Schistosoma japonicum: day to day variation in excretion and hatchability of parasite eggs in the domestic pig, Suis suis.

The aim of the present study was to describe the course of an Schistosoma japonicum infection in individual pigs over time, with special regards to fecal egg counts and egg hatchability, emphasizing the extent of variation during and between days. Five specific pathogen free Danish Landrace/Yorkshire/Duroc crossbred male pigs were each given 3500 cercariae intramuscularly. From day 36 to 62 post infection, fecal samples were collected from each pig, morning and evening. Pigs were perfused 62 days post infection. Actual fecal egg counts, miracidial counts, and worm burdens were determined. The trend of fecal egg excretion was adequately described with a third order polynomial and logarithmic link function. Miracidial counts were related directly to morning fecal egg counts through a simple linear function. The study revealed a fairly similar overall pattern of egg excretion for all pigs, showing an increase in egg excretion until week 8, followed by a marked reduction to almost zero. In general, large fluctuations around this trend were seen for all pigs, as revealed in variations in egg counts within the same day as well as between days. However, as revealed by the estimated model lines, these fluctuations are due to random variation in egg density in stools rather than being caused by biologically determined cycles. An exact time for both first occurrence of eggs in feces (days 35-38 post infection) and for peak egg counts (days 44-48 post infection) was predicted for each individual pig. Furthermore, the model revealed that miracidial counts can be related directly to the expected fecal egg counts of the same day through a parameter, which represents hatchability. This hatchability parameter was found to be independent of time post infection for each pig, but large individual differences were seen in hatchability between the pigs.

Peroral infection of pigs with Schistosoma japonicum cercariae.

Infections with the zoonotic trematode, Schistosoma japonicum in pigs serves as a valuable model for studying natural definitive host/parasite relationships and a model for human schistosomosis japonica. In the present study the efficiency of a peroral infection route was compared with that of an intramuscular route of infection. Eleven specific pathogen-free Danish Landrace/Yorkshire/Duroc crossbred male and female pigs were divided into two groups of five and six pigs, respectively. Each pig was given 1000 cercariae, either placed in droplets on the mucosa in the buccal cavity, or as medium-suspended cercariae injected into musculus biceps femoris of one of the hindlegs. Ten weeks post infection, all pigs were killed with pentobarbital and the venous system perfused. Worm burdens and liver egg counts were determined and worm fecundity was calculated. S. japonicum infections were established in all individuals in both groups of pigs. When comparing the two groups, the peroral group had significantly higher number of immature worms, whereas the intramuscularly infected group had significantly more worm nodules. However, no difference was seen in total number of worms. No statistical significant differences were found in neither tissue egg counts nor worm fecundity when comparing the two groups. The results from the present study showed a delay in maturation of infection following a peroral infection as compared with an intramuscular infection, but comparability was seen between overall worm establishment and egg production.

Schistosoma japonicum in the pig: a new technique for estimation of intestinal tissue egg counts.

This study introduced a new method for estimating intestinal tissue Schistosoma japonicum egg counts, based on scraping of the mucosal layer of different sections of the intestines. Twenty-eight Danish Landrace/Yorkshire/Duroc crossbred pigs were divided into 3 groups of 15, 5 and 8 pigs, respectively. Pigs were fed either a high- or low- protein diet and were infected by an intra-muscular or per-oral route of infection with doses of either 1,000, 1,500 or 3,000 S. japonicum cercariae. The pigs were killed 9-11 weeks post infection. For all 28 pigs the intestines were divided into 3 sections: cecum, colon and rectum and the entire mucosa was scraped off the serosa of each section and homogenized. Subsequently, samples corresponding to 5 g homogenised mucosal tissue were digested and egg counts were determined and correlated to liver egg counts. In order to compare the relative distribution of eggs in the mucosa and the serosa, small intestinal wall subsamples formerly taken from each section from a subgroup of 5 pigs were homogenized and egg counts determined for both the mucosa and serosa. The number of eggs were significantly higher in the mucosa than in the serosa. Egg counts estimated from digestion of mucosa subsamples either over or underestimated egg counts based on scrapings of the entire mucosa when compared, reflecting the very patchy distribution of S. japonicum eggs in the intestinal wall. Correlating liver egg counts with the number of eggs based on scrapings from the entire mucosa from cecum, colon and rectum, respectively, significant correlations were found for 2 out of 3 groups of pigs. The present study revealed that estimating intestinal tissue egg counts based on scrapings of the entire mucosa is a reliable and convenient approach, nicely supporting the liver tissue digestion approach. In addition, a reduction of the processing time of intestinal tissue in general was achieved due to the very simple scraping technique.

Schistosoma japonicum and Trichuris suis infections in pigs fed diets with high and low protein.

The aim of the study was to measure the impact of Schistosoma japonicum and Trichuris suis infections in young growing pigs fed low- or high-protein diets. Thirty-two pigs. 6-10 weeks old, were randomly allocated to 2 groups receiving either a high- or a low-protein diet. After 11 weeks half of the pigs from each group were infected with 1500 S. japonicum cercariae and 4000 T. suis eggs. The weight of the pigs was measured throughout the study, and blood and faecal samples were collected every second week from the time of infection. At the time of infection the low-protein pigs had significantly lower mean body weights, haemoglobin and albumin levels compared with the high-protein pigs, and this pattern continued throughout the study. The serum albumin concentration was further significantly reduced in the infected low-protein pigs compared to the non-infected low-protein pigs. Significantly more S. japonicum worms as well as faecal and tissue eggs were found in the low-protein pigs compared with the high-protein pigs. No differences between the 2 diet groups were observed in T. suis establishment rates or faecal egg excretion. We conclude that this low-protein diet increased the establishment rates of S. japonicum, favoured larger deposits of S. japonicum eggs in the liver and faecal egg excretion, reduced weight gains and caused anaemia and hypoalbuminaemia in young growing pigs as compared with a high-protein diet.