Stomach fluke rarely causes disease in sheep (and only occasionally in cattle eg coastal northern NSW).

The life cycle of the stomach fluke also involves a snail (a different snail to that involved with liver fluke). Paramphistomes or stomach flukes are conical shaped parasites. Adult flukes are found mainly in the forestomachs (reticulum but also in the rumen). They have a fleshy, pear-shaped body, five to twelve millimetres by two to four millimetres in diameter, and are pink or light red. Juvenile fluke are small (one to two millimetres long).

Most infections of adult fluke are harmless although large numbers of fluke can cause damage to the lining of the rumen. When disease does occur, it is due to inflammation of the upper small intestine (duodenitis) caused by large numbers of migrating immature fluke.

Juvenile fluke are attached to the lining of the intestine and, being small, are easy to overlook at post-mortem examination.

Anaemia, low blood protein (manifested as bottle jaw) and weight loss are seen in significant infections, which are very rare. After juvenile fluke migrate to the rumen, the intestine repairs but remains thickened.

Fencing to restrict access to wet snail habitats will aid in control. There are currently no anthelmintics, including Nilzan, registered for specific use against stomach fluke in Australia.