Problems with the diagnosis of haemotropic mycoplasma - like infection in the European wisent (Bison bonasus)

Abstract

A veterinarian treating wildlife must sometimes provide assistance to a sick animal based on incomplete data. Animals of special biological value are not the same as livestock. Some procedures routinely performed on domestic animals require pharmacological restraint in the veterinary service of large and dangerous wild animals. Therefore, such procedures are performed only in situations of absolute necessity. Such a situation took place in the Gdańsk zoo when a young European wisent (Bison bonasus) showed symptoms of haemotropic mycoplasma infection. Hemotropic mycoplasmas cause intravascular infection by attaching to red blood cells and triggering an immune response leading to elimination of the affected cells. This process can result in the development of hemolytic anemia. The case of suspected hemotropic mycoplasmosis in a European wisent described in this paper concerns an almost 2-year-old female, who lost her mother at the age of 11 months and from that time was the lowest in the hierarchy in the group of 10 wisents exposed at the zoo. The disease was manifested by emaciation, marked weakness, protrusion of the third eyelid and severe pallor of the mucous membranes. The sick animal was immobilized. Collected blood showed significant anemia (RBC 1.51 T/l, Ht 0.08 l/l), and microscopic imaging showed characteristic cells adjacent to erythrocytes suggestive of hemotropic mycoplasma infection. The animal was treated with a long-acting oxytetracycline administered three times a week, for 6 weeks. At the end of the 6-week treatment the wisent was immobilized and it was found that the nutritional status of the animal improved, the third eyelid returned to its physiological state and the pallor of the mucous membranes disappeared completely. Examination proved that the red blood cells and hematocrit reached a state that could be interpreted as physiological (RBC 4.89 T/l, Ht 0.26 l/l0, no microscopic changes of RBCs. Unfortunately, the available laboratory methods did not confirm the presence of mycoplasma genetic material. However, the efficacy of the used antibiotic therapy could be a confirmation that the disease was caused by hemotropic mycoplasmas.