Goat parasite control requires more than cattle protocols

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Goat parasite control requires more than cattle protocols

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Jun 01, 2006

With the increasing numbers of meat goats in the United States, many bovine practitioners face questions about goat healthcare targeted toward internal parasite treatment and control.

Applying control programs used for cattle to goats will not work. Cattle do get clinical diseases from internal parasites, particularly from Ostertagia sp. infestations. Parasite control in cattle is usually performed for economic returns due to increased calf gains, and there are no problems with cattle parasites being resistant to anthelmintics. By contrast, internal parasites in goats can be a life-threatening condition, and anthelmintic resistance is widespread. This makes the control of parasites in goats essential, yet more complicated. Goat producers usually want veterinarians to give them a deworming schedule including how often to deworm and with what product. They also would like this schedule to work every year in all situations. Unfortunately, this is impossible due to anthelmintic resistance problems. Veterinarians need to urge goat producers to get away from anthelmintic use, and move toward management of pastures and better culling practices. Veterinarians should not give producers advice about parasite control without knowledge of the farm environment and management. This requires physically visiting the farm and performing diagnostic tests.

Although sheep and goats get numerous types of parasites, Haemonchus contortus is the most clinically significant nematode parasite and most important with respect to anthelmintic resistance. The following control recommendations are for Haemonchus, a voracious bloodsucker that can cause severe anemia. If goats are showing clinical signs of parasitism (weight loss, diarrhea and/or bottle jaw) but are not significantly anemic, other parasite species should be suspected and diagnostic tests performed to determine which parasite species is the major problem.

Diagnostics

To make treatment and control recommendations, it is essential to know what dewormers are effective on a farm and to what degree. There are two ways to determine this. The first requires performing quantitative fecal exams. Eggs per gram (EPG) of feces should be calculated on fecal samples taken before deworming then repeated in seven days to 10 days after deworming. Dewormers that do not decrease the EPG by at least 90 percent are considered ineffective. However, the actual effectiveness percentage should be recorded for all dewormers tested because even those partially effective might still be used in some situations.

The second method of resistance determination is a test offered through the University of Georgia's parasitology lab. Resistance patterns to all dewormers can be determined with one test, which is less expensive than running multiple fecals for several dewormers as previously described.

Control programs

Parasitism in goats is not an anthelmintic deficiency; it is a pasture problem. A common saying is "permanent pasture perpetuates parasitism". Even if stocking rates are suitable for proper forage, if goats are allowed to graze an entire pasture without rotation, deadly infestations of Haemonchus can result. Haemonchus is prolific egg producer and has a relatively short prepatent period. It also is more heat tolerant than Ostertagia. This leads to rapid buildup of contamination, especially in summer, when the prepatent period is shorter. There is also a periparturient rise in EPG, which necessitates some special considerations around parturition. The heat tolerance of Haemonchus combined with mild winters make haemonchosis a problem year round in some parts of the country.

Strategic deworming

Strategic deworming programs were developed for Ostertagia problems in cattle and are of limited use with Haemonchus infestations in small ruminants. Strategic deworming requires deworming when most of the parasites are in animal and not in environment (winter for Haemonchus). However, this is difficult in areas with mild winters because some larva survive the season. One type of strategic deworming program for goats is to deworm does three weeks before the first kid is due and repeat every three to four weeks until the last kid born is three weeks old. This should minimize problems associated with the periparturient rise in parasite egg output that occurs around this time.

Salvage deworming

The FAMACHA method is the most common salvage deworming program currently being recommended but should only be used for Haemonchus infestations. This program is designed to slow development of anthelmintic resistance by selective treatment and increased refugia of susceptible parasites, which increases the number of sensitive genes in the gene pool and dilutes the number of resistant genes in the parasites. It also selects animals that are genetically resistant to parasites.