Prevalence and Distribution of Foot-and-Mouth Disease Virus Serotypes and Serotype O Subtypes in Kenya in 2019 and 2020
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Date
2024-10
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Kenyatta University
Abstract
Livestock is a source of livelihood, contributing to the reduction of poverty in many
parts of the globe. In Africa, livestock is an asset, a source of food and income. In
Kenya, approximately 12% of the country’s Gross Domestic Product (GDP) is
contributed by livestock production and similarly, 42% of the agricultural GDP.
Additionally, livestock offers employment to 50% of the agricultural labour force.
Animal diseases, however, pose a great challenge in the industry among them being
FMD (Foot-and-Mouth Disease), which is a transboundary viral disease typical
among the cloven-hoofed animals. This disease has a huge economic impact on
farmers as it affects many animals and disrupts the trade in animals as well as their
products. It is also known to be endemic in most parts of the world including Africa,
exists in seven serotypes (A, O, SAT 1, SAT 2, SAT 3, C, and Asia 1) and numerous
subtypes (topotypes) and the antisera from one serotype cannot neutralize another
serotype. Moreover, the movement of infected animals is closely linked with the
spread of the disease, and quarantine measures and vaccination are key in controlling
its spread, especially in endemic areas. In Kenya, the disease occurrence and severity
have continued to increase despite the implemented control measures. A cross sectional study was done to establish the disease prevalence, distribution, circulating
serotype O topotypes, and their genetic divergence from the current vaccine strain. A
total of 267 bovine epithelial samples were analysed, sourced from cattle presenting
with clinical disease in the years 2019 and 2020. FMDV (Foot-and-Mouth Disease
Virus) antigen detection and serotyping ELISA was performed and those positive for
serotype O antigen were further analyzed for genetic diversity. Viral RNA was
extracted from the confirmed serotype O samples using PureLink® Viral RNA/DNA
Mini Kit from Invitrogen according to the manufacturer’s instructions. The partial
FMDV VP 1 gene was amplified through RT (Reverse Transcription) PCR
(Polymerase Chain Reaction) and directly sequenced. The generated sequences were
edited using BioEdit version 7.2.5 and phylogenetically analysed using MEGA X
version 10.2.6 by neighbor-joining at 1000 bootstrap replicates before viewing them
through Tree view. The antigen detection and serotyping gave an overall virus
prevalence of 65.9% (176/267). From the same results, serotype SAT 1 had the
highest prevalence of 45.5%(80/176) followed by serotype O at 37.5% (66/176).
Serotype SAT 2 had a prevalence of 14.2% (25/176) and serotype A had the least of
2.8% (5/176). The phylogenetic analysis on FMDV serotype O revealed that all the
sequences analysed were of the EA (East African) 2 topotype. The genetic analysis of
these sequences showed a divergence from the current vaccine strain by the
replacement of some amino acids on the gene. This study, therefore, confirms that the
2019 and 2020 outbreaks were predominantly caused by serotype SAT 1 with some
serotype O viruses causing these outbreaks likely to have mutated and not being
covered by the current vaccine for serotype O. This information is useful to disease
control policymakers, implementors and farmers in effecting disease control at their
specific levels and recommends continual monitoring of the FMDV serotypes and
topotypes that are in circulation, and regularly matching the vaccine strain with the
circulating viruses to ensure effective vaccination measures.
Description
A Thesis Submitted In Partial Fulfillment Of The Requirements For The Award Of The Degree Of Master Of Science (Microbiology) In The School Of Pure And Applied Sciences Of Kenyatta University October, 2024
Supervisor:
1. Antony Kebire
2.Joseph Kamau
3.Abraham Sangula