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43 Cards in this Set
- Front
- Back
What is the main superfamily of Horse Nematodes? |
STRONGYLIDAE - Cyathostominae (small red worms) = resistant to anthelmintics - Strongylinae (large red worms) = sensitive to anthelmintics |
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Highly prevalent - Direct, NON-MIGRATORY life cycle - Propensity for arrested development (months-years) - Low host immunity - Principle parasitic pathogens of equidae in developed world - PPP 5-12 weeks |
CYATHOSTOMINAE |
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Cyathostomin Life Cycle? |
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Disease symptoms due to reemerging arrested larvae. |
CYATHOSTOMIN |
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CYATHOSTOMINOSIS |
Protein losing enteropathy - Diagnosis: Fecal larvae, NOT eggs - Seasonal: Late winter/spring - Often occurs post anthelmintic dosing for control program because clearing away adult worms clears away negative feedback on the arrested larvae and triggers reemergence |
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The majority (80%) of parasites are often present in the minority (20%) of the host population.
True or False? |
TRUE |
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Low prevalence in developed world - Direct, MIGRATORY life cycle - Migratory larval stages are highly pathogenic - Adult stage are plug feeders - All host stages susceptible to modern anthelmintics - Variable but reasonable host immunity - PPP 6-10 months |
STRONGYLINAE (large strongyles) |
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Which horse parasite life cycle is shown below? *Hint - disease symptoms due to migration of larvae through arteries. |
STRONGYLUS VULGARIS |
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Large vs Small Strongyles? |
LARGE STRONGYLES (strongylus): - Long (PPP ~6 months) migratory life cycle - Larval stages pathogenic & extremely sensitive to modern anthelmintics SMALL STRONGYLES (cyanthostomins): - Short (PPP ~8 weeks), non-migratory life cycle - Propensity for prolonged arrested development (>2 years) - Arrested larval stages refractory (unaffected by) to anthelmintics |
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Strongyle Epidemiology? |
- All ages of horse potentially contaminate pasture - Common in temperate regions - UK Peak pasture infectivity mid/late Summer - Prolonged dry heat lethal to pasture larvae |
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What are common problems with equine parasite control? |
1. Frequent on-movements of horses 2. BW of individual horses often not known so not treated with proper dosage leading to resistance |
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What is proper protocol for parasite control in horses? |
1. Test animal pre-worming to ensure there's a burden worth treating, otherwise treating without reason can lead to resistance. - Monthly FWEC (fecal worm egg count) all animals 2. If FWEC "positive" (>200epg) than dose; ensure dosing is appropriate for weight of horse |
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_________________ are the most common wormers used in horses and there's some level of resistance developed in 100% of worms. |
BENZIMIDAZOLES |
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What are the four main anthelmintics used in horses? Resistance? |
1. Benzimidazoles --> Cyathostomins resistant 2. Pyrantel --> Cyathostomins resistant 3. Ivermectin --> ascarids possibly resistant 4. Moxidectin --> Cyathostomins resistant |
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The proportion of parasites not exposed to anthelmintic chemical compound at points when animals are dosed is said to be _____________. |
REFUGIA |
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What are the three main refugia groups (not exposed to anthelmintic when animals are dosed) of Cyathostomin? |
1. Eggs in feces (L1s) 2. Eggs in pasture (L2-L3s) 3. Arrested L3s within host |
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Anthelmintic resistance is a genetic feature of the ___________________ population. |
PARASITE |
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Multi-drug resistance in cyathostomins to all 3 major anthelmintic classes (benzimidazoles, pyrantel salts, & macrocyclic lactones).
True or False? |
TRUE - so important to test for resistance of worms before worming (FEC Reduction Test) |
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Describe the Fecal Egg Count Reduction Test. |
1. Day 0 = Take FEC 2. Treat with anthelmintic 3. Day 10-14 = retake FEC
<90% reduction indicates resistant worms. |
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What are the main parasites of concern in Equine Parasite Control? |
1. Cyanthostomins 2. Tapeworm - Either target dose on basis of serology or annual inclusion of praziquantel dose (combo products) 3. Ascarids (foals & weanlings) 4. Bots - Ivermectin during Winter - Can combine with tapeworm dose 5. Strongyles (large) |
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What are some best practice techniques for equine parasite control aside from proper dosing with anthelmintics? |
1. Monitor anthelmintic resistance 2. Mixed species co-grazing (sheep/cattle with horses) 3. Harrowing - Caution: only done during dry, hot conditions when parasites can't survive, otherwise you'll just spread the parasites around. 4. Practice pasture hygiene (e.g. mowing and gathering pasture clippings; poop scooping) |
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Describe Parascaris equorum. |
ASCARIDOIDEA - Resemble typical ascarid = large (~40cm), white, round worms - Predilection for duodenum & prox. jejunum - Immunity develops with age so high burdens more common in foals and yearlings - Infection rates decrease from 6 months onwards - Clinical signs: unthriftiness - Typical direct ascarid life cycle |
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Life Cycle of parascaris equorum? |
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Pathogenesis of parascaris equorum? |
MIGRATING LARVAE cause damage to: - Liver = focal hemorrhages and fibrosis - Liver = focal hemorrhages, lymphocyte infiltration, nodules
ADULT WORMS in intestines = little pathology - Rarely, heavy worm burdens cause impaction, perforation, peritonitis |
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Clinical signs of parascaris equorum? |
More commonly seen in foals & yearlings (adults show age immunity) 1. Unthriftiness - due to adult worms in LI 2. Coughing, +/- greyish nasal discharge & runny nose (foals) |
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Parascaris equorum diagnosis? |
1. Clinical signs/history 2. FEC (tens of thousands pg) - Sensitive for ascarids (high fecundity) 3. Eosinophilia - transient in migratory phases of infection |
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What parasite eggs are these? |
PARASCARIS EQUORUM - Typical ascarid appearance |
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Epidemiology of parascaris equorum? |
- Foal -> Foal disease - Adult horses can act as carriers, but not major source of contamination. - Female worms extremely fecund - Eggs very resistant (survive several years) & sticky - Eggs build up on pasture towards end of Summer |
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Treatment/control of Parascaris equorum? |
Control measures aimed at small strongyles (Cyathostomins) should effectively control parascaris - Check for worm burden before treating and dose to BW - Adequate pasture management and hygiene important - Still sensitive to benzimidazoles but reports of ivermectin and pyrantel resistance. |
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Strongyloides westeri |
WORLDWIDE - Adult worms <1 cm - Only FEMALES are PARASITIC - Reasonably common in foals (<6 months old) - PPP = 8-14 days - Routes of entry: skin penetration or ingestion (infection of foals via transmammary route) |
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Clinical signs of Strongyloides westeri? |
* Only seen in very young animals (few weeks old) & requires heavy worm burden! 1. Unthriftiness 2. Diarrhea 3. Anorexia 4. Dullness 5. Reduced weight gain |
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Diagnosis of strongyloides westeri? |
1. Clinical signs 2. Larvated eggs in feces (smaller than strongyle egg) * High egg counts can be seen in healthy animals...
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Epidemiology of strongyloides westeri? |
Free-living L3s not very resistant (not sheathed like ascarids) - Require warm, wet conditions - Transmammary route important: successive progeny of same dam often show heavy infections. |
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Describe the characteristics of oxyuris equi? |
PINWORMS - Predilection for LI - L3 in egg is infective - PPP = 5 months
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Life cycle of Oxyuris equi? |
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Clinical signs of oxyuris equi? |
Adults in LI rarely produce clinical signs. - Egg laying activity can cause intense perineal irritation resulting in: - Rubbing - Alpecia/inflammation over rump & tail head |
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Diagnosis of oxyuris equi? |
1. Clinical signs 2. +/- eggs around the perineal (anal) region (usually not in feces) 3. Scraping plus microscopic examination of eggs 4. ADULT WORMS in feces |
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Which type of parasite egg is this? |
OXYURIS EQUI - 80-95 um length - yellow, ovoid - One side flatted - Mucus plug at one end |
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Epidemiology of oxyuris equi? |
- Infective L3 in egg can develop on perineal skin - Usually flakes of skin with eggs rubbed off - Little immunity to reinfection - Heavy burdens can build up in infected stables |
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Control of oxyuris equi? |
Susceptible to many broad spectrum anthelmentics - May be some resistance to ML compounds - KEEP ENVIRONMENT CLEAN! |
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Habronema microstoma - Host? IMH? Site? Route of infection? |
HOST: Horses, donkeys IMH: Muscid flies SITE: Adults in stomach ROUTE OF INFECTION: L3 from fly usually swallowed by horse and adults develop in stomach |
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Effects of Habronema microstoma infection? |
SUMMER SORES - Cutaneous infestation by the L3 of Habronema or related parasite, draschia - L3 deposited in skin, often around eyes by flies when stimulated by temps within 1-2C of body temp - No further development via cutaneous cycle of infection. * Associated with warm weather & often dark coated horses. |
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List the equine nematode parasites of importance to specific age groups and their age group. |
1. Parascaris equorum = foals & yearlings 2. Strongloides westeri = very young foals |