Equine Parasitology

External (mites, lice) and internal parasites (redworms, roundworms and tapeworms, etc.) are found in and on horses worldwide. Infestation with external parasites can cause severe itching and hair loss while internal parasites are a frequent cause of poor performance and ill-thrift. They may also cause diarrhoea, colic and even death in some cases.

Testing for external parasites is carried out via microscopic examination of plucked hair. Detection of internal parasites is primarily carried out by microscopic examination of faeces, but other methods may also be used.
Accurate and timely testing is necessary (i) to identify the parasites present in your horse, (ii) to determine if deworming treatment is required, and (iii) to determine which drugs are most effective for treatment.
The IEC offers the following tests for the detection of parasites in horses:


Parasite detected 


Faecal egg count (FEC)

Large and small redworms, 


and threadworms

  • Results are expressed as number of eggs per gram (EPG) of faeces
  • Treatment may be required above certain EPG threshold
  • Repeated FEC’s should be used to determine anthelmintic efficacy


  • Results are expressed as number of eggs per gram (EPG) of faeces
  • Shedding of tapeworm eggs may be intermittent; a negative result does not rule of infection

Fluke egg screen 

Liver fluke 

  • Results are expressed as ‘detected’ or ‘not detected’  
  • Liver fluke infection in horses may not result in patent infection, i.e. the fluke may not produce any eggs

Baermann technique 


  • Detects shedding of lungworm larvae in faeces
  • A negative result does not rule out lungworm infection as infection does not always lead to patent infection  

Cryptosporidium screen 


  • Detects cryptosporidium antigens in faeces
  • Cryptosporidium may be involved in foal diarrhoea 

Skin microscopy 

Lice and mites

  • Pluck of hair from affected area is required for analysis
  • 24-hour turnaround time on all tests
  • Discounts available for batches of samples
  • Follow-up veterinary advice available