Chapter 1: GENERAL INTRODUCTION
1.1 BACKGROUND INFORMATION
Kenya has a livestock population of 18.6 million cattle, 16.8 million sheep, 25.1 million goats
and 463,000 pigs (Livestock population as per Kenya Bureau of Statistics 2015). Livestock
sub-sector contributes about 12% of the total Gross Domestic Product (GDP) for the country
and 40% of the total agricultural GDP. Livestock production is a major socio-economic
activity for the communities that live in the high rainfall areas for dairy production and in the
arid and semi-arid areas (ASALS) for beef production. In both areas, livestock provides
substantial raw material for the local dairy, meat, hides and skins, wool and hair processing
industries. The livestock sector accounts for over 30 % of farm gate value of agricultural
commodities.
The sector is however burdened by many pests and diseases including Foot-and-mouth
disease (FMD) which threaten food security and livelihoods of smallholders and prevent
animal husbandry sectors from developing their economic potential. Foot and mouth disease
is notorious for its ability to severely affect and indeed disrupt national, regional and
international trade in animals and animal products. The burden of FMD on developing
countries involving the loss of animals and biological diversity and lowering of production
efficiency is underestimated.
Foot and mouth disease is a highly infectious, debilitating viral disease with huge economic
implications in livestock production in many developing countries where it’s endemic (Arzt,
2011). It affects artiodactyl wild and domestic species ( Jamal and Belsham, 2013) including
cattle, goats, sheep pigs, camelids, buffalo and deer leading to trade embargoes in countries
18
,free of the disease on livestock and their products and is therefore a major global animal
health problem.
The disease causes pyrexia and formation of vesicles in the mouth, nose, teats and interdigital
space of the feet which turn into erosions. Clinically this manifests as excess salivation, lips
smacking, teeth grinding (due to pain), nasal discharge, mastitis, lameness with lethargy and
anorexia (Radostits et al., 2000). This leads to reduced milk production, infertility, eventual
loss of weight, loss of draught power and death can be a common sequele in young animals
due to degeneration of heart muscle (Kitching, 2002; FAO, 2002). Secondary bacterial
infection on the lesions in affected parts of the body complicates the recovery process leading
to protracted illness though most animals recover within two weeks. Lesions are not
prominent in sheep and goats and unapparent in wild animals like buffaloes ( Donaldson and
Sellers, 2000). Transmission between animals can occur in various ways including animal to
animal contact and contaminated animal products. This is because during the acute phase of
the disease the virus is excreted in all body excretions and secretions and these are infectious
(Sumption et al., 2012). Peak transmission occurs when vesicles rupture contaminating the
environment including pastures and animal watering points. The virus is also found in lymph
nodes and bone marrow of slaughtered infected animals with survival being prolonged if the
meat is frozen. Mechanical transmission can occur by animals, human, formites and air. These
diverse modes of transmission leads to easy virus movement across borders often
circumventing control measures in place.
Mortality is low in adult animals, but deaths can be common in young piglets, calves and
lambs(Coetzer et al., 1994).
19
,The severity of clinical signs varies with the strain of virus, the exposure dose, the age and
breed of animal, the host species and the immunity of the animal. The signs can range from a
mild or inapparent infection to one that is severe. Certain strains of the virus may be of low
virulence for some species of animals (Donaldson, 2000). It is also difficult to distinguish
FMD from other viral vesicular diseases, including swine vesicular disease, vesicular
stomatitis and vesivirus infection, solely on the basis of clinical findings. Additionally, other
infectious agents can cause stomatitis, e.g. the viruses of mucosal disease , malignant catarrhal
fever, rinderpest, peste des petits ruminants, papular stomatitis, orf, blue tongue and epizootic
haemorrhagic disease. Thus, a definitive diagnosis requires laboratory investigation. Given the
potential of rapid spread of FMD, it is essential that suspected cases are quickly reported and
investigated. It’s important to use the most rapid and accurate tests, so that control measures
can be implemented speedily.
Foot and mouth disease virus has a wide host range, an ability to infect in small doses, a rapid
rate of replication, a high level of viral excretion and multiple modes of transmission,
including wind. These features make FMD a difficult and expensive disease to control and
eradicate( Knight-Jones and Ruston, 2013). It’s a disease that is much feared by farmers,
veterinarians and those associated with livestock production. Countries free of the disease take
great precautions to ensure that the virus does not gain entry. Consequently FMD is a major
constraint to international trade in livestock and animal products.
Foot and mouth disease is endemic in Kenya and in most African countries. Infection with
FMD quickly spreads in susceptible livestock and the epidemiology of FMD in this region is
complicated by the multiplicity of susceptible hosts both wild and domestic. There are also
20
, multiple virus serotypes, poorly informed control measures, inadequacies in the control of
movements of livestock and livestock products. Wildlife move freely further complicating
zoo-sanitary control measures. Additionally diverse socio-economic factors derail control
efforts (Wekesa et al., 2015). Kenya, like many other FMD endemic countries around the
world, is in the process of implementing the Progressive Control Pathway (PCP) for Foot-and-
mouth disease. This is in line with the Global Framework for the progressive control of Foot-
and-Mouth Disease and other Trans-boundary Animal Diseases (GF-TADs) in the country
and in the region.
This study was designed to address two areas; understanding the epidemiology of FMD in
domestic ruminants for formulation of the most effective control strategies. This was done
by surveillance for the disease to estimate the seroprevalence and determine the risk factors
associated with the disease. Secondly effective vaccines can be developed by studying the
relatedness of virus strains in circulation with the vaccine strains. This study evaluated the
relationship of recent circulating FMD field strains with other documented viruses and the
vaccine strains in use in the region.
1.2 JUSTIFICATION OF THE STUDY
Influence of FMD incidence on the economy of a country has shown that it is impossible to
farm economically in the presence of FMD. The exclusion of a country in regional and
international markets is undoubtedly the most serious economic consequence of the presence
of FMD. Foot-and-mouth disease has been endemic in Kenya for several decades and for the
country to develop effective control strategies certain knowledge gaps have to be addressed.
21
1.1 BACKGROUND INFORMATION
Kenya has a livestock population of 18.6 million cattle, 16.8 million sheep, 25.1 million goats
and 463,000 pigs (Livestock population as per Kenya Bureau of Statistics 2015). Livestock
sub-sector contributes about 12% of the total Gross Domestic Product (GDP) for the country
and 40% of the total agricultural GDP. Livestock production is a major socio-economic
activity for the communities that live in the high rainfall areas for dairy production and in the
arid and semi-arid areas (ASALS) for beef production. In both areas, livestock provides
substantial raw material for the local dairy, meat, hides and skins, wool and hair processing
industries. The livestock sector accounts for over 30 % of farm gate value of agricultural
commodities.
The sector is however burdened by many pests and diseases including Foot-and-mouth
disease (FMD) which threaten food security and livelihoods of smallholders and prevent
animal husbandry sectors from developing their economic potential. Foot and mouth disease
is notorious for its ability to severely affect and indeed disrupt national, regional and
international trade in animals and animal products. The burden of FMD on developing
countries involving the loss of animals and biological diversity and lowering of production
efficiency is underestimated.
Foot and mouth disease is a highly infectious, debilitating viral disease with huge economic
implications in livestock production in many developing countries where it’s endemic (Arzt,
2011). It affects artiodactyl wild and domestic species ( Jamal and Belsham, 2013) including
cattle, goats, sheep pigs, camelids, buffalo and deer leading to trade embargoes in countries
18
,free of the disease on livestock and their products and is therefore a major global animal
health problem.
The disease causes pyrexia and formation of vesicles in the mouth, nose, teats and interdigital
space of the feet which turn into erosions. Clinically this manifests as excess salivation, lips
smacking, teeth grinding (due to pain), nasal discharge, mastitis, lameness with lethargy and
anorexia (Radostits et al., 2000). This leads to reduced milk production, infertility, eventual
loss of weight, loss of draught power and death can be a common sequele in young animals
due to degeneration of heart muscle (Kitching, 2002; FAO, 2002). Secondary bacterial
infection on the lesions in affected parts of the body complicates the recovery process leading
to protracted illness though most animals recover within two weeks. Lesions are not
prominent in sheep and goats and unapparent in wild animals like buffaloes ( Donaldson and
Sellers, 2000). Transmission between animals can occur in various ways including animal to
animal contact and contaminated animal products. This is because during the acute phase of
the disease the virus is excreted in all body excretions and secretions and these are infectious
(Sumption et al., 2012). Peak transmission occurs when vesicles rupture contaminating the
environment including pastures and animal watering points. The virus is also found in lymph
nodes and bone marrow of slaughtered infected animals with survival being prolonged if the
meat is frozen. Mechanical transmission can occur by animals, human, formites and air. These
diverse modes of transmission leads to easy virus movement across borders often
circumventing control measures in place.
Mortality is low in adult animals, but deaths can be common in young piglets, calves and
lambs(Coetzer et al., 1994).
19
,The severity of clinical signs varies with the strain of virus, the exposure dose, the age and
breed of animal, the host species and the immunity of the animal. The signs can range from a
mild or inapparent infection to one that is severe. Certain strains of the virus may be of low
virulence for some species of animals (Donaldson, 2000). It is also difficult to distinguish
FMD from other viral vesicular diseases, including swine vesicular disease, vesicular
stomatitis and vesivirus infection, solely on the basis of clinical findings. Additionally, other
infectious agents can cause stomatitis, e.g. the viruses of mucosal disease , malignant catarrhal
fever, rinderpest, peste des petits ruminants, papular stomatitis, orf, blue tongue and epizootic
haemorrhagic disease. Thus, a definitive diagnosis requires laboratory investigation. Given the
potential of rapid spread of FMD, it is essential that suspected cases are quickly reported and
investigated. It’s important to use the most rapid and accurate tests, so that control measures
can be implemented speedily.
Foot and mouth disease virus has a wide host range, an ability to infect in small doses, a rapid
rate of replication, a high level of viral excretion and multiple modes of transmission,
including wind. These features make FMD a difficult and expensive disease to control and
eradicate( Knight-Jones and Ruston, 2013). It’s a disease that is much feared by farmers,
veterinarians and those associated with livestock production. Countries free of the disease take
great precautions to ensure that the virus does not gain entry. Consequently FMD is a major
constraint to international trade in livestock and animal products.
Foot and mouth disease is endemic in Kenya and in most African countries. Infection with
FMD quickly spreads in susceptible livestock and the epidemiology of FMD in this region is
complicated by the multiplicity of susceptible hosts both wild and domestic. There are also
20
, multiple virus serotypes, poorly informed control measures, inadequacies in the control of
movements of livestock and livestock products. Wildlife move freely further complicating
zoo-sanitary control measures. Additionally diverse socio-economic factors derail control
efforts (Wekesa et al., 2015). Kenya, like many other FMD endemic countries around the
world, is in the process of implementing the Progressive Control Pathway (PCP) for Foot-and-
mouth disease. This is in line with the Global Framework for the progressive control of Foot-
and-Mouth Disease and other Trans-boundary Animal Diseases (GF-TADs) in the country
and in the region.
This study was designed to address two areas; understanding the epidemiology of FMD in
domestic ruminants for formulation of the most effective control strategies. This was done
by surveillance for the disease to estimate the seroprevalence and determine the risk factors
associated with the disease. Secondly effective vaccines can be developed by studying the
relatedness of virus strains in circulation with the vaccine strains. This study evaluated the
relationship of recent circulating FMD field strains with other documented viruses and the
vaccine strains in use in the region.
1.2 JUSTIFICATION OF THE STUDY
Influence of FMD incidence on the economy of a country has shown that it is impossible to
farm economically in the presence of FMD. The exclusion of a country in regional and
international markets is undoubtedly the most serious economic consequence of the presence
of FMD. Foot-and-mouth disease has been endemic in Kenya for several decades and for the
country to develop effective control strategies certain knowledge gaps have to be addressed.
21
