A protozoan red blood cell parasite of cattle, historically referred to as Theileria buffeli, has been present in Australia for many years. It was a common incidental finding in blood smears taken from cattle in Queensland and coastal NSW where bush ticks where prevalent and was long considered a benign infection, with clinical disease being rare. Smeal (2000) reported that while the parasite was common in cattle in NSW between the far north and central coasts, acute disease had only been confirmed in 3 animals in that region between 1990 and 1994.
Cases of bovine anaemia due to Theileria orientalis in naïve adult cattle introduced into the region were first diagnosed in the Kempsey region in 2006. Izzo et al (2010) reported 8 cases of clinical disease associated with Theileria infections.
Over the last 10 years there has been significant research into Theileria in Australia. Kamau et al (2011) demonstrated that 3 genotypes exist in Australia – Ikeda, Chitose and Buffeli. Eamens et al (2013) found that clinical disease is strongly linked to the presence of Ikeda genotype, either on its own or in mixed infections with Chitose and/or Buffeli.
Cases of bovine anaemia continue to occur in the North Coast Local Land Services region in both adult cattle introduced to the area from tick free areas and also in homebred calves at 6-12 weeks of age.
This report describes 2 cases of bovine anaemia in beef calves in the Kempsey region.
The owner of a small Speckle Park herd near Rollands Plains contacted the district veterinarian in September 2016 reporting illness in two young homebred calves. The property ran two separate herds of cattle, the Speckle Park herd of 40 cows and a predominantly Angus herd of 120 cows. Illness had only been noted in the Speckle Park calves at that time.
The cows were grazing improved pasture comprising rye, white clover, chicory and plaintain. All cows were in good body condition and feed supply was plentiful. The owner reported that some calves had been scouring approximately 1-2 weeks earlier, though had recovered without specific treatment. Two calves were now noted to be lethargic and reluctant to move with the mob when changing paddocks. The cattle were yarded, with one calf becoming recumbent before reaching the yards.
Both calves examined were 8 weeks of age. Calf 1 was recumbent, had a rectal temperature of 37.2, dry pellet-like faeces with mucous covering and had very pale mucous membranes (Figures 1 and 2). Calf 2 had pale mucous membranes, rectal temperature of 40.1 and an increased respiratory rate. Blood samples were collected into plain and EDTA tubes from both calves.
Calf 1 died shortly after the clinical examination commenced and a post mortem examination was conducted. Gross findings including pale, slightly jaundiced carcase, spleen enlarged approximately two times normal size (Figure 3) and an enlarged ochre-coloured liver (Figure 4). A diagnosis of bovine anaemia was made based on signalment and clinical findings, samples were submitted to the State Veterinary Diagnostic Laboratory at EMAI.
Laboratory testing supported a diagnosis of bovine anaemia due to Theileria orientalis. There was evidence of a regenerative anaemia in both calves and the presence of organisms consistent with Theileria sp. Laboratory findings are summarized in table 1 below.
Table 1 – Haematology
|Calf 1||Calf 2|
|Packed Cell Volume (23-44%)||6%||10%|
|RBC Size||Anisocytosis +||Anisocytosis +|
|RBC Shape||Poikilocytosis +||Poikilocytosis +|
|Blood Parasites consistent with Theileria sp.||<5% of RBCs||5-10% of RBCs|
The owner of a small beef cattle herd in Kempsey contacted the District Veterinarian on September 19 following the death of a 3 month old calf. The owner reported that the calf had been lethargic over the weekend and had been found dead on Monday morning. The owner reported that she had lost two calves in the previous calving season which had showed very similar signs.
The property ran 30 Hereford cows on the Macleay river floodplain. Cows had been grazing predominantly kikuyu and clover paddocks, and the owner had also been strip grazing rye and clover.
The calf was very well grown and in excellent body condition. An external examination revealed pale mucous membrane. A post mortem examination was conducted. Findings included pale carcase, enlarged ochre-coloured liver (Figure 5) and an enlarged spleen (Figure 6). A diagnosis of bovine anaemia was made based on gross findings samples were not submitted for laboratory testing.
Anaemia due to Theileria orientalis remains a frustrating disease in the North Coast LLS region for both producers and veterinarians with treatment options limited. Treatments used most commonly include oxytetracyclines and imidocarb, some veterinarians are using Baycox (Toltrazuril, Bayer) as a prophylactic. Further trial work on the efficacy of some of these treatments is required. Blood transfusions may be an option and are used quite widely in New Zealand (Briggs, 2014). Minimising stress on affected animals remains an important part of management. Handling should be minimised and, if necessary, should be done quietly and slowly.