Suck? Or Bite? It Makes a Big Difference for Cattle Lice. 

Cattle lice are seen throughout the world and are common on beef properties across Australia. They cause irritation, behavioural changes, hair loss and skin lesions – leading to decreased animal welfare and loss in production, as well as damage from rubbing to fences and trees. Adelaide University’s 2015 survey shows that cattle lice were the second highest disease concern for South Australian beef producers, and most treat their cattle for lice at some time during the yearⁱ. But the various lice on cattle cause different problems and need different treatments.  

It is important therefore to know what type, or types, of lice are on your cattle. 

Cattle lice come in 2 types- sucking and biting. Because they are small, only a few millimeters long, most cattle producers wouldn’t be able to tell them apart. But the type of lice on the cattle is critically important, for several different reasons.

Biting lice of cattle are the same genus and are very similar in size, shape and colour to the common biting lice of sheep. However, they are very different biologically and the lice of different animals don’t cross-infect. These lice have a broad head and a powerful mandible, which they use to graze (chew) on scurf and skin debris on the surface of the skin.

Sucking lice on cattle may be one of 5 different species. Like the long-nosed sucking louse pictured above, they have a long stylet which is used to puncture the skin and suck blood from the capillaries.

The difference in the diet of the 2 types of lice is important because it affects which products will work and which won’t – sucking lice are exposed to any chemical in the animal’s blood, whereas biting lice are not. For example, a product which can’t move from the blood onto the skin will not kill biting lice (see below for more).

Both types of lice avoid direct sunlight and prefer cattle with long hair, so their numbers tend to increase after the onset of cold weather in autumn and winter. During the hotter times of the year, lice will seek refuge in the tail switch or in hard-to-see places such as the underside of the cattle. Note that a single mob of cattle may have two or more different species of lice on them at once.

Four reasons why you should know the type of lice on your cattle:

1. Product claims- Many producers face frustration when treating cattle lice. This is because not all products used to kill lice will work on all types. For example, dips and sprays containing synthetic pyrethroids (SPs), organophosphates (OPs) and diflubenzuron (in the IGR class) are registered for and effective against both sucking and biting lice. Some pour-on mectin products (macrocyclic lactones or MLs) also have claims against both types. However, when using injectable mectins (MLs), note that they generally have claims against sucking lice and either no claim to control biting lice, or can be used as ‘’an aid in the control” of biting lice i.e. not registered for a complete kill.
2. Resistance- reports from overseas indicate that there is established resistance in cattle lice populations to mectins (USA) and the SP deltamethrin (Ireland). Resistance has not been confirmed in Australian lice, but reports from the field indicate that lice populations are harder to eliminate compared to previous years. This may be an early sign of emerging resistance. Knowing what type of lice are resistant will help researchers find trends and provide better advice for control.
3. Damage- both types of lice will cause irritation to the skin, rubbing, scratching and subsequent hair loss. This results in poor welfare outcomes including exposure during cold weather. However, sucking lice also ingest substantial amounts of blood, potentially leading to anaemia and weakness in heavily-infested animals.
4. Disease vectors- sucking lice have been found to carry the blood parasite Theileria orientalis[i], which causes the deadly disease theilieriosis. Although not considered to be a ‘biological vector’ for this disease, which is normally transmitted by bush ticks Haemaphysalis longicornis, sucking lice are a potential ‘mechanical vector’ and could spread the disease within a herd.

Treatment tips:

Effective control of lice relies on:

• treatment of all cattle in herd (no missed musters)

• with an effective chemical (check label for details)

• applied thoroughly, including on the tail switch

• early in the season before numbers build up, but not too early as lice hide in difficult to access places

• checking cattle 2 to 4 weeks after treatment to ensure the ‘lice taxis’ are re-treated so they don’t re-infest the entire herd once their chemical wears off

Whichever product is used, it is common practice to treat twice, 4-6 weeks apart to ensure a complete kill. This is because lice larvae emerging from the eggs (nits) can re-infest cattle after the treatment has worm off.

If all cattle are treated with an effective treatment at the same time, lice can be eliminated from a mob and a whole property. This is because lice only live on the cattle and don’t have any reservoir in the environment.

Identification:

For identification of cattle lice, submit samples in sealed jars to your state veterinary diagnostic laboratory or veterinary parasitology laboratory.

For more information about cattle lice and control methods, see LiceBoss.

Pictures courtesy of Matt Playford, Jess Morgan and Peter James.

[i] SR Lanyon, ML Anderson and MP Reichel (2015) Survey of farmer knowledge and attitudes to endemic disease management in South Australia, with a focus on bovine viral diarrhoea (bovine pestivirus), Australian Veterinary Journal 93, 5: 157-163

[ii] Biniam T. Lakew, Sarbast K. Kheravii, Shu-Biao Wu, Steve Eastwood, Nigel R. Andrew, Adrian H. Nicholas, Stephen W. Walkden-Brown (2021) Detection and distribution of haematophagous flies and lice on cattle farms and potential role in the transmission of Theileria orientalis. Veterinary Parasitology, 298