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

myscus maniculatus) and the rabbit; in each of these species N. brasiliensis is able to develop to adulthood, although the degree of its adaptation varies greatly between hosts species. As to Mastomys natalensis, the longer prépaient period, the lower take (64-82% of that seen in the rat), the low level and short duration of egg output, the rapid rejection of worms, all seem to indicate a lower degree of adaptation of N. brasiliensis to that host species than to the rat. Exp.1. Mastomys Rat Exp. 2. Mastomys Rat 5 6 7 8 9 10 11 12 13 15 16 17 18 19 Days Fig. 2: Egg output pattern in the rat and Mastomys infected with 500 Nippostrongylus brasiliensis larvae Concerning the susceptibility of the multimammate rat it should be taken into consideration that in the present studies a rat strain of N". brasiliensis was used for experimental infections throughout. In view of this it might well be expected that the rate of establishment of infection could considerably be increased by using a Mastomys-adapted strain, as has already been shown experimentally with mouse-adapted (WESCOTT and TODD, 1966) and hamster-adapted (HALEY, 1958a, 1966a

( b) strains of X. brasiliensis. On experimental infection of Mastomys with Nippostrongyles maintained in the rat a take of 20-45% can be expected. In certain host species - e.g. hamster - female host specimens are more resistant to Nippostrongylus infection than males (HALEY, 1958b). Contrarily, in the present study male and female multimammate rats showed an almost equal susceptibility to primary infection (Table 1). Observations of alike nature were reported also by LÄMMLER et al. (1968). No difference was seen in the degree of resistance to challenge in female and male Mastomys (Table 3).