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  1. #1
    Join Date
    Mar. 31, 2004
    Upper Peninsula, Michigan

    Default Potomic Horse Fever *without* the fever? Other ideas?

    I'm exhausted so here's the run down.

    DH's Arab mare (Tryzen) that he's had since she was a weanling and is now 14 started dropping weight rapidly over the last two weeks and had some diarrhea. Initally he wormed her with Ivermecetin and the diarrhea did not clear up. She continued to drop weight; we took her to the vet (2 1/2 hour trip) who drew blood and recommended Sand Clear or Metamucil, a Panacur Power Pack, and ProBiotics.

    Bloodwork came back today and indicated a high WBC (28,000) and that her electrolytes were all out of whack (not surprising).

    The vet is thinking this could be Potomic Horse Fever.

    Now, I really like my vet and both large animal vets in the practice have consulted on this issue. I don't think they are necessarily steering us wrongly...

    HOWEVER this mare had NOT HAD A FEVER EVEN ONCE. She's solidly in the 99 range although today DH said her temp was 97????

    Secondly, we are not in a low, swampy area with standing water, nor are we near a pond or a lake. The only "stagnant" water is our water tank which is refilled/dumped when needed. The pasture is not swampy. There is some "sour" grass (Per DH) but no swamp grass.

    I have no idea how she'd have contracted Potomic if that is the case.

    Anyway, course of action now is Naxel until Monday and if no improvement, OxyTetraCycline (sp?). Also on an electrolyte.

    I know how we all love to play armchair quarterback...

    The mare will eat grain but only picks at hay and is really not interested in going out of the dry lot into her pasture (accesss 12 hrs / day when not in her stall due to bugs). She drank about a quarter of a 5 gallon bucket today in her stall and that is it. Although that is not abnormal for her (she's a bucket weirdo).

    ANY THOUGHTS at all to help us sort this out are welcome. We'll be talking with the vet again on Monday AM regarding her progress. We are somewhat hampered by our rural area and really do like our vet.

    I just didn't think to ask her WHY we're thinking "Potomic FEVER" when the mare's temp has never gotten out of the 99 degree range?

    The mare is definitely on the thin side now, and has the gaunt look across her haunch/flank area. She was FAT before so there was some "cushion" but now we're to the point that we don't want ANY MORE WEIGHT LOSS. Still liquid poo.

    All other horses on the property look fat, happy, shiny and have nice beautiful poops.

  2. #2
    Join Date
    Sep. 18, 2005


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  3. #3
    Join Date
    Dec. 15, 2005


    Apparently there are a lot of Potomac Fever cases now. Some are in areas where there is usually no Potomac Fever. I wonder if you missed the fevers, if they were brief and not too high.

  4. #4
    Join Date
    Mar. 27, 2008


    You don't need a lot of stagnant water around. You just have to have carrier mayflies land in water/feed buckets or water troughs where the horse will ingest them.
    Some of the cases I have witnessed did not present a high fever.
    There was also an alert recently about a new strain that doesn't even cause diarrhea - making it even harder to catch.

  5. #5
    Join Date
    Sep. 7, 2009
    Lexington, KY


    Leaving lights on at night has been identified as a risk factor. It appears to attract the may flies. Horrible disease. Saw a horse with hooves sloughed off. Had to be put down.

    Here's some info from Michigan State Veterinary College:

    From what it says, horse can have diarrhea or not, fever or not (and the fever may only last several hours, colitis symptoms or not. Must be very tough to diagnose.

  6. #6
    Join Date
    Feb. 1, 2008
    Nowhere, Maryland


    Most likely she is dehydrated, if she's had diarrhea for two weeks. Did the vet mention giving her IV fluids? Biosponge or pepto? Ulcerguard? If they really think it is PHF, they should start treatment with tetracycline/ banamine right away, not do the Naxcel.

    That said, most of the PHF cases I've seen have been either dead or back to normal after two weeks.

  7. #7
    Join Date
    Sep. 16, 2006

    Default Hoary Alyssum?

    Could the horse have gotten into some hoary alyssum? My sister's horses were eating hay with this weed in it, and had pretty bad diarrhea and dropped weight (they also got a little stocked up in the back legs). Not sure if that would be it or not...I would think your vet would have already covered this. Just something to think about.

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