Swine 7 Flashcards
main respiratory diseases of swine
- Mycoplasma hyopneumoniae
- Swine Influenza Virus
Mycoplasma hyopneumoniae; other names
- MH, M. hyo
- Enzootic pneumonia
geographical distribution of Mycoplasmal Pneumonia of Swine? prevalence?
- Widely distributed
> worldwide, but maybe not Switzerland - COMMON
> high prevalence
typcal type of disease caused by Mycoplasmal Pneumonia of Swine, and less common presentation? general symptoms? what type of operation is it common in and what time of year?
- Chronic respiratory disease
> there is a less common acute presentation - Coughing, reduced growth, reduced feed efficiency
- Common in continuous-flow production
- Occurs year round
significance of MPS? (3 things)
- A major swine respiratory pathogen in N.A.
- $$$$ very costly disease
- Contributor to Porcine Respiratory Disease Complex (PRDC) along with other pathogenic respiratory bacteria & viruses
Features of M. hyopneumoniae: growth, sensitivity, survival?
- Slow growth in culture: 4 to 8 wks
- Poor antibiotic sensitivity
- Poor survival in the environment
most common source of MPS?
n Carrier pigs most common source
MPS incubation time
Incubation 2-3 weeks
MPS transmission
Horizontal transmission:
- Sow-to-piglet: in crates
- Pig-to-pig: in nursery & grower
- Regional spread via aerosol at least up to 3.2 km
at what life stage is MPS a problem generally
Typical expression in grower pigs (>10 wks old)
> Grower – Finisher Phase
MPS acute herd presentation;
-severity, ages affected, symptoms and signs
- Uncommon
- Acute outbreaks in naïve farms can be severe
- All ages of pigs affected**
- Pyrexia (40-41.5C), anorexia, depression
- Severe respiratory signs:
> dyspnea, coughing, extensive lung involvement - Some peracute deaths
- Some abortions in pregnant sows due to pyrexia
MPS Endemic Herd Presentation;
- how it becomes a problem, signs and symptoms
(most common***)
- Chronically infected herds
- Susceptible (naïve) pigs exposed to M. hyopneumoniae upon entry to grower barn associated with:
> Waning passive antibody
> Shedding from older animals - Coughing develops 2-3 wks post-exposure, in the early grower period
- High morbidity
- Usually low mortality (unless complications arise)
MH/MPS clinical signs
Coughing:
- Uncomplicated: non-productive, dry raspy
- Productive coughing associated with concurrent infections (bacterial or viral)
Other signs:
- Tachypnea, dyspnea
- Uneven growth rates
Severity of MPS influenced by
- MH strain
- Pig flow
- Overcrowding (vicious circle)
- Poor air quality
MPS pathogenesis?
what increases severity?
- MH colonizes trachea and bronchial epithelial cells
- Clumps cilia > impairment of ciliary clearance
- Accumulation of secretory & cellular debris gravitate from bronchi to alveoli
- Secondary invasion: in virtually all naturally occurring MPS cases (mixed bacterial & viral infections)
- Resolution in uncomplicated cases
- Increased severity if infected concurrently with other respiratory pathogens à PRDC
MPS pathology
Bronchopneumonia (anteroventral (AV) consolidation)
- Cranial, middle & accessory lobes
- +/- cranial portion of caudal lobes
- Firm to touch (meaty)
- Deep red to dark purple colour
()
* Catarrhal exudate in airways on cut surface
* Enlarged, edematous mediastinal lymph nodes
* Characteristic (non-pathognomonic) histopathology
> Peri-bronchial lymphoid peribronchiolar hyperplasia “cuffing” - characteristic of M. hyopneumoniae
> Alveoli filled with debris and inflammatory cells
> Atelectasis
diagnostic methods for MPS (broadly)
A) Tissues (individual pigs):
B) Serology:
> herd testing – not helpful at at individual level
C) Slaughter check (herd testing)
how to diagnose MPS in swine using tissues
A) Tissues (individual pigs):
* Gross: AV bronchopneumonia (suggestive)
* Histopathology: peri-bronchiolar lymphoid hyperplasia “cuffing” (suggestive)
Confirmation
* Culture: not feasible (slow growth)
* Demonstration of antigen:
§ **PCR – lung (including airway), bronchial fluid, trachea, nasal mucosa
§ Fluorescent antibody test (FAT) on lung (sample should include airway with ciliated epithelium)
§ IHC – rarely and not widely available **PLUS demonstration of histo lesions
how to use serology to diagnose MPS? pros and cons?
Serology:
herd testing – not helpful at at individual level:
- IgG ELISA’s –DAKO, IDEXX
- Measures exposure but interpretation can be difficult:
§ Seroconversion highly variable (dose dependent)
§ May require up to 6 wks to induce IgG response following
natural infection
§ Cannot differentiate vaccine titres & natural infection
§ No correlation between vaccine titres and protection
§ Excellent specificity, but a few false positives occur
§ Sensitivity low
diagnosis of MPS via slaughter check - how to do it, what info you can gain? what samples are not reliable and why?
Slaughter check (herd testing):
- Lung lesion scoring at slaughter to determine severity and prevalence of disease
- Likelihood of MH herd infection increases if:
§ Individual lesions score >5%
§ Prevalence of infected lungs >15-20%
- PCR/FAT is unreliable on samples collected at slaughter
- due to comingling of positive and negative pigs at the assembly yard and scalding tank
4 methods for treatment and control of MPS
- vaccination
- strategic medication
- Environmental control
- Control other respiratory pathogens & ascarids
how to use vaccines to prevent MPS? what can the vaccine do? when to vaccinate? how many doses? is this a common strategy? what to keep in mind about sows and vaccination timeline?
Vaccination of sow, nursery or grower herds:
§ Vaccine reduces prevalence & severity of lesions
§ Vaccine does not prevent colonization or infection
§ Vaccinate pigs 2-3 wks prior to expected exposure
§ One and two dose products available – selection depends on severity, infection pressure & cost
§ COMMON
- If sows are vaccinated pre-farrowing, piglet vaccination must be delayed until after 6-8
wks of age due to maternal antibody interference
how to use strategic medication to treat MPS? when? how do they work and when are they useful?
Strategic medication prior to or during peak exposure:
- Antimicrobials reduce infection pressure but do not eliminate M. hyo infection
- Essential to control secondary bacterial infections
- Cost effective in grower, less so in finisher
Antimicrobial programs for MPS
Chlortetracycline in feed, also tiamulin, tylosin
§ Feed (mass medication of population):
> Continuous during periods of infection/transmission
> Pulsed (ie 1 week on/1 week off)
§ Parenteral (treatment of individual animals)
