Over the years, it seems like different species of tapeworms are increasing in frequency, with the risk of production losses also increasing. It also appears the risk of contacting a potentially very serious human disease is also increasing. (I will briefly cover this disease, echinococcus, at the end of this article.)
We see different tapeworm species in all the domestic animals and owners need to keep an eye out for them or develop preventive deworming strategies when necessary in conjunction with other deworming practices.
The nice thing is that with most of the common species, you can see segments shed in the manure if levels get high enough and so you know you potentially have a problem. Some species get very large and long and attach to the intestinal track and really raise eyebrows when they are passed.
Certain dewormers do not regularly control tapeworms — whether in horses, sheep or cattle — so even with a regular deworming program, levels can build up. They also sporadically shed the segments, which contain the eggs. So levels may appear to fluctuate when doing routine fecal counts. With some species of tapeworms (such as the one that infects horses), you cannot see the eggs with routine fecal exams. This is why some veterinarians would recommend using a horse dewormer containing Praziquantel every so often.
Tapeworms belong to the cestoda group of (flat) worms and they do look like a flattened-out worm. They all require an intermediate host to complete their life cycle, making them different than nematodes (the more common internal roundworms we treat in production animal practice).
In production animal species such as cattle, sheep, or bison, it has always been thought the taenia species don’t cause much in the way of production losses. However, they do seem to be showing up in increasing frequency and I have personally seen very high levels in bison calves.
The intermediate host for the taenia species is an oribatid mite but immunity against this tapeworm seems to develop well. We rarely see tapeworms in adult cattle and bison, but rather in the calves and yearlings. This indicates that immunity does develop. In sheep, when identified and dewormed with the appropriate dewormer, there can be a large number of tapeworms passed, which suggest they have almost been causing a blockage.
When one sees evidence of these tapeworms, keep in mind there is probably a mixed bag of internal worm infection and doing fecals from several animals may be in order. They are unsightly things, so if there is evidence of tapeworms, investigate further in regard to other parasites and get advice from a veterinarian. Some of the dewormers on the market don’t get tapeworms or the dose must be increased. The eggs look like a diamond shape on the fecals so very easy for the veterinary technicians to differentiate from other species of worms.
Your farm dogs and cats should be treated for tapeworms as well.
We often see the dried segments, which look like cucumber seeds stuck to the butts of cats. Cats that are good hunters can get bad cases from eating mice or birds. Usually the frequency of deworming is based on how good a hunter they are. Your local veterinary clinic can advise on the best product. We think of deworming out horses and production species on the farm but that should be extended to farm cat and dog populations.
Sheep can also get the larval stages of the tapeworm taenia ovis. This will cause cysts in the meat called sheep measles and can result in the carcass being condemned. Infections could be prevalent in the guard dogs that essentially live with the sheep. Defecating on the pastures or in the feed bunk can exacerbate this life cycle.
On the farm, one must keep in mind the fecal to oral pathway can spread lots of organisms. So just as we need to wash our hands when they are soiled with manure and wash fruit and vegetables before consuming them, we must be mindful of this same strategy with our pets on the farm. Feed animals in bunks and clean up after pets as often as possible. Having a barrier around the sandbox and other play areas is also a good strategy.
If the sheep tapeworm, taenia ovis, is a problem, then it is recommended that you deworm guardian dogs every six weeks. This will prevent spreading and so will not feeding them raw sheep meat (as that completes the tapeworm life cycle).
A tapeworm that infects dogs and coyotes appears to be increasing in prevalence in Alberta over the last several years.
Echinococcus multilocularis is a very tiny tapeworm that lives in wild canids (such as coyotes) but can also get in our domestic dogs if they consume rodents. Infected rodents can develop Alveolar echinococcosis, a disease that leads to a cystic-like structure developing in the liver and can eventually lead to liver failure.
The scary part is this is a zoonotic disease and the same thing can happen in humans if they inadvertently ingest the eggs of this tapeworm. It may take from five to 15 years to develop in humans. This is considered one of the scariest parasites because of the potential damage it can do. It can also be contracted from eating wild berries without washing them or other sources where there has been some contact with feces.
Most of the research on this disease has been conducted around cities like Calgary and Edmonton but coyotes are a common source so be aware as the incidence appears to be on the increase. Hopefully some studies will be done in rural areas next. Fortunately this severe disease is still very rare.
As you can see, tapeworms can affect our livestock and pets in various ways and could potentially affect us. If thinking of checking fecals for parasites consider tapeworms and when thinking deworming, definitely think of our farm dogs and cats on a routine basis.