As spring progresses we can see the complaint in groups of calves of bloody (black) scour, poor thrive and maybe tenesmus (forcing). One of the common causes of these clinical signs is coccidiosis caused by protozoan parasite of the eimeria species. It is a condition that affects calves indoors but also after turnout to pasture. What can happen is they ingest the oocysts in the house and will only show clinical signs when outside. It is also a condition that affects lambs indoors but mostly after turnout as well in my experience.
It happens when young animals ingest oocysts from the environment often shed by their dams. As time goes on the levels of oocysts in the environment build up leading to clinical signs in the infected calves. This is a disease that takes up to 3 weeks before clinical signs appear and typically affects lambs between 3 and 12 weeks and calves up to 6months. What happens are these oocysts or eggs invade the lining of lower intestine and cause damage leading to diarrhoea and poor thrive? So the oocysts causes damage when it invades but then when it matures or bursts even more damage is done. The critical thing to remember also that infected animals can ingest small numbers and ultimately shed millions of oocysts. This is why we see the disease progressing over the months after turnout. So it is a disease usually seen where large numbers of calves are housed and there is a big build up of these coccidian oocysts in the environment. It can affect animals at pasture as well; I often see creep fed lambs/calves being exposed to this disease. Anywhere there is a build up of faeces in the environment there is a risk of coccidiosis. This is why creep feeders should be moved regularly and water sources aren’t leaking to prevent favourable conditions for spread. There is a risk indoors but farmers should be vigilant for the clinical signs that might appear when calves/lambs are turned out. The good news is young calves and lambs develop immunity for life when exposed to low numbers. It is so important then to minimise exposure and build-up of oocysts in the environment.
There can be variations in the type of scour and symptoms seen but it is often darker and can have some fresh blood in it. Sometimes with batches of calves/lambs I will see failure to thrive faecal staining on rear end and mild scours. In severe cases you will see animals forcing and losing weight quiet rapidly. To diagnose I usually go on clinical signs and may also take a couple of faecal samples for the lab which may include worm egg counts to rule out other issues. Once confirmed I begin treating affected animals and also preventative medicine for the incontacts. It is worth noting there are different species of eimeria (coccidia) so when sampling it is worth looking for pathogenic strains. With lambs also it is useful to distinguish whether nemadtodirus is the issue or both together.
Once coccidiosis is diagnosed it is important to look at husbandry and controlling the build up of oocysts in the environment. Sheds need to be cleaned more regularly and avoid areas of heavy faecal build up around drinkers and feeding equipment. Only a few disinfectants are licensed to kill oocysts in the environment so it is important to talk to your vet about these. The one I recommend which is licensed to kill oocysts in the environment is keno-cox or interkosak. We must remember that these oocysts can survive year to year and long term strategies must be around housing hygiene and grazing lower risk pastures.
To treat calves we will often use a product containing toltrazuril. The reason I favour this for calves is it more persistent and I have personally had better results. The timing of this dose is critical, it must be given in advance of the problem to reduce shedding. So if you have a problem indoors then early administration is advised. All calves should be treated. As a general rule I recommend treating calves 1 week post turnout with toltrazuril if its outdoors the problem is occurring. These calf products are POMs so talk to your vet about which one is best for your herd. I often rec these infected animals receive oral sulpha powders and keep them on oral rehydration therapy as well. We must remember this is a very painful condition and again your vet can make recommendations around pain medication. So if you have a history of coccidiosis in calves or lambs I would advise talking to your vet about using these preventative medicines before problems arise. Improving husbandry can also make huge differences to the levels of oocysts in the environment.
With lambs there are 2 products available diclazuril or toltuzuril again I prefer a once of dose of toltuzuril because it is more persistent.
Some people offer decoquinates in feed but again this is a decision for you and your vet to make.
If you’ve had issues in the past after turnout sit down with your vet now, assess the risks and look at management and preventative dosing that might reduce the risk of coccidiosis on your farm.