Ureaplasma infections

Identity

Preferred Scientific Name

• Ureaplasma infections

International Common Names

• English: abortion; blockage of uterine tubes, oviducts, salpingitis; bovine mycoplasma conjunctivitis; endemic pneumonia in calves; endometritis; endometritis, metritis, cervicitis, in gilts and sows; genital ureaplasma infections in ewes; granular vulvitis; granular vulvovaginitis of cattle, goats and sheep; impaired spermatozids and seminal vesiculitis in bulls; infertility; pustular vulvovaginitis, seminal vesiculitis, balanopostitis and fetal alveolitis in cattle; respiratory disease; salpingitis; Ureaplasma diversum associated reproductive disease

Overview

While few laboratories isolate and identify mycoplasmas regularly, even fewer are capable of detecting ureaplasmas because of their unusual and fastidious growth requirements. The existence of ureaplasmas, formerly known as T (for tiny) strains was first recognized in humans nearly 50 years ago (Shepard, 1954). Their possession of the urease enzyme made them unique amongst mollicutes and led to their reclassification within the new genus, Ureaplasma, which now contains 7 species that occur in mammals.

Three species of ureaplasmas play a major role in disease in animals and man: Ureaplasma diversum, a cause of pneumonia, vulvovaginitis, conjunctivitis, infertility and abortion in cattle and pneumonia in swine; and U. urealyticum and Ureaplasma parvum, which can severely affect human neonates. Uncharacterized ureaplasma species are also frequently isolated from the reproductive and respiratory tracts of small ruminants where their role in disease is unclear. Ureaplasmas may also be found in pigs, chickens, cats and dogs.

Within the Mollicute Class, ureaplasmas are grouped within the Order I Mycoplasmatales and Family Mycoplasmataceae but comprise their own genus II, Ureaplasma. To date there are seven named species and some as yet unclassified ureaplasmas: U. urealyticum (man) which previously included the species now known as Ureaplasma parvum, U. diversum (cattle), U. gallorale (poultry), U. canigenitalium (dog), U. cati (cat), U. felinum (cat), and U. species (sheep, goats). Phylogenetically they are very close to mycoplasmas; U. urealyticum has been placed within the Pneumoniae group on the basis of its 16S rRNA gene sequence.

Hosts/Species Affected

While cattle are the major species affected, sheep, goats, camels, pigs and poultry also possess ureaplasmas. A number of isolations have also been made from cats and dogs in Japan (Haraswa et al, 1990).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Pathology

Genital disease in the female is characterized by a purulent vulvar discharge and inflamed hyperaemic vulvar mucosa with varying degrees of granularity (Ross, 1993). Gross lesions in the placenta consist of marked fibrotic thickening of large areas of the amnion and intercotyledonary zones in the chorioallantoic membrane infiltrated by mononuclear cells. There may be foci of fibrin exudation and haemorrhage. In aborted foetuses, microscopic lesions of alveolitis and placentitis may be seen and the antigen may be found in the zona pellucida of the embryo. Ureaplasma diversum was also linked with destructive polyarthropathy with fibrillation and erosion of articular cartilage deformation of articular surfaces, and proliferation of periarticular soft tissue in aborted bovine foetuses (Himsworth et al., 2009).

Respiratory disease involving ureaplasmas is largely subclinical. However, following endobronchial, but not aerosol, infection of gnotobiotic calves, thick cuffs of lymphoid cells and macrophages surrounding the bronchi, bronchioles and blood vessels develop along with a lobular catarrhal pneumonia (Laak et al, 1993a). These results confirmed earlier studies by Gourlay et al. (1979). Macroscopic lesions seen in U. diversum-associated-respiratory-disease consisted of red consolidation in the cranioventral areas of the lung (Ross, 1993). In the lung there is a diffuse alveolitis and focal lymphocytic accumulations around the airways. The alveolitis is characterized by degeneration and necrosis of the alveolar epithelium and there is infiltration of macrophages and granulocytes (Ruhnke, 1994).

Marques et al. (2010) demonstrated in vitro that Ureaplasma diversum adhered to and invaded Hep-2 cells, but did not invade the cell nuclei.

Diagnosis

Clinical signs of granular vulvitis are considered suggestive of ureaplasma infections while other signs such as subclinical pneumonia or conjunctivitis are far less definitive. Consequently laboratory diagnosis is necessary to determine the causative agent. Isolation of ureaplasmas in the genital tract is most successful from cultures of vulval swabs. The transient colonization of the uterus makes sampling this region unreliable. Preputial swabs should be taken with a guarded unit to obtain the sample from as far into the cavity as possible. Semen should be collected following disinfection of the prepuce and should ideally be fresh or kept in liquid nitrogen until ready to culture. Preferred tissues from embryos include the lung, caruncle, cotyledon, stomach contents and amniotic fluid.

From respiratory cases, nasal swabs, lung lavage fluids and lung tissue can be taken. Laak et al (1992a) found considerably higher levels in lavage fluids than nasal swabs. The appropriate transport medium for samples is crucial and antibiotics such as streptomycin and gentamycin, commonly used in many media may prove harmful to ureaplasmas. Recommended media include sucrose phosphate broth (2SP) or standard liquid medium (SLM) (Furr, 1998).

Media recommended for the primary culture of U. diversum differ from those for other mycoplasmas by containing 1% urea instead of glucose or arginine and having an adjusted pH of approximately 7.0. However there are many variations in exact composition of ureaplasma media. Whitford et al. (1994) list the composition of several media which have given good results including U4 buffered broth medium. Laak et al. (1992a) used Friis Media HAU and NHU and A7B agar medium which enabled the production of manganese dioxide as a brown deposit when urea was hydrolyzed; however HAU and NHU were superior to A7B when all three were used in parallel. Commercial media is now available for ureaplasma isolation (Mycoplasma Experience, Reigate, UK).

Once isolated, ureaplasmas can be identified by the production of brown colonies on agar medium containing manganese sulphate due to the deposition of manganese on the surface of the colony. Isolates can be serotyped by immunofluorescence on colonies grown on agar medium (Howard and Gourlay, 1981).

A PCR, based on the 16S rRNA gene, was more sensitive and rapid than culture for detecting U. diversum in vaginal swabs of cattle (Cardoso et al., 2000). This test offers a lot of advantages over traditional culture techniques. More recently, quantitative TaqMan PCR assays, still based on the 16S rRNA gene, have been developed (Marques et al., 2013).

Serological tests are not widely available for ureaplasmas and may be complicated by the existence of different serogroups. However, an indirect haemagglutination test was described for U. diversum by Nagatomo et al. (1996).

List of Symptoms/Signs

Disease Course

Acute granular vulvitis is characterized by an inflamed hyperaemic vulvar mucosa with small raised granules usually clustered around the clitoris. A purulent discharge may begin 3 days after infection and may last up to 2 weeks. The disease then becomes chronic with a reduction in clinical signs; however the ureaplasma can be isolated from the vulva for up to 7 months (Ruhnke, 1994). There may also be a transient colonisation of the uterus. During acute disease, the endometrium and/or fallopian tubes may become permanently damaged leading to infertility (Kreplin and Maitland, 1989). In some cases embryo death or abortion usually in the first and the last trimester, still birth or extremely weak calves that die shortly after birth with respiratory failure, may result as a consequence of ureaplasma infection (Ruhnke, 1994).

In studies of experimentally infected heifers using broth cultures of U. diversum or vaginal swabs from previously infected heifers, all animals developed granular vulvovaginitis; U. diversum was isolated from the vagina, urinary bladder and urethra. The pathogenicity of U. diversum increased with consecutive passages, making the incubation period shorter and clinical symptoms more pronounced (Pilaszek and Truszczynsk, 1991).

Experimental infections of sheep with Ureaplasma parvum, a Ureaplasma species associated with pre-term delivery in women, did not cause sustained effects on air space or vascular development in premature lambs (Polglase et al., 2010).

Epidemiology

Numerous studies have shown that U. diversum plays an important role in bovine reproductive failure (Ruhnke, 1994). Clinical signs include granular vulvitis, endometritis, salpingitis, abortion, infertility in the female and seminovesiculitis; all conditions have been reproduced experimentally (Ball et al., 1981, 1987). Ureaplasmas are common contaminants of the prepuce and the distal urethra, having been isolated from 29-100% of samples cultured where there may be, but not always, inflammation of the prepuce or penis (Pilaszek 1988). Semen is often contaminated by ureaplasmas and may impair sperm function and possibly fertility (Hobson et al., 2013); it also provides an important transmission vector to cows. Embryo transfer fluids have also been found to contain ureaplasmas, which adhere to the zona pellucida often resisting removal by washing (Britton et al., 1988). The spread of genital forms of the disease is facilitated by persistent infections in either the female or male genital tracts.

In a study in the Netherlands, Laak et al. (1992a, b) detected U. diversum in the respiratory tract of 80% of pneumonic calves compared to only 9% of healthy calves, indicating a significant role in the aetiology of respiratory disease. This confirms experimental infections of gnotobiotic calves with ureaplasmas in which pneumonic lesions, though not clinical disease, were seen (Gourlay et al., 1979). The principal reservoir of these infections is the respiratory tract of cattle.

Despite successful experimental reproduction of conjunctivitis in cattle, ureaplasma involvement in natural infections is unclear as known pathogens such as M. bovoculi and Moraxella bovis are often present as well.

The role of ureaplasmas in sheep and goats is less clear; they are readily isolated from the urogenital and, occasionally, respiratory tract of both healthy and diseased animals. Curiously, there have only been reports of isolation from the respiratory tract of small ruminants during rutting (Ross, 1993). A link however has been established between ureaplasmas and urinary calculi in goats on a low calcium diet (Ruhnke, 1994). It appears that ureaplasma infection may influence the total amount and composition of calculi. dos Santos et al. (2013) detected Ureaplasma spp. in sheep semen samples.

Ureaplasma diversum has also been detected in the pneumonic lungs of swine (Burgher et al., 2014).

Impact: Economic

Very little data exists for the effects of ureaplasma infections on livestock but it is clear that infections are under reported because of the difficulties in isolating the organism. However, Ross (1993) states that up to 27% reduction in fertility may occur in some herds which could incur significant economic losses.

Zoonoses and Food Safety

There are no zoonotic or food safety implications of Ureaplasma infection.

Disease Treatment

Little information is available on chemotherapeutic strategies for control of ureaplasma infections. An in vitro study of antibiotic sensitivity to 17 strains of U. diversum in the Netherlands showed the most effective <1m g/ml) to be: chlorotetracycline, tiamulin and tylosin. Antibiotics showing intermediate effectiveness (2-4m g/ml) included oxytetracycline and enrofloxacin. Antibiotics to which ureaplasmas were resistant (>8m g/ml) included: chloramphenicol, spectinomycin and lincomycin (Laak et al., 1993b).

In the field, Ball and McCaughey (1984) successfully eliminated ureaplasmas from the urogenital tract of most, but not all, infected sheep with tiamulin or oxytetracycline. In a study by Rae et al., (1993), pre-breeding treatment with chlortetracycline appeared to improve pregnancy rates in beef heifers with endemic U. diversum infections, though there was only a slight decrease in colonization rates of the vagina by ureaplasmas in treated groups.

There was marked and rapid clinical improvement in 2-year old heifers and bulls with granular vulvitis and ulcerative posthitis following a 5 day intramuscular course of tylosin (Gummow et al., 1992). Ureaplasma could not be cultured from the external genitalia of either heifers or bulls following clinical recovery, which began 3 days after treatment.

Prevention and Control

Treatment of semen with antibiotic combinations of gentamycin, lincospectin and tylosin appears to prevent spread of ureaplasmas and mycoplasmas according to one source (Ruhnke, 1994); however culling of persistently infected bulls may sometimes be necessary (Reid et al., 1989).

The application of three photosensitive agents followed by irradiation for disinfection of bovine semen had no effect on U. diversum at concentrations harmless to sperm (Eaglesome et al., 1994).

Mulira and Saunders (1994) measured antibody levels in serum and cervicovaginal mucus of heifers vaccinated with killed U. diversum strain 2312 in adjuvant; control heifers were given a placebo before both groups were challenged intravaginally. Vaccination stimulated specific IgG1 and IgG2 responses in serum and CVM but only a slight IgM and no IgA response. It was concluded that vaccination stimulated a specific, albeit non-protective, IgG response in serum and CVM. No commercial vaccines are presently available for infections caused by ureaplasmas.

Control of calf pneumonia (including those caused by ureaplasmas) should include measures to reduce environmental stress and to ensure adequate housing with good circulation of air. Wherever possible consideration should be given to ‘all in, all out practices’ to prevent older animals infecting younger ones. If this is not possible separation of calves from the adults is advisable at the earliest possible opportunity where endemic disease exists.

Although survival time of U. diversum in the environment (floors, slurry) does not exceed 24 h, Pilaszek and Truszczynski (1991) showed that it was sufficient to infect preputial mucosa in bulls but not heifers. These workers also showed that asymptomatic carriers can shed U. diversum with urine for prolonged periods. It was concluded that disinfection of cowsheds and treatment of carriers with antibiotics could play an important role in prevention of ureaplasma infection.

No recent studies have investigated veterinary Ureaplasma species antibiotic sensitivities, or their survival in the environment; however studies on Ureaplasma urealyticum have demonstrated that it can form biofilms (Pandelidis et al., 2013), which may have an impact on antibiotic susceptibility, their ability to evade host immune responses and their survival in the environment.

References

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Britton AP; Miller RB; Ruhnke HL; Johnson WH, 1988. The recovery of ureaplasmas from bovine embryos following in vitro exposure and ten washes. Theriogenology, 30(5):997-1003; 20 ref.

Burgher Y; Miranda L; Rodriguez-Roche R; Almeida Campos ACde; Lobo E; Neves T; Martinez O; Timenetsky J, 2014. Ureaplasma diversum in pneumonic lungs of swine. Infection, Genetics and Evolution, 21:486-488.

Cardoso MV, Blanchard A et al. , 2000. Detection of Ureaplasma diversum in cattle using a newly developed PCR-based detection assay. Veterinary Microbiology, 72(3-4):241-250.

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Distribution Maps