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This study reports a comparison between faecal egg count reduction test (FECRT), egg hatch assay (EHA) and larval development assay (LDA) for detecting anthelmintic resistance in equine strongyles. Resistance to benzimidazoles was demonstrated in 33 of 42 (79%) farms tested by FECRT and in 32 (62%) of the 52 farms tested by EHA. As the reference strain used was not fully susceptible to benzimidazoles it was not possible to determine the level of resistance by LDA. Pyrantel resistance was indicated on three of 15 farms by faecal egg count reduction. Resistance was also indicated by LDA for one of these farms. In addition resistance was indicated by LDA on two more farms that were not tested by FECRT. Further testing is needed to confirm if these findings are truly indicative of resistance. Generally, correlations between the tests were poor and it was not possible to use the outcome of one test to predict the outcome of another.

A trickle infection experiment was undertaken to study in detail the population dynamics of Oesophagostomum dentatum in pigs. Three groups of 32 pigs were inoculated via the feed twice weekly with 100 (Group A), 1000 (Group B) or 10000 (Group C) O. dentatum infective larvae (L3). Five pigs from each group were killed 2, 4, 8, 12, 16, and 20 weeks after the first inoculation (p.i.) to determine their worm burdens. Weekly faecal egg counts were determined. At slaughter, worms were counted, differentiated according to sex and developmental stage, and their length measured. Faecal egg counts ranked with dose rate until week 15, but later were more variable. The proportion of the total number of L3 administered which were recovered at slaughter inversely ranked with dose rate. In group C it decreased over time, whereas in groups A and B there was no consistent pattern. Worm fecundities (epg/female) in groups A and B were higher than in group C. The lengths of the female worms increased over time, whereas the lengths of the male worms remained approximately constant from week 8. The study suggests reduced establishment of incoming larvae and lower fecundity of the female worms at high dose levels.

The present study examined the possibility of using a tissue subsample to estimate the total number of Schistosoma japonicum eggs in the liver or an intestinal section. Sixteen male Landrace/Yorkshire crossbred pigs were each infected with 500 S. japanicum cercariae and killed 12 weeks post infection. Five-gram samples were taken from specific areas of the liver, colon, caecum and rectum, and tissue egg counts (TECs) were determined by digestion of the tissue sample in 3% KOH for 18 h according to a standard procedure. The rest of each tissue was also processed to determine whole tissue egg counts. For the liver, counts from 5-g samples taken from the left medial and left lateral lobes were not significantly different from counts for the whole liver, but counts from 5-g samples from the right lateral, right medial and central lobes differed significantly from whole liver counts. Variable results were obtained for 5-g samples from six specific points in the colon in comparison with the whole colon counts. This latter result corresponded well to observed gross pathological findings indicating patchy egg deposition in the large intestine. One 5 g sample from either the caecum or rectum could not be used to estimate the whole tissue egg count because of the high variability in the counts. The results suggest that the processing time of liver tissue can be greatly diminished by using a 5 g subsample from a specific liver lobe to estimate the TEC of the whole organ.

Four groups with three pigs in each group were inoculated with Oesophagostomum dentatum larvae (L3 larvae). Groups 1 and 3 were inoculated with 20,000 larvae, and Groups 2 and 4 with 200,000 larvae. On Days 11 and 34, respectively, Groups 1 and 2 and Groups 3 and 4 were slaughtered, and the contents from the large intestines collected. Subsamples of intestinal contents were mixed with agar to a final concentration of 1% agar and allowed to set. The worms were allowed to migrate from the agar-gel into 38 degrees C 0.9% saline overnight. Then the worms were collected on a sieve (38 microns mesh) and counted. The worms retained in the agar-gel were counted after pouring the melted agar through a sieve (38 microns mesh). The results showed that more than 95% of the worms migrated out of the agar-gel, and subsequently were available for counting in an almost clean suspension. Additionally the method yielded a high worm recovery; all stages were recovered. The recovery percentage was not significantly affected by either the dose of parasites or the time interval from slaughtering to start of incubation (37-128 min).

This paper describes the worm populations in pigs experimentally infected by trickle infections with different dose levels of the nodular worm, Oesophagostomum dentatum. Four groups each of 20 helminth naive pigs, 10-12 weeks old, were inoculated with 0 (group 1), 100 (group 2), 1000 (group 3), or 10,000 (group 4) infective larvae twice weekly, and the pigs were killed after 10-13 weeks. No overt clinical signs were observed, and only group 4 had slightly lower food conversion rate (P < 0.05) than the controls. Faecal egg counts revealed that the nodular worms in pigs of groups 2 and 3 had a short prepatent period (3-4 1/2 weeks) and a fairly stable egg output, while the worms in the pigs of group 4 had prepatent periods of 3-10 weeks and low, unstable egg excretion. The mean worm burdens increased with the dose rate (group 2: 929 worms; group 3: 7467 worms; group 4: 19,847 worms), but detailed analyses of the worm populations from 10 pigs from each of the infected groups revealed a clear dose-dependency in worm recovery, percentage adult worms, worm lengths and female fecundity, as all these measures declined significantly with increasing dose level. The adult worms seemed to be shorter and less fertile when they were located posteriorly to their predilection site, and especially in group 4 many stunted infertile adults measuring only 2-5 mm were found in the posterior half of the colon, but there were no indications of worm expulsion. Superimposed on the main experiment was a cohort study in which 4 pigs of group 3 were given a single dose of 1000 pyrantel resistant larvae at day 56 (all other larvae were pyrantel sensitive), treated with 28 mg pyrantel per kg body weight at day 85 and killed at day 90. Appropriate control groups were included. The mean establishment of the cohort was similar to previously uninfected controls, but between-animal variation was much higher in the trickle infected group.

SUMMARYThis investigation compared the effect of two common types of diet on worm burdens and faecal egg counts of pigs inoculated with Ascaris suum and Oesophagostomum dentatum. The diets were both considered nutritionally sufficient for pigs of this age, and gave high and comparable growth rates. Pigs were inoculated with both worm species at 14 weeks of age and slaughtered 3 or 12 weeks later. At 3 weeks, A. suum larvae were numerous in the small intestine of pigs fed ground barley plus protein supplement, but were not detected from pigs fed a commercial full-constituent pelleted feed. At 12 weeks, however, average adult worm burdens were low and similar in both groups. At both slaughter times, O. dentatum worm burdens were significantly higher in pigs fed barley plus protein than in pigs given commercial feed, particularly for female worms, and the commercial diet led to worms being located further along the large intestine, and to reduced worm fecundity. The chemical composition of large intestinal contents differed significantly between pigs fed the two diets.

A double-blind study on 100 enuretic naval recruits failed to demonstrate any type of anti-enuretic effect of imipramine hydrochloride (Tofrānil).

Nine groups of 5 pigs were inoculated with Ascaris suum eggs on day 0. Groups 1, 2, and 3 were inoculated with 100 eggs, groups 4, 5, and 6 with 1,000 eggs, and groups 7, 8, and 9 with 10,000 eggs. On day 3, groups 1, 4, and 7 were slaughtered, on day 7 groups 2, 5, and 8, and on day 10 groups 3, 6, and 9. The liver (days 3 and 7) and lungs (days 3, 7, and 10) were removed and 2, 25% samples of both organs were collected. Larvae were recovered from 1 sample by the Baermann method and from the other by an agar-gel method. Overall there were no significant differences in the liver larval recovery between the 2 methods. The use of the agar-gel method resulted in a very clean suspension of larvae and thereby reduced the sample counting time by a factor of 5-10 compared to the Baermann method. With both methods larval recovery from the lungs resulted in a clean larval suspension that was easy to count, and there were overall no significant differences between the 2 methods, although there was a tendency toward the Baermann method recovering more larvae from the lungs than the agar-gel method. The tissue sample dry weight did not significantly influence larval recovery by the agar-gel method, and the time interval from slaughtering to start of incubation on day 3 (interval 51-92 min), day 7 (interval 37-114 min), and day 10 (interval 50-129 min) had no significant effect on recovery by either method.

Four groups each of 3 pigs were inoculated with Ascaris suum eggs. Pigs in groups 1 and 3 were inoculated with 1000 eggs, and pigs in groups 2 and 4 with 10,000 eggs. On day 10 and 21 post-inoculation (p.i.), respectively, groups 1 + 2 and 3 + 4 were slaughtered, and the contents from the small intestines collected. The contents were mixed with agar to a final concentration of 1% agar and allowed to sediment. The larvae were allowed to migrate from the agar-gel into 38 degrees C 0.9% saline overnight, and were then collected on a sieve (20 microns mesh) and counted. The larvae retained in the agar-gel were counted after pouring the melted agar through a sieve (20 microns mesh). The results showed that more than 97% of the larvae migrated out of the agar-gel and were available for counting in an almost clean suspension. The inoculation dose level did not significantly affect the recovery percentage, neither did the larval stage (10 or 21 days old larvae). The variation in the time interval from slaughtering to start of incubation (interval 57-155 min) did not significantly affect the recovery percentage.