Régulation des populations de Nématodes gastro-intestinaux ...

3 – RESULTS
3.1. Parasitological values
3.1.1. Fecal egg excretion
Résultats
No fecal egg excretion was recorded in lambs of groups C (uninfected controls)
throughout the experimental period. This was confirmed later by the absence of worms in the
abomasum. During the initial infection, fecal egg excretion started on D19 in INRA 401
(group A) lambs while it was delayed for about 4 days (D23) in BBB (group A) lambs (Figure
1A). Furthermore, fecal egg counts (FEC) in the BBB breed were significantly lower than that
of INRA 401 (P < 0.001). During the challenge infection, i.e. the second phase of the
experiment, the first fecal egg excretion was observed on D64 for INRA 401 lambs and on
D66 for BBB lambs (Figure 1B) i.e. respectively 19 and 21 days post secondary infection.
The difference between previously-infected and primary-infected groups within a breed was
not significant. Similar to that observed during the initial infection of group A, FEC were
lower in the BBB group B lambs than in INRA 401 group B lambs (P = 0.005). Nevertheless,
FEC were not different between BBB and INRA 401 groups A.
3.1.2. Worm burden, size and fecundity of adult females
On D49 (4 days post challenge), only L4 stages of the parasite were found in the
abomasum of the two breeds of lambs. Both groups (A and B) of BBB lambs exhibited
significantly lower worm counts than their INRA 401 counterparts (P < 0.05), while there was
no group difference within breeds (Table 3).
On D75 (30 days post challenge), there was no significant difference for worm burdens
between previously-infected and primary-infected INRA 401 lambs. Surprisingly, higher
worm burden was registered (P < 0.05) in previously infected BBB lambs compared to the
primary-infected group. Moreover, only primary-infected BBB lambs had fewer worms than
INRA 401 (P < 0.05). Thirty days after challenge (D75), worms at any developmental stages
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