trichostrongyloidae family SDL

Question 1

describe the morphology of trichostrongylus spp

Answer 1

• small hair-like worms
• up to 0.7 mm long (difficult to see with naked eye)
• bursate nematode (tail of male containes bursa)
• small buccal capsule

Question 2

discuss trichostrongylus lifecycle

Answer 2

• inhabit alimentary tract of animals and birds
• direct, non-migratory life cycle
• infection via ingestion of free L3

Question 3

list common species of trichostronyloides

Answer 3

• Trichostrongylus colubriformis (sheep, goats and cattle) live in small intestine
• Trichostrongylus axei (sheep, goats and cattle) live in abomasum
• Trichostrongylus tenuis (birds)
• Trichostrongylus capricola
• Trichostrongylus vitrinus

Question 4

outline the general lifecycle of trichoctrongyles

Answer 4

Question 5

explain the intestinal pathology of trichostrongyloidae spp

Answer 5

• sloughing of intestinal vili
• leads to acute diarrhea in young
• chronic diarrhea in older animals
• enlarged mesenteric lymph nodes
• subclinical infection can reduce weight gains by 35%, wool growth by 10% and milk production by 20%

Question 6

discuss mechanisms of immunity to trichostrongylus spp

Answer 6

immune exclusion: exclusion of/barrier against L3
- mucus from immune sheep prevented establishment of trichostrongyloides in naive sheep intestine. IgA and mucus IgG recognises 3 different classes of L3 in cuticular Ags

Self cure: exclusion of adults in intestine
- this involves mast cells, IgE and eosinophils (TH2 induced immune response)
- romney sheep have increased expression of IL-5 and IL-3 in mesenteric lymphoid cells (IL-5 activates eosinophils, IL-3 stimulates eotaxin and eosinophil migration and class switching to IgE)
- T cell induced and can be prevented in T cell ablation models or can be induced when naive animals have T cells from immune animals adoptively transferred into them

Question 7

what causes parasitic gastroenteritis

Answer 7

can be caused by many nematode species from early summer to autumn. Often anthelmintic treatment may be given and if it works PGE will simply be diagnosed

Question 8

how do you treat trichostronguloid infection and reduce incidence parasitic gastroenteritis

Answer 8

• strategic use of anthelmintics to minimize pasture contamination
• reduce frequent tx and treat on the basis of the number of worm eggs. this will save money and reduce the risl of developing resistance on the farm
• provide adequate nutrition
• reduce overcrowding and the number of cattle on pastures
• move animals to clean pastures to minimize reinfection

Question 9

what anthelmintics can be used to treat trichostrongyloid infection

Answer 9

• albendazole
• fenbendazole
• levamisole
• ivermectin
• moxidectin
• doramectin

Question 10

how do you control trichostrongyloides

Answer 10

• must be careful not to induce development of resistance (possible with repeated treatments)
• allow a reasonable level of acquired immune resistance via regular contact with nematodes
• refuges (part of the parasitic population not exposed to selection pressure induced by administration of dewormers)
• some anthelmintic drugs can have adverse effects on non-target organisms especially those that live in/on dung

Question 11

list classes of anthelmintics and their visual descriptors

Answer 11

Question 12

what is reversion and is it likely no occur

Answer 12

reversion = return to susceptibility
not likely to occur in nematode populations. this means that resistance to anthelmintic will remain in a population forever(?)