Browsing by Author "Ngumi, P.N."
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Item Cross-immunity studies using Kenyan stocks of Cowdria ruminantium(1966) Rumberia, R.M.; Ngumi, P.N.; Mbogoh, S.K.; Kariuki, D.P.; Gitau, P.K.; KARI (National Veterinary Research Centre Muguga)Heart water or cowdriaosis, caused by the rickettsia organism Cowdria ruminantium, is a disease of major economic importance in sub-Saharan Africa (Ui1enberg 1983). The disease affects domestic and wild ruminants and is transmitted trans-stadially by ticks of the genus Amblyomma. The disease is controlled by control of vector ticks through use of acaricides, treatment of sick animals or by vaccination using an infection and treatment method. The first practical vaccination approach was investigated by Neitz and Alexander (1941) using Cowdria infected sheep blood. The infection and treatment method is used because animals that recover from clinical disease are usually resistant to homologous and in most cases to heterologous challenge (Uilenberg et al 1983). There are however, same shortcomings with this method.Item Estimating seroprevalence and variation to four tick-borne infections and determination of associated risk factors in cattle under traditional mixed farming system in Mbeere District, Kenya(2010) Gachohi, J.M.; Ngumi, P.N.; Kitala, P.M.; Skilton, R.A,; International Livestock Research Institute (ILRI), Old Naivasha Rd, Kabete, P.O. Box 30709-00100, Nairobi, Kenya, Kenya Agricultural Research Institute, Trypanosomiasis Research Center, Muguga, P.O. Box 362-00902, Kikuyu, Kenya, Department of Public Health, Pharmacology and Toxicology, College of Agriculture and Veterinary Sciences, University of Nairobi, P.O. Box 29053-00625, Nairobi, Kenya, Biosciences Eastern and Central Africa (BecA) – ILRI Hub, Old Naivasha Rd, Kabete, P.O. Box 30709-00100, Nairobi, KenyaA cross-sectional study of serum antibody responses of cattle to tick-borne disease (TBO) parasites (Theileria parva. Theileria mutans. Anaplasma marginale and Babesia bigeminal was conducted on traditional smallholder mixed farms in Mbeere District in Kenya. The objective was to estimate the infections' seroprevalence and variation and identify associated risk factors. A total of 440 cattle in 80 farms, selected by stratified random sampling from the four divisions in the district, were surveyed. Information on animal and on each farm 's management practices, particularly on tick control practices, was obtained by personal interview using a standardized questionnaire. Prevalences of serum antibodies were determined using the enzyme-linked immunosorbent assay (ELISA) technique. The relationship between TBOs seroprevalence and the risk factors was assessed by multivariable analysis using standard logistic regression models and mixed models using the farm as a random effect. Overall estimation of seroprevalences and their 95% confidence limits were: T. parva (19% [14%. 25%)). T. mutans (25% [20%. 29%)). A. marginale (58% [52%. 64%)) and B. bigemina (19% [15%. 23%)). Analysis in presence of extra-binomial variation under Analysis Of Variance (ANOVA) yielded relatively larger intra-farm correlation coefficient (ICC) (0.3) and variance-inflation factor (VIF) (2.35) values for T. parva than for the other parasites [range. 0.05-0.07 (for ICC) and 1.02-1.32 (for VIF)]. Both farm- and area-level variables had variably significant and large effects on all infections, but these were more pronounced on T. parva seroprevalence. Inclusion offarm random effect resulted in substantially higher estimate of farm variance component for T. parva infection (1.73) compared to other infections [range. 0.29-0.56]. comparable ICC values with those under ANOVA analysis [range. 0.08-0.35] and a substantially better fit than the standard multivariable logistic regressions. The above results serve as possible indicators of existence of endemic instability for the studied TBO infections in the district. A probable differential ecological and climatic variability in vector suitability habitats, particularly for T. parva vector, was likely in Mbeere District and this was suggested to influence farm tick control management across the area. Implications of the design-based sampling and analyses on the above results are also discussed.Item Isolation of the Causative Agent of Heartwater (Cowdria ruminantium) from Three Amblyomma Species in Eight Districts of Kenya.(British Veterinary Association , 1997) Ngumi, P.N.; Rumberia, R.M.; Williamson, S.M.; Sumption, K.J.; Lesan, A.C.; Kariuki, D.P.; National Veterinary Research Centre; University of Edinburgh; 1.Centre for Tropical Veterinary Medicine, University of Edinburgh, Easter Bush, Roslin, Midlothian, EH25 9RG 2.National Veterinary Research Centre, Box 32, Kikuyu, KenyaThirteen isolates of Cowdria ruminantium were made from eight different Districts of Kenya by four different isolation methods. Feeding adult Amblyomma species ticks derived from nymphs collected in the field and the inoculation of homogenates prepared from adult field ticks had the highest success rate. The reattachment of adult ticks collected in the field was successful on only one of five attempts, and the subinoculation of blood from suspected heartwater carriers was unsuccessful. Seven of the isolates were derived from A variegatum ticks, four from A gemma, one from A lepidum and one from a mixed pool of the last two species. This is the first report of the isolation of C ruminantium from A gemma ticks, and the first report of its transtadial transmission from nymphal to adult A gemma.Item Responses to a vaccine trial for East Coast fever in two cattle herds at the Kenyan coast(1991) Mutugi, J.J.; Ndungu, S.G.; Linyonyi, A.; Maritim, A.C.; Mining, S.K.; Ngumi, P.N.; Kariuki, D.P.A total of 373 cattle (271 Zebu-European crosses and 102 pedigree Jerseys) were immunized against East Coast fever on two farms in the Kilifi District of Coast Province, Kenya. The cross breeds and the Jersey cattle received I ml of either 10-01 or 10-' dilution of Thellena parva parva Marikebuni stock, respectively and simultaneous treatment with a long-acting formulation of oxytetracycline. Following immunization, 362 cattle (96.5%) showed Theileria parva antibodies; 346 cattle (92.7%) seroconverted without clinical reactions. The Jersey cattle developed a higher proportion of clinical East Coast fever reactors (14.7%) following the immunization than the cross breeds (0.6%). All the calves immunized (37) on both farms seroconverted to Theileria parva antigen without any theilerial clinical reactions. The development of a serological response to East Coast fever was independent of the route of stabilate inoculation and was unaffected by concurrent infections such as trypanosomiasis and foot and mouth disease. Following immunization, no discernable effects on milk production were recorded, except from cattle undergoing a clinical reaction, where a transient reduction in milk production was seen. Thirty months later, the immunized cattle are reported to have withstood the disease challenge presented to them naturally on the farms without any breakdown in immunity to East Coast fever.
