To study population kinetics during primary Ascaris suum infections, 3 groups of 52 pigs each were inoculated with 100, 1000, or 10,000 infective eggs. In all groups, the majority of larvae was found in the liver on day 3 post inoculation (p.i.) and in the lungs on day 7 p.i. Liver white spots, caused by migrating larvae, were most numerous at day 7 p.i., whereafter they gradually healed, and only low numbers of granulation-tissue type white spots and lymphonodular white spots persisted at days 21-56 p.i. Independent of dose level, 47-58% of the inoculated eggs were recovered as larvae in the small intestine on day 10 p.i., but most larvae were eliminated at days 17-21 p.i. This elimination started earlier and removed a higher percentage of the worms with increasing inoculation dose, resulting in small strongly aggregated worm populations by day 28 p.i. (k of the negative binomial distribution was low: 0.2-0.4) without significant differences between groups. Thus, overdispersion, which is a characteristic of both porcine and human ascarosis, is found here under experimental conditions where aggregation factors like host behaviour, transmission rate, host status etc have been partly or totally controlled.

Results suggest that age must be taken into account when interpreting results of echocardiography in young Standardbred racehorses because significant cardiac enlargement takes place with age and training. A larger heart was found in horses that were racing, and size of the heart was correlated with athletic performance of the horse.

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The purpose of this study was to assess the intraobserver variation of various echocardiographic measures in standardbred trotters. Serial echocardiographic examinations were carried out on eight standardbred mares by one ultrasonographer for 5 separate days. During each examination, five nonconsecutive cardiac cycles (frames) were recorded and an average obtained for each individual measure. Various echocardiographic measures were obtained by use of two-dimensional (2-D), M-mode, color flow Doppler and pulsed wave Doppler echocardiography. The total variation in the echocardiographic measurements was split into three levels: the variation between horses, the day-to-day variation within individual horses, and finally the variation within horse on the same day of examination (intercardiac cycle variation). The intraclass correlation coefficient (ICC) was calculated for each measure. The ICC represents the variability of the measurements because of differences between the horses. In general the 2-D, M-mode and color flow Doppler measures had higher ICC values (ICC from 0.63 to 0.95) than the pulsed wave Doppler measures (ICC from 0.24 to 0.46), and the former measures were more repeatable than the pulsed wave measures. Exceptions to that were left ventricular free wall in diastole, the pulmonary artery in systole and the left ventricular mass, which all had low repeatability (ICC from 0.22 to 0.49). The results were used to calculate the relative differences that must be detected to diagnose a statistically significant change between two measurements in an individual horse. Differences from 4.2% to 21.8% must be achieved to document significant changes between serial measurements. A general tendency is that the color flow and pulsed wave Doppler measures require a larger relative difference (11.4-21.8%) between the measures to point out statistically significant cardiac changes than the 2-D and M-mode measures (4.2-13.9%).

During the course of carrying out studies on the role of intestinal immunity in blocking the migration of larval Ascaris suum in the pig, it was discovered that the prevailing understanding of larval penetration sites was at variance with our observations. Therefore, a detailed investigation of the migration of A. suum 1.2 larvae through the intestine was initiated. The results demonstrate that the 1.2 larvae invade almost exclusively the wall of the pig cecum and colon and not the small intestine as is generally believed. The larvae were recovered from the mucosa of the cecum and colon as early as 3 hr postinoculation (PI) with infective eggs and were recovered from the liver by 6 hr PI. The maximal recovery of larvae (total larvae and larval/g of mucosa) from the intestinal mucosa occurred between 6 and 12 hr PI; by 24 hr PI, virtually all of the larvae had disappeared from the mucosa. These observations correct a common misunderstanding of this aspect of the life cycle of A. suum in the pig, and they raise 2 issues related to the biology and pathogenesis of Ascaris in humans. What is the actual migratory and development behavior of Ascaris lumbricoides and A. suum in humans and the potential risk for liver lesions? Most authors, in describing the life cycle of A. lumbricoides, either ignore or discount a possible obligatory liver stage of development, and, consequently, the potential for lesion formation similar to that which occurs in pigs infected with A. suum. This issue takes on added importance with the growing evidence that A. suum is an important zoonoses.