Nematodes: roundworms, pinworms, whipworms Flashcards
Name 3 Superfamilies of non bursate nematodes.
Ascaridoidea
Oxyuroidea
Trichuroidea
Superfamily (non bursate nematodes) Ascaridoidea:
includes which genera?
Direct or indirect life cycle?
Infection by what stage of larvae?
Ascaris, Toxocara, Parascaris etc.
Large white worms.
Life cycle direct, infection by L2/L3
Superfamily (non bursate nematodes) Oxyuroidea:
includes which genera?
Direct or indirect life cycle?
Infection by what stage of larvae?
Oxiuris, Skrjabinema
Female has long pointed tail.
Life cycle direct, infection by L3
Trichuroidea:
includes which genera?
Direct or indirect life cycle?
Infection by what stage of larvae?
Trichuris, Capillaria
Whip-like or hair-like worms.
Life cycle direct or indirect, infection by L1.
The largest nematodes belong to which order?
Ascaridida
Name the 4 main genera belonging to Ascaridida?
Ascaris
Parascaris
Toxocara
Toxascaris
(Heterakis
Askaridida)
Main host of Ascaris suum?
pig
General morphology of roundworms:
Simple mouth:
* 3 large lips
* Small denticles on each lip
* No buccal capsule
Males are slightly curved posteriorly.
Males have two spicules, no bursa.
Eesophagus is bulb shaped (some don’t have).
Eggs are very resistant, thick-shaped, zygote or larva inside.
Morphology of Parascaris equorum?
Male: up to 28 cm
Female: up to 50 cm
- 3 heart shaped lips
- Lips separated from body by a deep
transverse groove
Morphology of Ascaris suum?
Female: up to 40 cm
Male: up to 25 cm
- Large spicules
- No bursa
- No cervical alae
Morphology of Ascaridia galli?
Male: 3-7 cm
Female: 7-11 cm
- 3 lips
- Lips have denticles
- Male tail has posterior alae
Morphology of Heterakis gallinarum?
Female: 6-11 cm
Male: 8-11 cm
- 3 lips
- Body has lateral alae
Morphology of Toxocara canis?
Male: 8-13 cm
Female: 12-18 cm
- Large lanceolate cervical alae and caudal alae
- Male tail has narrow appendage
- Anterior body curved ventrally
Morphology of Toxocara cati?
Male: 3-7 cm
Female: up to 12 cm
- Striated cervical alae shorter and wider than in T. canis (cobra)
- Male tail has narrow appendage
- Ant. body curved ventrally
Morphology of Toxocaris leonina?
affects both cats and dogs
Male: 4-6 cm
Female: 7-10 cm
- Long, thin cervical alae
- Male tail is simple
- Anterior body curved dorsally
Life cycle of Ascaaris suum in general
Direct + reservoir/paratenic hosts
Larva develops inside an egg (L2 or L3).
Larva hatches inside the final host small intestine.
Larva migrates via hepatopulmoenteral system.
Few moults in the final host, last moult in intestines.
In some hosts:
*Transplacental and intrauterine migration
Paratenic hosts: the egg hatches and L3 larva travels to tissues from gut lumen – remains infective for several years.
Life cycle of Parascaris equorum
Direct and migratory cycles:
Infective stage: L2 in egg,
Egg development is fast – 2 weeks.
Prepatent period 10–16 weeks
Longevity is up to 2 years
No evidence of prenatal infection.
identify
Eggs of Parascaris equorum are 90-100 µm
with a thick, rough shell.
identify spp.
Egg of Parascaris spp. in a fecal flotation from a horse.
Describe eggs of Ascaris suum.
Eggs: zygote or larva inside, round, brownish, thick-shelled)
Which common nematodes spp. are zoonotic?
Toxocara canis
Toxocara cati
Life cycle of Toxocara canis
4 main transmission ways in dogs:
* eggs, that have L3 stage larvae
* Transplacental migration
* Lactogenic - no migratory phase, puppies (when 3-4 weeks old) can already shed eggs of T. canis
* Reinfection from puppy feces
Hepatopulmoenteral migration until 3 month old puppies, later somatic migration and hypobiosis – in liver, lungs, heart, brain, muscles.
Pregnant bitch – prenatal infection - 3 weeks before parturition - transpacental transmission – larvae in fetuses lungs.
Paratenic host of Toxocara canis?
Mice
Paratenic host = “An optional intermediate host is one which the larvae usually enters passively, along with ingested food.” Development of parasite does not occur in this intermediate host.
Life cycle of Toxocara cati
In cats:
* Migratory phase – infection from L2 in egg.
* Paratenic host – larvae migrates to the stomach wall, returns to the stomach and matures in the small intestine (enteric migration).
* No migratory phase as in lactogenic infection with L3 (in kittens).
Lactogenic transmission to kittens
No transplacental transmission
Prepatent period in egg infection (before eggs are shed in the feces) is 8 weeks.
Longevity up to 6 months.
Name some differences in the life cycles of Toxocara canis and cati.
Transplacental transmission is possible in dogs as well as lactogenic.
Only lactogenic is possible for vertical transmission of T.cati in cats.
Toxascaris leonina
Definitive hosts:
Paratenic hosts
Definitive hosts: dogs, cats
Paratenic hosts: rodents
Life cycle of Toxascaris leonina
Infectious stage: L2 larva in egg.
Paratenic host infected with L3.
Eggs develop outside fast!
- 1 week (Toxocara species 4 weeks)
No migratory phase
- larva is in small intestine wall for two weeks, then moults
Prepatent period: 10-11 weeks
identify spp.
Toxascaris leonina eggs
Infectious stage: L2 larva in egg
identify
Toxocara spp.
Egg round, 75-90 µm, thick shell, surface golf
ball-like
Brown to black colour
Content: single cell occupies almost all the shell
identify
Toxascaris leonina
Egg round, 70-85 µm
Thick shell, smooth surface, „inner layer“ of shell braid-like
Light coloured
Content: single cell occupies only part of the shell
Pathogenesis and pathologies caused by Ascarid disease.
Mostly from migrating larvae.
Eosinophilic infiltration.
Liver
Petechiae
Destruction of tissues
white spots (milk spots)
- seen in recent infection
- migration of larvae
Larvae in lungs
- Oedema
- Emphysema - ascaris pneumonia
Adults in intestines
- mucoid enteritis, occlusion, perforation, peritonitis
Clinical signs of ascarid infestation.
Mostly asymptomatic or mild.
Potbelly, retarded growth, irregular apetite
vomiting and diarrhea (foul-smelling in horses).
Heavy infections – migrating larvae
- Stunted growth
- Cough (pneumonia), nasal discharge, dyspnea
- Pulmonary oedema – death
Adults in the intestines
- Enteritis, diarrhea (with phases of constipation), abdominal pain, perforation, peritonitis
Toxascaris seems less pathogenic than Toxocara, infestation is usually without any clinical signs.
Clinical signs in humans (T.canis)
Visceral larva migrans (cutaneous larva migrans)
- fever, lymphadenopathy, cough
- Abdominal pain
- Pruritic skin
- Encephalitis – death
Ocular larva migrans
- Granulomas in retina
- uveitis, chorioretinitis
- loss of vision
Diagnosis of ascarid infestation
Anamnesis and history
Clinical signs
Differential diagnosis:
Other liver (milk spots), lungs, GI parasites
Biliary colic
pinworm of veterinary importance and covered by this course is called?
Oxyuris equi is a horse pinworm
Family Oxyridae
Order Oxyurida
Host species for Oxyuris equi
Horses, donkeys
Mostly in young animals (up to 1 year) &
old horses.
Predilection site within host for Oxyuris equi.
Mucosal villi of the Caecum, colon, rectum
Describe the mature female and male pinworm / Oxyuris equi.
Mature Female: up to 15cm
* Large greyish-white opaque worm
* Body is transparent
* Long narrow pin-like tail
* Uterus opening|vulva situated anteriorly
Mature Male: up to 1.2cm
* Expanded caudal alae
* Blunt tail
* Single pin shaped spicule
Double esophageal bulb in both sexes.
L4 already has a developed mouth
Life cycle of Oxyuris equi / horse pinworm
Direct
1) Horse eats embryonated eggs with L3 – infection
2) Larvae hatches in the small intestine (A in image)
3) In the mucosa of the caecum or colon molts to L4 (3-11 days after infection) (B)
4) L4 moves to lumen of the caecum, small and large colon, molts again (7-8 weeks after infection) (C)
5) After fertilization, female migrates to the anus, extrudes her anterior end and lays eggs in clumps around perianal skin (up to 50 000 eggs per female) (C)
6) Fast development inside the egg – 3-5 days and 2 molts
7) Perianal skin starts to itch – horse scratch the skin and eggs rub off – environment is contaminated.
Prepatent period 4-5 months
Longevity of a female worm – 6months
What does the image depict?
Equine female adult pinworm (Oxyuris equi) laying a mass of eggs
Clinical signs of horse pinworm
Oxyuris equi causes:
- Perineal dermatitis, tail itching
- Colitis (L4)
- But is mostly asymptomatic
Diagnosis of Oxyuris equi.
Anamnesis
Clinical signs + observation
Laboratory diagnostics:
Examination of faeces (adult worms)
- Eggs found rarely
- Stool sampled per rectum
Examination of perianal clumps
- Scotch-tape impression
- native sample
Necropsy
Differential diagnoses for Oxyuris equi.
Other causes of dermatitis
- Mange (acariosis)
Other causes of itching
- ectoparasites, insect bites, fungal
diseases, drug side-effects, allergy,
eosinophilic dermatitis, etc.
Other causes of restlessness
- Colics
-GI parasites
identify
Egg of Oxyuris equi / horse pinworm
Egg: 85-95 x 40-45 µm, asymmetric, yellow to brown in colour, flattened along one side,
and feature a mucoid plug at one end, U-shaped larva.
identify
Oxyuris equi egg (horse pinworm)
this egg is embryonated / larvae is developing or developed
Treatment of Oxyuris equi.
Routine anthelmintic therapy
- Ivermectin
- Moxidectin
- Benzimidazoles
- Pyrantel
- Recent reports show reduced efficacy of ivermectin and moxidectin – probable potential resistance.
Accurate doses are important.
Repeat scotch-test 2 weeks after treatment.
Latin name for whipworm species of vet med importance.
Trichuris spp. which cause trichuriosis
Synonym for Trichuris spp.
Synonym: Trichocephalus spp.
because „hair“ = „tricho“ is located on the head side and „cephalus“ means head (see image)
Morphology of Trichuris spp.
whipworms
Anterior part is 2x (+) longer than posterior part.
- Long and slender - whip-like
- Place for the esophagus
Posterior part
- Thick and short
- Place for the intestines and reproductive organs
3-8 cm long
Males have spicule with sheath
Their tail is coiled spirally
identify
eggs of Trichuris spp. (whipworms)
Size: 50-70 µm
Form: lemon-shaped
Shell: thick-shell, yellow to brown with 2 visible poles
Content: granular
PS: Due to size and shape, resemble
eggs of the nematode Capillaria spp. (lower right in image). Trichuris egg poles are transparent.
Life cycle of whipworms.
Direct cycle:
In feces, infective larvae develops inside eggs
within 1-2 months (L1) – under optimal conditions.
After ingestion, the egg dissolves in the duodenum and L1 stage larvae hatches.
L1 penetrates the mucosal glands of the colon and caecum.
Molts in the mucosa 4 times.
Adult comes to lumen and lays eggs, their anterior part is attached to mucosa.
Prepatent period 7-12 weeks
Patency up to 16 months
Where in the world are whipworms found?
Prevalent worldwide, common in Estonia
Older dogs more intensively infected
Infection heavier in younger animals
Eggs are very resistant, last years in the bedding or ground.
transmission of whipworms?
alimentary transmission with egg containing L1 stage larvae
Capillaria spp. are known by what two english names?
hairworms & threadworms
Host and organ predilection for Capillaria spp.?
Parasite of birds and mammals.
In the intestines, bladder, respiratory
organs and liver.
Causes Capillarioses
Morphology of Capillaria spp.
Whitish filamentous worm
Male - 20mm and female - 30mm
Has stichosome esophagus – 1/3 to 1/2 of the
body length.
- stichosome is a part of the esophagus
- function: secretory gland
Simple mouth
Males have one simple spicule with a primitive bursa-like structure.
Life cycle of Capillaria (Eucoleus) aerophila
Aka lungworm though this term is usually used for other nematodes. Alt. bronchial capillariasis.
a). Ingestion of infective eggs from the
environment or via paratenic host (earthworm)
b). Larvae hatch in the duodenum and migrate via the bloodstream to the lungs (through the liver and heart)
c). In the lungs they settle in the bronchi, they molt 2 times and mature
d). Following maturation of the worms;
reproduction starts, eggs are laid, coughed
up, swallowed and excreted via the feces.
e). Prepatent period is about 6 weeks. In the
environment, the infective larva develop in
the egg in 5 – 6 weeks.
Life cycle of Capillaria boehmi.
- Dog ingests infective egg with L1 or the
paratenic host. - In the duodenum the larva hatches and
migrates to lungs through liver and heart. - From the lungs the larva migrates to
nasal passages – develops to adult and
lays eggs. - Eggs travel from mouth to intestines
and out with feces.
Life cycle of Capillaria hepatica.
1) Adult worms are located deep within the liver parenchyma of the host, and lay hundreds of eggs in the surrounding
parenchymal tissue.
2) Eggs remain in the liver until the animal dies.
3) Or is eaten by a predator or scavenger.
4) Then unembryonated (not infectious) eggs pass through the digestive tract out in feces.
5) Eggs embryonate in the environment.
6) Embryonation is slow and may take between 6 weeks and 5 months. .
7) The cycle continues when embryonated eggs are eaten by a suitable mammalian.
8) Infective eggs hatch in the intestine, releasing L1 which penetrates the intestinal wall and migrate via the portal vein to the liver parenchyma within 3-4 days.
Larvae take about 3-4 weeks to mature into adults and mate. Dogs, cats, humans are usually infected after ingesting embryonated eggs in fecally-contaminated food, water, or soil.
Clinical signs of Capillarioses.
Light infection is asymptomatic
Moderate to severe infection:
C. aerophile: nasal discharge, sneezing, cough, dyspnoea, weakness, poor growth, death
C. putorii: digestive disorders, vomiting
C. plica: infection in the bladder, urinary disorders: painful and frequent, hematuria
C. hepatica.: liver function disorders, icterus, apathy, anorexia, vomiting
Describe eggs of capillaria spp.
Eggs
Size: 60-80 µm and 30-40 µm
Color: green to yellow brown
Content: granular, unsegmented
Shape: ovale, 2 polar plugs are transparent
Shell: thick-shell
whose eggs deez?
Capillaria, Angylostoma, Trichuris
Capillaria eggs look similar to those of Trichuris species (large eggs and poles are non-transparent);
C. eggs = both polar plugs are not protruding, so that the poles appear more or less rounded.
PS: C. plica egg are found in the urine!
