Parasitic Infections of the MSK I Flashcards
What is trichinella
Nematode that causes the disease trichinosis
How do people get infected with Trichinella?
Via ingestion of meat containing larval cysts
How many species of trichinella are there?
Nine species and three unnamed genotypes
How is trichinella transmissed?
- Predation
- Cannabalism
- Feeding on carrion
What animals is trichinella mainly in?
mainly in wild animals
* endemic in domestic pigs in latin america and china
How many trichinella hosts are there?
Over 100 mammal species, 7 avian species and 3 reptile species
Where can trichinella larvae survive?
Decaying carcasses/ Frozen Carrion
How many trichinella cases are there per annum?
10,000 per annum
What is the most important infection source of trichinella in europe?
Domestic pork/ wild boar
What is the clinical consequence of trichinella in animals?
It is non-pathogenic for natural hosts unless there are large numbers of larvae in the muscles
What is the EU approved method of diagnosing trichinella in animals?
- Direct observation of larvae in carcasses
What are the predilection trichinella sites in pigs?
- Diaphragm
- Tongue
- Masseter muscle s
digest with pepsin and HCL
sediment & examine under a microscope
What are two alternative methods to test for trichinella?
- PCR
- look for antibodies in serum or meat ‘juice’
Name 5 ways you can control/ prevent trichinella
- On-farm biosecurity
- Cooking to reach an internal temperature of above 71 degrees
- abattoir testing of breeding sows, boars and pigs
this is not neccesary for pigs raised in controlled housing - Feral wild boar supplied to consumers and local retailers needs to be tested
What is the adult morphology of taenia?
- 2-20m
- 1000-2000 segments
- segments are ‘longer than wide’
What are the general features of taenia?
- Parasite eggs survive in warm moist soil
- Cysticerci survive 2-3 years
What is taenia transmission associated with?
- Poor sanitation
- Consumption of inadequately cooked beef/ pork
- insufficient meat inspection at animal slaughter
What is the intermediate host of taenia saginata?
Cattle
What is the definitive host of taenia saginata?
Humans
What is cysticerus?
Infection caused by the parasite taenia solium
What is the epidemiology of T.saginata?
- Extensive cattle rearing, poor sanitation, informal slaughter practices
- Calves are always infected early in life- cattle then develop immunity and are resistant to further infection
- the prevalence of cystericosis in cattle can be 30-60%
where is the presence of cystericosis low?
Europe due to good sanitation and meat inspection practices
What are the three risk factors for bovine cysticercosis in europe?
- Access to pasture and contaminated water
- Dairy production
- Uncontrolled human defecation close to farms
What does the taeniasis disease look like?
- usually asymptomatic
- fullness or abdominal pain
- it is often only discovered when proglotidds are seen in faeces or crawling onto bed clothes
What does taenia solium disease look like in intermediate hosts (humans)
mainly juveniles
- Cysts in muscles, sub-cutaneous tissue, eyes and brain
- Asymptomatic to severe disease
- Important cause of epilepsy
How could you diagnose taeniasis
- may be a few eggs in faeces but the proglottids are often intact
- PCR
- antigen/ antibody tests
How do you control taeniasis and crystericosis?
- Improved sanitation
- Health education
- Mass chemotherapy of pigs
- Meat inspection and processing of meat products
- Preventative chemotherapy
What are the definitive hosts of taenia ovis I?
Dogs and wild canids
What are the intermediate hosts of taenia ovis I?
Sheep
How can you diagnose taenia ovis?
- Diagnosis through identification of cysts at meat inspection
What is the lifecycle of trichinella
- Larvae is encysted in striated muscle
- Ingestion of undercooked meat in a human
- Larvae are released into the SI of the human
- become adults in the SI
- Larvae are deposited in the mucosa
- then become encysted in the straited muscle
What are the three main trichinella species?
- T.pseudospiralis
- T.papuae
- T.zimbabwensis
How many hosts are there of trichinella?
100 mammal species, 7 avian species and 3 reptile species
What is the EU approved method of detecting trichinella in pigs?
- The predilation sites are the tongue, masseter muscles and diaphragm
- take over 1/2g
- Digest with pepsin and HCL
- Sediment and examine under a microscope
What are 3 ways you can control trichinella?
- On-farm biosecurity
- Cooking to reach an internal temperature of above 71 degrees
- Abbatoir testing of breeding sows
What is the lifecycle of Taenia Saginata?
- Cow ingests embryonated eggs
- Oncospheres migrate to tissues
- develop to cysterci
- cysterci are ingested by humans
- they are released from a muscle in the stomach
- worms mature and live in the intestine
- Adults then grow to 10cm in length
- Proglottids pass in the faeces
Cattle are intermediate hosts
What are Taenia outbreaks associated with?
Use of human sewage on fields
What is the lifecycle of taenia solium?
- Eggs or gravitad proglottids are found in faeces
- these are then ingested by pigs or humans
- oncospheres hatch and penetrate the intestinal wall
- they develop in the cysterci of muscles
- humans acquire the infection by consuming raw or undercooked meat from an infected animal host
How would you diagnose cystericosis?
- Imaging
- ELISA
- Antibody detection
- Tongue palpation
- Meat Inspection at Slaughter
- Post-Mortem
