Essentially Lucy’s problem is her diet of raw salmon. Tapeworms of all types (and in all species) are acquired through the ingestion of eggs, either from eating faecal material or inadequately cooked meat (see diagram for life-cycle).
There are lots of different types of tapeworm; the most common of those seen in humans are listed below with the type of meat they are acquired from.
• Taenia saginata – beef – up to 10m in length
• Taenia solium – pork – up to 3m in length
• Diphyllobothrium latum – fish – up to 10m in
• Hymenolepis nana – human faeces – only 40mm
All of these organisms can cause chronic infections which only come to light because the patient is either shown to be anaemic and has an eosinophilia (due to blood loss and failure to absorb vitamin B12 because the tapeworm absorbs this), or they actually pass a worm in their stool... not a pleasant experience I suspect.
In order to diagnose these infections unless of course a worm has actually been seen (please send them in...Microbiologists like to see them!) the microbiology laboratory examines the patient’s stool looking for evidence of worm eggs. Usually three separate samples would be examined before the laboratory releases a negative result because the worm eggs can be very hard to find and identify.
The treatment in humans is relatively straight forward. A single dose of PO Praziquantel 5-10mg/kg is enough to treat most tapeworm infections. H. nana is slightly more difficult to treat and requires 25mg/kg of PO Praziquantel with a second dose given 1 week later (I don’t know why this is the case, do leave a comment if you know). In H. nana a stool sample should be retested 3 weeks after the second dose.
In bears, intervention is less easy, but treatment is actually similar, PO or subcutaneous Praziquantel 5mg/kg! It is thought wild bears may expel adult egg-laying worms prior to denning as they have fewer tapeworms in spring compared to autumn. However when they start eating raw salmon again, high tapeworm levels return. Put simply bears have chronic infections and there really isn’t much that can be done about that.
P.S. I strongly recommend Bella Coola in British Columbia for Bear viewing.