THE EFFECT OF CONCURRENT OR SEQUENTIAL OESOPHAGOSTOMUM-DENTATUM AND O-QUADRISPINULATUM INFECTIONS ON THE WORM BURDENS OF THE 2 SPECIES IN PIGS

The interaction between the 2 nodular worm species in the pig, Oesopha gostomum dentatum (O.d.) and Oesophagostomum quadrispinulatum (O.q.), was studied by comparing the development and distribution of the speci es following single or mixed infections. The faecal egg excretion leve ls were assessed at regular intervals from week 3 post-inoculation, an d indicated a strong negative impact of the introduction of O.q. on th e continued egg excretion of O.d. All pigs were killed 9 weeks after t he first inoculations to determine the composition and location of the worm burdens in the large intestine. O.q. was found more anteriorly l ocated in the intestine than O.d., thus confirming previous descriptio ns. When both species were present, the distribution of O.d. was moved further posteriorly and was more spread out than in single-species in fections. There appeared to be no adverse effect of O.d. on the establ ishment and fecundity of O.q. However, the worm recoveries corroborate d the egg excretion observations, namely reduced worm burdens of O.d. if O.q. was introduced, or if O.q. was already present. It is uncertai n whether this effect is caused by differences in host reaction agains t the two species, or whether a more specific competition occurs betwe en the two nodular worm species in pigs.