Getting the measure of tapeworm and ELISA Testing

When conducting a faecal worm egg count it is not possible to give an accurate estimation of tapeworm burden. The reason for this is tapeworm eggs are stored within segments of the tapeworm. As the segment breaks off if it canrupture and the eggs are dispersed in the dung, however if it does not rupture then the eggs remain inside and a faecal test will not indicate an accurate level of infection.

There is a way to estimate a horses tapeworm burden through an ELISA test developed by Professor Chris Proudman of the University of Liverpool. Currently the University is the only laboratory in the world that can run this ELISA test. ELISA stands for Enzyme Linked Immunosorbent Assay, it works by detecting the level of antibody in the immune system.

The tapeworm ELISA test can be used if your vet is concerned that your horse has a tapeworm infection, or it can be used in a targeted worming programme to detect if a tapeworm treatment is required or not.

To carry out a tapeworm ELISA your vet will need to take a blood sample and send it off to Diagnosteq at the University of Liverpool. At the lab they test the blood serum sample against a standard positive tapeworm sample.  The result given provides an indication of the level of IgG(T) antibody that is present in the serum sample. If the horse has never had a tapeworm infection then the result would be clear as it has never had to make a tapeworm antibody. However if there has been a tapeworm infection then a positive result will be reported.

The important thing to remember is that this test looks at trends, this is vital in the interpretation of results. Because the test measures the antibody it is important to remember that once the horse has been exposed to the tapeworm antigen its immune system will have created an antibody which will remain in the system. Therefore if the horse was exposed to the tapeworm antigen again then the immune system could quickly increase the level of antibody to fight the tapeworm antigen.

This means that if a horses first ever tapeworm ELISA test returns a low positive result it could mean the horse has a low tapeworm burden, or that it has been exposed to tapeworm in the past either way at a low level it is not a huge concern. If the horse has had a tapeworm burden then the reading will never go back to clear because the immune systems memory keeps a small amount of antibody in the system. If the second reading increases from clear to low this would indicate some tapeworm activity. If it increases from low to medium or high then this is indicative of a tapeworm infection.  If there is a medium or high reading and this infection is treated then the level of antibody can drop to low positive but will never return to clear.

So when looking at the results from a tapeworm ELISA it is important to remember that you are looking for a trend. Unlike a faecal worm egg count you are not looking at a number of egg per gram which is indicative of a low medium or high reading, you are looking for a trend of tapeworm antibody in the system. 

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