Estimating transmission parameters of F4+ E. coli for F4-receptor-positive and -negative piglets: one-to-one transmission experiment

Abstract

SUMMARY F4+Escherichia coli is an important agent of post-weaning diarrhoea in piglets. Piglets that express an adhesion site for F4+ E. coli in their small intestine (F4R+) shed higher numbers of F4+ E. coli than piglets lacking this site (F4Rx). We hypothesized that F4R+ piglets are more infectious and more susceptible for F4+ E. coli. This implies that in populations with F4R+ and F4Rx piglets, the transmission would be dependent on the frequency of both types of animals. To quantify the difference in infectiousness and susceptibility, a one-to-one transmission experiment was performed with 20 pairs consisting of one inoculated and one contact piglet. Based on the contact infections observed, transmission parameters were estimated with generalized linear models. F4R+ piglets were infectious for other piglets and the reproduction ratio (R 0 ) for homogeneous F4R+ populations, that is the average number of secondary infections that one F4R+ pig will cause during its entire infectious period in a population of susceptible F4R+ individuals only, was estimated as 7 . 1. F4R+ piglets were more susceptible than F4Rx piglets and reducing the fraction of F4R+ piglets of a population will reduce transmission. It was calculated that in order to prevent major outbreaks of F4+ E. coli (R 0 <1), the fraction of F4R+ piglets must be lower than 0 . 14.

Transmission of F4+ E. coli in groups of early weaned piglets

“…F4R+ piglets were more susceptible to F4+ E. coli infection than F4Rx piglets, but were not more infectious. This confirms and completes the findings of a one-to-one transmission experiment [12] in which susceptibility was found to differ, but which was inconclusive on the infectiousness as none of the inoculated F4Rx piglets became infectious. In the current study, six F4Rx piglets did become infectious, four inoculated and two contact piglets.…”

“…Results of a one-to-one transmission experiment with F4+ E. coli showed that F4Rx piglets were less susceptible for F4+ E. coli infection than F4R+ piglets [12]. Results of this experiment were inconclusive on whether F4R+ and F4Rx piglets differed in infectiousness, as none of the inoculated F4Rx piglets was infectious, probably due to a low infection pressure.…”

“…In an unpublished study by Geenen et al, a classification rule was determined by principal components analysis (PCA) to distinguish between high and low shedders. High shedding is associated with piglets being infectious [12]. All piglets of which the sum: g coefficient ln cfu k* (ln cfu k xm ln cfu k ), with k=day 1, 2, …, 8 is smaller than 1 .…”

“…High shedders ' (see also ' Determination of shedding type ' section above) were assumed to be infectious as this was found to be highly associated with the occurrence of cases in a one-to-one transmission experiment [12]. Since S, I, N and C are measured daily from the transmission experiment, we may drop Dt, being the unit of time, from the equation above, without loss of generality.…”

Persistence and Spread of Gastro-Intestinal Infections: the Case of Enterotoxigenic Escherichia coli in Piglets

“…F 4+E-coli can attach to the microvilli of the small intestine enterocytes, where they produce enterotoxins. These toxins affect the enterocytes and cause increased secretion of fluid, leading to diarrhoea, dehydration, acidosis, or in some cases, even to death (Geenen, 2005;Geenen et al, 2004Geenen et al, , 2007. To this day, several empirical studies have investigated how the occurrence of clinical symptoms depends on environmental factors, such as weaning age, diet composition, temperature or litter size Carstensen et al, 2005;Pluske et al, 2007;Wellock et al, 2006), or the genetic aspects of intestinal infections (Melin et al, 2004;Zhang et al, 2007).…”