Two natural human interferon alpha preparations, (nHuIFN-μ [Cantell]) and (Nhuifn-μ [ISI]), were used for the oral treatment of cattle experimentally infected with Theileria parva parva. In the first experiment, 8 Friesian bulls were inoculated with a 1 in 10 dilution of a sporozoite stabilate of T. p. parva (Marikebuni) stock. Four of the cattle were treated daily with 1 international unit/kg body weight (i.u./kg bwt) of nHuIFN-μ (Cantell) from day –2 to day 8 p.i. None of the 4 calves given IFN developed clinical theileriosis, but 3 of the 4 control calves died of theileriosis while the fourth had a mild infection. Three of 4 treated calves and the 1 surviving control calf developed a detectable antibody response to T. p. parva schizont antigen but, on challenged with a 10-fold higher dose of stabilate, the surviving control animal and only 1 of the 4 treated calves proved to be immune. In a second experiment, 4 groups of 4 calves were inoculated with the same stabilate dilution. Three treatment groups were given either 1 i.u. nHuIFN-μ (Cantell), 1 i.u. nHuIFN-μ (ISI), or 10 i.u. nHuIFN-μ (ISI)/kg bwt from day –2 to day 8 p.i. once daily and the fourth group were controls. Clinical theileriosis occurred in 2 controls, 2 calves given 10 i.u. nHuINF-μ (ISI), 1 calf given 1 i.u. nHuIFN-μ (ISI) and no calves given 1 i.u. nHuIFN-μ (Cantell)/kg bwt. Of these, 2, 1, 0 and 0 cattle died in the respective groups. All the surviving cattle proved to be immune on homologous challenge with 10-fold higher dose of stabilate except the 2 cattle which did not develop high antibody responses. A third experiment using an undiluted challenge of T. p. parva (Muguga) sporozoite stabilate (10α) on 8 steers. Four steers were treated with 1 i.u. nHuIFN-α (Cantell)/kg bwt and 4 were controls. All calves developed acute theileriosis and the experiment was terminated. Cells of the C2 lymphoblastoid cell line, infected with T. p. parva (Muguga) schizonts, were cultured in vitro with various concentrations (0-01-100 i.u./ml) of nHuIFN-a (Cantell). The IFN appeared to have no effect on host cell or parasite developmental variables when compared to untreated control cultures.

Two mathematical models are developed that investigate the transmission dynamics of Theileria parva by the ixodid tickRhipicephalus appendiculatus to cattle in endemically stable areas. A method of estimating the rate of infection to cattle ofT. parva at the endemically stable state is given. Empirical estimates of ail the parameters in the model are available. The degree to which animals that have recovered from theileriosis (the ‘carrier’ state) are able to transmit the infection to tick nymphs or larvae is a crucial determinant of the dynamics of infection in a herd. Two control methods influencing the transmission of infection are considered – infection and treatment immunization and the reduction in tick feeding by acaricide application. The impact of each method on the transmission of infection is evaluated. Future developments and the data required to predict the dynamics of T. parva infections in cattle and ticks are discussed.

Tick populations were monitored between October 1991 and September 1992 at monthly intervals on 10 Boran (Bos indicus) heifers at Didtuyura ranch, Yabelo district, Ethiopia. Twelve different tick species in four genera were identified from a total of 16 026 specimens collected. Of all the ticks collected, Rhipicephalus spp. constituted 84.7%, Amblyomma spp. 9.9%, Boophilus spp. 4.8% and Hyalomma spp. 0.24%. The ventral parts of cattle were found to be the most favoured feeding sites for most of the ticks collected. The size ranges of the standard ticks collected were 4–8 mm; 9–16 mm; 4–8 mm and 8–13 mm for R. pulchellus, A. variegatum, B. decoloratus and A. gemma, respectively, while their respective male to female sex ratios were 2:1; 3.2:1; 1:5.4 and 2.6:1. Packed cell volume (PCV) values of blood samples taken from 600 cattle were monitored monthly during the study period. There was a reduction in PCV during the dry season of the year but generally the values were within the normal range of 32–40%. The parasites causing anaplasmosis, babesiosis and theileriosis (T. mutans) were detected by microscopic examination of blood smears and serologically (ELISA) at seroprevalence rates of 94.68%, 77.19% and 30.9% respectively.

Deltamethrin (IR, 3R)-3(2,2-dibromovinyl)-2, 2-dimethylcyclopropane carboxylate of (S)-alpha-cyano-3-phenoxy-benzyl, was observed in the field in Zambia to offer a better residual effect against adult Rhipicephalus appendiculatus of up to 7 days post-treatment during a high infestation pressure period than on organophosphorus (OP) acaricide. A group of 20 cattle sprayed with deltamethrin wash of approximately 0.005 w/v at 14 days intervals carried an average of less than 12 ticks per head by the 7th day post-treatment, whereas two groups of 20 cattle each, dipped weekly in an OP at 0.05% w/v had an average of over 60 ticks per head. In a theileriosis infected area 14 days' treatment with deltamethrin would probably be unsuitable for disease control during high infestation period, but 7–10 days would probably yield better results than those likely to be obtained with OPs.