Rumen fluke in cattle: Future research perspectives
Take home messages:
- There is often no clinical sign of rumen fluke, but if calves grazing waterlogged pasture show signs of severe diarrhoea, rumen fluke diagnosis should be considered
- Rumen fluke infections are often seen as co-infections with liver fluke, as they have a similar lifecycle.
Rumen fluke infections have been identified in cattle since the 1950’s, yet in the past decade more attention has been given to their presence due to increases in reports of cases in ruminant livestock, especially cattle.
Clinically, there is thought to be little significance of the parasite in the UK, but it’s important farmers remain aware of it. This article will outline some of the scientific details that we know about rumen fluke and how the Institute of Biological, Environmental and Rural Science (IBERS) parasitology research at Aberystwyth University is paving the way in lab and field discovery research.
What we know so far
Prevalence of rumen fluke appears to vary between regions of the UK, but it is generally accepted that there is one prominent species – Calicophoron daubneyi.
Rumen fluke infection is often seen as a co-infection with liver fluke, likely due to similarities in the lifecycle including the same intermediate host.
Infected cattle excrete rumen fluke eggs within faeces, which then develop within pasture to hatch larvae which go on to infect the intermediate host - mud snail Galba truncatula.
Once the infection has developed within the snail, the snail sheds larvae onto the pasture, which encyst, forming the worms that are ingested by grazing cattle.
These immature fluke migrate to the small intestines where they latch onto the mucosa and feed. It is at this stage that a clinical infection is more likely to be found.
Once the flukes mature to adults they migrate to the rumen where highest densities are found in areas where papillae are located, mainly the rumen and reticulum.
The adult fluke anchor onto these papillae which causes a mechanical irritation and morphological changes.
Although there are often no clinical symptoms of the disease, at the rumen level there is a chronic inflammatory reaction and pathological changes at the site of interaction between rumen fluke and the cattle host.
A number of deaths in young cattle have been recorded due to very large burdens of immature rumen flukes.
These severe cases were associated with acute diarrhoea and dehydration amongst other symptoms but had to be confirmed as a rumen fluke infection via post-mortem.
Furthermore, the diagnosed calves had come from waterlogged pasture, which is a prime environment for the intermediate snail host of liver fluke.
Thus it has been recommended that if vulnerable livestock from commonly flooded grazing areas are presented with severe diarrhoea, an infection with rumen fluke should be considered in the diagnosis.
Difficulties in diagnosis
The closeness in the relationship of rumen fluke to liver fluke has created difficulties in diagnosis and treatment. The presence of rumen fluke eggs can make the diagnosis of liver fluke through faecal egg counts (FEC) more difficult. The egg morphology is similar, but rumen fluke eggs are identified as a paler egg, compared to the yellow colour of liver fluke eggs.
Secondly, the treatment practice of rumen fluke has proved to add some implications to liver fluke anthelmintic resistance. Oxyclozanide is effective against rumen fluke and also liver fluke, but only at the adult stage of the lifecycle.
Cattle are able to tolerate high loads of rumen fluke without seemingly having any detriment to health or production. Therefore, it is disputed as to whether a routine use of oxyclozanide for rumen fluke should be utilised at times of the year when immature liver fluke infections are present.
A reduction in the routine usage method may help in a reduction in flukicide resistance within liver fluke.
Finally, as fluke-parasites are connected through lifecycles and co-infections, it is difficult to tease out the full effects of rumen fluke on production.
Weight loss in cattle has been attributed to high immature rumen fluke loads. Yet, through the use of scientific modelling that accounts for liver fluke presence as well as rumen fluke, there was a lack of effect of rumen fluke on production losses in cattle. Although this would need to be verified in whole animal studies.
IBERS – driving rumen fluke on-farm and lab discovery research
Rumen fluke infections are likely to continue at a higher level. Although farmers should not be overly concerned, it is something that they should be aware of, especially on wet farms and during wet summers.
However, rumen fluke have a high genetic diversity similar to liver fluke which will likely mean that they are also highly adaptable. Thus there is a need for us to understand more about these parasites.
Work at IBERS, Aberystwyth University, is striving to develop a greater understanding of rumen fluke which will lead to better management and control strategies in the future.
Scientists have identified that within Wales the intermediate rumen fluke host is the same as liver fluke – G. truncatula. Further work is ongoing to establish the prevalence of rumen fluke within Wales. Furthermore, on-farm data is being utilised within scientific modelling to establish a better picture of the risk factors related to rumen fluke infections over Wales as a whole.
In the lab, discovery projects are working to develop our understanding of the parasite as a whole and the interaction between the fluke and the host within the rumen.
These studies will help clarify the effects of adult rumen fluke burdens on cattle production.
Through a better understanding of the fundamentals of the parasite, more informed management strategies can be undertaken in the future.
Diagnostics to differentiate between rumen and liver fluke would be highly beneficial to prevent misdiagnosis, therefore work is ongoing to identify biomarkers for diagnostic tests.
Finally, the group is also looking at screening natural products for their anthelmintic properties against rumen fluke to improve the current reliance on one drug.
Published by kind permission of Farming Connect