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29 Cards in this Set
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- Back
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worms in cats and dogs
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Toxacara (canis and cati) Diplydium caninum Taenia spp Echinococcus granulosis Angiostrongylus vasorum Dirofilaria immitis |
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Toxacara canis + cati
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Ascarid (roundworms) – large, white worms Mild – moderate infections in adults don’t usually cause much harm, but severe infections can lead to pneumonia and intestinal blockage. Infected pups/kittens usually have pot-bellies, ill-thrift and some diarrhoea. If infected in-utero, lung damage can cause death within a few days of birth. Severe zoonotic potential |
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Toxocara Canis and cati life cycle
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Mature worms in the small intestine 4 weeks to develop to larval stage May be eaten by paratenic hostor Ingested eggs hatch in the small intestine Larval migration in children can cause blindness Adults’ immune system arrests migration, immobilising larvae in tissues Reactivation during pregnancy, larvae cross placenta and mammary glands In young, larvae migrate to lungs, coughed up and swallowed |
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Diplydium caninum life cycle
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Adult worm in dog or cat Active tail segments (proglottids) released into faeces Eggs released and ingested by flea larvae or louse Develop in flea abdomen to form metacestodes Flea eaten by dog/cat Metacestodes develop into adult worms |
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Taenia and echinococcus
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Adult worms live in small intestine Proglottids released and passed out with faeces Eggs released from proglottid and eaten by intermediate host Digestion of egg capsule activates onchosphere Onchosphere migrates through blood or peritoneum Develops into metacestode cyst Cyst-infected flesh eaten by definitive host |
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Echinococcus granulosus
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Dog is definitive host, shed 1 segment/weekSheep common intermediate host, also other ruminants, pigs. Equids are resistant. Humans are an incidental host to the metacestode stage (hydatid disease) Onchospheres have long environmental survival (2 years) Metacestodes are slow-growing (<1yr) |
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Hydatid disease in humans
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Ingestion of tapeworm egg Invasion of tissues and formation of metacestode cysts Commonly liver and CNS |
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Angiostrongylus vasorum
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Metastrongyle worms – canine lungworm Adults live in the right ventricle and pulmonary arteries L1 penetrate alveoli and are coughed up, swallowed and passed out in faeces Develop to L3 in gastropods Ingested by definitive host (dog) and migration through blood stream Pathology: pulmonary pathology from migration, coagulopathies |
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Aelurostrongylus abstrusus
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Metastrongyle worms – feline lungworm Similar lifecycle to Angiostrongylus; gastropod intermediate host Adult and larvae live in lung parenchyma Mild clinical signs |
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Dirofilaria immitus
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Canine heartworm Adults live in the heart and major vessels (right side)-> Release microfilariae into blood-> Ingested by mosquito-> Develop to L3 which reside in the mouthparts-> Infest dog when bitten Cycle takes 6 months, adults can live for 2-5 years Heavy infestations cause obstructive heart failure and endocarditis Killing adult worms can cause pulmonary embolisms |
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Ostertagia spp
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Affects cattle & sheep (species specific) Direct lifecycles Can have hypobiosis stage |
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Ostertagia
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Type I ostertagiosis: disease from larvae ingested 3-4 weeks ago (no hypobiosis) Diarrhoea High morbidity, low mortality Type II ostertagiosis: disease from emerging larvae (ingested 6 months ago Diarrhoea, anorexia, protein loss -> oedema Low morbidity, high mortality |
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Moniezia
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Anoplocephalidae tapeworms Adults >2m long Proglottids release eggs onto pasture Eaten by forage mites Develop into cysticercoids in mites, which are eaten by a ruminant Usually asymptomatic |
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Echinococcus granulosus
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Ruminants are intermediate host Cysts develop in muscle and CNS Eggs survive up to 2 years on pasture Life cycle Adult worm in dog intestine Releases eggs in faeces Onchosphere released from egg, penetrates intestinal wall Metacestode stage: cysts form in muscle Proscolex released from cyst and attaches to intestinal wall |
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Fasciola hepatica
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Flukes Adult flukes live in bile ducts Immature flukes migrate through parenchyma Egg development is temperature dependent (>10◦C) Miracidium penetrate snail (lifespan 3 hrs) 1 miricidium = >600 metacercariae Migrate via peritoneal space through liver capsule |
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Dictyocaulus viviparus
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Cattle lungworm (Husk) Adults live in the bronchi, larvae travel up the trachea, are swallowed and passed with faeces Moult to L3 on pasture, dispersed via fungus, then ingested Penetrate intestinal wall and travel to alveoli via the bloodstream. Affects first-grazing calves in SummerLarvae in alveoli cause most damage – coughing, bronchitis and lung collapse Prolonged recovery, some permanent lung damage Strong natural immunity develops, vaccine is available |
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Paramphistomum
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Rumen flukes Adults live in the rumen and reticulum Lifecycle similar to liver fluke, immature flukes live in the duodenum then migrate forward to the rumen as they mature Adults cause no damage, but young flukes are plug feeders, so heavy infestations can cause oedema, haemorrhage, diarrhoea, weight loss and death. |
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Strongylus spp
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Horses Large redworms (S. vulgaris, S. edentatus, S. equinus) Adults live in large intestines, are active feeders Direct lifecycle, 1-2 weeks for eggs to mature Extensive larval migration, esp S. vulgaris pathology: Blood loss, Diarrhoea, Weight loss and weaknessThromboembolismColic, stasis, torsions |
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Cyathostomes
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Horses Small redworms (>40 species) Adults live in large intestine, active feeders but smaller than Strongyloides Direct lifecycle (2 weeks for eggs to mature) L3 invades intestinal mucosa (no deeper migration) and develops to L4 -> adult Hypobiosis of L3-4 in some species Pathology Less severe than large worms due to buccal size Extreme burdens can reduce mucosal efficiency Larval Cyathostomiasis: Sudden, mass emergence of larvae from hypobiosis Severe protein loss and inflammation |
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Parascaris equorum
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Ascarid – large white worms in horses Adults live in small intestine Direct lifecycle, 10-14 days for egg maturity Larvae migrate through liver to pulmonary circulation, penetrate lungs, coughed up and swallowed. Adults cause illthrift, especially in foals. Heavy burdens can cause impactions Larvae cause liver and lung pathology |
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oxyuris equi
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Pinwormsin horses Adults live in the colon Female lays eggs directly out of anus onto perineal skin Mature to L3 on skin, ingested and migrate into LI mucosa Emerge as adults Adults cause little pathology L4 can cause mucosal erosions Pruritis -From adult female laying eggs |
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Dictyocaulus arnfieldi
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Lungworm in horses Donkeys are definitive host, horses incidental Adults live in the bronchi Eggs/larvae coughed up and swallowed, passed out in faeces2-3 weeks to mature Can survive mild winters on pasture |
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worms in rabbits
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Roundworms (direct lifecycle) Strongyles Trichostrongyles Metastongyles Tricurids Ascarids Ascaroides Pinworms Filaroides Dirofilaria Tapeworms – host to Taenia pisiformis (dogs) |
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Diagnosis of worms
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Visualisation Large wormsTapeworm segmentsPinwormsClinical signs DiarrhoeaWeight lossRight sided heart enlargementCoughing Faecal testing Plain microscopyMcMaster techniqueBaermann techniqueFlotation method Sedimentation method Filtration technique Dependent on active adult worms Post-mortem Direct visualisation of worms on intestinal mucosaPetechiae and erosionsHistology |
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Epidemiological triad
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Disease Host Agent Environment |
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Control of worms
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Use triad Blocking one part of the lifecycle can give you control Agent control - Antihelmintic pharmaceuticals Administration Oral Topical Environmental control Stop/reduce transmission Hygiene Pick up faeces, stocking densities Know which environmental conditions affect transmission and time drug use around thisIntermediate host control Reduce host stress factors Host Control Nutrition / stress Ensure immunocompetency Control contact with transmission paths Vaccination Breed for resistance |
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Individual v's Herds
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Factors when treating individuals (eg. companion animals) Disease to individual is a priority Zoonoses!!! Close contact with owners, risk to children Environmental sharing is less concentrated Aim is to remove all parasites Priorities when treating herds Loss of productivity is the priority Less of a zoonosis risk Environment shared in large numbers and close contact Aim is to keep parasites to a manageable level |
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Anthelmintic resistance
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The use of anthelmintics selects for resistant worms Attempting to eliminate all worms has lead to the development of whole populations of resistant worms New worming guidelines for pasture-grazed animals SCOPS, COWS Eliminate the risk of underdosing/ineffective dosing Weigh the animal (weigh the largest in the group) Measure equipment Check administration technique Ensure correct drug storage Avoid introducing resistant worms (quarantine drenching) Use a wormer that works- Do wormer resistance tests every few years In sheep, more regular worming is needed due to greater impact. Still want to reduce development of resistance Instead of removing all worms, keep a reserve population of susceptible worms alive Don’t worm the best 10% of the flock Don’t move straight to clean pasture Change the class of wormer regularly |
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Fecal Egg Count
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Cattle and Horses checking for anthelmintic resistance when it is necessary to worm |
