Parasites of the nervous system Flashcards
What type of parasite is taenia multiceps?
Cestode parasite (tape worm)
What is the definitive host of taenia multiceps?
Canids
What disease does taenia multiceps cause?
Causes disease coenurosis, aka “gid” or “staggers”, in sheep
Where is taenia multiceps found?
Found worldwide but absent from the USA and New Zealand
What is the adult morphology of taenia multiceps?
- Adult worms are 40-100cm in length
- They have small heads, 0.8mm in diameter
- also have a double ring of rostellar hooks
What is the pathology of taenia multiceps?
- 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
What are the clinical signs of acute coenurosis?
- sheep graze on heavily contaminate pasture
- migration of larvae through the brain causing neurological dysfunction
- clinical signs appear 10 days after infection
When does death occur from acute coenurosis?
Death occurs 3-5 days from the onset of neurological signs
What is the pathology of acute coenurosis?
acute meningoencephalitis and pale yellow tracts (necrotic tissue) on the brain surface
When does chronic coenurosis occur?
3-6 months post infection in sheep 6-18 months of age
What does a chronic coenurosis lesion look like?
progressive focal lesion of the brain
presentation depends on the cyst location and size
What are the clinical signs of chronic coenurosis?
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
What is the definitive host of T.multiceps?
Dogs, can diagnose by finding tapeworm segments in perianal area or proglottids/ eggs in faeces
How could you treat the intermediate host of T.multiceps?
- Surgery to remove the cyst
- Slaughter sheep fit for market, and euthanise any others
How could you control T.multiceps?
- Regular anthelmintic treatment of working dogs
- Correct disposal of sheep carcasses
- Vaccine based on recombinant proteins of T.multiceps
How can humans become infected with Coenurosis?
accidental ingestion of parasite eggs, contaminating food or water
When do coenurosis cysts develop?
in humans
they develop over 90 days
What are the neurological symptoms of coenurosis in humans?
- headaches, seizures, hemiparesis, and hydrocephalus
What is the adult morphology of thelazia callipaeda?
- Thin/ yellowish worms
- 1-2cm long
- round worms (nematodes)
green picture on histo
What is the pathogenesis of thalezia?
Lesions and damage are due to serrated cuticle of the worm and movement of active young adults
* causes lachrymation and conjunctivitis
* photophobia in cattle
What do heavy thalezia infections look like?
cornea is cloudy and ulcerated, swollen eye
flies will cluster around the eyes
What may a thalezia infecton predispose to?
secondary bacterial infection
What are the two ways you may diagnose thalezia?
- Conjunctivitis in the season of fly activity
- Observation of worms on the conjunctival surface/ in the conjunctival sac
How may you treat thalezia?
- Anthelmintics
- Mechanical removal with forceps (horses and dogs)
How long can the thalezia parasite survive in the eye?
The parasite can survive in the eye or several years, but only the young adult is pathogenic -> symptomless reservoir
What is sarcocystitis neurona?
- Protozoan parasite
- causes equine protozoal myeloencephalitis (EPM)
found in the americas
Where is Sarcocystitis neurona found geographically?
the Americas
How can horses become infected via sarcocystitis neurona?
ingestion of food or water contaminated with opossum faeces
What are the risk factors of sarcocystitis neurona?
- Seasonality (more common in autumn)
- Presence of opossums in wooded areas
- Stress
- racehorses/ show horses
What are the clinical signs of sarcocystitis neurona?
pathologically
acute or chronic multifocal neurological disease
What are the clinical signs of sarcocystitis neurona?
- Dysphagia
- abnormal upper airway function
- unusual lameness
- seizures
- head-tilt
- facial nerve paralysis
in vital signs- animal appears alert and vital signs are normal
How could you treat sarcocystitis neurona?
Medical and supportive treatment as neccesary
How can you control sarcocystitis neurona?
- Decrease stress
- decrease exposure to opossum faeces
- intermittent drug treatment
What are the clinical signs of canine neosporosis?
fatal progressive ascending hindleg paralysis
* lesions in the brain, spinal cord, nerve roots, skeletal muscle
* more severe in transplacentally infected puppies
Where are canine neosporosis lesions most commonly found?
- Brain, Spinal Cord, nerve roots, skeletal muscle
What is the lifecycle of taenia multiceps?
- 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
How would you diagnose Taenia in the intermediate host?
- Clinical signs, differentials, listeriosis, louping-ill, sarcocystosis, polioencephalomalacia
- CSF collection and analysis
- local softening of the frontal bones
- Ultrasound
How would you diagnose Taenia in the definitive host?
- Diagnosis in dogs-> presence of tapeworm segments in the perianal area or proglottids/ eggs in faeces
How do humans become infected with coenurosis?
Accidental ingestion of parasite eggs
* Cysts develop over 90 days
Name 4 eye worms
- Thelazia rhodesi
- Thelazia lacrymalis
- Thelazia callipaeda
- Oxyspura mansoni
What is the lifecycle of Thelazia?
Muscid fly
- 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
What is the epidemiology of thalasezia?
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
What is the lifecycle of sarcocystitis?
- Horse ingests a sporocyst
- Horse acts as an abberant host
- Intermediate host -> cat, skunk, raccoon, sea-otter
What is the transmission of sarcocystitis?
- 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
What is the antemortem diagnosis for sarcocystitis?
- Clinical signs
- Neurological signs
- Confirm using immunodiagnostic testing
- rule out other potential causes
