High Risk Of Fluke In The West

It is no surprise to find that, given the weather and our recent fluke forecasts, a significant proportion of our sheep PM cases in our lab in early November have produced a diagnosis of acute fluke infection.  In some instances large numbers of sheep have either died or are reported to be affected.  Triclabendazole inefficacy or inappropriate flukicide choice for the time of year have been risk factors in some outbreaks.  Many of the fluke recovered have been around 5-7mm in length suggesting infection occurring in late September.    It is tempting to assume that the risk is universally high on all farms.  Some farms, and even fields within farms, may be severely affected and at high risk, however other farms or fields will be lower risk because of drier conditions, absence of snail habitats and fluke populations that remain susceptible to triclabendazole.

Monitoring fluke risk and local epidemiology will be of critical importance this autumn and to that end we suggest that post-mortem examinations should be carried out to investigate sudden deaths in ewes or lambs.  This is the quickest and most reliable way to diagnose acute fasciolosis.   The quicker the diagnosis is made the better for the remaining sheep.  Investigate the first death in a group and don’t wait until there have been multiple losses.

Cattle

Cattle can potentially pick up liver fluke from grass until the day they are housed.   In contrast to sheep this is more likely to cause production losses than deaths.  Remember to time post housing treatments to ensure the maximum kill of fluke in the liver.  If you are sending animals to slaughter request feedback on liver condition.  Consider collecting faecal samples after Christmas to check that treatment has been successful or to assess whether treatment is required if you are unsure.

Heather Stevenson, SAC Consulting Veterinary Services