Mycoplasma haemolamae in alpacas with ill-thrift and anaemia

Alison Lee
Principal Veterinary Officer – Product Integrity/OJD, Agriculture Victoria

In July 2018, four alpacas on a property north-east of Melbourne presented with ill-thrift and anaemia. Samples sent for laboratory testing confirmed infection with Mycoplasma haemolamae (previously Eperythrozoon sp.).

Mycoplasma haemolamae are bacteria that affect red blood cells of alpacas and other camelids. Since their re-classification to the Mycoplasma genus, they are commonly referred to as haemotropic mycoplasmas or haemoplasmas to distinguish them from the other mycoplasma organisms that cause reproductive, respiratory and joint diseases (for example, in New Zealand dairy herds).

Infection with M. haemolamae is usually subclinical, but clinical disease may occur secondary to other concurrent diseases or causes of stress or immunosuppression.

Prevalence

M. haemolamae were first diagnosed in the United States in 1990 and has since been diagnosed in alpaca populations in:

• South America
• Europe
• New Zealand
• Australia.

International prevalence studies have reported up to approximately 30 per cent of herds as affected although clinical expression of disease is considerably lower than this.

The prevalence of M. haemolamae in Australia is unknown, but it has been detected in a small number of herds. M. haemolamae is not a notifiable disease in Victoria. Each of the clinical cases reported to Agriculture Victoria appear to have been associated with other concurrent conditions such as internal parasitism. When concurrent disease processes are present, particularly if they contribute to anaemia (for example, haemonchosis) it may be difficult to determine the degree to which M. haemolamae is contributing to the animal's ill-health.

Clinical signs

As the clinical presentation (or detection) of M. haemolamae may be secondary to other diseases or causes of immunosuppression, clinical signs may vary.

Signs associated with M. haemolamae may appear as either acute or chronic disease. Signs of acute disease include inappetence, sudden weakness and sometimes fever, while chronic signs may present as lethargy, weight loss/wasting, or decreased fertility.

As these bacteria result in the destruction of red blood cells, anaemia or jaundice may be present. Given that alpacas are considerably slower than other livestock species to regenerate red blood cells, anaemias may appear to be either regenerative or non-regenerative.

Transmission

The transmission of M. haemolamae is not completely understood but the most likely form of transmission is via biting insect vectors. Iatrogenic transmission (reused needles or blood transfusions) is also possible.

Diagnosis

It is essential that blood smears are made in the field, as M. haemolamae are known to detach from red blood cells during sample transportation, with potential negative results upon arrival at the laboratory. Also, if anaemia is severe (a significant number of red blood cells have already been destroyed), M. haemolamae may be in lower numbers when examining smears.

PCR testing is useful to confirm the presence of M. haemolamae. Although there are currently no validated PCR tests in Australia, some veterinary laboratories may be able to provide unvalidated testing. Further information can be obtained through direct contact with your preferred laboratory. Another option is to forward samples to Oregon State University.

Treatment

Treatment for clinically affected animals consists of 20 mg/kg bodyweight long-acting oxytetracycline, given subcutaneously, every three days for two to five treatments (off-label treatment). Supportive treatment (for example, blood transfusion) and treatment of concurrent conditions (for example, internal parasitism or nutritional deficits) may also be required.

Antibiotic treatment may be ineffective in eliminating the organism from affected animals, and they may become carriers or relapse if another stressful event occurs. Re-infection is also possible, given there may be other sub clinically affected animals in the herd.

The options of treating the whole herd with oxytetracycline or testing and treating those animals that return positive results, could also be considered. The latter option may be more attractive if a validated PCR was available in Australia.

Prevention

The control of possible insect vectors may assist prevent the spread of M. haemolamae. Iatrogenic spread could be reduced by taking care not to reuse needles and other potentially contaminated equipment.

Notification

Although M. haemolamae is not a notifiable disease in Victoria, Agriculture Victoria is interested to hear of any cases of M. haemolamae to get a better knowledge of its prevalence in Victoria.

Forward details of cases to our Principal Veterinary Officer. Call the Customer Service Centre at 136 186.