View Full Version : Chronic low WBC count in otherwise healthy horse -- any ideas?

Dec. 31, 2010, 04:22 PM
My 13-year-old gelding has been running low on his WBC count since last June. We found this during an exam to investigate his extremely frequent urination (bladder ultrasound, rectal, etc.). Blood chemistry was normal, but his total WBC count was 3.3 (reference range 5.5-12.5) and the RBC was a little low also.

A short course of SMZs made little difference -- afterward the WBC count was 3.6.

I then began omeprazole treatment for ulcers and within a few days the urination symptoms completely disappeared. I treated for 30 days and he has been fine ever since.

A follow-up CBC in July showed WBC count closer to normal but still low at 5.3.

We just ran two more CBCs this month. On 12/9 it was 4.8 and 12/28 it was down again to 4.3. Blood chemistry is still normal.

My vet has done a thorough exam from bow to stern and can find nothing wrong. He says it's possible there is an internal abscess that is using up white cells, or perhaps the horse just isn't making enough white cells.

He suggests waiting a month and re-testing. If the count is down, then we can try 30 days of SMZs and see if there is any change. Another option would be a bone marrow aspirate. Or we can do nothing.

The horse seems perfectly healthy and is working well. My main concern is with him being more susceptible to infection, because I am planning to show him next season. I'm not inclined to go to great lengths looking for something we may not find, or, if found, something we couldn't do anything about anyway.

Does anyone have any bright ideas, thoughts or conjectures about this?

Dec. 31, 2010, 04:57 PM
The only thing that jumps to mind is a tick borne disease infection that is mildly responsive to SMZs.

Dec. 31, 2010, 05:36 PM
The reference ranges are produced using a number of "healthy" horses distributed in a bell curve.

It *could* be that your horse just falls outside of that bell curve. His "low" WBC count may be *normal* for him, considering if he's otherwise healthy and it's consistently low.

I know I'm the same way. My WBC count is "low" by human standards. When I was sick, it was elevated into the "normal" range.

Just something to think about.

Dec. 31, 2010, 07:09 PM
That's another thing my vet metioned -- that it may just be normal for him. I have to think that if there were an internal abscess going on for this long, I would have noticed something by now.

Dec. 31, 2010, 08:41 PM
When my TB had a low white count, it was because he was battling a chronic infection (3 years with mud fever), his white counts were anywhere from 3-4 on average. Not alarmingly low, but vet figured it was because of the chronic mud fever. I havent repeated it yet, its been a year since he is mud fever free (thank GOD!), but I should - just to see if it has come up to normal range, or if that WAS his normal range.

Dec. 31, 2010, 08:54 PM
Warmbloods often have WBC counts that are a bit lower than the reference ranges. If he's otherwise healthy (warmblood or not)- I wouldn't worry. The mid-to-upper 4,000s don't bother me.

Dec. 31, 2010, 09:46 PM
I didn't know that about warmbloods. He is 3/4 TB 1/4 Percheron.

As for the counts in the 3s last June, I suspect it had something to do with the ulcers (both reds and whites were down) since counts went up after treatment. If this is his normal level I a fine with it, as long as he feels well.

Dec. 31, 2010, 10:52 PM
Drafts almost ALWAYS have "low" white blood counts, Every time I have a blood panel done on one of my Clydesdales, the vet always comes back and tells me he or she is anemic. It is actually normal for them. Also, drafts are lightweights when it comes to tranqs, so keep that in mind if you need to tranq your horse. Don't go by weight alone...do a horse size dose and see what happens first. This may not be an issue with one that 1/4 draft but better safe than sorry.

Jan. 1, 2011, 11:08 AM
I'd investigate tick-borne disease too. We don't have a lot of this Colorado but we do have it.

Jan. 1, 2011, 11:18 AM
agree with others saying it might be his cold blood side. Drafts trend low, there are also age related differences ( I would have to look in my refernce book for those.)

All bell curves have someone on the low side of normal. You might compare a blood sample drawn during exertion.

I would not concern myself if this is the only symptomology

Jan. 1, 2011, 01:36 PM
if by smz you mean sulfamethoxazole (do you?) then that drug has a major side effect of lowering white blood cell count.

viruses can do it as well...but i don't know what "chronic" viruses horses can have...?

Jan. 1, 2011, 01:50 PM
if by smz you mean sulfamethoxazole (do you?) then that drug has a major side effect of lowering white blood cell count.

viruses can do it as well...but i don't know what "chronic" viruses horses can have...?

Yes, SMZ = trimethoprim-sulfamethoxazole. How does this lower WBC count? I would assume it would kill bacteria and the body then would reduce production of WBCs. At any rate, he had only a short course back in June so it's not really a factor at this point.

Regarding ticks, I'm not inclined to get excited about a tick-borne disease but I'll ask my vet about it. I've seen two ticks since moving to Colorado in 1995. We are high and dry here and we just don't see them.

My horse is probably laughing about all this worry and money spent on him. He's as strong and healthy as I could hope for -- his favorite hobby is tearing around the pasture. He considers it a reward f I take him out on a trail and let him gallop a few miles, preferably uphill.

Jan. 1, 2011, 01:51 PM
Maybe that's just his range. Not every parameter fits nicely on the tall part of the bell curve. :)

If an antibiotic has a side effect of reducing WBCs, that is not because of its intended bacteria-killing effect, it's separate and unrelated. A true *side* effect. Still, if the white count was low prior to treating him with the antibiotic, I wouldn't think that would be relevant.

Jan. 2, 2011, 02:29 PM
THe SMZ really only stands for sulfamethoxazole. If you have sulfamethoxazole/trimethoprim then it is SMZ/TMP as the whole name. Each component has it's own side effects/issues so it's important to be clear that the hose is getting both (the combination med).

Sulfa drugs can cause neutropenia (low white blood cell count) by a kind of complicated mechanism. So, SMZ/TMP works by preventing bacteria from using folate. So, some people think that it can worsen pre-existing folate deficiency in humans and cause neutropenia and anemia by that mechanism. That's one idea :) There are lots of other proposed mechanisms. Some think it is a hypersensitivity (allergy) type effect. Others have suggested it is just a direct effect of SMZ/TMP on the bone marrow supressing its action. The bottom line is no one knows for sure - but it is a very common side effect. In sensitive patients - resolution of the side effect can take weeks to months! So even though your horse had a short course in June - it IS possible (though would be unusual for sure) that his counts are still affected from it.

Up to your vet for sure, but if you are wanting to use antibiotics to treat a possible infection now - usually in humans we would avoid SMZ/TMP in a patient with known neutropenia due to concerns of worsening it. So, your vet might want to consider a different antibiotic in the time being - just to be cautious.

A bone marrow aspirate will definitely help tell what is going on in there and separate "naturally low" from "real medical problem"

May. 12, 2012, 08:27 PM
I realize this is an old thread, but I just came across it looking for answers to the very same question for my TB. Had been noticing frequent urination in small amounts, didn't really think much of it as he is not a big drinker, pulled a cbc just to get a baseline and found low wbc 3.3 Had we not pulled a cbc you would have no idea his counts were low. Shows no signs of being ill at all. Just curious if you found any answers or what the end results were.

May. 12, 2012, 10:23 PM
Copper deficiency.

May. 13, 2012, 01:53 AM
Nothing ever came of it. The WBC count never went back up, so I decided to stop spending money testing it and am operating under the assumption that he is just normally low.

The wee-wee problem resolved with the ulcer treatment and has never returned. Though we didn't scope him, ulcers made sense because he had been boarded away from home for two months and was very unhappy with the confinement.

The horse is better than ever and healthy as can be. I just make sure to give him omeprazole as a preventive when he has to stay away from home overnight.

I've heard of other horses having frequent urination as a symptom of ulcers, so you might consider a course of omeprazole to see if it helps (reference the myriad "blue pop rocks" threads for an economical alternative).

Don't know anything about the copper deficiency but am reasonably certain it was not a factor with my horse.

May. 13, 2012, 09:16 AM
Thank you, We did get his counts back up with stem cell injections, but 4 weeks later when we tested again they were right back down. Might try the ulcer treatments and see what happens with that, but not looking to spend a fortune looking for something that may not be there since he shows no other signs.

May. 13, 2012, 09:20 AM
It may be his normal, especially if he has been acting fine for a while now.

In general for OP and all, I did want to add that it is so valuable to have a baseline panel done on your horse when he is completely healthy, especially an older horse. I usually do mine yearly only because he is older, but it proved so valuable with his recent eye problem, as his once perfect panel came back as abnormal bloodwork - counts were off, anemic, proteins high, pointed us to infection, and when it went BACK perfect again after doxy, it helped us rule out a fear of cancer, and eliminated us from doing more exploratory lancing, U/S, etc. When you have the time, get a baseline to keep on file.

May. 13, 2012, 02:31 PM
Kicking myself for not doing one at the pre-purchase. Normally I would, but ran into an issue that side tracked me and forgot to come back to it. The cbc we pulled when we found the low wbc was pulled for no other reason than to have a baseline which went out the window with the results. They are telling me that at 3.3 for wbc and lymphocytes at 231 (range is 1500 - 7700) that it can not be normal. This is the lowest the lymphocytes and wbc have ever been and this was after the stem cell injections so I'm not too sure about those. (they had been running in the 1400s for lymph and 4.3 for wbc). Then when all the other counts were w/in range (after giving stem cell) his platelets were low. We have not been working him other than short rides a couple times a week and are doing a follow up cbc next week. I'm beginning to think maybe he had/has a virus that just needs to run it's course and let his body naturally take care of things, unless he starts showing other signs of illness. We have been tracking his counts now since March and there has been no change in him other than the results. Still appears to be a happy healthy horse. I am getting a second opinion from another vet and will go from there. Not that I don't completely trust my vet, but he is at a loss even after talking with vet schools. Thank you all for the input and please feel free to keep the ideas coming.

Jul. 11, 2012, 04:21 PM
I came across this while searching for answers to my 12 yr old TWH chronically low RBC and WBC. A few years back a vet targeted ulcers as a sourcef the problem and there was a marked improvement after treating with omeprozale. After, I switched to an ulcer product from Progressive Nutrition which has worked well and is more cost effective for me. I also have kept him on an iron and copper vitamin to keep him in the low normal range for the RBC. I should also mention the poor guy is a stage 3 of 5 on a neurologic scale, which is due mainly (they think) to tissue damage in his neck and arthritis, as well as nerve damage suffered from a bad bout of EPM. I still can go on nice slow rides with him which he loves on his good days. Four weeks ago I checked his bloodwork and his RBC was at 1.4... yeah. I now have him on EPIC to boost his immune system, but he shows no symptoms of being sick. He has pretty bad arthritis in his stifle that I started getting injected a couple years ago, but am holding off for now because of the steroid effect with all of this. He has only ever been a trail horse. Thoughts anyone? Of course he's the sweetest thing.