Fasciola
See also Parasites - internal
Diagnosis
Grazing history, clinical examination, serology, faecal egg count, response to treatment. Necropsy findings.
ELISA serology is available for the detection of infection with both immature and adult fluke. Titres appear 6-8 weeks (cattle) or 4-6 weeks (sheep) after infection and remain high for at least 12 weeks after the infection has been removed. Antibodies remain high in untreated subacute and chronic stages.The false negative rate is low in both cattle (2.5%) and sheep (nil). The test is not suitable for other species.
For a herd diagnosis, NSW DPI recommends that 10 animals be bled and a pooled fluke ELISA requested. The samples will be tested as two pools of five samples in the laboratory. The ELISA test has been shown to be sufficiently sensitive to detect a single infected animal in a pool containing serum from 4 other uninfected animals.
Faecal egg counts are only of value in chronic fascioliasis where eggs are being excreted (patent infection); they are of no value in acute and subacute infections.
ELISA serology is more sensitive than faecal egg counts for the detection of chronic fascioliasis in both cattle (30% more infected animals detected) and sheep (15-20% more infected animals detected).
ELISA serology is the only diagnostic method for the detection of acute and subacute fascioliasis, which typically occurs in NSW from autumn to early winter and in late spring.
Specimens required
- Serum samples from affected animals and their cohorts for ELISA serology
- Faeces for egg counts in the following situations:
-
- where serum collection is not feasible, or,
- in animals where liver fluke has been detected in the herd or flock and treatment has been given in the previous 5 months, or
- where paired faeces and serology is specifically sought for comparative study.
At least 30 g of fresh faeces from each of at least 10 animals in the flock or herd, submitted in a screw-capped jar for fluke egg count. Samples may be tested individually, or pooled in groups of up to five samples. Pooling reduces costs. Submitters should nominate if they wish the samples to be tested in pools. If pooling is not requested, the laboratory will test the individual samples. At necropsy, fascioliasis should be diagnosed in the field and there is no need for laboratory specimens.
For more information, refer to the Primefact 446, Liver fluke disease in sheep and cattle.