Risk factors for farm-level African swine fever infection in major pig-producing areas in Nigeria, 1997–2011

Abstract

African swine fever (ASF) is an economically devastating disease for the pig industry, especially in Africa. Identifying what supports infection on pig farms in this region remains the key component in developing a risk-based approach to understanding the 2 epidemiology of ASF and controlling the disease. Nigeria was used for this matched case-control study, because there is perpetual infection in some areas, while contiguous areas are intermittently infected. Risk factors and biosecurity practices in pig farms were evaluated in association with ASF infection. Subsets of farms located in high-density pig population areas and high-risk areas for ASF infection were randomly selected for analysis. Most plausible risk factor variables from the univariable analysis included in the multivariable analysis include: owner of farm had regular contact with infected farms and other farmers, untested pigs were routinely purchased into the farm in the course of outbreaks, there was an infected neighbourhood, other livestock were kept alongside pigs, there was a presence of an abattoir/slaughter slab in pig communities, wild birds had free access to pig pens, tools and implements were routinely shared by pig farmers, there was free access to feed stores by rats, and feed were purchased from a commercial source Only the presence of an abattoir in a pig farming community (OR = 8.20; CI 95% = 2.73; 24.63; P < 0.001) and the presence of an infected pig farm in the neighbourhood (OR = 3.26; CI 95% = 1.20; 8.83; P = 0.02) were significant. There was a marginally significant negative association (protective) between risk of ASF infection and sharing farm tools and equipment (OR = 0.35; CI 95% = 0.12; 1.01; P = 0.05).Of the 28 biosecurity measures evaluated, food and water control (OR = 0.14; CI 95% = 0.04, 0.46; P < 0.001), separation/isolation of sick pigs (OR = 0.14; CI 95% = 0.04, 0.53; P = 0.004) and washing and disinfection of farm equipment and tools (OR = 0.27; CI 95% = 0.10, 0.78; P = 0.02) were negatively associated (protective) with ASF infection.Consultation and visits by veterinarian/paraveterinarians when animals were sick (OR = 8.11; CI 95% = 2.13, 30.90; P = 0.002), and pest and rodent control were positively 3 associated with ASF infection of Nigerian farms (OR = 4.94; CI 95% = 1.84, 13.29; P = 0.002).The presentation of sick and unthrifty pigs for slaughter at abattoirs, farmers' inadvertent role, an infected neighbourhood, a pig to pig contact, rodents and wild birds may contribute to infections of farms, whereas washing, disinfection of tools, food and water control, and separation of sick pigs reduces the likelihood of infections. Underlying reasons for these observations and strategies for control are discussed.

Enhancing knowledge and awareness of biosecurity practices for control of African swine fever among smallholder pig farmers in four districts along the Kenya–Uganda border

“…It will therefore be necessary to educate the farmers on the benefits of implementing biosecurity. Fasina et al (2012) in Nigeria found out that it was profitable to implement biosecurity, and such findings could be extrapolated to our study area on the Uganda/ Kenya border. Weaknesses in the implementation of legislative and policy measures severely affected adoption of biosecurity practices by smallholder farmers.…”

Preventive measures aimed at minimizing the risk of African swine fever virus spread in pig farming systems

“…Factors found to increase the risk of outbreak, include free range pig management system [11], the previous occurrence of a disease in the farm [32], the presence of an infected pig farm in the neighbourhood or of an abattoir in the community, and visits by veterinarians and para-veterinarians [33]. A spatial regression analysis found density of the road network, of water bodies and of the domestic swine population to be associated with outbreaks in Russia [34] and a spatial spread model found the movement of infected animals to be the most important factor in the spread of ASFV [35].…”

Drivers and risk factors for circulating African swine fever virus in Uganda, 2012–2013

“…The presence of wire mesh coverings on windows on pig houses seemed to protect pigs inside the houses against ASF infection, perhaps because of the effect on reduction of contacts between freeflying birds, rodents or insects and domestic pigs (although these remain unproven means of spread of ASF (Fasina et al, 2012)); and also limits human contact with the pigs. The presence of engorged hard ticks on pigs was positively associated with lower ASF infection.…”