Lungworm

Question 1

Causative agent of lungworm in cattle, camelids and deer

Answer 1

Dictyocaulus viviparus

Question 2

Epidemiology of lungworm in cattle - time of year

Answer 2

Major outbreaks July-September

When non-immune calves have been on pasture for 2-5 months and parasites have had time to reproduce

Question 3

T/F: older animals are resistant to Dictyocaulus viviparus but can act as carriers, spreading infection without showing clinical signs

Answer 3

True

Question 4

T/F: under favourable conditions, Dictyocaulus viviparus can overwinter on pasture

Answer 4

True

Question 5

Clinical signs of Dictyocaulus viviparus infection

Answer 5

Can range from bronchitis to severe pneumonia
Widespread coughing in grazing cattle: Intermittent to frequent deep, harsh coughing
Normal to elevated resp rate (tachypnoea)
+- Dyspnoea
Lung auscultation may reveal squeaks and crackles at diaphragmatic lobes, abnormal lung sounds over tracheal bifurcation
Milk drop
Weight loss
(Severe cases) respiratory distress, gasping for air with outstretched head and neck, salivation, loss of appetite, fever

Question 6

What is the pre patent period of Dictyocaulus viviparus?

Answer 6

3 weeks

Question 7

How could Dictyocaulus viviparus result in severe pneumonia?

Answer 7

Eggs are inhaled into all areas of the lungs and inflammation commences

Question 8

How is lungworm in cattle diagnosed?

Answer 8

Usually from clinical signs, grazing history and relevant epidemiology
Demonstration of L1 larvae in faeces (flotation/Baermann technique)
Tracheal washes —> cytological evidence of eosinophilic inflammation
Bronchoscopy
Radiography
Demonstration of adult nematodes at necropsy

Question 9

How is lungworm in cattle treated?

Answer 9

Macrocyclic lactones and benzimidazoles are effective against larval and adult stages
Animals at pasture should be moved inside for treatment
Supportive therapy may be needed for complications. In severe cases maybe NSAIDs.

Question 10

Why has cattle lungworm increased over the years?

Answer 10

Increased reliance on anthelmintics meant no chance for animals to develop natural immunity
Climactic changes e.g. warmer and wetter spring/summer may favour survival of L3 on pasture

Question 11

T/F: there is a vaccine available for cattle lungworm

Answer 11

True
Huskvac
Must be given every year
2 doses 4 weeks apart; further 2 weeks then required before turnout in order to achieve protection

Question 12

T/F: cattle vaccinated against lungworm do not become infected in future.

Answer 12

False
Vaccine prevents clinical disease
Cattle may still become mildly infected, excrete larvae and therefore perpetuate further infection

Question 13

If a cattle slaughtered at the abattoir is found to have lungworm, what should you do?

Answer 13

Reject affected organ(s) as Category 2

Reject entire carcass as Category 2 if lungworm has caused pneumonia which is accompanied by emaciation/anaemia

Question 14

Describe the immune response to lungworm in cattle

Answer 14

Eosinophilia is seen in response to lungworm
Lungworm also elicits antibodies —> cows show an influx of activated T cells into the lungs
Repeated natural infections results in some level of immunity

Question 15

Lungworm larvae often make use of what in their environment to disperse themselves?

Answer 15

Fungal spores of Pilobolus

Question 16

Which kind of weather conditions favour lungworm in cattle?

Answer 16

Rain can disperse larvae in contaminated faeces
Warm, moist conditions keep infective larvae alive and encourage fungal growth
Generally, conditions which favour the growth of pasture also favour development of the infective larval stage L3

Question 17

When do lungworm outbreaks peak?

Answer 17

Late summer and early autumn

Question 18

Describe the name and composition of the vaccine for lungworm in cattle

Answer 18

Bovilis Huskvac
Live vaccine containing irradiated lungworm larvae
Oral administration

Question 19

Describe a possible farm control plan for lungworm in cattle

Answer 19

1) Vaccination of all cattle, then annual young stock vaccination
2) Quarantine and vaccination of all incoming cattle
3) Control by management/rotational grazing
4) Use of anthelmintics

Question 20

Which areas of Britain is cattle lungworm more prevalent?

Answer 20

Wetter, western areas

Question 21

You see a group of cattle coughing. In which group(s) would you be more suspicious of lungworm?

a) first season grazing calves
b) older milking cows
c) older beef cows

Answer 21

a) first season grazing calves

Question 22

When or why might a previously immune animal exhibit signs of lungworm infection?

Answer 22

If immunity has waned

If pasture infectivity is high

Question 23

How do cows become infected with Dictyocaulus viviparus?

Answer 23

Ingestion of infective L3 larvae on pasture

Question 24

Describe the life cycle of Dictyocaulus viviparus

Answer 24

Infective L3 are ingested on pasture
These migrate to the lungs where they develop into adults
Adults produce eggs in the lungs
Eggs hatch and L1 larvae are coughed up, then swallowed
L1 larvae pass into faeces, and develop in the environment into L3