Browsing by Author "Ngaira, J.M."
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Item Animal-level risk factors for Trypanosoma evansi Infection in camels in Eastern and Central parts of Kenya(2002) Ngaira, J.M. ; Bett, B.; Karanja, S.M.; Kenya Trypanosomiasis Research Institute; Kenya Trypanosomiasis Research Institute, P.O. Box 362, KikuyuPoint prevalence and animal-level risk factors for Trypanosoma evansi Infection were investigated in a cross-sectional study that involved 2 227 camels from eastern and central parts of Kenya. The screening tests used were haematocrit centrifugation technique (HCT), mouse inoculation and latex agglutination (Suratex®). All camels were screened with HCT, while 396 and 961 of them were, in Addition, screened with mouse inoculation and SurateX tests, respectively. Parasitological and Suratex® test results were used in parallel to determine the number of camels exposed to T. evansi infections. Statistical analyses were conducted using Statistical Analysis Systems. Parasitological and Suratex® test results in parallel were dependent variables in multivariable logistic regression models that determined risk factors for T. evansi infection. Herd-level clustering was corrected with general estimation equations. The prevalence were 2.3 % and 19.6 %, using parasitological and Suratex tests, respectively, and 21.7 % when both tests were used in parallel. There was a Positive association between the screening tests (McNemar's test = 104.8, P = 0.001) although the strength of association was low (Kappa = 0.2; 95 % CI: 0.1- 0.3). Before accounting for herd-level clustering, dry season (OR = 1.5; 95 % CI: 1.0, 2.1) and nomadic pastoralism (OR = 1.8; 95 % CI: 1.1, 3.2) were associated with increased odds of a camel being exposed to T. evansi infection compared to wet season and ranching, respectively. Following this correction, only nomadic pastoralism was significantly associated (OR = 3.1; 95 % CI = 1.0, 14.4) with T. evansi infection compared to ranching. It is concluded that camels managed under nomadic pastoralism had higher risk of being exposed to T. evansi infections than camels from ranching systems of management.Item Evaluation of Antigen and Antibody Rapid Detection Tests for Trypanosoma Evansi Infection in Camels in Kenya(2003) Ngaira, J.M.; Bett, B.; Karanja, S.M.; Njagi, E.N.M.; Kenya Trypanosomiasis Research Institute; Lavington, Code 00603, P.O. Box 25530, Code 00603, Nairobi, Kenya, Kenya Trypanosomiasis Research Institute, P.O. Box 362, Kikuyu, Kenya, Department of Biochemistry, Kenyatta University, P.O. Box 43844, Nairobi, KenyaThe card agglutination test for Trypanosoma evansi (CATTIT. evansi) for the detection of antibodies, and Suratex® for the detection of circulating antigens were compared in a cross-sectional study involving camels in eastern and central parts of Kenya. Of the 2227 camels screened, 2038 were owned by nomadic pastoralists in T. evansi endemic areas in eastern Kenya. A herd of 86 camels were from a ranch in Mugwoni. In Athi River area, 35 camels belonged to Kenya Trypanosomiasis Research Institute, and 68 were slaughter animals. Diagnostic sensitivity estimates were obtained by testing sera from 51 camels that had been found to be parasitologically positive by the haematocrit centrifugation technique, buffy-coat technique and mouse inoculation. Diagnostic specificity was estimated by testing sera from 35 camels known to be trypanosome-free. Positive and negative predictive values (NPVs) were calculated using a range of prevalence values. The sensitivity of CATT/T. evansi (68.6%) was higher than that of Suratex® (58.8%), but not significantly. Both tests had equally high specificity (100%). The overall prevalence was 2.3% (51 out of 2227) by parasite detection, 32.2% (327 out of 1017) by CATT/T. evansi and 19.6% (188 out of 961) by Suratex®. Overall, there was a positive association between CATT/T. evansi and Suratex® though the strength of association was low (McNemar's test = 46.12, P = 0.001; kappa = 0.26, CI: 0.20-0.33). Parasite prevalence ranged from 0% in several herds to 27.8% in a herd in Isiolo. Prevalence was highest in Isiolo with 2.5% (51 out of 2030) by parasitological detection, 38.8% (321 out of 828) by CATT/T. evansi and 21.9% (169 outof772) by Suratex®. In Mugwoni prevalence was 7 and 18% by CATT/T. evansi and Suratex®, respectively, and no parasites were detected. In Athi River Suratex® detected 2.9% (3 out of 103) positive while CATT/T. Evansi and parasitological methods gave negative results. At prevalence values between 10 and 100%, CATT/T. Evansi as well as Suratex® had infinitely high positive predictive values, whereas Suratex® had a lower NPV than CATT/T. Evansi.Item Use of TrypTectCIAA T to determine the effectiveness of treatment of Trypanosoma brucei r/lOdesiense infections in vervet monkeys (ChLorocebus aethiops) and man(2010) Karanja, S.M. ; Ngaira, J.M.; Thuita, J.K.; Ngotho, M.; Gichuki, C.W.; ; Kenya Trypanosomiasis Research Institute; Jomo Kenyatta University of Agriculture and Technology (JKUAT), Biochemistry, Kenya, Kenya Agricultural Research Institute, Trypanosomiasis Research Centre (KARI-TRC); UNDP/World Bank/WHOThe vervet monkey (Chlorocebus aethiops) model of sleeping sickness was used to evaluate the effectiveness of TrypTectCIATT in assessing the success of trypanocidal therapy. A retrospective study was therefore conducted on sera collected from monkeys infected with Trypanosoma brucei rhodesiense and treated either curatively with melarsoprol or sub-curatively with diminazene aceturate. In the human survey, 440 sera collected from 96 human patients were tested. These patients were treated with either surname or melarsoprol depending on the stage of the disease. An extra 56 parasitologically positive pre-treatment samples were also tested to aid in determination of the test sensitivity. Results indicated that between 21-28 days post-infection, the test detected trypanosomal antigens in 84.2% (16119) of animal samples that were parasitologically positive by the hematocnt centrifugation technique (RCT). In curatively treated animals, 77, 8% (7/9) exhibited positive reaction up to 9 months post-treatment. One animal was positive for trypanosomal antigens for the entire 12 months while one was a non-reactor from the sub-curatively treated group, 80% (8110) were detected positive for the entire 12 months while, 2 animals were non-reactors.In the human survey, 3 patterns of antigen profiles were observed. In some patients, there was fluctuation of antigen levels throughout the 12 months follow-up period. In others, antigens were detected for the entire 12 months but in decreasing levels. The last group was that of patients with antigens decreasing at different rates to undetectable levels at 12 months post-treatment. The presence of trypanosome positive but antigen negative samples during the study raises a few questions with regards to the sensitivity of the test. It is however evident that the test was able to detect trypanosomal antigens in over 80% of positive monkey and human serum samples. Consequently, TrypTectCIATT may be an important additional tool reduction of the follow-up period and determination of success of chemotherapy in sleeping sickness.
