Browsing by Author "Ledger, M.A."
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Item The Application of an Indirect Method of Infecting Ticks with Piroplasms for Use in the Isolation of Field Infections(1974) Cunninggham, M.P.; Purnel, R.E.; Ledger, M.A.; Irvin, A.D.; Brown, C.G.D.; Pyne, R.C.; East African Veterinary Research OrganizationNymphal R. appendiculatus ticks became infected with Theileria parva following the intraperitoneal inoculation of fresh or refrigerated infected bovine blood into rabbits on which the ticks were feeding. The method was successfully used in the isolation of field infections and as blood is the only material needed from such cases the method can be readily and conveniently applied in the isolation of different field strains of T. parva and possibly of similar blood-borne protozoal diseases.Item Attempted Transmission of Theileria gorgonis, Brocklesby & Vidler 1961, from Blue Wildebeest (Connochaetes taurinus) to Cattle(Tropenmed Parasitol, 1973) Purnell, R.E.; Schiemann, B.; Brown, C.G.; Irvin, A.D.; Ledger, M.A.; Payne, R.C.; Radley, D.E.; Young, A.S.; Immunological Research on Tick-borne Cattle Diseases and Tick Control Project; East African Veterinary Research Organisation, MugugaFour blue wildebeest (Connochaetes taurinus), two from the Serengeti National Park in Tanzania and two from the Athi/Kapiti Plains m Kenya, were splenectomied. Of the two wildebeest from Tanzania, one which had previously had detectable intra-erythrocytic piroplasms of Theileria gorgonis, had an increase in parasitaemia to a peak of 7%, the other, which had previously had no detectable parasites, developed a low-level parasitaemia. The two wildebeest from Kenya had severely exacerbated T. gorgonis infections all in one case a concomitant Anaplasma marginale infection They died of severe anaemia after febrile responses and theilenal parasitaemias in excess of 70%. Attempts to transmit T. gorgonis to spienectomised calves by blood passage and to steer~ via Rhipicephalus appendiculatus ticks failed despite the establishment of the parasite in the ticks. A. marginale, on the other hand, was blood-passaged to two of the splenectomised calves, which were inoculated with blood from the infected wildebeest.Item Attempted Transmission of Theileria Gorgonis, Brocklesby & Vidler 1961, From Blue Wildebeest (Connochaetes Taurinus) to Cattle(1973) Purnell, R.E.; Schiemann, B.; Brown, C.G.D.; Irvin, A.D.; Ledger, M.A.; Payne, R.C.; Young, A.S.; East African Veterinary Research Organization, Muguga, KenyaTwo blue wildebeest (Connochaetes taurinus) from the Serengeti National Park in Tanzania and two from Kenya were splenectomised. Of the two from Tanzania, one that had previously had detectable intra-erythrocytic piroplasms of Theileria gorgonis showed an increase in parasitaemia (percentage of erythrocytes infected) to 7%, and the other, which had had no detectable parasites, developed a low-level parasitaemia. The two animals from Kenya had severely exacerbated infections with T. gorgonis and in one case a concomitant infection with Anaplasma marginale. They developed Theileria parasitaemias of more than 70% and died. Attempts to transmit T. gorgonis to steers by means of adults of Rhipicephalus appendiculatus Neum. that had fed as nymphs on infected wildebeest were unsuccessful, although it was shown that the parasite became established in the ticks. Some 500 ticks were used on each steer.Item The "Black Rot" Condition in Pyrethrum in Tanzania-Nematological Investigations(1967) Schoemaker, R.L.P.W.; Ledger, M.A. ; E.A.A.F.R.O., Kikuyu, KenyaAn experiment is described in which pyrethrum and chrysanthemum plants were inoculated with chrysanthemum leaf eelworm (Apltelenchoides ritzemabosi). After II weeks only one Aphelenclzoides specimen was recovered from pyrethrum, while a dense population was present on chrysanthemum. This result proves that pyrethrum is not a suitable host for the chrysanthemum leaf eelworm.Item East Coast Fever: 60Co-Irradiation of Theileria Parva in Its Tick Vector, Rhipicephalus Appendiculatus(1974) Purnell, R.E.; Brown, C.G.D.; Burridge, M.J.; Cunningham, M.P.; Emu, H.; Irvin, A.D.; Ledger, M.A.; Njuguna, L.M.; Payne, R.C.; Radley, D.E.; East African Veterinary Research Organization, Muguga P.O. Box 32, Kikuyu, KenyaThree experiments were carried out in which Theileria parva was irradiated in its tick vector, Rhipicephalus appendiculatus. In the first experiment, infected unfed adult ticks were irradiated at doubling doses from 4 to 32 krad. Some of the ticks were then fed for 4, 5, 6, 7 and 8 days on rabbits, and the parasites in their salivary glands examined. Five male and 5 female ticks from each irradiation dose were put onto each of a pair of susceptible cattle, whose reactions were recorded. Increasing doses of irradiation resulted in progressive destruction of the parasites. All cattle receiving ticks irradiated at doses up to and including 16 krad died of East Coast fever (ECF), and one of the cattle receiving ticks irradiated at 32 krad died.Item East Coast fever: correlation between the morphology and infectivity of Theileria parva developing in its tick vector(1973) Purnell, R.E.; Brown, C.G.D.; Cunningham, M.P.; Burridge, M.J.; Kirimi, L.M.; Ledger, M.A.Rhipicephalus appendiculatus ticks, infected with Theileria parva, were fed on rabbits and removed at daily intervals for 9 days. Half of the ticks removed were dissected and their salivary glands processed and examined for parasites. The remaining ticks which had been removed were ground up and aliquots of the supernatant fluid thus obtained were injected into East Coast fever susceptible cattle. Cattle injected with supernatant fluids from ticks fed for 4-9 days became infected, and this could be correlated with the histological detection of mature parasites in the corresponding ticks. The most highly ineffective supernatant fluids were prepared from 5-day-fed ticks. In a second experiment it was shown that female ticks of a variety of weights contained ineffective particles of T.parva.Item The Rate of Growth and the Efficiency of Food Conversion in Various Breeds of Poultry(1956/1957) French, M.H.; Ledger, M.A.1. Breeds of poultry, imported as day-olds can grow at Muguga (6,800 ft.) at rates which are very little different from those secured in temperate zones. 2. The efficiency of food conversion for such birds is also little different from those reported from the temperate latitudes. 3. The amount of food Consumed per lb. of Iive-weight increase rises sharply from 14-16 weeks of age for the North Holland Blue, Brown Leghorn and Cambar and WeI summer breeds. 4. For Aylesbury ducklings and Roman geese a decreased gross efficiency of food conversion commences at an earlier age than with chickens and suggests that ducklings should be sold when not older than 14 weeks and that well fed gooslings are better sold when 12-13 weeks old.Item Studies on Theileria Parva in Whole-Body Irradiated Mice(1973) Irvin, A.D.; Brown, C.G.D.; Cunningham, M.P.; Crawford, J.G.; Ledger, M.A.; East African Veterinary Research Organization, Kabete, Nairobi (KenyaTheileria parva, the causative agent of East Coast fever (E. C. F.) of cattle, has never been grown successfully in small laboratory animals, and the only animals of proven susceptibility are cattle and two species of buffalo (Syncerus caffer and Bubalus bubalis). A number of workers have made unsuccessful attempts to establish T. parva in a variety of animals including rabbits, mice, guinea-pigs, hamsters, rats, hyraxes and chick embryos [1-4]. The failures encountered by these earlier workers can be partly attributed to lack of suitable infective material, and partly to host resistance. We have attempted to overcome these problems, firstly by using a source of material. of known high infectivity for cattle, i.e. T. parva macro schizont-infected bovine lymphoid cells in tissue culture (5), and secondly by reducing the host response using whole-body irradiation.Item Theileria Parva: Variation in the Infection Rate of the Vector Tick, Rhipicephalus Appendiculatus(1974) Purnell, R.E.; Ledger, M.A.; Omwoyo, P.L.; Payne, R.C.; Peirce, M.A.; East African Veterinary Research Organization, P,O, Box 32, Kikuyu, KenyaThe variation in Theileria parva infection rates of experimental batches of adult Rhipicephalus appendiculatus ticks, used during the course of several years, was examined. It was found that considerable variation occurred, but that this could not always be correlated with the piroplasm parasitaemia in the cattle on which the ticks engorged as nymphs. Statistical analysis showed that the infection rate of ticks fed on cattle with a parasitaemia of 41–50 per cent was significantly higher than that of ticks fed on cattle with lower parasitaemias. A number of experiments were then carried out in which one or several factors of this aspect of the host-parasite relationship remained constant whilst others were altered. None of these factors was seen to play a major part in the variation. Finally, randomly selected groups of 10 ticks which had dropped engorged as nymphs from the same animal on the same day were examined. The variation observed even in these groups was so great that it was concluded that the infection rate could depend on a factor such as the juxtaposition of possibly-infected gut epithelial cells and developing salivary glands during the nymphal moult.
