Studies on the interaction between Salmonella enterica ser. Typhimurium and intestinal helminths in pigs.

Concomitant infections with helminths and bacteria may affect the course and the resulting disease outcome of the individual infections. Salmonella, Oesophagostomum, Trichuris and Ascaris coexist naturally in pig herds in Denmark, and possible interactions were studied. Pigs in one experiment were trickle infected with low or moderate dose levels of Oesophagostomum spp. and challenge infected with S. Typhimurium. In another experiment, pigs were inoculated with S. Typhimurium followed by a challenge exposure to either Oesophagostomum, Trichuris or Ascaris. Enhancement of the Salmonella infection was not demonstrated in either experiment. The helminth effect on the pigs was modest and may explain the lack of influence on the Salmonella infection. A previous experiment with a larger Oesophagostomum infection level resulted in enhancement of the S. Typhimurium infection. A dose dependency of the interaction is therefore suggested. However, the relatively high worm burdens in the present study suggest that infection with these common pig helminths does generally not influence the course of concurrent S. Typhimurium infections under natural conditions.

Natural progression of Oesophagostomum bifurcum pathology and infection in a rural community of northern Ghana.

An estimated 250,000 people in northern Ghana and Togo are infected with the intestinal helminth parasite Oesophagostomum bifurcum, as detected by stool cultures. Clinical disease caused by O. bifurcum is responsible for about 50 cases per year at the region's central hospital, and presents as painful abdominal masses: inflammatory colonic nodules containing live juvenile stages of the helminth. In individuals living in villages highly endemic with O. bifurcum infection, colonic pathology visible by ultrasound is also highly prevalent. These nodules also contain O. bifurcum juvenile worms but are apparently asymptomatic. Thus, O. bifurcum infection and asymptomatic colonic pathology are highly prevalent within this area, but clinical disease is relatively uncommon. The natural evolution and regression of the colonic pathology in an endemic community in northern Ghana and its distribution within the population is described. Of the 299 individuals in the study group, 28% had colonic pathology at recruitment in the late-rainy season, which decreased with a half-life of 3-4 months during the dry season. Of those negative at recruitment, 28% developed nodules during the year, the majority appearing at the end of the subsequent rainy season. Children tended to have a higher prevalence and intensity of ultrasound-visible pathology compared to adults. Almost half (49%) of the study group had colonic nodules at least once during the year, and 2% of these individuals presented with clinical disease to the local hospital during the mid-rainy season.

The role of pigs as transport hosts of the human helminths Oesophagostomum bifurcum and Necator americanus.

We conducted a study in an endemic area of both Oesophagostomum bifurcum and Necator americanus in northern Ghana to examine the possibility of pigs acting as transport hosts for these two human helminth species, due to the commonly observed coprophagic habits of pigs. Under controlled conditions four parasite-free pigs consumed fresh faeces from people heavily infected with both helminths, and faeces were subsequently collected from the rectum of the pigs from 5 to 50 h post-feeding. Four to five per cent of the O. bifurcum and N. americanus eggs fed to the pigs were viable and retrieved as third-stage larvae after coproculture of the pigs' faeces. We discuss the possible impact of the coprophagic habits of pigs as potential parasite transport hosts during different seasons in this area of West Africa.

Inactivation of eggs and larvae of the cattle nematodes Ostertagia ostertagi and Cooperia oncophora after passage in pigs.

The study investigated the effect of gastrointestinal passage in pigs on free-living stages of bovine nematodes. Two Landrace x Yorkshire pigs, A and B, were fed fresh eggs of Ostertagia ostertagi and Cooperia oncophora while two other pigs, C and D, were fed third stage larvae (L3) of the same parasites. Faeces from the pigs were collected for 48 h after ingestion. In pigs A and B, 15 and 66% of the eggs were recovered after passage, respectively. However, only 0.003 and 0.002% of the ingested eggs developed into third stage larvae (L3) after subsequent culturing. In pigs C and D, 0.01 and 0.02% of the L3 survived the passage of the gastrointestinal tract. Fresh O. ostertagi and C. oncophora eggs were cultured in parasite free porcine and bovine faeces. Only 0.05% L3 developed in porcine faeces, whereas 21% of the eggs developed into L3 in the bovine culture. Our results demonstrate an extremely poor rate of development and survival of both bovine nematode eggs and infective larvae after passage in pigs. It may imply that pigs can play an important role in reducing transmission of cattle nematodes if the two species are grazed together or alternately.

Parasite-specific IL-4 responses in Ascaris suum and Trichuris suis-infected pigs evaluated by ELISPOT.

The objective of the present study was to develop an ELISPOT method to measure parasite-specific IL-4 producing cells during experimental Ascaris suum and Trichuris suis infections in pigs. In many experimental settings it is useful to be able to measure changes in specifically induced cytokines over time at post-mRNA level; in particular, specific measurement of IL-4 is important for studies on nematodes due to the key function of IL-4 in driving the Th2 response. Two separate experiments were carried out, one with A. suum and other with T. suis infection in which we were able to measure statistically significant increases in specific IL-4 production in peripheral blood mononuclear cells over time in parallel to an increase in blood eosinophils. Furthermore, IL-4 was measured in the colon lymph node of T. suis-infected pigs. Egg excretion and worm burdens at necropsy were measured. The ELISPOT method is a valuable tool for future experimental settings as it enables repeated and parasite-specific measurement of IL-4 at protein level when investigating, for example, immunomodulatory properties of helminths. Furthermore, the method could be used to identify specific parasite antigens inducing IL-4 production.