Theileriosis in eland

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Context/Importance

A high prevalence of Theileria infections is found in eland. Theileria taurotragi was first described by Martin and Brocklesby in 1960 [1], under the name Cytauxzoon taurotragi, as a benign parasite of the eland (Taurotragus oryx). It was subsequently demonstrated that the parasite was readily transmissible to cattle, in which it caused a transient febrile reaction, and it became clear that T. taurotragi was one of the benign theilerial parasites of cattle which had been known collectively as Theileria mutans since the beginning of the twentieth century.

The parasite is widely distributed through eastern and southern Africa, and in addition to cattle and the eland, sheep and goats can be infected experimentally. Its main significance is the confusion that it causes in the differential diagnosis of mild reactions to Theileria parva as it causes mild clinical signs in cattle that were experimentally infected.

The first cases of theileriosis in eland were described by Grootenhuis et al. in 1980 [2]. These were three natural cases and two that were experimentally produced; all the animals died because of the infection. Generalised lymphadenopathy was the consistent feature in all the animals while wasting is seen in the prolonged cases. Two of the natural cases manifested severe terminal diarrhoea while one died while suffering from severe respiratory distress

Theileriosis was also recently diagnosed in a group of ten eland (Taurotragus oryx) that were translocated from the Vryburg district to Magaliesburg in the Gauteng province, South Africa. Two of the ten animals died a month after transportation to the new premises. They were tick-infested. The features of the disease at necropsy were distinct and should be indicative of such an infection should they be detected.

Epidemiology

The infection is transmitted between eland by Rhipicephalus appendiculatus and R. phallelus[3]

Pathogenesis

Clinical sings and pathology

The main features of the disease in animals that died of the infection include lesions in the lymph nodes, spleen, abomasum, intestines, adrenal, lungs, heart, liver, kidneys, and the central nervous system.

The following figures demonstrate the parasitic stages seen in a lymph node smear (Fig. 1, Fig. 2. and Fig 3.), and the macroscopical lesions present in one of the animals at necropsy.

Diagnosis

Examination of blood smears will confirm the diagnosis but will not identify the specific species of the parasite. In animals that die of the infection, piroplasm parasitaemia may be as high as 50% while schizonts are present in smears made from lymph node biopsy specimens and in lymphoid smears made during necropsy. The structural features of the schizonts are distinctly different from those of T. parva [2].

A presumptive diagnosis can be made on the basis of histopathological findings typified by the infiltration of large parasitised lymphoid cells in tissues and organs throughout the carcass: lymphoid organs, intestinal tract, adrenal glands, liver, lungs heart, kidneys, and central nervous system. These cells occurred intra- and extra-vascularly and were accompanied by necrosis, thrombosis, and haemorrhage [2].

Control/Management

References

  1. Brocklesby, D.W., 1962. Cytauxzoon taurotragi, Martin and Brocklesby, 1960, a piroplasm of the eland (Taurotragus oryx pattersonianus, Lydekker, 1906) Research in Veterinary Science, 3, 334–344
  2. 2.0 2.1 2.2 Grootenhuis, J. G., Morrison, W. I., Karstad, L., Sayer, P. D., Young, A. S., Murray, M., & Haller, R. D., 1980. Fatal theileriosis in eland (Taurotragus oryx): pathology of natural and experimental cases. Research in Veterinary Science, 29, 219-29U.
  3. Grootenhuis, J. G., Young, A. S., Kanhai, G. K., & Paling, R. W., 1977. Experimental tick transmission of Theileria species between eland. The Journal of Parasitology, 1127-1129. http://www.jstor.org/stable/3279866