Trematodes

Question 1

Digenean

Answer 1

Indirect lifecycle

Adult flukes only found in final host

Question 2

Morphological stages of life cycle

Answer 2

Egg dev miracidium that infects 1st intermed host
Inside mollusc dev into sporocyst guves rise to redia giving rise to cercarua eventually dev into metacercaria (infective to final host)

Question 3

Fasciola hepatica

Answer 3

Snails and mammalian species
Seasonal determined by temp and moisture effect on snail pop and free living stages
Snails around ponds and acidic marshy areas (pop multiply rapidly in spring between 15 and 26 degees)
Survive dry period by burrowing so cerceriae released en masse when moisture returns
April-nov in Uk good for fluke and snails
Smails infected late spring and warly summer by hatched miracidium deposited prev autumn and winter
Encyst as metacercaria in late summer and autumn so seen in sheep sept-dec

Question 4

Moist and temp effects fasciola hepatica

Answer 4

Miracidia only dev within egg over 10 degree and hatch 6wk after
Eggs are shed when temp above 15
Over 22 can mean hatching occurs much quicker
Usually hatch en masse

Question 5

Black disease

Answer 5

Fatal peracute infection of all ages of sheep
Clostridium novyi toxins
Triggered by migrating larvae

Question 6

Chronic fasciolosis

Answer 6

Adults in bile ducts
Seen fev-march also maybe in summer
Mature flukes in bile ducts
Areas of fibrosis around bile ducts
Irregular shape due to compensatory hypertrophy

Question 7

Fasciolosis in sheep and cattle causes

Answer 7

Poor repro performance

Question 8

Dicrocoelium dendriticum

Answer 8

Adult in bile ducts lay eggs cont miricidia
Hatch after ingestion by land snail
Sporocysts dev in snail
Cercariae in slime eaten by ants
Metacercari in ant body cavity and brain cause climb to top of plant and paralysis then ingested by ruminants
Hatch once in s intest of sheep and migrate along main bile ti liver
Adult in bile ducts survive for many yrs

Question 9

Paramphistomes

Calicophoron daubneyi

Answer 9

Similar to free living and int host stage of f hepatica
Cercariae swim and encyst as metacecarie on vegetation
Eaten by cattke or sheep
Excyst on duodenum
Immature flukes attach and plug feed
Young flukes migrate to fore stomach where they mature adult flukes attach tomforestomach and feed on blood

Question 10

Schistosomes

S mansoni

Answer 10

Human intestinal
Atypical as they are dioesious
Def hist sec repro
Intermed snail hist asex repro

Question 11

Shistoma lifecycke

Answer 11

Eggs shed into water in faeces
Miracidia hatch in resp to temp light dilution of faeces etc
Search for and penetrate freshwater snail
Dev and multiply through sporocyst gen to cercaria in snail
Emerge from snail during daylight and seek final hist attach to skin and penetrate
Once inside head of cecariae change to shistosimule (endoparasitic larvae)
Enter circ starting at dermal lymphatics and venules feeding on blood
Migrate to lungs and hepatoportal curc via l side of heart
Form monogamous mating pairs mature and migrate to mesenteric vein
Eggs laid onto endo lining of venous capill walls
Eggs work their way to intestinal lunen aided bu hook and enzymes and are shed

Question 12

Shistosoma pathology

Answer 12

Due to egg passage

Swimmers itch caused by initial attachment and penetration

Question 13

Schistosoma bovis

Answer 13

Adult f in ventral groove of m in portal mesenteric and urogenital veins
F penetrate submuc blood vessel of intestine and bladder
Eggs travel to intestinal lumen and are passed in faeces and urine
Eggs hatch in water and miracidia penetrate snails
Following asex repro motile cerceria infect final hists through skin or orally
Young flukes travel in blood to heart lungs and systemic circ befoe localising to the liver and entering portal circ

Question 14

Schistosoma japonicum

Answer 14

Dermatitis

Pneumonia