PREPATENT PERIODS OF DIFFERENT OESOPHAGOSTOMUM SPP ISOLATES IN EXPERIMENTALLY INFECTED-PIGS

To define prepatent periods of different Oesophagostomum spp. isolates we carried out two separate experiments, one using two monospecific l aboratory isolates and another using laboratory isolates as well as is olates obtained from pig herds having different management systems and with different anthelmintic treatment histories. Pigs were inoculated with 1,000-2,000 infective larvae. Fecal samples were collected daily beginning on days 15 and 16 postinoculation (p.i.). Fecal cultures we re set up at different times to yield larvae that could be identified by DNA analyses. All pigs started to excrete eggs on days 18-24 p.i. T he mean prepatent period was 20.2 +/- 1.4 days, with no significant di fference being observed between species and isolates. Prepatent period s of 17-19 days were found for the monospecific laboratory isolates of O. dentatum and O. quadrispinulatum. These findings conflict with par asitology textbooks; therefore, suggestions as to the possible reasons for the observed short prepatent periods are given.