Browsing by Author "Radley, D.E."
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Item Adaptation and Possible Attenuation of Theileria Parva-Infected Cells Grown in Irradiated Mice(1976) Irvin, A.D.; Brown, C.G.D.; Stagg, D.A.; Kanhai, G.K.; Kimber, C.D.; Radley, D.E.; East African Veterinary Research Organisation, Muguga, P.O. Box 32, Kikuyu, KenyaTheileria parva-infected bovine lymphoid cells were taken from 8 cattle immediately after death from East Coast fever (ECF). Cells were inoculated into groups of irradiated Swiss and athymic nude mice. Cells became established in one group of Swiss mice and 2 groups of athymic mice. Development of cells in mice only occurred if cells concurrently established in culture; when establishment in culture was delayed, cells failed to develop in mice. Cells from one of the isolates in athymic mice were passaged 6 times through further mice. On inoculation of these mouse-passaged cells into cattle, the animals underwent mild reactions and subsequently resisted a lethal ECF challenge. The possibility of vaccinating cattle against ECF by means of mouse passaged cells merits further study.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 East Coast Fever: 3. Chemoprophylactic Immunization of Cattle using Oxytetracycline and a Combination of Theilerial Strains(1975) Radley, D.E.; Brown, C.G.D.; Cunningham, M.P.; Kimber, C.D.; Musisi, F.L.; Payne, R.C.; Purnell, R.E.; Stagg, S.M.; Young, A.S.; East African Veterinary Research Organization, Kikuyu Kenya,In the first of two experiments performed, 29 animals were immunized by chemoprophylaxis against either a combination of three theilerial strains, Theileria parva (Muguga), T. parva (Kiambu 5) and T. lawrencei (Serengeti transformed), or against one or two elements of the combination separately, and then challenged with either T. parva (Kiambu 1) or T. lawrencei (Solio KB1), both of which were known to be heterologous to T. parva (Muguga). The animals immunized against the combination had mild or inapparent reactions to challenge, whilst the susceptible control cattle and many of those immunized against one or two strains either had severe reactions of died. In the second experiment, 17 cattle immunized by chemoprophylaxis against the combination were challenged with lethal doses of three theilerial strains, T. parva (Entebbe 1), T. parva (Entebbe 2) and T. parva (Ukunda), recently isolated from two widely separated areas of East Africa. They had mild or inapparent reactions whilst 13 of 15 susceptible control cattle died. Chemoprophylaxis using a combination of theilerial strains and a limited oxytetracycline regimen was shown to be an effective means of immunizing cattle against East African theilerioses. The use of this technique as a method of immunizing cattle before exposure in the field is proposed.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: Challenge if Immunised Cattle by Prolonged Exposure to Infected Ticks(1975) Radley, D.E.; Brown, C.G.D.; Cunnigham, M.P.; Kimber, C.D.; Musisi, F.L.; Purnell, R.E.; Stagg, S.M.; East African Veterinary Research Organization, Muguga, PO Box 32, Kikuyu, KenyaBos taurus steers, previously treated with acaricide but washed before the trial commenced, were introduced sequentially to a paddock with a high level of T. parva infected ticks. The 12 animals exhibited macroschizonts in lymph nodes at 7-12 days, a febrile response at 9-13 days, and died at 14-21 days. Tick counts were highest on ears (the maximum level was 330), and the build-up of tick attachment correlated with time to death. Four steers immunized three months previously with tick-derived T. parva stabilate material plus Terramycin ECF were kept in the paddock throughout the experiment (60 days). Prepatent period was 10-15 days, but despite high levels of tick attachment (peaks of 500 on ears), there were minimal symptoms and only a slight transient rise in antibody titre on day 40. A few macroschizonts were detected in lymph nodes during the first week of infection and they reappeared from days 34-38. A few piroplasms were seen intermittently in blood smears.Item Further Studies on the Immunization of Cattle against Theileria La Wrencei by Infection and Chemoprophylaxis(Elsevier, 1979) Radley, D.E.; Young, A.S.; Grootenhuis, J.G.; Cunningham, M.P.; Dolan, T.T.; Morzaria, S.P.; Veterinary Research Department, Kenya Agricultural Research Institute, Muguga; Veterinary Laboratories, Kabete (Kenya); International Centre for Insect Physiology and Ecology, Kenya; MAFF Central Veterinary Laboratories, Great Britain.Three experiments were carried out to ascertain the feasibility of immunization of cattle against Theileria lawrencei using infection and chemoprophylaxis. In the first two experiments, cattle were immunized with a combination of three theilerial strains (‘cocktail’) and simultaneous treatment with an experimental formulation of oxytetracycline. When groups of these immunized cattle were challenged with stabilates of T. lawrencei isolated from African buffalo captured in Kenya and Tanzania, many of the immunized cattle had severe reactions and 3 out of 20 died, as did 18 of the 20 controls. A paddock containing carrier buffalo which maintained a population of Rhipicephalus appendiculatus continuously infected with T. lawrencei, was used in a second and third experiments. Cocktail immunized and control cattle were exposed to this tick challenge, and 55% of the immunized animals and 91% of the controls died. The protection provided by cocktail immunization was compared with immunization using different isolates of T. lawrencei from the buffalo paddock, but little difference in the degree of protection was detected. However, a high degree of immunity was observed when cocktail immunized cattle which had undergone a T. lawrencei stabilate challenge were exposed in the paddock. Only mild reactions were seen and no deaths occurred. Field immunization of cattle against T. lawrencei may be difficult due to immunovariants of this parasite emanating from the buffalo populations.Item A Note on the Susceptibility of Sheep and Goats to East Coast Fever(1974) Purnell, R.E.; Radley, D.E.; Cunningham, M.P.; East African Veterinary Research Organisation, P.O Box 32, Kikuyu, Kenya.In East Africa, where cattle, sheep and goats are commonly herded together, all three are regularly infested with Rhipicephalus appendiculatus ticks (Yeoman, 1966), the vectors of East Coast fever of cattle. Sheep and goats, while they are known to be susceptible to other species of Theileria (T. ovis and T. hirci) in various parts of the world, have never been shown to be infected with T. parva, the causative organism of East Coast fever, although there has always been speculation as to their potential ability to act as reservoirs of the parasite. Since we now have a number of low temperatures preserved stabilates of T. parva (Muguga) in this laboratory (Cunningham, Brown, et al, 1973), we decided to attempt to infect a new-born lamb and a new-born kid using relatively massive doses of T. parva infective material. A pregnant sheep and a pregnant goat, both of local native breed, were obtained. The sheep was shown to harbour occasional intra-erythrocytic piroplasms morphologically identified as T. ovis, whilst the goat apparently had no intra-erythrocytic parasites. Four hours after birth, the lamb was bled for serology and then inoculated subcutaneously in front of the right. Supported by a grant from the Pfizer Corporation, New York. shoulder with 10 ml of T. parva (Muguga) stabilate, two control cattle each receiving 1 ml of the stabilate. The kid was similarly bled and innoculated 23 hours after birth. Five cattle, which acted as controls on the infectivity of the stabilate inoculated into the kid, had each received 1 ml of the stabilate the previous week. The viability of the stabilate was also confirmed 11 weeks later when five cattle were each fatally infected by the inoculation of 1 ml. The rectal temperature of each animal was recorded daily. Giemsa-stained biopsy smears from the local drainage prescapular lymph nodes were examined daily after inoculation, and Giemsa-stained blood smears examined from the 10th day after inoculation, for the following month. Although local drainage lymph nodes of both animals, particularly that of the lamb, became hyperplastic and enlarged, no theilerial parasites were observed in the nodes or in the blood. All control cattle, except one which died of intercurrent disease, died of East Coast fever. Comparison of pre-inoculation and 28 days post inoculation serum samples, using the indirect fluorescent antibody test with a bovine conjugate (Burridge and Kimber, 1973), revealed no antibody response to T. parva antigens in the lamb or the kid. We conclude therefore, that neither animal was susceptible to infection with T. parva (Muguga) even when challenged with a dose of infective material much greater than they would encounter in an ECF enzootic area.Item A Pathogenic Theilerial Syndrome Of Cattle In The Narok District Of kenya(1972) Irvin, A.D.; Brown, C.G.D.; Burridge, M.J.; Cunningham, M.P.; Musoke, A.J.; Pierce, M.A.; Radley, D.E.Two theilerial parasites, pathogenic for cattle, were isolated during a field trial conducted at Aitong in the Narok District of Kenya. In a series of laboratory experiments the first of these parasites was successfully transmitted to all of 18 cattle by syringe inoculation of piroplasm infected blood. Two lines were established which were passaged 5 and 3 times respectively_ The animals inoculated all underwent a haemolytic syndrome with anaemia and jaundice and 5 of them died. Macro- and microschizonts were seen in only one of these 18 animals, but piroplasms were present in large numbers. Animals which had recovered from infection and were challenged with Theileria parva all died and there was no evidence that previous infection had conferred any protection on them. This infection was not transmitted by ticks.Item Theileria Parva: Comparative Infectivity of a Ground Tick Stabilate and a Classical 10-Tick Challenge(1973) Cunningham, M.; Brown, C.G.D.; Burridge, M.J.; Irvin, A.D.; Purnell, R.E.; Radley, D.E.; East African Veterinary Research Organisation, Muguga, P.O. Kabete, KenyaTwo groups of cattle, one ECF-sus-ceptible and the other ECF-recovered, were given East Coast fever challenges. The challenge was given either as a classical 10-tick challenge or by inoculation of a stabilate derived from the same batch of ticks. All susceptible animals died from both methods of challenge, with consistently uniform reactions in each case. Animals recovered from ECF consistently withstood challenge. Two reasons are given for preferring a stabilate challenge to a classical 10-tick challenge, namely reproducibility of uniformly lethal challenge over an extended period and the need for less strict confinement of the challenged animals.Item The use of Parasympathomimetic Drugs to Stimulate Salivation in the Tick Rhipicephalus Appendiculatus, and the Transmission of Theileria Parva using Saliva Obtained by this Method from Infected Ticks(1969) Purnell, R.E.; Branagan, D.; Radley, D.E.; East African Veterinary Research Organisation, P.O Box 32, Kikuyu, Kenya.Various parasympathomimetic drugs were injected per anus into female R. appendiculatus, previously fed for 5 days on rabbits, in attempts to induce the ticks to salivate. Pilocarpine nitrate and arecoline hydrobromide gave the best results and these drugs were therefore injected into ticks of various weight ranges and at various concentrations of the drug and the diluent, saline. The drugs were most effective at a concentration of 10% in 6 % sodium chloride solution. If ticks salivated, the amount of saliva they produced could be positively correlated with their weight. Sections of salivary glands from 5-day-fed female ticks in the corresponding weight ranges were examined for infection with T. parva. There appeared to be an inverse relationship between the infection rate of the ticks, and the number of infected acini observed, with increase in their weight. It was established that the greatest numbers of infective particles of T. parva should be obtained by the injection of 1 ul of 10% pilocarpine nitrate in 6 % sodium chloride solution into ticks weighing between and 13.0 mg. Twenty-five infected ticks in this weight range were injected, and the resultant saliva added to concentrated autologous leucocytes in phosphate-buffered saline before injection into a steer. The animal underwent a typical East Coast fever reaction and died, thus indicating that infective particles had been harvested by our methods.
