ABSTRACT
The use of ceftiofur sodium or streptomycin for treatment of leptospirosis was investigated in hamsters (M.auratus) experimentally infected with L. interrogans serovar pomona. The inoculi of leptospires for infection was adjusted for a dilution that presents the median of 20 to 30 microrganisms per microscopic field, 200 times magnification. In the first experiment one group of animals received one dose of streptomycin, at the concentration of 25 mg/kg body weight by the intramuscular route and the other was treated with one or two intramuscular injections of ceftiofur sodium, 20 mg/kg body weight, each 24 hours. In the second experiment the ceftiofur sodium was tested in one intramuscular dose of 30 or 40 mg/kg/body weight. In the third experiment it was investigated one intramuscular dose of ceftiofur sodium at the concentration of 25 mg/kg/ body weight, against five serial dilutions of the leptospires inoculi. In all of the three experiments the first antimicrobial treatment was performed 48 hours after the infection with leptospires. The hamsters were observed two times a day searching for signs of the infection (weakness, hemorrhagies, icterus, incoordenation). When they became ill they were killed at the moribund stage of the disease and the leptospiral infection was atested by the demonstration of the microorganisms in liver or kidney suspensions examined under dark field microscopy. The animals that presented no signs of the disease were killed in the 21st or 30th post infection day, and at this time it was investigatet the presence of leptospires by cultivation of kidney samples and the presence of agglutinines in blood by the microscopic agglutinantion test. The results showed that streptomycin as able to stop the development of the infection with no kidney carriers in the survivors. With the ceftiofur sodium the lowest effective dose was one intramuscular injection of 25 mg/kg/body weight. All of the animals treated with this concentration presented no signs of infection and 96% (48/50) of them presented no leptospires in kidney cultures performed at the 21 post infection day.
KEY WORDS:
Leptospirosis; hamster; streptomicin; ceftiofur sodium.