Ovine Pneumonia Flashcards
What are the common causes of pneumonia in sheep?
Mycoplasma ovipneumoniae
Mannheimia haemolytica
Secondary - Fusobacterium necrophorum, Trueperella pyogenes
Jaagsiekte/OPA
Maedi visna
Caseous lymphadenitis - Corynebacterium pseudotuberculosis
What kind of disease is caused by Mycoplasma?
Atypical/chronic/chronic- nonprogressive pneumonia
Describe the pathogenesis of mycoplasma
4-7 month old lambs Commensal See multiple strains in one infection Invades the bronchi, damages cells and reduces mucous clearance Allows for secondary bacterial infection
What are the clinical signs of mycoplasma?
Mild
Decreased growth rate
*similar to calf cuffing pneumonia
How is mycoplasma treated?
Generally self limiting, only treat if severe
Any Ab except aminoglyoside
Slow to occur so is slow to resolve
Prevention - reduce stocking densities, avoid multiple sterssors at once, control other disease
What kind of pneumonia is caused by F. necrophorum and T. pyogenes?
Chronic suppurative pneumonia
Describe the pathogenesis of a chronic suppurative pneumonia
Secondary to M. haemolytica infection
Inhalation of bacteria
Bacteria are spread from a septic focus
What are the clinical signs of chronic suppurative pneumonia?
Weight loss/reduced weight gain Depression Tachypnoea Cough Normal temp/intermittent pyrexia (walling off of abscess, intermittent release of bacteria)
How is chronic suppurative pneumonia diagnosed?
Difficult to diagnose
Auscultation - area of focally collapsed lung, no wheezes/crackles
Percussion - dullness, pain
US - pleural abscess
How is chronic suppurative pneumonia treated?
Difficult
Ab won’t penetrate into abscesses but will improve immune response and help wall off infection
Micotil/macrolide
Prevention - vaccination, healthy sheep
Describe the pathogenesis of Jaagsiekte
Contagious lung tumour caused by a retrovirus
3-4 year incubation period
Lambs will often have disease if the dam did
Get secondary infection with M. haemolytica which will kill the sheep
What are the clinical signs of Jaagsiekte?
Weight loss despite good appetite
Exercise intolerance
Lung crackles
Tachypnoea
How is Jaasikete diagnosed?
Wheel barrow test - -ve does not = -ve. Repeat test until get a +ve
No detectable immune response
BAL - PCR
US - sharp demarcation, +ve = +ve but -ve does not = -ve
PM - definitive dx
How is Jaagsiekte treated?
No tx, cull
Control - tricky, don’t buy in sheep, regularly inspect flock for signs, avoid trough feeding to reduce transmission
Describe the pathogenesis of maedi visna
Caused by lentivirus (retrovirus)
Infected as lambs via colostrum/milk
Long incubation period > 3 years
Causes lymphocytic infiltration of the lungs, udder, joints and nervous tissue
Often have concurrent Jaagsiekte or Pasteurellosis
What are the clinical signs of maedi visna?
Exercise intolerance
Weight loss
Progressive tachypnoea and dyspnoea
Indurative mastitis (firm, solid udder)
How is maedi visna diagnosed?
Ab test, ELISA, AGIDT
Slow to seroconvert - 6 months
PM - firm, rubbery, heavy lungs
How is maedi visna treated?
Early cases - corticosteroid, but only if in respiratory distress
High dose broad spec antibiotic for 3-4 weeks
Tracheotomy - high value animals
Describe the pathogenesis of caseous lymphadenitis
Corynebacterium pseudotuberculosis Flock problem Spread by skin abrasions e.g. via shearing equipment Abscess in regional LN Discharging LN - bacteria survive
What are the clinical signs of lymphadenitis?
Firm, palpable swellings involving LN anywhere on body
~ 25% sheep only have interal abscesses
How is caseous lymphadenitis diagnosed?
Bacterial culture - if suspect and get -ve culture then culture again
Presumptive - flock hx, CS
Serology - ELISA (high spec and sens)
How is caseous lymphadenitis treated?
No tx Isolate/cull animals with discharging lesions Gd hygiene at shearing and dipping Blood test and cull seropositive animals Vaccinate
