SURVEILLANCE FOR AFRICAN SWINE FEVER AND CLASSICAL SWINE FEVER IN BENUE STATE, NIGERIA
1.1 Background Information
African swine fever and classical swine fever are the two most feared and important contagious diseases of pigs worldwide (Penrith et al., 2011; Penrith et al., 2013) and are World Organization for Animal Health (OIE) notifiable diseases (Petrov and Salzungen, 2015). African Swine Fever (ASF) is also known as Peste porcine Africaine, fiebreporcina Africana, maladie de Montgomery(Penrith et al., 2013) while Classical Swine Fever (CSF) is known as Hog Cholera, Peste du Porc, colera Porcina,Virusschweinepest (Penrith et al., 2011; Petrov and Salzungen, 2015).
While outbreaks of ASF have a long and on-going history in Africa (Fasina et al.,2010), CSF up to now is considered an exotic disease within African member states with exception of Madagascar and Mauritius (Penrith et al., 2011;Aiki-Rajietal., 2014). However, very recently CSF was reported in domestic pigsslaughtered at an abattoir in Ibadan, South-western Nigeria (Aiki-Rajietal., 2014),thereby, making both diseases of high risks to the pig industry in Nigeria.
The two diseases exhibit similar clinical picturebut their causative agents differ greatly (Penrith, et al., 2013;Petrov and Salzungen, 2015). Afican swine feveris caused by African Swine Fever Virus (ASFV),a large, double-stranded DNA virus,belongingto its own genus;Asfivirus, the only member of the family Asfarviridae(Dixon et al. 2004), while CSFis caused by Classical Swine Fever Virus (CSFV),a small enveloped positive single-stranded RNA virus of the genus Pestivirus, family Flaviviridae (Petrov and Salzungen, 2015). Both viruses affect only members of the pig family Suidae (Plowright etal., 1994; Moennig, 2000) and are highly contagious to pigs and their ancestor, the Eurasian wild boar (Sus scrofa ferus).African swine fevervirus is the only known DNA arbovirus that has a biological vector that can maintain and transmit the virus (Dixon et al. 2005).
The pig population in Nigeria is estimated at over 7.4 million and is concentrated mainly in the Middle Belt and Southern parts of the country (FAO, 1998b; NBS, 2010). Small holder farms raise most of these pigs(El-Hicheri, 1998; NBS, 2010 Cited by FLD, 2010).This important pig population contributes highly to the food security of the low income rural and periurban population (Ate and Oyedipe, 2011;El-Hicheri, 1998) thereby contributing significantly to the economic welfare of the rural population as well as playing an important role in the social and cultural life of most of the communities in the southern and middle-belt States of Nigeria, including providing cheap meat for traditional marriages and burial rites (Ate and Oyedipe, 2011). In addition, pigs provide a ready and regular source of cash to meet the rural families’ needs, such as paying educational and health expenses; and procurement of farm inputs on a day to day basis (El-Hicheri, 1998; Ate and Oyedipe, 2011).
The pig industry in Nigeria can be classified into small holder farms(having fewer than 50 pigs in the herd at any point in time); medium holder farms (with 50 to 100 pigs in the herd at any point in time); and large holder farms (of over 100 pigs in the herd at any point in time) (Awosanya etal., 2015). The pig farming industry in Nigeria has a significant presence in the north-centraland south-western Nigeria. The pig production system in Benue state Nigeria is predominantly semi-intensive (El-Hicheri, 1998; FAO, 1998a).
The ASF scourge has however adversely affected the bustling activities in the industry since the outbreak of African swine fever in Nigeria in 1997 (Babalobietal., 2007). The various state governments of the affected states have made efforts through farm extension services in educating the farmers on biosecurity measures following that outbreak (Awosanya etal., 2015).
Globally, ASFV is present in Africa, Italy (Sardinia), Georgia, Latvia, Poland, Ukraine, Russia (Moscow) and some Caribbean countries, with an increasing risk of spreading to ASF-free countries in Europe and America (Sánchez-Vizcaínoetal., 2013; OIE, 2015). African swine fever is enzootic in Nigeria (Olugasa, 2007; Sánchez-Vizcaíno etal., 2009; Fasina, et al.,2012).
ASFV is often introduced into pig populations by infected pigs or the meat of infected pigs fed as swill, and this is the usual modes of introduction of CSFVthereby makingthe epidemiology of ASF and CSF similar (Haresnape etal., 1987; Penrith et al. 2013). Both ASFV and CSFVtolerate a wide range of temperatures and pH and can survive for long periods in meat (Mebus et al. 1997; Edwards, 2000).
Classical swine feverhas remained a problem in many parts of the world with both, an economic impact on swine production and a constraining effect on trade (Elbers et al., 1999; Edward et al., 2000; Awosanya etal., 2015).
Nigeria, other West and Central African countries endemic for ASF experience intermittent infections(Fasina etal., 2012). ASF first made an apparently unsustained incursion into South Western Nigeria in 1973 and thenbecame extinct (Owolodun etal., 2010a). However, there was a resurgence of outbreaksin West Africa from 1996 onwards, with the ASF virus entering Nigeria between August and September1997; and has continuedto spread acrossNigerian pig farms, causing sporadic outbreaks with attendant mortalities (Fasina etal., 2012).
1.2 Statement of Research Problems
African Swine Fever (ASF)is the main threat to the pig industry in Africa and has been sporadically occurring in different parts of Nigeria,causing deaths in pig populationsresulting in heavy economic losses (Babalobi etal., 2007; Costard etal., 2009a)and mortality approaching 100 % (Costard etal., 2009a).
Persistence infections with both ASFV and suspected CSFV appear to recur in the core pig-producing areas ofthe country having had significant economic and social impact inNigeria since 1997(Olugasa, 2007).
The status of CSF in Nigeria remains unknown thereby raising the suspicion of its existence or coexistence with ASF (Aiki-Rajietal., 2014).
However, there is, in particular, dearth of information on CSF even though Benue state is one of the largest pigs producing and pork consuming states in Nigeria.
Previous and recent outbreaks of ASF in Benue Statehave affected pig production in themidst of growing importance in pig farming and have affected livelihoods of pigkeepers in Nigeria as a result of direct loss of pigs and easy source of animal protein, due to mortality (Babalobi et al., 2007).
The reported presence of ASFV positive pigs in neighbouring state of Taraba (Abwage et al., 2015) appears to add to the existing threat on swine industry in Benue state as explained by the proposed theory of geographical contiguity and supported by the incidence of infections (Fasina et al., 2012).
Therefore, the continuous surveillance ond monitoring of both ASFand CSF in pigs in Benue State and indeed Nigeria needs not to be overemphasized since the presence and reintroduction ofthese viruses can be devastating to the pig population.
1.3 Justification of the Research
Worldwide, the goal of pig production operation is to make money or provide some advantage such as cheap source of animal protein for the family diet. So any disease threatening pig production threatens the food security of the human population and its social balance and thus the need of the surveillance for ASF and CSF diseases.
There are enormous potentials for pig production in Benue state, but the continuous maintenance of ASF in pigs in Nigeria is amajor constraints to the growth of the pig industry. Regular surveillance and monitoring of this disease will provide comprehensive and readily accessible data base that will help to contain any fulminating outbreak.
There is lack of regular surveillance or monitoring for ASF as well as lack of documented report on CSF; hence the need for this study.
Surveillance for ASF and CSF will help to ascertain the status andincrease awareness of the diseases to facilitate early detection in order to instituteappropriate control measures during outbreaks.
Also, the results from the study would contribute to the design of the disease control strategies and policy formulation.
1.4 Aim of the Study
The aim of the studywas to determine thepresence of antibodies to African swine fever virus and classical swine fever virus in pigs in piggeriesand in slaughtered pigs at Makurdi central slaughter slab in Benue State,Nigeria.
1.5 Objectives of the Study
The specific objectives of the study were to determine the:
- presence of antibodies to ASFV and CSFVinpigs in piggeries and in slaughtered pigs at the Makurdi central slaughter slab in Benue State, Nigeria.
- coexistence of antibodies to ASFV and CSFV in pigs in piggeries and in slaughtered pigs at Makurdi central slaughter slab in Benue State, Nigeria.
- risk factors associated with ASFV and CSFV infection in Benue State, Nigeria.
1.6 Research Question(s)
- Does antibodies toASFV and CSFVexist inpigs in piggeries and in slaughtered pigs at Makurdi central slaughter slab in Benue State?
- What is the rate of antibodies to ASFV and CSFV coexistence in pigs in piggeries and in slaughtered pigs at Makurdi central slaughter slab in Benue State?
- What are the risk factors associated with ASFV and CSFV infection in pigs in Benue State?