Endurance.Net Ridecamp Archives

Since I'd posted today about Rascal's progress , 10 months post epm, we got 
this today, on the newest research notes on EPM.Thought I'd pass it on.  
Laurie/Rascal/Honey and Scout



      Dr Furr gave his talk on EPM last night and I hope I can understand 
my scribbled notes well enough so that this information does not become 
distorted before it gets to your eyes!! Many of the"veteran EPM moms and 
dads" already know alot of what follows but for those that are new-- here is 
a summary of what was said :  (excuse any mixup I may have made on 
scientific terminolgy)
 EPM is disease of neuro system resulting in wide variety of neurological 
abnormalities caused by unicellular parasite (S. neurona and sometimes  
neospora hugesi is found in horses with EPM).  Lives in the lining of the 
bowel of the opposum, sporocysts are shed in possum feces which are then 
eaten by intermediate host(which can be many- well documented intermediate 
hosts are 9 banded armidillo, skunk, raccoon and possibly cat-with jury out 
on cat and said Dr McKay says that perhaps anything that eats it has 
possibility of becoming intermediate host). After being ingested by 
intermediate host it is absorbed into bloodstream and travels to tissues and 
forms sarcocysts in skeletal muscles where it remains dormant until death of 
intermediate host. The sarcosysts do NOT cause the death of intermediate 
host and it is important to remember that it remains completely dormant in 
intermediate host until the animal is dead. When opposum eats the dead 
muscle tissue of infected intermediate host it then sheds sporocysts which 
are consumed by horses

After sporocysts are ingested by horses it is absorbed through bowel into 
blood stream. Blood flows to every part of  body and horses' bodies are 
adept at ridding it in muscle but not so efficient of ridding it once in 
central nervous system.
It divides and expands inside neurons causing inflammation in nerve nerve 
cell which leads to swelling and possible nerve cell death or necrosis of 
spinal cord which result in neuro deficits. Clinical signs are wholy 
dependent on where in central nervous system organism "lands".
  The disease has widespread exposure of 40 to 60% in horses in North and 
South America. It has never been found in native horses outside the Americas 
that have NEVER lived in the Americas.  Dr Furr did state one vet in France 
thinks he may have seen one case but it has never been proven.
 All breeds are affected with ponies being rarely affected. Most common age 
is 4 to 5 years of age but any age can be affected- it could be that age 4-5 
is more noticable because of start of serious training, etc. Cases conform 
to range of opposum- not as common in Canada and AZ. Very heavy in FL and 
heavy in eastern seaboard. Further north you travel- less prevalent.
 Any neurological sign  can present-- most typical being ataxia, 
asymetrical deficits, abnormal leg placemement,  muscle wasting. A bit not 
as common are abnormal swallowing, head tilt, head pressing, etc and rarer 
are seizures, blindness, etc.
 The disease usually progresses slowly over weeks but acute cases do exist 
with exception being long term muscle atrophy(nerve to muscle dies).
 Diagnostic criteria are not easy-can't be 100% sure in live horse. Only 
post mortem examination can defintiely provide 100%.
Diagnosis based on:
1)consistant clinical signs which show neurological disease
2)cerebral spinal fluid analysis-Western Blot
3)exclusion of other neuro disorders-neck xrays to rule out cervical 
vertebral disorders, testing for encephalitis, WN, herpes and checling of 
serum VIT E levels

CSF is collected from lumbar-sacral junction checking for antibodies of s 
neurona. As few as 8 red blood cells(RBCs) in one micro liter of CSFcan 
contaminate tap resulting in false positive. Consequently less than 10 RBCs 
per microliter are considered relatively clean , and over 50 RBCs per 
microliter of CSF result in a tap which is meaningless. In between 10 and 50 
is questionable.
TREATMENT-
Dr Furr's treament of choice is ponazuril-marquis(Bayer). It is given for 
28days at 5mg/kg BW. In studies after 28 days treatment at that dosage, 
treatment was stopped no matter how much improvement was seen and all horses 
were evaluated 90 post treatment. 60-70%(actually closer to 69%) of all 
horses in study showed improvement. There is essentually NO toxicity with 
marquis- it is as safe as you can get. Way back in time organism was related 
to blue green algae and S.n retains chlorophyll receptors. Ponazuril which 
was developed in 50's as herbicide shuts down chlorophyll receptors, hence 
killing organism. People and horses have no chlorophyll receptors so 
ponazuril has no place to bind hence it is completely safe for 
horses-pregnant mares and breeding stallions included. The actual killing of 
tha parasite is based on time-therefore extended treatment time would be 
more effective than increasing dosage. Some horses need to be treated 2 
months. Adding 2 ounces of corn oil increases blood levels 25% so Dr Furr 
recommends supplememting with corn oil to increase absorption into blood 
stream.
      Sulfadiazine pyrimethamine needs minimum of 4 to 6 mos of dosing with 
preferable minimum of 6 to 7 months dosing. Side affects that might occur 
are anemia, diarrhea. Fetal abnormailites and abortion can occur.
  Nitazoxanide-NTZ(Navigator) is an antimicrobial, antiparasitic drug. 
Success rates are a bit higher but there is element of toxicity. Fever, of 
102, 103, even 104, diarrhea, off feed etc sometimes occur during first 
week.  Dosing is 22.72 mg/lb BW and manufacturer is now suggesting dosing 
with half that amount for first five days(11.36 mg/lb for days 1 thru 5 and 
then 22.72 mg/lb for days 6 thru 28) This seems to help with toxicity. It is 
imperative that directions be followed to the letter. Death can occur from 
overdosing.   It may be a logical alternative for relapse cases or when 
other drugs do not work.
    Diclazuril (Scherring) is very similar to ponazuril and will be 
approved shortly and cost will be similar to marquis. Success rates are 
similar as well.
  DMSO, NSAIDs(bute/banamine) are good for treatment crisis which sometimes 
appear 5-7 days after start of treatment. Some give NSAIDs routinely to fend 
off treatment crisis.
 Around 70% of affected horses willimprove and about 1/3 of those 70% will 
return to 100% normal whereas many of others will return to useful state but 
maybe not back to 100%.
  To help prevent-- do NOT feed off of ground, keep feed locked up. Un of 
Fl has a test area in Gainsville("swimming in opposums") and all horses sero 
convert within 2 wks once put into that area-- but by running electric fence 
10 inches off ground sero conversion was slowed dramatically.  Dr Furr also 
showed picture of  "opposum heaven"-- grass clearing surrounded by thick 
brush-said opposums travel out 75 to 100 yards from brush at night, do their 
thing and then head back into thick brush and said although not always 
practical to keep pasture fences away from thick brush and woods.  It is 
believed that about 1/4 of opposums carry this.
 This was news to me-- but in Dr Furr's words-- "as we speak" EPM vaccine 
is part of challenge studies at Ohio State under Bill Saville. OSU has been 
able to produce EPM in horses in controlled setting and vaccinated horses 
are now being challenged. Within a few months  we will know for sure if 
vaccine is effective and it will either be marketed or pulled from the 
market . He says Fort Dodge has been very accommodating and has worked very 
hard to get to this end. Dr Furr explained the conditional vs full 
licensure-saying 48 of 50 states have approved conditionally . Vaccine is 
proven safe and has reasonable expectancy of efficacy(as opposed to say 
sterile water which is safe but no expectancy of efficacy).
  Marquis kills but takes time-a time dependent effect-increasing treatment 
duration is more effective than increasing dosage amount.
 He said 40% of us(people) have toxiplasm(????don't know what that is or 
how to spell it??) in our brains-- just sitting there quietly. An 
immunesuppressive event or getting ill can set it off and similar thing is 
with EPM and horses. It "can sit" in horses for a long time and later 
activate in 1 1/2 % of horses.
   Dr Furr explained neural plasticity where nerves can "learn" functions 
of other nerves. Said this is age dependent-- meaning younger horses have 
greater ability to retrain nerves.

Dede
http://hometown.aol.com/hueybre/dedemaloney.html

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There are 2 ways to win at this sport. You take a horse and race him for a
short time and then find a new horse or you can take one horse , do the
homework and spend many miles and years enjoying that horse.
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