Emergence of fatal Mannheimia haemolytica infections in cattle in the Netherlands.

In the Dutch national surveillance system, outbreaks of fatal infections by Mannheimia haemolytica (M. haemolytica) in dairy cows and veal calves have become apparent in recent years. These observations prompted an in-depth analysis of available pathology data over the period 2004-2018 to investigate changes in the occurrence and/or expression of M. haemolytica-associated cattle disease. With multilevel logistic regression models, time trends were identified and corrected for farm, season, pathologist and region. Deaths associated with M. haemolytica infection increased over time with dairy cows and veal calves diagnosed with fatal M. haemolytica infections 1.5 and 1.4 times more frequently every following 3-year period between 2004 and 2018, respectively. M. haemolytica-associated disease showed two distinct disease presentations: acute pleuropneumonia in dairy cows and polyserositis in veal calves. The prevalence of both disease presentations with M. haemolytica confirmed increased in each 3-year time period between 2004 and 2018, with an odds ratio (OR) of 1.5 for acute pleuropneumonia in dairy cows and an OR of 1.7 for polyserositis in veal calves. No change was found for M. haemolytica-associated disease in dairy calves. Although M. haemolytica is considered an opportunist bovine pathogen, and the presence of primary pathogens such as BHV-1, BVDV and Mycoplasma species was not completely ruled out in our study, substantial evidence is provided to indicate infections with M. haemolytica were the most likely cause of death. M. haemolytica-associated diseases occurred more often in October-June than July-September, and were detected more often in necropsied animals from the North, South and East Netherlands than the West Netherlands.

Stress significantly increases mortality following a secondary bacterial respiratory infection.

A variety of mechanisms contribute to the viral-bacterial synergy which results in fatal secondary bacterial respiratory infections. Epidemiological investigations have implicated physical and psychological stressors as factors contributing to the incidence and severity of respiratory infections and psychological stress alters host responses to experimental viral respiratory infections. The effect of stress on secondary bacterial respiratory infections has not, however, been investigated. A natural model of secondary bacterial respiratory infection in naive calves was used to determine if weaning and maternal separation (WMS) significantly altered mortality when compared to calves pre-adapted (PA) to this psychological stressor. Following weaning, calves were challenged with Mannheimia haemolytica four days after a primary bovine herpesvirus-1 (BHV-1) respiratory infection. Mortality doubled in WMS calves when compared to calves pre-adapted to weaning for two weeks prior to the viral respiratory infection. Similar results were observed in two independent experiments and fatal viral-bacterial synergy did not extend beyond the time of viral shedding. Virus shedding did not differ significantly between treatment groups but innate immune responses during viral infection, including IFN-γ secretion, the acute-phase inflammatory response, CD14 expression, and LPS-induced TNFα production, were significantly greater in WMS versus PA calves. These observations demonstrate that weaning and maternal separation at the time of a primary BHV-1 respiratory infection increased innate immune responses that correlated significantly with mortality following a secondary bacterial respiratory infection.

Cross protection of a Mannheimia haemolytica A1 Lkt-/Pasteurella multocida ΔhyaE bovine respiratory disease vaccine against experimental challenge with Mannheimia haemolytica A6 in calves.

Bovine respiratory disease causes significant economic losses in both beef and dairy calf industries. Although multi-factorial in nature, the disease is characterized by an acute fibrinous lobar pneumonia typically associated with the isolation of Mannheimia haemolytica. M. haemolytica A1 and A6 are the two most commonly isolated serotypes from cattle, however, the majority of vaccines have not demonstrated cross-serotype protection. In the current study, the efficacy of a novel, attenuated live vaccine, containing both M. haemolytica serotype A1 and Pasteurella multocida, was evaluated in calves challenged with M. haemolytica serotype A6. Although the challenge was more severe than expected, vaccinated calves had reduced clinical scores, lower mortality, and significantly lower lung lesion scores compared to the placebo-vaccinated control group. The results demonstrate that vaccination with an attenuated live vaccine containing M. haemolytica serotype A1 can protect calves against clinical disease following challenge with M. haemolytica serotype A6.

Transmission of Mannheimia haemolytica from domestic sheep (Ovis aries) to bighorn sheep (Ovis canadensis): unequivocal demonstration with green fluorescent protein-tagged organisms.

Previous studies demonstrated that bighorn sheep (Ovis canadensis) died of pneumonia when commingled with domestic sheep (Ovis aries) but did not conclusively prove that the responsible pathogens were transmitted from domestic to bighorn sheep. The objective of this study was to determine, unambiguously, whether Mannheimia haemolytica can be transmitted from domestic to bighorn sheep when they commingle. Four isolates of M. haemolytica were obtained from the pharynx of two of four domestic sheep and tagged with a plasmid carrying the genes for green fluorescent protein (GFP) and ampicillin resistance (AP(R)). Four domestic sheep, colonized with the tagged bacteria, were kept about 10 m apart from four bighorn sheep for 1 mo with no clinical signs of pneumonia observed in the bighorn sheep during that period. The domestic and bighorn sheep were then allowed to have fence-line contact for 2 mo. During that period, three bighorn sheep acquired the tagged bacteria from the domestic sheep. At the end of the 2 mo of fence-line contact, the animals were allowed to commingle. All four bighorn sheep died 2 days to 9 days following commingling. The lungs from all four bighorn sheep showed gross and histopathologic lesions characteristic of M. haemolytica pneumonia. Tagged M. haemolytica were isolated from all four bighorn sheep, as confirmed by growth in ampicillin-containing culture medium, PCR-amplification of genes encoding GFP and Ap(R), and immunofluorescent staining of GFP. These results unequivocally demonstrate transmission of M. haemolytica from domestic to bighorn sheep, resulting in pneumonia and death of bighorn sheep.

Fatal pneumonia epizootic in musk ox (Ovibos moschatus) in a period of extraordinary weather conditions.

The musk ox is adapted to extreme cold and regarded as vulnerable to the impacts of climate change. Population decline is proposed to occur due to changes in forage availability, insect harassment, parasite load, and habitat availability, while the possible role of infectious diseases has not been emphasized. The goal of the present article is to describe an outbreak of fatal pasteurellosis that occurred in the introduced musk ox population of Dovrefjell, Norway in 2006, causing the death of a large proportion of the animals. The epizootic coincided with extraordinary warm and humid weather, conditions that often are associated with outbreaks of pasteurellosis. The description is based on long series of data from the surveillance of the musk ox population, weather data from a closely located meteorological station, and pathoanatomical investigation of the diseased animals. It is concluded that the weather conditions likely were the decisive factors for the outbreak. It is suggested that such epizootics may occur increasingly among cold-adapted animals if global warming results in increased occurrence of heat waves and associated extreme weather events, thereby causing population declines and possibly extinctions.

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.

An evaluation of the relative efficacy of tulathromycin for the treatment of undifferentiated fever in feedlot calves in Nebraska.

A field trial was performed under commercial feedlot conditions in central Nebraska to assess the relative efficacy of tulathromycin (TULA) to florfenicol (FLOR) for the treatment of undifferentiated fever (UF) in feedlot calves that did not receive a metaphylactic antimicrobial or vaccines/bacterins containing Mannheimia haemolytica or Histophilus somni at feedlot arrival by comparing animal health, feedlot performance, and carcass characteristic variables. Two hundred recently weaned, auction market derived, crossbred beef calves that met the study-specific case definition of UF were randomly allocated in a 1:1 ratio to 1 of 2 experimental groups as follows: TULA, which received tulathromycin administered subcutaneously at the rate of 2.5 mg/kg body weight (BW) once at the time of allocation; or FLOR, which received florfenicol administered subcutaneously at the rate of 40 mg/kg BW once at the time of allocation. In terms of animal health, the first UF relapse (RR = 0.65), overall mortality (RR = 0.33), and BRD mortality (RR = 0.29) rates in the TULA group were significantly (P < 0.05) lower than in the FLOR group. There were no significant (P > or = 0.05) differences between the TULA and FLOR groups for the other animal health variables measured. There was no significant (P > or = 0.05) difference in average daily gain between the TULA and FLOR groups. There were no significant (P > or = 0.05) differences in the overall distributions of quality grade and yield grade between the experimental groups; however, a significantly (P < 0.05) higher proportion of carcasses in the TULA group graded yield grade USDA-4 as compared with the FLOR group. In the economic analysis, the benefits observed resulted in an economic advantage of $52.50 USD/animal in the TULA group due to lower first UF relapse and overall mortality rates, even though the occurrence of yield grade USDA-4 carcasses increased and the initial UF treatment cost was higher.

Naturally occurring Mycoplasma bovis-associated pneumonia and polyarthritis in feedlot beef calves.

Mycoplasma bovis is perceived as an emerging cause of mortality in feedlot beef cattle. This study examined the lesions and infectious agents in naturally occurring M. bovis-associated bronchopneumonia and arthritis and the relationship of this condition with bovine viral diarrhea virus (BVDV) infection. Standardized pathologic, immunohistochemical, and microbiologic investigations were conducted on 99 calves that died or were euthanized within 60 days after arrival in 72 feedlots. Cranioventral bronchopneumonia with multiple foci of caseous necrosis was identified in 54 of 99 calves, including 30 with concurrent fibrinosuppurative bronchopneumonia typical of pneumonic pasteurellosis. Mycoplasma bovis was consistently identified in these lesions by culture and immunohistochemistry, but also commonly in healthy lungs and those with pneumonia of other causes. Focal lesions of coagulation necrosis, typical of pneumonic pasteurellosis, were often infected with both Mannheimia haemolytica and M. bovis. Arthritis was present in 25 of 54 (46%) calves with M. bovis pneumonia, and all calves with arthritis had pneumonia. BVDV infection was more common in calves with lesions of bacterial pneumonia than in those dying of other causes, but BVDV infection was not more common in calves with caseonecrotic bronchopneumonia than those with fibrinosuppurative bronchopneumonia. Retrospective analysis identified cases of M. bovis pneumonia in the early 1980s that had milder lesions than the current cases. The findings suggest that, in at least some calves, M. bovis induces caseonecrotic bronchopneumonia within the lesions of pneumonic pasteurellosis.

Evaluation of a multivalent Pasteurella haemolytica vaccine in bighorn sheep: protection from experimental challenge.

The efficacy of a multivalent Pasteurella haemolytica vaccine (A1, A2, T10) in reducing morbidity and mortality associated with pneumonic pasteurellosis in bighorn sheep (Ovis canadensis) was examined. Fifteen captive bighorns were divided equally into three treatment groups based on vaccination status: control (no vaccination), one dose 10 days prior to challenge, or one or two doses 57 wk prior to challenge. At challenge, each bighorn received about 6.2 x 10(7) colony forming units of P. haemolytica (biotype T, serotype 10, biogroup 4-CDS; ribotype ECO; "Alamosa Canyon" strain) suspension sprayed into the proximal trachea. Vaccination reduced (P = 0.1) mortality in bighorns vaccinated 10 days prior to challenge as compared to controls. Although mortality rates in bighorns vaccinated 57 wk prior to challenge did not differ from controls (P = 0.26), a trend in reduced mortality was apparent. Ranked cumulative postmortem scores based on observed gross lesions and bacteriology did not differ (P > or = 0.14) between vaccinated animals and control animals. Neutralizing antibody titers to P. haemolytica leukotoxin were elevated (P = 0.003) at challenge in bighorns vaccinated 10 days before challenge, and neutralizing titers in bighorns from both vaccinated groups were elevated at death < or = 7 days after challenge (P < or = 0.004). In contrast, agglutinating antibody titers to P. haemolytica serotype A1 or T10 surface antigens did not differ between vaccinated and unvaccinated bighorns (P > or = 0.19). Based on these data, we believe that this experimental P. haemolytica vaccine is safe and can stimulate protective immunity from pneumonic pasteurellosis in bighorn sheep. Further evaluation of this vaccine as a tool in preventing and managing pasteurellosis in wild bighorn sheep appears warranted.

Pneumonic pasteurellosis associated with Pasteurella haemolytica in chipmunks (Tamias sibiricus).

A laboratory study was performed in order to identify the possible cause of death in chipmunks (Tamias sibiricus) imported from China with respiratory disease. Severe congestion, alveolar oedema and fibrinous pleuritis were observed. Biochemical analyses identified the causative organism as Pasteurella haemolytica. An in vitro susceptibility test using various antimicrobial agents revealed sensitivity to beta-lactams (ampicillin and amoxicillin) and streptomycin.

The pattern of fatal fibrinous pneumonia (shipping fever) affecting calves in a large feedlot in Alberta (1985-1988).

Data from a retrospective field study were used to describe the epidemiology of fatal fibrinous pneumonia as it affected beef calves entering a large commercial feedlot in southwestern Alberta during the fall months of y 1985 to 1988. A chute-side computer system was used to record processing and health data on 58885 calves during this period. The large annual variation (10%-57%) in the proportion of total mortality due to fibrinous pneumonia indicated that crude mortality cannot be used in epidemiological studies as a surrogate measure of fibrinous pneumonia mortality. Yearly epidemic curves for fatal fibrinous pneumonia were very similar, with a short time interval (median, 19-22 d) between arrival and fatal disease. Fully 75% of the calves that died of fibrinous pneumonia already were sick within 2 weeks of arrival. Studies of the biological, environmental, and population factors that are present before and shortly after arrival at the feedlot are needed to identify strategies for reducing the incidence of fatal fibrinous pneumonia.

Effect of transportation on fatal fibrinous pneumonia and shrinkage in calves arriving at a large feedlot.

A retrospective, epidemiologic field study was performed to determine whether calves that were transported greater distances from the auction market to the feedlot were at significantly higher risk of developing fatal fibrinous pneumonia (shipping fever). The study involved all 45,243 springborn steer calves that were purchased from auction markets and moved into a large commercial feedlot between September 1 and December 31 over a 4-year period (1985-1988). For all 4 years of the study, the distance calves were transported from the market to the feedlot and their shrinkage or subsequent death loss from fibrinous pneumonia were not correlated. The risk of fatal fibrinous pneumonia for calves arriving from nearby markets was just as high as that for calves transported much greater distances. The results suggested that calves can be purchased from more distant markets without having to discount their price for higher expected death losses. Differences between short and long hauls explained little, if any, of the variation among truckloads of calves in the risk of fatal fibrinous pneumonia.

Effect of pretransit mixing on fatal fibrinous pneumonia in calves.

A retrospective, epidemiologic study was performed to quantify the mixing of calves from various sources at auction markets, and to determine whether mixing at the markets and the risk of fatal fibrinous pneumonia (FFP) at the feedlot were associated. In this study, 32,646 spring-born steer calves that entered a single large feedlot during the fall seasons between 1985 and 1988 were traced back to their originating auction market, and sales tickets were used to measure the number of farm sources that contributed to each truckload of calves. Individual cow/calf producers contributed a median of only 2 calves/truckload arriving at the feedlot in this study. An average truckload of 60 steers comprised calves from as many as 20 to 30 farms. The degree of mixing varied little over time and could not, therefore, be used to explain the large variations in FFP risk during different months and different years of the study. However, variation in the degree of mixing of calves from various sources at the markets evidently was responsible for differences in FFP risk among truckloads assembled by different buyers. When truckloads were grouped by buyer, FFP risk and mean number of calves per source were negatively correlated in 1986 (r = -0.67, P = 0.099), and in 1987 (r = -0.90, P = 0.002). These variables also were negatively correlated in 1988 (r = -0.56), although the correlation was not significant. The positive linear relationship between mixing of calves in truckloads supplied by different buyers and subsequent FFP risk suggested that veterinarians and feedlot owners should more aggressively observe and treat calves from truckloads that were highly mixed.(ABSTRACT TRUNCATED AT 250 WORDS)