Evaluation of the involvement of mice (Mus musculus) in the epidemiology of porcine proliferative enteropathy.

The aim of this study was to evaluate the fecal-oral transmission of L. intracellularis between mice and pigs. The study was divided into two parts. The first part aimed to determine whether mice could be infected by feces from pigs that are experimentally infected with L. intracellularis. Thirty-four Swiss mice received L. intracellularis PCR-positive feces from experimentally infected pigs (M1) for four consecutive days. Twelve other mice received swine negative feces (M2). Pools of mice feces were collected on alternating days post-exposure (dpe). The second part of the study aimed to test whether pigs could be infected when exposed to L. intracellularis PCR-positive feces from experimentally infected mice. Twelve 5-week-old pigs received feed mixed with L. intracellularis PCR-positive mice feces (P1), while the other two pigs received PCR-negative mice feces (P2) for four consecutive days. In the first study, the amount of L. intracellularis provided to M1 boxes per day was between 106 and 108. Mice shed, an average of 104 bacterial units every collection day. Three mice from M1 were positive for L. intracellularis by immunohistochemistry (IHC) at the end of the study. In the second part of the study, pigs in P1 received an average of 105 bacterial units per day. Ten pigs were infected by L. intracellularis based on positive qPCR and/or immunohistochemistry and serology results. These pigs shed an average of 104L. intracellularis/g of feces. Mice and pigs experimentally infected with L. intracellularis can infect each other, therefore, rodents should be considered players in the epidemiology of this disease in pig farms.

Transmission of Lawsonia intracellularis to weanling foals using feces from experimentally infected rabbits.

The aim of this study was to investigate whether feces from rabbits experimentally infected with Lawsonia intracellularis were infectious to foals. Two rabbits were infected with L. intracellularis, while two rabbits served as controls. Eight foals received daily feces from either the infected or the control rabbits. All rabbits and foals were monitored daily for clinical signs for the entire study period (21days for rabbits, 42days for foals). Feces and blood were collected for the PCR detection of L. intracellularis and serologic analysis, respectively. None of the infected rabbits or foals developed clinical signs compatible with proliferative enteropathy. All infected rabbits and foals shed L. intracellularis in their feces and all seroconverted. The results support the role of rabbits as asymptomatic amplifiers of L. intracellularis and their role as sources of infection for susceptible foals.

Further investigation of exposure to Lawsonia intracellularis in wild and feral animals captured on horse properties with equine proliferative enteropathy.

This study investigated the exposure to Lawsonia intracellularis in wild birds, mice, rabbits, raccoons, coyotes and squirrels, and feral cats and pigs on 10 farms with confirmed equine proliferative enteropathy (EPE). Serum samples from all resident foals (417 samples) as well as fecal (461) and serum (106) samples from wild and feral animals were collected for serological and molecular detection of L. intracellularis following the diagnosis of EPE in index cases. A total of three cats from two farms, three mice from two farms and eight cottontail rabbits from one farm had evidence of prior exposure to L. intracellularis. These animals may be an indicator of environmental exposure or may be actively involved in the transmission of L. intracellularis to foals by acting as a potential reservoir/amplifier host.

Monitoring of Lawsonia intracellularis in breeding herd gilts.

In modern pig production, proliferative enteropathy is a common cause of diarrhoea and poor growth in young animals. This study aimed to determine the possible spread of Lawsonia intracellularis through the sale of replacement gilts and the possibility to protect the herds by adequate biosecurity measures. This was achieved by repeated sampling of 50 gilts in an infected multiplying herd, from the last day in the farrowing pen and until sale. Further, 60 gilts sold from this herd were tested during their stay in quarantine in a recipient herd. To confirm freedom from infection, 100 growing pigs in the recipient herd were also tested. Individual faecal (n=748) and blood (n=728) samples were analysed by PCR and ELISA, respectively. Transmission of L. intracellularis from the sows to their offspring was not demonstrated. However, the possible transmission between herds by replacement gilts was demonstrated. Peak shedding occurred at 12 and 15 weeks of age, and single animals were also PCR-positive at 24-36 weeks of age in the multiplying herd and in the quarantine in the recipient herd. Further, the possible occurrence of chronically infected carrier animals was suggested. Although L. intracellularis is widely spread, it appears possible to avoid the transmission between herds by employing adequate biosecurity measures. Thus, it would be advisable to establish herd profiles in breeding herds to avoid the selling of infected animals as well as to establish the health status of the recipient herd. Further, the health status of the recipient herds should be known.

Detection of Lawsonia intracellularis by real-time PCR in the feces of free-living animals from equine farms with documented occurrence of equine proliferative enteropathy.

The objective of this study was to determine whether Lawsonia intracellularis was present in the feces of free-living animals collected on two equine premises with documented occurrence of equine proliferative enteropathy (EPE). Fresh feces from black-tailed jackrabbits (Lepus californicus, n=100), striped skunks (Mephitis mephitis, n=22), feral cats (Felis catus, n=14), Brewer's Blackbirds (Euphagus cyanocephalus, n=10), Virginian opossums (Didelphis virginiana, n=9), raccoons (Procyon lotor, n=4), California ground squirrels (Spermophilus beecheyi, n=3), and coyotes (Canis latrans, n=2) were collected from August 2006 to January 2007 either from the ground while walking the premises or after trapping the animals using live traps. Nucleic acid purified from feces was directly processed for polymerase chain reaction (PCR) analysis using a real-time PCR assay targeting the aspartate ammonia lyase gene of L. intracellularis. Purified DNA samples were also precipitated, preamplified for L. intracellularis, and analyzed using the same real-time PCR assay, to increase the detection limit to one L. intracellularis organism per extracted sample. Feces from jackrabbits, striped skunks, Virginian opossums, and coyotes tested PCR positive for L. intracellularis, whereas all feces from feral cats, Brewer's Blackbirds, raccoons, and ground squirrels tested PCR negative for L. intracellularis. PCR testing on DNA extracted directly from feces was positive for L. intracellularis in six of 164 fecal samples. When DNA purification from feces was followed by a precipitation and preamplification step, five additional fecal samples tested PCR positive for L. intracellularis (11/164). The largest number of PCR positive L. intracellularis fecal samples was observed in striped skunks, followed by Virginian opossums, jackrabbits, and coyotes. This is the first description of L. intracellularis in these four species. Because the fecal samples were collected at equine farms with confirmed cases of EPE, striped skunks, Virginian opossums, jackrabbits, and coyotes may act as potential sources of infection to susceptible weanlings.

An outbreak of Lawsonia intracellularis infection in a standardbred herd in Ontario.

An outbreak of protein-losing enteropathy associated with Lawsonia intracelluaris infection was diagnosed in 6 standardbred foals from a farm in Ontario. Wildlife exposure may have been involved in the perpetuation of disease in this outbreak. The clinical presentation, treatment, outcomes, and pathological findings are described.

A Lawsonia intracellularis transmission study using a pure culture inoculated seeder-pig sentinel model.

Transmission of Lawsonia intracellularis from experimentally inoculated pigs to naive swine was demonstrated in this study. The study was conducted using conventional pigs divided into three groups as follows: principles inoculated with L. intracellularis, sentinels, and controls. The pigs were inoculated and paired on 13 and 9 days post-inoculation with a sentinel pig for 7 days. Fecal samples and serum samples were collected throughout the study for polymerase chain reaction (PCR) and antibody testing by indirect fluorescent antibody techniques. After co-mingling, the inoculated group was necropsied; sentinel and control pigs were necropsied 7-14 days later. The intestinal tracts were evaluated grossly and microscopically for lesions. PCR was performed on intestinal mucosal scrapings and feces. Warthin-Starry and fluorescent antibody staining procedures were conducted to confirm colonization with L. intracellularis. Gross and microscopic lesions typical of porcine proliferative enteropathy (PPE) were observed in both the inoculated and sentinel groups. Transmission was demonstrated from inoculated principle pigs to sentinel pigs. PCR results detected cyclical shedding of L. intracellularis in the feces. Seroconversion occurred in pigs that were exposed to L. intracellularis. From this study, it was demonstrated that transmission of L. intracellularis can occur easily in an environment with experimentally infected pigs and that PCR can be a useful tool to monitor fecal shedding of the organism.