Mozzies in Sheep- How to Prevent?

Mosquitoes are blood-sucking flying insects that are attracted to sheep and other animals to suck blood and breed. The larvae (wrigglers) develop in any still water source, so current flooded paddocks provide perfect conditions for their development.

Mosquitoes affect us for several reasons.

1. Irritation– bites pierce the skin, resulting in swelling, reddening heat, pain and itchiness.
2. Disease transmission– Mycoplasma ovis (M. ovis). also known as Eperythrozoon ovis, eperythrozoonosis, Épy’ or simply E. ovis, causes anaemia and weakness, especially in lambs.
3. Work health and safety– Japanese Encephalitis Virus (JEV)– Already confirmed from a NSW piggery in November 2022, this disease has already spread as far as Victoria and South Australia. The virus has a reservoir in water birds and infects pigs (multiplying host) as well as humans, horses and sheep, which usually have a mild infection. However, watch out for any neurological signs in sheep and report them to your veterinarian. Vaccines are now available to prevent JEV in humans. If you work outdoors and consider yourself at risk, contact your general practitioner for advice.

Treatments or preventives for mosquitoes in sheep

If marking lambs, it is an advantage to use bloodless methods (e.g. rubber rings rather than castration knife or docking iron) if there is a risk of wound irritation or disease transmission due to mosquitoes or other biting insects. Take care to cause minimal trauma to the ear when tagging.

Although many types of chemicals are used to kill lice and fly in sheep, mosquitoes require a different approach because a repellent, not an insecticide, is required. Of the chemical classes registered for sheep, the one with the best insect repellent activity is the synthetic pyrethroid (SP) group.

These chemicals are derived from pyrethrums naturally occurring in chrysanthemum flowers and have been used in a range of applications including lice and fly control in sheep and mosquito repellents in many different species of animals. To assist with choosing a product, use the ‘Product Search’ tools on the paraboss.com.au website.

More information

NSW DPI AgFacts

NSW LLS report by Dr. Libby Read

[1] K.N.Daddow (1980) Culex annulirostris as a vector of Eperythrozoon ovis infection in sheep Veterinary Parasitology, Volume 7, Issue 4, December 1980, Pages 313-317

Image credits: Stephen Doggett