Sero-prevalence and risk factors associated with African swine fever on pig farms in southwest Nigeria

BMC Veterinary Research

Yrjo Tapio Grohn²  Gabriel Ogundipe¹  Babasola Olugasa¹  Emmanuel Jolaoluwa Awosanya² 

[1] Department of Veterinary Public Health and Preventive Medicine, Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Oyo State, Nigeria;Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca 14853, NY, USA

关键词: Southwest Nigeria;    Transmission;    Management;    Season;    Pigs;    African swine fever;    Sero-prevalence;   

Others  :  1213744
DOI  :  10.1186/s12917-015-0444-3

 received in 2014-11-19, accepted in 2015-05-20,  发布年份 2015

【 摘 要 】

Background

African swine fever (ASF) is one of the major setbacks to development of the pig industry in Nigeria. It is enzootic in southwest Nigeria. We determined the sero-prevalence and factors associated with ASF among-herd seropositivity in 144 pig farms in six States from southwest Nigeria during the dry and rainy seasons using indirect Enzyme Linked Immunosorbent Assay (ELISA) for ASF IgG antibodies. An interviewer-administered questionnaire was used to collect information on demography, environmental and management factors. We performed descriptive statistics, and univariate and multivariable analyses to determine the among-herd sero-prevalence of ASF and its associated factors.

Results

The overall herd sero-prevalence of ASF was 28 % (95 % Confidence interval (95 % CI) 21 – 36); it was significantly higher (P <0.05) in the dry season (54 %; 95 % CI 37 – 70) than the rainy season (18 %; 95 % CI 11 – 27). In the univariate analysis, having a quarantine/ isolation unit within 100 m radius of a regular pig pen (OR = 3.3; 95 % CI 1.3 – 8.9), external source of replacement stock (OR = 3.2; 95 % CI 1.3 – 8.3) and dry season (OR = 5.3; 95 % CI 2.2 – 12.7) were risk factors for ASF among-herd seropositivity. In the multivariable logistic regression, there was interaction between season and herd size. Our final model included season, source of replacement stock, herd size and interaction between herd size and season. Herds with an external source of replacement always had higher ASF sero-prevalence compared with herds with an internal source. The herd size effect varied between seasons.

Conclusions

The ASF herd level sero-prevalence in southwest Nigeria was higher in pig herds with an external source of replacement stock and in the dry season. The effect of season of the year the samples were taken on ASF seropositivity was modified by herd size. We encourage strict compliance with biosecurity measures, especially using an internal source of replacement stock and measures that minimize movement on pig farms in southwest Nigeria, in order to enhance ASF free farms.

【 授权许可】

   
2015 Awosanya et al.

【 图 表 】

Fig. 1.

Fig. 2.

【 参考文献 】

• [1]Food Agricultural Organization of the United Nations (FAO). Recognizing African swine fever. A field manual. FAO Animal Health Manual 2000. http://www.fao.org/docrep/004/x8060e/x8060e00.htm. Accessed on 4 Dec., 2013.
• [2]Sánchez-Vizcaíno JM, Mur L, Martínez-López B. African swine fever (ASF): five years around Europe. Vet Microbiol. 2013; 165(1–2):45-50.
• [3]World Organization for Animal Health (OIE). Disease Distribution Maps 2014 and 2015 – Disease Information. 2015. http://www.oie.int/wahis_2/public/wahid.php/countrymapinteractive. Accessed on 30 March, 2015.
• [4]Costard S, Wieland B, de Glanville W, Jori F, Rowlands R, Vosloo W et al.. African swine fever: how can global spread be prevented? Phil Trans R Soc B. 2009; 364(1530):2683-96.
• [5]Babalobi OO, Olugasa BO, Oluwayelu DO, Ijagbone IF, Ayoade GO, Agbede SA. Analysis and evaluation of mortality losses of the 2001 African swine fever outbreak, Ibadan, Nigeria. Trop Anim Health Prod. 2007; 39:533-42.
• [6]Plowright W, Thomson GR, Neser JA. African swine fever. In: Infectious diseases of livestock, with special reference to southern Africa. 1st ed. Coetzer JAW, Thomson GR, Tutsin RC, editors. Oxford University Press, Cape Town, South Africa; 1994: p.567-99.
• [7]Sánchez-Vizcaíno JM, Arias M. African swine fever. In: Diseases of swine. Zimmerman J, Kar-riker LA, Ramirez A, Schwartz KJ, Stevenson GW, editors. John Wiley & Sons, Iowa, United States of America; 2012: p.396-404.
• [8]Boinas FS, Wilson AJ, Hutchings GH, Martins C, Dixon LJ. The persistence of African swine fever virus in field-infected Ornithodoros erraticus during the ASF endemic period in Portugal. PLoS ONE. 2011; 6: Article ID e20383
• [9]Luther NJ, Majiyagbe KA, Shamaki D, Lombin LH, Antiabong JF, Bitrus Y et al.. Detection of African swine fever virus genomic DNA in a Nigerian Red River hog (Potamochoerus porcus). Vet Rec. 2007; 160:58-9.
• [10]Babalobi OO, Ayoade GO, Olugasa BO, Oluwayelu DO, Oyedela O. Differential diagnosis of a swine epizootic of unknown aetiology in Ibadan, Oyo State, Nigeria. IJVM. 2003; 58(2/3):86-9.
• [11]Food Agricultural Organization of the United Nations (FAO). African swine fever in West Africa: Togo, Senegal, Gambia and Guinea-Bissau. [French] Mission report from 1 to 16 June 1998. (1998a) Available from: http://www.fao.org/docrep/field/382969.htm. Accessed on 25 March, 2012.
• [12]Food Agricultural Organization of the United Nations (FAO). African swine fever in Nigeria hits rural poor. News & Highlights. December 1998. (1998d) Available from: http://www.fao.org/NEWS/1998/981201-e.htm. Accessed on 25 March, 2012.
• [13]Sánchez-Vizcaíno JM, Martínez-López B, Martínez-Avilés M, Martins C, Boinas F, Vial L, et al. African Swine Fever. Scientific report submitted to EFSA 2009: 1–141
• [14]Olugasa BO. Serological evidence of African swine fever virus infection in commercial pig herds in southwest Nigeria. Afr J Livest Ext. 2007; 5:61-6.
• [15]Owolodun OA, Bastos ADS, Antiabong JF, Ogedengbe ME, Ekong PS, Yakubu B. Molecular characterization of African fever viruses from Nigeria (2003 – 2006) recovers multiple virus variants and reaffirms CVR epidemiological utility. Virus Genes. 2010; 41:361-8.
• [16]Odemuyiwa SO, Adebayo IA, Ammerlaan W, Ajuwape ATP, Alaka OO, Oyedele OI et al.. An outbreak of African swine fever in Nigeria: virus isolation and molecular characterization of the VP72 gene of a first isolate from West Africa. Virus Genes. 2000; 20:139-42.
• [17]Owolodun OA, Obishakin ET, Ekong PS, Yakubu B. Investigation of African swine fever in slaughtered pigs, Plateau state, Nigeria, 2004–2006. Trop Anim Health Prod. 2010; 42(8):1605-10.
• [18]Fasina FO, Shamaki D, Makinde AA, Lombin LH, Lazarus DD, Rufai SA et al.. Surveillance for African swine fever in Nigeria, 2006–2009. Transbound Emerg Dis. 2010; 57(4):244-53.
• [19]Owolodun OA, Yakubu B, Antiabong JF, Ogedengbe OE, Luka PD, John Audu B et al.. Spatio-temporal dynamics of African swine fever outbreaks in Nigeria, 2002–2007. Transbound Emerg Dis. 2010; 57(5):330-9.
• [20]Olugasa BO, Ijagbone IF. Pattern of spread of African swine fever in south-western Nigeria, 1997–2005. Vet Ital. 2007; 43(3):621-8.
• [21]Sánchez-Vizcaíno JM, Mur L, Martínez-López B. African swine fever: an epidemiological update. Transbound Emerg Dis. 2012; 59(1):27-35.
• [22]Atuhaire DK, Ochwo S, Afayoa M, Mwiine FN, Kokas I, Arinaitwe E, et al. Epidemiological Overview of African swine fever in Uganda (2001–2012). J. Vet. Med. 2013, Article ID 949638, 9 pages http://dx.doi.org/10.1155/2013/949638.
• [23]Cocks P, Abila R, Bouchot A, Benigno C, Morzaria S, Inthavong P et al.. FAO ADB and OIE SEAFMD Study on Cross Border movement and market chains of large ruminants and pigs in the Greater Mekong Sub Region. Bangkok, Thailand; 2009.
• [24]Boklund A, Alban I, Mortensen S, Houe H. Biosecurity in 116 Danish fattening swine herds: descriptive results and factor analysis. Prev Vet Med. 2004; 66:49-62.
• [25]Gardner IA, Willeberg P, Mousing J. Empirical and theoretical evidence for herd size as a risk factor for swine diseases. Anim Health Res Rev. 2002; 3:43-55.
• [26]Food Agricultural Organization of the United Nations (FAO). FAO takes a close look at the pig Sector in Eastern Europe to better understand the threats of African Swine fever. EMPRES Watch 2010. http://www.fao.org/docrep/012/ak755e/ak755e00.pdf. Accessed on 4 Dec., 2013.
• [27]Magali Jacquier. Occurrence, Distribution and Characterisation of African Swine Fever Virus (ASFV) in the Tick Ornithodoros porcinus in the Kruger National Park. BFA SEMINAR SERIES NO. 32 Held at Ulwazi Institute, Suburbs, Bulawayo, on 17 September 2004. (2004) http://www.biodiversityfoundation.org/documents/s32.pdf Accessed 2 Dec., 2013.
• [28]Carrillo C, Borca MV, Afonso CL, Onisk DV, Rock DL. Long-term persistent infection of swine monocytes/macrophages with African swine fever virus. J Virol. 1994; 68:580-3.
• [29]Barcelo J, Marco E. On farm biosecurity. Proceedings of the 15th International Pig Veterinary Society Congress. 1998.129-33.
• [30]Fasina FO, Agbaje M, Ajani FL, Talabi OA, Lazarus DD, Gallardo C et al.. Risk factors for farm-level African swine fever infection in major pig-producing areas in Nigeria, 1997–2011. Prev Vet Med. 2012; 107:65-75.
• [31]Otesile EB, Ajuwape ATP, Odemuyiwa SO, Akpavie SO, Olaifa AK, Odaibo GN et al.. Field and Experimental Investigations of an Outbreak of African Swine Fever in Nigeria. Revue Élev Méd vét Pays trop. 2005; 58(1–2):21-6.
• [32]Penrith ML, Vosloo W. Review of African swine fever: transmission, spread and control. J S Afr Vet Assoc. 2009; 80(2):58-62.
• [33]Biosecurity for Highly pathogenic Avian Influenza – issues and options. 2008.
• [34]Sánchez-Vizcaíno JM. Early detection and contingency plans for African swine fever. Compedium of technical items presented to the OIE World Assembly of Delegates and to OIE Regional Commissions 2010, 129-168.
• [35]Mannelli A, Sotgia S, Patta C, Sarria A, Madrau P, Sanna L et al.. Effect of husbandry methods on seropositivity to African swine fever virus in Sardinia swine herds. Prev Vet Med. 1997; 32:235-41.
• [36]Muhanguzi D, Lutwama V, Mwiine FN. Factors that influence pig production in Central Uganda—case study of Nangabo Sub-County, Wakiso district. Vet World. 2012; 5(6):346-51.
• [37]Federal Department of Livestock (FDL) Nigeria. Report on study and mapping of poultry farming systems and pig production areas by support for the Integrated National Action Plan on Animal and Human Influenza (SPINAP) Project in Nigeria. Official document (2010).
• [38]Thrusfield M. What sample size should be selected? In: Veterinary Epidemiology. 3rd ed. Blackwell Publishing Limited, UK; 2007: p.232-8.
• [39]Bennett S, Woods T, Liyanage WM, Smith DL. A simplified general method for cluster-sample surveys of health in developing countries. World Health Stat Q. 1991; 44:98-106.
• [40]Otte MJ, Gumm ID. Intra-cluster correlation coefficients of 20 infections calculated from the results of cluster-sample surveys. Prev Vet Med. 1997; 31:147-50.
• [41]Arias M, Sánchez-Vizcaíno JM. Manual de diagnóstico serológico de la peste porcina africana. Monografías INIA. 1992; 83:5-44.
• [42]Ade-Ajayi JF, Falola TO, Hamilton A, Kirk-Greene M, Udo RK. Nigeria - Britannica academic edition. 2010 http://www.britannica.com Accessed on 2 Dec., 2013.
• [43]Statistical Analysis System (SAS) Institute Inc. SAS/STAT® 9.3 User’s Guide. Cary, NC: SAS Institute Inc. 2011. http://support.sas.com/documentation/cdl/en/statug/63962/HTML/default/viewer.htm Accessed on 2 Dec., 2013