Parasite Diagnosis
And Treatment Protocol
By Dr. Missi Cooper
Two areas that have new protocols related to parasites in alpacas are how fecal exams are preformed and treatment recommendations. The changes that have been made in how to run a fecal are the result of recent research that shows that alpacas have difficulties with lower parasite loads than other species. Treatment protocols have changed due to the increase in parasite resistance and research information on the length of effectiveness of dewormers especially doramectin or Dectomax.
Traditionally, fecal exams are preformed by mixing feces with a salt solution and allowing the parasite eggs to rise. This is effective when the number of parasites that cause damage is in the 300 to 500 eggs per gram rate. Recent studies from The Ohio State University College of Veterinary Medicine have shown that llamas and alpacas have damage internally at much lower rates of 30 to 50 eggs per gram of fecal matter. For this reason, it is now recommended that these two species fecal exams be run by a modified Stoll's technique. This requires that the feces be centrifuged and use a sugar solution in order to concentrate the parasite eggs, so that smaller numbers can be detected. Unfortunately, not all veterinarians that deal with llamas and alpacas have seen this most recent information and are still running salt flotation fecal exams on these animals. Some results of fecal exams done with the salt flotation will be negative but when run using the modified Stoll's will show a parasite load that requires treatment.
More accurate diagnosis and appropriate treatment are necessary to slow down the progression of parasite resistance. There are several llama farms and numerous small ruminant farms that are known to have parasites that are resistant to both Avermectins (ivermectin and doramectin) and benzimidazoles (fenbendazole or oxybendazole) type dewormers. This leaves few drugs that are effective against the common parasites of llamas and alpacas such as P. tenuis, strongyle type, and trichuris. Recommendations are now to test individual animals and only treat those that need it, compared to before to treat the whole herd two to three times a year regardless of who is having problems. Pease consult with your veterinarian as to what is appropriate for your farm and animals.
Along these same lines are newer treatment protocols for prevention of P. tenuis or the meningeal worm. Initially ivermectin once a month was used year round to prevent migration of this parasite. With the release of Dectomax or doramectin some were using this in replacement for ivermectin every thirty days. Studies done by The Ohio State University several years ago showed that this drug is effective in the body for a longer period of time then ivermectin. Doramectin was proven to be able to kill parasites that were migrating for 28 days after treatment and it usually takes larva about 30 days to migrate to the spinal cord. This means that doramectin should be dosed every 60 days and to use it more frequently is enhancing the development of resistant parasites.
Also to try to reduce the number of parasites that become resistant to dewormers the number of times to treat for preventing meningeal worm infections has been reduced for certain areas and environments. After further analyzing the peak incidence of clinical signs associated with P. tenuis infections and the habits of snails and slugs, it was determined that there is a low risk of exposure during the hot dry summers and the frozen winters so no prevention is necessary. For farms in southeastern Pennsylvania that do not have a lot of standing water or swamps or fields that are in the woods dosing for P. tenuis can be limited to spring and fall. This in combination with using doramectin would reduce the number of dosings to four times a year or twice dosing in the spring sixty days apart and twice dosing in the fall sixty days apart. Reduction in the parasites exposure to the dewormers, from twelve times a year with ivermectin to four times a year, will help to slow down the resistance rate.
Many experts
feel that parasite resistance is a bigger problem then infection with
P. tenuis due to the fact that there will not be a new dewormer available
for about ten years. Since the percentage of animals that develop disease
from strongyle type internal parasites is higher than those that are
infected with P. tenuis, not having an effective dewormer will affect
more animals. As always, please consult with your veterinarian about
what is the best practice for your animals and farm.