Biological parameters of Trichostrongylus colubriformis in Meriones unguiculatus

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In a series of three experiments, 64 jirds, Meriones unguiculatus, were infected with 700 infective larvae of Trichostrongylus colubriformis for the study of several biological parameters of this laboratory host–parasite model. In jirds the third stage larvae of T. colubriformis were shown to reach the fourth larval stage by the Day 6 post-infection (PI). By Day 10 PI, all the worms harvested had reached the immature adult stage. All immature adult stages of T. colubriformis developed to sexually mature adult stage by Day 12 PI when the female worms showed developing eggs in their uteri. Developed eggs were observed in the uteri of females on Days 13 and 14 PI. The first eggs of T. colubriformis appeared in the faeces of jirds on Day 13 PI. The peaks of egg production were recorded between Day 21 and Day 31 PI. Immunosuppression of jirds infected with 700 L 3, by administration of dexamethasone from Day 57 to Day 94 PI led to increased faecal egg count when compared to untreated controls. All the worms were located in the small intestine. The jirds of dexamethasone treated group harboured higher number of adult worms than those of the untreated group. The number of adult worms was significantly higher in the first part of the small intestine than in the three other similar parts of the small intestine. The coefficient of correlation between the faecal egg count and worm number on the day of necropsy of jirds ranged between r = 0.58 and r = 0.89. Patent infections in jirds were maintained till the end of experiment on Day 100 PI, indicating that in this host and unlike other laboratory hosts, T. colubriformis is responsible for long lasting infections similar to what happens in domestic ruminants. The results of the present study suggest that the jird is a suitable laboratory model to study various aspects of this host–parasite relationship.