Liver Fluke: A further insight into it’s effect on livestock.

Liver fluke infections cost the UK farming industry an estimated £300 million per year, through animal death, or decreased productivity in chronically infected animals that may show no obvious signs of disease.

At Ridgeway Research Ltd we are committed to animal welfare and aiding the scientific understanding of parasite life cycles and their control.

At our laboratory we maintain the Liver Fluke life cycle, producing and supplying metacercariae to Universities and Pharmaceutical Companies. Find out more information here. These metacercariae are used in research to gain a better understanding of the parasite, its control and the growing problem of its resistance to anthelmintic treatments. We also provide a test for Liver Fluke infections to help you accurately target treatment.

If you want to find more information, NADIS can keep you up to date with latest trends in animal diseases and for more information about liver fluke specifically in cattle or sheep visit COWS and SCOPS respectively.

Below is an example of some of the additional work done at Ridgeway Research Ltd, this was presented as a poster at the 2019 British Society of Parasitology meeting at Aberystwyth University.

For those of you who might be interested in our work, keep an eye on our website, facebook and twitter.


Comparison of hepatic, pathology and antibody responses in lambs challenged with comparable numbers of Fasciola hepatica metacercariae.

C A Fenn1; S N Smith1; B L Rees1; M A Fisher1; P Goodwin2; R Jones2; C L Webster3; R M Morphew3; P M Brophy3

1Ridgeway Research Ltd (RRL), UK; 2Bio-check (UK) Ltd, UK; 3Aberystwyth University – IBERS, UK


Introduction

  • The differential outcomes of Fasciola hepatica infection on the liver pathology and blood chemistry in naturally infected ruminants are well known. In addition, hepatic and peritoneal changes and immune responses have been recorded in vaccination studies following experimental challenge infections. However, the variety and range of effects of fascioliosis on individuals is not well characterised. 
  • This study aimed to measure this variation using commercially reared Texel X lambs given a defined challenge of F. hepatica isolate. 

Method

In total, 15 female and 2 male (castrated) weaned lambs of approximately 6 months of age having no previous exposure to liver fluke, were each challenged with 200 metacercariae from a confirmed triclabendazole (TCBZ) susceptible F. hepatica isolate (Italian Strain RRL), the infections were staggered over a 3 week period.

At post mortem (12 weeks after metacercariae challenge), data from each lamb was collected for:

  • Body weights
  • Liver weights
  • Number of adult fluke
  • Liver conditions

Liver damage was assessed by dissection of the parenchyma tissue and evaluation of the level of damage (graded 0 to 3). Assessment of bile duct wall damage in terms of thickening and calcification was done by incising along the main bile ducts.  Each evaluation of bile duct thickening was made using the following visual based graded system:

  • 0 = Liver with normal appearance
  • 1 = Mild adverse changes in liver morphology.  Evidence of mild thickening throughout the bile ducts.
  • 2 = Moderate adverse changes in liver morphology. Evidence of thickening throughout the bile ducts or localized patches of marked thickening.
  • 3 = Severe adverse change in liver morphology. Evidence of marked thickening throughout the bile ducts.
  • Images of liver pathology were taken, blood samples collected for liver enzyme analysis (Gamma-glutamyl transferase (GGT), Glutamate dehydrogenase (GLDH)), and antibody response testing.
  • Results were captured in an electronic database, summarised and analysed as appropriate.

Results

  • During the 12 weeks of infection animals maintained reasonable body condition and showed no adverse clinical signs, figure 1.
  • Number of fluke vs liver weight is plotted in figure 2.
  • Results demonstrated an arithmetic mean infection rate of 51% (range 19.5 to 83.5%), figure 3.
  • Liver morphology scores revealed moderate adverse changes in 3 of the animals (17.6%), the remaining 14 exhibiting mild changes, figure 4.
  • High levels of liver enzymes; GGT up to 13 times the normal range and GLDH up to 40 times the normal range, figure 5 and 6.
  • All showed a positive antibody response, figure 7.
  • No differences were seen between animal sexes.
Ridgeway Research Ltd | Comparison of liver weight to body weight
Figure 1: Comparison of liver weight to body weight
Ridgeway Research Ltd | Comparison of liver weight and fluke burden
Figure 2: Comparison of liver weight vs fluke burden
Ridgeway Research Ltd| Yeild of adult fluke from challenge
Figure 3: Graph showing % yield of adult fluke
Ridgeway Research Ltd| Comparison of liver damage vs number of fluke
Figure 4: Comparison of liver damage vs number of fluke
Ridgeway Research Ltd| Number of fluke vs GGT
Figure 5: GGT in blood vs number of fluke
Ridgeway Research Ltd | Number of fluke vs GLDH
Figure 6: Number of fluke vs GLDH
Ridgeway Research Ltd|Comparison of number of fluke vs antibody response
Figure 7: Comparison of number of fluke vs antibody response

Discussion

  • The study confirmed variation in individual host responses in a challenge that could lead to chronic fascioliosis, with no apparent correlation between, or clear trends in, the levels of fluke infection and pathological, biochemical or antibody responses in the parameters examined.
  • Further investigation of host and parasite responses will be undertaken on samples from these animals.
  • Future studies will repeat the experiment with significantly lower F. hepatica infection levels in an effort to delineate individual response profiles.

 

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