The digger was wounding the tubers sufficiently to allow infection.
However, the pits were exposed to the open air for several days until they were nearly full, allowing ongoing infection of the rat population.
This coat enables an infecting T. brucei population to persistently evade the host's immune system, allowing chronic infection.
The epidermis may be hyperkeratotic and warty and this predisposes to tissue cracks and allows secondary infection.
They must be hypoallergenic and avoid the "wick effect" that would allow fluids and thus infection to penetrate the body along the suture tract.
Because HSV-1 can also live in saliva, sharing kitchen utensils or drinking glasses can also allow infection.
It is the spread of urediniospores which allows infection to spread from one cereal plant to another.
Operating systems that allow easy infection of viruses should have their purchase price repaid under warranty and banned.
Unfortunately gill damage to the fish is often the result, allowing secondary infection by all manner of parasites, bacteria and fungi.
As the larvae weaken the roots the adults feed on the leaves and flowers of the plant, killing the plant outright or allowing infection by opportunistic fungi.