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110 Cards in this Set

  • Front
  • Back
What is a common parasitic cause of otitis externa, especially in cats?
Otodectes cynotis
Is cytological examination of ear discharge a useful diagnostic test in otitis externa?
When are culture and antimicrobial susceptibility essential diagnostic tests for otitis externa?
1. When rod shaped bacteria are found on cytology

2. With cases of recurrent otitis that have shown a poor response to therapy

3. If otitis media is suspected
A dog is presented for ear scratching. A swab of the ear canal is taken and Gram stained. Gram + bacteria are present. Is this bacteria the cause of the ear infection?
Maybe - Streptococcus bacteria can be found in a normal ear and also be a pathogen in otitis externa
What are 2 most common microbes isolated from a healthy dog’s normal ear canal?
1. Malassezia otitis (yeast)

2. Staphylococcus intermedius (pseudintermedius)
What is otitis externa?
* Acute or chronic inflammation of the epithelium of the external ear canal

* Pinna may be involved

* Multifactoral problem
What are some predisposing factors for otitis externa?
1. Anatomic: conformational predispositions of certain breeds

2. Environment: swimming, foreign material

3. Medications: chronic antibiotic and glucocorticoid therapy for yeast infections

4. Hypersensitivity diseases
What are some good diagnostic tests for otitis externa?
1. Otoscopic exam
2. Ear swab (cytology, culture and sensitivity)

**** Those are the most practical if problem persists you can do the following

3. CBC and Chem
4. X-ray
5. CT
6. Biopsy
What gram + bacteria are most common in healthy dog ears?
****Staphylococcus (9-20%)
* Streptococcus (16%)

*** If abnormally high population could be causing otitis externa
3 most common gram - bacteria found in dogs with otits externa?
* Pseudomonas sp. (20%)
* Proteus sp. (11%)
* E. coli (14%)
What funji is found commonly in both dog and cat ears?
* Malassezia sp. (yeast)

** A few yeast is normal but if you see an abundance on cytology it could be the cause of otitis externa
What metazoana is commonly the cause of otitis externa in cats?
Otodectes cynotis

* Can cause problems in dogs but rare
What should always be used when taking a sample for an ear culture?
Individual sterilized otoscope cones
Which microbe of otits externa can be spread from animal to animal?
* Otodectes cynotis (cats, dogs, ferrets)
3 microbes that commonly cause otitis media in large animals?
1. Mannheimia haemolytica
2. Pasteurella multocida
3. Histophilus somni
3 common foot infections in sheep?
1. Ovine interdigital dermatitis

2. Ovine footrot (contagious footrot of sheep)

3. Strawberry footrot
Cause of Ovine interdigital dermatitis
Fusobacterium necrophorum
Cause of ovine footrot (contagious footrot of sheep)?
**Dichelobacter nodosus** plus Spirochetes and Arcanbacterium pyogenes
Cause of strawberry footrot in sheep?
Dermatophilus congolensis
How quickly does ovine interdigital dermatitis resolve?
Most cases resolve spntaneously in about a week as the immune response overcomes the Fusobacterium necrophrum and its toxin

** Hoof usually not involved
What are the general characteristics (gram stain, O2 requirements, spores) of Fusobacterium necrophrum?
* Gram Neg ROD (pleomorphic filaments)

* Obligate ANAEROBE

* Non-spore forming
What virulence factors does Fusobacterium necrophrum have?
1. Lipopolysaccharide (LPS)- endotoxin

2. Cytotoxin- leukotoxin
What is the natural environment for Fusobacterium necrophrum?
Mucus membranes and GI tract
3 common foot infections in sheep?
1. Ovine interdigital dermatitis

2. Ovine footrot (contagious footrot of sheep)

3. Strawberry footrot
Cause of Ovine interdigital dermatitis
Fusobacterium necrophorum
Cause of ovine footrot (contagious footrot of sheep)?
**Dichelobacter nodosus** plus Spirochetes and Arcanbacterium pyogenes
Cause of strawberry footrot in sheep?
Dermatophilus congolensis
Contagious ovine digital dermatitis is also known as what?
Ovine footrot

* Cause by Dichelobacter nodosus
Gen. characteristics for Dichelobacter nodosus?
* Gram Neg

* Obligate anaerobe

* Non-spore forming
Clinical signs of a sheep with ovine footrot caused by Dichelobacter nodosus?
* Moist, red interdigital area

* Invasion of hoof sole (undermining and separation of hard horn especially from rear)

* Foul smell
Virulence factors of Dichelobacter nodosus?
* Adhesin- Fimbriae (higly immunogenic)

* Extoxin- extracellular proteases

* Lipopolysaccharide (LPS) endotoxin
What is the difference between the virulent and benign strain of Dichelobacter nodosus?
Virulent strains produce potent extracellular proteases
What is the major virulent factor for Dichelobacter nodosus?
Fimbria- it has affinity for interdigital epidermis
What does the exotoxin (extracellular proteases) of Dichelobacter nodosus cause to sheep foot?
* Damage to interdigital epidermis

* Cause separation of horn from underlying lamina
7 major events for a bacterial pathogen to cause damage to host
1. Entry
2. Adherence
3. Avoidence of host defenses
4. Multiplication
5. Spread
6. Evasion of host defenses
7. Damage to cells, tissues, and/or organs
What predisposes a sheep to foot infections?
Predisposing conditions are environmental moisture resulting in maceration of the interdigital skin ans sand or stones that may cause mechanical skin damage
How would a predisposed sheep get a would colonized with Dichelobacter nodosus? Fusobacterium necrophorum?
* Dichelobacter nodosus from subclinically, acutely and chronically infected sheep

* Fusobacterium necrophorum from the environment
How long does it take from infection by Dichelobacter nodosus or Fusobacterium necrophorum to see clincal signs in sheep?
10 to 20 days
What are the gen. characteristics of Dermatophilus congolensis (cause of strawberry footrot)?
* Gram POS rod or filamentous

* Aerobic
Reservoir for Dermatophilus congolensis?
Obligate parasite, so infected animals
Environment for Dermatophilus congolensis?
5 other diseases caused by Dermatophilus congolensis in large animals
1. Dermatiohilosis
2. Greasy heel
3. Rain rot
4. Rain scald
5. Lumpy wool
Characteristic appearnace of Dermatophilus congolensis under the microscope?
gram positive with railroad track appearance
How do you diagnose strawberry footrot caused by Dermatophilus congolensis?
* Clinical signs- when you peal off scabs there should be a red (strawberry) mark

* Culture- interpretation difficult because contamination by opportunistic and environmental bacteria

* Use scabs or crusts for diagnostic testing
How do you prevent foot infections in large animal herds?
* Foot health
* Foot baths
* Segregate
* Avoidance
* Vaccinate
* Minimize skin trauma
* Antibacterial shampoo
*** Dont put treated sheep back on infected pasture
3 common foot infections of cattle
1. Interdigital dermatitis
2. Bovine footrot (bovine interdigital necrobacillosis)
3. Digital dermatitis
Cause of Interdigital dermatitis in cattle
Dichelobacter nodosus
Cause of bovine footrot
* Fusobacterium necrophorum
* Prevotella melaninogenica
* Arcanobacterium pyogenes
Cause of digital dermatitis in cattle
* Fusobacterium necrophorum
* Prevotella melaninogenica
* Spirochetes
other names for digital dermatitis in cattle
* papillomatous digital dermatitis

* hairy heel warts

* strawberry foot
Surface virulance factor for Fusobacterium necrophorum
* Cell wall- Lipopolysaccharide
Secreted virulance factor for Fusobacterium necrophorum
Exotoxin: cytotoxin - leukotoxin
Pathogenesis for Fusobacterium necrophorum causing bovine footrot
1. Disruption of normal skin
2. Colonization of wound
3. Development of anaerobic conditions
What term is used to describe any disease or lesion with which for Fusobacterium necrophorum is associated?
Other common diseases caused by for Fusobacterium necrophorum in cattle
* necrotic layrngitis of calves (calf diphtheria)

* Necrobacillosis

* Necrotic rhinitis
What does for Fusobacterium necrophorum cause in the horse hoof?
Thrush of the hoof

* Localized inflammation, usually hind feet
Treatment of digital dermatitis in cattle
* Debridement of skin flaps and overrun sole horn

* Topical treatments (antibacterial agents)

* Foot trimmings

* Foot baths
Prognosis of digital dermatitis in cattle
Good with proper care and management
Complication associated with digital dermatitis in cattle?
Can progress into distal interphalangeal joint and become septic arthritis
How long can Fusobacterium necrophorum survive in the soil?
* Up to 10 months

* Normal constituent of ruminal flora and in the environment
How long can Dichelobacter nodosus survive in the environment?
* Survive warm, muddy environment for 4-14 days

* obligate pathogen of clinically affected or chronic carrier feet
Corynebacterium pseudotuberculosis is the causative agent for what disease in horses?
Pigeon fever
A Gram stain of a direct smear from a lesion caused by C. pseudotuberculosis would show what?
Gram-positive pleomorphic rod shaped bacteria that is intracellular
Corynebacterium pseudotuberculosis is the causative agent for what disease in goats?
Caseous lymphadenitis
Although the location of abscesses caused by C. pseudotuberculosis in the horse can be found
anywhere on the horse, where is the most likely location?
Why is it called piegon fever?
It gets its name from the abscess lumps that often appear on the pectorals, making the horse look
like it has a pigeon's breast.
How does a horse become infected with Corynebacterium pseudotuberculosis causing piegon fever?
* The bacteria enter through skin abrasions and insect bites

* Can also be spread
through horse to horse contact, horse to cow contact, through the soil, or through a break in the skin.
Geographically where is piegon fever common?
Pigeon fever is more common in dryer climates and is prevalent in California, but in recent years has
been spreading northward.
Is piegon fever fatal in horses?
Rarely is this disease fatal, but recovery can take months and the disease can reoccur.

** There is no vaccine for this disease, so if a horse contracts pigeon fever, the course of action is to
prevent the spread of the infection to other horses.
Clinical signs of piegon fever
* Lameness
* Fever
* Lethargy
* Weight loss
* Very deep abscesses and multiple sores along the chest, midline, and groin area and, sometimes,
the back

* Abscesses also can develop internally.
What is the definitive test to diagnose an infection with C. pseudotuberculosis?
Culture (isolation)
How is serologic testing used to diagnose an infection with C. pseudotuberculosis?
Serological testing is a screening procedure
determining exposure to the bacterium. It does not indicate,
however, whether an animal is currently infected or whether
it will develop clinical signs of the disease.
What neurologic diseases are reportable in horses?
* West Nile
* Equine Herpes Myeloencephalopathy (EHM)
* Rabies
What type of virus causes EEE, WEE, and VEE?
Toga viruses
What is commonly seen as a result to the toga viruses causing EEE, WEE, or VEE?
* Perivascular cuffing with mononuclear and neutrophilic infiltrates

* Gliosis

* brain and spinal cord affected equally
What type of virus causes west nile virus?
What is commonly seen as a result to the flavivirus causing West Nile?
Nonsuppurative encephalomyelitis

* Spinal cord is more commonly affected
What virus causes Equine Herpes Myeloencephalopathy (EHM)?
Equine Herpes Virus 1
What is commonly seen as a result to equine herpes virus 1 causing Equine Herpes Myeloencephalopathy (EHM)?
CNS vasculitis with hemorrhage
What virus causes Rabies?
What is commonly seen as a result to the Rhabdovirus cauing rabies?
Viral inclusions (negri bodies)
5 common respiratory signs in horses
1. Fever
2. Malaise
3. Nasal discharge
4. Cough
5. Dyspnea
6 reportable respiratory diseases in horses
1. Equine Herpes Virus 1&4 (EHV)
2. Equine Viral Arteritis (EVA)
3. Influenza
4. African Horse Sickness
5. Tularemia
6. Glanders
Besides respiratory disease, what other manifestations can EHV 1 cause?
Neurologic disease and abortion
Besides respiratory disease, what other manifestations can equine viral arteritis (EVA) cause?
* Edema
* Conjunctivitis
* Abortion
* Infertility
Clinical signs of hematologic diseases in horses?
* Pallor (anemia)
* Icterus
* Pigmenturia
* Malaise
* Edema
* Petechia/ecchimosis
4 reportable hematologic diseases in horses
1. Piroplasmosis
2. Equine Infectious Anemia (EIA)
3. Surra
4. Dourine
What infectious agent causes equine Piroplasmosis?
* Babesia caballi
* Babesia equi

** Causes hemolysis
What are the 3 populations of horses that piroplasmosis is commonly seen?
* South Texas ranch
* Horses imported before Aug 2005
* Racing horses (esp. quarter horse)
What type of virus causes EIA?
3 clinical syndromes of EIA
1. Acute: fever, thrombocytopenia

2. Chronic: weight loss, periods of acute

3. Inapparent
What is the trend in the number of cases of pigeon fever seen in horses at Texas A&M?
Has gone from no cases 4 years ago to about 45 cases this year.

* Increasing each year!
How do you diagnose Corynebacterium psudotuberculosis (piegon fever)?
* Clinical signs/history

* Ultrasound

* Synergistic Hemolysis Inhibition Test (>512= internal infection)

* Culture
How do you treat Corynebacterium psudotuberculosis (piegon fever)?
* Incision and drainage

* Antimicrobials (internal)
How do you prevent Corynebacterium psudotuberculosis (piegon fever)?
* Dispose of pus
* Manure removal
* Insect control
2 types of fungi
Molds and Yeasts
Molds vs. yeasts
Molds: Multicellular,m filamentous (fuzzy)

Yeast: Single cell, reproduce by budding
When are dimorphic fungi molds? yeast?
Molds: 25'C

Yeasts: 37'C
Transmission of Fusobacterium necrophorum causing ovine interdigital dermatitis
* Usually occurs when there has been heavy rainfall for several weeks and temperature above 50 degrees F.

** Pathogens are transmitted between sheep via soil contact.
Fusobacterium necrophorum zoonotic?
What is the reservoir host for the Equine Encephalomyelitis virus?
EEE, WEE, VEE, and WNV are all transmitted via what type of vectors?
EPM is transmitted how?
the ingestion of infected opossum feces
most common infectious cause of cysitis and pyelonephritis in cattle and swine
Corynebacterium renale
Corynebacterium renale characteristics
Gram + rod, piliated, non-motile
painful or difficulty urinating, straining
more frequent voiding of small amount
Clinical presentation of Cystitis
* Dysuria
* Pollakiuria
* +/- hematuria
* +/- pyuria
* Distended atonic bladder on palpation with firm thick walls
* UA: blood, protein and variable pH
* Usually no generalized signs, no fever
painful urging to urinate, spastic dysuria
Clinical presentation of Pyelonephritis
* Dysuria
* Pollakiuria
* Stranguria
* Tail swishing
* Treading on hindlimbs
* Scalding of the perineum
* Distended atonic bladder with firm thick walls
* Dilation of the ureter and enlargement of the kidney
* Urine reddish-brown in color, cloudy, pyuria, hematuria
* UA: more blood and protein than with cystitis and a variable pH
* Urine specific gravity low
* Presence of bacteria C. renale, E. coli, A. pyogenes
* Generalized signs, fever
* Usually worse than cystitis