Campylobacter jejuni, a leading cause of bacterial gastroenteritis, has different age distribution and disease expression in developing and developed countries, which may be due to the endemnicity of infection and the age of acquisition of immunity. Differences in disease expression are not solely dependent on the C. jejuni strain or virulence attributes. Another modulating factor in developing countries may be endemic nematode infections such as Trichuris, which drive type 2 cytokine responses and down-regulate type 1 immune responses. In this study, three-day-old germfree pigs given dual infections with Trichuris suis and C. jejuni had more frequent, more severe diarrhea and severe pathology than pigs given no pathogens, only T. suis, or only C. jejuni. These pigs had significant hemorrhage and inflammatory cell infiltrates in the proximal colon where adult worms were found, and abscessed lymphoglandular complexes in the distal colon with intracellular C. jejuni. Pigs given only C. jejuni had mild clinical signs and pathology, and bacteria in feces or extracellular sites. Pigs given T. suis or no pathogens had no disease and minimal pathology. Thus, these agents synergized to produce significant disease and pathology, which was site specific.