Campylobacter jejuni has an incubation period of usually 24-72 hours before a possibly debilitating set of symptoms arise from full colonization within the host.

What are the symptoms of this creatures infection?

Headache, myalgias, chills/fever, acute diarrhea (sometimes bloody), abdominal cramping, and acute gastroenteritis are commonly experienced by the host.  Illness termed Campylobacteriosis usually lasts for about 2-5 days and can be serious if dehydration occurs.  Serious complications can be associated with this infection including Guillain-Barre Syndrome, chronic reactive arthrits, and even abortion.  Relapse rates are about 20%.

What mechanisms do these pathogens use to do their dirty work?

Most enteropathogens (causing disease in the intestinal tract) use a secretion system that allows them to deliver virulence factors which aid in adhesion and invasion of the human host cells and also regulate the immune systems response to the infection. [1] The flagellar apparatus (see diagram on Adaptations page) in C. jejuni has been found to be an important tool in host invasion, serving as a secretion system for invasion antigens and also providing the necessary motility. [5] 

C. jejuni also have been found to utilize outer membrane vesicles to deliver virulence factors. [2] Instead of secreting toxins directly into the environment where they could be broken down by the host, these vesicles allow a coordinated package of toxins to be delivered.  One toxin discovered is called Cytolethal distending toxin.  This toxin causes DNA damage leading to the shut down of the cell cycle at the G2/M phase and eventually apoptosis (cell death).

Something that is very interesting about these vesicles is that they have been found to actually purposefully initiate immune response.  One might think the best plan of action is to lay low and try not to cause too much commotion regarding the immune defense system but these bacteria take the chaotic path and just go with it.  The result of initiating this immune response turns out to benefit C. jejuni because it ends up damaging the epithelial barrier function from severe inflammation. [2] This loss of integrity in the cell membranes allows for even easier endocytosis of the vesicles leading to further damage.

This isn't the only situation where Campylobacter jejuni causes the body to harm itself.

C. jejuni is a common infection preceding the onset of symptoms including weakness and paralysis.  Certain strains have been found to have lipo-oligosacharide structures that mimic gangliosides found in human nerve and brain cells. [2] The consequence of this sly mimicry is that antibodies produced in the immune response to the presence of C. jejuni go on to attack and destroy the hosts own nerve cells.  This leads the auto-immune disorder Guillain-Barre syndrome, 40% of the patients with this syndrome can be found to have had a recent infection. [3] To learn more about this syndrome check out this Mayo clinic website.