Régulation des populations de Nématodes gastro-intestinaux ...

2.2. Parasitological monitoring
Résultats
Egg counts were performed according to the modified McMaster technique (Raynaud,
1970) on fecal samples collected twice a week from D15 to D30 for the previously-infected
groups (INRA 401 and BBB groups A) and from D60 to D75 for all three groups.
Immediately after necropsies, the contents and washings of the abomasum were collected and
passed through a 40 µm sieve to conserve the coarse material containing worms. The whole
abomasum was digested in pepsin-hydrochloric acid solution (37°C, 6 h) to collect the tissue
dwelling nematode stages. The contents, washings and digested materials, were preserved in
absolute alcohol. The volume of these materials was then adjusted to 1 L and worms were
counted in a 10% aliquot and classified as adult male or female, immature male or female, or
L4. Furthermore, twenty adult female worms were randomly picked from each D75 sample
for total parasite length measurement and counting of eggs in utero. For this purpose,
individual female worms were allowed to disintegrate in 200 µL of 20% Milton Sterilizing
fluid (Milton Pharmaceutical LTD, contains 2% w/v sodium hypochlorite and 16% w/v
sodium chloride) in distilled water (Kloosterman et al., 1978) and all eggs liberated from the
uterus were counted for each worm.
2.3. Fecal egg hatch test
At the end of experiment, fecal samples were collected during necropsy directly from the
rectum. 3g of each sample was taken for eggs per gram (EPG) determination, while the
remaining material was weighed and cultured at 23°C for 10 days with regular humidification.
The samples were then transferred to a Baermann apparatus for collecting infective larvae of
H. contortus. 24 hours later, all the fluid contained in the apparatus was collected and larvae
were counted in 500µL of the suspension. To maximize the number of counted larvae, the
remaining fecal material (after Baermann) was weighed again and 1g was dissolved in 100 ml
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