Parasitology

• Ectoparasites are parasites that inhabit the body surface, such as the skin or hair.
• Pasture borne helminths of livestock include nematodes, trematodes, cestodes, and platyhelminthes.
• Nematodes are helminths that are worm-like eukaryotic parasites, with approximately 12,000 species.
• Trematodes are flukes, with approximately 1,500 species.
• Cestodes are tapeworms, with approximately 7,800 species.
• Platyhelminthes are flatworms, with approximately 4,000 species.
• Cylicocyclus nassatus, Cyathostomum catinatum, and Cylicostephanus longibursatus account for 70-80% of the ≈40 species of which ≈10 are common.
• Adult worms develop in the small intestine, copulate and start to produce eggs.
• The level of anthelmintic resistance in Cyathostomins is not region-related.
• Parascaris univalens has a life cycle where eggs are passed in faeces, develop into the infective stage within 2 weeks, and can remain viable for several years.
• Cyathostomins are non-migratory and inhibited larvae are common in adult horses.
• Cyathostomins have a seasonal dynamics with Cyathostominosis being the most common symptom.
• Larval cyathostominosis is characterized by a mass emergence of L4s in young horses, usually seen in late winter-spring.
• Cyathostomins have a general life cycle with three stages: egg, third-stage larvae, and adult.
• Cyathostomins have a regional distribution with 50% found on establishments in the south of the country.
• Symptoms of larval cyathostominosis include weight loss, sudden onset profuse diarrhoea, and oedema.
• Parascaris (equorum) univalens is an increasing problem in foals in Sweden.
• Cyathostomins have an age-dependent immunity with prevalence of Parascaris univalens increasing with age.
• Cyathostomins are caused by Strongylus vulgaris, the most pathogenic strongylin, which migrate in arteries.
• Immature eggs in faeces are L3 passed to the trachea and are swallowed.
• Cyathostomins cause mild inflammatory enteropathy with sub clinical symptoms being the most common.
• Helminths have existed for over 370 million years and inhabit all ecosystems, both parasitic and free-living forms.
• Nematodes are characterized as vermiform, multicellular, pseudocoel, with a nervous system, a cuticle, and a pharyngeal nerve ring.
• There was no indication that the level of IVM resistance as measured by the faecal egg count reduction test was higher on farms with high FA.
• Based on these results, dyf-7 is not a suitable marker for field testing of IVM resistance in Haemonchus contortus.
• The FA was generally stable in samples collected from the same farms, even though they were obtained on different occasions up to 25 months apart.
• By comparing FA in samples from the same farms pre- and post-IVM treatment, there was no evidence of a correlation between dyf-7 and level of IVM resistance.
• The fractional abundance (FA) of the mutant SNP was within the range 7.8 and 31%.
• The same sets of primers and probes were used in a droplet digital PCR (ddPCR) assay for precise quantification of dyf-7 allele frequencies in pre- and post-anthelmintic treatment faecal larval cultures.
• The sequence data was used to create a haplotype network.
• Nematodes of horses have an internal body plan with a gut, no circulatory system, and are dioecious with X & Y chromosomes.
• Nematodes have a life cycle that can be direct or indirect.
• Trichostrongyloidea are parasites of ruminants with a life cycle that is direct and infects with L3.
• Targeted selective treatments (TST) involve treating only individual animals within the grazing group based on a single, or a combination of, treatment indicators, such as faecal egg count (FEC), weight gain, milk yield and body condition score.
• Parasites in refugia are not exposed to anthelmintics, are part of the free-living part of the life cycle, and their mucosal stages are not affected by the drug.
• The larger the refugia population, the more slowly resistance develops.
• A major shift in mentality will be required to make these approaches common practice in parasite control.
• Targeted treatments (TT) and targeted selective treatments (TST) are ready to be used and provide practical benefits today.
• Targeted treatments (TT) involve treating the whole flock/herd based on knowledge of the risk, or parameters that quantify the severity of infection.
• Research practices to optimise gastrointestinal nematode control on sheep, goat and cattle farms in Europe include the use of targeted treatments (TT) and targeted selective treatments (TST).