Roadmap for development of diagnostic tests for helminths

What are we trying to achieve and why? What is the problem we are trying to solve?

Current tests have a variety of deficiencies including accuracy, specificity, sensitivity, speed, cost and significant requirements for labour and /or specialist technical expertise. This limits their practical application and routine uptake in the field.

What are the scientific and technological challenges (knowledge gaps needing to be addressed)?

• Need to validate biomarkers for infection intensity, morbidity or production impact for fluke or nematodes.
• Need to validate anthelmintic resistance mutations and validate genotype to phenotype relationships in fluke and nematodes
• Need to further validate pooling and composite sampling approaches
• Need validation of species-specific quantitative diagnostics required Eg rumen fluke and liver fluke, different nematode species
• Need to validate much more usable (e.g. less costly) diagnostic platforms including wearable technology, penside tests and laboratory tests,.
• Need to better understand clinical relevance of different levels of anthelmintic resistance for the various helminth species
• Agree and adopt approved methods for validating new diagnostic tests to establish diagnostic sensitivity, specificity, values using field studies, positive and negative predictive values and appropriate diagnostic cut off values. For this, validated panels of samples from mono-species infected animals are required.

What approaches could/should be taken to address the research question?

WAAVP approved guidelines for validating diagnostic assays in the absence of a gold standard.
A panel of samples from animals mono-infected with helminth species to test for cross reactivity.

What else needs to be done before we can solve this need?

Diagnostic tests need to be supported by decision trees to help farmers interpret their results and administer drugs or implement control programmes effectively.

Existing knowledge including successes and failures

• A range of serological tests have been developed, some also as commercially available tests (e.g. Ostertagia-, Fasciola-ELISA)
• Data on use of pooled faecal samples for group/flock coproscopical diagnosis have been published
• A variety of molecular tests for nematode species identification (RT-PCR, pyrosequence genotyping, next-gen sequencing based methods). Largely confined to research use at present due to complexity and cost.
• Several molecular tests for the analysis of benzimidazole-resistance associated beta-tubulin allele frequencies in pooled trichostrongyle larvae DNA samples have been developed which are suitable for field use. Largely confined to research use at present due to complexity and cost.
• Currently, there are no validated molecular tests for resistance mutations for other drug classes.