Bursate Nematodes 2

Question 1

What are the 3 major groups of bursate nematodes?

Answer 1

Trichostrongtloidea (Trichostrongyles) - Direct life cycles GIT ruminants
Metastrongyloidea (Metastrongyles) - Indirect life cycles (mostly) lungworms
Strongyloidea (Strongyles) - Direct life cycles GIT horses

Question 2

Trichostrongyle Genus: Ostertagia

Answer 2

Host: PGE cattle

Question 3

What are the clinical signs of Bovine Ostertagiosis?

Answer 3

*Inappetance
*Diarrhea (greenish)
Oedema - in severe cases
Anaemia - in severe cases

Question 4

Bovine Ostertagiosis Immunity

Answer 4

-Cattle acquire immunity following first grazing season
-Older animals not affected clinically, do not complete efficient lifecycle to produce eggs
-Economic losses?
-Higher immune responses, productivity trade off
-Only slight contribution to pasture contamination

Question 5

Type 1 disease of Bovine Ostertagiosis:

Answer 5

Calves in the first grazing season
*more common form of the disease

Question 6

Type 2 Disease of Bovine Ostertagiosis:

Answer 6

Young cattle in late winter / spring following 1st grazing season, eggs deposited at time of falling temperature “cold conditioned” eggs develop along a different pathway, arrested development (hypobiosis) at EL4 stage in abomasal glands (prolonged resting phase), synchronous emergence, disease example is in housed dairy heifers, severe pathology / sporadic
*not as common as type 1 disease

Question 7

Ostertagia is more of a problem in __ calves than __ calves:

Answer 7

Dairy vs beef

Question 8

__ born calves are most at risk to Ostertagiosis:

Answer 8

Spring (in temperate climates)

Question 9

Auto-infection Disease

Answer 9

Late summer -> Autumn

Question 10

Hypobiosis / Arrested Development

Answer 10

Ostertagia ostertagi arrested larva (early L4)

Question 11

Diagnosis of Ostertagiosis:

Answer 11

Clinical history - scour in calves at grass
Type 2 - history
Fecal egg counts
Plasma pepsinogen (gastrin)
Bulk milk antibody response
Response to treatment

Question 12

Fecal Egg Counting

Answer 12

-Number of parasites is critical (parasite burden is important in grazing animals)
-Quantitative fecal examination (counting the number of eggs or larvae present)
-McMaster technique/Mini-FLOTAC
-Typical strongyle eggs
-Eggs per gram (epg)

Question 13

Parasite burdens are __.

Answer 13

Overdispersed

Question 14

Most parasites in a minority of animals __ tail - __ rule

Answer 14

Long tail; 80/20 rule

Question 15

Hosts crowded together (stocking density) favors __.

Answer 15

Transmission!

Question 16

Younger animals are more __ (with significant exceptions).

Answer 16

Susceptible!

Question 17

Pregnancy and lactation may __ host defenses (periparturient rise in sheep).

Answer 17

Reduce!

Question 18

What are the Ostertagiosis treatment options?

Answer 18

-Modern anthelmintics effective against adults and larvae
-Benzimidazoles, avermectins (macrocyclic lactones)
-Avermectin formulations with residual effects

Question 19

What’s are some preventative measures (better and cure)?

Answer 19

-control
-pasture management
-strategic anthelmintics
-combinations
-targeted (selective) treatment

Question 20

Is drug resistance a worry?

Answer 20

YES
-dose only when necessary
-rotate pastures, mixed grazing, lower stock density
-leave proportion of parasites undosed (refugia, undosed animals)
-“targeted, selective treatment”