Occurrence and identification of hemotropic mycoplasmas (Hemoplasmas) in free ranging and laboratory rats (Rattus norvegicus) from two Brazilian zoos

BACKGROUND: Hemotropic mycoplasmas (hemoplasmas), bacteria belonging to the class Mollicutes, are obligatory red blood cell pathogens of a variety of animal species. They may cause acute anemia that is life-threatening or chronic disease that is clinically silent, but may interfere with results of experimental studies when using infected animals. Since these bacteria cannot be cultivated, molecular techniques are the gold standard for diagnosing an infection, investigating its prevalence, and describing new species. Mycoplasma coccoides and M. haemomuris are the most commonly recognized hemoplasmas in the blood of wild and laboratory rodents. Neither the epidemiology nor clinical and molecular characterization of hemoplasma infection in free-ranging rodents in Brazil has been previously reported. The aims of this study were to investigate the occurrence of hemoplasmas in free-ranging rats (Rattus norvegicus) captured in the Passeio Público and Curitiba Zoo and compare hematologic parameters of infected and non-infected animals. RESULTS: Anti-coagulated blood samples collected from 43 free-ranging and 20 nursery rats were included in the study. Overall 63.5 % were positive using SYBR® Green quantitative PCR (qPCR) of the 16S rRNA gene to screen for hemoplasma infection (72 % among free-ranging rats; 45 % among laboratory-raised rats). Sequencing of the qPCR products showed that all but one sample had >98 % identity to M. haemomuris. Phylogenetic analysis based on a fragment of approximately 1300 bp of the 16S rRNA gene showed 99 % identity to a new hemoplasma from European rats and 98 % identity to a hemotropic mycoplasma described infecting a European harvest mouse (Micromys minutus). No statistically significant changes in hematologic parameters between infected and non-infected rats were found, confirming the low pathogenicity and/or silent characteristics of the infection. CONCLUSIONS: Our findings suggest that hemoplasmas are likely endemic in rodent species in this region. The epidemiology, especially as it relates to the mode of transmission, needs to be further investigated as well as the possibility that other animal species, including humans, might become infected.