There is an old saying that ‘a sheep’s worst enemy is another sheep’ – sheep, like all animals, suffer from a number of contagious diseases. When they were grazed on open country they were generally healthy, but as sheep farming intensified, greater numbers of sheep were confined to smaller paddocks and keeping them healthy became a bigger challenge. The following health problems were present in sheep on open country, but grew worse under intensive farming.
Hydatids and other worms
Hydatids (Echinococcus granulosus) was well established in New Zealand in the late 19th century. The disease is caused by a parasite that may occur in dogs as an intestinal tape worm. During the cycle of development it exists as a cyst in the organs of sheep, human beings and other animals. Dogs become infected by eating raw offal from an infected sheep.
In the late 1950s a massive control effort began, including establishing 800 local voluntary committees, education, promotion, peer pressure, dedicated hydatids officers, dog dosing strips and the introduction of the Hydatids Act 1959. In 2002 New Zealand was pronounced provisionally free of hydatids, and the control programme a success.
Lungworm and worms of the gut were major problems, especially in young sheep, in some areas by the early 1880s. In 1881 a stock inspector in North Canterbury reported an outbreak, with the mortality rate of affected flocks being 5 –20%. He recommended turpentine (distilled from the resin of pine trees) as the best remedy. Infected sheep were often dosed with a mixture of turpentine and milk.
Sheep scab was the most serious stock health problem in the early years of large-scale sheep farming in New Zealand. The disease is caused by the mange mite Psoroptes communis ovis, which lives in the skin of sheep. Infected animals lose their wool and condition.
A Scab Ordinance was passed in 1849 to control the introduction of scabby sheep from Australia. Thereafter provincial governments enacted increasingly harsh measures to try to control the problem. Sheep inspectors checked sheep for the disease and courts could order infected flocks to be slaughtered. In the 1850s and 1860s several large stock owners were bankrupted by scab because of the impact of the disease on their sheep, the cost of treatment, or the financial penalties set by the courts.
Dipping was known to be the best treatment for scab, but farmers disagreed on what ingredients made the best dipping solution. The decision was often down to the whim of the person in charge of the job. In 1868 John Robinson, the manager at Whiterock Station, north of Christchurch, dipped the sheep in arsenic. He killed several hundred, and nearly killed the shepherds as well.
Treatment was by dipping the sheep in boiled tobacco water. Sometimes salt, saltpetre, sulfur or arsenic were added. By the end of the 1880s New Zealand was largely free of scab, partly because of the severe penalties imposed by the courts and partly due to the increase of wire fencing, which meant farmers could keep infected sheep away from their flocks.
There were isolated outbreaks of anthrax (Bacillus anthrax) from the 1870s to the early 1900s. The cause was found to be bones, imported from India, which had been crushed and spread on pasture and crops as fertiliser. Between 1903 and 1935 the government put measures in place to prevent the introduction of anthrax, including a ban on importing bone meal.
Anthrax spores have been used as a weapon in biological warfare. In 1942, British bio-weapons trials severely contaminated Gruinard Island in Scotland with anthrax, making it uninhabitable for the next 48 years.
Anthrax is one of the oldest recorded diseases of ruminants (sheep, cattle and goats) and horses, and also affects humans. The spores can survive for decades in the soil and enter an animal by being eaten or breathed in, or through damaged skin. They quickly spread through the body, causing cell destruction and bleeding. In ruminants, death is usually sudden.
Anthrax became known as wool-sorters’ disease after an outbreak in Bradford, England, in the late 19th century, when it was found that humans were ingesting anthrax spores from wool pelts.