Small ruminant parasite control (Proceedings)


Small ruminant parasite control (Proceedings)

Nov 01, 2010

The most common reason for anemia in the small ruminant is internal parasitism. Hemonchus contortus (the barber pole worm) is a voracious bloodsucker that typically resides in the abomasum. The condition may occur in both young stock and adults alike. With the ever increasing issue of parasite resistance, practitioners will be faced with the severely anemic small ruminant. Providing that there are no other serious disease conditions, these cases can have successful outcomes.

The clinically parasitized individual

The case presentation is quite typical. The animal is weak and often down. Mucous membranes are pale pink to white. The mucous membranes of the eye provide the most consistent coloring although mucous membranes of the oral cavity and vagina may also be examined. The heart and respiratory rates are usually elevated. Diarrhea may or may not be present. Often times, there is a history of deworming, even recent deworming.

If the client is bringing the animal into your clinic and it is coming as a probable anemia, the client should bring a healthy blood donor. Have the client make sure that the donor's mucous membranes are bright pink to red. It is important to not stress or excite the patient in that this could lead to collapse and possibly death due to anoxia. Most cases, that we have dealt with in Tennessee, are too weak to get excessively stressed. A pack cell volume (PCV), total protein (TP), and fecal floatation help to confirm the diagnosis of anemia due to internal parasitism. A blood transfusion is the treatment of choice if the PCV is 10 or less. The lowest PCV seen by the author at least a couple of times was 4. These cases were transfused successfully and sent home. Animals' PCVs as low as 9 or 10 can recover without blood transfusions if treated with effective anthelmintics but blood transfusions help ensure recovery and recovery will be faster. An animal with a PCV of 11-15 may benefit from a transfusion but this is not always necessary for a successful outcome. The TP is usually low as well and fecal floatation should demonstrate numerous parasite eggs. About 50% of the time, the case is complicated by coccidia.

Steps in performing a blood transfusion

     1. Place a temporary jugular catheter in the anemic animal.

     2. Make sure the blood donor is healthy by checking mucous membrane color and running a PCV. The PCV should preferably be above 30 but we have used donors with PCVs between 20 and 30 without incident.

     3. Place a jugular catheter in the donor animal (a needle may be used as well as long as there is good restraint).

     4. Collect blood from the donor; 10-20 ml/kg can be collected from a healthy donor. We typically collect 10-15 ml/kg which equates to 500 to 750 ml from a 50 kg goat. Blood can be collected in sterile IV bags that have had sodium citrate added as an anticoagulant. One hundred ml of a 4% Na citrate solution should be added to a 1 liter bag (extrapolate with smaller bags). The bag should be agitated during collection to prevent clotting.

     5. Transfuse donor blood into patient. Infuse at a slow drip for the first 15 minutes, if no reactions occur, the rest of the volume may be transfused at a rapid drip. Reactions are quite rare in small ruminants during the first transfusion. Reactions will likely become more frequent if subsequent (days to weeks later) transfusions are necessary. Epinephrine is the drug of choice if a reaction occurs. If a serious reaction does occur, blood may be transfused very slowly or another donor should

Post-transfusion, the patient will often be noticeably stronger and will eat. We typically keep the animals overnight and monitor the PCV and TP the next day. You can expect a 5-10 point rise in the PCV....should at least be in the teens. Iron injections are often not necessary but should be considered for animals that repeatedly become anemic over a short time period.

It is also acknowledged that certain parts of the United States have a greater problem with internal parasites other than H. contortus. These cases usually present with ill thrift, diarrhea, bottle jaw, and low serum protein. Blood transfusion is not usually necessary and deworming with an effective anthelmintic is the treatment of choice. However blood transfusions will help to elevate the protein levels and might be considered in special cases. Some of the authors own sheep (dewormed prior to lambing only with ivermectin) developed muzzle edema and bottle jaw. Three older ewes, 2 yearling ewe lambs, and 4 young lambs were placed on a ½ acre lot to allow the primary pasture to grow and be cut for hay. The sheep were on the small pasture for 1.5 months and had eaten the pasture down to about an inch in height. Only the older ewes developed signs of parasitism. The ewes were not anemic but had low total proteins and extreme muzzle edema and bottle jaw. The older ewe were dewormed with moxidectin and signs of edema were gone within 2 days.