Mycoplasma haemocanis in Dogs: Symptoms, Splenectomy Risks, and Treatment

Introduction

Mycoplasma haemocanis is a specialized organism that lacks a cell wall and clings to the erythrocyte membranes of dogs. Although the bacterium may remain silent in normal dogs, it may cause serious life-threatening anemia under certain conditions.

Unlike Ehrlichia which stays inside white cells, Mycoplasma attaches to the outside of red blood cells, leading to their destruction in the spleen.

​Attack Mechanism

​The bacterium differs from others because of its epicellular attachment to the RBC membrane.

​Immunological Response: 

The dog's immune system identifies "coated" cells as either damaged or foreign organisms.

​Extravascular Hemolysis: 

The infected RBCs are filtered out and destroyed in the spleen.

​The Outcome: 

Decrease in the RBC numbers causes regenerative anemia in a short time.

​Risk Groups, Clues, and Symptoms

​Normal Healthy Dogs: 

Usually act as silent carriers; spleen keeps the infection in check.

​Splenectomized Dogs: 

Dogs who have their spleen removed carry the highest risk of suffering. Absence of the spleen leaves the infection uncontrolled.

​Immunocompromised Dogs: 

Dogs under chemotherapy treatment, those with multiple infections (Ehrlichia, Babesia, etc.).

​Clinical Symptoms and Physical Signs

​Pale Mucous Membrane: 

Examine the gums; they become pale or light pink.

​Lethargic and Weak: 

Lack of oxygen due to destruction of red blood cells.

​Icterus or Jaundice: 

If the process proceeds quickly enough, the body accumulates bilirubin, turning whites into yellow.

​Fever and Weight Loss.

Diagnosis & Therapy

Blood Smear: 

Detection of small cocci, rods, or rings attached to the membrane of RBCs with Giemsa or Wright stains.

Note: 

The parasite may be detached from RBCs in EDTA blood sample, making fresh blood smear preferable.

PCR: 

Most accurate diagnostic test available.

Therapy: 

Doxycycline works well, although Enrofloxacin is commonly used for Mycoplasmosis in dogs.

Life Cycle of Mycoplasma haemocanis 

​1. Transmission (The Vector Phase)

​Primary Vector is the Brown Dog Tick (Rhipicephalus sanguineus).

​The bacterium is transferred into the host during the tick bite.

​Alternative Modes of Transmission: 

The disease may be transmitted through blood transfusion, injections with contaminated needles because bacteria are constantly in the bloodstream of the carrier animals.

​2. Epicellular Attachment (The Host Phase)

​M. haemocanis remains extracellular as opposed to the Ehrlichia spp which invades the cells. In other words, it attaches to the cell surface.

​The "Ring": 

The bacteria attach in chains, small dots (called cocci) or ring-shaped formations to the RBC cell surface.

​Nutrient Absorption: 

Due to lack of the cell wall and having a very small genome, Mycoplasma uses direct nutrient absorption from RBCs for survival and reproduction.

​3. Recognition by the Immune System and Erythrophagocytosis

​Bacterial multiplication causes disruption of the surface of erythrocytes thus exposing the previously hidden antigens.

​The Role of the Spleen: 

The spleen serves as a "quality control" mechanism whereby when such abnormal or "flagged" erythrocytes circulate through the splenic sinuses, splenic macrophages recognize them.

​Degradation: 

They degrade and consume the erythrocyte completely (erythrophagocytosis).

​4. Carriers (Latent Infection)

​In a normal dog with a normally functioning spleen, the removal of infected cells occurs at a constant rate.

Clinical carrier stage: 

The bacteria are present in the dog's body, but in trace amounts.

Reactivation stage: 

In cases where the dog experiences stress or suppression of the immune system or splenectomy, the “filter” will be absent, causing the bacteria to multiply excessively, resulting in hemolytic crisis.

The life cycle of M. haemocanis involves biological vector transmission and strategic attachment to red blood cell membranes, culminating in extravascular hemolysis within the spleen.

Conclusion: The Significance of Alertness

To conclude, despite being considered less dangerous due to its "silent" nature in normal animals, Mycoplasma haemocanis continues to pose a significant risk in canine hematology. Given the possibility for this microorganism to cause acute hemolytic complications in dogs who have been splenectomized or have weakened immune systems, it can no longer be underestimated.

There are several aspects that must be considered for the efficient treatment of M. haemocanis infection:

1.The early identification through highly sensitive PCR tests as well as analysis of the patient's blood samples.

2.A strict treatment regimen involving administration of either Doxycycline or Enrofloxacin.

3.Control of the vectors – Brown Dog Ticks, which cannot be achieved without proper management.

4.The relationship between the immune system of the host organism and M. haemocanis should be considered carefully.