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

of egg output lasting not longer than 2-3 days, i.e. the course of infection appears to follow the pattern outlined by the German authors (Table 4). A minor deviation that in our Mastomys the course of Nippostrongylus infection to be one day shorter was observed. According to LAMMLER et al. (1968) initially the sex ratio of the Nippostrongylus populations harboured by Mastomys is characterized by an almost equal proportion of males and females, or by a slight predominance of females; later on sex ratio changes towards the predominance of males. Against this PANDE et al. (1977) reported shift of the sex ratio towards female predominance with progressing time (more than 60% by days 12-15), and attributed the subsequent depression of egg production to inadequate fertilization of the females rather than to the immunological response of the Mastomys. This interpretation is hardly tenable. From Fig. 2 and Table 2 it can be seen that simultaneously to the sudden fall of egg counts on day 8 also the worm counts of the Mastomys hosts fell to about 50%, by day 9 already to 6.9% of the maximum 6-day worm count, i.e. the worms themselves will also be expelled. It is therefore suggested, that the abrupt drop of egg output was due to the elimination of the parasites themselves, rather than to the depression of their egg production. Immunity The present studies provided the first evidence on the resistance exhibited to homologous reinfection by Mastomys natalensis after primary Nippostrongylus infection (Table 3). Like in the rat, also in the multimammate rat a primary 500 larval infection was found to elicit firm protective immunity to subsequent challenge. Summarizing, it is concluded that Mastomys natalensis can be infected by Nippostrongyles without any difficulties. After a patent period of only 2-3 days duration the established primary worm burden will be spontaneously rejected from this host species. Infected animals develop strong immunity to reinfection. In view of the rapid course of infection in Mastomys, this model does not seem to be very suitable for anthelminthic drug assays. References HALEY, A.J. (1958a): Host specificity of the rat nematode Nippostrongylus muris. - Am. J. Hyg., 67. 331-349. HALEY, A.J. (1958b): Sex differences in the resistance of hamsters to infection with the rat nematode, Nippostrongylus muris. - Exper. Parasitol., 7. 338-348. HALEY, A.J. (1966a): Biology of the rat nematode Nippostrongylus brasiliensis III. Characteristics of N. brasiliensis after 30 to 120 serial passages in the Syrian hamster. J. Parasit., 52. 98-108. HALEY, A.J. (1966b): Biology of the rat nematode Nippostrongylus brasiliensis IV. Characteristics of N. brasiliensis after 1 to 40 serial passages in the Syrian hamster. J. Parasit., 52. 109-116. KASSAI, T. (1968): A parazitás immunitás némely jelenségének vizsgálata patkány-Nippostrongylus brasiliensis modellen. - Parasit.

Hung., I. 37-56. LÄMMLER, G. - ZAHNER, H. - TEXDORF, I. (1968): Infektionsversuche mit Darmnematoden, Cestoden und Trematoden bei Mastomys natalensis (Smith, 1834). - Z.f. Parasitenkunde, 31. 166-202. PANDE, V. - KATIYAR, I. C. - GEORGE, P.A. - SEN, A.B. (1977): Susceptibilities of albino rat and Mastomys natalensis to Nippostrongylus brasiliensis infection. - Indian J. Parasit., 1. 41-46. REDL, P. - GYŐRFFY, Gy. (1978): A kocapatkány (Mastomys natalensis) mint laboratóriumi állat. - Magy. Ao. Lapja, 33- 844-848.