Dr. Murai Éva szerk.: Parasitologia Hungarica 12. (Budapest, 1979)

days later takes found in Mastomys and rat controls were 35.4 and 55.6%, respectively, comparing to takes of 0.7-1.0 and 3.9% in multimammate rats and rats, respectively, previously exposed to primary infection (Table 3). Table 2 Dinamics of worm rejection in the rat and Mastomys after infection with 500 Nippostrongylus brasiliensis larvae Post mortem worm counts In the rat In Mastomys Post mortem worm counts No. of animals Worm counts No. of animals Worm counts after infection No. of animals mean (ranges) % take No. of animals mean (ranges) % take 6 3 304 (224 - 352) 60.9 3 195 (114 - 315) 39.0 8 3 274 (259 - 295) 54. 8 3 90 ( 33 - 183) 18. 1 9 3 224 (207 - 235) 44. 9 3 41 ( 0 - 125) 2. 7 12 3 168 (152 - 181) 33. 7 4 0 0.0 14 3 62 ( 39 - 95) 12. 4 4 0. 5 (0 - 1) 0. 1 15 3 31 ( 0 - 91) 6. 2 Table 3 Susceptibility to challenge of the rat and Mastomys formely exposed to 500 larval primary Nippostrongylus brasiliensis infection Host animals Larval dose Worm counts on day 6 Animals immune/ total Species Sex Primary Secondary* mean (ranges) % take Animals immune/ total Mastomys male 500 500 3. 8 ( 0 - 7) 0. 7 6/6 Mastomys female 500 500 5. 1 ( 0 - 17) 1. 0 6/6 Rat female 500 500 19.9 ( 0 - 95) 3.9 12/12 Mastomys control male 0 500 177. 4 (111 - 276) 35. 4 0/5 Rat control female 0 500 278. 2 (149 - 359) 55. 6 0/5 * On day 17 after primary infection. On day 15 all animals were dosed by thiabendazole at 200 mg/kg i. p. Discussion Susceptibility In the present studies a total of 117 multimammate rats was exposed to infection with N. brasiliensis, and the parasite was able to_establish itself in each. These observations lend support to the suggestion put forward by LÄMMLER et al., (1968) and PANDE et al. (1977) that Mastomys natalensis is within the host range of N. brasiliensis. The host spectrum of that parasite has included the mouse, hamster, cotton rat, white-footed deer mouse (Pero-