Moderator:
DrO
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Posted on Monday, Nov 17, 2008 - 8:07 am:
Just when you think MRLS is history, think again. Multiple smaller outbreaks occurred in 2006 so caterpillar vigilance still recommended on horse farms. An interesting aspect of this report is that it treats the irritating hair theory as having other competitors, something I have not seen recently. I thought the hairs of the caterpillar had pretty much been established as the cause.
DrO
Vet Pathol. 2008 Sep;45(5):710-22.
REVIEW paper: mare reproductive loss synDrOme.
Sebastian MM, Bernard WV, Riddle TW, Latimer CR, Fitzgerald TD, Harrison LR.
Institute of Comparative Medicine, BB1810, Columbia University, 650 W 168th Street, New York, NY 31793 (USA).
An epidemic of early fetal loss (EFL), late fetal loss (LFL), fibrinous pericarditis, and unilateral uveitis which occurred during the spring of 2001, are together now known as the mare reproductive loss synDrOme (MRLS). A similar epidemic with less intensity was reported during the same period of time from southern Ohio, West Virginia, and Tennessee. The same synDrOme with lesser intensity recurred in 2002. The estimated economic loss from the synDrOme in 2001 and 2002 together was approximately $500 million. Both EFL and LFL were characterized by the absence of specific clinical signs in aborting mares. Nonhemolytic Streptococcus spp. and Actinobacillus spp. accounted for 65% of the organisms isolated from fetuses submitted for a postmortem during the MRLS period in 2001 and 2002. The pathologic findings in fetoplacental units of LFL included bronchopneumonia and funisitis, and there were no findings in EFL. Epidemiologic studies conducted in 2001 suggested an association between the presences of eastern tent caterpillars (ETC) in pastures with MRLS. Experimental studies in pregnant mares by exposure to ETC, or administration by stomach tube or with feed material, reproduced EFL and LFL. Similar experimental studies in mouse, rats, and goats with ETC were unsuccessful. Currently, 2 hypotheses are proposed for MRLS. One hypothesis proposes that an ETC-related toxin with secondary opportunistic bacterial invasion of the fetus leads to MRLS. The second hypothesis suggests that a breach of gastrointestinal mucosal integrity by hairs of ETC leads to a bacteremia and results in MRLS. In 2004, a similar equine abortion storm was reported from Australia and caterpillar exposure was identified as a risk factor for the abortion. In 2006, the synDrOme was observed in Florida and New Jersey.
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