Bovine Leukemia Virus as a One Health Challenge in Nutrition, Food Security, and Public Health: A Narrative Review.

Bovine leukemia virus (BLV) is among the most prevalent infectious diseases of dairy cattle, with herd-level infection rates exceeding 80% in many regions worldwide. Although only a minority of infected animals develop clinical enzootic bovine leukosis, subclinical effects are widespread and extend beyond animal health. This narrative review examines BLV through a One Health lens, emphasizing its nutritional, food security, and public health dimensions. Relevant literature was identified through targeted searches of major scientific databases using terms related to BLV, milk composition, nutrition, food security, and One Health. Evidence suggests that BLV infection reduces milk yield and alters composition, particularly in cows with high proviral load. Decreases in fat, protein, and bioactive components diminish milk's caloric density and functional quality, potentially lowering consumers' dietary intake of essential fatty acids, fat-soluble vitamins, and immunomodulatory proteins. Increased susceptibility to mastitis due to BLV-associated immune dysfunction further exacerbates nutrient losses, compounding inefficiencies in milk production. Collectively, these changes undermine dairy's nutritional value, especially for populations that rely heavily on milk as a staple food, including young children, low-income households, and communities in low- and middle-income countries where dairy products may provide important dietary energy, protein, and micronutrients. At the systems level, BLV contributes to economic inefficiency through reduced herd productivity. These losses aggregate into a significant drag on dairy supply, with implications for affordability, accessibility, and environmental sustainability. Although definitive evidence of zoonotic transmission is lacking, recurring detection of BLV deoxyribonucleic acid, proteins, and antibodies in human tissue raises questions regarding potential public health risks. Taken together, BLV represents an underappreciated One Health challenge, encompassing animal productivity, human nutrition, economic access, and possible zoonotic implications. Future research should quantify BLV's economic and nutritional impacts on consumers and clarify risks to human health to support interventions aligned with animal health, food security, and sustainable nutrition.