The causal prophylactic activity of the novel hydroxynaphthoquinone 566C80 against Plasmodium berghei infections in rats.

The influence of the novel hydroxynaphthoquinone 566C80 on exoerythrocytic development of Plasmodium berghei was examined in Brown Norway rats. The procedure employed was designed to identify residual activity of the drug against tissue merozoites emerging into the bloodstream and to distinguish this from any observed causal prophylactic activity against the liver stages. Single oral doses of 10 and 1 mg/kg of 566C80 administered 3 hours after sporozoite-inoculation were effective in preventing the appearance of a patent parasitaemia, while a dose of 0.1 mg/kg significantly reduced the severity of the ensuing blood infection. There was a pronounced residual effect of 566C80 against the blood forms at a dose of 10 mg/kg, a slight residual effect at a dose of 1 mg/kg, but no apparent residual effect at 0.1 mg/kg. At the time when EE merozoites would normally emerge into the bloodstream, an aliquot of blood was sub-inoculated into mice from sporozoite-infected, 566C80-treated rats. This procedure confirmed that 566C80 is active against the exoerythrocytic stages of Plasmodium berghei.

Susceptibility of colostrum-deprived swine of various ages to streptococcic lymphadenitis.

The effect of age on susceptibility of young pigs to streptococcic lymphadenitis was investigated. Twenty-nine cesarean-derived, colostrum-deprived pigs were allotted to 7 groups exposed to type IV group E Streptococcus (GES) at 5, 14, 28, 35, 56, 70, and 84 days of age. Four cesarean-derived, colostrum-deprived pigs were maintained as nonexposed controls. Six naturally farrowed, susceptible controls were exposed to GES at 63 to 84 days of age. All exposed pigs were killed and necropsied 28 days after exposure. Lesions of streptococcic lymphadenitis were not observed in pigs exposed at 5 or 14 days of age, except for 1 microabscess in a mandibular lymph node in a pig exposed at 14 days, but GES was recovered from 11% of lymph nodes examined from pigs of those age groups. Lesions and GES-positive lymph nodes were frequent in cesarean-derived, colostrum-deprived pigs exposed at 28 days and older and in susceptible controls. Serologic response to exposure, as determined by microtitration agglutination test and bactericidal test, was observed only in pigs exposed at 14 days and older. The absence of abscess development in pigs exposed at 5 or 14 days of age was not caused by antibody or failure of infecting organisms to reach the target organs.