Table 4.
Risk factors described in observational studies (n = 27).
| Risk factorsa (n = 84) | Risk factor details |
|---|---|
| Biosecurity (n = 19) | All-in-all-out vs. continuous flow (n = 7), mixing/cross fostering (n = 5), internal and external biosecurity (n = 5), air space separation (n = 2), piglet movement between stages (n = 3), infection control (n = 4), dead pig removal (n = 1) |
| Vaccination of dams (n = 14) |
Porcine reproductive and respiratory syndrome virus (PRRSV) (n = 4), Porcine Circovirus type 2 (PCV2) (n = 3), Enterotoxigenic Escherichia coli (ETEC) (n = 3), rotavirus (n = 1), not clear or unspecified (n = 3) |
| Housing (n = 13) | Pen floor type (n = 4), space allowance/pig density (n = 4), use of bedding (n = 2), drinker type (n = 2), climatic and temperature conditions (n = 3), age of buildings (n = 1), indoors vs. outdoors (n = 1) |
| Vaccination of pigletsb (n = 11) | PRRSV (n = 4), PCV2 (n = 4), not clear, or unspecified (n = 5) |
| Weaning (n = 9) | Weaning age (n = 8), mixing at weaning or weaning management (n = 3) |
| Feed regime (n = 5) | Restricted feeding (n = 4), creep feeding (n = 3), starter diet protein content restriction (n = 1) |
| Producer education (n =4) |
Experience level of manager/producer/worker (n = 3), Education level of manager/producer/worker (n = 2) |
| Feed type (n = 3) | Pelleted nursery feed (n = 1), feed composition quality (n = 1), level of soybean and canola (n = 1) |
| Feed additive (n = 3) | Zinc product (e.g., ZnO) (n = 3) |
| Air quality (n = 3) | Ventilation (n = 3) |
Categories of risk factors presented in order of decreasing frequency.
a
Risk factors included modifiable exposures regardless of the positive or negative impact of the exposure on an outcome.
b
Piglet vaccination includes suckling piglet or nursery pig vaccination.