Stomach flukes (Calicophoron calicophorum and Paramphistomum ichikawai) rarely cause disease in sheep or goats (and only occasionally in yearling cattle when very heavy burdens are present e.g. coastal northern NSW).
Stomach flukes are conical-shaped parasites with adult flukes found mainly in the fore stomach (reticulum, but also in the rumen). They have a fleshy, pear-shaped body, 5–12 mm long by 2–4 mm in diameter in the lower body, and are pink or light red. Juvenile fluke are small (1–2 mm long) and are found in the small intestine and easy to overlook at post-mortem examination.
The life cycle (and distribution) of the stomach fluke is similar to that of liver fluke, as both use an aquatic snail as an intermediate host. The flat planorbid (or ram’s head) snail transmits paramphistomes, but does not transmit liver fluke. Also, paramphistomes stay within the stomachs and small intestines rather than migrating to other tissues as do liver flukes.
As sheep and goats rapidly develop strong resistance to this parasite, 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 mostly in weaners or in adults that have been imported from an area with no stomach fluke. The signs are from inflammation of the upper small intestine (duodenitis) caused by large numbers of migrating immature fluke.
Anaemia, low blood protein (manifested as bottle jaw) and weight loss are seen in very significant infections, which are very rare. After juvenile fluke migrate back 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 specifically for use against stomach fluke in Australia.
Download pdf below: Stomach Fluke in Ruminants Primefact 452 NSW DPI