It is important to note that poultry production is a viable and ever-growing business among other agricultural-related businesses in South Africa, as it accounts for the majority of protein sources (Idowu et al., 2019). Recently, there have been cases of reduced egg quality and decreased egg production, which are all symptoms related to MG and MS (Puvača et al., 2020; Yadav et al., 2022; Feberwee et al., 2022). The objective of the present study was to molecularly detect Mycoplasma synoviae (MS) and Mycoplasma gallisepticum (MG) in South African chicken breeds. Fecal and swab samples were used for the detection of MG and MS, and the results are shown in Table 1.
This study revealed the highest prevalence of MG in swab samples from Ovambo breeds and the lowest in those from Rhode Island. Previous research has shown high levels of MG and MS across farms (Mahmmoud et al., 2022; Marouf et al.,2022). Surprisingly, PKs did not contain MGs or MSs across the sampled faecal or tracheal swabs. This could be because of the strict biosecurity measures adopted in the PK breed pen and the host immune response to MG and MS, which leads to high resistance to MG and MS (Ishfaq et al., 2020).
In contrast to the study by Felice et al. (2020) on a chicken backyard farming system in Italy, the present study recorded a relatively lower prevalence of MG and MS. This may be due to the better biosecurity of commercial poultry production, the differences in sampling time and the variation in season (Mahmmoud et al., 2022). Khalifa et al. (2013) reported that MG and MS can easily be transmitted across poultry pens, which supports the current finding that MG and MS are present in both tracheal swabs and fecal samples. This may suggest that there is horizontal transmission of mycoplasma within poultry chickens.
Phylogenetic analysis of MG 16S rRNA sequences revealed a high percentage of nucleotide similarity with corresponding sequences of MG strains from four isolates from different countries, namely, Brazil, India, Pakistan, and the USA. This may imply the possibility of an evolutionary relationship among all the isolates. However, there were two observed strains in this study, namely, PT/MG71/ck/00 (99%) and PT/MG41/ck/00 (98%), which had high similarity to those in Brazil, but only with accession number OR104959. This finding showed a high level of similarity between these two isolates. Additionally, PT/MG48/ck/00 and PT/MG51/ck/00 from this study have high levels of similarity with those from a study from India, with accession number ON955841. Furthermore, the current study showed a high level of evolutionary relationship with similar studies in Hungary, Poland, Thailand, Japan, and Egypt (Sulyok et al., 2019; Felice et al., 2020). Additionally, IT/MG41/ck/00, IT/MG48/ck/00, and IT/MG51/ck/00 formed a separate cluster from all the other analysed MG strains, indicating a high degree of similarity (99.6%) (Fig. 3). However, IT/MG71/ck/00 was not closely related to the other three strains in this study. This could suggest the presence of a new strain from among the other strains detected in South Africa chicken production.
The PT/MS41/CK/01 strain shares 84% similarity with the KC832812 Israeli strain of MS. Additionally, there was a cluster of PT/MS74/CK/01 strains with Japanese MS strains with 74% similarity. Finally, there was a cluster between PT/MS78/CK/01 and the MS strain Thailand, with reference number ON191527 (Fig. 4). The two strains are closely related, showing a high level of similarity from common ancestors. Nevertheless, PT/MS46/CK/01 underwent speciation from two of the above strains (ON191527 and PT/MS78/CK/01), which were from the same ancestor but not closely related. The dendrogram obtained from this study revealed that the MS strains belonged to four different subclusters (Fig. 4). PT/MS41/ck/00 and PT/MSA22/ck/00 clustered with the KC832812 (Israel) strain at 84% and 81%, respectively. The South African strains exhibited a strong evolutionary trend compared with the Israeli strains. Additionally, the ON191527 (Thailand) strain has a strong evolutionary relationship with two South African strains from this study, PT/MS78/ck/00 and PT/MS46/ck/00, with 79% and 78%, respectively, similarity. Interestingly, PT/MS74/ck/00 is evolutionarily distant from the other four strains observed in this study (Fig. 4). This strain could be genetically diversified from the other three strains reported in this study. A dendrogram of the vlha sequences of the MS strains detected in the PT/MSA22/CK/01 study clustered with Israel KC832812 and Hungary KC506807, with percentage similarities of 99 and 98%, respectively (Fig. 4).
Despite all attempts to produce mycoplasma-free poultry in South Africa poultry production, the prevalence of MG and MS across poultry houses corroborates that MG and MS can be transmitted horizontally through the possible inhalation of contaminated droplets of air in feed (Valeris-Chacin et al., 2021). Additionally, the types of samples (tracheal swabs and feces) used for detection in this study were obtained from previous studies (Sawicka-Durkalec et al., 2021; Jude 2021), which makes it difficult to completely eradicate them. Furthermore, MG and MS can be more easily detected from swab samples than from faecal samples due to the possibility of higher sensitivity of tracheal swabs to qPCR than faecal samples (Jude, 2021). Additionally, air easily contributes to the transmission of bacterial pathogens to the tracheal region faster than to the lower part of the body (Valeris-Chacin et al., 2021). Therefore, conscious efforts should be made to ensure adherence to biosecurity measures, select breeds with high immune responses, use essential oils (Puvača et al., 2020), use herbal extracts (Rehman et al., 2019), use phytogenic products (Upadhaya and Kim 2017), use prebiotics and antibiotics (Amer et al., 2017), use probiotics (Wang et al., 2021), use synbiotics (Limsatanun et al.,2018), use biologically sensitized nanoparticles (Guha et al., 2021) and possibly use chickens with high levels of mannose-binding lectin (Idowu et al., 2021).