Bacteriological survey of leptospirosis in Zaria, Nigeria.

A total of 252 rodents were trapped in the environs of Ahmadu Bello University, Zaria, over a two-year period, of which 221 were brown field rats (Arvicanthus niloticus). Only these were found positive (4.5%). Titers were detected against Leptospira interrogans, serovars australis, icterohaemorrhagiae, tarassovi and hardjo. All positive sera except one reacted against a single serovar. Eight isolates were obtained from field rats: five were serovar australis, one ballum and two unidentified. Five isolates were recovered from 74 bovine kidneys examined: one was serovar pyrogenes and four unidentified. One unidentified isolate failed to react with any of the 16 screening leptospira antisera and another was tentatively considered to be serovar ballum. Two isolates, one ballum and one unidentified, were recovered from the Kubani stream waters. No leptospira was isolated from piggery sewage effluents collected at Kano and Kaduna. It is suggested that serovar ballum be included in any screening battery for leptospirosis in man and animals in Nigeria.