The barber's pole worm Haemonchus contortus causes severe anaemia in cattle in tropical and subtropical regions, with expanding range due to climate change now threatening temperate herds.
Haemonchus infestation causes progressive anaemia that significantly compromises welfare. The reduced oxygen-carrying capacity of severely anaemic blood causes weakness, exercise intolerance, and lethargy that prevents normal activity. Bottle jaw from protein loss and hypoalbuminaemia causes edema and discomfort. Severely anaemic cattle spend increasing time recumbent and show impaired grazing behavior, reducing food intake and creating a cycle of worsening condition. Death from peracute haemonchosis occurs within days in highly susceptible naive animals. The expanding geographic range from climate change means that herds previously unexposed to Haemonchus may encounter the parasite with no established management protocols.