Helminths Flashcards

Question

Free living nematode enviro conditions

Answer 1

Most teichostrong eggs survive best at 18-26 degrees at higher temp dev is faster but energy rate more quickly depleted so incr mortality rate Eghs dont hatch or larvae dev at temp below 10 Larval dev only when humidity over 80% and optimal at 100 survival low at below 80 in herbage Humidity in grass and faeces allows dev when dry Dessication kills L3

Answer 2

``` Thick walled enviro res eggs (ascarid) Retention of L2 cuticle sheath on L3 assist harsh enviro survival (trichostrongyle) Arrested dev/hypobiosis Critical egg hatching req Periparturient rise in egg prod ```

Answer 3

Temporary pause in dev in host as evolutionary strategy to survive adverse enviro conditions Physiological- toxocara canis - larvae enter hypobiosis in tissues and are react 3 wk pre parturition and migrate to and infect foetus Seasonal - ostergaia ostertagi - larvae ingested in autumn and overwinter in abomasal gastric glands larval dev resume in spring

Answer 4

Larvae overwinter in eggs Hatch onto pasture in spring after receiving enviro trigger usually temp Allow mass emergence in spring when many suscept hosts around

Answer 5

Incr faecal egg count of ewes and goats around parturition Competition between host imm stst and pro req of pregnancy and lactation so arrested larvae mature incr new infect establishment incre female egg output

Answer 6

``` Cestodes and trematodes Dorso ventr flattened No bidy cavity Organs embedded in solid matrix Monoecious Both sex and asex repro Some trematodes are triploid ```

Answer 7

Unsegmented leaf like One or two suckers for host attachment Blind gut with single opening Indirect lifecyvle with one or two int hosts one of which is always a mollisc

Answer 8

Segmented Very ling sometimed Usually have a distinct scolex/head with hooks and or duckers for hist attachment Identical proglotids (segments) continually prod form neck of scolex Proglottids flat white and rectamgles in tape form known as strobila Mature into self cont hermaphroditic egg prod units No gut-nutrients diffuse through cuticle Indirect lifecycle with vert and invert int host

Answer 9

Upset by domestication and intensive farming dev creating enviros that: Suited to dev and survival of free living stages with enganced exposure to infective forms Inadvertantly alter host imm or inn resp Enable exposure to prev unrecog species and strains Can upset sustainable equilibrium between parasote and host Can guve competetive advantage to some allowing them to presominate and be more patjogenic

Answer 10

Evasion : low stocking densities on variety of herbage and co grazing or browsing with other animals that are hosts to same parasites Grazing rotation Seldom conducive to economic prod Strategic use of anthelmintics aim to suppress infective larval pop, due to highly pleomorphic genome they will become res Most farms and pet owners etc have become athlemintic dep to maintain productivity and good welfarr Used to strike balance between level of challenge that impairs an animal and that needed to enable protective imm dev

Answer 11

Effect of climatic variation on livestock and helminths Freq stockpvement and quarantine impracticality Sub efficacy of some drug usage Innapripriate timing of administration Effect of concurrent dis or managment on anthelmintic action

Answer 12

Hook worms and cutaneous larva migrans Ascarid and visceral nematodes Human fasciolosis Exhinococcus tapeworm

Helminths Flashcards

(36 cards)