Assessment of risk to human health associated with aflatoxins in the Kenyan dairy value chain

Abstract

Aflatoxins are considered a food safety priority in Kenya in light of the recurrent outbreaks of aflatoxicosis in humans and livestock and a possible role in childhood stunting and immunosuppression. Nonetheless information is lacking on the health risks posed to public health by aflatoxins in the Kenyan dairy value chain. This study looked into the levels of contamination by aflatoxins along the dairy value chain and developed a quantitative risk assessment model to assess their public health impact. A survey of 286 farmer households was carried out in Kwale (n=37), Isiolo (n=56), Tharaka-Nithi (n=65), Kisii (n=64) and Bungoma (n=64) Counties, chosen to represent different agro-ecological zones (AEZ). Determination of aflatoxin levels was carried out by use of competitive enzymelinked immunosorbent assay. Literature review was conducted to determine the impacts of aflatoxin standards on health and nutrition in Sub-Saharan Africa considering the case of Kenya. Finally this study used the World Organisation for Animal Health (OIE) risk assessment framework consisting of release assessment, exposure assessment, consequence assessment, and risk estimation to estimate the risk of liver cancer from aflatoxin exposure. Overall, 26% of maize, 10% of millet and 11% of sorghum had aflatoxin B1 (AFB1) exceeding the Kenyan limit of 5 ppb. In samples collected during the rainy season, maize from Kisii and Bungoma, (temperate AEZ), had the lowest mean contamination whereas maize from Kwale (subhumid AEZ) had the highest contamination. Millet and sorghum from Tharaka-Nithi (humid AEZ) and Isiolo (semi-arid AEZ), respectively, had the highest mean contamination (p<0.05). Dairy feed concentrates from farmers had AFB1 levels from less than 1 ppb to 9,661 ppb. The percentages of dairy feeds with AFB1 above Kenyan limits of 5ppb were 73% from farmers, 90% from feed retailers and 62% from feed manufacturers. AFM1 levels in milk were up to 6,999 ppt and the prevalence was lowest in Kwale (3.5%) and highest in Tharaka-Nithi (64.5%). Exposure to AFM1 through milk was estimated at between 0.3 and 1 ng AFM1 per kg body weight per day through the consumption of milk. The annual incidence rates of cancer attributed to the consumption of AFM1 in milk were 3.5 × 10−3 (95% CI: 3 × 10−3–3.9 × 10−3), 2.9 × 10−3 (95% CI: 2.5 × 10−3–3.3 × 10−3), 1.4 × 10−3 (95% CI: 1.2 × 10−3–1.5 × 10−3) and 2.7 × 10−3 (95% CI: 2.3 × 10−3–3 × 10−3) cancers per 100,000 in adult females, adult males, children 6–18 years old, and in children less than five years old, respectively. These annual incidence rates are quite low, nonetheless, risk managers should take action based on cumulative exposure from all sources of aflatoxins and hence the need to know the importance of different sources. The prevention of aflatoxins in dairy feeds would effectively curb the presence of aflatoxin residues in milk and other animal products meant for human consumption. Strategies to reduce aflatoxins in animal feeds include keeping the moisture and temperature of feeds moderately low (<13% moisture; temperature range of 20 - 35oC) to inhibit mould growth, maintaining cleanliness of on-farm equipment, and, where possible, using mould inhibitors or aflatoxin binders. The use of binders in feeds should be further investigated to determine safety and efficacy. The understanding and awareness of the feed manufacturers, retailers, producers (dairy and grains) and consumers on aflatoxins should be improved so that they produce/demand aflatoxin free foods/ feeds.