SUMMARY The sensitivity and specificity of various serologic tests for antibodies to Toxoplasma gondii were compared in 1,000 naturally exposed sows, using isolation of viable T gondii as the definitive test. Serum samples obtained from heart blood of 1,000 sows from Iowa were examined for T gondii antibodies by use of the modified agglutination test ( mat ), latex agglutination test ( lat ), indirect hemagglutination test ( ihat ), and elisa . Toxoplasma gondii was isolated from 170 hearts of 1,000 sows by bioassays in mice and cats. The percentage of samples diagnosed as positive for each of the serologic tests was: mat = 22.2% (titer ≥ 1:20), ihat = 6.4% (titer ≥ 1:64), lat = 10.4% (titer ≥ 1: 64), and elisa = 24.1% (OD > 0.360). The sensitivity and specificity of these tests were calculated respectively to be: 82.9 and 90.29% for mat , 29.4 and 98.3% for ihat , 45.9 and 96.9% for lat , and 72.9 and 85.9% for elisa . The dye test was run at 1:20 dilution on only 893 sera because of bacterial contamination and presence of anticomplement substances. Dye test antibodies were found in 17.8% of the sera, and sensitivity and specificity were 54.4 and 90.8%, respectively. Thus, the mat had the highest sensitivity among all serologic tests used.

Hearts of 1,000 pigs killed at an abattoir in Iowa were bioassayed for the prevalence of tissue cysts of Toxoplasma gondii. One hundred grams of cardiac muscle from each pig was homogenized, digested in pepsin solution, and bioassayed in 10 mice. Five hundred grams of heart tissue from each of a subset of 183 pigs was also bioassayed in cats. Serum collected from the heart from each pig was assayed for anti-T. gondii antibodies in the modified agglutination test using formalin-fixed whole tachyzoites. Anti-T. gondii antibodies were found in 22.2% of pigs. Viable T. gondii was isolated from a total of 170 pigs; from 50 hearts by bioassay in mice, from 58 hearts by bioassay in both mice and cats, and from 62 pigs by bioassay in cats only. The success of isolation in cats (65.6%) was approximately twice that in mice (31.7%). Percentage of isolations of T. gondii with respect to reciprocal antibody titers (in parentheses) in pigs was: 3.7% (< 20), 37.1% (20), 38.1% (40), 60% (80), 75% (200), 77% (400), 83% (800), and 75.8% (> or = 2,000 to 16,000).

The hearts of 893 sows from Iowa killed for food between January 1990 and February 1992 were examined for Sarcocystis bradyzoites by the digestion technique. Bradyzoites were found in 163 (18.2%) hearts. Sections of formalin-fixed tissues from 28 hearts with demonstrable bradyzoites were examined for sarcocysts. Sarcocystis miescheriana sarcocysts were found in six pigs. The prevalence of Sarcocystis was apparently not affected by season.

Eighteen calves were orally inoculated with either 200,000 or 225,000 sporocysts of Sarcocystis cruzi. Eight goats were orally inoculated with 20,000 sporocysts of S capracanis. Calves and goats were euthanatized at various times after inoculation, and portions of their right and left biceps femoris, right and left longissimus dorsi, myocardium, and tongue were frozen at -150 C in precooled isopentane and stored at -70 C. Frozen sections of these muscles were stained with hematoxylin and eosin, modified Gomori's trichrome, nonspecific esterase, diphosphopyridine nucleotide tetrazolium reductase, and adenosinetriphosphatase at pH 10.4 and 4.6. Muscle from the same locations was fixed in 10% neutral buffered formalin, processed for paraffin embedding, sectioned, and stained with hematoxylin and eosin. Microscopic examination of both calf and goat tissue indicated that both type I and type II muscle fibers were equally infected and that infected myofibers showed no apparent damage other than displacement by sarcocysts. Occasionally, muscle fibers within the muscle spindles contained sarcocysts.

During the lambing season of 1983/1984, 8 of 44 purebred Hampshire ewes on a farm in Knoxville, Md had reproductive problems. In at least 4 of these ewes, the problem was attributed to toxoplasmosis. Necrosis and Toxoplasma gondii tachyzoites were found in placental specimens from 3 ewes. Agglutinating antibody to T gondii, at a titer of 1:80, was found in pleural fluids of both fetuses aborted from 1 ewe; this ewe had an antibody titer of 1:6,400 at the time of abortion. In another ewe, the diagnosis was confirmed by the isolation of T gondii from the placenta and 1 of her lambs. Of numerous free-roaming adult cats on the farm, 16 were trapped, euthanatized, and examined for T gondii. Agglutination antibody to T gondii, at titers of 1:4 to 1:64, was found in serum samples from all the cats. Toxoplasma gondii was isolated from the brain and skeletal muscles of 9 of the cats, and from the feces of 1 cat. Blood samples obtained from all 78 sheep on the farm 6 months after the episode of abortion were examined for antibody to T gondii. Agglutinating antibody titers to T gondii were less than 1:16 in 46 sheep, 1:16 in 16, 1:64 in 12, 1:256 in 2, 1:024 in 1, and 1:4,096 in 1. Analyses of serologic data in sheep of various age groups suggested that the Toxoplasma infection was acquired sporadically, probably from feed contaminated with oocysts.

Sarcocysts similar to those of Sarcocystis muris were found in mice from the Iowa State University Mouse Genetics Laboratory. Muscle tissue from these mice was fed to 8 cats. Five cats developed an isosporan infection with oocysts most like those of Isospora felis. Sporulated oocysts from cat feces were fed to mice. In about 100 days mice developed sarcocysts that were visible to the unaided eye. Three cats were fed muscle tissue from the experimentally infected mice, and all cats developed an I. felis-like infection. Three cats fed muscle tissue from control mice from the same colony as the experimental mice did not develop isosporan infections. Thus it is demonstrated that this murine Sarcocystis is part of an isosporan life cycle.

Hemiurid trematodes, found in the stomach of Rana boylei from northern California, were identified as Halipegus aspina Ingles, 1936. Morphological differences separate these flukes from Halipegus. Parahalipegus gen. n. is established, with P. aspina (Ingles, 1936) as type species. Ingles (1936) described hemiurid trematodes from the stomach of yellow-legged frogs (Rana boylei Baird) as a new species, Halipegus aspina. Rankin (1944) reviewed the genus Halipegus and referring to H. aspina stated, p. 160, This species certainly belongs near Halipegus, but the characters do not fit those