A blood sucking external parasite.
What are Cattle Ticks?
Ticks are blood sucking external parasites. The common cattle tick Haemaphysalis longicornis favours cattle but they are not completely host specific and can infest deer, sheep, goats, humans, horses, rabbits, hares, and domestic pets.
There are many different species of tick in the world, but H.longicornis is the only one found in New Zealand. It is called a three-host tick, with each of its growing stages - larvae, nymph, and adult - feeding off separate hosts, not necessarily of the same species.
The adult female tick, which when fully engorged with blood can grow to approximately 9mm long by 7mm wide, lays hundreds of eggs from which the larvae will hatch on nearby vegetation. The larvae attach to a suitable host and feed before falling to the pasture where they develop to a nymph stage. Nymphs will also attach to a host to feed before detaching and developing into an adult. The time taken for the completion of the life cycle varies considerably from days to months depending on factors such as temperature and the host’s immunity developed from previous exposure.
The larvae and nymphal stages of the life cycle position themselves at the tips of long grass or vegetation and attach to the skin of grazing animals or hosts walking through the paddocks.
Ticks are obvious on clinical observation. Ticks are commonly found on the head, ears, udder, and lower body extremities.
About the Disease/Condition
Ticks feed by puncturing the skin of a host with their mouthparts. These puncture sites and any damage that may result can reduce the quality and value of velvet antler during growth in the spring can be a problem in some years.
Nymph (larval) ticks can be a major problem on newborn fawns and young grazing lambs prior to weaning causing anaemia with deaths from blood loss in severe cases.
Cost/Impact on Herd/Farm Revenue
Ticks cause damage to hides, loss of production, anaemia, and death when they are present in large numbers.
Theileriosis is a disease caused by a species of Theileria, a blood-borne parasite that only affects cattle and is primarily transmitted by ticks.
Signs of Theileriosis are those associated with anaemia and include: pale mucous membranes, depression, lethargy, lack of appetite, lagging behind the herd, downer cows that don't respond to treatment ,and in some cases collapse and death. Pregnant cows may abort, and still births are common. In dairy cows there may be a drop in milk production, and somatic cells may rise.
Management and Control
There is one pour-on product, Bayticol, registered for cattle available in New Zealand. It is a systemic pyrethroid and does not have a withholding period for meat to milk.
Ticks are practically impossible to eradicate but there are a few management methods to reduce tick infestation of animals from pasture.