PGE - Nematodes

Question 1

Name the nematodes involved in PGE (7)

Answer 1

Ostertagia ostertagi, Teladorsagia circumcincta
Haemonchus contortus
Trichostrongylus axei
Cooperia spp.
Trichuris
Nematodirus battus (lambs only)

Question 2

Describe the lifecycle of Ostertagia

Answer 2

1. Adults lay eggs which are excreted in the faeces
2. L1 hatch in faeces
3. L1 -L2 (free living stage)
4. L3 ingested and penetrate abomasal mucosa
5. L3 develop to L4 or arrest
6. Adults burst out of gland and feed on abomasal wall

Question 3

How does the lifecycle of Haemonchus differ from that of Ostertagia?

Answer 3

L3 attach to the abomasal mucosa and feed. They mature to L4 and then to adults which move freely along the mucosa, feeding intermittently.

Question 4

How does the lifecycle of Trichostrongylus differ from that of Ostertagia?

Answer 4

Same except larvae penetrate mucosa of small intestine as well as abomasum

Question 5

In which tissue does the larval stage of Cooperia arrest?

Answer 5

Proximal 1/3 of small intestine

Question 6

Describe the pathology of Ostertagia

Answer 6

Simulataneous maturation and breaking out of adults.
Hyperplasia of gastric glands
Loss of cellular differentiation
Central orifice marks exit of worm
Decreased HCl = increased pH
Increased gastrin and pepsinogen (not converted to pepsin) = hypergastrinaemia

Question 7

Describe the pathogenesis of Haemonchus

Answer 7

Feeding of adults on mucosa causes haemorrhage - penetrate capillaries causing petechial haemorrhaging

Question 8

What are the clinical signs of type 1 Ostertagia infection and in what age of cattle is it seen?

Answer 8

FGS calves in July - October
Profuse, watery, green d+
High morbidity, high mortality
+/- submandibular oedema

Question 9

What are the clinical signs of type 2 Ostertagia infection and in what age of cattle is it seen?

Answer 9

Due to ALD of L4 acquired at pasture
Intermittent d+
Weight loss and anorexia
Increased thirst
Low morbidity, high mortality

Question 10

What are the clinical signs of Haemonchus?

Answer 10

Anaemia
D+
Weight loss
Submandibular oedema
Ill thrift

Question 11

What are the general clinical signs of PGE?

Answer 11

Weight loss/poor weight gain
D+
Anorexia
Submandibular oedema
Ill thrift
Dehydration

Question 12

How is Ostertagia dagnosed?

Answer 12

CS
Seasonal incidence and grazing hx
Response to worming tx
FEC - type 1
Increased blood gastrin and pepsingoen
PM

Question 13

How is PGE diagnosed?

Answer 13

CS
Occult blood in faeces (Haemonchus)
FEC (Ostertagia, Trichostrongylus, Cooperia, Nematodirus)

Question 14

Describe the lifecycle of Trichuris (whipworm)

Answer 14

1. L1 is ingested as an egg
2. Plugs at either end of egg are digested and L1 is released
3. L1 form mucosal nodules in the large intestine and develop
4. Adults emerge into the lumen and attach to mucosa of caecum and LI where they feed on tissue secretions from damaged cells - cause ulceration and necrosis

Question 15

Describe the lifecycle of nematodirus

Answer 15

1. Eggs deposited on pasture
2. L1 slowl develops inside the egg to L3, can survive up to 2 years on pasture
3. Hatching occurs after a period of prolonged chill at a temp of 10-17 degrees
4. L3 are ingested

Question 16

Describe the pathology of Nematodirus

Answer 16

Lambs 6-10 wks
Late April - June
Eggs rarely passed by ewes

Question 17

What are the clinical signs of Nematodirus?

Answer 17

Sudden onset of profuse d+ (black-green/pale yellow/colourless)
Rapid dehydration
Death

Question 18

How is Nematodirus diagnosed?

Answer 18

FEC - usually -ve as CS are seen 11-12d post infection whereas the PPP is 15s
PM - enteritis

Question 19

How is PGE treated?

Answer 19

ML - Moxidectin, Doramectin, Eprinomectin, Ivermectin
BZD - Albendazole, Fenbendazole, Oxfendazole
LEV - Levamisole

Question 20

How can PGE be controlled?

Answer 20

Alternatively graze cattle and sheep annually
Feed tannin rich forages e.g. clover, lucerne, trefoil
Anthelmintic tx