''Mycoplasma ovipneumoniae'' is a species of ''

Mycoplasma ''Mycoplasma'' is a genus of bacteria that, like the other members of the class ''Mollicutes'', lack a cell wall around their cell membranes. Peptidoglycan (murein) is absent. This characteristic makes them naturally resistant to antibiotics ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

that most commonly inhabits and affects ovine animals, first described in 1972. M. ovipneumoniae contributes to harmful pneumonia in sheep and goats. The duration and severity of M. ovipneumoniae varies from region to region.

Affected populations

M. ovipneumoniae is a respiratory pathogen of domestic sheep, domestic goats,

Bighorn sheep The bighorn sheep (''Ovis canadensis'') is a species of sheep native to North America. It is named for its large horns. A pair of horns might weigh up to ; the sheep typically weigh up to . Recent genetic testing indicates three distinct subspec ...

, mountain goats, and other Caprinae and can cause both primary atypical pneumonia and also predispose infected animals to secondary pneumonia with other agents, including ''Mannheimia haemolytica''. Recent studies have identified the bacterium in others animals outside of the caprinae family. ''M. ovipneumoniae'' has been detected in bighorn sheep, caribou, mountain goats, Beira antelope, Dall sheep, muskoxen, mule deer, white-tailed deer, and domestic cattle, sheep and goats.

Characteristics

Several mechanisms are involved in the pathogenicity of ''M. ovipneumoniae'', including altering

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

activity, adhering to the

ruminants Ruminants ( suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...

' ciliated epithelium via its polysaccharide capsule, inducing the production of autoantibodies to ciliary

antigens In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

, and suppressive activity on

lymphocytes A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adap ...

, all of which are important factors that contribute to the disease in sheep and other small ruminants. The bacterium also has the ability to act as a predisposing factor for other bacterial and viral infections. Populations of ''M. ovipneumoniae'' of infected sheep are often found to have varying strains of the bacterium within one animal, but the different strains vary in virulence. The bacterium can be found within the

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of th ...

trachea The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...

, and

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal c ...

of small ruminants. ''M. ovipneumoniae'' paralyzes cilia in the airways of the infected animal which doesn't allow them to push out the pneumonia-causing bacteria that has entered the lungs. A combination of this with other environmental factors can cause respiratory disease and increased mortality rates in infected individuals.

Transmission and impacts on susceptible populations

Transmission

In July 2007, this species of ''Mycoplasma'' was linked to the deaths of

in the Western

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. ''M. ovipneumoniae'' is also a predominant bacterium associated with broncopneumonia lesions in free-ranging bighorn lambs. Introductions come from either domestic sheep and goats (which harbour ''M. ovipneumoniae'' with limited morbidity), or through contact with other infected bighorn sheep which survived initial infection events to become long-term chronic carriers. Transmission comes from animal secretions or respiratory droplets. There have been a minimum of thirteen studies where bighorns and domestic sheep were penned together, resulting in 98% bighorn mortality rates. The cause of the issue is when domestic sheep and goats that are infected with ''M. ovipneumoniae'' come into contact with healthy bighorn sheep, this infects them and can cause large population die-offs.

Declining population rates

Once a bighorn population is infected with ''M. ovipneumoniae'', the pathogen is difficult to eliminate, and is associated with stagnant-to-declining population growth rates. ''M. ovipneumoniae'' is also associated with population declines in several other wild caprinae, including the Norwegian Muskox. ''Mycoplasma'' species are labile organisms which are easily destroyed by heat, dehydration, sunlight, and common disinfectants, so they do not survive for a long time outside the body of the animal. As of now, and with many ''Mycoplasma'' diseases, no protective immune responses have been achieved with the use of vaccines, though antibodies can be obtained. Biologists deduced that the greatest limiting factor for

populations is the deadly disease caused by contact with domestic sheep and goats. Domestic sheep are seemingly unaffected by ''M. ovipneumoniae'' and to compound the problems in bighorn sheep, lamb survival can remain dangerously low for decades after an outbreak. Adult bighorns that survive become carriers and pass the disease onto the young lambs.

Symptoms, testing and prevention

Symptoms

The symptoms of ''M. ovipneumoniae'' vary between domestic and bighorn sheep, as well as other caprinae. Symptoms in domestic sheep can range from mild respiratory disease, severe pneumonia and even death. Clinical and subclinical symptoms may be present in domestic sheep. Clinical symptoms may include fever, lethargy, decreased appetite, nasal discharge, coughing, and decreased milk production in ewes. Subtle and often unnoticeable clinical symptoms are present until severe damage associated with secondary bacterial infection sets in. Clinical signs such as fever, lethargy, head shaking, coughing, nasal discharge, and sudden death are common in

possessing ''M. ovipneumoniae.''

Testing options

There are multiple different options for testing caprinae for ''M. ovipneumoniae such as'' antibody-based tests, DNA based tests, and bacteria cultures that can be done.

Polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) t ...

(PCR) detection of ''M. ovipneumoniae,'' indirect hemagglutination (IH), and competitive enzyme-linked immunosorbent assay (cELISA) detection of exposure to ''M. ovipneumoniae'' all exist as options. The detection of ''M. ovipneumoniae'' can be obtained by bacteriologic culture, molecular diagnostics, and serology, allowing for the bacterium to be grown in culture, species-specific DNA sequences, and specific antibodies identified, respectively. If antibodies are present after testing, this indicates that the tested animal has at some point been exposed to ''M. ovipneumoniae'' bacteria, but does not establish alone that the individual is currently infected.

Preventative measures

Although there are no current vaccine options available to prevent ''M. ovipneumoniae,'' the best preventative measure for the disease is keeping wild free-ranging sheep out of contact with domestic sheep and goats. Preliminary research shows that having ''M. ovipneumoniae'' free domestic sheep and goats could be not only be beneficial to bighorns, but to domestic sheep producers as well. Domestic lambs, that are ''M. ovipneumoniae'' free, experience higher daily gains and better carcass traits, which would lead to higher profits for producers and less die-offs in bighorn sheep populations.