When to see a vet urgently
Seek immediate care if your cat has any of the following:
- Very pale mucous membranes with weakness or an inability to get up.
- Rapid, laboured or open-mouth breathing at rest.
- Collapse or reduced responsiveness to its surroundings.
- Fever or yellowing accompanied by loss of appetite and marked deterioration.
Severe anaemia can compromise oxygen transport even without visible bleeding. You can find a vet near you.
Overview
Mycoplasma haemofelis belongs to the haemotropic mycoplasmas: microbes that attach to the surface of red blood cells and destroy them. Red blood cell breakdown (haemolysis) leads to anaemia. The disease may be acute, chronic or latent. Some infected cats remain symptom-free while the body keeps the infection under control, but stress or weakened immunity can allow illness to reappear.
Other haemoplasma species are also recognised in cats, including Candidatus Mycoplasma haemominutum and Candidatus Mycoplasma turicensis. Their ability to cause disease varies, and Mycoplasma haemofelis is usually the most important cause of severe anaemia. It can also make a cat ill without a previously diagnosed immune problem.
The cat's own defence system also contributes to red blood cell loss by removing altered cells from circulation. The marrow may try to replace them by increasing production, but haemolysis can outpace this response. This microbe is different from the mycoplasmas associated with common respiratory signs; the name alone does not identify the site of infection.
Causes
The main routes of transmission are:
- Bites and scratches during fights between cats.
- Blood-feeding insects and external parasites, including fleas and ticks.
- Transfusion of infected blood.
- Transmission from a mother to her kittens, rarely.
This list does not mean that every route is equally well established. Transfusing infected blood can spread infection. Natural transmission routes, however, are poorly understood. Fleas and ticks have been suspected as vectors, but evidence that they play a significant role in feline haemoplasma infections is weak. Information about mother-to-kitten transmission is also limited.
Blood contact during fights is a possible explanation for the risk associated with outdoor access. The absence of fleas does not rule out infection, and flea prevention is not regarded as reliable protection against haemoplasmas. Infection is not inferred from finding a single tick either.
Risk factors
- Unrestricted outdoor access and contact with other animals.
- Lack of flea and tick protection.
- FeLV or FIV infection, associated with more severe disease.
- Poor condition and chronic illness.
- Young males that fight outdoors.
The likelihood of infection and the severity of symptoms are different matters. A chronically infected cat may have no symptoms, with infection discovered during investigations for another reason. FeLV, FIV and other illnesses are considered, but not every positive cat develops severe anaemia. The risk profile of a young outdoor male does not rule out disease in other cats.
Typical symptoms
- Fever.
- Tiredness, weakness and apathy.
- Pale or yellowish mucous membranes, reflecting anaemia and sometimes jaundice.
- Weight loss.
- Faster breathing and heart rate.
- In severe cases, collapse and a life-threatening condition.
At home, changes may include avoiding jumping, sleeping more than usual or a reduced appetite. Pallor suggests possible anaemia but does not identify its cause. A yellowish colour may be associated with red blood cell breakdown, but liver and biliary causes are also investigated.
Rapid breathing may result from impaired oxygen transport rather than a primary lung disease. Breathing difficulty nevertheless needs immediate assessment. Fluctuating condition or a temporary improvement does not establish that red blood cell numbers have recovered.
Complications and consequences
Untreated haemoplasmosis can lead to:
- Severe haemolytic anaemia.
- Insufficient oxygen reaching tissues and internal organs.
- Secondary bacterial infections.
- Chronic carrier status and repeated relapses.
- Death in severe disease.
Not every cat develops all the listed consequences. An asymptomatic carrier state is not the same as continuously active haemolytic disease. Conversely, severe anaemia may need urgent supportive care before its cause is confirmed. Another concurrent illness can affect both symptoms and prognosis.
Diagnosis at the vet
Investigations used to diagnose the disease include:
- A complete blood count, showing anaemia and reticulocytosis.
- Microscopic examination of a blood smear for mycoplasmas on red blood cells, although this method has limited sensitivity.
- PCR testing, the most accurate method.
- Blood biochemistry to assess the liver and kidneys.
The blood count assesses the severity of anaemia and the number of young red blood cells, or reticulocytes. An increase supports the interpretation that the marrow is responding to red blood cell loss. Other causes of anaemia, such as bleeding or another disease that destroys red blood cells, are investigated when necessary.
A blood smear may suggest infection, but a negative microscopic finding does not rule it out. The number of infected cells can vary, and few organisms may be present in the sample. PCR detects bacterial genetic material and can also help distinguish the haemoplasma species. Tell the vet about all antibiotics and other medicines given before sampling.
A positive PCR alone does not establish that haemoplasmas are causing this particular cat's anaemia. Carrier status and another cause of anaemia may occur together. The result is interpreted alongside the blood count, symptoms and other findings. FeLV and FIV tests can look for concurrent infections, but their results are interpreted separately too.
Treatment
Symptomatic infection is treated with an antibiotic active against haemoplasmas, such as a doxycycline product selected by the vet. The appropriate medicine and treatment duration depend on your cat's condition, the organism and the response. Antibiotic treatment is not automatically necessary for a symptom-free cat with only a positive PCR result.
An antibiotic can control clinical disease even if the bacterium is not completely eliminated from the body. Follow-up therefore assesses both red blood cell values and your cat's condition. Persistent or recurrent signs may require the diagnosis, concurrent illnesses and medication to be reviewed. Corticosteroids are not routine treatment for every haemoplasma infection; their need is assessed separately if another immune-mediated cause of haemolysis is suspected.
Severe anaemia may require a blood transfusion. Donor blood is selected and compatibility assessed at the practice. Pain, nausea, nutrition and any necessary fluid support are also addressed. Iron supplements alone do not treat an infection that destroys red blood cells, and they should not be started simply because a cat looks pale.
Giving medication and monitoring at home
Ask to be shown how to give the prescribed medicine. In particular, a doxycycline tablet or capsule lodged in the oesophagus can irritate and damage it. The vet will explain the appropriate administration method and whether water or food should follow the medicine. Do not leave your cat to swallow a dry tablet without the safety instructions provided.
Contact the practice if your cat drools, has difficulty swallowing, regurgitates or refuses food during medication. Report unsuccessful administration so treatment can be made to work. Do not force food or water into a weak cat's mouth. Nutritional support can be arranged at the practice when needed.
Monitor appetite, activity, breathing, mucous membrane colour and weight. Keep your recovering cat in a quiet environment and prevent fights. Agreed blood tests confirm that the anaemia is resolving; appearing brighter alone is insufficient reason to end treatment. New weakness, breathing difficulty or loss of appetite warrants prompt contact.
Prognosis and carrier status
The prognosis is often good when symptomatic disease is recognised and treated early. Severe anaemia and concurrent illnesses may worsen it. A cat that appears clinically recovered may remain a carrier, so mention the previous infection to the vet if anaemia recurs. A carrier must not be chosen as a blood donor simply because it looks well.
Prevention
- Maintain regular flea and tick protection.
- Avoid unrestricted roaming and fighting.
- Test donor blood before transfusion.
- Address viral infections promptly and support immunity.
Blood donors are screened for haemoplasma infections using PCR, because a cat without symptoms can still carry the bacterium. External parasite control is chosen to suit the cat and its exposure risk, although its effectiveness in preventing haemoplasma infection has not been established conclusively. Reducing fighting and uncontrolled roaming reduces opportunities for blood contact.
Monitoring diagnosed FeLV and FIV infections and treating other illnesses are useful, but cannot be replaced by a general promise to boost immunity. Medication cannot eliminate every chronic viral infection. The care plan is based on the diagnosed illness and your cat's needs.
Important for cat owners
Haemoplasmosis is a dangerous infection, particularly in cats with weakened immunity. If your cat is tired, feverish and has pale mucous membranes, take it to a vet without delay. Prompt investigation and treatment can save your cat and bring the disease under control.
This article provides general information and does not replace veterinary care. Contact a vet if you notice signs of illness in your cat.
Frequently asked questions
Does a positive PCR always mean disease requiring treatment?
No. A cat can be an asymptomatic carrier, and anaemia may have another cause. Treatment needs are decided according to symptoms, the blood count and other findings.
Can a cat that seems healthy develop severe disease?
Yes. Mycoplasma haemofelis can cause significant anaemia without a previously diagnosed immune problem. Other haemoplasma species often cause milder disease, but every finding is interpreted individually.
Does flea treatment reliably protect against infection?
No. External parasite control is part of risk-based care, but evidence for fleas and ticks as haemoplasma vectors is weak. Good parasite protection does not rule out infection.
Does an antibiotic eliminate the bacterium completely?
Not always. Symptoms and anaemia may resolve while the cat remains a carrier. Follow-up and assessment of any new symptoms are therefore planned with the vet.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Guideline for Haemoplasmosis in Cats, European Advisory Board on Cat Diseases, accessed 2026-11-03.
- Hemotropic Mycoplasma Infections in Animals, Merck Veterinary Manual, accessed 2026-11-03.
- Feline Hemotrophic Mycoplasmosis, VCA Animal Hospitals, accessed 2026-11-03.
- Anaemia, Cornell Feline Health Centre, accessed 2026-11-03.
- Guideline for Blood Transfusion in Cats, ABCD, accessed 2026-11-03.
- 2020 AAFP Feline Retrovirus Testing and Management Guidelines, Journal of Feline Medicine and Surgery, accessed 2026-11-03.
- Giving Your Cat Oral Medications, Cornell University College of Veterinary Medicine, accessed 2026-11-03.
- Initial Triage and Resuscitation of Small Animal Emergency Patients, Merck Veterinary Manual, accessed 2026-11-03.
- 2022 ISFM Consensus Guidelines on Management of the Inappetent Hospitalised Cat, Journal of Feline Medicine and Surgery, accessed 2026-11-03.