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Role of Pigs and Economic Losses Associated with ASF
Pigs represent an important economic source of income globally. The FAO data on global meat consumption for 1999 revealed that 88 million tonnes of pig meat was consumed making it the number one meat by quantity consumed for that year (Moore, 2007). National and international data on pigs and pork consumption are in agreement with the FAO reports. Since 1995, the USA has become a major net exporter of pork, with an export market worth of over $1,000 million in 1995 alone (USDA-ERS, 2009, National Pork Producers Council, 2010). However, to date, China remains the most important role-player in the pig industry having approximately 50% of the global pig population. In Benin, a country in West Africa with a human population of approximately 7.9 million (CIA World Fact Book, July, 2006 estimate), an organization has been involved in a major pig production project (Songhai project) targeted at providing pork and other pig products for about 20% of the population. In Côte d’Ivoire, pork constitutes 15% of the total meat consumption and is a widely available source of cheap meat. The estimated pig population in 1996 was 400,000 for this country. In Nigeria, the estimated pig population increased from nearly 2 million in 1984 to about 7 million in 1997 (El-Hicheri, 1998). This rapid increase was associated with the government agricultural initiative aimed at boosting agricultural production and alleviating poverty among the rural and urban poor. Benue, a state in north-central Nigeria with an estimated human population of 2,780,398 (1991 national census figure) alone has about 27,000 pig farmers (≈0.001% of the state population) and produces about 20% of the country’s pigs annually. Major cities and rural areas in the southern parts of the country similarly have numerous pig farms and farmers’ cooperatives. The poor and smallholder farmers who raise an average of 1-50 pigs own the majority of the Nigerian pig population. The continued rise in demand for pigs and pig products in the Lagos metropolis and its suburbs as well as in most other upcoming cities prior to the ASF outbreaks of 1997 boosted pig production activities. Secondary to the purely economic benefits associated with pig production, pigs are used for socio-cultural reasons including bride price, marriage ceremonies, rituals and funeral rites. Furthermore, its by-products serve as a source of fertilizer and energy generation for farmstead and household needs (El-Hicheri, 1998).
The advent of ASF in 1997 and the consequences as reported above has continued to delimit the successes associated with the progress made in the industry. Many pig farmers were discouraged and abandoned pig production while the farmers who continue to produce pigs stand the perpetual risk of ASF outbreaks. To date, it is difficult to determine the actual pig population in Nigeria in view of this perpetual incursion and sporadic outbreaks of ASF on pig farms and the resulting fluctuating levels of commitment to the industry.
ASF Epidemiology in West Africa
From 1996 to date, African swine fever has gained an epizootic dimension in West and Central Africa. It was first reported in Cote d’Ivoire in 1996 leading to the death of over 135,000 pigs (El Hicheri et al., 1998). Prospective and retrospective evaluation of notifications, diagnostics and events associated with ASF outbreaks has revealed that the disease was first discovered in Africa in Kenya in 1921 (Montgomery, 1921); that it occurs in many eastern and southern African countries, including:f Angola, Botswana, Burundi, Kenya, Malawi, Mozambique, Namibia, Rwanda, South Africa, Tanzania, Uganda, Zambia and Zimbabwe (Edelsten and Chinombo, 1995; Bastos et al. 2003; Bastos et al., 2004; Penrith, Thomson and Bastos, 2004; Lubisi et al. 2005; Boshoff et al., 2007; Lubisi et al., 2007; OIE, 2010); it was present in Senegal in 1959 (Bastos et al., 2003), Cameroun in 1982 and 1985 (Wesley and Tuthill, 1984; Ekue and Tanya, 1985; Nix et al., 2006) and many other West Africa countries (Benin, Togo, Ghana, Gambia, Senegal, Cameroun, Chad and Cape Verde) between 1996 to date (Plowright, Thomson and Neser, 1994; El Hicheri, 1998; El Hicheri et al., 1998; Odemuyiwa et al., 2000; Penrith, Thomson and Bastos, 2004; Vial et al., 2007). Recent outbreaks have been reported from Madagascar and Mauritius (Gonzague et al. 2001; Lubisi et al. 2009), and more recently in Chad, Cameroun, Tanzania, Kenya, South Africa and many other locations within and outside Africa (See Appendix B., OIE, 2012). It will be technically sound to consider the whole of the West African sub-region as one epidemiological block and approach the management of any animal disease situation sub-regionally in view of the following:
1. There are no strict border restrictions in the whole of the sub-region and animals, including feral pigs, cross freely within and between local and international borders.
2. The free trade zone policy operates in the sub-region and the livestock markets within the countries in the sub-region are freely accessible to traders and farmgate buyers within the sub-region. In addition, these markets are typically located close to or along the porous borders and illegal trade occurs daily.
3. Quarantine stations, laboratory services and veterinary investigative capacities are weak or non-existent.
4. The livestock disease ecology of the countries within the sub-region is similar with respect to their shared tropical climate, absence of ticks of the Ornithodoros moubata complex, and unconfirmed/dwindling populations of wild pigs. Further, no direct role has been assigned to wild pigs in the epidemiology of ASF in West Africa.
It will appear that the West African sub-region was poorly prepared for the outbreaks that started in 1996. Following the initial infections and subsequent outbreaks in Côted’Ivoire, the FAO sent notifications to neighbouring countries, however, the lack of an established and tested early-warning-system that can trigger immediate reactions and prompt control and management of rapidly spreading infectious diseases prevented the gains that should have been associated with such notifications (El Hicheri, 1998). Furthermore, there was a rapid growth of the pig populations across the sub-region in the face of absent zoosanitary measures (movement restrictions, road blocks, quarantine stations, closure of livestock markets, prompt stamping out and intensive epidemio-surveillances). The distribution of wild pigs spans West and Central Africa (see Figure 2.1a-d) and largely coincides with the distribution of the disease. However, since there was no evidence to suggest that the classical sylvatic cycle which involves wild suids and ticks of the Ornithodoros moubata complex, played a role in the epidemiology of ASF in West Africa, these wild host were not believed to be responsible for the outbreaks recorded in the West and Central African region (Leeson, 1958; Ekue and Wilkinson, 1990). Recently, the soft tick species, O. erraticus, which acted as a vector for ASF in Spain and Portugal, was reported from Senegal and other sahelian countries including Chad, without any known association with warthogs; and O. sonrai was shown to be a possible role-player in the maintenance of the virus in parts of West Africa (Vial et al., 2007). In light of this isolated report, and the growing body of literature substantiating a pig-exclusive cycle in the region, it will be scientifically sound to concentrate effort on domestic pigs in the understanding of epidemiology of ASF in West Africa.
CHAPTER ONE: GENERAL INTRODUCTION
1.1 AFRICAN SWINE FEVER EPIDEMIOLOGY
1.2 AFRICAN SWINE FEVER VIRUS CHARACTERISTICS
1.3 GLOBAL SPREAD OF AFRICAN SWINE FEVER
1.4 SOURCES OF INFECTIONS AND MANAGEMENT STRATEGIES
1.5 ROLE OF PIGS AND ECONOMIC LOSSES ASSOCIATED WITH ASF
1.6 AIMS AND OBJECTIVES
CHAPTER TWO: RATIONALE AND APPROACH TO THE STUDY
2.1 ASF EPIDEMIOLOGY IN WEST AFRICA
2.2 POTENTIAL RISK FACTORS FOR AFRICAN SWINE FEVER
2.3 ASF AND BIOSECURITY IN PIG FARMS
2.4 ECONOMIC COSTS OF AFRICAN SWINE FEVER
2.5 DETERMINATION OF VIRULENCE OF ASF
CHAPTER THREE: SURVEILLANCE FOR AFRICAN SWINE FEVER IN NIGERIA, 2006-2009
3.1 INTRODUCTION
3.2 MATERIALS AND METHODS
3.3 RESULTS
3.4 DISCUSSIONS
3.5 REFERENCES
CHAPTER FOUR: COST IMPLICATIONS OF AFRICAN SWINE FEVER IN SMALLHOLDER FARROW-TO-FINISH UNITS: ECONOMIC BENEFITS OF DISEASE PREVENTION THROUGH BIOSECURITY
4.1 INTRODUCTION
4.2 MATERIALS AND METHODS
4.3 RESULTS
4.4 DISCUSSIONS
4.5 REFERENCES
CHAPTER FIVE: RISK FACTORS FOR FARM-LEVEL AFRICAN SWINE FEVER INFECTION IN MAJOR PIG-PRODUCING AREAS IN NIGERIA, 1997-2011
5.1 INTRODUCTION
5.2 MATERIALS AND METHODS
5.3 RESULTS
5.4 DISCUSSIONS
5.5 CONCLUSIONS
5.6 REFERENCES
CHAPTER SIX: PHYTOCHEMICAL ANALYSIS AND IN-VITRO ANTIAFRICAN SWINE FEVER VIRUS ACTIVITY OF EXTRACTS AND FRACTIONS OF ANCISTROCLADUS KORUNPENSIS, THOMAS AND GEREAU (ANCISTROCLADACEAE)
6.1 BACKGROUND
6.2 METHODS
6.3 RESULTS
6.4 DISCUSSIONS
6.5 CONCLUSIONS
6.6 REFERENCES
CHAPTER SEVEN: LENGTH AND SEQUENCE HETEROGENEITY OF THE ASFIVIRUS THYMIDINE KINASE GENE
7.1 INTRODUCTION
7.2 MATERIALS AND METHODS
7.3 RESULTS
7.4 DISCUSSIONS
7.5 REFERENCES
CHAPTER EIGHT: GENERAL DISCUSSION AND CONCLUSIONS
REFERENCES
