Nematodes (finish) Flashcards
Morphological features of Nematodes
- dioecious
- unsegmented but may be annulated
- outer body cover: cuticle (can have modifications)
- mouth: 2-6 lips, others may have buccal capsule; some have teeth/dentigerous ridge
- buccal cavity: connects esophagus to outside
- females: rectum/males-cloaca
- male repro: 1-2 tubular testes, vas deferens, spicule pouch, spicules, +/- copulator bursa
- female repro: 2 tubular ovaries, oviduct, uterus (100s-1000s of eggs/larvae), seminar receptacle, vagina, vulva
Female nematode classification of egg type
Oviparous- eggs contain a single stage or morula (ex. Toxocara vitulorum, strongyle, trichostrongyles)
Oviviparous- eggs contain a first stage larva (ex.- Strongyloides westeri)
Laviparous- eggs are retained within the uterus, incubated and the female ‘gives birth’ to live larvae/microfilariae (ex.- Dirofilaria immitis)
Developmental stages in the lifecycle of a typical nematode
Within the environment (free-living) or intermediate host: egg > 1st larval stage (L1) > 2nd larval stage (L2) > 3rd larval stage >
Within the definitive host: 4th larval stage > 5th larval stage (immature/preadult) > adult
List the superfamilies of Nematodes
Rhabditoidea Trichostrongyloidea* Metastrongyloidea Strongyloidea* Oxyruoidea* Ascaroidea* Spiruroidea Trichuroidea* Filariodea*
“Trichostrongyle” (HOTC) Parasites of Ruminants
Characteristics:
Hosts: Ruminants; distributed throughout North America; influenced by climate
Habitat: abomasum and small intestine
Includes Haemonchus spp., Ostertagi spp.
Life cycle: eggs shed in feces, free-living first stage larvae (L1) develop in manure to L2 and L3 while feeding on fecal bacteria. L3 migrates to herbage and ingested by animal as it grazes. In host, develops through L4 to adulthood in GI tract.
Pathogenicity: PGE
Haemonchus spp.
2 species: H. contortus (ruminants), H. placei (cattle) H. contortus most pathogenic Common name: Barberpole worm High fecal egg counts anemia (sheep/goats) Resistant to most antihelmintics
Ostertagia ostertagi
Common name: Brown stomach worm
Very pathogenic in cattle (larvae)
Loss of protein, serum increases in pepsinogen, change in abomasum pH; results in diarrhea
Type I: high egg counts, incremental to rapid onset, good prognosis with tx, diarrhea, weight loss, bottle jaw,
Pre/Type II: ingestion of L3, hypobiosis in gastric glands, 4-7 months, no clinical disease; large number of hyperbiotic larva simultaneously resume development, emerge from gastric glands destroying abomasum, uncommon, yearlings, severe PGE, high serum pepsinogen
Ancylostoma caninum
Common name: Hookworm
Host: Dog
Other spps: A. tubaeforme (cats), A. braziliense (dogs and cats)
Habitat: small intestine
Identification: Adults- medium sized, gray to red; eggs- 8-cell morula
Life cycle: attached to mucosa of the small intestine, large amount of eggs produced, pass out of intestine into feces, L1 develops within the egg, larva hatch and become free living, soon molts to L2, L3 stage is the infective stage, dog can be infected 1/5 ways
Pathogenicity: anemia, adults use anticoagulant; severity related to intensity of infection
Clinical signs: diarrhea (frank blood) or mucusy, black and tarry, poor appetite and growth
Diagnosis: fecal float, necropsy
Treatment: sanitation, pick up feces
Zoonotic: Cutaneous larval migrans
Toxocara canis
Ascarid species found in the small intestine of dog adults- large nematodes; eggs float egg with L2 larvae is infective to DH Can be: direct, prenatal, colostral, ingestion of paratenic host
Oxyuris equi
Common Name: Large Equine Pinworm
Host: Equids, worldwide distribution
Habitat: Lower colon and rectum
Identification: adult- white, thick bodied, club-shaped esophagus; eggs- asymmetrical, operculum at one end
Direct life cycle
Pathogenicity: localized inflammation, “seat itch”/summer sores
Diagnosis: tape prep-eggs around anus, clinical signs (loss of hair at tail head)
Trichinella spiralis
Host: pigs, rats, bears
Habitat: adults- small intestine, larva-striated muscle
Identification- Adults: slender worms, females produce eggs hatch in uterus, give “birth” to live larva, spirally coiled
Life cycle: females deposit larvae in intestinal wall, larvae enter lymphatics -> thoracic duct ->heart->lungs-> heart-> systemic circulation -> larvae encyst in striated muscle-> excyst when eaten by a different host-> adults mature in S.I.
Pathogenicity: clinical signs rarely seen
Infection has two phases- nonspecific signs (nausea, vomiting, fatigue, fever); eosinophilia, fevers, chills, cough, pruritis
Diagnosis: serum, muscle biopsy, ELISA
Dirofilaria immitis
Hosts: canids, felids, ferrets, sea lions, seals, and other
Habitat: adults- right ventricle, pulmonary arteries; microfilariae- prelarval stages in circulating blood
Identification- adult- long, slender, white; microfilariae- tapered at their anterior end, possess visible cellularity at head
Life cycle: microfilaria released by female worm, mosquitoes take up mff with blood meal, L3s migrate to mosquito mouth parts released when mosquito feeds, enter host through bite wound, L3s molt to L4, L4 migrate through tissues for 2-3 months, molt from L4 to L5, grow up to pulmonary arteries, right ventricle and pulmonary trunk
Periodicity: nocturnal, incomplete
Pathogenicity: disease due to presence of worms, many dogs appear asymptomatic
Diagnosis: direct blood smear, Difil test, antibody/antigen test, imaging, CBC/Chem
Potential modifications of the cuticle:
- Cervical alae: lateral, flattened cuticular expansions at the anterior end of the body
- Copulatory bursa: lateral, flattened cuticular expansions at posterior end in males, used during mating; composed of fingerlike projections called bursal rays
- Spicules: sclerotized penis
Hypobiosis
ability of nematodes to arrest their development and go dormant for a variable period of time; extends prepatent period; less sensitive to antihelmintics
PGE
Parasitic gastroenteritis
disease syndrom caused by a compex mix of predominantely trichostrongyloid nematode species in ruminants
Ruminants, camelids: Haemonchus spp.; tropical
Cattle: Ostertagi spp.
Clinical signs: weight loss, rough hair coat, anemia, diarrhea, hypoproteinemia leading to bottle jaw
Most affected; small, young, lactating
