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La Nina weather declared! Horse worm parasites rejoice!

La Nina weather declared! Horse worm parasites rejoice!

La Nina weather declared! Horse worm parasites rejoice!

So a La Nina weather event has been declared.  This is great news for horse worms. Not so great news for horse owners….

In this article:

  • La Nina – warm wet conditions over summer – a worm paradise for growth a development
  • Heavy rains spreading worm eggs & larvae away from manure – more likely for horses to eat
  • Unusual wet, warm conditions - consider an additional Fecal Egg Count or Wormer over the summer period.

Firstly, what is a La Nina?  The opposite to El Nino which brings drought, La Nina brings humid, wet tropical weather. The Bureau of Meterology is forcasting ‘typically a wetter period for eastern Australia’ over this summer.

So why does a warm wet summer affect worms in horses?  Put simply – they love it and are developing to the next stage in their life cycle in paddocks and pasture waiting to find their way into your horse’s system.

Horse worm eggs and larvae need moisture.  In Australia that means they hate our summers with our hot dry conditions causing paddocks and manure to dry out quickly, slowing or even halting worm egg development.  Concentrating on survival o means they not developing to the stage where they actively seek a ride in our horse’s digestive system.

We all know that horse’s don’t really eat near their manure.  Eggs and larvae rely on other ways to get around to the pasture that horses eat.  And one of the best ways is heavy rain.

The recent wet weather around the east coast of Australia means that eggs and larvae may now have travelled far away from manure piles -  and be patiently waiting for a passing by grazing horse.

Worm larvae also tend to prefer grass close to the soil, so it’s in your interests to prevent horses grazing grass too short.

In Australia, spring and autumn generally provide the best conditions for horse worm development in pasture.  However the La Nina – a wet, warm summer - means the perfect conditions for development continue significantly increasing the risk of dangerous parasite burdens.

What should I do?

We should still aim to break the lifecycle of the worms mechanically as much as possible with pasture management (spelling, rotation with sheep & cattle, ensuring pasture isn’t overgrazed) but be ready to step in with the right wormer at the right time if necessary to ensure worm burdens don’t rise to a level where they might be damaging to horse health.

So, be extra careful about monitoring horses and consider reducing the time between fecal egg counts or worming to 8 weeks - particularly with young, old or vulnerable horses.

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