Friday, July 19, 2013

Egg Counts Continue to Increase

When looking at fecal egg count (FEC) data, it is important to separate the data from those goats that were dewormed (two weeks ago) from those that were not treated with an anthelmintic on June 27.

For the untreated goats (n=49), fecal egg counts ranged from 120 to 14,680 and averaged 3,463 + 2,754 epg. The median egg count was 3,114 epg. Two weeks prior, fecal egg counts averaged 1,120 + 1,142 epg. This is a substantial increase in two weeks.

The substantially increasing fecal egg counts are an indication of an increasing parasite problem. However, after a large number of goats were dewormed on July 11 -- and the goats were moved to a clean pasture -- it is expected that fecal egg counts on July 25 will be lower, especially among the treated goats (n=46). It is also expected that fewer goats will require deworming.

For the goats that were treated on June 27 (n=16) , fecal egg counts ranged from 0 to 575 and averaged 158 + 157 epg. The median fecal egg count was 163 epg.  A fecal egg count reduction was calculated for the goats that were dewormed with levamisole (Prohibit @ 3 ml/50 lbs.) on June 27. It ranged from -250.9 to 100 percent and averaged 68.7 + 70.0 percent.  The median reduction was 67 percent.

The only goat whose egg count went up after deworming went from 57 to 200 epg. Because these counts are so low, they aren't really different. If you remove this data from the data set, fecal egg count reduction ranged from 47.7 to 100 and averaged 90.0 + 13.3 percent.  A 90 percent reduction is an indication of a low level of resistance. An effective anthelmintic treatment should reduce fecal egg counts by 95 percent or more.

The low egg counts in the treated goats is an indication that levamisole (Prohibit) is generally an effective treatment for the population of worms that is infecting the goats in this year's test. The first fecal egg count that follows a deworming will not be factored into the test results, as the lower egg count is usually the result of drug treatment, not the genetics of the goat.

Larvae ID
For the pooled fecal sample collected on June 27, Haemonchus contortus (barber pole worm) comprised 77 percent of the worm infection, compared to 82 percent on May 31. Trichostrongylus spp. comprised 17 percent of the worm infection on June 27, compared to 12 percent on May 31. Other worm species accounted for the other 6 percent of the worm larvae.

Haemonchus is a blood-feeding parasite that causes anemia, as evidenced by pale mucous membranes. The diagnostic test for the barber pole worm is a blood test (packed cell volume). A FAMACHA card is used to estimate packed cell volume (PVC) in sheep, goats, and camelids.

The other worms are more likely to cause diarrhea (scours) and further weaken a goat that is carrying a heavy load of barber pole worms. It is harder to determine the cause of diarrhea, but goats that have significant diarrhea are usually dewormed and given treatments for scours. Unfortunately, it is very difficult to obtain a fecal sample from a goat with liquid feces (fecal consistency score of 1).

Download July 11 (d-28) FEC Report