Evidence of host adaptation in Lawsonia intracellularis infections

Abstract

Background: Lawsonia intracellularis is the causative agent of proliferative enteropathy, an endemic disease in pigs and an emerging concern in horses. Enterocyte hyperplasia is a common lesion in every case but there are differences regarding clinical and pathological presentations among affected species. We hypothesize that host susceptibility to L. intracellularis infection depends on the species of origin of the bacterial isolate. The objective of this study was to evaluate the susceptibilities of pigs and horses to L. intracellularis infection using either a porcine or an equine isolate. Materials and methods: Twelve foals and eighteen pigs were equally divided into three groups and infected with either a porcine or an equine isolate (10 9 L. Intracellularis/challenged animal), and a saline solution (negative control group). The animals were monitored regarding clinical signs, average of daily weight gain, fecal shedding of the bacteria by PCR and humoral serological response. Results: Foals infected with the equine isolate developed moderate to severe clinical signs and maintained a lower average of weight gain compared to control foals. Fecal quantitative PCR in equine isolate-infected foals revealed higher amounts of bacterial DNA associated with longer duration of shedding compared with porcine isolateinfected foals. All four foals infected with the equine isolate demonstrated higher IgG titers in the serum compared with porcine isolate-infected foals. In the pig trial, diarrhea and seroconversion were only observed in animals infected with the porcine isolate. Pathological changes typical of proliferative enteropathy were observed in the necropsied foal infected with equine isolate and in the two necropsied pigs infected with the porcine isolate. Conclusions: Evident clinical signs, longer periods of bacterial shedding and stronger serologic immune responses were observed in animals infected with species-specific isolates. These results show that host susceptibility is driven by the origin of the isolated L. intracellularis strain.

Equine proliferative enteropathy on a Brazilian farm

“…Reported clinical signs and macro-and microscopic findings, all consistent with the literature (Lester 2001, Pusterla et al 2010, Vannucci et al 2012) associated with positive immune staining for Lawsonia intracellularis allowed us to reach the diagnosis of equine proliferative enteropathy (EPE). Unlike pigs, in which lesions and immunostaining are more highly concentrated in the final third of the small intestine, in horses, these lesions can also be found in the duodenum, as reported in this case.…”

“…Al-Ghamdi et al (2012) reproduced proliferative enteropathy (EP) in 2-month-old foals using a pure culture of L. intracellularis and intestinal mucosa homogenates obtained from experimentally infected pigs. However, Vannucci et al (2012) did not observe the same results, as pigs infected with equine isolated and foals infected with L. intracellularis isolated from pigs showed no clinical signs, decline in performance, pathological changes or hypoproteinemia, suggesting adaptation to the host.…”

“…The lesions of the large intestine are less frequent, but in our case, histologic lesions compatible with EPE were found in the large intestine. The ages of affected animals ranged from a few days to 21 months of age, although diarrhea associated with hypoproteinemia and submandibular edema had been observed more frequently in foals 3 to 6 months old, an age group in which animals are more susceptible to and affected by L. intracellularis (Pusterla et al 2010, Vannucci et al 2012). This predisposition is most likely associated with the decline of maternal antibodies (Pusterla et al 2008a), as well as stressors such as weaning, moving to new paddocks and barns, deworming and/ or vaccination programs and/or early conditioning programs (Frazer 2008), which were performed at this farm.…”

“…This antimicrobial is not effective in the treatment of EPE (Schumacher et al 2000, Vannucci et al 2012, Wuersch et al 2006) because its active property has a high minimum inhibitory concentration (MIC) for L. intracellularis (McOrist et al 1995). In animals with hypoproteinemia, erythromycin doses were followed by clinical improvement in some infected animals, and treatment with erythromycin was effective for EPE in other reports (Bihr 2003, Lavoie et al 2000, Schumacher et al 2000 and is generally considered the drug of choice for the treatments of suspected cases.…”

Infection of sparrows (Passer domesticus) and different mice strains with Lawsonia intracellularis

“…Guedes and Gebhart (2003c), using monoclonal antibodies (MAbs 2001 and IG4 MAbs) and one polyclonal antibody (1999 PABs) for L. intracellularis, demonstrated through Western blot analysis that all L. intracellularis isolates, except one strain from a hamster, showed reactivity for all antibodies; which may indicate some difference in outer membrane proteins of the hamster isolate. Vanucci et al (2012) demonstrated evidences of host adaptation in L. intracellularis infections in swine and horses. In their study strong lesions and clinical signs were observed when the animals were challenged with an inoculum species specific.…”