Establishment and characterization of a low-dose Mycoplasma haemofelis infection model

Molecular detection and identification of hemotropic Mycoplasma species in dogs and their ectoparasites in Iran

Hemotropic Mycoplasma species are vector-borne bacteria that attach and grow on the surface of erythrocytes in various mammals, yet reports of canine hemoplasmosis in Iran are scarce. The aim of this study was molecular detection and identification of hemoplasmas in the blood of dogs (n = 370) from five provinces of Iran and ectoparasites infesting them including Ctenocephalides canis and Pulex irritans fleas, Rhipicephalus sanguineus sensu lato ticks, Heterodoxus spiniger lice and Hippobosca longipennis keds. Hemotropic Mycoplasma spp. pathogens were detected using genus-specific conventional PCRs, and subsequently identified using species-specific PCRs for Mycoplasma haemocanis (Mhc), and Candidatus Mycoplasma haematoparvum (CMhp). Sanger sequencing was then performed to confirm the species. Correlation of infection and risk factors (geographical area, keeping condition, body condition, sex, age, ectoparasite infestation) were analyzed. In total, 210 dogs (56.7%) were tested PCR-positive for hemotropic Mycoplasma spp. Species-specific PCR and sequencing revealed infection with Mhc in 17.8%, with CMhp in 7.02% and co-infection in 31.9% of dogs. Flea infestation, poor body condition, and being older than 3-years-old correlated with hemoplasmosis. In ectoparasites, DNA of hemoplasmas were detected only in fleas i.e. Mhc in P. irritans, CMhp in P. irritans and C. canis, and co-infection in C. canis. To our knowledge, this is the first large-scale molecular epidemiology study of canine hemoplasmosis in Iran. Considering the high prevalence of canine hemoplasmosis all over the country including potentially zoonotic CMhp, effective ectoparasite control strategies, regular examination of dogs, successful chemoprophylaxis and public awareness strategies are advocated.

Consecutive antibiotic treatment with doxycycline and marbofloxacin clears bacteremia in Mycoplasma haemofelis-infected cats

Mycoplasma haemofelis is the most pathogenic feline hemoplasma species and a causative agent of infectious hemolytic anemia in cats. Current treatment protocols are effective in reducing M. haemofelis blood loads and clinical signs but consistent bacteremia clearance is rarely achieved. The aim of this study was to develop an antibiotic treatment protocol capable of clearing M. haemofelis bacteremia. Doxycycline and marbofloxacin treatment protocols were evaluated in chronically M. haemofelis infected cats in two pre-experiments and a controlled treatment study (main experiment) using five treated and four untreated cats. The blood bacterial loads in the main experiment were monitored weekly by real-time PCR for 203 days. Cats were treated with doxycycline (5 mg/kg bid orally) for 28 days. Cats that remained M. haemofelis PCR-positive or became positive again (all 5 cats in the main experiment) were switched to marbofloxacin treatment (2 mg/kg sid orally) for 14 days; then, all cats were PCR-negative. Immunosuppression after the antibiotic treatment did not lead to reactivation of bacteremia. Fine needle aspirates of different organs and bone marrow collected before and after immunosuppression were PCR-negative. Overall, 5 cats cleared bacteremia with doxycycline alone (showing lower bacterial loads at the treatment start), while 10 cats needed to be switched to marbofloxacin. Based on our results, we recommend doxycycline treatment (10 mg/kg up to 28 days) for clearance of M. haemofelis infection and monitoring bacterial loads by real-time PCR. Only if bacteremia persists or reoccurs, antibiotic treatment should be switched to marbofloxacin (2 mg/kg sid for 14 days).

Acute phase proteins response in cats naturally infected by hemotropic mycoplasmas

Information about the acute phase proteins (APP) response in cats naturally infected with hemoplasmas and in cats co-infected with different species of hemoplasmas is lacking. This study evaluated serum amyloid A (SAA), haptoglobin (Hp) and albumin in 48 cats naturally infected with hemoplasmas, including 25 with Candidatus Mycoplasma haemominutum and 23 co-infected with different hemoplasmas agents; and in 10 healthy control cats. Infected cats had significantly higher Hp and lower albumin than controls. Symptomatic cats had significantly higher SAA and Hp, and lower albumin than asymptomatic animals, and also than controls. Asymptomatic cats had significantly higher Hp than controls. Concentrations of APP were not significantly different between single infected and co-infected cats. According with these results, hemoplasmosis should be considered when alterations in APP are detected in diseased cats with compatible clinical signs. Furthermore, a subclinical infection should be considered in apparently healthy cats from endemic areas with increased Hp.

Passive immunization does not provide protection against experimental infection with Mycoplasma haemofelis

Mycoplasma haemofelis (Mhf) is the most pathogenic feline hemotropic mycoplasma. Cats infected with Mhf that clear bacteremia are protected from Mhf reinfection, but the mechanisms of protective immunity are unresolved. In the present study we investigated whether the passive transfer of antibodies from Mhf-recovered cats to naïve recipient cats provided protection against bacteremia and clinical disease following homologous challenge with Mhf; moreover, we characterized the immune response in the recipient cats. Ten specified pathogen-free (SPF) cats were transfused with pooled plasma from cats that had cleared Mhf bacteremia; five control cats received plasma from naïve SPF cats. After homologous challenge with Mhf, cats were monitored for 100 days using quantitative PCR, hematology, blood biochemistry, Coombs testing, flow cytometry, DnaK ELISA, and red blood cell (RBC) osmotic fragility (OF) measurement. Passively immunized cats were not protected against Mhf infection but, compared to control cats, showed significantly higher RBC OF and B lymphocyte (CD45R/B220⁺) counts and occasionally higher lymphocyte, monocyte and activated CD4⁺ T lymphocyte (CD4⁺CD25⁺) counts; they also showed higher bilirubin, total protein and globulin levels compared to those of control cats. At times of peak bacteremia, a decrease in eosinophils and lymphocytes, as well as subsets thereof (B lymphocytes and CD5⁺, CD4⁺ and CD8⁺ T lymphocytes), and an increase in monocytes were particularly significant in the passively immunized cats. In conclusion, passive immunization does not prevent bacteremia and clinical disease following homologous challenge with Mhf, but enhances RBC osmotic fragility and induces a pronounced immune response.

Lack of cross-protection against Mycoplasma haemofelis infection and signs of enhancement in "Candidatus Mycoplasma turicensis"-recovered cats

“Mycoplasma haemofelis” and “Candidatus Mycoplasma turicensis” are feline hemoplasmas that induce hemolytic anemia. Protection from homologous re-challenge was recently demonstrated in cats recovered from primary infection. Here, we determined if cats recovered from “Cand. M. turicensis” infection were protected against infections with the more pathogenic M. haemofelis. Ten specified pathogen-free cats were exposed to M. haemofelis. Five of the ten cats had recovered from “Cand. M. turicensis” bacteremia (group A), and five cats were naïve controls (group B). No cross-protection was observed. By contrast, the “Cand. M. turicensis”-recovered cats displayed faster M. haemofelis infection onset (earlier PCR-positive and anemic) than the controls. No “Cand. M. turicensis” was detected in any cat. M. haemofelis shedding was observed in saliva, feces and urine. In both groups, evidence of a Th1 response was observed (high IFN-γ, low IL-4), but IL-10 levels were also high. In group A, total, CD4+ and CD8+ T cells increased within days after M. haemofelis exposure. At times of maximal bacteremia, macrocytic hypochromic anemia, neutropenia, monocytosis and a decrease in leukocyte, eosinophil, and lymphocyte counts and subsets thereof (B- and T-cells, CD4+, CD8+ and CD4+CD25+ cells) were particularly significant in group A. Moreover, an increase in protein concentrations, hypoalbuminemia and a polyclonal hypergammaglobulinemia were observed. Five of ten M. haemofelis-infected cats subsequently cleared bacteremia without antibiotic treatment. In conclusion, the study suggests that a previous hemoplasma infection, even when the cat has ostensibly recovered, may influence subsequent infections, lead to an enhancement phenomenon and other differences in infection kinetics.

Molecular detection of haemotropic Mycoplasma species in urban and rural cats from Portugal

OBJECTIVES

The aim of the present study was to evaluate the prevalence of haemoplasma infection in cats in Portugal and to assess risk factors for infection.

METHODS

Real-time polymerase chain reaction techniques were used to assess 236 urban and rural cats from central and southern Portugal.

RESULTS

The overall prevalence of haemoplasma in the target population was 27.1% (64/236), with individual species' prevalences as follows: 17.8% (42/236) 'Candidatus Mycoplasma haemominutum' (CMhm), 14.4% (34/236) Mycoplasma haemofelis (Mhf) and only 5.9% (14/236) 'Candidatus Mycoplasma turicensis' (CMt). Multiple infections were detected in 8.1% (19/236) of the samples, with triple and double infections with Mhf and CMhm being most commonly detected (5.9% [14/236] of cats). Haemoplasma infection was significantly higher in shelter cats (P = 0.015) than in cats with other lifestyles (eg, free-roaming/house pet/blood donors). Haemoplasma prevalence was also higher in cats with feline immunodeficiency virus infection (FIV; P = 0.011). Although sex was not significantly associated with haemoplasma infection (P = 0.050), CMt was predominantly found in males (P = 0.032). Also, the presence of haemoplasma multiple infections was statistically associated with being in a shelter (P = 0.021), male (P = 0.057) and with FIV co-infection (P = 0.004). No evidence of an association between haemoplasma infection and geographical location, age or feline leukaemia virus co-infection was found.

CONCLUSIONS AND RELEVANCE

The results obtained in our study are consistent with the documented worldwide prevalence of feline haemoplasma infections, suggesting that the three main feline haemoplasma species are common in Portugal.

Protective immunity against infection with Mycoplasma haemofelis

Hemoplasmas are potentially zoonotic mycoplasmal pathogens, which are not consistently cleared by antibiotic therapy. Mycoplasma haemofelis is the most pathogenic feline hemoplasma species. The aim of this study was to determine how cats previously infected with M. haemofelis that had recovered reacted when rechallenged with M. haemofelis and to characterize the immune response following de novoM. haemofelis infection and rechallenge. Five specific-pathogen-free (SPF)-derived naive cats (group A) and five cats that had recovered from M. haemofelis infection (group B) were inoculated subcutaneously with M. haemofelis. Blood M. haemofelis loads were measured by quantitative PCR (qPCR), antibody response to heat shock protein 70 (DnaK) by enzyme-linked immunosorbent assay (ELISA), blood lymphocyte cell subtypes by flow cytometry, and cytokine mRNA levels by quantitative reverse transcriptase PCR. Group A cats all became infected with high bacterial loads and seroconverted, while group B cats were protected from reinfection, thus providing the unique opportunity to study the immunological parameters associated with this protective immune response against M. haemofelis. First, a strong humoral response to DnaK was only observed in group A, demonstrating that an antibody response to DnaK is not important for protective immunity. Second, proinflammatory cytokine interleukin-6 (IL-6) mRNA levels appeared to increase rapidly postinoculation in group B, indicating a possible role in protective immunity. Third, an increase in IL-12p35 and -p40 mRNA and decrease in the Th2/Th1 ratio observed in group A suggest that a Th1-type response is important in primary infection. This is the first study to demonstrate protective immunity against M. haemofelis reinfection, and it provides important information for potential future hemoplasma vaccine design.