THE TELOSPORASIDA AND THE COCCIDIA PROPER 



189 



COCCIDiOSIS IN SHEEP AND GOATS 



Coccidiosis in sheep is primarily a 

 disease of feedlot lambs. It has been 

 studied by Newsom and Cross (1931), 

 Deem and Thorp (1939, 1940) and Chris- 

 tensen (1940) among others. It appears 

 12 days to 3 weeks after the lambs arrive 

 in the feedlot. Diarrhea, depression and 

 inappetance appear, followed by weakness 

 and loss of weight. The diarrhea continues 

 for several days up to about 2 weeks, and 

 some lambs may die during this period. 

 Most, however, recover. The mortality 

 varies, but is seldom more than 10%. In 

 a group of 16, 000 New Mexico feeder 

 lambs studied by Christensen (1940) on a 

 Nebraska feedlot, the mortality was 3.4%, 

 but another 9. 8% of scouring, emaciated 

 lambs were removed to a hospital lot for 

 special diet and care. 



Even if there are no deaths, there 

 may be loss of weight or reduced weight 

 gains. Thus, Shumard (1957) found that 

 80 lambs experimentally infected with a 

 sublethal mixture of coccidian oocysts 

 (mostly E. nlnakohlyakimovae and£. 

 arloingi) lost an average of 0.205 pounds 

 per pound of feed consumed during the 24 

 days following infection, as compared 

 with an average gain of 0. 062 pounds per 

 pound of feed consumed for 40 control, 

 uninfected lambs. 



When lambs are brought into the feed- 

 lot, they are usually shedding small num- 

 bers of coccidian oocysts. As the result 

 of crowding, and under conditions which 

 promote fecal contamination of the feed, 

 the coccidial infections build up. The 

 number of oocysts in the feces rises for 

 about a month, remains stationary for 1 

 to 3 weeks and then decreases rather 

 rapidly, only a few oocysts being present 

 at the end of the feeding period. Whether 

 or not disease will appear depends upon 

 the number and species of oocysts which 

 the lambs ingest during the crucial first 

 week or two. By the end of the first 

 month, there is little danger of coccidio- 

 sis. The lambs have been infected, but 

 the exposing dose of oocysts has been 

 small enough to permit immunity to de- 

 velop. In other words, there has been 

 coccidiasis but no coccidiosis. 



Feeding of chopped feed in open troughs 

 low enough to be contaminated with feces 

 promotes coccidiosis. Christensen (1941a) 

 found that corn silage provided an amount 

 of moisture which favored oocyst sporula- 

 tion, while chopped alfalfa, grain and mo- 

 lasses also permitted sporulation. 



Dunlap, Hawkins and Nelson (1949) 

 followed oocyst production from the time 

 of birth in lambs running with their mothers. 

 The ewes were the source of infection, and 

 lambs became infected by ingesting sporu- 

 lated oocysts from the bedding. The first 

 oocysts appeared when the lambs were 5 to 

 8 weeks old; they built up to a peak which 

 lasted 1 to 4 weeks, and then declined. 



Temperature affects oocyst sporula- 

 tion. Dunlap, Hawkins and Nelson (1949) 

 found the first sporulated oocysts in the 

 bedding when the mean temperature was 

 49° F. Christensen (1939) found that the 

 optimum sporulation temperature for the 

 oocysts of E. arloingi was 20-25° C, the 

 sporulation time being 2 to 3 days at that 

 temperature in a thin layer of water or in 

 fecal pellets. The oocysts survived less 

 than 4 months in fecal sediment at this 

 temperature. Sporulation was slow at 

 to 5° C, altho oocysts remained alive for 

 at least 10 months in fecal sediment or 

 moist pellets. No sporulation took place 

 at 40° C and the oocysts were killed within 

 4 days. If the fecal sediment was allowed 

 to putrefy, however, no sporulation took 

 place at any temperature. 



Landers (1953) found that the oocysts 

 of E. arloi)igi, E. ninakohlyakiniovae and 

 E. parva did not survive 24 hours in sheep 

 pellets when frozen directly to -30° C, and 

 survived less than 2 days when conditioned 

 at -19° C prior to freezing to -30°. They 

 survived without essential mortality when 

 frozen directly to -25° C for 7 days, but 

 only about half of the first two species and 

 one quarter of E. parva survived 14 days. 

 Repeated freezing and thawing at -19 or 

 -25° C up to 6 or 7 times had no significant 

 effect on survival. Landers said that in an 

 average winter at Laramie, Wyoming the 

 minimum soil surface temperature would 

 probably be between -15 and -20° C and 

 that unsporulated oocysts would not nor- 

 mally be killed by such temperatures. 



