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Trematoda Features

- Leaf like, flattened body
- Gut present
- Feed on blood & tissues or intestinal contents

Trematoda Life Cycle

SNAIL HOST -> rainfall/water source, faecal distribution
Factors for transmission: intermediate host, secondary intermediate host, final host feeding behaviours, climate

Fasciola Hepatica

Liver fluke, class trematoda
Found in sheep & cattle, adults in bile ducts & blood
Cause: liver rot, black disease, chronic anaemia, enlargement of liver & bile ducts
Cattle higher risk as sheep prefer dry food


No gut, Scolex, neck, proglottids


Scolex armed with 4 suckers, genital pores open laterally, larvae only hatch when eaten, usually 2 host life cycle


Definitive host: carnivores & people
Intermediate host: mammals (as metacestodes)
Eggs can survive 1 year in environment

Taeniidae Metacestodes

Bladder worms or hydatid
Scolex with cyst forms adult worm, most of bladder digested
Always found in organs of mammallian hosts (adults in SI)

Taenia saginata

Human beef tapeworm
Cow intermediate host

Taenia slolum

Pork tapeworm
Pig or human intermediate host
Uncooked pork -> cysticerci in brain

Echinococcus granulosus

Hydatid cysts
Humans as intermediate host cause severe disease
Adults only a few mm long, 4 segments at one time
Domestic/intermediate cycle (dog/sheep) ingest eggs in faeces
Sentinel host (cattle, pigs) infertile cysts

Family Dilepididae

Cucumber Worm
One of vet = Flea or dog tapeworm
Adults in SI of dog, cat fox
Proglottids bilateral genital pores
Intermediate host flea

Dipylidium caninum

Dog/flea tapeworm
Cucumber worm
Causes scooting
Adults in SI of dog
Intermediate host flea

Family Anoplocephalidae

Definitive host = herbivore
Intermediate host soil/pasture dwelling arthropods like mites
Adult has short wide segments

Phylum platyhelminthes

Flat worms


Sheep family anoplocephalidae
Definitive host: herbivore
Intermediate host: mites


Ruminants family anoplocephalidae
Definitive host: herbivore
Intermediate host: mites

Anoplocephala perfoliata

Horses family anoplocephalidae
Definitive host: herbivore
Intermediate host: mites
Causes fatal blockage at ileocaecal junction

Order Pseudophyllidea Features

Scolex with 2 longitudinal bothria (rather than suckers) Genital pores open dorsally or ventrally
Eggs hatch in water
Usually 3 hosts

Order Pseudophyllidea Life cycle

Definitive host = fish & lower vertebrates
2 intermediate hosts required

Spirometra erinacei life cycle

Zipper worm
Adults in cat, dog, fox (mid ventral genital pores look like zipper)
Fluke like eggs passed in faeces
Requires water for hatching coracidium
Eaten by small crustacean develops to procercoid
Infected crustacean eaten by second intermediate host (usually amphibian) develops into plerocercoid
Plerocercoids or spargana in a range of intermediate & paratenic hosts

Spirometra erinacei effects

Zipper worm
Heavy infection can cause ill thrift or enteritis (especially cats)

Spirometra erinacei order


Phylum Nematoda


Phylum Nematoda features

Elongate, cylindrical but tapering at either end
Mouth anteriorly, cloaca & tail posteriorly
Mouth > muscular pharynx or oesophagus > intestine > cloaca
Separate sexes (males smaller)

Order Strongylida (Bursate) Importance?

Most important group in domestic animals

Order Strongylida Sex differences

Sexual dimorphism, males with bursa with rays feamles with muscular ovijector at end of uterus

Order strongylida Superfamily Ancyclostomatoidea


Hookworms Lifecycle

Family Ancyclostomatoidea
Adults in SI of carnivore in ruminants L3 penetrate mucose or skin, blood vessels/lymphatics, heart, lungs, tracheal migration, swallowed into SI transmammary migration

Ancyclostoma and Uncinaria

Hookworms in dogs, cats
Blood suckers of SI
Causes anaemia, ill thrift, diarrhoea, creeping eruption on skin, enteritis

Superfamily Strongyloidea (Strongyles)

Adults in caecum and large intestine of horse ruminants pigs
Some suck blood, others feed on gut mucosa
infection by ingestion of L3

Strongylus vulgaris

Large horse strongyle
Most pathogenic
Larval penetration of gut wall and migration to cranial mesenteric artery
Carried to L1 as cysts, which erode intestinal wall and release worm into lumen
Disruption of blood flow to colon causes colic
SUSCEPTIBLE TO ANTHELMINTICS ( declining significance)


Small stronglyes/red blood worms
L3 invades mucosa of LI lives up to 2 years, L4 emerge from cyst and enter lumen destroys mucosal cells & inflammation

Strongyles & Anthelmintics

Strongylus vulgaris susceptible
Cyathostomes not susceptible

Family Trichostrongyloidea Life cycle

Hair worms
Eggs in faeces L1-Ld in faeces or migrate in environment, ingestion, sometimes penetrates mucosa, moulting, adult
Adults in upper GIT (abomasum or SI)
Infection always ingestion of L3

Trichostrongyloidea effects

Hair worms
Abomastitis, anaemia, oedema, necrosis, reduced weight gain, chronic diarrhoea, emaciation, death

Haemonchus contortus

Hair worm/Barbers pole worm
Blood suckers in abomasum
Causes anaemia, bottle jaw
Mixed infection diarrhoea
Heavy infection death during pre-patent period

Important worm for sheep in wet areas

Haemonchus contortus


(trichostrongyloidea hair worm) Cattle
Abomasum mucous metaplasia & inflammation, nodule formation, loss of plasma proteins, increased pH, decreased food intake, diarrhoea, bottle jaw

Important worm for ruminants in Summer wet/temperate areas

Ostertagia & Teiodorsagia


(trichostrongyloidea hair worm) sheep, goats
Abomasum mucous metaplasia & inflammation, nodule formation, loss of plasma proteins, increased pH, decreased food intake, diarrhoea, bottle jaw


Lung worm (trichostrongyloidea hair worm)
Lung worm of bronchial tree in ruminants
Coughing respiratory signs ill-thrift
Especially intensively farmed calves
Major disease of calves in temperate regions

Superfamily metastrongyloidea

Lung worms
Adults in lungs/pulmonary vasculature of cattle, cat rat
Require intermediate host, may use paratenic host
L1 passed in faeces (rather than egg) KINKED TAIL
Not important in domestic animals

Angiostrongylus cantonensis

Rat lungworm (metastrongyloidea)
Migrates through CNS after ingestion of intermediate host
Severe neurological disease (dogs, humans)

Aelurostrongylus abstrusus

Cat lungworm (metastrongyloidea)
Lung nematode of cats
L1 in faeces, L3 in mollusc, ingestion of paratenic host, partial tracheal migration, eggs & L1.
Respiratory signs and weight loss

Genus Strongyloides Features

Parsitic adults all female, very small, entwined with SI villi

Genus Strongyloides Lifecycle

Larvated eggs pass in faeces and hatch quickly
Develop into free living adult males or females OR become parasitic and enter host via skin
Ingestion from environment or colostrum
L3 enters blood, tracheal migration, SI parthenogenic females develop in SI

Genus Strongyloides Causes

Significant in very young horses, pigs, ruminants
Diarrhoea, ill thrift, foot rot (lambs) often asymptomatic

Strongyloides ransomi

Pig threadworms
Larvae transfer via colostrum, piglets infected within 24 hours
Severe econimic loss
Transmission uncommon in clean dry piggeries

Other strongyloides

S westeri (horses) S canis (dogs)

Order Ascaridia

Large round worms


Adults in small intestine
Eggs large numbers, sticky, thick walled
L1-L3 in egg must be eaten before hatching

Toxocara canis Lifecycle

Dog roundworms
Somatic migration of L2, larval arrest in tissues (placental/mammary transmission to pups)
TRACHEAL MIGRATION of L2 in pups L3 in pharynx Adults in SI
SOMATIC MIGRATION paratenic host direct development in SI

Toxocara canis Effects

Ill thrift vomiting diarrhoea pot belly pups

Ascaris suum

Pig roundworms
Somatic and tracheal migration via liver and lungs to SI

Pascaris equorum

Horse roundworm

Toxocara cati

Cat roundworm

Order oxyurida

Adults in LI
Direct lifecycle
Egg cememnted on perianal skin or passed in faeces
ighly host specific

Oxyuris equi

Horse Pinworm
Irritation around anus can lead to poor condition

Superfamily habronematoidea

Adults in stomach, thin shell eggs in faeces
L1 ingested by maggot of muscid fly, development to L3 escapes via fly mouthparts during feeding

Habronema spp or Draschia metastoma

Adults unimportant problem when larvae escapes into inappropriate sites

Superfamily Filarioidea

Adults in circulatory system or connective tissue, no direct route out of host
ingested by arthropods

Dirofilaria immitis

Dog heartworm
Adults in pulmonary aorta and right chaber of heart
Develop into L3 in mosquito, migrate via mouthparts during feeding, L3 and 4 develop in CT, L5 penetrates great veins and carried to distal pulmonary aorta, move proximally as they mature
Cause pneumonitis, congestive heart failure, renal disease

Trichuris species

Adults in L1 of dog, pig, ruminant, human
Long anterior end embeds in mucosa, short broad posterior end
Direct lifecycle, extremely resilient eggs pass in faeces, embryonate to L1 within egg, ingested by definitive host
Most infection light


Disease of intensive husbandry: Poultry, young animals, macropods in captivity by ingestion of oocysts

Isopora and Eimera

Coccidia Protists
Highly host specific, nearly all enteric, site in gut differs among secies

Cryptosporidium paryum

Mammals, significant zoonosis, diarrhoea in humans, disease of over crowding

Toxoplasma gondii

Coccidia protist. Tissue cyst forming
Wide range of hosts
Benign infection except in immunosupporession or pregnancy (infection in third trimester can kill fetus)


Coccidia protist tissue cyst
Direct host: canids, gamogony and oocyst formation, paralysis in pups
Intermediate host: cattle, horse, cysts in CNS, major cause of abortion in cattle


Coccidia protist tissue cyst
Muscle cysts in wide range of mammals

Order Haemosporida

Protist parasites of blood cells
Malaria and malaria like parasites in blood cells of vertebrates


Malaria Protist
Species in Australi affects birds and reptiles


Birds and reptiles, blackflies and midges are vectors. Some species highly pathogenic.


Parasites of blood cells. Tick vectors.


Tick fever (Piroplasmida protist)


Alimentary or genital track, close association with mucous membrane
Transmission by faeces of genital secretions as trophozoites or cysts


Mucosoflagellates Protist
Pear shaped, binucleate
Trophozoites, adapted for attachment to small intestine where they feed on mucous secretions, excretion of cysts, faecal and water contamination
Causes diarrhoea, malabsorption


Mucosoflagellates Cattle foetus protist
Genital infection (STD)
No cystic stage direct transfer
Infertility in female cows, abortions

Trichomonas gallinae

Mucosoflagellates Birds negrotic ulceration in upper GIT


Life in blood, lymph and/or tissue spaces transmission by blood sucking insects

Trypanosoma brucei

Nagana in animals. Sleeping sickness in humans.
Tsetse fly vector (vector in tropical africa) salivary transmission
Replicates in blood, lymph & CNS causes anaemia, fever, neuro signs
Horses and dogs highly susceptible - rapid course of disease
Ruminants chronic (midly pathogenic)

Leishmania spp

All species infect mammals (especially humans, dogs, rodents)
Amastigotes invade macrophages
Transmission by sandflies
Tropical and subtropical (exotic to Australia)
Cutaneous (curable) and visceral (fatal)


Possess cilia in at least one stage of life cycle
Most species free living, few are parasitic

Balantidium coli

Pigs and humans. Cysts passed in faeces, contaminate environment, ingestion, release in gut, then LI
Usually subclinical but association with ulcertaion of colon (diarrhoea, dysentery)

Ichtyophthirius multifilis

Whitespot in freshwater fish

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