Older animals appear to have a strong protective immunity, keeping infections low in those animals. In heavy infections, a bloody diarrhea may occur durring the prepatent period. Larval stages developing in the submucosa are responsible. A consequence of this tissue penetration is secondary infection , particularly with Treponema hyodysenteriae, the cause of swine dysentery. Clinical manifestations of severe whipworm infections include diarrhea, anemia, anorexia, poor growth rates, dehydration, emaciation, and death.
Diagnosis is by identification of the characteristic egg in feces.
However, in cases of severe diarrhea occurring during the prepatent period, a definitive diagnosis can often only be made at necropsy. Because it is a soil-transmitted helminth it is seen most commonly in pigs with access to soil or pasture.