As flocks tend to be negative when a day old but develop some contamination between 2 and 3 weeks of age, the pathogen may enter the house through one or more vectors. Increasing biosecurity could help reduce the rate of infection. Yet, as the vector is not well-understood, it is difficult to eliminate. Many vectors are considered to be potential causes of the disease, from flock to flock carryover, poor washing practices, farm staff, visitors, water and feed to flies and other insects.
Biosecurity alone does not seem to be able to provide a solution. Research has shown that contamination rates can be reduced by over 50% with stringent biosecurity measures, but not eliminated. Unfortunately, it is very difficult to maintain such high standards of biosecurity under commercial conditions, therefore a much lower reduction may be more realistic.