Many hookworms can infect the host by skin penetration, an important discovery made by A. Looss when he accidentally spilt larvae in water on his hand in 1898.

They attach to the wall of the intestine, reaching the adult stage in two to seven weeks, depending on the species.

In a resistant host, the third stage larva can invade tissue and persist, eventually infecting offspring in females either in milk or prenatally.

The final hosts of strongyles are generally herbivores, such as horses, ruminants, ratite birds and Australian marsupials.

Arrested development is a well-studied feature, which may occur in temperate zones when the weather is too cold, or when it is too dry.

In ewes, they wait for parturition and lactation, when there will be a population of young animals with little or no immunity; the sudden production of eggs by newly matured worms is known as spring rise.

[4] All of these parasites go through a snail to infect the lungs or vascular system of mammals, like artiodactyls, carnivores, marsupials, and cetacea.