Benjamin L. Hart

Behavioural defences in animals against pathogens and parasites: parallels with the pillars of medicine in humans.

No other theme in animal biology seems to be more central than the concept of employing strategies to survive and successfully reproduce. In nature, controlling or avoiding pathogens and parasites is an essential fitness strategy because of the ever-present disease-causing organisms. The disease-control strategies discussed here are: physical avoidance and removal of pathogens and parasites; quarantine or peripheralization of conspecifics that could be carrying potential pathogens; herbal medicine, animal style, to prevent or treat an infection; potentiation of the immune system; and care of sick or injured group members. These strategies are seen as also encompassing the pillars of human medicine: (i) quarantine; (ii) immune-boosting vaccinations; (iii) use of medicinal products; and (iv) caring or nursing. In contrast to animals, in humans, the disease-control strategies have been consolidated into a consistent and extensive medical system. A hypothesis that explains some of this difference between animals and humans is that humans are sick more often than animals. This increase in sickness in humans leading to an extensive, cognitively driven medical system is attributed to an evolutionary dietary transition from mostly natural vegetation to a meat-based diet, with an increase in health-eroding free radicals and a dietary reduction of free-radical-scavenging antioxidants.

How mammals stay healthy in nature: the evolution of behaviours to avoid parasites and pathogens

Mammals live and thrive in environments presenting ongoing threats from parasites in the form of biting flies, ticks and intestinal worms and from pathogens as wound contaminants and agents of infectious disease. Several strategies have evolved that enable animals to deal with parasites and pathogens, including eliminating away from the sleeping–resting areas, use of an array of grooming techniques, use of saliva in licking, and consuming medicinal plant-based compounds. These strategies all are species-specific and reflect the particular environment that the animal inhabits. This article is part of the Theo Murphy meeting issue ‘Evolution of pathogen and parasite avoidance behaviours’.

Sickness Behavior in Animals: Implications for Health and Wellness

Sickness behavior represents a centrally organized suite of behaviors – depression, inactivity, anorexia, sleepiness, and reduction of grooming – that evolved in animals living in nature to conserve body resources for the high energetic costs of fever in fighting infections. The domestic scene reveals that sickness behaviors can be an early marker of infections such as mastitis in cows. Aspects of sickness behavior are markers of stressful situations such as separating a young animal from its mother. In husbandry of animals that are pets, farm animals or in zoos, markers of sickness behavior are indications of infection, or stress and impaired welfare.