Enterocecocolitis associated with intraepithelial Campylobacter-like bacteria in rabbits (Oryctolagus cuniculus)

CAMPYLOBACTER HYOINTESTINALIS ISOLATION FROM HOWLER (ALOUATTA CARAYA) AND SPIDER MONKEYS (ATELES FUSCICEPS ROBUSTUS) AT A ZOOLOGIC FACILITY IN CENTRAL ILLINOIS

Campylobacter hyointestinalis was initially isolated from an asymptomatic black howler monkey (Alouatta caraya) in a routine fecal culture examination. Fecal cultures from other individuals in this group and an adjacently housed black-headed spider monkey (Ateles fusciceps robustus) group recovered C. hyointestinalis from all but one of the individuals sampled (1.1 spider monkeys and 2.1 howler monkeys). Concurrently, one spider monkey presented with acute onset severe rectal prolapse and diarrhea. Whole-genome sequencing results of C. hyointestinalis isolates from all individuals were homologous and closely related to Campylobacter hyointestinalis subsp. hyointestinalis TTU_618, a strain typically associated with environmental samples. In addition, two cytolethal distending toxin (CDT) expressing gene clusters, cdt-I and cdt-II, were identified in all isolates. These results suggest C. hyointestinalis is transmissible to both howler monkeys and spider monkeys, though the origin of infection and whether it is transmissible between these species is undetermined.

Prevalence and associated risk factors for Lawsonia intracellularis infection in farmed rabbits: A serological and molecular cross-sectional study in South Korea

Lawsonia intracellularis is the etiological agent of proliferative enteropathy, which is globally considered an important enteric disease in pigs and horses. Experimental studies suggest that the organism spreads by subclinical infection of many animals, including rabbits. Despite the importance of rabbits in the epidemiology of L. intracellularis, the extent of exposure to L. intracellularis in the rabbit population is poorly defined and remains unclear. The objective of this cross-sectional study was to investigate the seroprevalence and shedding of L. intracellularis in farmed rabbits. Furthermore, we aimed to identify risk factors associated with seropositivity. Sera from the rabbits were used to measure L. intracellularis-specific antibodies by immunoperoxidase monolayer assay, and rectal swabs were used to detect L. intracellularis DNA using a real-time PCR assay. Antibodies against L. intracellularis were detected in 12.3% of farms (20/163) and 6.3% of rabbits (49/774). Lawsonia intracellularis DNA in rectal swabs was detected in 3.8% of farms (6/156) and 1.2% of rabbits (8/667). The risk factor analysis showed that the presence of pigs or horses on the farm or the neighboring farm was associated with an increase in the risk of seropositivity (p < 0.05). We observed significantly increased odds of positivity for L. intracellularis in rabbits with a history of digestive trouble (diarrhea) on the farm during the 3 months before the samples were obtained (p < 0.05). Collectively, these findings demonstrated that L. intracellularis infection was evident among farmed rabbits and that rabbits might serve as an important reservoir for L. intracellularis epidemiology.

Chimeric hemagglutinin supra-seasonal universal influenza vaccine candidates administered sequentially by the intramuscular route are locally and systemically well-tolerated in rabbits

Sequential intramuscular immunization with chimeric hemagglutinins (cHA) composed of the same conserved HA stalk domain and distinct HA heads is a proposed strategy to produce a supra-seasonal universal influenza vaccine. To evaluate the local tolerance and the local and systemic effects of this strategy, two studies were performed in rabbits. In the first study, two different split virion monovalent cHA vaccines, containing cH5/1N1 and cH8/1N1, with or without AS01 or AS03, were injected at a two-week interval. In the second study, animals were given these vaccines and two weeks later an additional dose of split virion monovalent cHA vaccine containing cH11/1N1, with or without AS01 or AS03. General health status, rectal temperature, local tolerance, ophthalmology, hematology, coagulation, and blood chemistry parameters were monitored. Macroscopic and microscopic evaluations were performed three days after the last dose and after a treatment-free recovery period. The treatment-related changes included body weight loss and food consumption decrease, increases in neutrophil count, C-reactive protein and fibrinogen levels. Microscopic signs of inflammation at the injection sites and immune stimulation of the draining lymph nodes and spleen were also noticed. Most post-injection findings could be linked to the transient inflammation due to the establishment of the desired vaccine-elicited immune response, and were mainly observed in the adjuvanted groups. In conclusion, the sequential administration of different cHA vaccines was locally and systemically well-tolerated in rabbits.

Preparation and Characterization of Polyclonal and Monoclonal Antibodies against Lawsonia Intracellularis

Proliferative enteropathy is an intestinal infectious disease caused by the obligate intracellular bacterium Lawsonia intracellularis. Immunohistochemistry staining has superior sensitivity over hematoxylin and eosin and silver staining for detecting L. intracellularis in histological sections. A L. intracellularis—specific monoclonal antibody (MAb) produced in the UK (IG4 MAb) has been described in the literature. However, no monoclonal or polyclonal antibodies are commercially available. Therefore, the objective of this study was to produce and characterize new polyclonal and monoclonal antibodies against L. intracellularis that are suitable for diagnostic use. The new monoclonal (2001 MAb) and polyclonal antibodies (1999 PAb) were compared with the IG4 MAb using Western blot analysis of outer membrane proteins (OMPs) of 6 L. intracellularis isolates, Bilophila wadsworthia and Brachyspira hyodysenteriae and using immunohistochemistry of known positive and negative histologic samples and pure cultures of L. intracellularis, B. wadsworthia, B. hyodysenteriae, Salmonella choleraesuis, S. typhimurium, and Escherichia coli K88. Immunogold staining using 2001 MAb was performed to show the specificity of the antibody against an L. intracellularis surface protein. Western blot analysis showed that the 2001 MAb targeted an OMP of 77 kD, which made it different from the IG4 MAb that targeted an 18-kD OMP. The immunogold stain demonstrated the specificity of the 2001 MAb to a surface protein of L. intracellularis. The polyclonal antibody (1999 PAb) targeted 5 OMPs (77, 69, 54, 42, and 36 kD). Both the 2001 MAb and 1999 PAb stained known positive, but not negative, histologic samples. Both the 2001 MAb and 1999 PAb reacted with a pure culture of L. intracellularis but not with any other common enteric pathogens. These two new antibodies will be useful for immunodiagnosis of L. intracellularis.

Biology and Diseases of Rabbits

Beginning in 1931, an inbred rabbit colony was developed at the Phipps Institute for the Study, Treatment and Prevention of Tuberculosis at the University of Pennsylvania. This colony was used to study natural resistance to infection with tuberculosis (Robertson et al., 1966). Other inbred colonies or well-defined breeding colonies were also developed at the University of Illinois College of Medicine Center for Genetics, the Laboratories of the International Health Division of The Rockefeller Foundation, the University of Utrecht in the Netherlands, and Jackson Laboratories. These colonies were moved or closed in the years to follow. Since 1973, the U.S. Department of Agriculture has reported the total number of certain species of animals used by registered research facilities (1997). In 1973, 447,570 rabbits were used in research. There has been an overall decrease in numbers of rabbits used. This decreasing trend started in the mid-1990s. In 2010, 210,172 rabbits were used in research. Despite the overall drop in the number used in research, the rabbit is still a valuable model and tool for many disciplines.

Recent Advances in Understanding the Pathogenesis of Lawsonia intracellularis Infections

Proliferative enteropathy is an infectious disease caused by an obligate intracellular bacterium, Lawsonia intracellularis, and characterized by thickening of the intestinal epithelium due to enterocyte proliferation. The disease is endemic in swine herds and has been occasionally reported in various other species. Furthermore, outbreaks among foals began to be reported on breeding farms worldwide within the past 5 years. Cell proliferation is directly associated with bacterial infection and replication in the intestinal epithelium. As a result, mild to severe diarrhea is the major clinical sign described in infected animals. The dynamics of L. intracellularis infection in vitro and in vivo have been well characterized, but little is known about the genetic basis for the pathogenesis or ecology of this organism. The present review focuses on the recent advances regarding the pathogenesis and host-pathogen interaction of L. intracellularis infections.

Proliferative enteropathy involving Lawsonia intracellularis infection in rabbits (Oryctlagus cuniculus)

Five rabbits suffering from diarrhea were diagnosed with proliferative enteropathy (PE). Histopathology revealed a thickened mucosa consisting of hyperplastic intestinal epithelium and infiltration of inflammatory cells mainly consisted of macrophages. In the affected epithelial cytoplasm, numerous curved bacillus-like organisms were observed in the Warthin-Starry silver stain and electron microscopy observation. In polymerase chain reactions, Lawsonia intracellularis-specific DNA fragment were amplified from affected ileal tissue extracted DNA in each case and present 5 cases were confirmed to be L. intracellularis infection. Serum collected from the affected rabbit was immunohistochemically reactive with L. intracellularis in tissue sections from pigs with porcine proliferative enteropathy, as well as with tissue sections from the five affected rabbits. Thus, serum obtained from the affected rabbit may be applicable to immunohistochemical detection for L. intracellularis infection in other species.

Infection of different strains of mice with Lawsonia intracellularis derived from rabbit or porcine proliferative enteropathy

This report describes intestinal lesions in five strains of mice infected orally with Lawsonia intracellularis-infected tissue homogenates from rabbits or pigs (RLI and PLI). BALB/cA, C3H/HeJ, C57BL/6J and ICR mice were susceptible to infection with RLI, whereas only C3H/HeJ, C57BL/6J and ICR strains were susceptible to PLI. In susceptible mice, crypt epithelial hyperplasia occurred in association with an inflammatory reaction, as in proliferative enteropathy (PE) in other species. The intestinal changes in the infected mice varied from mild to severe. Unlike rabbit or porcine PE, in which the changes are confined to the ileum, the lesions in mice were located in the caecum. Immunolabelling of L. intracellularis antigen was abundant in early infection when the epithelial hyperplasia was mild or absent. When the hyperplasia had become severe, however, immunolabelling was weak. For this reason, it is suggested that transitory infection of the epithelium induces epithelial hyperplasia. Genetic differences between mouse strains appeared to play an important role in the response to L. intracellularis infection. Moreover, the susceptibility of BALB/cA mice to RLI but not to PLI suggests that there are significant biological differences between L. intracellularis isolates from rabbit PE and porcine PE.

Gamma interferon influences intestinal epithelial hyperplasia caused by Lawsonia intracellularis infection in mice

Lawsonia intracellularis is a recently identified bacterial pathogen which causes disease in a broad range of animals. Invasion of intestinal epithelial cells and the resultant hyperplasia of infected cells are central processes in disease pathogenesis. In this study, we aimed to establish whether immunocompetent mice were susceptible to infection and whether gamma interferon (IFN-gamma) contributed to the pathogenesis of infection. Wild-type 129-Sv-Ev mice (129 mice) and IFN-gamma receptor knockout mice based on the 129 background (IFN-gammaR(-)) were challenged orally with approximately 5.5 x 10(7) L. intracellularis cells. Both 129 and IFN-gammaR(-) mice became infected, although the extent of infection (as determined by the proportion of infected crypts) was substantially lower in 129 mice than in IFN-gammaR(-) mice. Despite these differences, infected crypts showed characteristics typical of proliferative enteropathies of other animals, i.e., intracellular colonization of epithelial cells by L. intracellularis with resultant epithelial hyperplasia. Infection in 129 mice was cleared between days 21 and 28 postchallenge, whereas infection in IFN-gammaR(-) mice was evident in 100% of animals from day 21 onward. Additionally, in IFN-gammaR(-) mice the infection was so extensive that fatalities resulted. IFN-gamma therefore plays a significant role in limiting intracellular infection and increased cellular proliferation associated with L. intracellularis. L. intracellularis infection is generally associated with modest cellular infiltration; therefore, further comparative examinations will be necessary to determine pathogenicity factors and define the role of IFN-gamma in controlling this infection.

Subclinical proliferative enteropathy in sentinel rabbits associated with Lawsonia intracellularis

Light microscopic and ultrastructural changes of naturally acquired proliferative enteropathy were observed in two of three young sentinel New Zealand White rabbits. The etiologic agent, Lawsonia intracellularis, was demonstrated in the tissues using morphologic, immunohistochemical, and molecular methods. Proliferative enteropathy was associated with infection of villous and crypt enterocytes by intracellular organisms genotypically and antigenically related to L. intracellularis of various other animal species.

Proliferative enterocolitis associated with dual infection with enteropathogenic Escherichia coli and Lawsonia intracellularis in rabbits

Both enteropathogenic Escherichia coli (EPEC) and an obligate intracellular bacterium, previously referred to as an intracellular Campylobacter-like organism and now designated Lawsonia intracellularis, have been reported as causes of enterocolitis in rabbits. An outbreak of enterocolitis in a group of rabbits, characterized by an unusually high rate of mortality, was found to be associated with dual infection with EPEC and L. intracellularis. The EPEC strain was found to have eaeA gene homology but was negative for afrA homology. The absence of the afrA gene, which encodes the structural subunit for the AF/R1 pilus, indicates that this rabbit EPEC strain is distinct from the prototypic RDEC-1 strain. This finding suggests that rabbit EPEC strains widely reported in Western Europe, which lack AF/R1 pili, are also present in rabbits in the United States. Dual infection with these two pathogens in rabbits has not been previously reported and may have contributed to the unusually high mortality observed in this outbreak.

Intracellular Campylobacter-like organisms associated with rectal prolapse and proliferative enteroproctitis in emus (Dromaius novaehollandiae)

Rectal prolapse was the presenting clinical finding in a group of juvenile emus (Dromaius novaehollandiae). Gross findings included severely thickened and rugose distal rectal mucosae. Histologically, there were thickened villi, enterocyte hyperplasia, dilated glands filled with mucus and heterophils, and a dense infiltrate of heterophils, macrophages, lymphocytes, and plasma cells in the lamina propria. Examination of Warthin-Starry silver-stained sections revealed numerous apically located comma-shaped intracytoplasmic bacteria approximately 1 x 3 microns in size. Campylobacter-like organisms morphologically compatible with ileal symbiont intracellularis now known as Lawsonia intracellularis were seen via electron microscopy. Bacteria were further characterized by indirect immunofluorescence using monoclonal antibody specific for the 25-27-kd outer membrane protein of L. intracellularis.

Alimentary and respiratory tract lesions in eight medically fragile Holstein cattle with bovine leukocyte adhesion deficiency (BLAD)

Lesions in the alimentary tract were studied in eight medically fragile Holstein cattle homozygous for the bovine leukocyte adhesion deficiency (BLAD) allele as determined by polymerase chain reaction and restriction endonuclease analysis. These cattle received institutional medical care but died or were euthanatized because of chronic debilitation associated with diarrhea (6/8) and pneumonia (4/8). The six cattle with diarrhea had acute (n = 3) or chronic (n = 3) intestinal ulcers, but the other two remained relatively healthy for 3 years and did not develop intestinal tract ulcers. Ulcerated areas were present in the small intestine in six animals, and two of these also had ulcers in the large intestine. Ulcers were covered by thick exudates that, in chronic lesions, partially occluded the intestinal lumen. Intramural and serosal fibrosis also contributed to lumen constriction. Pseudomonas aeruginosa was isolated from the intestine of four cattle. Bovine viral disease virus and Salmonella were not isolated from the five cattle that were tested. Respiratory tract lesions consisted of dense infiltrates of neutrophils in bronchi, bronchioles, and alveoli. This study suggests that intestinal lesions are integral to the demise of BLAD cattle that receive intensive medical care and that neutrophils do infiltrate the lung and enter airway lumina, despite the adhesion deficiency.

Intracellular Campylobacter-like organism from ferrets and hamsters with proliferative bowel disease is a Desulfovibrio sp

Proliferative bowel disease is an intestinal disorder of a variety of domestic animals associated with the presence of an intracellular Campylobacter-like organism (ICLO). We have identified the ICLO obtained from a ferret with proliferative colitis by 16S rRNA sequence analysis. In this ferret, proliferative bowel tissue containing the ICLO had translocated to the mesenteric lymph nodes, omentum, and liver. The 16S rRNA genes of the ICLO were amplified from an infected fragment of extraintestinal tissue by using universal prokaryotic primers. Approximately 1,480 bases of the amplified 16S rRNA gene were sequenced by cycle sequencing. Comparison of the sequence of the ICLO with those of over 400 bacteria in our data base indicated that the sequence of the ICLO was most closely related to that of Desulfovibrio desulfuricans (87.5% similarity). Phylogenetic analysis with 12 Desulfovibrio species and 20 species from related genera placed the ICLO in a subcluster within the genus Desulfovibrio with D. desulfuricans and 5 other Desulfovibrio species. We will refer to this organism as the intracellular Desulfovibrio organism (IDO). Specific primers were produced for PCR amplification of a 550-base fragment of the 16S rRNA gene of the IDO in proliferative intestinal tissue samples. This unique 550-base segment was amplified from samples of frozen intestinal tissue from nine ferrets and three hamsters with ICLO-associated disease but not in four intestinal tissue samples from animals without the ICLO-associated disease. The 550-base amplified products from the bowel tissues of one hamster and one ferret were fully sequenced. The ferret IDO partial sequence was identical to the previously determined 16S rRNA sequence over its length, and the hamster IDO sequence differed by a single base. The same intracellular organism has been identified in proliferative intestinal tissues of swine and that the organism has been successfully maintained in tissue culture. The availability of specific primers for PCR-based detection of this intracellular Desulfovibrio organism will aid in the determination of its role in the pathogenesis of proliferative bowel disease in a variety of infected hosts.

Intracellular bacteria of porcine proliferative enteropathy: cultivation and maintenance in vitro

An obligate intracellular bacterium was isolated from the intestines of all 10 cases of porcine proliferative enteropathy from four different pig farms. The organism grew in a rat enterocyte cell line (IEC-18) and was maintained over 20 passages. The growth of the bacteria was assessed by immunostaining of cells exposed to infection. Infection was not associated with morphological cell change, and growth was confined to cells infected at the time of each transfer of infection and the progeny of these cells. The bacterium is a microaerophilic, cell dependent, curved or rod-shaped, gram-negative bacillus that multiplies freely in the enterocyte cytoplasm. Cell cultures containing the intracellular bacteria appear to be free of other microorganisms, including chlamydiae and viruses.