Genetic and serological analysis of foot and mouth disease viruses (FMDV) in selected domestic and wildlife populations in Kenya.

Abstract

Foot-and-mouth disease (FMD), a highly infectious viral disease of domestic and wild cloven-hoofed animals is endemic in Kenya and in eastern Africa. FMD virus (FMDV) exists in seven serotypes (O, A, C, Asia 1, SAT 1, SAT 2 and SAT 3) and six (except Asia 1) have been found in eastern Africa. Serotype C is not current and SAT3 has never been isolated in Kenya. FMD control in Kenya is mainly by vaccination plus animal movement control, and is greatly hampered by limited knowledge on the emerging and re-emerging strains plus roles played by different hosts in the epidemiology. This study has analysed the viruses within domestic and wild animals to increase knowledge for the development of efficacious vaccines and effective disease control strategies. The study used virological tests including virus isolation, antigen detection enzyme-linked immunosorbent assay (AgELISA), reverse transcription-polymerase chain reaction, and sequencing to analyse archived epithelium samples from 47 cattle in various parts of Kenya and probang samples from 102 African buffalo in selected wildlife ecosystems. Serological assays including non-structural protein ELISA, liquid phase blocking ELISA and virus neutralization tests were used on serum samples from the 102 buffalo and on 191 pig serum. The latter were collected during a countrywide survey of FMD in 2010 that coincided with SAT 1 FMDV outbreaks in cattle. Four serotypes (O, A, SAT 1 and SAT 2) were recently circulating among cattle, but there was no evidence for a recent occurrence of serotypes C and SAT 3 in cattle, buffalo or pigs. Analysis of 35 serotype O viruses collected between 2008 and 2013 revealed four independently evolving lineages. Among 38 serotype A field isolates collected between 1964 and 2013, four genotypes within the Africa topotype and a fifth apparently emerging lineage were detected. Analysis of the 102 buffalo samples collected in 2012 found that buffalo harbor SAT 1 and SAT 2 serotypes that were genetically divergent from those found in cattle. Results from 191 pig sera revealed serological evidence for SAT 1 FMDV infection, concluding that pigs may not play an obvious role in FMD spread, but could become important in the epidemiology. Continuous disease surveillance and more research to assess the effectiveness of the current FMDV vaccine strains are recommended. The need for exhaustive studies of the roles of buffalo and pigs in FMD epidemiology in Kenya, including more comprehensive sample material and information plus deliberate efforts to isolate and characterise FMDVs from buffalo and pigs was realized. Better disease control strategies are also recommended, including efficient animal movement control, reduction of FMDV burden among livestock and limiting the association of livestock with wildlife and contact between pigs and cattle.