Larval paramphistomosis



Introduction


In the past paramphistomosis (infection with rumen fluke) was not considered to be a significant parasitic disease in cattle or sheep. However, over the past few years there has an increase in the number of outbreaks of scour and ill thrift associated with rumen fluke in certain years. In the past few weeks clinically significant larval rumen fluke infections have been reported in both sheep and cattle by both Athlone and Sligo RVLs. We suspect this may be related to the increased rainfall in the catchment areas of these RVLs. The cases typically occur late in the grazing season, with a typical history of sudden death or unresponsive diarrhoea in sheep and cattle. It has been usually seen in weanlings at the end of their first grazing season, but all ages are susceptible. Faecal egg counts for rumen fluke eggs are unreliable for diagnosis and the presence of adult rumen fluke is not necessarily diagnostic. Post mortem examination is necessary confirm diagnosis, but response to treatment is a reasonable diagnostic approach if there is no suitable animal for PM. Treating an entire herd following diagnosis is not a proportionate response to confirming rumen fluke infestation as grazing conditions and age are major factors in onset of disease. Treatment should be confined to the clinically ill cohort but including animals that may not yet have diarrhoea.


Detailed case study


Athlone RVL have diagnosed larval paramphistomosis in a 7 month old Friesian weanling with a history of ill-thrift and very severe scour, weakness and inappetence. It was one of a group of 20 weanlings that had been grazing ground that was prone to flooding. One other animal in the group had died and 5 others were being treated. At post mortem examination, there were haemorrhagic contents in the proximal small intestines and large numbers of tiny larvae were visible to the naked eye on the mucosa of the small intestine(PHOTO). Laboratory testing detected a severe larval paramphistome infection in the intestinal contents (PHOTO).


Rumen fluke are parasites of ruminants and occur worldwide. They use a snail as an intermediate host. The adult parasites live in the rumen (first stomach) and the immature larval forms live in the small intestine. Clinical disease is due to intestinal damage caused by massive numbers of larvae in the small intestine (larval paramphistomosis). The adult flukes in the rumen are large and eye-catching at [post mortem, but are not usually considered to cause disease. The current scientific research suggests that main/only rumen fluke in cattle in Ireland is Calicophoron daubneyi which uses the mud snail Galba (Lymnaea) truncatula as its intermediate host and this is the same snail that acts as the intermediate host for the liver fluke Fasciola hepatica.


Clinical disease occurs occasionally with clinical signs including dullness, dehydration, rapid weight loss, and a severe watery scour which may contain traces of blood. long-standing untreated cases may show a swelling under the jaw (‘bottle-jaw’ or ‘pocán’). Severely affected animals may die due to dehydration. As the clinical signs described here are not exclusive to rumen fluke infection, diagnosis by clinical signs alone is unreliable. However, a severe scour and weight loss and abnormally low levels of albumin (a blood protein) in blood samples combined with a history of grazing wet ‘flukey’ ground, especially in the late summer or autumn would raise suspicions. Demonstration of rumen fluke in a faecal sample (eggs/larvae) would help confirm the diagnosis. However tests to detect the larvae rather than the egg are not routinely available in laboratories and generally it is only in severe cases that larvae are detected in faeces, therefore a negative result does not rule out larval paramphistomosis.


Control of rumen fluke should focus on reducing the possibility of exposure to rumen fluke larvae on pasture. Restricting access to fields, or parts of fields, which are or have been wet or water-logged will reduce exposure to contaminated herbage. Most of the drugs that control liver fluke DO NOT kill rumen fluke. Although not specifically licensed in Ireland for the treatment of rumen fluke, it has been reported in the scientific literature that products that are licenced for liver fluke containing oxyclozanide as an active ingredient can kill both mature and immature stages of this parasite. Cattle may occasionally show transient scouring, inappetence and dairy animals may have decreased milk yield following treatment. As the dosages and treatment frequency described in the literature for oxyclozanide against rumen fluke differ from those recommended for liver fluke control, you should contact your veterinary surgeon for advice.

Species: Bovine
3:11 PM on Wed, 10 November

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