The importance of veterinary policy in preventing the emergence and re-emergence of zoonotic disease: examining the case of human african trypanosomiasis in Uganda

One Health policy for combatting African trypanocide resistance

The rise of African trypanocide resistance (ATr) is influenced by various factors such as evolutionary changes in the pathogen, the presence of resistance genes in the population, poor policy decisions, limited private-public partnerships to engage local communities, and insufficient funding for the development of new drugs over the past sixty years. These challenges have been exacerbated by the inadequate implementation of drug liberalization policies in the mid 20th century, leading to poor pharmacovigilance practices for veterinary drugs in low and middle income countries (LMICs). One health (OH), a disease management framework, provides practical solutions for addressing ATr, drawing on its success in managing previous epidemics like avian influenza in 2004 and the recent COVID-19 pandemic, where institutional collaborations were rapidly established. To combat ATr, OH initiatives involving both international and local partners at the policy and grassroots levels are crucial to generate community interest. The importance of political commitment, media involvement, and nongovernmental organizations cannot be overstated, as they are essential for resource mobilization and long-term sustainability in LMICs.

Experiences of the one-health approach by the Uganda Trypanosomiasis Control Council and its secretariat in the control of zoonotic sleeping sickness in Uganda

Elimination of sleeping sickness from endemic countries like Uganda is key if the affected communities are to exploit the potential of the available human and livestock resources (production and productivity). Trypanosoma brucei rhodesiense, the parasite that causes acute sleeping sickness in humans, is transmitted by tsetse flies and co-exists in non-human animal reservoirs. Uganda by Act of Parliament in 1992 decided to handle the complex approach to control of sleeping sickness and animal trypanosomiasis by establishing the Uganda Trypanosomiasis Control Council (UTCC) and its secretariat the Coordinating Office for the Control of Trypanosomiasis in Uganda (COCTU). The Institutional arrangement aimed to promote engagement with key stakeholders across nine key ministries and the community, all vital for control of zoonotic sleeping sickness, creating a One Health platform, long before such practice was common. From 2006, approaches by the Public Private Partnership, Stamp Out Sleeping Sickness (SOS) have required involvement of stakeholders in the promotion of insecticide treated cattle as live tsetse baits, targeting elimination of zoonotic sleeping sickness. Experiences in promoting sustainability of these interventions have been captured in this study as part of the Tackling Infections to Benefit Africa (TIBA) partnership. Meeting transcripts, focus group discussions and questionnaires were used to collect data from the different stakeholders involved in a rapid impact live bait study over 12 months from Dec 2017. The study provides unprecedented insights into the stakeholders involved in the application of a One health approach for control of zoonotic sleeping sickness across the most important active human African trypanosomiasis focus in East Africa. This unique study is fundamental in guiding multi-stakeholder engagement if the goal to eliminate zoonotic sleeping sickness is to be realised. A major challenge is timely feedback to the community as regards human and animal disease status; rapid diagnostic services that can be delivered from facilities established in close proximity to the affected communities and well equipped in-country reference laboratories are key to delivering effective control and best One Health Approach.

The elimination of Trypanosoma brucei gambiense? Challenges of reservoir hosts and transmission cycles: Expect the unexpected

The World Health Organisation has set the goal for elimination of Human African Trypanosomiasis (HAT), caused by Trypanosoma brucei gambiense (gHAT), as a public health problem for 2020 and for the total interruption of transmission to humans for 2030. Targeting human carriers and potential animal reservoir infections will be critical to achieving this ambitious goal. However, there is continuing debate regarding the significance of reservoir host animals, wild and domestic, in different epidemiological contexts, whilst the extent and duration of the asymptomatic human carrier state is similarly undefined. This paper reviews the status of the knowledge of latent infections in wild and domestic animal reservoir hosts towards the goal of better understanding their role in the transmission dynamic of the disease. Focus areas include the transmission cycles in non-human hosts, the infectivity of animal reservoirs to Glossina palpalis s.l., the longevity of infection and the stability of T. b. gambiense biological characteristics in antelopes and domestic animals. There is compelling evidence that T. b. gambiense can establish and persist in experimentally infected antelopes, pigs and dogs for a period of at least two years. In particular, metacyclic transmission of T. b. gambiense has been reported in antelope-G.p.palpalis-antelope and pig-G.p.gambiensis-pig cycles. Experimental studies demonstrate that the infectiveness of latent animal reservoir infections with T. b. gambiense is retained in animal-Glossina-animal cycles (antelopes and pigs) for periods of three years and human infectivity markers (human serum resistance, zymodeme, DNA) are stable in non-human hosts for the same period. These observations shed light on the epidemiological significance of animal reservoir hosts in specific ecosystems characterized by presently active, as well as known "old" HAT foci whilst challenging the concept of total elimination of all transmission by 2030. This target is also compromised by the existence of human asymptomatic carriers of T. b. gambiense often detected outside Africa after having lived outside tsetse infested areas for many years - sometimes decades. Non-tsetse modes of transmission may also play a significant but underestimated role in the maintenance of foci and also preclude the total elimination of transmission - these include mother to child transmission and sexual transmission. Both these modes of transmission have been the subject of case reports yet their frequency in African settings remains to be ascertained when the context of residual foci are discussed yet both challenge the concept of the possibility of the total elimination of transmission.

Monitoring the elimination of human African trypanosomiasis: Update to 2014

BACKGROUND

The World Health Organization (WHO) has targeted the elimination of Human African trypanosomiasis (HAT) 'as a public health problem' by 2020. The selected indicators of elimination should be monitored every two years, and we provide here a comprehensive update to 2014. The monitoring system is underpinned by the Atlas of HAT.

RESULTS

With 3,797 reported cases in 2014, the corresponding milestone (5,000 cases) was surpassed, and the 2020 global target of 'fewer than 2,000 reported cases per year' seems within reach. The areas where HAT is still a public health problem (i.e. > 1 HAT reported case per 10,000 people per year) have halved in less than a decade, and in 2014 they corresponded to 350 thousand km2. The number and potential coverage of fixed health facilities offering diagnosis and treatment for HAT has expanded, and approximately 1,000 are now operating in 23 endemic countries. The observed trends are supported by sustained surveillance and improved reporting.

DISCUSSION

HAT elimination appears to be on track. For gambiense HAT, still accounting for the vast majority of reported cases, progress continues unabated in a context of sustained intensity of screening activities. For rhodesiense HAT, a slow-down was observed in the last few years. Looking beyond the 2020 target, innovative tools and approaches will be increasingly needed. Coordination, through the WHO network for HAT elimination, will remain crucial to overcome the foreseeable and unforeseeable challenges that an elimination process will inevitably pose.

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

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; and Trypanosoma 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 1:12 T. 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.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0224-8) contains supplementary material, which is available to authorized users.

Revisiting zoonotic human African trypanosomiasis control in Uganda

OBJECTIVES

Human migration and concomitant HIV infections are likely to bring about major changes in the epidemiology of zoonotic parasitic infections. Human African trypanosomiasis (HAT) control is particularly fraught with intricacies. The primarily zoonotic form, T.b. rhodesiense, and the non-zoonotic T.b. gambiense co-exist in Northern Uganda, leading to a potential geographic and genetic overlap of the two foci. This region also has the highest HIV prevalence in Uganda plus poor food security. We examine the bottlenecks facing the control program in a changed political and economic context.

METHOD

We searched the literature in July 2015 using three databases: MEDLINE, Google Scholar, and Web of Science.

FINDINGS

Decentralized zoonotic HAT control for animal reservoirs and vectors compromise sustainability of the control programs. Human transmission potential may be underestimated in a region with other endemic diseases and where an HIV-HAT epidemic, could merge two strains.

CONCLUSION

Our comprehensive literature review concludes that enhanced collaboration is imperative not only between human and animal health specialists, but also with political science. Multi-sectorial collaborations may need to be nurtured within existing operational national HIV prevention frameworks, with an integrated surveillance framework.

Cost analysis of options for management of African Animal Trypanosomiasis using interventions targeted at cattle in Tororo District; south-eastern Uganda

Background

Tsetse-transmitted African trypanosomes cause both nagana (African animal Trypanosomiasis-AAT) and sleeping sickness (human African Trypanosomiasis - HAT) across Sub-Saharan Africa. Vector control and chemotherapy are the contemporary methods of tsetse and trypanosomiasis control in this region. In most African countries, including Uganda, veterinary services have been decentralised and privatised. As a result, livestock keepers meet the costs of most of these services. To be sustainable, AAT control programs need to tailor tsetse control to the inelastic budgets of resource-poor small scale farmers. To guide the process of tsetse and AAT control toolkit selection, that now, more than ever before, needs to optimise resources, the costs of different tsetse and trypanosomiasis control options need to be determined.

Methods

A detailed costing of the restricted application protocol (RAP) for African trypanosomiasis control in Tororo District was undertaken between June 2012 and December 2013. A full cost calculation approach was used; including all overheads, delivery costs, depreciation and netting out transfer payments to calculate the economic (societal) cost of the intervention. Calculations were undertaken in Microsoft Excel™ without incorporating probabilistic elements.

Results

The cost of delivering RAP to the project was US$ 6.89 per animal per year while that of 4 doses of a curative trypanocide per animal per year was US$ 5.69. However, effective tsetse control does not require the application of RAP to all animals. Protecting cattle from trypanosome infections by spraying 25 %, 50 % or 75 % of all cattle in a village costs US$ 1.72, 3.45 and 5.17 per animal per year respectively. Alternatively, a year of a single dose of curative or prophylactic trypanocide treatment plus 50 % RAP would cost US$ 4.87 and US$ 5.23 per animal per year. Pyrethroid insecticides and trypanocides cost 22.4 and 39.1 % of the cost of RAP and chemotherapy respectively.

Conclusions

Cost analyses of low cost tsetse control options should include full delivery costs since they constitute 77.6 % of all project costs. The relatively low cost of RAP for AAT control and its collateral impact on tick control make it an attractive option for livestock management by smallholder livestock keepers.