Candidatus Mycoplasma haemominutum-associated anaemia in cats: a small clinical study with a single FeLV-positive cat
Irish veterinary journal · 2026
In plain language
This study describes 38 cats infected with a blood bacterium called Candidatus Mycoplasma haemominutum (CMhm). Thirteen had anaemia and 25 did not. Every anaemic cat also had another illness, so the anaemia cannot be blamed on this bacterium alone. Only one cat in the study was FeLV-positive, so the study cannot tell us anything about FeLV.
Scientific detail
This is a cross-sectional clinical study of naturally infected cats with CMhm confirmed by conventional PCR: 38 animals, 13 anaemic and 25 non-anaemic. Ten CMhm 16S rRNA sequences were also generated. The cross-sectional design cannot establish causality or temporal sequence. Conventional PCR did not quantify bacterial load.
All anaemic cats had at least one concurrent disease, as did most non-anaemic cats, and the difference was not significant. This is compatible with a secondary-pathogen role for CMhm but does not exclude a primary role; undetected conditions or a limited screening panel could also explain it. At the population level, the anaemia was mild, normocytic-normochromic and non-regenerative. These are descriptive findings from 13 anaemic cats, all with comorbidities, and cannot be attributed to CMhm alone.
Only one cat in the cohort was FeLV-positive. It was CMhm co-infected and anaemic, with macrocytic non-regenerative anaemia and thrombocytopenia, and it died after a progressive course. The authors suspect myelodysplastic syndrome, but this was not confirmed, as no bone marrow examination or histopathology was done. The FeLV association was not statistically significant (1/13 vs 0/25). The authors suggest a possible contributory role of FeLV, reasoning from the low background FeLV prevalence (10/290); with n = 1 this reasoning is speculative and supports no conclusion about FeLV.
Limitations include the small sample size, the absence of reticulocyte counts and iron profiles in the non-anaemic group, and the lack of comprehensive evaluation of direct biomarkers of haemolysis, inflammation and iron regulation. The conserved 16S rRNA gene limits investigation of virulence determinants. The proposed mechanisms are plausible interpretations, not definitive conclusions.
What we know
In this cohort of 38 CMhm-infected cats, every anaemic cat had at least one concurrent disease, and the anaemia was overall mild, normocytic-normochromic and non-regenerative. For FeLV, there is only a single-case observation: one co-infected, anaemic cat with macrocytic non-regenerative anaemia and thrombocytopenia, which died. The study does not show that FeLV contributes to CMhm-associated anaemia.
What we don't know
Whether CMhm can act as a primary pathogen, independent of concurrent disease, remains unresolved. Whether FeLV influences CMhm-associated anaemia is unknown; one cat cannot support a conclusion. The suspected myelodysplastic syndrome in that cat was not confirmed. The mechanisms of the anaemia remain unestablished.
Evidence
EvidenceLevel C — Preliminary evidenceConfidence 90/100
All anaemic CMhm-infected cats had at least one concurrent disease, as did most non-anaemic cats, and the difference was not significant.
Excerpt verified in the source — verbatim, in the source's own language“All CMhm-infected anaemic cats (13/13, 100%) and most non-anaemic cats (22/25, 88%) had at least one concurrent disease ( P = 0.53).”
This is compatible with a secondary-pathogen role for CMhm but does not exclude a primary role. Undetected conditions or the limited screening panel could also explain the finding.
EvidenceLevel C — Preliminary evidenceConfidence 85/100
At the population level, the anaemia in these cats was mild, normocytic-normochromic and non-regenerative.
Excerpt verified in the source — verbatim, in the source's own language“CMhm-associated anaemia was generally mild (mean PCV 22%, median Hgb 8.2 g/dL), normocytic–normochromic (median MCV 39.2 fL, MCHC 31.7 g/dL), and non-regenerative (median reticulocytes 0.045 × 10⁶/µL).”
Descriptive findings from 13 anaemic cats, all with comorbidities. They cannot be attributed to CMhm alone.
InferenceConfidence 60/100
The single FeLV-positive cat falling in the anaemic group may suggest a contributory role of FeLV, according to the authors. The FeLV association itself was not statistically significant (1/13 vs 0/25).
With n = 1 this cannot support any conclusion about FeLV. The authors' reasoning rests on the low background FeLV prevalence (10/290) and is speculative.
Open questionConfidence 85/100
Whether CMhm can act as a primary pathogen, independent of concurrent disease, remains unresolved.
The background states that inconsistent prior reports leave the question unresolved. This study's finding that all anaemic cats had comorbidities does not settle it.
Provenance
Source: Clinical insights into Candidatus Mycoplasma haemominutum-associated anaemia in naturally infected cats: flea-associated risk and paradoxical clinicopathological findings.
AVA