Exposure of feral swine (Sus scrofa) in the United States to selected pathogens

Feral swine (Sus scrofa) are widely distributed in the United States. In 2011 and 2012, serum samples and tonsils were recovered from 162 and 37 feral swine, respectively, in the US to evaluate exposure to important swine endemic pathogens. Antibodies against porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) were found in 2.5% and 25.3% of tested sera, respectively. Positive serological reactions against Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae have been detected in 19.7% and 69.7% of animals. More than 15% of animals presented antibodies against these 2 pathogens simultaneously. Most animals were also seropositive for Lawsonia intracellularis. Feral swine can also be involved in transmission of zoonotic agents. Almost 50% of animals possessed antibodies against Salmonella. In addition, 94.4% of animals were carriers of Streptococcus suis in their tonsils. In conclusion, feral swine may be considered as a potential reservoir for different endemic diseases in domestic pigs, as well as for important zoonotic agents.     

Ovine contagious epididymitis: A review

Ovine contagious epididymitis is predominantly associated with Brucella ovis, Actinobacillus seminis and a variety of organisms including Histophilus ovis. Transmission occurs venereally or by homosexual activity and, in the case of Actino bacillus seminis, ewe to lamb transmission is probably important. A chronic infection, mainly in the cauda epididymis may result in formation of spermatic granulomata and a reduction in ram fertility. Eradication of ovine brucellosis can be achieved by serological testing using a complement-fixation test in conjunction with palpation of lesions and removal of reactors. Vaccination to control ovine brucellosis is advocated in some countries.The nomenclature of the group of Gram-negative pleomorphic organisms to which Actinobacillus seminis and Histophilus ovis belong is urgently in need of review. This paper reviews the organisms capable of producing ovine contagious epididymitis, the pathogenesis of the condition as well as methods of diagnosis and control.     

The genetic organization of the capsular polysaccharide biosynthesis region of Actinobacillus pleuropneumoniae serotype 14

The genetic organization of the gene involved in the capsular polysaccharide (CPS) biosynthesis of Actinobacillus pleuropneumoniae serotype 14 has been determined. The DNA region for the CPS biosynthesis of serotype 14 (cps14) comprised 9 open reading frames, designated as cps14AB₁B₂B₃CDEFG genes, encoding Cps14A to Cps14G protein, respectively. Cps14A was similar to CpsA of A. pleuropneumoniae serotypes 1, 4 and 12; the Cps14B₁ and Cps14B₂ were similar to CpsB of A. pleuropneumoniae serotypes 1, 4 and 12, suggesting that CPS structure of A. pleuropneumoniae serotype 14 would belong to Group I including A. pleuropneumoniae serotypes 1, 4, 12 and 15. Surprisingly, the overall nucleotide sequence, deduced amino acid sequence, and the genetic organization of the cps14 were nearly identical to those of Actinobacillus suis. This study will provide the molecular basic knowledge for development of diagnostics and vaccine of A. pleuropneumoniae serotype 14.     

Serological characterization of Actinobacillus pleuropneumoniae strains and proposal of a new serotype: serotype 12

Until now 11 serotypes of Actinobacillus pleuropneumoniae have been described (Nicolet 1971, Gunnarsson 1980, Nielsen 1982, Rosendal & Boyd 1982, Nielsen & O’Connor 1984, Nielsen 1985, Kamp 1986). Recently a hitherto unrecognized serotype was isolated from 9 Danish outbreaks of pleuropneumonia in pigs. The origin of the strains is given in Table 1. From 3 herds the unrecognized serotype was found in 2 to 3 pigs submitted for necropsy at different times. The present study describes the serological properties of the 13 isolated strains.     

Identification of Aerococcus Viridans by Means of Co-Agglutination

Gaffkemia, which has recently been reviewed by Stewart & Rabin (1970) and by Stewart (1975), is a fatal bacterial disease of the American and European lobster (Homarus americanus and Homarus vulgaris) (Snieszko & Taylor 1947). The causal agent, first classified as Gaffkya homari (Hitchner & Snieszko 1947), is now classified as Aerococcus viridans (Williams et aL 1953, Buchanan & Gibbons 1974).     

Regional Ileitis in Pigs Isolation of Campylobacter from Affected Ileal Mucosa

In the last few years special interest has been focused on enteric diseases localized to the lower alimentary tract, especially the ileum of weaned pigs. An increasing frequency of disorders of unknown aetiology described as regional ileitis (Emsbo 1951), necrotic enteritis (Jubb & Kennedy 1970), and intestinal adenomatosis (Rowland et al. 1973) has been reported. The changes include thickening of the ileal mucosa with hypertrophy of the muscular wall. The normal structure of villi is replaced by a proliferation of crypt cells. Necrosis of the mucosa and granulation-tissue proliferation in the submucosa occur in later stages. Regional ileitis in man (Crohn et al. 1932) which is described as a chronic enteric disease with granulomatous inflammatory changes localized to segments of the ileum is also attracting increasing attention in medical research (Liljefors 1972). The lesions are also found in the colon, and the presence of a transmissible agent involved in the aetiology of Crohn''s disease has been discussed on the basis of animal experiments (Cave et al. 1973). The disease in pigs is accompanied by haematological changes, including decreased concentration of total serum protein, albumin, alkaline phosphatase, and zinc (Martinsson et al. 1974, 1976).     

Influence of amperozide on disease occurrence in a pig fattening unit

The social and physical environments of animals and man have long been implicated in the etiology of infectious diseases. However, controlled experiments on adverse social and environmental stimuli and animal health are meagre (Kelley 1980). Recently the term psychoimmunology was coined to reflect the growing interest in the relationship between stress, reduced immune function and illness. For more than a decade it has been known that prolonged secretion of stress hormones, particularly corticosteroids, contributes to regression of the lymphoid tissues (Selye 1974, Freeman 1975). Now it has been shown more specifically, that the level of secretory immunoglobulin A is reduced in periods of high stress and that the activity of lymphocytes and natural killer cells are significantly reduced after intense stress periods (Wood 1985). Although the relationship between stress and immunity thus seems to be clear, studies linking those to disease are still a rarity.     

Identification of Actinobacillus Pleuropneumoniae Serotype 2 by Monoclonal or Polyclonal Antibodies in Latex Agglutination Tests

Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is a major problem in modern swine industry worldwide. At present 12 serotypes have been recognized (Nielsen 1990). Serotyping has been based upon capsule associated, heat-stabile antigens of polysaccharide (PS) and lipopolysaccharide (LPS) nature. A variety of tests have been used for serotyping including slide agglutination (Mittal et al. 1982), immunodiffusion (Gunnarsson et al. 1978, Nielsen & O’Connor 1984), indirect haemagglutination (Mittal et al. 1983a) and coagglutination (Mittal et al. 1983b). Recent studies report on serotyping of A. pleuropneumoniae strains using monoclonal antibodies in enzyme-linked immunosorbent assays (Lida et al. 1990, Nakai et al. 1990).     

A Field Outbreak Caused by Bovine Respiratory Syncytial Virus

Bovine respiratory syncytial virus (BRSV) caused a large epizootic of acute respiratory disease in Japan in 1968—69 (Inaba et al. 1970, Inaba et al. 1972). A much smaller outbreak occurred in Switzerland (Paccaud & Jacquier 1970). In Belgium the virus has been isolated from an outbreak of respiratory disease (Wellemans et al. 1970). BRSV has later been proved an important causal agent of respiratory disorders in the same country (Wellemans & Leiinen 1975). In England and USA the virus has caused and been isolated from outbreaks of acute respiratory disease in calves (Jacobs & Edington 1971, Rosenquist 1974, Smith et al. 1974). In Denmark BRSV has sporadically been isolated from pneumonic calf lungs (Bitsch et al. 1976).     

Toxicity of halogenated oxyquinolines to dogs. The effect of feeding fouled herring

Acute clinical toxicity of halogenated oxyquinolines in dogs has been reported (Schantz & Wikström 1965, Hangartner 1965, Müller 1967). The clinical picture was comprehensively studied (Lannek 1972 b). The dose range in the clinical material was found to vary from about 7 to 250 mg per kg body weight (Lannek 1972 a).     

Isolation of Yersinia Enterocolitica from a Dog with Chronic Enteritis: A Case Report

During recent years, Yersinia enterocolitica has been isolated from humans and various animal species in connection with intestinal disorders, such as acute ileitis and appendicitis. Cases of septicaemia, polyarthritis and erythema nodosum have also been described (Mollaret & Destombes 1964, Nilehn 1969, Winblad 1969, Lassen 1972, Langford 1972). Y. enterocolitica has been isolated most frequently from chinchillas and hares, but sporadic isolations from deer, cow, horse, rabbit, goat and dog have been reported (Langford, Krogstad et al. 1972). In Norway, an outbreak of the disease in a goat herd is the only described case of yersiniosis among animal species (Krogstad et al.). A case of chronic enteritis in a dog from which Y. enterocolitica was isolated is presented in the following.     

Adherence of Actinobacillus pleuropneumoniae serotype 1 to swine buccal epithelial cells involves fibronectin

The swine pathogen Actinobacillus pleuropneumoniae serotype 1 was investigated for its ability to adhere to swine, rat, and human buccal epithelial cells (BEC). The highest number of bacteria adhered was to swine BEC. This binding ability was affected by heating, extreme pH, treatment with sodium dodecyl sulfate, ethylenediamine tetraacetate, or periodate, and proteolysis, suggesting that cell-surface glycoproteins participate in adherence and that adherence is based mostly on ionic interactions. Mannose and swine fibronectin may play a direct role in this interaction. Convalescent-phase serum from naturally infected pigs inhibited the adhesion. There was a correlation between bacterial pathogenicity as well as host specificity and the capacity for adherence to swine BEC. Adhesion to swine BEC provides a convenient method to study in vitro the adherence of A. pleuropneumoniae and other pathogens of the pig respiratory tract.     

Genomic Description of Antibiotic Resistance in Escherichia coli and Enterococci Isolates from Healthy Lusitano Horses

Antibiotic resistance is a global problem, and it is known that commensal bacteria can act as reservoir of antibiotic resistance genes of clinical importance. The aim of the present study was to determine the antibiotic resistance phenotype and mechanisms implicated in resistance of Escherichia coli and Enterococcus spp. isolates collected from fecal samples of 90 Lusitano horses from Portugal. Sixteen of the 71 E. coli isolates (22.5%) recovered showed resistance to at least one of the antibiotics tested. The number of E. coli isolates resistant to streptomycin, tetracycline, chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole, and gentamicin was 9, 7, 6, 3, 2, and 1, respectively. The bla_TEM-1 and bla_OXA-1 genes were detected in ampicillin-resistant isolates and the sul2 and dfrA1 genes in trimethoprim-sulfamethoxazole-resistant, while the aac(3)-I, floR and tet(A) were found in the gentamicin, chloramphenicol and tetracycline-resistant isolates, respectively. Twenty-two of the 71 (31%) recovered enterococci showed antibiotic resistance for at least one of the tested antibiotics, and resistant isolates were identified as Enterococcus faecium (n = 14), E. faecalis (n = 3), E. hirae (n = 2), and Enterococcus spp. (n = 3). The erm(B) and erm(C) genes were identified in erythromycin-resistant enterococci and the tet(M) and/or tet(L) genes in tetracycline-resistant isolates. The slight prevalence of antibiotic resistance among commensal bacteria of healthy Lusitano horses can improve the treatment of upcoming infections in these horses because these microorganisms can be considered as antimicrobial indicator bacteria.     

Characterization of Mannheimia haemolytica isolated from feedlot cattle that were healthy or treated for bovine respiratory disease

Mannheimia haemolytica is the principal bacterial pathogen associated with bovine respiratory disease (BRD). As an opportunistic pathogen, M. haemolytica is also frequently isolated from the respiratory tract of healthy cattle. This study examined the characteristics of M. haemolytica collected using deep nasal swabs from healthy cattle (n = 49) and cattle diagnosed with BRD (n = 41). Isolates were analyzed by pulsed-field gel electrophoresis (PFGE), serotyped, and tested for antimicrobial susceptibility. Polymerase chain reaction (PCR) was used to screen isolates for virulence [leukotoxin C (lktC), putative adhesin (ahs), outer-membrane lipoprotein (gs60), O-sialoglycoprotease (gcp), transferring-binding protein B (tbpB) and UDP-N-acetyl-D-glucosamine-2-epimerase (nmaA)] and antimicrobial resistance [tet(H), bla_ROB-1, erm(X), erm(42), msr(E)-mph(E) and aphA-1] genes. Isolates were genetically diverse but in three instances, M. haemolytica with the same pulsotype, resistance phenotype, and genotype were collected from cattle with BRD. This occurred once between cattle located in two different feedlots, once between cattle in the same feedlot, but in different pens, and once among cattle from the same feedlot in the same pen. Isolates from healthy cattle were primarily serotype 2 (75.5%) while those from individuals with BRD were serotype 1 (70.7%) or 6 (19.5%). Resistance to at least one antibiotic occurred more frequently (P < 0.001) in M. haemolytica collected from cattle with BRD (37%) compared with those that were healthy (2%). Overall, tetracycline resistance (18%) was the most prevalent resistant phenotype. All tetracycline-resistant M. haemolytica encoded tet(H). Ampicillin resistance (6%) and neomycin resistance (15%) were detected and corresponded to the presence of the bla_ROB-1 and aphA-1 genes, respectively. Tilmicosin resistance (6%) was also detected, but the resistance genes responsible were not identified. The virulence genes lktC, ahs, gs60, and gcp were present in all isolates examined, while tbpB and nmaA were only detected in serotype 1 and serotype 6 isolates indicating they may be potential targets for serotype-specific identification or vaccine development. These results provide the first reported evidence of transmission and spread of antimicrobial-resistant M. haemolytica that have contributed to bovine respiratory disease in western Canadian feedlots.     

Prevalence of Antibodies to Neospora caninum and Toxoplasma gondii in Swedish Dogs

Neospora caninum is a newly described coccidian parasite which has been found in various species such as the dog, cattle, horse, sheep and goat. Morphologically it resembles Toxoplasma gondii with which it is related (Holmdahl et al. 1994), and with which it has earlier been confused. The life cycle of N caninum is only partially known. Tachyzoites and tissue cysts are the only known stages of the parasite, and transplacental transmission is the only known route of infection. Subclini-cally infected dams can transmit the parasite to their fetuses and successive offspring from the same mother might be born infected (Dubey et al. 1990b). Clinical neosporosis is mostly seen in pups or young dogs, and the majority or all pups in a litter are often affected. The disease is characterized by ascending paralysis of the legs, with the hind legs more severely affected than the front legs, paralysis of the jaw, difficulty in swallowing and muscle flaccidity and atrophy (Dubey 1992, Dubey & Lindsay 1993). Fatal infections with N caninum in dogs have been reported from many countries, e.g. Norway (Bjerkäs & Presthus 1988), USA (Dubey et al. 1988), Sweden (Uggla et al. 1989a,b) and the United Kingdom (Dubey et al. 1990a). Serological surveys for antibodies to N. caninum in dogs from Kansas, USA and England have shown a prevalence of 2 and 13%, respectively (Lindsay et al. 1990, Trees et al. 1993).     

Characterization of colonization-deficient mutants of Actinobacillus suis

Actinobacillus suis is an important opportunistic pathogen of swine that can cause disease in pigs of all ages, especially in high-health status herds. Although A. suis shares many virulence factors in common with Actinobacillus pleuropneumoniae and can cause a haemorrhagic pleuropneumonia similar to that caused by A. pleuropneumoniae, A. suis most often causes septicaemia and diseases such as arthritis and meningitis that are sequelae to septicaemia. In a recent signature-tagged transposon mutagenesis study, 30 colonization-essential genes of A. suis were identified. In the current study, the attachment and invasion patterns of strains harboring Tn10 insertions in ompA, pfhaB1, lcbB, and cpxR were evaluated using porcine palatine tonsil organ cultures, the swine kidney epithelial cell line, SK6, and a porcine brain microvascular endothelial cell line, PBMEC/C1-2. All of these mutants attached in lower numbers than wild type to the tonsillar explants and to the SK6 cells. The ompA mutant attached in significantly lower numbers than wild type to the porcine tonsil cells (P = 0.02) and to PBMEC (P = 0.0008) at 60 min time point. As well, the ompA mutant showed significantly greater sensitivity than wild type to chemical stressors and to swine serum. Using fluorescent microscopy, a GST-OmpA fusion protein could be demonstrated to interact with the crypt epithelial cells of porcine palatine tonsil.     

DNA microarray-based identification and typing of Actinobacillus pleuropneumoniae

A DNA microarray system was prepared and shown to facilitate identification and typing of Actinobacillus pleuropneumoniae. The DNA microarray, composed of 18 DNA polymerase chain reaction (PCR) amplicons printed on glass slides and arranged in 3 subarrays, was developed. These target DNA included 1 or multiple fragments of the outer membrane lipoprotein, apx toxin, capsular polysaccharide, and disulfide bound formation protein E (dsbE)-like genes of A. pleuropneumoniae. These arrayed target DNA retained their expceted hybridization properties. The hybridization signal intensities ranged from the least-intense to the most-intense, 4626 to 9789 arbitrary fluorescence units, respectively. Cy3-probes of A. pleuropneumoniae strains labeled with multiplex PCR were hybridized to the DNA microarray. A total of 51 different A. pleuropneumoniae strains representing serotype 1 to 12 reference strains and clinical isolates were detected and typed by the DNA microarray. Twelve reference serotypes produced 11 distinct target DNA hybridization patterns, and hybridization patterns of serotypes 1 (n = 7), 3 (n = 5), and 7 (n = 6) field isolates were identical to hybridization patterns of reference serotypes 1, 3, and 7, respectively. Non-serotyped isolates 4, 6, and 11 (out of 21) from diseased pigs had identical hybridization patterns to reference serotypes 3, 7, and 1, respectively. The results show that the DNA microarray system described in the present study is a valuable tool for identifying and typing reference strains and isolates of A. pleuropneumoniae, and enables relatively rapid identification of non-serotyped isolates.     

Immunological study of an attenuated Salmonella Typhimurium expressing ApxIA,ApxIIA, ApxIIIA and OmpA of Actinobacillus pleuropneumoniae in a mouse model

Salmonella Typhimurium strain expressing the Actinobacillus pleuropneumoniae antigens, ApxIA, ApxIIA, ApxIIIA and OmpA, was previously constructed as a vaccine candidate for porcine pleuropneumonia. This strain was a live attenuated (∆lon∆cpxR∆asd)Salmonella as a delivery host and contained a vector containing asd. An immunological study of lymphocyte proliferation, T-lymphocyte subsets and cytokines in the splenocytes of a mouse model was carried out after stimulation with the candidate Salmonella Typhimurium by intranasal inoculation. The splenic lymphocyte proliferation and the levels of IL-4, IL-6 and IL-12 of the inoculated mice were significantly increased, and the T- and B-cell populations were also elevated. Collectively, the candidate may efficiently induce the Th1- and Th2-type immune responses.     

High diversity of coagulase negative staphylococci species in wild boars,with low antimicrobial resistance rates but detection of relevant resistance genes

This work was focused to determine the prevalence and the species diversity of coagulase-negative staphylococci (CoNS) in wild boars, and to study their antimicrobial resistance phenotype and genotype. Nasal samples of 371 wild boars from six Spanish regions were collected for CoNS recovery. The identification was performed by MALDI-TOF mass-spectrometry. Antimicrobial susceptibility for eight antimicrobial agents was studied by disc-diffusion method and the presence of 31 antimicrobial resistance genes by PCR.CoNS were detected in nasal samples of 136/371 animals tested (36.6%), and 161 isolates were obtained (1–3/animal); a high diversity of species was found (n = 17), with predominance of S. sciuri (n = 64), S. xylosus (n = 21) and S. chromogenes (n = 17). Among CoNS isolates, 22.4% showed resistance to at least one antimicrobial tested. Tetracycline-resistance phenotype was the most frequently detected (10.5%), generally mediated by tet(K) gene [associated or not with tet(L)]. Other relevant resistance genes were identified including unusual ones [mecA, erm(B), erm(F), mphC, erm(43), msr(A)/msr(B), lnu(A), dfrG, fexA, and cat_pC221].This is the first study in which CoNS isolates from wild boars are analysed. The knowledge of antimicrobial phenotype and genotype of CoNS in natural ecosystems is highly important since these staphylococcal species can act as vectors of relevant antimicrobial resistance mechanisms.     

Small Intestinal Bacterial Overgrowth in Seven Dogs with Gastrointestinal Signs

In small intestinal bacterial overgrowth (SIBO) syndrome the small intestine is colonized by bacteria in excess of 10⁵ colony-forming units (CFU)/ml or g (Batt et al 1983, Williams et al 1987, Strombeck & Guilford 1990). In dogs, SIBO has only recently been recognized as a cause of gastrointestinal signs like diarrhea (Strombeck et al 1981, Batt et al 1983, Batt & McLean 1987, Batt et al 1988). No demonstrable underlying anatomic or functional predisposition is identified in most cases of canine SIBO. However, most of the reported cases have been on German shepherds and dogs suffering from pancreatic insufficiency (Williams etal 1987; Simpson etal 1990).