Parasites of the nervous system

Question 1

What type of parasite is taenia multiceps?

Answer 1

Cestode parasite (tape worm)

Question 2

What is the definitive host of taenia multiceps?

Answer 2

Canids

Question 3

What disease does taenia multiceps cause?

Answer 3

Causes disease coenurosis, aka “gid” or “staggers”, in sheep

Question 4

Where is taenia multiceps found?

Answer 4

Found worldwide but absent from the USA and New Zealand

Question 5

What is the adult morphology of taenia multiceps?

Answer 5

• Adult worms are 40-100cm in length
• They have small heads, 0.8mm in diameter
• also have a double ring of rostellar hooks

Question 6

What is the pathology of taenia multiceps?

Answer 6

• Cysts (5cm long) are found in the cerebral hemisphere
• they are found less commonly in the cerebellum or spinal cord
• As the cyst develops -> damage to brain tissue -> neurological disturbances
• Cyst causes pressure atrophy -> perforation of the skull
• Cysts in the spinal cord -> paresis of the hindlimb

Question 7

What are the clinical signs of acute coenurosis?

Answer 7

• sheep graze on heavily contaminate pasture
• migration of larvae through the brain causing neurological dysfunction
• clinical signs appear 10 days after infection

Question 8

When does death occur from acute coenurosis?

Answer 8

Death occurs 3-5 days from the onset of neurological signs

Question 9

What is the pathology of acute coenurosis?

Answer 9

acute meningoencephalitis and pale yellow tracts (necrotic tissue) on the brain surface

Question 10

When does chronic coenurosis occur?

Answer 10

3-6 months post infection in sheep 6-18 months of age

Question 11

What does a chronic coenurosis lesion look like?

Answer 11

progressive focal lesion of the brain
presentation depends on the cyst location and size

Question 12

What are the clinical signs of chronic coenurosis?

Answer 12

Compulsive Circling behaviour, head pressing and depression
Visual defects, stumbling/ uncoordinated movements, postural defects, animal may also develop anorexia and weight loss
* sheep will circle towards the side of superficial cysts and away from deeply-sited cysts

Question 13

What is the definitive host of T.multiceps?

Answer 13

Dogs, can diagnose by finding tapeworm segments in perianal area or proglottids/ eggs in faeces

Question 14

How could you treat the intermediate host of T.multiceps?

Answer 14

• Surgery to remove the cyst
• Slaughter sheep fit for market, and euthanise any others

Question 15

How could you control T.multiceps?

Answer 15

• Regular anthelmintic treatment of working dogs
• Correct disposal of sheep carcasses
• Vaccine based on recombinant proteins of T.multiceps

Question 16

How can humans become infected with Coenurosis?

Answer 16

accidental ingestion of parasite eggs, contaminating food or water

Question 17

When do coenurosis cysts develop?

in humans

Answer 17

they develop over 90 days

Question 18

What are the neurological symptoms of coenurosis in humans?

Answer 18

• headaches, seizures, hemiparesis, and hydrocephalus

Question 19

What is the adult morphology of thelazia callipaeda?

Answer 19

• Thin/ yellowish worms
• 1-2cm long
• round worms (nematodes)

green picture on histo

Question 20

What is the pathogenesis of thalezia?

Answer 20

Lesions and damage are due to serrated cuticle of the worm and movement of active young adults
* causes lachrymation and conjunctivitis
* photophobia in cattle

Question 21

What do heavy thalezia infections look like?

Answer 21

cornea is cloudy and ulcerated, swollen eye

flies will cluster around the eyes

Question 22

What may a thalezia infecton predispose to?

Answer 22

secondary bacterial infection

Question 23

What are the two ways you may diagnose thalezia?

Answer 23

• Conjunctivitis in the season of fly activity
• Observation of worms on the conjunctival surface/ in the conjunctival sac

Question 24

How may you treat thalezia?

Answer 24

• Anthelmintics
• Mechanical removal with forceps (horses and dogs)

Question 25

How long can the thalezia parasite survive in the eye?

Answer 25

The parasite can survive in the eye or several years, but only the young adult is pathogenic -> symptomless reservoir

Question 26

What is sarcocystitis neurona?

Answer 26

* Protozoan parasite * causes equine protozoal myeloencephalitis (EPM) | found in the americas

Question 27

Where is Sarcocystitis neurona found geographically?

Answer 27

the Americas

Question 28

How can horses become infected via sarcocystitis neurona?

Answer 28

ingestion of food or water contaminated with opossum faeces

Question 29

What are the risk factors of sarcocystitis neurona?

Answer 29

* Seasonality (more common in autumn) * Presence of opossums in wooded areas * Stress * racehorses/ show horses

Question 30

What are the clinical signs of sarcocystitis neurona? | pathologically

Answer 30

acute or chronic multifocal neurological disease

Question 31

What are the clinical signs of sarcocystitis neurona?

Answer 31

* Dysphagia * abnormal upper airway function * unusual lameness * seizures * head-tilt * facial nerve paralysis | in vital signs- animal appears alert and vital signs are normal

Question 32

How could you treat sarcocystitis neurona?

Answer 32

Medical and supportive treatment as neccesary

Question 33

How can you control sarcocystitis neurona?

Answer 33

* Decrease stress * decrease exposure to opossum faeces * intermittent drug treatment

Question 34

What are the clinical signs of canine neosporosis?

Answer 34

fatal progressive ascending hindleg paralysis * lesions in the brain, spinal cord, nerve roots, skeletal muscle * more severe in transplacentally infected puppies

Question 35

Where are canine neosporosis lesions most commonly found?

Answer 35

* Brain, Spinal Cord, nerve roots, skeletal muscle

Question 36

What is the lifecycle of taenia multiceps?

Answer 36

* Eggs are in faeces and then pass onto the environment * Embryonated eggs then pass onto/ are ingested by the intermediate host * Oncospheres hatch and penetrate the intestinal wall, circulate to tissue * Oncospheres develop into coenuri in the tissue of the intermediate host * Canids are infected by ingesting the intermediate host * Scolex attaches to the intestine, they become adults in the small intestine * embryonated eggs are ingested by a human host

Question 37

How would you diagnose Taenia in the intermediate host?

Answer 37

* Clinical signs, differentials, listeriosis, louping-ill, sarcocystosis, polioencephalomalacia * CSF collection and analysis * local softening of the frontal bones * Ultrasound

Question 38

How would you diagnose Taenia in the definitive host?

Answer 38

* Diagnosis in dogs-> presence of tapeworm segments in the perianal area or proglottids/ eggs in faeces

Question 39

How do humans become infected with coenurosis?

Answer 39

Accidental ingestion of parasite eggs * Cysts develop over 90 days

Question 40

Name 4 eye worms

Answer 40

* Thelazia rhodesi * Thelazia lacrymalis * Thelazia callipaeda * Oxyspura mansoni

Question 41

What is the lifecycle of Thelazia? | Muscid fly

Answer 41

* Adults shed larvae by oviviviparity in the conjunctiva of the definitive host * first-stage larvae are ingested by the insect intermediate host as it feeds on tears of teh definitive host * L1-> L3 follicles in summer months * Larvae develop into L3 larvae in the intermediate host * L3 migrate to fly mouthparts * Cattle horses and dogs serve as primary definitive hosts, they become adults in the conjunctival sac * Humans become incidental hosts

Question 42

What is the epidemiology of thalasezia?

Answer 42

Infections occur seasonally, linked to periods of maximum fly activity Larvae can survive in fly pupae overwinter [arasite survives in the eye for severa; years but only the young adult is pathogenic -> symptomless reservoir

Question 43

What is the lifecycle of sarcocystitis?

Answer 43

* Horse ingests a sporocyst * Horse acts as an abberant host * Intermediate host -> cat, skunk, raccoon, sea-otter

Question 44

What is the transmission of sarcocystitis?

Answer 44

* Horses are accidental intermediate hosts * infected through ingestion of food and water contaminated with opossum faeces * no horizontal transmission between horses * vertical transmission is very uncommon * not all infected horses develop disease * mechanism of pathogenesis is poorly understood

Question 45

What is the antemortem diagnosis for sarcocystitis?

Answer 45

* Clinical signs * Neurological signs * Confirm using immunodiagnostic testing * rule out other potential causes