An exploration of novel approaches to improve surveillance for infectious diseases in rural poultry of Zambia using Newcastle Disease as a case study
Mubamba, Chrisborn (2018) An exploration of novel approaches to improve surveillance for infectious diseases in rural poultry of Zambia using Newcastle Disease as a case study. PhD thesis, James Cook University.
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Abstract
Poultry provides an important protein and revenue source for communities in tropical regions. Unfortunately, mechanisms for early detection of diseases in the rural poultry sector of developing countries like Zambia remain a challenge. Early detection of Newcastle Disease (ND) and other poultry diseases in domestic birds can reduce their spread. Understanding the status of priority poultry diseases like ND and movement of birds through trade will allow identification of disease and trade hotspots where frequent contact between birds can be expected and disease can be transmitted.
Consequently, ensemble modelling was used to identify disease and trade hotspots with the aim of utilising them for rapid poultry disease detection. The approach involved a hazard and risk assessment which identified priority diseases and high disease risk hotspots for the rural poultry sector within Eastern Zambia respectively. This was followed by implementation and assessment of community based syndromic surveillance using poultry clubs (PCs).
Newcastle Disease was identified as a priority disease. A retrospective study found that the disease followed a seasonal and cyclic pattern, with peaks in the hot dry season (Overall Seasonal Index 1.1) and had an estimated provincial incidence range of 0.16 to 1.7% per year, in eastern Zambia. Additionally, there were apparent spatial shifts in districts with outbreaks over time which could be because of veterinary interventions chasing outbreaks rather than implementing uniform control. When retrospective ND data was fitted to a predictive time series model, it showed an increasing trend in ND annual incidence over 25 years if existing interventions continue.
The seroprevalence of ND among indigenous chickens that were not vaccinated against ND in Eastern Zambia was 73% (95% confidence interval 59-94%). Group specific reverse transcription assays and full genome sequencing identified NDV sub-genotypes VIIh and XIII, which were first identified in Asia, to be among the circulating ND viruses in Eastern Zambia. These findings revealed how vulnerable countries like Zambia are to exotic poultry disease infections.
Descriptive and financial analysis of the rural poultry sector at the farm gate revealed that Poultry ranked highest in terms of popularity and numbers when compared with other animals kept by respondents (median=20). Gross margin analysis conducted using costing data from poultry farmers and expert opinion of extension workers revealed that indigenous chickens had the highest gross margin percentage (72%) compared to commercial broilers and layers which had gross margin percentages of 53% and 56% respectively. Breakeven analysis revealed that indigenous chickens required the lowest number of products to be sold (27) to realise profit compared to broilers (1011) and layers (873). The study further discusses how extension workers could utilise the weaknesses and strengths identified to initiate information sharing sessions with farmers that can arouse interest and ensure sustainable participation and implementation by farmers in sustainable disease extension programmes.
A study that conducted social network analysis and analysed poultry trading practices revealed that some farmers and traders sourced their poultry from neighbouring countries thus justifying the need for regional collaboration when conducting poultry disease surveillance. Trade of poultry and its products was at its peak in December and January and was associated with Christmas and New Year celebrations respectively, thus providing information when surveillance should be taking place. This was the first study that formally described poultry movement networks within Zambia and the surrounding region. Its findings provided data required for implementing targeted surveillance in regions where resources are either inadequate or non-existent.
A study that assessed the viability of syndromic data as a possible source for disease surveillance data found that farmers reported an overall annual disease incidence in rural poultry for eastern Zambia of 31% (90% CI 29-32%). On farm disease in poultry was associated with use of middlemen to purchase poultry products (p=0.05, OR=7.87), poultry products sold or given away from the farm (p=0.01, OR=1.92), farmers experiencing a period with more trade of poultry and its products (p=0.04, OR=1.70), presence of wild birds near the farm or village (p˂0.01, OR=2.47) and poultry diseases being reported from neighbouring farms or villages (p˂0.01, OR=3.12). The study also tentatively identified three poultry diseases (Newcastle Disease, Gumboro Disease and Fowl Pox) from the thirty-four disease syndromes provided by farmers. Farmers reported an incidence of 27% for Newcastle Disease in 2014. When compared with the state veterinary services data which reported Newcastle Disease incidence at 9% in 2014, it seems syndromic data obtained from farmers may be more sensitive in identifying disease incursion.
The efficiency of PCs was assessed by computing the proportion of meetings conducted by PCs compared to the actual meetings planned. Sustainability was assessed by comparing the mean ranks of report submission of farmers over the 24 months post PC inception using the Friedman test. The effectiveness of disease surveillance using PCs was evaluated by determining the minimum number of reports required from club members to detect at least one household with poultry disease in the population. This was modelled further using a geometric distribution function to establish the sensitivity of the reporting system. Additionally, PCs were evaluated using focussed group discussions and structured questionnaire interviews. The syndrome reporting efficiency of PCs was 0.8. The PC approach was sustainable because there were no significant differences in report submission between the 24 months post inception (Friedman test, χ2(23) = 32.93, p = 0.08). The probability of detecting outbreaks in disease hotspots of Eastern Zambia was estimated at 98% (51-100). Most respondents were either very satisfied or extremely satisfied with the approach. The study concluded that PCs can be used as a community-based platform for low cost syndromic surveillance that is sustainable.
Using ensemble modelling, the project managed to set up a viable system for rapid detection of poultry diseases which utilised disease and trade hotspots among the rural poultry sector in Eastern Zambia. Through its studies this research revealed key disease control issues which could be extrapolated to other regions and its model may be applied to enhance disease surveillance for other livestock such as pigs, goats, cattle and aquaculture.
| Item ID: | 58242 |
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| Item Type: | Thesis (PhD) |
| Keywords: | disease surveillance, extension programmes, financial analysis, hot spots, market chain, modelling, Newcastle disease, production costs, rural poultry, social networks, surveillance, syndromes, traditional remedies, trends |
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| Copyright Information: | Copyright © 2018 Chrisborn Mubamba |
| Additional Information: | Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 2: Mubamba, C., Ramsay, G., Abolnik, C., Dautu, G., and Gummow, B. (2016) A retrospective study and predictive modelling of Newcastle Disease trends among rural poultry of eastern Zambia. Preventive Veterinary Medicine, 133. pp. 97-107. Chapter 4: Mubamba, C., Ramsay, G., Abolnik, C., Dautu, G., and Gummow, B. (2018) Analysing production and financial data from farmers can serve as a tool for identifying opportunities for enhancing extension delivery among the rural poultry sub-sector in Zambia. Preventive Veterinary Medicine, 158. pp. 152-159. Chapter 5: Mubamba, Chrisborn, Ramsay, Gavin, Abolnik, Celia, Dautu, George, and Gummow, Bruce (2018) Combining value chain and social network analysis as a viable tool for informing targeted disease surveillance in the rural poultry sector of Zambia. Transboundary and Emerging Diseases, 65 (6). pp. 1786-1796. Chapter 6: Mubamba, C., Ramsay, G., Abolnik, C., Dautu, G., and Gummow, B. (2018) Is syndromic data from rural poultry farmers a viable poultry disease reporting tool and means of identifying likely farmer responses to poultry disease incursion? Preventive Veterinary Medicine, 153. pp. 84-93. |
| Date Deposited: | 10 May 2019 02:55 |
| FoR Codes: | 07 AGRICULTURAL AND VETERINARY SCIENCES > 0707 Veterinary Sciences > 070704 Veterinary Epidemiology @ 100% |
| SEO Codes: | 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8303 Livestock Raising > 830309 Poultry @ 50% 97 EXPANDING KNOWLEDGE > 970107 Expanding Knowledge in the Agricultural and Veterinary Sciences @ 50% |
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