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Equine Protozoal Myeloencephalitis (view source)
Revision as of 12:23, 20 July 2010
, 12:23, 20 July 2010→Treatment
==Treatment==
==Treatment==
===Antiprotozoals===
The Food and Drug Administration has approved four treatments for use in horses, but not all of these are commercially available:(IVIS 4)
*'''Sulfadiazine and pyrimethamine combination, 'Re-Balance'''': administered PO daily for a minimum of 90 days. Due to availability and ease of administration, some use an off-label regimen of trimethoprimsulfa tablets with pyrimethamine tablets. ''Mode of action'': trimethoprim, sulfadiazine, and pyrimethamine all inhibit enzymes of folic acid synthesis. ''Efficacy'': 61.5% improvement by one clinical grade.(98 in furr)''Potential adverse effects'': bone marrow suppression (mild anaemia, leucopenia, neutropenia, thrombocytopenia), fever, anorexia, depression, acute worsening of ataxiam altered reproductive performance in stallions (19 in IVIS 4), congenital defects(20 in IVIS 4) and abortion. Folic acid deficiency may also cause gastrointestinal disturbances such as glossitis.(18 in IVIS 4) Blood dyscrazias are typically self-limiting and resolve on withdrawal of treatment. (Furr)
Ponazuril (Marquis, Bayer Animal Health) - 1st FDA-approved drug for EPM, well absorbed PO, achieves steady state therapeutic concentration in 3days in CSF of horses (100 in Furr). In filed efficacy study improvement bny at least one clincal gradein 60%, 8% relase after 90days of stopping treatment (91 in Furr), resposne wihtin 10days. V safe, no sstemci toxicity even at high doses (101 in Furr), use in pregannt animals is off-label, feeding corn oil immediately prior to admin may enahcne absrobption of durg (103 in Furr)
Ponazuril is a triazinetrione antiprotozoal drug that targets the “apicoplast” organelle and inhibits energy metabolism (respiratory chains). The label dosage regimen PO daily for 28 days. A multi-center field study - no adverse effects were noted. However, information provided by the manufacturer reports “unusual daily observations” in eight animals that may have been related to treatment including blisters on nose and mouth, skin rash or hives, loose stools, mild colic, and a seizure.(IVIS 4)
Protocols involving intermittent administration of ponazuril may have application in prevention of EPM. (Mackay, R.J, Tanhauser, S.T, Gillis, K.D, Mayhew, I.G, Kennedy, T.J (2008) Effect of intermittent oral administration of ponazuril on experimental Sarcocystis neurona infection of horses. Am J Vet Res, 69(3):396-402.
Treatment with ponazuril minimizes, but does not eliminate, infection and clinical signs of EPM in horses. (Furr, M, McKenzie, H, Saville, W.J, Dubey, J.P, Reed, S.M, Davis, W (2006) Prophylactic administration of ponazuril reduces clinical signs and delays seroconversion in horses challenged with Sarcocystis neurona. J Parasitol, 92(3):637-43.
Diclazuril po, SID, chemically similar to ponazuril, one study imorvment in 58% cases if gven for 28days (98 in Furr), approved by FDA for use as top-dress tablet but not comemrically avialable, no adverse effects in effciacy study.(Furr)
Diclazuril is a triazinetrione antiprotozoal agent similar to ponazuril with an unknown (but possibly similar) mechanism of action. A multi-center clinical field study was performed. Reported adverse reactions were not clearly linked to drug administration and included worsening neurologic status and laminitis. Results of efficacy studies were surprisingly similar for each of the four approved therapies when similar methodologies and means of assessing improvement were used. Regardless of drug, _60% of treated horses improved by at least one neurologic grade or became negative on CSF WB. Based on reported side effects, ponazuril and diclazuril seem to have the fewest reported adverse effects. (IVIS 4)
NTZ (Navigator, Idexx Pharmaceuticals) member of 5-notrothiazol class of antimicrobials ad currently approved for tx of EPM, succes rate of about 60% in FDA-regulated study (98 in Furr). Adverse effects and death at high doses (98),, diarrhoea, depressiona and lamninits recorded at lower doses. {Poor completion rate and study compliance sugegts unreproted toxicity. Toxci signs usally resolve oin withdrawl of tx, no longer availbale in US.
Even successfully treaed cases may remian immunoblot positive for long periods so trying ot treat unitl seronegatvie not relasiitc. Triaxine based rugs (ponazuril, diclazruil, NTZ) licensed to be used oinly for 28days. Longer tx often needed as determined by repeat exam after 1mth. No reposnee sugegsts misdx and case should be re-evaluated. If some resposne bt rmeiansabnromal, continue tx for another mth.(Furr)
Paste no longer commercially available. This drug is a 5-nitrothiazole antiparasitic drug that inhibits the pyruvate:ferredoxin oxidoreductase (PFOR) enzymedependent electron transfer reaction essential for anaerobic energy metabolism. Reported side effects in these studies included inappetence and depression.
Two field studies for efficacy and safety were conducted during the approval process for nitazoxanide.
The most common adverse reactions were fever, anorexia/reduced appetite, and lethargy/depression.
Following warning: “administration of nitazoxanide can disrupt the normal microbial flora of the gastrointestinal tract leading to enterocolitis. Deaths due to enterocolitis have been observed while administering the recommended dose in field studies.”a(IVIS 4)
===Ancillary medication===
===Ancillary medication===
*'''NSAIDs''': DMSO IV as 10% solution, thought to reduce CSF pressure and improve clinical status. Recommended for severe cases of EPM or to avoid worsening inflammation that may be induced by parasite kill(Furr). Caution: DMSO may cause intravascular haemolysis(Pasq).
*'''NSAIDs''': DMSO IV as 10% solution, thought to reduce CSF pressure and improve clinical status. Recommended for severe cases of EPM or to avoid worsening inflammation that may be induced by parasite kill(Furr). Caution: DMSO may cause intravascular haemolysis(Pasq).