Mare Reproductive Loss Syndrome

Term or close-to term abortions:

• Delivery may occur in mares anywhere from 5 weeks premature to past the "due date";
• Red-bag (placenta previa) deliveries are being more commonly seen;
• Foals presented are not dysmature;
• Those foals born alive are seen to be significantly ill - dehydrated and septic;
• Pre-natal pneumonia appears to be present in many cases;
• Edema may be present;
• Reddening of the eye may be present;
• The possibility of facial papillomas may be connected with the condition;
• Bacteria have been isolated from aborted dead term or close-to term foals. Of 247 sampled, 147 showed Streptococcus spp. presence and a significant number showed Actinobacillus presence;
• Streptococcus spp. have also been isolated from aborted 2001 breedings (22 of 49 samples).
• It is not thought that the bacteria presence is the primary cause, but rather a sequela of some other cause;
• Nitrate implication has been ruled out;
• Viral implication has been ruled out;
• Leptospirosis implication has been ruled out;

Early pregnancy loss:

• Associated early pregnancy losses are being observed post day 35 and prior to day 90;
• Although palpation may indicate a normal pregnnacy, embryos viewed by ultrasound that are at risk usually display a cloudiness in the fetal fluids;
• Subsequent examination may identify a dead or aborted fetus;
• These mares will be unlikely to re-enter estrus until 120 days post breeding ovulation owing to normal endometrial cup activity;
• Results of a census indicates that of 159 regional farms, 37 have experienced no early pregnancy losses, whereas 17 have experienced greater than 50% loss. The number of mares considered in foal when checked at 42 days of gestation was approximately 3294 and of these, 2616 were still in foal on May 7 which represents a 79% pregnancy rate;

Mares:

• Some mares have shown sickness themselves, displaying trembling and shaking as outward signs;
• There has been a drop off in aborted foals being presented for analysis the last couple of days, but it is hypothesised that this may be due more to the end of the breeding/foaling season becoming closer, rather than an indication of a reduction of the cause;

Other genders, ages and locations:

• There is some evidence that signs are being seen in ages and genders other than broodmares;
• It is thought that similar signs may be being see in areas north and east of Kentucky - Ohio, Pennsylvania (in the Amish horses), and West Viriginia.
• Unexplained weight loss in yearlings is being seen in Kentucky this year and is thought to be possibly related;
• Increased incidence of pericarditis is being seen. Two combined practices report having seen 20 cases in the last few weeks where they will normally see only a couple each year;

Hypothesizing of cause:

• It is universally agreed that a definitive cause cannot be provided at this stage;
• Mycotoxins are now thought to be unlikely to have been the primary cause (May 23rd, 2001);
• It is now thought possible that there is a link between cyanide or cyanogenic compounds as the causal agent. Wild black cherry trees are the likely source of these toxins. Limited recent observations imply that Eastern Tent Caterpillar may be directly or indirectly involved in the delivery of cyanogenic compounds to horses (May 24th, 2001);

Preventative measures:

• Reducing exposure to pastures and (this years) Kentucky produced hay;
• Pastures may be mowed to remove seed heads and the cuttings should possibly be removed and used only in feed for another species not likely to be susceptible. It must be noted that the mowing of the grasses may result in a drier condition in which mycotoxins are likely to flourish, so this may not be a long-term solution. Additionally if the bluegrass is mowed, animals may turn to other food sources not normally bothered with, including tall fescue grasses which may be endophyte infected;
• Placing pregnant mares on daily Domperidone, Flunixin Meglumine (Banamine^TM), probiotics and Trimethoprim Sulfa drugs may be of assistance and is thought unlikely to cause any problem;
• Regumate use is not suggested as endogenous progesterone levels have not been shown to be reduced;
• Mycotoxin-binding feed additives should be used, which costs about 30 cents per day per horse (yeast cell-wall extract);
• Even though mycotoxins are now thought to be unlikely as the primary cause, it is suggested that keeping animals on the mycotoxin binders may be advisable as there could be other (unknown) associated benefits that assist in reduction of likelihood of stock being affected by the syndrome (May 23rd, 2001);
• These mycotoxin binders are produced by Kentucky-based Alltech and are available through Farmers Feed Mill/Hallway Feeds, Southern States, McCauley's, and Brumfield Feeds.

Other comments:

• Shipping out of Kentucky to attempt to prevent early embryonic loss may not result in a "safe" pregnancy as there is uncertainty as to whether previous cell damage may result in subsequent pregnancy loss;
• Permit requirements for shipping horses from Kentucky to Florida have been implemented by the Florida Dept. of Agriculture;
• It is important if shipping to another State that the veterinarian inspecting for the paperwork contact the destination State to ensure new regulations have not been implemented;
• It is thought that this situation may be a reflection of a repeat of a similar situation that occurred in early 1981, but owing to diagnostics (specifically ultrasound) not being as developed then it is difficult to draw an accurate comparison.