Nematodes PDF

Lecture Objectives Nematodes – Know the key characteristics – Be able to determine if a life cycle is direct or indirect – Be able to identify the types of hosts in a life cycle – Be able to identify methods nematodes use to ensure the survival of their species – Understand the impact of grazing on...

Lecture Objectives Nematodes – Know the key characteristics – Be able to determine if a life cycle is direct or indirect – Be able to identify the types of hosts in a life cycle – Be able to identify methods nematodes use to ensure the survival of their species – Understand the impact of grazing on nematode infections – Be able to describe the balance between pasture nutrition and parasite management Lecture Objectives Ancylostoma caninum – Know the primary clinical signs – Know the primary modes of infection – Be able to relate morphology & behaviour to pathology and clinical signs Parasites of veterinary importance Phylum Nematoda (Roundworms) Phylum Platyhelminthes (Flatworms) – Class Cestoda (Tapeworms) – Class Trematoda (Flukes) Helminth = worm Live extracellularly: in the gastro-intestinal tract and organs Helminths Sexual reproduction – Nematodes: Males and females – Cestodes & trematodes: hermaphroditic – Egg-laying (oviparous); some lay live young (viviparous) Do not multiply within the host sexual reprohappens in histidine Tempting – Offspring must leave host host to multiply – Some cestode larval stages an exception Increased infection results from increased environmental exposure Nematodes (roundworms) Free-living or parasitic – Soil and plant nematodes – Animal nematodes Elongate/cylindrical Alimentary canal present Sexes usually separate – Egg-laying (oviparous); some lay live young (viviparous) – Do not multiply within the host – Offspring must leave host Increased infection results from increased environmental exposure Life cycle direct or indirect Helminths Courtesy Elanco Nematodes (roundworms) (www.simplerecipes.com) Round -- Elongate/cylindrical Nematodes (roundworms) Photo: J. Ketzis Round -- Elongate/cylindrical Nematodes (roundworms) Ancylostoma caninum Buccal cavity Large Strongyles causesblood primaryfood blood primarysymptoms anemia esophagus intestines e Photo: RUSVM Photo: J. Ketzis Alimentary canal present Nematodes (roundworms) Alimentary canal present Photo: J. Ketzis Nematodes (roundworms) Astrids must be held at a great Alimentary canal present Sexes usually separate distance Female nematodes fingernails appendage Photo: CSIRO Male nematodes Burser RUSVM, 2006 Nematodes (roundworms) Mammomonogamus spp. male and females stay in copulation for the rest of their life male smaller than female Photo: J. Ketzis Nematodes (roundworms) Cross-section through Ascaris d.n. Dorsal nerve n.c. non-contractile portion of muscle cells c. Cuticle e. Epidermis l.l. lateral line e.v. excretory vessel m. contractile portion of muscle cells v.n. ventral nerve ov. Ovary ut. Uterus g. gut Clipart courtesy FCIT http://etc.usf.edu/clipart Thomson, 1916 Nematodes (roundworms) Spirocerca lupi larva in wall of thoracic aorta Nematodes (roundworms) Bursate (male) or not Vulva Mouth (shape, teeth) Esophagus Size Aids in identification Lecture Objectives Nematodes – Key characteristics alimentary canal round – Life cycles – Hosts – Means of species survival Ancylostoma caninum sexualrepro Nematodes – life cycle E – (mff) L1 - L2 - L3 - L4 - L5 - Adult – Pre-L1 = microfilaria (some nematodes) mff released from those that – L5 = immature adult Insert host(s) – Final or definitive if the femalelays LI egg liveyoung – Intermediate – Vectors, paratenic, etc. Insert mode of infection (per os, percutaneous, transmammary, transplacental lay liveyoung an egg Ll LI of microfilariae Nematodes – life cycle Life cycle Direct – infective larva (usually L3) – infective larva in an egg (usually NOT L1) Indirect – L1 infective to intermediate host – L3 to the final host NematodesDirect – life In feces L1-L2-L3 Does Host not life lycle the In grass In feces Batches out cycle in diagnosticstage in D can move where the host is located L3 fecalmatter 3 leaves matter what and entershost looks like L3 infective stage L3-L4-L5-Adult-eggs leaves in egg feces autopsy you would identify adult worm In an Nematodes –Direct life cycle In feces In feces In grass L1 L1-L2-L3 L3 Larvae is in feces Host diagnostic stage Does not matter the egg looks like what L3-L4-L5-Adulteggs-L1 in egg-L1 Ll develops inside ofegg Still inside of the host Ll leaves thehost in feces I P ing g il g Nematodes – life cycle Insert means of survival How they ensure offspring get in a host – – – – Survival of eggs with larva Paratenic hosts Transmammary, transplacental Periparturient rise in and aroundwhenanimal ishaving a baby Avoid immune system/crowding/“badweather”: – Arrested development/Hypobiosis/Inhibited worm more development eggs bigger Nematodes – life cycles common parasite Direct Diagnostic stage egg in feces PH must be egg consumed in theinfective stage Courtesy Elanco Nematodes – life cycles INDIRECT uncommon DH parasite diagnostic stage larva in Feces LI PHEE Courtesy Elanco IH Nematodes – life cycles could ensure protectionby burrowinginto the dirt production of thousands of L3 egg Novartis Animal Health Nematodes – life cycles Some can survive on pasture in winter Some have to find another means of making the pasture infected – arrest and emerge in spring; periparturient rise Life cycles Peripartuient 23 can survive 60 90 days the environment seesick lambshere lambs in consume the adult The longer it for the takes egg to become it is more likely to arrest after ingestion periparturenic rinse can be cult in half by moving lambs sick lambs Trichostrongyle fecal egg counts; ACSRPC hummer in late caused by Peruatuirenic rise in 34 I can sepro Nematodes – life cycles strongerimmunity developingimmunity ‘immune exclusion’ or rapid larval rejection L3s gone in 48 h Hypersensitized sheep; previous exposure IgE, increased peristalsis of the gut Delayed rejection L3s enter mucosa and eventually die Naive sheep babies Eosinophil-mediated larval killing (antibodydependent cell cytotoxicity) 35 Nematodes – life cycles L3 exsheaths and now L4 Crowding; adult excretion = arrests Older L3 = slower development = inhibited Immune protection = arrests Immune protection = regulates feeding Small L4 Small adult Fewer eggs 36 Nematodes – life cycles Spring time! L4 resume development after a few months (regardless that it is spring) Spring rise in egg count, periparturient rise results in all New L3 cause “self-cure” or premonition Payytes Hypobiosis as a winter strategy is a potential misconception Arrested larva in dogs cats arrest occurs due to When Alternate theory environment hypobiosis Ewes lose immunity around lambing (-2 - +8 wk) Results in higher infection 37 Nematodes – life cycles Nematodes in ruminantshave preference tump to survive good at ie of hypobiosis why large eggs in the springtime Some can survive on pasture in winter Some have to find another means of making the pasture infected – arrest and emerge in spring; periparturient rise Life cycles could calves put on pasture not used during grazingseason put older animals there calves to protect Urquhart et al., 1996. Veterinary Parasitology, 2nd edition. Blackwell. pp3914 Nematodes – life cycles Epidemiology – when exposure occurs – when heavy infections occur – when there is the most pathology & clinical signs – how to intervene Usefulness of fecal egg counts counts related to worm mass most egg not Take home message: if you know how the species perpetuates, you can know how AND WHEN to intervene! Nematodes – life cycle E - L1 - L2 - L3 - L4 - L5 - Adult – L1 = mff; L5 = immature adult Insert host(s) – Final or definitive – Intermediate – Vectors, paratenic, etc. Insert mode of infection (per os, percutaneous, transmammary, transplacental Insert means of survival Nematodes – Pastures What ways do parasites enable the survival of their species peripartenic rise and Animals on pasture in spring Animals in barn in winter Pasture rotations to maximize nutrition Often 30 days – depends on weather, stocking rate, time of year, type of pasture Nematodes – Pastures Eggs to L3: a few days to a few weeks L3 life span a few weeks to 3+ months L3 accumulate Day 1: 100 eggs; Day 2: 100 eggs; Day 3: 100 eggs, etc. Day 7: 100 L3, Day 8: 200 L3; Day 9: 300 L3, etc. On pasture for 30 days: all the L3 from eggs deposited in previous 23 days and, in 7 more days, all L3 from all 30 days Lecture Objectives Nematodes – Know the key characteristics – Be able to determine if a life cycle is direct or indirect – Be able to identify the types of hosts in a life cycle – Be able to identify methods nematodes use to ensure the survival of their species – Understand the impact of grazing on nematode moreexposure infections – Be able to describe the balance between pasture nutrition and parasite management Lecture Objectives Ancylostoma caninum – Know the primary clinical signs – Know the primary modes of infection – Be able to relate morphology & behaviour to pathology and clinical signs Ancylostoma caninum Round; elongated; males and females Buccal cavity – anything for ID? Size? Bursa? Host? Mode of infection? Prediliction site? Food? Life cycle? Ancylostoma caninum Round; elongated; males and females Buccal cavity – teeth Size – 1-2 cm Bursa -- yes Host – caninum = dogs Mode of infection – many modes Prediliction site – adults small intestines; larvae migrate in lungs Food – adults blood Life cycle -- direct Nematodes – Ancylostomatoidea Adults: small (1-2 cm); characteristic hook appearance; bursa; small intestine Attach to the intestinal villi with large mouth (buccal) cavity Caryn Ehrhardt (males; stained) Thomas Nolan Ancylostoma caninum PPP: 2-3 wk DIRECT I parasite on St Kitts Anthelimtic resistance Anemia 13 can migrate thru lungs bronchill Paratenic hosts Elanco Ancylostoma caninum Life cycle: Direct Five modes of infection – Percutaneous or penetration of oral mucosa – Per os – Paratenic hosts (e.g., rodents) – Transplacental (rare) – Transmammary (important) Arrested development Lung migration Ancylostoma caninum Pathogenesis and lesions for acute high of adults Acute or chronic hemorrhagic anemia Moist eczema with percutaneous infection Acute infections clinical signs Anemia and lassitude Respiratory disease (larval migration); pneumonia Diarrhea (blood and mucus) Chronic infections clinical signs warmer tropical climates Weight loss, poor hair coat etc.) Ancylostoma caninum Photo courtesy of Noah’s Archive Nematodes – Ancylostomatoidea Hemorrhaging Anemia Photo courtesy of Dr. Thomas Nolan Nematodes – Ancylostomatoidea Eggs: oval, thin shelled; 60 X 40 µm average size Photo: Zajac and Conboy, 2012 Ancylostoma caninum Diagnosis: Clinical signs important in animals less than 14day Fecal examinations only useful in 14 days older A few hookworm eggs confirms infection (-iasis) only, not hookworm disease L4 / early mature also feed on blood or Cutaneous larval migrans (CLM) ZOONOTIC (Photo RC Krecek) (Photo courtesy of A Gessner, 2008) Nematodes – Ancylostomatoidea Summary Hookworms mayhffmical I signAdults: 1-2 cm; small intestine Buccal capsule modifications: teeth, cutting plates Anemia: feed on blood; ulcers Pneumonia: larval migration Eggs: oval, thin shelled, 60 x 40 µm Young animals most severe signs Limited immunity Zoonotic (cutaneous larval migration) Impact of parasites Blood feeding Hoste et al. 2016. Interactions between nutrition and infections with Haemonchus contortus and related gastrointestinal nematodes in small ruminants. Advances in Parasitol 58 Nematodes Trematodes Cestodes Wrinkles = segments Little pieces = segments