Swine 11 Flashcards
most common cause of diarrhea in swine???
Salmonellosis
types of salmonellosis in swine and what causes them? hosts?
-Enteric form caused by S.Typhimurium
> Can infect other livestock, poultry, mice, and people
> Pigs are considered most likely source of S. Typhimurium DT104 in people
-Systemic form caused by S. Cholerasuis
> Host-adapted** i.e., considered restricted to swine
> Rare reports in humans out of Asia (**zoonotic potential)
> Can live in mice
salmonella seotype diversity? general characteristics? toxins? how to inactivate?
n >2000 Salmonella serotypes
n Salmonella are notoriously diverse
n Hardy, small, ubiquitous, gram-negative bacilli
n Contain ENDOTOXIN
n Inactivated by iodine and phenol-based disinfectants
where in the host in salmonella generally found? how does it spread? are there always clinical signs? when do we usually see a clinical outbreak?
- Salmonella in gastrointestinal tracts (of many hosts)
- Spreads via fecal-oral route
- New infections in pig herds
> Usually, fecal contaminated feed or water
> Pigs may act as asymptomatic carriers = source of infection especially if comingling pigs or new introductions into herd - Farm may be positive with no clinical signs of disease
- Clinical outbreak typically follows a stressful event
> Shipping, mixing, overcrowding, concurrent disease
S. Typhimurium causes:
enterocolitis
Enterocolitis form of salmonella:
how it spreads? who it affects? prevalence?
- Fecal-oral route
- Typically pigs in nursery to mid-grower
> ~50% herd prevalence in Ontario
> ~2% recognize as a problem
S. Typhimurium: pathogenesis
- Endotoxin results in mucosal GIT damage and endothelial necrosis
> Vasculitis, microvascular thrombosis - Diarrhea attributed to tissue fluids leaking from damaged mucosa. Malabsorption diarrhea
S. Typhimurium – Clinical signs? sequelae?
Enterocolitis form of salmonella:
- Moderate pyrexia, anorexia and dehydration
- Typically, a yellow-coloured diarrhea due to fluids leaking through the damaged mucosa
> As progresses more mucus, fibrin, and blood in feces. But blood is not a primary feature
- Morbidity high (over time) and mortality low
- May cause emaciation and slow growth
- Sequelae: rectal stricture …….rectal prolapse
S. Typhimurium – public health concerns
Public heath issue:
- Concern due to pigs shedding in abattoir DT104
- Multi-drug resistant strains
S. Typhimurium - lesions
- Lower small intestine and large intestine are heavy, edematous and thickened
- Enlarged, congested mesenteric lymph nodes
- Focal necrosis on intestinal mucosa
- Chronic cases may have raised circular lesions in the colon (button ulcers)
- Excess peritoneal fluid and strands of fibrin – peritonitis
> pigs have small amount of abdominal fibrin which is normal. Look for “excess fibrin”
S. Typhimurium – laboratory Diagnosis
Culture & Sensitivity
- Untreated animal and demonstrating typical signs
- Culture multiple organs
- PCR
- Serotype
> Special test for DT 104 by Public health Agency of Canada - zoonotic
Histopathology
- Rule-out other enteric and septicemic diseases
S. Cholerasuis causes what form of salmonellosis?
Septicemic form
Pathogenesis and transmission
Septicemic form of salmonellosis
- Fecal-oral route or inhalation of organism
- Invades tonsil (Mr. Tonsil!) and mucosa of small intestine
- Spreads to regional lymph nodes and can survive in macrophages
- Results in a septicemia and localizes in tissues where cause lesions:
> Releases endotoxin, vasculitis (present in all forms of salmonellosis)
> Liver, lung, brain, meninges, joints, lymph nodes
S. Cholerasuis - what age affected, what immunity usually protects?
All ages of pigs but usually nursery to mid-grower
- Lactogenic immunity is usually protective
S. Cholerasuis - Clinical Signs? common in ontario?
- Clinical signs mediated by endotoxin - variable
- Inappetance, depression, high fever, acute death
- Discolored skin (red to purple), cyanosis
- Diarrhea may develop later (if pig lives) but not a typical clinical sign
- Respiratory signs - dyspnea and cough
- High mortality, low morbidity
- VERY VERY rare in Ontario (last reported in 2015)
