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Lecture 11,ascaridida, parascaris, hetarakis
- 2. Ascaridia spp. (LARGE ROUNDWORM OF BIRDS) Definitive Host Spectrum – Chickens, turkeys etc, wild birds Intermediate Host Earthworms paratenic hosts Geographic Distribution – Worldwide Morphology – Adults - varies by species, females 20-120 mm, males 16-76 mm; 3 lips – Eggs - oval, with smooth shell, in single cell stage when laid, 73-92 x 40-60 microns
- 3. Life Cycle (Stages) – Eggs are passed in avian feces – Develop to infective larvated eggs in 10 days or longer – Infective eggs may be ingested by birds in contaminated food or water or earthworms may ingest the eggs and in turn be eaten by birds – After ingestion and hatching, larvae remain in the lumen of the intestine for about 8 days, then they spend some time in the mucosa – Larvae then mature to the adult stage – Prepatent period - varies, depending on age of host, 5-6 weeks or up to 8 weeks Site of Infection – Small intestine
- 4. Pathogenesis/Clinical Signs – Most serious in birds 1-3 months old – Larvae penetrating the mucosa cause hemorrhage and enteritis – Clinical signs - diarrhea, unthriftiness, emaciation, weakness, decreased egg production Diagnosis – Eggs in feces or worms at necropsy Treatment – Avermectins – Piperazine compounds – Benzimidazoles – Levamisole
- 5. Other Control Measures – Separate young birds from old – Rotate poultry runs – Use good ventilation, feeding and drinking troughs for housed birds – Compost litter Public Health Significance – None
- 6. Heterakis gallinarum (CECAL WORM) Definitive Host Spectrum – Chickens, turkeys, geese, ducks, wild birds Intermediate Host – Earthworms may serve as paratenic (transport) hosts Geographic Distribution – Worldwide Morphology Adults - small, males 7-13 mm, females 10-15 mm; lateral alae Eggs - ovoid, smooth-shelled, in single cell stage when laid, 65-80 x 35-46 microns
- 7. Life Cycle (Stages) – Eggs are passed in feces and become infective after the infective larva develops within – DH ingests the infective eggs directly or in an earthworm paratenic host – Larvae hatch in the intestine and reach maturity in the ceca – Prepatent period - about 1 month Site of Infection – Ceca Pathogenesis/Clinical Signs – Thickening of the cecal mucosa and petechial hemorrhages occur only in heavy infections – Important economically as a carrier of Histomonas meleagridis , the causative agent of "blackhead" of turkeys
- 8. Diagnosis • Finding eggs in feces Treatment • Avermectins in feed • Benzimidazoles in feed • Levamisole in drinking water Other Control Measures • Good sanitation Public Health Significance • None
- 9. Parascaris equorum (LARGE ROUNDWORM OF HORSES) Definitive Host Spectrum – Equids Intermediate Host – None Geographic Distribution – Worldwide Morphology Adults - large, robust, males 15-28 cm, females up to 50 cm; the 3 lips are very conspicuous – Eggs - almost spherical, brown, with a 1-celled zygote and a thick pitted shell, 90-100 microns
- 11. Life cycle » Very similar to Ascaris suum » Eggs are passed in feces » Larvated egg is infective when ingested while grazing or suckling a contaminated udder » After the larvae penetrate the intestine, they migrate through the liver, heart, lungs to the trachea and pharynx and are swallowed » Maturation occurs in the small intestine » Prepatent period - 10 to 12 weeks Sites of Infection » Small intestine, bile ducts - adults (can break out of the gut and into the peritoneum) – Liver, lungs - larvae
- 12. Pathogenesis/Clinical Signs • Clinical effects usually seen only in foals 2-6 months old (immunity develops by 6 months) – Migration produces petechial hemorrhages, eosinophilic infiltration in the liver, lungs – Adults produce catarrhal enteritis, may cause obstruction or perforation of the intestine or bile duct – Clinical signs - coughing, dirty mucoid nasal discharge, pot-bellied appearance, weight loss, poor hair coat, weakness, fetid diarrhea that is pale in color, flatulence – Lab findings - eosinophilia, lower total body albumin and serum albumin Diagnosis – Finding eggs, perhaps adults, in feces
- 13. Treatment – Ivermectin – Mebendazole – Moxidectin – Fenbendazole – Febantel – Oxibendazole – Dichlorvos – Pyrantel pamoate – Piperazine compounds Other Control Measures – Good sanitation – Clean foaling boxes, mare's udder – Turn mare and foal out into clean paddock – Collect manure and compost it or spread it on land not used as horse pasture Public Health Significance – None
- 14. Superfamily Oxyuroidea Adults oxyuroides of animals inhabit the large intestine. They are commonly called as pinworms because of the pointed tail of the female parasites. They have a double bulb oesophagus. The life cycle is direct. The only genus of veterinary interest is oxyuris which is parasitic in the horse.
- 15. Oxyuris equi (HORSE PINWORM) Definitive Host Spectrum • Equids Intermediate Host • None G. Distribution: Worldwide Morphology Adults - males 9-12 mm, females up to 150 mm long; mature females have long narrow tails which may be more than 3 times as long as the rest of the body • Eggs - elongate, flattened on one side, operculated, 85-95 x 40-45 microns
- 16. Life Cycle (Stages) • Females travel to the rectum and out the anus to lay eggs on the perianal skin • Eggs usually are rubbed off or fall on the ground and become infective • Infective (larvated) eggs are ingested by a DH • Eggs hatch in the small intestine and larvae pass to the cecum where they feed on the mucosa • Adults develop in the cecum, do not attach and are probably scavengers of the cecal contents • Prepatent period - 4 to 5 months Sites of Infection • Cecum, large colon; also rectum, perianal area for egg- laying females
- 17. Pathogenesis/Clinical Signs – The L 4 may produce inflammation of the cecal and colonic mucosa by its feeding activity – Eggs laid by female worms cause pruritis ani – Clinical signs - restlessness, loss of condition, butt rubbing, "rat tail" Diagnosis – "Rat tail" appearance is indicative of infection; eggs may be seen by using scotch tape technique • Because of their egg laying habits, adult females may be seen in feces
- 18. Treatment – Fenbendazole – Dichlorvos – Ivermectin, (will kill adults and larvae) – Moxidectin Other Control Measures – Change bedding frequently – Provide clean water – Construct feed boxes so they will not be contaminated by bedding Public significance – None