Occurrence of autoantibodies to cilia in lambs with a 'coughing syndrome'

The role of Mycoplasma ovipneumoniae and Mycoplasma arginini in the respiratory mycoplasmosis of sheep and goats in Italy: Correlation of molecular data with histopathological features

Mycoplasma infections are commonly found in the respiratory system of small ruminants; the species most commonly detected are Mycoplasma ovipneumoniae and Mycoplasma arginini, associated with the so-called "atypical non-progressive pneumonia". The pathogenic role of M. ovipneumoniae in pneumonia has been demonstrated in sheep but still needs to be verified in goats; on the other hand, the role of M. arginini in sheep is not well understood, while in goats seems to be of low pathogenic value. The present study aims to investigate the aetiology of pneumonia in sheep and goats that died from respiratory disease using anatomopathological, histopathological, and molecular investigations and to clarify the role of respiratory mycoplasmas by the association of molecular data with histopathological features. First, to better understand which histological changes are actually suggestive of atypical pneumonia in sheep and goats, the study identified the histological lesions significantly associated with Mycoplasma spp. infection. Then, the histological score of lesions considered suggestive of atypical pneumonia was used to estimate the pathogenicity of each mycoplasma detected. The results showed that M. ovipneumoniae and M. arginini (alone or in mixed infections) are pathogenic both in sheep, as well as in goats with similar histology and severity of lesions. Moreover, young animals were statistically more susceptible to M.ovipneumoniae and M. arginini infection than adults. Animals appeared more at risk to the development of M. ovipneumoniae and M. arginini infection in summer.

Host vs. pathogen evolutionary arms race: Effects of exposure history on individual response to a genetically diverse pathogen

Introduction

Throughout their range, bighorn sheep (Ovis canadensis) populations have seen significant disease-associated declines. Unfortunately, understanding of the underlying epidemiological processes driving the disease dynamics in this species has hindered conservation efforts aimed at improving the health and long-term viability of these populations. Individual response to pathogen exposure emerges from dynamic interactions between competing evolutionary processes within the host and pathogen. The host’s adaptive immune system recognizes pathogens and mounts a defensive response. Pathogens have evolved strategies to overcome adaptive immune defenses including maintaining high genetic diversity through rapid evolution. The outcomes of this evolutionary warfare determine the success of pathogen invasion of the host and ultimately the success of conservation efforts.

Methods

During an epizootic dominated by a single strain, we explore these host-pathogen dynamics by examining the variation in effects of pathogen invasion on captive bighorn sheep with differing histories of exposure to genetically diverse strains of Mycoplasma ovipneumoniae (Movi). We monitored clinical signs of disease and sampled animals and their environment to detect spread of Movi among 37 bighorn sheep separated into nine pens based on known exposure histories.

Results

We documented Movi transmission within and across pens and we detected Movi DNA in air, water, and invertebrate samples. Higher levels of antibody to Movi prior to the epizootic were associated with a lower likelihood of presenting clinical signs of pneumonia. Nonetheless, higher antibody levels in symptomatic individuals were associated with more severe progressive disease, increased probability and speed of pneumonia-induced mortality, and reduced likelihood of returning to a healthy state. Bighorn sheep with previous exposure to a strain other than the predominant epizootic strain were more likely to recover.

Discussion

Our results indicate that Movi-strain variability was sufficient to overwhelm the adaptive host immunological defenses. This outcome indicates, in free-ranging herds, past exposure is likely insufficient to protect bighorn sheep from infection by new Movi strains, although it influences the progression of disease and recovery within the herd. Therefore, given Movi-strain variability and the lack of immunological protection from past exposure, focusing management efforts on minimizing the introduction of Movi into bighorn herds, through separation of domestic and bighorn sheep and avoidance of management activities that create commingling of bighorn sheep carrying differing Movi strains, will likely be the most effective approach for reducing the effects of disease and achieving bighorn sheep conservation goals.

Mycoplasma ovipneumoniae: A Most Variable Pathogen

Mycoplasma ovipneumoniae, a well-established respiratory pathogen of sheep and goats, has gained increased importance recently because of its detection in wild ruminants including members of the Cervidae family. Despite its frequent isolation from apparently healthy animals, it is responsible for outbreaks of severe respiratory disease which are often linked to infections with multiple heterologous strains. Furthermore, M. ovipneumoniae is characterized by an unusually wide host range, a high degree of phenotypic, biochemical, and genomic heterogeneity, and variable and limited growth in mycoplasma media. A number of mechanisms have been proposed for its pathogenicity, including the production of hydrogen peroxide, reactive oxygen species production, and toxins. It shows wide metabolic activity in vitro, being able to utilize substrates such as glucose, pyruvate, and isopropanol; these patterns can be used to differentiate strains. Treatment of infections in the field is complicated by large variations in the susceptibility of strains to antimicrobials, with many showing high minimum inhibitory concentrations. The lack of commercially available vaccines is probably due to the high cost of developing vaccines for diseases in small ruminants not presently seen as high priority. Multiple strains found in affected sheep and goats may also hamper the development of effective vaccines. This review summarizes the current knowledge and identifies gaps in research on M. ovipneumoniae, including its epidemiology in sheep and goats, pathology and clinical presentation, infection in wild ruminants, virulence factors, metabolism, comparative genomics, genotypic variability, phenotypic variability, evolutionary mechanisms, isolation and culture, detection and identification, antimicrobial susceptibility, variations in antimicrobial susceptibility profiles, vaccines, and control.

Pathophysiology of Influenza D Virus Infection in Specific-Pathogen-Free Lambs with or without Prior Mycoplasma ovipneumoniae Exposure

Polymicrobial pneumonias occur frequently in cattle, swine, and sheep, resulting in major economic losses. Individual pathogens comprising these complex infections may be mild on their own but can instead exhibit synergism or increase host susceptibility. Two examples of such pathogens, Mycoplasma ovipneumoniae (M. ovipneumoniae) and influenza D viruses (IDVs), naturally infect domestic sheep. In sheep, the role of M. ovipneumoniae in chronic nonprogressive pneumonia is well-established, but the pathogenesis of IDV infection has not previously been studied. We utilized a specific-pathogen-free sheep flock to study the clinical response to IDV infection in naïve vs. M. ovipneumoniae-exposed lambs. Lambs were inoculated intranasally with M. ovipneumoniae or mock infection, followed after four weeks by infection with IDV. Pathogen shedding was tracked, and immunological responses were evaluated by measuring acute phase response and IDV-neutralizing antibody titers. While lamb health statuses remained subclinical, M. ovipneumoniae-exposed lambs had significantly elevated body temperatures during IDV infection compared to M. ovipneumoniae-naïve, IDV-infected lambs. Moreover, we found a positive correlation between prior M. ovipneumoniae burden, early-infection IDV shedding, and IDV-neutralizing antibody response. Our findings suggest that IDV infection may not induce clinical symptoms in domestic sheep, but previous M. ovipneumoniae exposure may promote mild IDV-associated inflammation.

Disease Ecology of a Low-Virulence Mycoplasma ovipneumoniae Strain in a Free-Ranging Desert Bighorn Sheep Population

Simple Summary

Like many wildlife diseases, bighorn sheep pneumonia can vary in burden. Here, we report on a bighorn sheep pneumonia event that showed much lower symptom and mortality burdens than have been documented previously. We provide detailed descriptions of symptoms, diagnostic testing results, and mixing patterns throughout the population, and end by discussing mechanisms that could have generated the distinct disease ecology associated with this event.

Abstract

Infectious pneumonia associated with the bacterial pathogen Mycoplasma ovipneumoniae is an impediment to bighorn sheep (Ovis canadensis) population recovery throughout western North America, yet the full range of M. ovipneumoniae virulence in bighorn sheep is not well-understood. Here, we present data from an M. ovipneumoniae introduction event in the Zion desert bighorn sheep (Ovis canadensis nelsoni) population in southern Utah. The ensuing disease event exhibited epidemiology distinct from what has been reported elsewhere, with virtually no mortality (0 adult mortalities among 70 animals tracked over 118 animal-years; 1 lamb mortality among 40 lambs tracked through weaning in the two summers following introduction; and lamb:ewe ratios of 34.9:100 in the year immediately after introduction and 49.4:100 in the second year after introduction). Individual-level immune responses were lower than expected, and M. ovipneumoniae appeared to fade out approximately 1.5 to 2 years after introduction. Several mechanisms could explain the limited burden of this M. ovipneumoniae event. First, most work on M. ovipneumoniae has centered on Rocky Mountain bighorn sheep (O. c. candensis), but the Zion bighorns are members of the desert subspecies (O. c. nelsoni). Second, the particular M. ovipneumoniae strain involved comes from a clade of strains associated with weaker demographic responses in other settings. Third, the substructuring of the Zion population may have made this population more resilient to disease invasion and persistence. The limited burden of the disease event on the Zion bighorn population underscores a broader point in wildlife disease ecology: that one size may not fit all events.

Genes involved in immune, gene translation and chromatin organization pathways associated with Mycoplasma ovipneumoniae presence in nasal secretions of domestic sheep

Mycoplasma ovipneumoniae contributes to polymicrobial pneumonia in domestic sheep. Elucidation of host genetic influences of M. ovipneumoniae nasal detection has the potential to reduce the incidence of polymicrobial pneumonia in sheep through implementation of selective breeding strategies. Nasal mucosal secretions were collected from 647 sheep from a large US sheep flock. Ewes of three breeds (Polypay n = 222, Rambouillet n = 321, and Suffolk n = 104) ranging in age from one to seven years, were sampled at three different times in the production cycle (February, April, and September/October) over four years (2015 to 2018). The presence and DNA copy number of M. ovipneumoniae was determined using a newly developed species-specific qPCR. Breed (P<0.001), age (P<0.024), sampling time (P<0.001), and year (P<0.001) of collection affected log₁₀ transformed M. ovipneumoniae DNA copy number, where Rambouillet had the lowest (P<0.0001) compared with both Polypay and Suffolk demonstrating a possible genetic component to detection. Samples from yearlings, April, and 2018 had the highest (P<0.046) detected DNA copy number mean. Sheep genomic DNA was genotyped with the Illumina OvineHD BeadChip. Principal component analysis identified most of the variation in the dataset was associated with breed. Therefore, genome wide association analysis was conducted with a mixed model (EMMAX), with principal components 1 to 6 as fixed and a kinship matrix as random effects. Genome-wide significant (P<9x10^-8) SNPs were identified on chromosomes 6 and 7 in the all-breed analysis. Individual breed analysis had genome-wide significant (P<9x10^-8) SNPs on chromosomes 3, 4, 7, 9, 10, 15, 17, and 22. Annotated genes near these SNPs are part of immune (ANAPC7, CUL5, TMEM229B, PTPN13), gene translation (PIWIL4), and chromatin organization (KDM2B) pathways. Immune genes are expected to have increased expression when leukocytes encounter M. ovipneumoniae which would lead to chromatin reorganization. Work is underway to narrow the range of these associated regions to identify the underlying causal mutations.

Comparison of phenotypic and genotypic profiles among caprine and ovine Mycoplasma ovipneumoniae strains

Mycoplasma ovipneumoniae (Movp) is considered to be one of the most important mycoplasmas causing respiratory disease in small ruminants. Most epidemiologic and characterisation studies have been conducted on strains collected from sheep. Information on the presence and characteristics of Movp in healthy and pneumonic goats is limited. Phenotypic or genotypic differences between sheep and goat isolates have never been studied. The objective of our study was to characterise and compare the similarities and differences between caprine and ovine Movp strains isolated from affected and asymptomatic animals in order to elucidate phenotypic and genotypic variability. Four different techniques were used on a set of 23 Movp isolates. These included SDS-PAGE, Western blotting, random amplified polymorphic DNA and the heat shock protein 70 gene sequence-based method. A high degree of phenotypic and genotypic heterogeneity among Movp strains was demonstrated in this study. Our results demonstrated differences between goat and sheep strains, revealing not only a link between strains and host ruminant species, but by geographical origin as well. However, the finding of immunodominant antigens of molecular masses 36, 38, 40 and 70 kDa (±3 kDa) in Movp isolates from sheep and goats foretells their potential use in the development of serological diagnostic tests and vaccines.

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.

Mycoplasma ovipneumoniae can predispose bighorn sheep to fatal Mannheimia haemolytica pneumonia

Mycoplasma ovipneumoniae has been isolated from the lungs of pneumonic bighorn sheep (BHS). However experimental reproduction of fatal pneumonia in BHS with M. ovipneumoniae was not successful. Therefore the specific role, if any, of M. ovipneumoniae in BHS pneumonia is unclear. The objective of this study was to determine whether M. ovipneumoniae alone causes fatal pneumonia in BHS, or predisposes them to infection by Mannheimia haemolytica. We chose M. haemolytica for this study because of its isolation from pneumonic BHS, and its consistent ability to cause fatal pneumonia under experimental conditions. Since in vitro culture could attenuate virulence of M. ovipneumoniae, we used ceftiofur-treated lung homogenates from pneumonic BHS lambs or nasopharyngeal washings from M. ovipneumoniae-positive domestic sheep (DS) as the source of M. ovipneumoniae. Two adult BHS were inoculated intranasally with lung homogenates while two others received nasopharyngeal washings from DS. All BHS developed clinical signs of respiratory infection, but only one BHS died. The dead BHS had carried leukotoxin-positive M. haemolytica in the nasopharynx before the onset of this study. It is likely that M. ovipneumoniae colonization predisposed this BHS to fatal infection with the M. haemolytica already present in this animal. The remaining three BHS developed pneumonia and died 1-5 days following intranasal inoculation with M. haemolytica. On necropsy, lungs of all four BHS showed lesions characteristic of bronchopneumonia. M. haemolytica and M. ovipneumoniae were isolated from the lungs. These results suggest that M. ovipneumoniae alone may not cause fatal pneumonia in BHS, but can predispose them to fatal pneumonia due to M. haemolytica infection.

Global suppression of mitogen-activated ovine peripheral blood mononuclear cells by surface protein activity from Mycoplasma ovipneumoniae

Mycoplasma ovipneumoniae is associated with chronic non-progressive pneumonia of sheep and goats. As with many other mycoplasmas involved in animal diseases, protective immune responses have not been achieved with vaccines, even though antibody responses can be obtained. This study focuses on characterizing the interaction of M. ovipneumoniae with ovine PBMC using carboxy-fluorescein-succinimidyl-ester (CFSE) loading and flow cytometry to measure lymphoid cell division. M. ovipneumoniae induced a strong in vitro polyclonal suppression of CD4(+), CD8(+), and B blood lymphocyte subsets. The suppressive activity could be destroyed by heating to 60 degrees C, and partially impaired by formalin and binary ethyleneimine treatment that abolished its viability. The activity resided on the surface-exposed membrane protein fraction of the mycoplasma, since mild trypsin treatment not affecting viability was shown to reduce suppressive activity. Trypsin-treated mycoplasma regained suppressive activity once the mycoplasma was allowed to re-synthesize its surface proteins. Implications for the design of vaccines against M. ovipneumoniae are discussed.

Isolation and immunological detection of Mycoplasma ovipneumoniae in sheep with atypical pneumonia, and lack of a role for Mycoplasma arginini

Mycoplasma ovipneumoniae NCTC 10151(T) and four new isolates from UK sheep flocks were compared. Only glucose and pyruvate were used as energy sources by the five strains: glucose was the best energy source for the type strain, pyruvate supported better growth of the new strains. Whole cell protein patterns and antigenic profiles showed high similarity between all five strains. The new isolates fell into two groups in ELISA tests. Serum samples from 30 pneumonic sheep were assessed for M. ovipneumoniae infection and Mycoplasma arginini co-infection. Fourteen (out of 30) serum samples were positive for M. ovipneumoniae both by ELISA and immunoblotting. Twelve antigenic proteins of M. ovipneumoniae were detected in infected serum samples: the antigen patterns were unique, with between one and at least seven occurring in any one sample. All serum samples were designated as negative for M. arginini antibodies by both ELISA and immunoblotting.

A high level of strain variation within the Mycoplasma ovipneumoniae population of the UK has implications for disease diagnosis and management

Mycoplasma ovipneumoniae is one of only two mycoplasma species associated with small ruminant disease in Britain and has been associated with an increasing number of disease outbreaks since 2002. This investigation used well-defined techniques to assess the variability of UK M. ovipneumoniae isolates, in an attempt to identify strain clusters within the population. Strains received for routine diagnosis between 2002 and 2004 were analysed using random amplified polymorphic DNA (RAPD) and pulsed field gel electrophoresis (PFGE). Of the 43 samples screened 40 RAPD Hum-1, 41 RAPD Hum-4 and 40 PFGE profiles were observed. Composite data analysis divided strains into 10 similarity clusters with SDS-PAGE and Western blotting indicating that this DNA variability is translated into a pattern of variable protein expression. In order to assess the strains isolated within flocks two sets of samples, from diverse locations, were included in this test panel. The presence of variable isolates existing on the same farm may reflect animal movement and the introduction of asymptomatic, carrier, animals where M. ovipneumoniae is already established within a flock. These findings have significant implications regarding disease diagnosis and management.

Mycoplasma infections in small ruminants

Mycoplasmas have complex mechanisms of antigenic variation that allow them to evade the immune system. These organisms cause a variety of clinical syndromes that can have a significant economic effect on small ruminant production. The syndromes range from acute septicemia and death to chronic infection resulting in decreased production. Recent research findings have shed light on the means by which these organisms evade the host immune response and cause or contribute to the development of disease in the host. This article provides a review of the pathogenesis, clinical signs, and treatment options for common disease syndromes involving Mycoplasma spp. in small ruminants.

Differential serologic response to Mycoplasma ovipneumoniae and Mycoplasma arginini in lambs affected with chronic respiratory disease

An enzyme-linked immunoabsorbent assay (ELISA) was used to evaluate the levels of antibodies to Mycoplasma ovipneumoniae and M. arginini in lambs with chronic respiratory disease. Sera were obtained from lambs in several flocks at various stages of the clinical disease and tested with sodium dodecyl sulfate (SDS)-treated M. ovipneumoniae and M. arginini whole cells and a crude capsular extract of M. ovipneumoniae as the antigens. There were low levels of antibody to M. ovipneumoniae in flocks sampled at the early stages of infection, whereas increased levels of antibody were present in lambs from flocks that had apparently recovered from the clinical disease. Slowly rising titers of circulating antibodies to M. ovipneumoniae were confirmed by sequential bleeding of lambs during the course of the clinical disease. However, antibody levels of M. arginini were more likely to increase earlier in the disease process. There was significant cross-reactivity between the 2 SDS-treated antigens in both the ELISA test and western immunoblotting. In contrast, the crude capsular extract was specific for detecting antibodies to M. ovipneumoniae.