Jill R. Thomson

Investigations into field cases of porcine colitis with particular reference to infection with Serpulina pilosicoli.

Investigations into the possible causes of colitis and typhlocolitis were carried out on 85 pig units in the United Kingdom between 1992 and 1996. Serpulina pilosicoli was identified most commonly, occurring as the suggested primary agent on 21 (25 per cent) of the units but forming part of mixed infections on another 23 (27 per cent) of the units, the main co-infections being Yersinia pseudotuberculosis (eight units), proliferative enteropathy (six units), Salmonella species (four units) or Serpulina hyodysenteriae (two units). ‘Atypical’ Serpulina species, S hyodysenteriae, Salmonella typhimurium, Y pseudotuberculosis and Lawsonia intracellularis (proliferative enteropathy) were the suggested primary agents on seven, six, four, four and three units, respectively. Various combinations of mixed infections involving the latter organisms and other possibly incidental agents were recorded on another 10 units. Investigations on a further six units failed to detect any recognised pathogens. On units where S pilosicoli was the suggested primary agent, pigs ranging between 20 to 40 kg (eight to 16 weeks of age), but occasionally up to 50 kg, had diarrhoea and grew poorly over a period of two to three weeks. The prevalence was estimated to be between 5 and 15 per cent in affected batches, with a mortality of approximately 1 per cent. The clinical signs usually developed seven to 14 days after the moving and mixing of pigs. At postmortem examination, affected pigs had liquid contents in their colon, which contained accumulations of mucus in some chronic cases. Gross and histological lesions of colitis were prominent in the mid-spiral region of the colon. In mixed infections with Y pseudotuberculosis, Salmonella typhimurium or S hyodysenteriae, lesions were more extensive and affected the caecum as well as the colon. In the colon, lesions of proliferative enteropathy were usually confined to the proximal half of the ascending spiral but mixed infection with S pilosicoli caused more extensive colitis. Mixed infections were reported to prolong the time taken for pigs to recover naturally and to have a more detrimental effect on growth rates than S pilosicoli infection alone. Despite the successful treatment of batches of pigs with tiamulin or lincomycin, S pilosicoli infection persisted as a chronic problem on many units, with diarrhoea and colitis in successive batches of pigs unless prophylactic medication was used.

Immunopathogenesis of experimentally induced proliferative enteropathy in pigs

To characterize the immune response associated with Lawsonia intracellularis infection, twenty-eight, 7-week-old pigs were dosed orally with a pure culture of L. intracellularis. Animals were killed 3, 7, 14, 21, 28, 35, and 42 days postinfection. Light microscopic studies were undertaken to immunophenotype the immunologic response using specific antibodies to T-cell subsets (CD3, CD4, and CD8), B cells, major histocompatibility complex class II, cadherin, and macrophages over the course of time. The results indicate that there is a direct association between the presence of L. intracellularis and reduced T-cell and B-cell numbers. For the first time, this provides evidence of the presence of an immunosuppressive mechanism operating in this disease. Furthermore, macrophage marker studies indicated that macrophages may play a more complex and significant role in the disease process than has been previously reported, with activated macrophages accumulating in infected hyperplastic crypts.

Evidence of Chlamydophila abortus vaccine strain 1B as a possible cause of ovine enzootic abortion.

Chlamydophila abortus, the agent of ovine enzootic abortion (OEA), is a major cause of lamb mortality worldwide. Disease can be controlled through the use of vaccines based on the 1B temperature-sensitive mutant strain of C. abortus. This study investigated suspected OEA cases across Scotland for the presence of the 1B strain by analysis of recently identified unique point mutations (9). Thirty-five cases were C. abortus-positive and 14 came from vaccinated flocks. Analysis of single nucleotide polymorphisms by PCR-RFLP and sequence analysis revealed the presence of point mutations consistent with the presence of the 1B vaccine strain in 5 of these 14 samples. Quantitative real-time PCR revealed comparable numbers of genome copies of the 1B strain in infected placentas to those present following wild-type infection. This study is the first to demonstrate the presence of the 1B vaccine strain in the placentas of OEA cases and suggests a probable causal role in the disease.

Detection of Pasteurella multocida in pigs with porcine dermatitis and nephropathy syndrome.

Comprehensive bacterial cultures were made on samples from 20 pigs that had died of porcine dermatitis and nephropathy syndrome after a short clinical illness. Eleven species of porcine bacterial pathogens and a range of commensal organisms were isolated. Pasteurella multocida was isolated from 16 of the 20 cases but the other pathogens occurred much less commonly. P multocida was isolated from between one and five sites per case and from the tonsils, retropharyngeal lymph node or lungs in 14 of the 16 cases. Immunohistochemical investigations of kidneys from 30 cases of the syndrome (including the 20 cases in the bacteriological study) revealed P multocida-specific staining in 26 of the cases, primarily in the renal tubular epithelial cells of the proximal convoluted tubules, but also in the glomeruli, in lesions of renal vasculitis and in the cytoplasm of interstitial mononuclear cells.

Expression by Lawsonia intracellularis of type III secretion system components during infection

Contact-dependent secretion systems, such as the type III secretion system (T3SS), have been shown to play significant roles in the pathogenicity of many gram-negative bacterial pathogens. Lawsonia intracellularis is a novel, obligate intracellular gram-negative bacterium, which has been identified as the etiological agent of proliferative enteropathies in numerous animal species. Analysis of the genome sequence of the L. intracellularis strain PHE/MN1-00 has revealed the presence of a T3SS secretion system in this bacterium. In this study we aimed to determine whether this important virulence mechanism is also present in L. intracellularis strain LR189/5/83. Using a PCR-based approach, we verified the presence of a genomic region encoding a T3SS. Specifically, a gene highly homologous to the yscN energiser component of the prototypic T3SS of Yersinia spp. was identified and termed lscN. Two further open reading frames (ORFs) contiguous with lscN were also identified: lscO and lscQ, which are also homologues of ORFs within the T3SS of Yersinia spp. To establish whether this T3SS may be functional, expression was monitored directly by RT-PCR and indirectly by detection of serological responses in vaccinated and infected animals. Transcripts for lscN and lscQ were detected and purified rLscQ was recognized by antiserum from infected pigs, indicating expression in vivo during infection. By analogy to other bacteria, this T3SS may be crucial for intracellular development and is likely to play a significant role in the virulence of this unusual pathogen.

Absence of a set of plasmid-encoded genes is predictive of reduced pathogenic potential in Brachyspira hyodysenteriae

The gene content of 14 strains of the intestinal spirochaete Brachyspira hyodysenteriae was compared using a DNA microarray. A consistent difference occurred in a block of four genes on the ~36 Kb plasmid, with these being present in six virulent strains and absent in eight strains with reduced pathogenic potential. These genes encoded a predicted radical S-adenosylmethionine domain protein, a glycosyl transferase group 1-like protein, an NAD dependant epimerase and a dTDP-4-dehydrorhamnose 2–5 epimerase: they may be involved in rhamnose biosynthesis and glycosylation. The absence of these plasmid genes in B. hyodysenteriae isolates is predictive of reduced pathogenic potential.

Emergence of severe porcine epidemic diarrhoea in pigs in the USA

PORCINE epidemic diarrhoea (PED) virus is of current concern to the UK pig industry due to recent reports of severe disease outbreaks in the USA. This follows significant PED outbreaks in Korea in the 1990s, which subsequently spread across east and south-east Asia. A more recent rise in PED outbreaks across this region, since 2008, is attributed to new PED virus strains emerging in China, then Vietnam and Thailand, and is causing major disruption to Asian pig production. The recent intercontinental shift of these novel strains to the USA has caused further concern about the highly transportable nature of PED virus and the threat it poses to British pigs. The first case of PED in the USA was confirmed on May 16, and by July 27, just over 10 weeks later, 403 cases had been reported from 16 states through the USDA APHIS VS NVSL National Animal Health Laboratory Network. This letter aims to raise awareness among British veterinary practitioners attending pigs about PED virus, its recent epidemiological movements and measures that their pig producer clients can take to limit the risk of virus incursion. It is important to note that PED is not a notifiable disease and is not zoonotic. Defra has published a preliminary outbreak assessment on PED (www.defra.gov.uk/animal-diseases/monitoring/poa), reviewing potential routes of incursion of PED virus from China and the USA. PED is transmitted through the faeco-oral route by contact …

Efficacy of seven disinfectant sanitisers on field isolates of Brachyspira pilosicoli

EH26 OQE AMONG the intestinal spirochaete species of pigs, Brachyspira hyodysenteriae and Brachyspira pilosicoli are important agents of disease. B pilosicoli infection is variously termed spirochaetal diarrhoea (Taylor 1992), porcine colonic spirochaetosis (Muniappa and others 1997) or porcine intestinal spirochaetosis (Duhamel 1995). A recent study on pig herds with infectious colitis in the UK showed that B pilosicoli was found in 25-0 per cent as a single pathogen, and in another 27-0 per cent as a copathogen (Thomson and others 1998). Transmission of Bpilosicoli occurs either through contamination of the immediate environment, or by direct contact between pigs. B pilosicoli can remain viable in contaminated water for 66 days (Oxberry and others 1998), thus increasing the potential for transmission. As there is no information on the activity of disinfectants against B pilosicoli, this short communication describes a study of the efficacy of seven disinfectant sanitisers against six field isolates and the type strain, ATCC-51139, ofB pilosicoli, in the absence and presence of organic matter. The field isolates were from cases of porcine colitis, obtained as part of a surveillance programme for porcine colitis conducted by the Scottish Agricultural College (SAC). B pilosicoli grown anaerobically in brain heart infusion broth (Oxoid) supplemented with 5 per cent (w/v) filter-sterilised rabbit serum at 380C for two days was used as a bacterial suspension for assessing the disinfectant sanitisers. The tested products were of four different chemical groups, all manufactured by Antec International, and included three quaternary ammonium compounds, Ambicide (a disinfectant), DSC-1000 (a sanitiser) and HD-3 (a sanitiser); one amphoteric surfactant-caustic soda compound, Heavy Duty (a sanitiser); two tar organic acid compounds, Farm Fluid (a disinfectant) and Long Life (a disinfectant); and one peroxygen compound, Virkon S (a disinfectant). The efficacy tests were carried out according to the recommendations of the National Committee for Clinical Laboratory Standards for (NCCLS) antimicrobial susceptibility on anaerobic bacteria (NCCLS 1989), and adapted for testing the disinfectants. Ten-fold dilutions ( 1:10 up to 1 :100,000) of the disinfectant sanitisers were prepared in sterile deionised water (SDW) (for testing in the absence of organic matter) or in a suspension of sterile pig faeces (SPF) (for testing in the presence of organic matter) diluted 1:20 in phosphatebuffered saline solution. An aliquot of 0-1 ml ofbacterial suspension (approximately 105 colony-forming units/ml) was added to 0-9 ml of each serial dilution and the mixture was left for contact times of 30 or 60 minutes at room temperature (220C). Each suspension was then inoculated in triplicate on to blood agar plates, allowed to dry, and incubated anaerobically at 380C for three to four days. Control inocula, with no disinfectant, of each isolate were included. The efficacy of the disinfectant sanitisers was recorded as the proportion (percentage) of inocula at the breakpoint dilution in which bacterial growth was completely inhibited. Statistical analysis of data was performed using a nonparametric test (Mann-Whitney) on Minitab software for Windows. , .-, , a

Survey of veterinary practitioners on PMWS and PDNS in the UK

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Serotypes and Spa types of Erysipelothrix rhusiopathiae isolates from British pigs (1987 to 2015)

Erysipelothrix spp. cause a range of clinical signs in pigs and at least 28 different Erysipelothrix spp. serotypes have been identified. In this study, 128 isolates of Erysipelothrix spp. from pigs in Great Britain from 1987 to 2015 were characterised by serotyping and multiplex real time PCR assays targeting the surface protective antigen (Spa) and the main genotypes (Erysipelothrix rhusiopathiae, Erysipelothrix tonsillarum and Erysipelothrix spp. strain 2). All 128 British isolates were characterised as E. rhusiopathiae and were classified as serotypes 1a (n=21), 1b (n=17), 2 (n=75), 5 (n=2), 9 (n=2), 10 (n=2), 11 (n=4) and 15 (n=1), while four isolates were untypeable. All isolates were positive for the spa A gene. Serotypes 1a, 1b and 2 constituted 88.3% of the isolates; current serotype 2 based vaccines should protect against these isolates.