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Non-haemotropic mycoplasmas can be found on the mucous membranes of the respiratory and the urogenital tract (mucosa-associated mycoplasmas), where they can escape from the immune response of the infected animal for a very long time. Conjunctivitis and rhinitis are clinically apparent, disorders of the upper respiratory tract occur less frequently. Mycoplasmas can also be primarily pathogenic.
Mycoplasmas often occur in dog populations and are sometimes considered as commensals in the literature. Yet, they are also associated with diseases of the urogenital region and with infertility. Clinically, an infection with canine mycoplasma can cause prostatitis and/or orchitis in male dogs, and can, amongst others, lead to endometritis in female dogs. However, mycoplasmas may also play a role in canine respiratory diseases.
As it is difficult to cultivate mycoplasma, PCR detection is the method of choice.
In the cat common cold complex, not only viral components (FHV, FCV) play a role, but also Mycoplasma felis. Clinically, an infection is usually manifested by conjunctivitis and rhinitis. Mycoplasma gatae and Mycoplasma feliminutum are sometimes isolated from cats, nevertheless, their clinical relevance is questionable.
Mycoplasma pulmonis is the causative agent of “murine respiratory mycoplasmosis” in rats and mice, a slowly progressing infection of the respiratory tracts associated with the formation of thick mucus. Clinical signs of infected animals are sneezing, mucopurulent nasal discharge, stertorous breathing sounds and dyspnoea. The infection can spread to the middle ear and lead to otitis media and head tilt.
In addition, especially in older female rats, Mycoplasma pulmonis can cause genital infection which leads to infertility or a small litter size. In rare cases, metritis or pyometra are also seen.
Latent infections without any clinical signs are common.
Transmission occurs through aerosols in close direct contact. Sexual or intrauterine transmission is also possible.
Several Mycoplasma spp. exist in tortoises. An infection with a virulent Mycoplasma agassizii strain causes the so-called upper respiratory tract disease (URTD), a disease clinically characterised by serous, mucous and purulent nasal discharge as well as ocular discharge, conjunctivitis and eyelid oedema. Furthermore, it can cause lethargy, dehydration, anorexia and fatal cachexia. An essential trait of mycoplasma infections is the fact that they can persist in the organism without triggering any symptoms. Often, the disease only breaks out if there are other microorganisms and environmental factors involved, combined with the genetic properties and immune reactions of the host.
Mycoplasmas are also detected in turtles and other reptiles, especially pythons, but little is known about their clinical relevance.
In the first weeks of the life of a calf, Mycoplasma bovis can cause mostly enzootic pneumonia and arthritis, and in cows it leads to severe mastitis.
Affected calves typically suffer from otitis with hanging earlobes and head tilt. As mastitis pathogen, Mycoplasma bovis is highly infectious. Typically, the mammary gland increases in size and hardens, and within a few weeks, the inflammation spreads to the neighbouring udder quarters.
The pathogen is also often detected in connection with chronic diseases of the respiratory tract. Reservoirs of M. bovis are the respiratory tract of clinically healthy calves and young cattle as well as the udder of cows with subclinical mastitis.
Mycoplasma mycoides subsp. mycoides is the causative agent of contagious bovine pleuropneumonia (notifiable upon suspicion in Germany).
Mycoplasma hyopneumoniae is the primary causative agent of enzootic porcine pneumonia (EPP). EPP is one of the most significant causes of respiratory infectious diseases in pigs. The disease is globally distributed. However, the pathogen only causes high economic losses in pig production when combined with poor environmental conditions and secondary bacterial and/or viral infections.
Infections with Mycoplasma gallisepticum cause the so-called chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys. Infection occurs both horizontally through the air and direct contact as well as vertically through hatching eggs.
The main symptoms include chronic inflammation of the upper respiratory tracts and air sacs, accompanied by disorders of the joints, tendon sheaths and the genital tract. Central nervous disorders can also arise. In addition, laying performance and hatching rates decrease significantly.
Mixed infections with viral pathogens, such as Newcastle disease virus (NDV) or infectious bronchitis virus (IBV) are not unusual and can severely aggravate the clinical picture (also as vaccine viruses).
In chickens and turkeys, Mycoplasma synoviae causes infectious synovitis and arthritis, which is clinically manifested by joint swellings and lameness. Inflammations of the air sacs, myocardium and pericardium also occur. Especially after mixed infections, respiratory symptoms can be seen as well. Stunted growth, reduced laying performance and greenish diarrhoea are also due to the infection. Besides game birds, geese, too, are susceptible to this pathogen.
