Improving the specificity of indirect immunofluorescence for the serological diagnosis of bovine anaplasmosis.

Fluorescing inclusion appendages were detected consistently in preparations of Anaplasma centrale and Anaplasma marginale when they were used as antigen in indirect immunofluorescence serological tests for the diagnosis of anaplasmosis in cattle. The presence of the inclusion appendages made it possible to confirm the specificity of the immunofluorescent reaction and to determine end-points with accuracy.

Viability of Theileria parva trivalent stabilate after thawing and maintenance at 4 degrees C for up to 15 hours.

Two experiments were conducted to determine the effect of prolonged maintenance at 4 degrees C on thawed Theileria parva stabilates. Samples maintained at 4 degrees C for 1, 12, 15 and 18 h were all infective for cattle. Immunized cattle were able to resist potentially lethal challenges 29 days later. These results indicate that the handling of T. parva trivalent stabilates for immunization against East-Coast fever in the field should be much easier than previously envisaged.

Theileria parva (Kasoba): isolation and challenge of cattle recovered from infection with other Theileria parva stocks.

A pathogenic Theileria stock was isolated from control cattle during an East Coast Fever (ECF) field immunization trial at Kasoba near Karonga town in northern Malawi. A stabilate of this stock caused severe fevers and prolonged parasitosis in Theileria parva naive cattle, resulting in the death of 5 out of 12 cattle despite treatment. In contrast, this parasite stock caused mild to moderate reactions in 17 cattle immunized with the trivalent T. parva stabilate except in 3 animals which developed severe reactions, and one of them died. Another time, cattle immunized with buffalo-derived Theileria parva (Serengeti transformed) resisted a potentially fatal challenge, with only mild to moderate reactions being recorded. The parasite stock was morphologically and serologically indistinguishable from Theileria parva (Muguga); it was virulent and could cause mortality, particularly in T. parva naive cattle. The parasite stock was designated Theileria parva (Kasoba).

Bulk-freezing of Theileria parva stabilates for vaccine production.

The freezing and thawing characteristics of different volume samples of freezing medium and Theileria parva stabilates were studied in order to identify suitable conditions for freezing large volumes of stabilates for use in the preparation of vaccines. Conventionally, 1.8 ml aliquots are used but are cumbersome to handle in the field preparation of trivalent vaccines. In this study, 75 ml aliquots of the stabilates were found to exhibit freezing and thawing characteristics similar to those of the 1.8 ml aliquots. Bulk freezing of 2 stabilates yielded sporozoites which remained infective for cattle upon thawing, induced a range of clinical reactions in vaccinated cattle and stimulated the development of immune reactions.

Isolation of Theileria parva (SAO Hill) and Theileria parva (West Kilimanjaro) and their cross-immunity with Theileria parva (Kasoba).

Two Theileria parva stocks were isolated from control cattle during East Cost fever (ECF) field immunization trials at SAO Hill and West Kilimanjaro in the southern and northern parts of Tanzania respectively. Both parasite stocks caused severe clinical ECF which required antitheilerial treatment for 3 of the 5 experimentally infected cattle. Cattle recovering from infection with the two T. parva stocks did not develop a fever and only 1 of 4 animals developed scanty schizont parasitosis for one day during a challenge with T. parva (Kasoba) from northern Malawi. In contrast, both control cattle developed fever and schizonts, and one required antitheilerial treatment to survive.

Immune effector mechanisms involved in the control of parasitaemia in Trypanosoma brucei-infected wildebeest (Connochaetes taurinus).

The course of Trypanosoma brucei infection in the wildebeest (Connochaetes taurinus) was studied. A low but persistent parasitaemia developed in all five wildebeest following intravenous inoculation with 1 X 10(8) organisms of clone ILTat 2.1. Unlike cattle controls, however, the wildebeest did not develop anaemia. In both cattle and wildebeest, radioimmunoassay studies revealed a classical sequence of production of IgM, IgG1 and IgG2 antibodies which had the capacity to bind to the corresponding purified variable surface glycoprotein and to neutralize the infectivity of ILTat 2.1. Investigations into the interaction between post-infection sera, trypanosomes and freshly isolated peripheral blood leucocytes (PBL) of wildebeest and cattle showed that sera from the wildebeest had a higher capacity to induce adherence of trypanosomes to homologous PBL. The adherence and phagocytosis-inducing activity resided in the IgM fraction. Cross-testing of the antibodies and PBL revealed that wildebeest IgM antibodies induced high adherence indices when tested on cattle PBL. High adherence indices were also observed when cattle IgM antibodies were tested on PBL of wildebeest. It was concluded that the phagocytic system of the wildebeest was superior to that of cattle, that freshly prepared wildebeest PBL bear receptors for wildebeest as well as cattle IgM, and that cattle PBL bear a receptor for wildebeest IgM that would appear to be different from that for cattle IgM.

The response of Bos taurus and Bos indicus cattle types to inoculation of lymphoblastoid cell lines infected with Theileria parva schizonts.

In a preliminary experiment eight Bos indicus type cattle were inoculated with 10(9) cells of a Bos taurus lymphoblastoid cell line infected with Theileria parva schizonts. Four cattle showed patent infections and one died of theileriosis. On challenge of the surviving cattle with a tick derived stabilate of the same stock of T. parva no animal died of theileriosis. To test the susceptibility of Bos taurus and Bos indicus cattle to cell lines of both cattle types infected with T. parva of the same stock, 10(9) cells of each cattle type were inoculated into five cattle of each type. Bos taurus cattle had a higher susceptibility to infection regardless of the origin of the donor cells. Two Bos taurus type cattle receiving Bos taurus cells died of theileriosis while none receiving Bos indicus cattle died. Both cattle types were more susceptible to infection with cells derived from their own cattle type. All surviving Bos indicus and Bos taurus cattle were immune to lethal stabilate challenge. The possibility that the histocompatibility type of the donor cells influences the success of the immunization is discussed.