Chorioptes bovis - Itchy Mite in Cattle
If your cattle are itchy and you don’t think it is lice, read on ………
Summary: 1) If you have itchy cattle with patchy hair loss, and you can not see lice, or have treated for lice with no affect, this mite could be the cause. 2) They exists across every state in Australia (and throughout Europe and North America), and cause itchiness over the cooler months. 3) The itch, hair loss and scabs/crusting usually starts at the base of the tail, but can progress down the back legs and eventually all over the body. 4) Sometimes they will only cause heavy crusting in localised areas (eg on the inside of the hocks) with no apparent itchiness. 5) It is difficult to control effectively but a newer, longer acting anti-parasite injection called Moxidectin offers hope. |
What is C bovis?
C bovis is a mite that is too small to see (as big as a grain of dust), and lives in the upper layers of skin where it crawls around eating skin debri. (As opposed to lice which are visible at 3mm long and live on top of the skin and in the hair coat.) C bovis has a two week life cycle and generally can last only a few days off the animal (possibly a few weeks as has been found experimentally). It can also affect horses, sheep, goats and camels, causing itchiness and hair loss in these animals also.
Symptoms
 |  |  |
C bovis in a Highland bull | C bovis in an Angus cow | C bovis in a horse |
Generally only a few animals in a herd will be affected (less than 10%), and some animals may have the mite and not show any symptoms. With most cattle, the skin problems start at the tail base and then extend down the backs of the legs and can affect the udder or scrotal skin. It can extend up the underbelly and eventually affect the skin around the shoulders and neck. Some cattle can be so itchy and spend so much time scratching that they lose weight and if lactating, milk production can drop significantly.
It results in itchiness and patchy hair loss with the skin showing scaly, flaky change, and in severe infestations, heavy scabs and crusting with yellow exudate under the crusts when these are removed. Occasionally, some animals will show lesions around the lower legs, especially the back feet.
What else can cause this?
The main other problem that can cause itchiness and patchy hair loss will be one of the various species of cattle lice, although the adult lice and the lice eggs are visible to the naked eye around the skin lesions (especially around the neck and topline where lousy cattle have most of their lesions). Also, cattle lice are relatively easily controlled with most pour-ons, whereas, these products are only slightly effective against C bovis, or in some cases, totally ineffective.
There are not really any other parasites in Australia that can cause such skin itch, although they do exist in other countries. Allergies are very rare in cattle.
Diagnosis
The mite can be seen on skin scrapings taken by a vet, although they can be easily missed as they are few and far between, and of course, very small. The main way to tell that your animal has this mite is by the distribution of the skin lesions over the body and the failure to respond to general lice treatments (and improvement with specific mite treatments).
Treatment
C bovis is difficult to kill and it’s eggs will continue to hatch for weeks after you use an effective treatment, so it may take a fortnight for the animal to get complete relief after a single treatment.
From my reading, and from personal experience, Moxidectin (as an injection) is by far the simplest and most effective treatment. A single injection will appear to help in nearly every case, but a second injection (& sometimes a third) 30 days later is a good idea to be sure, so that all the adult lice that hatch from the eggs left in the skin are also killed. Ivermectin injection can also work, but I have personally found this to be a less effective longer term control. Moxidectin as a pour-on should work in theory, but there are reports of it failing (& reports of it working), so stick to the injectable form.
Since this mite only affects a small proportion of animals in your herd, it is appropriate to just treat the affected animals, however, if you had a lot of animals with it, or you wanted to try to eliminate it from your property, you would need to use Moxidectin injection twice, 30 days apart on all your cattle older than three months (and treat all your horses, sheep, goats and camels as well) as carrier animals appear to exist.