WormMail – Tapes and Trematodes

Lovely, isn’t it? 🙂

This little beauty was found when Armidale-based wild dog researcher Dr Guy Ballard, along with Dr Gerhard Koertner and Dr Tommy Leung, dissected a quoll.

For those who don’t know much about Australian marsupial carnivores, the quoll is a cat-sized ‘dasyurid’ with plenty of attitude, like Tasmanian Devils, African honey badgers and north american wolverines. (‘The name Dasyurus means "hairy-tail",[5] and was coined by Étienne Geoffroy Saint-Hilaire in 1796 – according to wikipedia.).

Dr Leung identified and photographed this trematode. (Please respect Dr Leung’s rights regarding this image).

Christine Reed (Manager, Risk AnalysisMAF Biosecurity New Zealand) in a 2009 report, citing Spratt, says:

"Mehlisia acuminata: This species infects some dasyurid species but no other marsupials (Spratt et al 1991).
Although the life cycle of this parasite has not been elucidated, all trematodes have complex life-cycles requiring intermediate hosts and sometimes additional paratenic hosts".

Spratt DM, Beveridge I, Walter EL (1991). A catalogue of Australian monotremes and marsupials and their recorded helminth parasites. In: Jones PG, Horton P, Mathews EG, Thurmer J (Editors), Records of the South Australian Museum. Monograph series 1. Australian Government Publishing Service, Adelaide.

See also Beveridge and Spratt (1996).  The Helminth Fauna of Australasian Marsupials: Origins and Evolutionary Biology. Advances in Parasitology Volume 37, 1996, Pages 135-254

Did you know there may be up to 24,000 species of trematodes (flukes)? (Greek trēmatōdēs, having holes.  Maybe I should call my socks by the same name??)

Tapeworm in lambs

Dr Bruce Watt has just written a very nice article on this subject for his local (Bathurst) rag. This was discussed in a recent WormMail.

Here is Bruce’s article (reproduced with permission):

"SHOULD YOU DRENCH LAMBS FOR TAPEWORMS

Sheep producers are divided into two camps on the great debate on whether to drench lambs for tapeworms or not.

Those in favour, argue that tapeworms must be doing something. After all, the segments are obvious in the manure of lambs. If you follow up with a post mortem, you sometimes find that their intestines seem almost choked by long white tapeworms.

As an aside, you will no doubt be fascinated to learn that a New Zealand lamb holds the record with 41 tapes. Apparently, students of sheep parasites refer to the volume of tapes that a lamb might carry. This rarely exceeds 200 ml but can be as large as 280 ml, which is a middy. Imagining that may help if you need to reduce your alcohol consumption.

Those who don’t drench lambs for tapeworms however argue that research has shown that tapeworms don’t cause any harm and are not worth treating.

Having done some homework on this subject and communicating with colleagues, Drs Brown Besier and Stephen Love, both eminent parasitologists, I can now give you an opinion.

The first study I found on this subject was conducted on prime lambs in the Armidale district in the early 1970s. The veterinarians who ran the trial took 100 spring and later 100 autumn drop lambs and drenched half with ‘Mansonil,’ a product that kills tapeworms. They repeated this treatment every three weeks. They also drenched both groups regularly with levamisole to take care of the other worms.

At the end of the trial they found that the spring lambs treated for tapeworms gained 33.0 lbs (back in the pre-metric days) while the untreated lambs gained 31.9 lbs. The autumn lambs treated for tapes gained 39.75 lbs while the untreated lambs gained 40.0 lbs. The veterinarians concluded that this difference was not significant.

In New Zealand, numerous studies have looked at possible benefits to treating lambs for tapeworms. None showed any advantage. This led DC Elliot from the Wallaceville Animal Research Centre to conclude that there was ‘no justification for treating sheep for Moniezia expansa (the scientific name for these tapeworms) on the basis of any likely benefit to the health or production of the animal.’

So the case seemed settled. However, a Kiwi team led by J Southworth decided to take another look at this issue. In October 1993, they divided 300 Romney lambs into three groups. Group one received no worm treatments of any kind. Group 2 were drenched with levamisole to take care of round worms but not tapes. Group 3 were treated with both levamisole and praziquantel, taking care of both round worms and tapeworms. Praziquantel is a highly effective, relatively new treatment for tapeworms including hydatids in dogs.

Southworth and team found that the untreated lambs gained 7.56 kg from October to December, while the lambs treated with levamisole for roundworms only, gained 8.53 kg. However, the lambs treated with both levamisole and praziquantel gained even more. They gained 10.53 kg over the duration of the trial. These differences were all statistically different.

With only one New Zealand trial showing a benefit and many showing no benefit, it seems unlikely that treating lambs for tapeworms is worthwhile. However, that may not be correct under all circumstances. If sheep producers on the tablelands would like us to study this in our area please let me know.

In the meantime, we can be sure that the other worms, including barber’s pole worms, which are rife now, must be controlled. If farmers concerned about tapeworms use products that are less effective or inappropriately timed for the control of the other worms, then tapeworms really can cost money."

~~~~~~~~~~~

Some notes:

‘Mansonil’ (Bayer; active = niclosamide) was a common tapewormer for sheep but was supplanted by praziquantel (the active ingredient in ‘Droncit’ (and similar) for dogs).

There are a number of ‘wormers’ on the market now for sheep that combine a broad-spectrum with praziquantel. In deciding which product to use by far the most important consideration is whether the broad-spectrum works on your property…(against the really important worms, ie the not-so-easy to see nematodes, like barber’s pole worm (Haemonchus), black scour worm (Trichostrongylus spp) and small brown stomach worm (Teladorsagia/Ostertagia circumcincta).

And, as always, its important to read the label. Did you know for example that ‘Cydectin+Tape’ (moxidectin+praziquantel) has no claim for persistent activity against barber’s pole worm, unlike its sibling, ‘Cydectin Oral’ (which is sans praziquantel)??

One of the first combination broad-spectrum+tapewormer products on the market for sheep in Australia (in the last 15 years at least) was ‘FirstDrench’, which contained levamisole + praziquantel. As implied, this was targeted as the first drench for lambs. The praziquantel doubtless worked fine on tapeworms, but on most properties would have been less than highly effective against the scour worms (Trichostrongylus and Teladorsagia) as resistance of these genera to levamisole was already widespread. Thankfully FirstDrench was soon followed by ‘FirstMectinDrench’. The broad-spectrum in this is abamectin, which is somewhat more likely to be effective against the scour worms than levamisole.

In short, concentrate most on what is most important.  (There is probably a time-management principle in this as well).

Why did Southworth et al find a significant response to treatment for Moniezia, when virtually all other trials have found no significant/detectable benefit in treating for tapeworms? Who knows?  Perhaps tapeworms generally produce little in the way of negative effects on lambs because they are so well adapted to the host???   and/or they have an immuno-modulatory effect (like Trichuris/whipworm infection in humans with ulcerative colitis).

Much of the negative effect of worms on their host can be due to the host response, as well as direct effects from the worms themselves.  Perhaps in the Southworth trial the hosts -for some reason – were not in a state of relative ‘immuno-tolerance’?    I really don’t know.

Another of life’s mysteries.

Regards

SL

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