A retrospective study of Newcastle disease in Kenya

Authors: APOPO, AULERIA - Ministry Of Agriculture, Livestock And Fisheries, State Department Of Livestock; KARIITHI, HENRY - Orise Fellow; ATEYA, LEONARD - Kenya Agricultural And Livestock Research Organization; BINEPAL, YATINDER - Kenya Agricultural And Livestock Research Organization; SIRYA, JANE - Jomo Kenyatta University; DULU, THOMAS - Ministry Of Agriculture, Livestock And Fisheries, State Department Of Livestock; WELCH, CATHARINE - University Of Georgia; HERNANDEZ, SONIA - University Of Georgia; Afonso, Claudio

Submitted to: Tropical Animal Health and Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2019
Publication Date: 9/10/2019
Citation: Apopo, A.A., Kariithi, H.M., Ateya, L.O., Binepal, Y.S., Sirya, J.H., Dulu, T.D., Welch, C.N., Hernandez, S.M., Afonso, C.L. 2019. A retrospective study of Newcastle disease in Kenya. Tropical Animal Health and Production. 52:699-710. https://doi.org/10.1007/s11250-019-02059-x.
DOI: https://doi.org/10.1007/s11250-019-02059-x

Interpretive Summary: Newcastle Disease is a significant poultry disease, caused by a highly virulent virus that is considered a select agent and is reportable affecting trade. The virus has great mobility across continents and the identification of new strains is important for better diagnostics and for effective control of the disease. Furthermore, the identification of reservoirs is important for establishing trade and movement of goods policies. Very little information exist on the epidemiology of Newcastle Disease in Eastern Africa. Here we analyzed all of the Newcastle disease cases reported in Kenya between 2005 and 2015 and identified production systems and ecological factors that may contribute to the endemicity of the virus. We also identified management practices that reveal opportunities for improvement in surveillance, diagnostics and epidemiology of Newcastle disease virus strains in Kenyan domestic poultry.

Technical Abstract: Newcastle disease (ND) is a major constraint to Kenya’s poultry production, which is comprised of approximately 80% indigenous chickens (ICs; caged and free-range system) and 20% exotic chickens (intensive system). This study analyzed cases reported as suspected ND in Kenya between 2005 and 2015. Of the suspected 332 ND reported cases from the three production systems in 27 locations within six Kenyan Agro-Ecological Zones (AEZs), 140 diagnosed as infected with avian orthoavulavirus 1 (AOaV-1; formerly Newcastle disease virus) were present in every year in all AEZs. The numbers of AOaV-1-positive cases differed significantly (p'<'0.05) between the production systems across the years depending on the season, climate, and location. In the free-range system, both ambient temperatures and season associated significantly (p'='0.001 and 0.02, respectively) with the number of cases, while in the intensive and caged systems, the positive cases correlated significantly with season and relative humidity, respectively (p'='0.05). Regardless of the production systems, the numbers of clinically sick birds positively correlated with the ambient temperatures (r'='0.6; p'<'0.05). Failure to detect AOaV-1 in 58% of the ND cases reported, and mortalities exceeding the observed numbers of clinically sick birds suggest deficiencies in the current ND reporting and diagnostic system. Intensive farmers were the slowest in reporting the cases and diagnostic deficiencies were most evident by failure to test the exposure of ICs to natural infection with AOaV-1 and for the AOaV-1-negative cases lack of testing for other pathogens and/or AOaV-1 variants. This study indicates a need for improved surveillance and diagnostics in Kenyan domestic poultry.