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stimulation of SOD activity by an as yet unknown mechanism. Because we found the difference in reticulocytosis between infected (2.7%) and uninfected mice (0.4%) to be small, and because the SOD activity in the infected mice showed no correlation with the reticulocyte level, the observed differences in SOD activity between the red blood cells from the two groups of mice should not arise from the reticulocytes alone. No variation in SOD level was observed in the young and mature erythrocytes in humans (Michelson, 1977. In Frontiers in physicochemical biology, B. Pullman (ed.). Academic Press, New York, p. 351). Finally, enzyme activity and protein-stained patterns of extracted SOD from red cells of uninfected and infected mice and SOD from isolated parasites appeared identical. The parasite may be able to use this enzyme for combating toxicity of oxygen or oxidant stress during the conversion of ingested hemoglobin (containing heme (Fe II)) to yield hemozoin pigment (containing hemin (Fe III)). Supertimulation of SOD activity by an as yet unnown mechanism. Becaus we found the diference in reticulocyt sis between inf cted .7%) and uninfected mice (0.4%) to be small, d because the SOD activity n he fect d oxide ca arise from the reduction of oxygen bound to hemoglobin during the oxidation of Fe (II) of heme to Fe (III) of hemin (Rotilio et al., 1976. In Superoxide and superoxide dismu ase, J. M. McCord and I. Fridovich (eds.). Academic Press, New York, pp. 239-244). Disulfiram can potentiate oxygen toxicity in rats by interacting with SOD (Forman et al., 1976, J. Pharmacol. Exp. Therapeut. 212: 452-455). Perhaps the antimalarial action of a bioconverted product of disulfiram, diethyldithiocarbamate, on P. falciparum is related to its inhibition of the parasite's SOD activity (Scheibel et al., 1979, Proc. Natl. Acad. Sci. USA 76: 5303-5307). We found that diethyldithiocarbamate at concentration as low as 0.2 mM inhibited the SOD extracted from the isolated P. berghei and also that from infected red blood cells from 20 mice. We thank UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (Project no. 780001) for financial support.

The excretory and secretory antigens from the evaginated scoleces of Taenia ovis were collected for 3 days in vitro, and used in an ELISA test to detect antibodies to T. ovis in the serum of dogs. When tested on sequentially collected sera, diagnostic ELISA values could be detected in many dogs 4 wk after infection, and remained for an average of a further 4 wk after worms were removed from dogs with an anthelmintic. Using an ELISA discriminant value that eliminated all false positives from 70 uninfected laboratory dog sera and from 57 uninfected farm dog sera, 54/62 true positives were found in sera from dogs infected with various numbers of T. ovis for various intervals. Sera from dogs infected with T. hydatigena gave 11/15 false positive reactions, whereas sera from 15 dogs infected with Echinococcus granulosus or 7 dogs infected with T. pisiformis were all negative. For T. ovis the test had a high repeatability, was not greatly influenced by the number of worms carried by the dog and higher titres were correlated with long-standing infections. Approximately 1,000 scoleces could be recovered from each experimentally infected sheep. Using the ELISA test with undiluted antigen and serum diluted 1:40, approximately 10 sera could be tested in duplicate with the excretions and secretions from each T. ovis scolex.

A high level of resistance to oral infection with Echinococcus granulosus eggs was stimulated in lambs by two or more subcutaneous injections of oncospheres given 14 days apart. The degree of resistance was significantly higher than that resulting from a single injection. Resistance was apparently stimulated by the activated oncosphere or a stage of cyst development prior to 14 days of age. Studies on oncospheres cultured in vitro in sera collected from animals during immunization or after oral challenge showed that most cysts were killed before 7 days of culture had elapsed. This confirmed the observation that resistance was stimulated by an early stage of cyst development. The in vitro test also showed that two injections of oncospheres resulted in a marked increase in the lethal effects of serum. These lethal effects decreased with time, providing circumstantial evidence that the high degree of resistance stimu- lated by two or more injections may only be transient.