In the past five years generally well managed farms reported an increase in acute deaths in their grower herds to their consulting veterinarian. At the same time reports from across the world indicated that this is not a problem seen only in South Africa. The syndrome is generally referred to as haemorrhagic bowel syndrome (HBS), red gut or balloon pig. Veterinarians generally believed that the cause of these acute deaths were due to the acute form of Lawsonia intracellularis, also known as porcine haemorrhagic enteropathy (PHE). Because neither the clinical symptoms present prior to death, nor the post mortem changes were typical for a L. intracellularis case it was decided to investigate this syndrome in more depth. Five commercial farms were purposefully selected where growers that died peracutely were necropsied and intestinal samples collected for histological as well as bacteriological examination. A total of 28 pigs were sampled with the histological sections from all samples indicating a Clostridium species as the cause and from 11 of samples Clostridium perfringens were cultured as the predominant bacterium. Although pigs on the farms were seropositive for Lawsonia intracellularis there was no evidence that this bacterium was the cause of death in the pigs. Rather the aetiology points to C. perfringens being the cause, possibly together with other predisposing factors such as rapid growth, high ambient temperatures and interruption in fedding patterns. Based on these results further studies to determine the toxin type as well as predisposing factors should be done. Copyright / Gedurende die afgelope vyf jaar het plase met ’n algemene goeie bestuur ’n verhoging in akute vrektes in hulle groeikuddes opgemerk en hulle het hulle kommer oor die vrektes aan hulle konsulterende veeartse oorgedra. Diè verhoging in groeivrektes is nie uniek aan Suid Afrika nie. Dieselfde tendens is regoor die wêreld opgemerk, maar niemand is seker wat presies die oorsaak van die akute vrektes is nie. In die literatuur word daar na “haemorrhagic bowel syndrome (HBS)” oftewel hemoragiese derm sindroom verwys. Boere verwys na die sindroom as rooiderm of “balloon pig”. Tot nou toe het veeartse aanvaar dat die oorsaak moontlik Lawsonia intracellularis is. Die organisme is verantwoordelik vir ’n groep sindrome waarvan “porcine haemorrhagic enteropathy” die akute form is. Omrede die kliniese simptome en die nadoodse ondersoek nie tipies vir ’n L. Intracellularis geval is nie, is daar besluit om die akute vrektes verder te ondersoek. Vyf plase, waar die sindroom baie voorkom, is geidentifiseer en dermonsters is geneem vir histopatalogiese sowel as mikrobiologiese ondersoeke. In totaal is monsters van 28 varke geneem. Die histologies seksies van al die monsters het gedui op ’n Clostridium spesie as die hoofoorsaak van vrekte en Clostridium perfringens is uit 11 van die monsters geisoleer. Alhoewel al 5 plase serologies positief getoets is vir Lawsonia intracellularis, was daar geen bewyse gewees dat die bakterium verantwoordelik vir die vrektes was nie. Die etiologie dui eerder op C. perfringens as die oorsaak. Daarby saam speel ander faktore soos vinnige groei, hoë omgewingstemperature asook onderbrekings in beskikbaarheid van voer heelwaarskynlkik ’n belangrike rol in die sindroom. Verdere navorsing om die toksien tipe te identifiseer asook die identifikasie van moontlike faktore wat die sindroom aanhelp moet gedoen word. / Dissertation (MMEdVet)--University of Pretoria, 2009. / Production Animal Studies / unrestricted

Lawsonia intracellularis and the disease it causes in horses, equine proliferative enteropathy (EPE), is an emerging pathogen of increasing importance to the horse industry from both an economic and welfare standpoint. Long recognized as an economically important disease of swine, the hallmark of EPE is a protein-losing enteropathy, where affected horses suffer weight loss and some ultimately succumb to the disease despite aggressive treatment. There are currently no known EPE preventative measures and the epidemiology of the disease remains poorly defined. While EPE is a sporadic disease affecting less than 25% of exposed horses, some farms experience clinical cases year after year. Further, weanlings are uniquely susceptible to this disease, although no conclusive reason for this predisposition has been identified. The overall hypothesis is that the host immune response plays a significant role in the susceptibility of weanlings to L. intracellularis infection and the occurrence of clinical equine proliferative enteropathy. To test this hypothesis, four individual hypotheses were proposed: (H1) previous farm history of EPE does not have an effect on weanling seroprevalence, (H2) passively-acquired antibodies do not have an effect on susceptibility to L. intracellularis and the occurrence of EPE, (H3) the serological status of mares can be used to determine the role they play in the epidemiology of EPE on endemic farms, and (H4) L. intracellularis-specific IFN-g expression is not associated with increased resistance to EPE.