication of strangles ○ Rare ○ Various mechanisms § Infarcts § Immune mediated § Bacterial invasion of muscle
