Importance of canine hemotropic mycoplasma infections with emphasis on their geographical distribution

Importance of canine hemotropic mycoplasma infections with emphasis on their geographical distribution Abstract Two hemotropic mycoplasmas (aka hemoplasma) species have been characterized in dogs: Mycoplasma haemocanis (Mhc) and ‘Candidatus Mycoplasma haematoparvum’ (CMhp). The natural transmission routes of canine hemoplasmas are as yet poorly understood. Previous studies have suggested an association between the prevalence of canine hemoplasma infections and the presence of the potential tick vector, Riphicephalus sanguineus, which is commonly encountered in areas with Mediterranean climate. The aim of the present study was to assess the prevalence and clinical importance of canine hemoplasmas in countries with Mediterranean climate and molecularly characterize the identified isolates. Using real-time TaqMan® PCR, 82 out of the 850 investigated samples (600 Italian, 200 Spanish, 50 Portuguese) were PCR-positive (9.6%; 95% CI 7.7-11.8); of these, 43 (5.1% CI 3.7-6.8) were positive for Mhc and 34 (4%; 95% CI 2.8-5.5) were positive for CMhp. Five Italian dogs were co-infected with both canine hemoplasmas. The sample prevalence was significantly higher in Portugal (40%) than in Italy (9.5%; P<0.0001), which in turn had a significantly higher prevalence than Spain (2.5%; P=0.0009). Moreover, the hemoplasma prevalence in Italy and Portugal was significantly higher than what we had previously reported for Switzerland (P<0.0001), a country where R. sanguineus is not permanently established. Canine hemoplasma infections were significantly more frequent in kennel dogs than in privately owned dogs (P=0.0117). Heavy tick infestations associated to mutual conditions of the dogs in the kennel could explain the higher prevalence of canine hemoplasma infections. In addition, dogs infected by blood-sucking arthropods showed more often canine hemoplasma infection (P=0.0035). Overall, no significant difference was found in the infection rate between sick and healthy dogs; however, in the samples from Bologna the hemoplasma prevalence was significantly higher in sick than healthy dogs (P<0.0179). Ten of the 82 PCR-positive dogs (12.2%) were anemic (PCV<37%); two dogs had a PCV of 17.4% and <10%, respectively; but overall no significant association was found between anemia and the presence of hemoplasma infections. Sequencing of the 16S rRNA gene of different isolates derived from Italy, Spain and Portugal revealed >99% identity to other European isolates. In conclusion, the present study demonstrated that canine hemoplasma infections are commonly encountered in Mediterranean countries and in kennel dogs. This supports our hypothesis that the prevalence of hemoplasma infections is associated with the presence of the R. sanguineus tick vector. The clinical importance of canine hemoplasma infections is unclear; only some dogs exhibited clinical signs attributable to canine hemoplasmosis (e.g. severe anemia). The stage of hemoplasma infection in the presented dogs was unknown: chronically infected dogs that recovered from acute illness may lack clinical signs. Moreover, additional factors, such as immunosuppression, may play a role in the pathogenesis.