The Susceptibility of Kenana Cattle to Tropical Theileriosis in the Sudan

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Mohamed Ahmed Bakheit Ahmed, Ahmed
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This work was carried out to study the course of Theileria annulata infection in Kenana cattle and to assess the innate resistance of the breed to tropical theileriosis. Nine Kenana calves were purchased from El Damazin Livestock Market and brought the Department of Parasitology, Faculty of Veterinary Science, U. of K. They were found negative to T. annulata antibodies in the indirect fluorescent antibody test. They were divided into two groups. The first group of 5 (was infected by subcutaneous injection of 1.0 ml (equivalent to 10 ticks) of ground up tick supenatant stabilate prepared from experimentally infected Hyalomma anatolicum anatolicum adults. The second group of 4 calves was infected by application live adult ticks from the same batch. A third group of three Friesian calves was infected by stabilate injection and served as a susceptible control. All animals in the 3 groups reacted to different degrees to the T. annulata infection. The prepatent period to lymph node enlargement, body temperature, schizont appearance and piroplasm parasitaemia were the same in the 3 groups. The percentage of schizont parasitosis (Macroschizont Index, MSI) was three times less in the Kenana stabilate-infected group (16.6 ± 24.7) compared to the Friesian (57.0 ± 29.4). The percentage of parasitaemia was also significantly less (P < 0.05) in the Kenana stabilate-infected (1.7 ± 1.3) than in the Friesian group (12.6 ± 17.7) and that was attributed to the higher rate of schizont multiplication in the latter group. The haematological findings revealed that the rate of white blood cells reduction was significantly greater (P < 0.05) in the Friesian group than in the Kenana stabilate-infected. This difference appeared to be associated with severe disease and high MSI. Seventy eight per cent of the Kenana animals recovered spontaneously and only 22% required treatment compared to the 100% mortality in the exotic Friesian group. On the other hand, the two Kenana groups behaved similarly to the infection; in each group, one animal showed a severe reaction and was treated, one showed a severe reaction and recovered, two showed a moderate reaction and the fifth animal in the Kenana stabilate-infected group showed a mild reaction. There were no significant differences in the maximum MSI, duration of schizont parasitosis, maximum piroplasm parasitaemia and duration of parasitaemia. There was also no significant difference in haematological parameters (packed cell volume, white blood cells count, red blood cells count and haemoglobin concentration). The similar behaviour of the two Kenana groups was presumably due to the low number of applied ticks which was not sufficient to cause strong sensitization in the animals to affect transmission of the parasite. All Kenana cattle developed high antibody titres to T. annulata schizont antigen in the IFA test and the seroconversion started on day 12 after the infection. Sera from the Friesians were found negative in the IFA test. It is concluded that the ability of the Kenana cattle to limit the macroschizont multiplication, resulting in less severe damage of the lymphoid tissues during the acute phase of the disease, is the probable basis of their resistance. The resistance of Kenana to the disease and to tick infestation makes them suitable for breeding or cross-breeding programs when aiming at controlling tropical theileriosis in the Sudan
: The Susceptibility of Kenana Cattle to Tropical Theileriosis in the Sudan