Modeling the Impact of Newcastle Disease Virus Vaccinations on Chicken Production Systems in Northeastern Madagascar

Abstract

Chickens are a key source of nutrition for rural Malagasy communities. Due to high endemic rates of Newcastle disease, it remains challenging to raise sustainable chicken flocks as a consistent food source. Here, we explore the impact of triannual Newcastle disease virus (NDV) vaccine interventions on the growth and herd immunity acquisition of Malagasy chicken flocks. Between 2011 and 2018 we collected longitudinal data to assess the population dynamics of chicken populations in remote Malagasy communities. In 2016, we launched a pilot campaign for vaccination in six rural communities to determine the impacts on chicken survivorship and productivity. We used these data to specify a mathematical model of realistic Malagasy chicken population dynamics under a triannual vaccination regime. The mathematical model represents an extension to conventional SIR models that allows for modeling the impact of specific vaccinations on chicken flock dynamics, rather than estimation of parameters. Understanding chicken population dynamics is important for realizing the potential for domestic chicken flocks to serve as sustainable food sources. The results suggested that vaccination coverage of at least ~40% is necessary over 5+ years to achieve population doubling, while complete herd immunity may not be possible given the short duration of effectiveness of vaccination, and the high levels of births and deaths in the chicken flocks.

Transcriptome Analysis Reveals Inhibitory Effects of Lentogenic Newcastle Disease Virus on Cell Survival and Immune Function in Spleen of Commercial Layer Chicks

“…NDV is a contagious viral disease that involves complex host-virus interactions in the immune, nervous, and respiratory systems. Chickens infected with NDV show respiratory signs such as gasping and coughing; nervous signs such as tremors, paralyzed wings and legs, and twisted neck; swelling in the eyes and neck [ 21 ]; watery diarrhea [ 22 ]; and reduced egg and meat production [ 23 ]. ND can cause damage to hematopoietic [ 24 ], lymphoid [ 25 ], vascular and neural cells [ 26 ].…”

Evaluation of tenrec population viability and potential sustainable management under hunting pressure in northeastern Madagascar

“…To avoid such an outcome for spiny tenrecs, without compromising human health, a combination of hunting management and nutritional replacement will be necessary. Domesticated meat production, particularly of chickens, is a nascent alternative to compensate for the demand of wild meats in the region (Golden et al, 2014;Annapragada et al, 2019). Similarly, programs to increase consumption of insects as a protein source have shown early success (Tao and Li, 2018).…”

Constraints on Rice Cultivation in Eastern Madagascar: Which Factors Matter to Smallholders, and Which Influence Food Security?

“…It furthermore included training on, for example, land preparation, soil conservation, composting, biological pest control as well as livestock breeding, management, and health (Harvey et al, 2018). Chickens were the prevalent livestock around the CAZ but are vulnerable to diseases (e.g., Newcastle disease) and community-centred interventions can support smallholders to afford vaccinations, particularly to target households without access to irrigable land (Annapragada et al, 2019;Borgerson et al, 2019;Maminiaina et al, 2007). Most of the small-scale livelihood projects implemented around the CAZ lasted less than a year but continuation and increasing efforts based on the gained experience will be key to improve food security and reduce deforestation (Harvey et al, 2018;Tabor et al, 2017).…”