Livestock Network Analysis for Rhodesiense Human African Trypanosomiasis Control in Uganda

Abstract

Background: Infected cattle sourced from districts with established foci for Trypanosoma brucei rhodesiense human African trypanosomiasis (rHAT) migrating to previously unaffected districts, have resulted in a significant expansion of the disease in Uganda. This study explores livestock movement data to describe cattle trade network topology and assess the effects of disease control interventions on the transmission of rHAT infectiousness.Methods: Network analysis was used to generate a cattle trade network with livestock data which was collected from cattle traders (n = 197) and validated using random graph methods. Additionally, the cattle trade network was combined with a susceptible, infected, recovered (SIR) compartmental model to simulate spread of rHAT (Ro 1.287), hence regarded as “slow” pathogen, and evaluate the effects of disease interventions.Results: The cattle trade network exhibited a low clustering coefficient (0.5) with most cattle markets being weakly connected and a few being highly connected. Also, analysis of the cattle movement data revealed a core group comprising of cattle markets from both eastern (rHAT endemic) and northwest regions (rHAT unaffected area). Presence of a core group may result in rHAT spread to unaffected districts and occurrence of super spreader cattle market or markets in case of an outbreak. The key cattle markets that may be targeted for routine rHAT surveillance and control included Namutumba, Soroti, and Molo, all of which were in southeast Uganda. Using effective trypanosomiasis such as integrated cattle injection with trypanocides and spraying can sufficiently slow the spread of rHAT in the network.Conclusion: Cattle trade network analysis indicated a pathway along which T. b. rhodesiense could spread northward from eastern Uganda. Targeted T. b. rhodesiense surveillance and control in eastern Uganda, through enhanced public–private partnerships, would serve to limit its spread.

Analysis of patterns of livestock movements in the Cattle Corridor of Uganda for risk-based surveillance of infectious diseases

“…It was noteworthy that the networks based on district-todistrict movement of farm animals in the cattle corridor presented very similar structural properties to most other published animal movement networks, even though farming systems were different between countries and production types (15,21,34,48,49). Although the results did not include all districts in Uganda, they showed the value of such data for epidemiological studies in the country, given that most ruminants are farmed in the cattle corridor.…”

“…The Cattle Corridor covers about 35% of Uganda's land surface and diagonally stretches from southwestern to northeastern Uganda, with many semi-arid characteristics such as; low and unreliable rainfall, and prolonged drought dominated by pastoral rangelands (1,2). The region has in the present past experienced numerous outbreaks of foot-and-mouth disease (FMD), lumpy skin disease, contagious bovine pleuro-pneumonia in cattle; peste des petits ruminants, contagious caprine pleuro-pneumonia in small ruminants; African swine fever in pigs; trypanosomiasis, brucellosis and anthrax in all ruminants and pigs which has partly been fueled by direct animal movement (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15).…”

“…Therefore, failure to understand animal movement hinders formulation of specific control strategies in case of infectious animal disease outbreaks ( 19 , 20 ). The lack of animal movement data in Uganda has made it difficult to quantify key parameters for simulating potential disease transmission and hindered effective planning of control strategies for eradication of transboundary animal diseases (TADs) ( 15 , 21 ).…”

Identifying target areas for risk-based surveillance and control of transboundary animal diseases: a seasonal analysis of slaughter and live-trade cattle movements in Uganda

“…This seems to dispel the notion that livestock may be protected by vast geographical distances. Indeed, long-distance transmission events of TADs such as FMD and Tsetse-transmitted human African trypanosomiasis (hAT) have been reported in Uganda 14 , 54 – 56 .…”

“…Livestock supply peaks with optimal prices and better-quality cattle becoming available for sale, and this boosts wide-ranging livestock mobility, resulting in a continuous and pulsating livestock trade environment with epidemiological implications for the country-wide dynamics of TADs and other infectious diseases. Therefore, increased mid-year cattle traffic coincides with an anticipated rise on sales of mixed type cattle for breeding, ploughing, or re-stocking amongst large-scale ranches and agro-pastoral farmers along the cattle corridor, the pastoral Karamojong and the smallholder agro-pastoral communities in peripheral districts along the west and southeast 39 , 40 , 56 . In contrast, the end-of-year decline in cattle movements could be associated to escalating livestock prices and an increased sale of aged animals to be culled during the festive season 40 , 55 .Therefore, the seasonality observed at national level partially explains the variations of the active districts, trade links and volumes.…”