Nematospiroides dubius in the jird, Meriones unguiculatus: factors affecting the course of a primary infection.

This project investigated the influence of the age and sex of the host and the level of infection with Nematospiroides dubius on the establishment and duration of a primary infection in the jird. It was found that 30 to 35% fewer worms matured in jirds than in mice and that this proportion was unaffected by the level of infection or by the sex of the host. In contrast the age of the jird was found to be critically important in determining the number of adult worms recovered 14 days after infection. Thus, maximum susceptibility to infection was observed when jirds were 18 to 22 days old. In older jirds susceptibility declined until 30 days after birth and thereafter, when approximately 70% of the infective larvae matured (relative to the number of worms maturing in mice). The duration of a primary infection in jirds was similar in both sexes but was influenced by the level of infection and by the age of the host at infection. Heavier infections (500 larvae) lasted about 10 days longer than low level infections, and expulsion of the parasite occurred even when the host was infected with only five larvae. The duration of a primary infection was markedly prolonged in neonatal jirds, faecal egg counts remaining positive for 54 to 56 days after infection of 12-day-old jirds. These results supply some further baseline data for future work on the biology of N. dubius in the jird and they provide support for the involvement of immunological processes in the termination of primary infections of this parasite in mature jirds.