We’ve had a great summer as far as the t-shirt tan is concerned, albeit considerably less great as far as grazing and hay yields go…. It’s been the hottest summer on record here in the UK, while also persistently dry across many parts. While this has meant that parasites such as strongyles, coccidia and liver fluke have had (happily) a harder time over the period, the recent wet weather means that we now have perfect conditions for a Haemonchus headache. A dry spell followed by warm, wet weather creates perfect conditions for a sudden surge in Haemonchus. And it looks warm and wet for at least the next 10 days…
Why is now a significant time for Haemonchus?
Well, if your animals had Haemonchus larvae at the onset of the dry spell, 4th stage larvae are able to undergo a process known as hypobiosis (or arrested development) within the wall of C3 and they can actually wait until conditions outside the host are favourable again before moulting to adults and laying eggs. It will take about 10 days for L4 larvae to become adults and start laying eggs. It is also possible that larvae can also remain on the pasture in dried out faeces and emerge after rain such that there can be a sudden surge in infection. [It should be noted that these phenomena have been observed in sheep and in other countries but haven’t been properly documented in the UK. Given the sudden surge in Haemonchus cases in alpacas that we have seen following these conditions however, it is likely that this is what is occurring in the UK in alpacas.]
The best conditions for hatching of eggs and larval development are when it’s wet and temperatures are 22-26°C – at temperatures lower than this, development is just a little slower. Development from egg to infective 3rd stage larvae that are the problem ones your animals consume can occur within 4 days, then it takes 12-15 days to develop to adults that produce eggs. So we have a pre-patent period, the time before eggs are produced, while L4 larvae can be consuming blood and causing anaemia in your animals.
What does this mean for you?
- I recommend that you monitor your herd closely over the next couple of months. This monitoring should include checking for anaemia at least weekly in all animals where possible. You might as well check BCS at the same time, although for Haemonchus it’s specifically anaemia that we’re worried about. If you don’t know how to check for anaemia, please click here to watch a video showing you how to do this. https://www.ukalpacavet.com/resources/how-to-assess-for-anaemia-in-alpacas/ You’ll also find a similar resource in the Resources area of the website on how to body condition score.
- Since it takes some time for adults to appear and start laying eggs, it could be at least a couple of weeks before egg counts start increasing. This is why it’s so important to be checking for anaemia in the animals themselves – it can be too late if you wait for egg counts to increase. If you do see anaemia, then do some faecal testing. But if you don’t observe any anaemia over the next few weeks, I suggest faecal testing a representative portion of the herd about a month after the start of the wet weather. At that point, you will detect if the wet weather has increased burdens in your animals. You want to have the chance of detecting it before they get out of control. What’s a representative portion of the herd? Generally speaking we recommend that if you have fewer than 10 animals, you want to test all of them. If you have more than 10, then test 10% of the herd or 10, whichever is the largest number. However, bear in mind that the greater proportion of the herd that is tested, the less you are leaving your parasite control strategy to chance. This is because you are extrapolating from these results to understand what is going on in the herd and then treating on the basis of only clinical signs in untested animals.
- Don’t forget to check crias too when doing your faecal testing because they could also be brewing up coccidia!!
- Find out about our faecal testing service here. Our prices reduce the more you send because we want to encourage you to test more animals. This gives you the best amount of information about what’s going on in your herd!
Why you shouldn’t just go and treat everybody now just in case
This is not recommended because first of all, if you’re poo-picking regularly enough, you might not have a problem anyway. Secondly, it’s generally only 20% of the animals that have an issue and you don’t want to worm everyone when you don’t need to. And thirdly, and most importantly, worming everyone is the quickest way to induce drug-resistant populations of worms. That is bad because animals may die even when treated with an ineffective wormer and a blood transfusion as the parasites will keep sucking their blood – and if you work your way through all the wormers in this way, you’ll have nothing left to treat parasite-infested alpacas with and those that become infected later will die and there will be nothing you can do…
Oh, and finally, if you’re not already poo-picking your pastures, although starting now won’t prevent any larvae being consumed by your animals, it will help reduce further build-up. Poo-picking is by far and away the best thing that you can do to minimise exposure of your animals to worms – and potentially avoid having to use wormers at all. Poo-picking should ideally be done every day. If you do it every 2-3 days, be aware that it may get trodden in making it hard to pick up (especially if it’s been rained on) and quite a lot can accumulate in 2-3 days making it a bigger job!