Browsing by Author "Picozzi, Kim"

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    Bayesian Geostatistical Analysis and Prediction of Rhodesian Human African Trypanosomiasis
    (PLoS, 2010) Wardrop, Nicola A.; Atkinson, Peter M.; Gething, Peter W.; Fèvre, Eric M.; Picozzi, Kim; Kakembo, Abbas S. L.; Welburn, Susan C.
    The persistent spread of Rhodesian human African trypanosomiasis (HAT) in Uganda in recent years has increased concerns of a potential overlap with the Gambian form of the disease. Recent research has aimed to increase the evidence base for targeting control measures by focusing on the environmental and climatic factors that control the spatial distribution of the disease. One recent study used simple logistic regression methods to explore the relationship between prevalence of Rhodesian HAT and several social, environmental and climatic variables in two of the most recently affected districts of Uganda, and suggested the disease had spread into the study area due to the movement of infected, untreated livestock. Here we extend this study to account for spatial autocorrelation, incorporate uncertainty in input data and model parameters and undertake predictive mapping for risk of high HAT prevalence in future. Using a spatial analysis in which a generalised linear geostatistical model is used in a Bayesian framework to account explicitly for spatial autocorrelation and incorporate uncertainty in input data and model parameters we are able to demonstrate a more rigorous analytical approach, potentially resulting in more accurate parameter and significance estimates and increased predictive accuracy, thereby allowing an assessment of the validity of the livestock movement hypothesis given more robust parameter estimation and appropriate assessment of covariate effects. Analysis strongly supports the theory that Rhodesian HAT was imported to the study area via the movement of untreated, infected livestock from endemic areas. The confounding effect of health care accessibility on the spatial distribution of Rhodesian HAT and the linkages between the disease’s distribution and minimum land surface temperature have also been confirmed via the application of these methods. Predictive mapping indicates an increased risk of high HAT prevalence in the future in areas surrounding livestock markets, demonstrating the importance of livestock trading for continuing disease spread. Adherence to government policy to treat livestock at the point of sale is essential to prevent the spread of sleeping sickness in Uganda.
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    Cattle movements and trypanosomes
    (Parasites & Vectors, 2013) Selby, Richard; Bardosh, Kevin; Picozzi, Kim; Waiswa, Charles; Welburn, Susan C.
    Background: The northwards spread of acute T. b. rhodesiense sleeping sickness in Uganda has been linked to cattle movements associated with restocking following the end to military conflict in 2006. This study examined the number of cattle traded from T. b. rhodesiense endemic districts, the prevalence of the parasite in cattle being traded and the level of trypanocidal treatment at livestock markets. Methods: Between 2008 and 2009 interviews were carried out with government veterinarians from 20 districts in Uganda, 18 restocking organizations and numerous livestock traders and veterinarians. Direct observations, a review of movement permit records (2006 to 2008) and blood sampling of cattle (n = 1758) for detection of parasites were also conducted at 10 livestock markets in T. b. rhodesiense endemic districts. Results: Records available from 8 out of 47 identified markets showed that 39.5% (5,238/13,267) of the inter-district cattle trade between mid-2006 and mid-2008 involved movement from endemic areas to pathogen-free districts. PCR analysis showed a prevalence of 17.5% T. brucei s.l. (n = 307/1758 [95% CI: 15.7-19.2]) and 1.5% T. b. rhodesiense (n = 26/1758 [95% CI: 0.9-2.0]) from these same markets. In a two-year period, between late-2006 to late-2008, an estimated 72,321 to 86,785 cattle (57, 857 by 18 restocking organizations and 10,214 to 24,679 by private traders) were imported into seven pathogen-free northern districts, including districts that were endemic for T. b. gambiense. Between 281 and 1,302 of these cattle were likely to have carried T. b. rhodesiense. While governmental organizations predominantly adhered to trypanocidal treatment, most Non-Governmental Organization (NGOs) and private traders did not. Inadequate market infrastructure, poor awareness, the need for payment for drug treatments, and the difficulty in enforcing a policy of treatment at point of sale contributed to non-compliance. Conclusion: With increasing private trade, preventing the spread of Rhodesian sleeping sickness in Uganda requires government support to ensure mandatory trypanocidal treatment at livestock markets, investment in market infrastructure and possible drug subsidy. Mapping the northern reaches of T. b. rhodesiense in livestock and preparation of risk assessments for cattle trading could mitigate future outbreaks.
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    Evaluating the impact of targeting livestock for the prevention of human and animal trypanosomiasis, at village level, in districts newly affected with T. b. rhodesiense in Uganda
    (Infectious Diseases of Poverty, 2017) Hamill, Louise; Picozzi, Kim; Fyfe, Jenna; Wissmann, Beatrix von; Wastling, Sally; Wardrop, Nicola; Selby, Richard; Acup, Christine Amongi; Bardosh, Kevin L.; Muhanguzi, Dennis; Kabasa, John D.; Waiswa, Charles
    Background: Uganda has suffered from a series of epidemics of Human African Trypanosomiasis (HAT), a tsetse transmitted disease, also known as sleeping sickness. The area affected by acute Trypanosoma brucei rhodesiense HAT (rHAT) has been expanding, driven by importation of infected cattle into regions previously free of the disease. These regions are also affected by African Animal Trypanosomiasis (AAT) demanding a strategy for integrated disease control. Methods: In 2008, the Public Private Partnership, Stamp Out Sleeping Sickness (SOS) administered a single dose of trypanocide to 31 486 head of cattle in 29 parishes in Dokolo and Kaberamaido districts. This study examines the impact of this intervention on the prevalence of rHAT and AAT trypanosomes in cattle from villages that had (HAT +ve) or had not (HAT-ve) experienced a recent case of rHAT. Cattle herds from 20 villages were sampled and screened by PCR, pre-intervention and 6-months post-intervention, for the presence or absence of: Trypanosoma brucei s.l.; human infective T. b. rhodesiense; Trypanosoma vivax;andTrypanosoma congolense savannah. Results: Post-intervention, there was a significant decrease in the prevalence of T. brucei s.l. and the human infective sub-species T. b. rhodesiense in village cattle across all 20 villages. The prevalence of T. b. rhodesiense was reduced from 2.4% to 0.74% (P<0.0001), with the intervention showing greater impact in HAT-ve villages. The number of villages containing cattle harbouring human infective parasites decreased from 15/20 to 8/20, with T. b. rhodesiense infection mainly persisting within cattle in HAT+ve villages (six/eight). The proportion of T. brucei s.l. infections identified as human infective T. b. rhodesiense decreased after the intervention from 8.3% (95% CI=11.1–5.9%) to 4.1% (95% CI=6. 8–2.3%). Villages that had experienced a recent human case (HAT+ve villages) showed a significantly higher prevalence for AAT both pre- and post-intervention. For AAT the prevalence of T. vivax was significantly reduced from 5.9% to 0. 05% post-intervention while the prevalence of T. congolense increased from 8.0% to 12.2%. Conclusions: The intervention resulted in a significant decrease in the prevalence of T. brucei s.l., human infective T. b. rhodesiense and T. vivax infection in village cattle herds. The proportion of T. brucei s.l. that were human infective, decreased from 1:12T. brucei s.l. infections before the intervention to 1:33 post-intervention. It is clearly more difficult to eliminate T. b. rhodesiense from cattle in villages that have experienced a human case. Evidence of elevated levels of AAT in livestock within village herds is a useful indicator of risk for rHAT in Uganda. Integrated veterinary and medical surveillance is key to successful control of zoonotic rHAT.
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    LAMP for Human African Trypanosomiasis: A Comparative Study of Detection Formats
    (PLoS Neglected Tropical Diseases, 2010) Wastling, Sally L.; Picozzi, Kim; Kakembo, Abbas S. L.; Welburn, Susan C.
    Loop-mediated isothermal amplification (LAMP) is at the forefront of the search for innovative diagnostics for human African trypanosomiasis (HAT). Several simple endpoint detection methods have been developed for LAMP and here we compare four of these: (i) visualization of turbidity; (ii) addition of hydroxynaphthol blue before incubation; (iii) addition of calcein with MnCl2 before incubation and (iv) addition of Quant-iT PicoGreen after incubation. These four methods were applied to four LAMP assays for the detection of human African trypanosomiasis, including two Trypanozoon specific and two Trypanosoma brucei rhodesiense specific reactions using DNA extracted from cryo-preserved procyclic form T. b. rhodesiense. A multi-observer study was performed to assess inter-observer reliability of two of these methods: hydroxynapthol blue and calcein with MnCl2, using DNA prepared from blood samples stored on Whatman FTA cards. Results showed that hydroxynaphthol blue was the best of the compared methods for easy, inexpensive, accurate and reliable interpretation of LAMP assays for HAT. Hydroxynapthol blue generates a violet to sky blue colour change that was easy to see and was consistently interpreted by independent observers. Visible turbidity detection is not possible for all currently available HAT LAMP reactions; Quant-iT PicoGreen is expensive and addition of calcein with MnCl2 adversely affects reaction sensitivity and was unpopular with several observers.
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    Spatial Predictions of Rhodesian Human African Trypanosomiasis (Sleeping Sickness) Prevalence in Kaberamaido and Dokolo, Two Newly Affected Districts of Uganda
    (PLoS neglected tropical diseases, 2009) Batchelor, Nicola A.; Atkinson, Peter M.; Gething, Peter W.; Picozzi, Kim; Fe`vre, Eric M.; Kakembo, Abbas S. L.; Welburn, Susan C.
    The continued northwards spread of Rhodesian sleeping sickness or Human African Trypanosomiasis (HAT) within Uganda is raising concerns of overlap with the Gambian form of the disease. Disease convergence would result in compromised diagnosis and treatment for HAT. Spatial determinants for HAT are poorly understood across small areas. This study examines the relationships between Rhodesian HAT and several environmental, climatic and social factors in two newly affected districts, Kaberamaido and Dokolo. A one-step logistic regression analysis of HAT prevalence and a two-step logistic regression method permitted separate analysis of both HAT occurrence and HAT prevalence. Both the occurrence and prevalence of HAT were negatively correlated with distance to the closest livestock market in all models. The significance of distance to the closest livestock market strongly indicates that HAT may have been introduced to this previously unaffected area via the movement of infected, untreated livestock from endemic areas. This illustrates the importance of the animal reservoir in disease transmission, and highlights the need for trypanosomiasis control in livestock and the stringent implementation of regulations requiring the treatment of cattle prior to sale at livestock markets to prevent any further spread of Rhodesian HAT within Uganda.