Prevalence of swine hemoplasmas revealed by real-time PCR using 16S rRNA gene primers

Hemotrophic Mycoplasmas-Vector Transmission in Livestock

Hemotrophic mycoplasmas (HMs) are highly host-adapted and specialized pathogens infecting a wide range of mammals including farm animals, i.e., pigs, cattle, sheep, and goats. Although HMs have been known for over 90 years, we still do not know much about the natural transmission routes within herds. Recently, it has been repeatedly discussed in publications that arthropod vectors may play a role in the transmission of HMs from animal to animal. This is mainly since several HM species could be detected in different potential arthropod vectors by PCR. This review summarizes the available literature about the transmission of bovine, porcine, ovine, and caprine HM species by different hematophagous arthropod vectors. Since most studies are only based on the detection of HMs in potential vectors, there are rare data about the actual vector competence of arthropods. Furthermore, there is a need for additional studies to investigate, whether there are biological vectors in which HMs can multiply and be delivered to new hosts.

Haemotrophic Mycoplasmas Infecting Pigs: A Review of the Current Knowledge

Haemotrophic mycoplasmas (haemoplasmas) are a group of highly specific and adapted bacteria. Three different haemoplasma species in pigs are known to date: Mycoplasma (M.) suis, M. parvum and 'Candidatus (Ca.) M. haemosuis'. Even though these bacteria have been known in pig farming for a long time, it is difficult to draw general conclusions about the relevance of their infections in pigs. This review summarizes the current knowledge on the three porcine haemoplasma species with regards to clinical and pathological descriptions, pathobiology, epidemiology and diagnostics as well as prevention and therapy. Overall, it is clear that considerably more data are available for M. suis than for the other two species, but generally, porcine haemoplasmas were found to be highly prevalent all over the world. Mycoplasma suis is the most virulent species, causing acute infectious anaemia in pigs (IAP), whereas M. parvum usually results in chronic and subclinical infections associated with performance losses. Little is known about the clinical significance of the recently discovered third porcine species 'Ca. M. haemosuis'. So far, the described pathogenic mechanisms mainly include direct destruction of erythrocytes via adhesion, invasion, eryptosis and nutrient scavenging, indirect erythrocyte lysis due to immune-mediated events and immune dysregulation processes. A review of published diagnostic data confirms PCR assays as the current standard method, with various cross-species and species-specific protocols. Overall, there is a need for further examination to obtain valuable insights for practical application, specifically regarding the importance of subclinical infections in naturally infected animals. An essential requirement for this will be to gain a more comprehensive understanding of the mechanisms operating between the host and the pathogen.

Occurrence of Mycoplasma parvum in German Pigs of Different Age Groups Using a Novel Quantitative Real-Time PCR Assay

Mycoplasma (M.) parvum is a hemotrophic bacterium circulating in the blood of pigs but is not considered a primary pathogen. Only a handful of studies dealing with this agent have been published since its first description in 1951, and many issues, including epidemiology and the impact of subclinical infections, are yet to be elucidated. This study aimed to establish a M. parvum specific real-time PCR for its detection and quantification in porcine blood and the application of this assay to obtain insights into the occurrence of M. parvum in German pigs. Furthermore, 16S rDNA amplicons of M. parvum positive blood samples were phylogenetically analyzed using MEGA 11 software. The established qPCR targeting the M. parvum glyceraldehyde-3-phosphate dehydrogenase encoding gene (gap) showed a lower detection limit of 10 gene copies per reaction and no cross-reactivity within the specificity test. A total of 36.0% (n = 72) of the sampled fattening pigs, 25.0% (n = 15) of the sows, and 4.37% (n = 8) of the boars tested M. parvum positive. The dendrogram showed the typical allocation of the M. parvum isolates into the "haemominutum group" subgroup within the hemotrophic Mycoplasma species. Both the novel established qPCR and the obtained epidemiological data can serve as an important basis for future studies dealing with M. parvum.

Occurrence of 'Candidatus Mycoplasma haemosuis' in fattening pigs, sows and piglets in Germany using a novel gap-based quantitative real-time PCR assay

Background

The appearance of the novel porcine haemotrophic mycoplasma (HM) species ‘Candidatus Mycoplasma haemosuis’ was reported in apparently healthy but also in clinically sick animals in China, Korea and in a case report from Germany. Outside of Asia, however, nothing further is known about the frequency of ‘Ca. M. haemosuis’ in pigs to date. To investigate the distribution of this novel HM species in Germany, fattening pigs, sows and pre-suckling piglets were examined using a herein developed quantitative real-time PCR assay (qPCR). Because the piglets were sampled before the first colostrum uptake, additional information on a possible vertical transmission from dams to their offspring was obtained.

Results

Our novel qPCR assay successfully detected ‘Ca. M. haemosuis’ in all blood samples from the ‘Ca. M. haemosuis’-infected pigs. No cross-reactivity was detected when DNA from non-target Mycoplasma spp. and other bacterial species representing 10⁵ bacteria/reaction were used as a template. The lower limit of detection of the qPCR was thus 10 gap gene copies per reaction and 2.5 x 10³ genome equivalents (GE) per mL blood.

‘Candidatus M. haemosuis’ was detected by this qPCR in blood samples from a total out of 6.25% sows (13/208), 4.50% pre-suckling piglets (28/622) and 17.50% fattening pigs (35/200). On farm level, 3 out of 21 piglet producing farms (14.28%) and 9 out of 20 fattening farms (45.00%) were positive for ‘Ca. M. haemosuis’. Co-infections with M. suis were evident in all age groups.

Conclusion

‘Candidatus M. haemosuis’ infection is present in German pig farms and the detection of the novel porcine HM species in piglets immediately after birth before colostrum intake indicates vertical transmission. The novel qPCR assay specific for ‘Ca. M. haemosuis’ described herein will be a prerequisite for future studies on the prevalence, epidemiology as well as the clinical and economic impact of ‘Ca. M. haemosuis’ infections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03147-1.

Porcine hemothropic mycoplasmas infection associated with productive impact in intensive pig production

Background

So far, three porcine hemoplasmas (PH) have been identified, namely Mycoplasma suis, Mycoplasma parvum, and Mycoplasma haemosuis. The first one is the main agent associated with porcine hemoplasmosis, a possible cause of economic losses in pig production. Thus, this work aimed to detect and quantify PH 16S rRNA in finishing pigs and to associate its load estimate with average daily weight gain (ADWG). For this purpose, whole blood samples from 318 pigs were collected at an age of 75 days (d0) when the pigs entered the finishing phase and 105 days later (d105). To calculate ADWG, the animals were weighed at the abovementioned dates. Then, DNA from blood samples were submitted to a qPCR targeting the 16S rRNA gene for PH. Spearman correlation test was performed to investigate potential associations between ADWG and the quantification values. Lastly, the molecular characterization of PH was done by sequencing the 23S rDNA gene.

Results

Out of the 318 samples, 190 (59.74%) were positive on d0, and 304 (95.6%) were positive on d105. A significant correlation was observed (p < 0.05), albeit with a low coefficient value (0.18), when comparing ADWG with quantification values on d105. The phylogenetic analysis based on the 23S rDNA gene showed that four sequences were closely related to M. parvum, and one sequence was positioned in the M. suis cluster.

Conclusion

Two PH, M. suis and M. parvum, were detected in a Brazilian pig farm. Moreover, increasing occurrence through time was observed, which may have affected the productive performance of positive animals, mainly at the end of the finishing phase, when antimicrobials are removed.

Supplementary information

The online version contains supplementary material available at 10.1186/s40813-020-00171-1.

Genetic diversity of emerging hemotropic mycoplasmas in domestic pigs from Brazil

Mycoplasma suis and Mycoplasma parvum bind strongly to erythrocytes and may cause clinical hemoplasmosis in swine, affecting several age groups. Mycoplasma spp. infected animals may be asymptomatic carriers and/or show nonspecific clinical signs. In Brazil, information on genetic diversity associated with porcine hemoplasmas (PH) has not been described yet. Therefore, this study has aimed to detect, quantify and characterize the genetic diversity of PH in finishing pigs from technified farms in the state of Goiás, central-western Brazil. Ethylenediaminetetraacetic acid-blood samples from 450 swine belonging to 30 different farms from Goiás state were collected at the slaughterhouse. Quantitative real-time PCR (qPCR) assays were performed for the molecular detection and quantification of PH 16S rRNA gene fragments. Cloning and sequencing of 16S and 23S rRNA amplicons were performed to evaluate the genetic diversity. Moreover, a questionnaire was applied to each farm manager to obtain epidemiological information about the herd. The results on qPCR showed herd occurrence of 68.89% for PH. Quantification values (starting quantity [SQ]) ranged from 8.43 × 10^-1 to 4.69 × 10⁶ copies/µl, and 52.71% of the samples presented SQ values equal or lower than 1 × 10³ copies/µl. Risk factors were not evaluated once all farms had at least one positive animal. However, Spearman's coefficient test revealed that the occurrence of PH was inversely associated with the number of farrows per week, weaned piglets per week, and weight at slaughter. Phylogenetic analysis based on maximum likelihood and Bayesian methods showed that the 16S rRNA and 23S rRNA gene sequences obtained from five samples formed a single cluster closely related to M. parvum. Genotype analysis using DNASP software confirmed seven and four different 16S and 23S rRNA genotypes among the cloned amplicons, indicating that there are several genotypes of M. parvum circulating in individual pigs and among pig farms in central-western Brazil.

Prevalence and phylogenetic analysis of hemoplasma species in domestic pigs in Korea

Background

Two hemoplasma species, Mycoplasma suis and M. parvum, previously known as Eperythrozoon suis and E. parvum, respectively, have been identified in pigs. Swine hemoplasmosis is a global problem, and M. suis infection results in economic losses to pig producers worldwide. This study investigated the frequency and distribution of hemotropic mycoplasmas in pig farms of Korea. As hemoplasmas can be transmitted by ticks, we also analyzed the presence of the tick-borne pathogens Anaplasma spp. and Borrelia spp.

Methods

We screened 1867 samples from 464 pig farms located in four regions of Korea over the period from 2014 to 2018. PCR-positive samples were further analyzed by nucleotide sequencing and phylogenetic analysis of pathogen-specific markers for species identification.

Results

Of the 1867 pigs evaluated in the study, three (0.2%), 51 (2.7%), and one (0.1%) were found to be infected with M. suis, M. parvum, and the novel hemotropic M. haemosuis, respectively; Anaplasma spp. and Borrelia spp. were not detected. The 16S rRNA sequences of M. suis, M. parvum, and the novel hemotropic M. haemosuis were highly similar (99.3–100%, 99.6–100%, and 99.6–100%, respectively) to those of Mycoplasma spp. isolated from other countries. To the best of our knowledge, this is the first nationwide, large-scale study of the molecular detection of Mycoplasma spp. in domestic pigs in Korea.

Conclusions

Our results indicate that Mycoplasma infections are widespread in Korean domestic pigs, and that continuous monitoring and control strategies are required to prevent the spread of hemoplasmas, which, in addition to causing economic losses in the pig industry, pose a potential threat to public health. As transmission routes of hemoplasmas remain unelucidated, additional epidemiological studies are recommended to identify reservoirs and vectors of Mycoplasma spp. in Korea.

High frequency and molecular characterization of porcine hemotrophic mycoplasmas in Brazil

Mycoplasma suis and Mycoplasma parvum are the two hemotrophic mycoplasmas species described in pigs. M. suis is involved in infectious anemia, while M parvum infection is commonly subclinical. The objectives of this study were twofold: (i) to investigate the prevalence of porcine hemotrophic mycoplasmas in sows from the southern region of Brazil by quantitative real-time PCR (qPCR) and (ii) to genetically characterize a subset of the samples based on the 16S rRNA gene. A total of 429 blood samples were evaluated from 53 different farm sites. Porcine hemoplasmas was detected at all the 53 tested sites and in 79.72% of the samples (342/429). Two sequences were obtained for Mycoplasma spp. The phylogenetic analysis based on the 16S rRNA gene (900 bp) showed that the Mycoplasma sequences were closely related to the M. suis cluster and that one sequence was positioned in the M. parvum cluster. In conclusion, porcine hemoplasmas have a high rate of prevalence in sows from commercial farms in the southern region of Brazil. This study demonstrated the first molecular detection and characterization of partial 16S rRNA gene of M. parvum in Brazil.

Molecular detection of Mycoplasma suis in captive white-lipped peccaries (Tayassu pecari) and wild boars (Sus scrofa) in Brazil

Mycoplasma suis, the etiological agent of swine hemoplasmosis, is an epicellular bacterium that adheres to the surface of pig erythrocytes leading to deformations of the target cells. Little is known about the occurrence of M. suis in wild swine populations around the world, its economic impact on swine herds, and the risk of human infection. The aim of this study was to investigate, by quantitative real-time PCR (qPCR) based on the 16S rRNA gene, the occurrence of M. suis in a captive population of white-lipped peccaries (100 Tayassu pecari) and in free-living wild boars (14 Sus scrofa) in Brazil. None of the white-lipped peccaries were positive for M. suis, whereas seven (50%) wild boars were positive in qPCR assays. The quantification of M. suis-16S rRNA copies/μL ranged from 1.42 × 10° to 3.906 × 10¹ in positive animals, indicating a low bacteremia and a chronic carrier status in free-living wild boars. In conclusion, M. suis might be a non-frequent pathogen in wild suids maintained in captivity. Despite the low bacteremia, the prevalence of M. suis in wild boar population in Brazil seems to be high.

Rapid detection of haemotropic mycoplasma infection of feline erythrocytes using a novel flow cytometric approach

Background

The haemotropic mycoplasmas Mycoplasma haemofelis and Candidatus Mycoplasma haemominutum cause feline infectious anaemia with infection rates in feline populations reflecting widespread subclinical infection. Clinically significant infections are much rarer but can be life-threatening. Current diagnosis is dependent upon visualising organisms in stained blood smears, PCR or quantitative PCR (qPCR). These procedures are labour-intensive and time-consuming. Furthermore, PCR-based approaches offer limited insight into the disease burden of the infected animal.

Methods

We have developed a novel and rapid flow cytometric system that permits diagnosis of haemotropic mycoplasma infections and quantitation of the percentage of erythrocytes that are parasitized. The method exploits the fact that mature mammalian erythrocytes, the host cell for haemoplasmas, are enucleated and thus lack nucleic acid. DRAQ5 is a synthetic anthrocycline dye which rapidly crosses cell membranes and binds to nucleic acids. The presence of exogenous bacterial DNA in mammalian erythrocytes can, therefore, be detected by DRAQ5 uptake and flow cytometric detection of DRAQ5 fluorescence.

Results

Here, we show that this system can detect epi-erythrocytic infection of companion felines by haemotropic mycoplasma. Due to their differences in size, and hence the quantity of DNA, the two major feline hemoplasmas M. haemofelis and Candidatus M. haemominutum can be distinguished according to DRAQ5 fluorescence. We have also shown the usefulness of DRAQ5 uptake in monitoring a cat infected with M. haemofelis sequentially during treatment with doxycycline.

Conclusions

The technique described is the first report of a flow cytometric method for detecting haemotropic mycoplasmas in any species and could be applied to widespread screening of animal populations to assess infection by these epi-erythrocytic parasites.