GI nematodes: Ostertagia Osteragi

Question 1

Which species do O. ostertagi affect?

Answer 1

Ruminants

Question 2

Describe the life cycle of O. ostertagi

Answer 2

1. L3 stage is ingested by ruminant
2. L3 hatch and penetrate the abomasal gland where they can arrest in L4 stage over winter
3. Develop into immature adult, then mature in abomasum
4. Adults lay eggs which are excreted in faeces
5. Eggs hatch in faeces and develop from L1 to L2 which are the non-parasitic free living stages in the environment
6. L2 develops to L3

Question 3

Describe the pathology of O. ostertagi

Answer 3

1. Hyperplasia and oedema of abomasal mucosa (mucosa has morrocan leather appearance)
2. Pathology due to growth and eruption of larvae
3. Large numbers of adult worms will be present

Question 4

What are the 2 clinical forms of O. ostertagi?

Answer 4

1. Type 1
   - seen in grazing calves
   - due to larvae acquired from pasture 2-3 wks previously in late summer
   - occurs July - October
2. Type 2
   - seen in housed yearlings
   - due to maturation of L4 acquired from pasture during previous autumn
   - occurs March - May

Question 5

State 5 clinical signs of type 1

Answer 5

1. Profuse, watery diarrhoea
2. Weight loss
3. Submandibular oedema
4. High morbidity
5. Low mortality (if animals treated with anthelmintics)

Question 6

State 7 clinical signs of type 2

Answer 6

1. Intermittent diarrhoea
2. Submandibular oedema
3. Weight loss
4. Moderate anaemia
5. Anorexia and increased thirst
6. Low morbidity
7. High mortality

Question 7

How is O. ostertagi diagnosed?

Answer 7

1. Clinical picture and grazing pattern analysed
2. Diagnosis done on herd basis
3. Diagnostic tests; WEC, serum pepsinogen, serum antibody, PM

Question 8

How can type 1 be treated?

Answer 8

Most currently available anthelmintics and move to clean pasture.

Question 9

How can type 2 be treated?

Answer 9

Modern benzimidazoles, macrocyclic lactones, pro-benzimidazoles.

Question 10

How can O. ostertagi be controlled?

Answer 10

1. Grazing management
2. Prophylactic medication
3. WEC and monitor growth rates