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 Christensen (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. ninakohlyakimovae 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 feedlot, they are usually shedding small numbers 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 coccidiosis. The lambs have been infected, but the exposing dose of oocysts has been small enough to permit immunity to develop. 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 sporulation, while chopped alfalfa, grain and molasses 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 sporulated 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 sporulation. 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 0 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. arloingi, E. ninakohlyakimovae 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 normally be killed by such temperatures.
Coccidiosis in sheep and goats can be diagnosed from a combination of history, signs, gross lesions at necropsy and microscopic examination of the intestinal mucosa and feces. However, recognition of coccidia in the lesions at necropsy is necessary for positive diagnosis. The mere presence of oocysts in the feces does not necessarily mean that the disease is due to coccidia. On the other hand, acute coccidiosis may be present before any oocysts appear.
Relatively few studies have been carried out on the treatment of coccidiosis in sheep. A distinction must be made between preventive and curative treatments. Several sulfonamides and sulfur are of value in preventing coccidiosis in lambs, but no drugs are known to cure the disease once signs appear. However, oxytetracycline and related antibiotics may be of value in controlling secondary infections.
Foster, Christensen and Habermann (1941) found that 2 g sulfaguanidine a day prevented the acquisition of natural coccidiosis in 5 lambs and reduced the level of oocyst output in 4 subclinical infections with unnamed species. Christensen and Foster (1943) reported that 0.2% sulfaguanidine in the feed for 20 days beginning 1 day after an infective feeding with 500,000 sporulated oocysts from lambs with clinical coccidiosis prevented severe coccidiosis in lambs, but that 0.45% sulfaguanidine failed to affect the course of the disease when it was begun the day after clinical signs had appeared. Steward (1952) found that sulfamethazine and sulfadiazine had some value in an outbreak of coccidiosis in sheep, reducing the numbers of oocysts passed, but that quinacrine was valueless. Whitten (1953) found in a controlled experiment that neither 0.01 g per kg quinacrine hydrochloride nor 0.01 g per kg sulfamethazine daily for 3 days had any significant effect on oocyst production or weight gains in naturally affected lambs. However, oocyst production decreased markedly markedly in both ireated lambs and controls following treatment, so that if no controls had been used, it would have been assumed that the treatment had been of value.
Christensen (1944) found that 0.5 to 1.5% sulfur fed in a ration of chopped alfalfa and ground corn held together by molasses and water prevented coccidiosis in feeder lambs. He fed this amount of sulfur for 72 days without ill effects, but higher concentrations caused diarrhea and decreased weight gains.
Tarlatzis, Panetsis and Dragonas (1955) claimed that furacin was effective against coccidiosis in sheep and goats, but their work was uncontrolled.
Good sanitation will largely prevent coccidiosis in lambs. Coccidiosis is not a problem in suckling lambs on the western range, but appears when the animals are brought together in the feedlot. Feedlots should be kept dry and clean. Clean water and feed should be supplied, and feed troughs should be so constructed that they cannot be contaminated with feces.
Coccidiosis is a potential hazard if lambing takes place in a barn or restricted area, and the bedding is the most common source of infection. Shumard and Eveleth (1956) recommended as a practical method for raising lambs with their ewes that the animals be kept in concrete pens with straw bedding, that the pens be cleaned twice a week, and that 1 pint of a 3.45% sulfaquinoxaline solution be added to each 50 gallons of drinking water. In their studies, coccidian oocysts did not appear in the lambs until 18 days after treatment had been discontinued.