L. Gruner et al., WORM POPULATION CHARACTERISTICS AND PATHOLOGICAL-CHANGES IN LAMBS AFTER A SINGLE OR TRICKLE INFECTION WITH TELADORSAGIA-CIRCUMCINCTA, International journal for parasitology, 24(3), 1994, pp. 347-356
The regulation of the worm population and of its pathological effects
was studied after a single or trickle infection with T. circumcincta.
One hundred and twenty lambs, 60 Romanov and 60 Merinos d'Arles, 3 mon
ths old, were distributed in four balanced groups: non-infected (G0),
infected with 7000 L3 per animal once and slaughtered after 4 weeks (G
14) or 8 weeks (G18), and infected 8 times and slaughtered after 8 wee
ks (G88). Parasitological, histological, haematological parameters and
weight pins were recorded on each animal. Female and artificially nur
sed lambs had lower worm burdens and egg counts (epg) than males and n
aturally suckled lambs. No difference in parasitological parameters wa
s seen between the two breeds, but Merinos lambs infected once, had a
higher increase in pepsinogen concentrations than Romanov lambs. In th
e infected animals, a significant proliferation of mast and eosinophil
cells was observed in the abomasum wall. Serum pepsinogen concentrati
ons were significantly higher 3 weeks p.i. and the weight gain was dep
ressed during the first month p.i. The worm population was more numero
us and younger in group G 14 compared with G18 in which 24% of the wor
ms had been expelled during the second month p.i. The female worms in
G 18 were longer and had more eggs in utero and higher egg output. Aft
er the trickle infection (G88) the take was reduced, female worms were
longer with more eggs in vagina (pars ejectrix) and there was a highe
r variability in the number of eggs (compared with G18 data). The peps
inogen rise was smaller but no specific effect was seen on histologica
l and haematological parameters. Repeatability values around 0.5 were
estimated between 4 consecutive days of egg counts. However the correl
ations between epg 1 and 2 months p.i. or between pepsinogen concentra
tion and parasitological parameters were not significant.