Extensive rain and flooding in the eastern states of Australia over the past few months will result in large populations of mosquitoes. This will increase the chance that sheep and goats become affected by the disease Eperythrozoonosis (commonly called “Epi”). This is caused by the bacteria Mycoplasma ovis and can be spread by mosquitoes. The bacteria attach to red blood cells and cause them to rupture.
The signs of Epi appear the same as barber’s pole worm: anaemia and death, but your response should be very different.
If you have more expanses of surface water or flooding than usual this year and the mossies are bad, don’t rush to the drench gun if some sheep deaths occur. Barber’s pole worm should be high on the suspect list as the season progresses—but mosquitoes could be spreading Mycoplasma ovis bacteria (they could also be spreading the Bovine Ephemeral Fever virus).
If you suspect either barber’s pole worm or Epi, your priority is a WormTest (preferably with a larval culture) done without mustering the stock.
If there is a high worm egg count (WEC), treat the sheep immediately with an effective broad-spectrum drench, taking great care to muster slowly, with your drench pack with you. Any sheep that collapse during muster should be drenched on the spot and left behind in some shade, otherwise, the risk of death is high. A larval culture will be valuable to confirm a diagnosis of barber's pole worm, but don't wait the week for the results if sheep are dying and there is a high WEC.
If the WEC is not high, suspect Eperythrozoonosis, but it is important to also do another worm egg count one to two weeks later.
With Epi do not handle the stock or you may worsen the situation. Mustering them for a drench "just in case" can result in extensive losses.
There is no practical treatment for a whole mob for this disease; you must wait it out. However, if valuable stock such as rams are affected, discuss the feasibility of treatment with your local or district veterinarian; antibiotics have traditionally not met with great success, but their use is being re-evaluated.
Handling the stock will likely result in more deaths as the anaemic animals do not tolerate mustering very well, and bringing sheep together can increase the spread of the disease through the flock.
Why a second WormTest?
A follow up WormTest should be done one to two weeks after the first because the same conditions that favour Epi can sometimes cause a rapid and large infection with barber’s pole worms. This can cause deaths before high egg counts become obvious. A large burden of immature worms can be causing anaemia, but as they have not become adults they are not laying eggs. Such a situation should become apparent with a follow up worm test, as there will be a high WEC by another week or two.
Liver fluke also causes anaemia and death, but it only occurs in the high rainfall regions and on specific properties that have the watersnail intermediate host. This snail does not exist in the typically drier areas of the state.
A worst-case scenario is that the sheep are suffering from both barber’s pole worm and Eperythrozoonosis. The treatment for barber’s pole worm will need to take priority, as a severe infection is unlikely to resolve.
If you suspect Eperythrozoonosis, consult your local or district veterinarian, who can conduct blood tests to try to confirm the disease.
NOTE: Eperythrozoons can also be spread during and after lamb marking and shearing where infected blood from one animal contacts the next animal on knives or shears, or where flies move from wounds on one animal to the next.