Toxigenic and non-toxigenic Pasteurella multocida genotypes, based on capsular, LPS, and virulence profile typing, associated with pneumonic pasteurellosis in Iran.

Pasteurella multocida is an important cause of pneumonic pasteurellosis in small ruminants. Its prevalence was investigated in 349 pneumonic lungs from sheep (n = 197) and goats (n = 152), and genotypes of isolates were determined by capsular and lipopolysaccharide (LPS) typing as well as by virulotyping based on the detection of 12 virulence-associated genes. P. multocida was isolated from 29.4 % of sheep lungs and 13.8 % of goat lungs. A (78.5 %) and D (21.5 %) capsular types, as well as L3 (41.8 %) and L6 (57.0 %) LPS genotypes, were detected, with the A:L6 genotype being the most prevalent in both sheep (59.6 %) and goat (52.4 %) isolates. A total of 19 virulence profiles (VP) were detected, seven non-toxigenic and 12 toxigenic, which correlated with the capsular-LPS genotype. All isolates of each VP belonged to the same LPS and capsular genotype, except for one isolate of VP1. The diversity in VP was higher among toxigenic (0.29) than non-toxigenic (0.18) isolates. Moreover, the toxigenic VPs showed more diversity in their capsular-LPS genotypes, with the two main toxigenic VPs belonging to genotypes D:L3 (VP2) and A:L3 (VP3). Therefore, the abundance of toxigenic isolates among sheep and goat isolates does not seem to correspond to the expansion of a more virulent lineage associated with pneumonic pasteurellosis in small ruminants. The most prevalent genotypes among sheep isolates were the non-toxigenic VP1:A:L6 (41.4 %) and the toxigenic VP3:A:L3 (17.2 %) genotypes, whereas the most prevalent among goat isolates were the toxigenic VP2:D:L3 (33.3 %) and the non-toxigenic VP1:A:L6 (14.3 %) and VP4:A:L6 (14.3 %) genotypes. These prevalent toxigenic and non-toxigenic genotypes seem to be epidemiologically relevant in pneumonic pasteurellosis of small ruminants.

Evolution of the nasopharyngeal bacterial microbiota of beef calves from spring processing to 40 days after feedlot arrival.

The composition of the nasopharyngeal bacterial microbiota has been shown to play a role in cattle respiratory health. However, previous studies are narrow in scope regarding longitudinal observations, limiting our understanding of how respiratory bacteria evolve over time. The objective was therefore to characterize this microbiota and its evolution over time in beef calves. A total of 120 crossbred beef-breed steer calves were enrolled in a study in southern Alberta at the time of first vaccination (spring processing), comprising three groups (40 calves/group) that originated from different ranches and were placed in different feedlots. Deep nasopharyngeal swab samples were collected from the calves at the time of spring processing, arrival at the feedlot, and a targeted 40 days after feedlot arrival. The swabs were processed for DNA extraction and the V4 region of the 16S rRNA gene was sequenced to evaluate the microbiota. The composition of the microbiota differed among groups of calves, with each group showing different relative abundances of 963 observed sequence variants. Mycoplasma was the most abundant genus and M. dispar the most abundant species across all groups. There was a distinct shift in the composition of the microbiota over time for all calf groups; however, changes in sequence variants differed by group. Variations in both microbiota composition and temporal changes of sequence variants according to calf group indicates that the respiratory microbiota of beef cattle may lack a common pattern of evolution from ranch to feedlot, and that future studies should account for potential group effects.

Bacterial, PCR and clinico-pathological diagnosis of naturally occurring pneumonic pasturellosis (mannheimiosis) during subtropical climate in sheep.

Mannheimia haemolytica is causative agent of pneumonic pasteurellosis (mannheimiosis) that causes huge economic losses to livestock farmers. We investigated the microbial and clinico-pathological patterns associated with ovine pneumonic pasturellosis during an outbreak. Prior to death, infected sheep revealed clinical signs including dyspnoea, salivation, pyrexia and mucopurulent nasal discharge. Mortality was significantly (p < 0.05) high in young sheep as compared to adults. Necropsy findings revealed presence of froth in trachea, congestion and consolidation of lungs, pulmonary edema, severe pleural adhesions, pericarditis, hemorrhages on mucosa of jejunum and kidneys. Histopathological examination revealed circumscribed and centrally calcified necrotic areas punctuated with chronic inflammatory cells and interstitial pneumonia. Moreover, bronchial epithelial hyperplasia, edema, congestion, mononuclear cell infiltration, thick interlobular septae and peri-vascular cuffing were the striking changes in lungs. Furthermore, lungs showed severe fibrin depositions along with abundant amount of fibrin meshwork on pleura infiltrated with chronic inflammatory cells. Histologically, liver, kidneys and lymph nodes showed degenerative changes. Mannheimia haemolytica and Pasteurella multocida were differentially identified on the basis of culture characteristics and biochemical tests. M. haemolytica was further confirmed by using polymerase chain reaction. From the findings of current study, it is concluded that M. haemolytica is a major respiratory threat in small ruminants that causes severe pneumonic changes in infected animals.

Seroprevalence of respiratory viral pathogens of indigenous calves in Western Kenya.

Most studies of infectious diseases in East African cattle have concentrated on gastro-intestinal parasites and vector-borne diseases. As a result, relatively little is known about viral diseases, except for those that are clinically symptomatic or which affect international trade such as foot and mouth disease, bluetongue and epizootic haemorrhagic disease. Here, we investigate the seroprevalence, distribution and relationship between the viruses involved in respiratory disease, infectious bovine rhinotracheitis virus (IBR), bovine parainfluenza virus Type 3 (PIV3) and bovine viral diarrhoea virus (BVDV) in East African Shorthorn Zebu calves. These viruses contribute to the bovine respiratory disease complex (BRD) which is responsible for major economic losses in cattle from intensive farming systems as a result of pneumonia. We found that calves experience similar risks of infection for IBR, PIV3, and BVDV with a seroprevalence of 20.9%, 20.1% and 19.8% respectively. We confirm that positive associations exist between IBR, PIV3 and BVDV; being seropositive for any one of these three viruses means that an individual is more likely to be seropositive for the other two viruses than expected by chance.

The incidence and risk factors for shipping fever in horses transported by air to Hong Kong: Results from a 2-year prospective study.

A 2 year prospective study was performed between February 2011 and January 2013 to determine the incidence and risk factors for shipping fever (SF) in horses transported by air to Hong Kong (HK). Using a questionnaire, data were collected from professional flying grooms regarding the journey to HK and horses in the shipment. Horses were monitored in quarantine for 2 weeks after arrival in HK, and clinical signs of SF recorded. Poisson and logistic regression models were used to identify risk factors for SF at the horse and shipment levels. The study analysed data from 869 horses on 81 flights arriving from Australia (n = 24), New Zealand (NZ; n = 18), the United Kingdom (UK; n = 33) and the United States of America (USA; n = 6). The incidence risk of SF was 10.8 per 100 horses and the proportion of shipments with at least one horse that developed SF was 49/81 (60%). The study identified that the rate per shipment of SF in shipments of horses originating from NZ, the USA and the UK was 2.40 (95% confidence interval [CI] 1.22-4.71), 2.43 (95% CI 0.66-8.89) and 3.08 (95% CI 1.60-5.93) times the rate of SF compared to Australia. Shipments arriving in HK during March and May were 5.61 (95% CI 1.55-20.31) and 4.51 (95% CI 1.43-14.26) times more likely to contain horses that developed SF compared to shipments arriving in January. The identification of these risk factors and the recognition of at-risk shipments will help focus attention on preventative strategies.

Field epidemiology to manage BRD risk in beef cattle production systems.

Field disease investigations can help to identify patterns of disease that lead to causal hypotheses and, hopefully, effective disease risk management strategies. The most common way of doing this would be to characterize the outbreak by subject, time, and space. One of the perplexing animal health problems on some beef cattle ranches is the occurrence of pneumonia in calves prior to weaning in conditions of little stress and relative isolation. Field investigation of outbreaks of pneumonia in ranch calves prior to weaning has revealed patterns of sporadic illness in calves less than 30 days of age, and rapidly occurring outbreaks in calves 90-150 days of age. We speculate that the causes of these two patterns may be failure of passive transfer resulting in more sporadic cases in very young calves, or a large proportion of the population losing maternal antibody protection (i.e. losing herd immunity) resulting in rapid and widespread onset of pneumonia in older calves.

PCR assay detects Mannheimia haemolytica in culture-negative pneumonic lung tissues of bighorn sheep (Ovis canadensis) from outbreaks in the western USA, 2009-2010.

Mannheimia haemolytica consistently causes severe bronchopneumonia and rapid death of bighorn sheep (Ovis canadensis) under experimental conditions. However, Bibersteinia trehalosi and Pasteurella multocida have been isolated from pneumonic bighorn lung tissues more frequently than M. haemolytica by culture-based methods. We hypothesized that assays more sensitive than culture would detect M. haemolytica in pneumonic lung tissues more accurately. Therefore, our first objective was to develop a PCR assay specific for M. haemolytica and use it to determine if this organism was present in the pneumonic lungs of bighorns during the 2009-2010 outbreaks in Montana, Nevada, and Washington, USA. Mannheimia haemolytica was detected by the species-specific PCR assay in 77% of archived pneumonic lung tissues that were negative by culture. Leukotoxin-negative M. haemolytica does not cause fatal pneumonia in bighorns. Therefore, our second objective was to determine if the leukotoxin gene was also present in the lung tissues as a means of determining the leukotoxicity of M. haemolytica that were present in the lungs. The leukotoxin-specific PCR assay detected leukotoxin gene in 91% of lung tissues that were negative for M. haemolytica by culture. Mycoplasma ovipneumoniae, an organism associated with bighorn pneumonia, was detected in 65% of pneumonic bighorn lung tissues by PCR or culture. A PCR assessment of distribution of these pathogens in the nasopharynx of healthy bighorns from populations that did not experience an all-age die-off in the past 20 yr revealed that M. ovipneumoniae was present in 31% of the animals whereas leukotoxin-positive M. haemolytica was present in only 4%. Taken together, these results indicate that culture-based methods are not reliable for detection of M. haemolytica and that leukotoxin-positive M. haemolytica was a predominant etiologic agent of the pneumonia outbreaks of 2009-2010.

Relationship between serotype and the antimicrobial susceptibility of Mannheimia haemolytica isolates collected between 1991 and 2010.

The antimicrobial susceptibilities and serotype distribution of 310 Mannheimia haemolytica isolates obtained from cattle with bovine respiratory disease during 2002-2010 were investigated. Of the 310 isolates, 198 (63.9%) were resistant to at least one of the 16 tested antimicrobial agents. The resistance rates for ampicillin, amoxicillin, dihydrostreptomycin, kanamycin, oxytetracycline, doxycycline, chloramphenicol, thiamphenicol, nalidixic acid, enrofloxacin, and danofloxacin were 20.3%, 14.5%, 43.5%, 23.5%, 24.8%, 21.9%, 23.2%, 23.9%, 47.1%, 18.7%, and 18.7%, respectively. Almost 90% of the isolates belonged to three serotypes (serotypes A1, A2, and A6), and the relative prevalence of serotype A6 increased significantly over the last decade. Compared with bacteria belonging to other serotypes, bacteria belonging to serotype A6 exhibited a significantly higher antimicrobial resistance rates (χ2 test, p<0.05). The results of this investigation provide useful information for understanding the serotype prevalence and antimicrobial resistance patterns of one of the major bacteriological agents implicated in pneumonic pasteurellosis.

Bighorn sheep pneumonia: sorting out the cause of a polymicrobial disease.

Pneumonia of bighorn sheep (Ovis canadensis) is a dramatic disease of high morbidity and mortality first described more than 80 years ago. The etiology of the disease has been debated since its initial discovery, and at various times lungworms, Mannheimia haemolytica and other Pasteurellaceae, and Mycoplasma ovipneumoniae have been proposed as primary causal agents. A multi-factorial "respiratory disease complex" has also been proposed as confirmation of causation has eluded investigators. In this paper we review the evidence for each of the candidate primary agents with regard to causal criteria including strength of association, temporality, plausibility, experimental evidence, and analogy. While we find some degree of biological plausibility for all agents and strong experimental evidence for M. haemolytica, we demonstrate that of the alternatives considered, M. ovipneumoniae is the best supported by all criteria and is therefore the most parsimonious explanation for the disease. The strong but somewhat controversial experimental evidence implicating disease transmission from domestic sheep is consistent with this finding. Based on epidemiologic and microbiologic data, we propose that healthy bighorn sheep populations are naïve to M. ovipneumoniae, and that its introduction to susceptible bighorn sheep populations results in epizootic polymicrobial bacterial pneumonia often followed by chronic infection in recovered adults. If this hypothesized model is correct, efforts to control this disease by development or application of vectored vaccines to Pasteurellaceae are unlikely to provide significant benefits, whereas efforts to ensure segregation of healthy bighorn sheep populations from M. ovipneumoniae-infected reservoir hosts are crucial to prevention of new disease epizootics. It may also be possible to develop M. ovipneumoniae vaccines or other management strategies that could reduce the impact of this devastating disease in bighorn sheep.

Atypical non-progressive pneumonia in goats.

An outbreak of severe respiratory disease in a goat herd was associated with Mycoplasma ovipneumoniae, Mycoplasma arginini, Mannheimia haemolytica and Pasteurella multocida with mortality rates exceeding 20% in kids. Post mortem features in affected kids included severe pleuropneumonia, lung consolidation, large quantities of pleural fluid and pericarditis. This is the first report of atypical proliferative pneumonia in goats in Portugal.

Epidemic pasteurellosis in a bighorn sheep population coinciding with the appearance of a domestic sheep.

A pneumonia epidemic reduced bighorn sheep (Ovis canadensis) survival and recruitment during 1997-2000 in a population comprised of three interconnected wintering herds (Kenosha Mountains, Sugarloaf Mountain, Twin Eagles) that inhabited the Kenosha and Tarryall Mountain ranges in central Colorado, USA. The onset of this epidemic coincided temporally and spatially with the appearance of a single domestic sheep (Ovis aires) on the Sugarloaf Mountain herd's winter range in December 1997. Although only bighorns in the Sugarloaf Mountain herd were affected in 1997-98, cases also occurred during 1998-99 in the other two wintering herds, likely after the epidemic spread via established seasonal movements of male bighorns. In all, we located 86 bighorn carcasses during 1997-2000. Three species of Pasteurella were isolated in various combinations from affected lung tissues from 20 bighorn carcasses where tissues were available and suitable for diagnostic evaluation; with one exception, beta-hemolytic mannheimia (Pasteurella) haemolytica (primarily reported as biogroup 1(G) or 1(alphaG)) was isolated from lung tissues of cases evaluated during winter 1997-98. The epidemic dramatically lowered adult bighorn monthly survival in all three herds; a model that included an acute epidemic effect, differing between sexes and with vaccination status, that diminished linearly over the next 12 mo best represented field data. In addition to the direct mortality associated with epidemics in these three herds, lamb recruitment in years following the pneumonia epidemic also was depressed as compared to years prior to the epidemic. Based on observations presented here, pasteurellosis epidemics in free-ranging bighorn sheep can arise through incursion of domestic sheep onto native ranges, and thus minimizing contact between domestic and bighorn sheep appears to be a logical principle for bighorn sheep conservation.

Pasteurella multocida and bovine respiratory disease.

Pasteurella multocida is a pathogenic Gram-negative bacterium that has been classified into three subspecies, five capsular serogroups and 16 serotypes. P. multocida serogroup A isolates are bovine nasopharyngeal commensals, bovine pathogens and common isolates from bovine respiratory disease (BRD), both enzootic calf pneumonia of young dairy calves and shipping fever of weaned, stressed beef cattle. P. multocida A:3 is the most common serotype isolated from BRD, and these isolates have limited heterogeneity based on outer membrane protein (OMP) profiles and ribotyping. Development of P. multocida-induced pneumonia is associated with environmental and stress factors such as shipping, co-mingling, and overcrowding as well as concurrent or predisposing viral or bacterial infections. Lung lesions consist of an acute to subacute bronchopneumonia that may or may not have an associated pleuritis. Numerous virulence or potential virulence factors have been described for bovine respiratory isolates including adherence and colonization factors, iron-regulated and acquisition proteins, extracellular enzymes such as neuraminidase, lipopolysaccharide, polysaccharide capsule and a variety of OMPs. Immunity of cattle against respiratory pasteurellosis is poorly understood; however, high serum antibodies to OMPs appear to be important for enhancing resistance to the bacterium. Currently available P. multocida vaccines for use in cattle are predominately traditional bacterins and a live streptomycin-dependent mutant. The field efficacy of these vaccines is not well documented in the literature.

Contagious caprine pleuropneumonia and Mannheimia haemolytica-associated acute respiratory disease of goats and sheep in Afar Region, Ethiopia.

In April 2002, an investigation into an outbreak of acute respiratory disease in goats and sheep in Milae (Afar), Ethiopia was conducted. The investigation involved 4 flocks (722 sheep and 750 goats in total) and comprised the disease history, clinical and post-mortem examination, and microbiological analysis of nasal swabs, lung lesions, and pleural fluid samples. Clinically diseased animals exhibited severe respiratory distress, and necropsy of two of the goats demonstrated fibrinous pneumonia, lung sequestra, and excessive accumulation of straw coloured fluid in the thoracic cavity. Mannheimia haemolytica biotype T was isolated from nine (six goats and three sheep) out of 23 nasal swabs (39.1%). In the two necropsied animals Mycoplasma capricolum subsp. capripneumoniae (Mccp) was isolated from the lungs, and Mannheimia haemolytica biotype T was isolated from lung lesions and thoracic fluid. An unidentified Mycoplasma species was isolated from the thoracic fluid of one of the goats. Pseudomonas aeruginosa was isolated from a lung sequestrum of one of the necropsied goats. In vitro antimicrobial susceptibility test results indicated that two (33.3%) of the six M. haemolytica isolates that were tested were resistant to ampicillin and penicillin G, three (50%) to tetracycline, four (66.7%) to oxacillin, five (83.3%) to erythromycin, and six (100%) to clindamycin. Pseudomonas aeruginosa was resistant to all of the different classes of antimicrobials that were tested. Pleuropneumonia caused by Mccp, and secondary complications caused by M. haemolytica and the other unidentified Mycoplasma species, were confirmed as the cause of the outbreak. Morbidity was not associated with the species of animals affected (P > 0.05); however, mortality was significantly higher in goats than sheep (P < 0.05).

Minimum inhibitory concentrations of tulathromycin against respiratory bacterial pathogens isolated from clinical cases in European cattle and swine and variability arising from changes in in vitro methodology.

The in vitro activity of tulathromycin was evaluated against common bovine and porcine respiratory pathogens collected from outbreaks of clinical disease across eight European countries from 1998 to 2001. Minimum inhibitory concentrations (MICs) for one isolate of each bacterial species from each outbreak were determined using a broth microdilution technique. The lowest concentrations inhibiting the growth of 90% of isolates (MIC90) for tulathromycin were 2 microg/ml for Mannheimia (Pasteurella) haemolytica, 1 microg/ml for Pasteurella multocida (bovine), and 2 microg/ml for Pasteurella multocida (porcine) and ranged from 0.5 to 4 microg/ml for Histophilus somni (Haemophilus somnus) and from 4 to 16 microg/ml for Actinobacillus pleuropneumoniae. Isolates were retested in the presence of serum. The activity of tulathromycin against fastidious organisms was affected by culture conditions, and MICs were reduced in the presence of serum.

Efficacy of tulathromycin in the treatment and prevention of natural outbreaks of bovine respiratory disease in European cattle.

The efficacy of tulathromycin in the treatment (phase 1) and prevention (phase 2) of bovine respiratory disease (BRD) was evaluated on commercial farms in France, Germany, Italy, and Spain. In phase 1, commingled cattle with clinical BRD were treated with tulathromycin (n = 128) or florfenicol (n = 125) on day 0. Similar percentages of animals showed sustained clinical improvement at day 14 (tulathromycin 83.3% versus florfenicol 81.0%) and had not relapsed by day 60 (tulathromycin 63.3% versus florfenicol 58.4%). In phase 2, healthy in-contact cattle were treated with tulathromycin (n = 492), tilmicosin (n = 494), or saline (n = 265) on day 0. Significantly more (P = .0001) tulathromycin-treated cattle remained healthy to day 14 (92.4%) than tilmicosin-treated (83.7%) or saline-treated (63.7%) cattle, and this was maintained through day 60 (tulathromycin 85.4% versus tilmicosin 75.1% and saline 56.2%). Tulathromycin was highly effective in the treatment and prevention of BRD.

Evaluation of the therapeutic activity of tulathromycin against swine respiratory disease on farms in Europe.

The clinical efficacy of tulathromycin in the treatment of natural outbreaks of swine respiratory disease (SRD) was evaluated at five European sites. Pigs (1 to 6 months of age) exhibiting clinical signs of SRD were treated intramuscularly with tulathromycin (n = 247) at 2.5 mg/kg on day 0 versus either tiamulin (n = 102) at 15 mg/kg on days 0, 1, and 2 (Germany, the Netherlands, and the United Kingdom) or florfenicol (n = 20) at 15 mg/kg on days 0 and 2 (France). Actinobacillus pleuropneumoniae, Pasteurella multocida, and Mycoplasma hyopneumoniae infections were the most frequently diagnosed pathogens. For both tulathromycin-treated animals and those treated with tiamulin or florfenicol, there were significant (P = .0001) reductions in mean rectal temperature and the severity of abnormal clinical signs on days 2 and 10 compared with day 0. There were no significant differences (P > .05) between treatments in average daily weight gain. Tulathromycin was found to be safe and highly effective in the treatment of natural outbreaks of SRD.

Use of Akaike information criteria for model selection and inference. An application to assess prevention of gastrointestinal parasitism and respiratory mortality of Guinean goats in Kolda, Senegal.

A field experiment was carried out in Kolda (southern Senegal) from July 1986 to July 1988. Its goals were to: (1) describe the patterns of mortality of female Guinean goats by age, season and year; (2) assess preventive measures against respiratory diseases and gastrointestinal parasitism in reducing mortality; and (3) estimate the overall impact of these measures on survival to 1 year of age. Preventive measures for respiratory disease included vaccination against peste des petits ruminants (PPR) and pneumonic pasteurellosis (Pasteurella multocida types A and D). Control of gastrointestinal parasites was by deworming does with morantel (7.5mg kg(-1), three times during the rainy season). The effects of vaccines and deworming were tested in a randomised factorial field experiment with villages being the experimental units. A total of 19 villages, 113 goat herds and 1,458 goats were included in the study. Generalised linear models of survival for five cohorts of goats (defined by five different birth seasons) used a binomial assumption for the response distribution and a complementary log-log link. Explanatory variables included age, season, year, vaccination, deworming and their interactions. A complex a priori model was built on the basis of previous epidemiological knowledge; a purposely selected set of simpler models was compared to this full model by the Akaike information criterion (AIC) and derived statistics. Inference on 1-year survival and treatment effects accounted for model-selection uncertainty. It was carried out with a bootstrap procedure and used information from the whole set of selected models. Large variations in mortality by year and season were observed but no regular seasonal pattern was apparent. Mortality probabilities of kids in dewormed groups decreased quickly after birth, but remained elevated up to 9 months of age in the non-dewormed groups. Deworming lowered the risk of mortality. Vaccination alone was not protective (except during an observed outbreak of PPR).

Plasmid and restriction endonuclease patterns in Pasteurella multocida isolated from a swine pyramid.

Restriction endonuclease analysis (REA) and plasmid profile were used to study the epidemiology of Pasteurella multocida in a swine pyramid structure. The studied pyramid was comprised of a group of 12 swine farrow-to-finish farms related by unidirectional animal movement. P. multocida isolates were obtained from the lungs of 275 slaughtered pigs. Serotyping was performed by hyaluronidase sensitivity test and toxicity was investigated by the ELISA test. HpaII was used to cleave the P. multocida extracted DNA. REA patterns relationships were studied using the Sokal-Michener coefficients, and the dendrogram was built using the UPGMA system. The 218 P. multocida isolates obtained were distributed in 17 REA patterns. In 9 of the 12 farms studied only 2-3 REA patterns were detected, with one clearly predominant pattern. The 81 strains with plasmids were assigned to six plasmid profiles. REA and plasmid profiles proved to be good epidemiological tools for identifying different strains of P. multocida with the same phenotype.