Lungworm Flashcards
Causative agent of lungworm in cattle, camelids and deer
Dictyocaulus viviparus
Epidemiology of lungworm in cattle - time of year
Major outbreaks July-September
When non-immune calves have been on pasture for 2-5 months and parasites have had time to reproduce
T/F: older animals are resistant to Dictyocaulus viviparus but can act as carriers, spreading infection without showing clinical signs
True
T/F: under favourable conditions, Dictyocaulus viviparus can overwinter on pasture
True
Clinical signs of Dictyocaulus viviparus infection
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
What is the pre patent period of Dictyocaulus viviparus?
3 weeks
How could Dictyocaulus viviparus result in severe pneumonia?
Eggs are inhaled into all areas of the lungs and inflammation commences
How is lungworm in cattle diagnosed?
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
How is lungworm in cattle treated?
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.
Why has cattle lungworm increased over the years?
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
T/F: there is a vaccine available for cattle lungworm
True
Huskvac
Must be given every year
2 doses 4 weeks apart; further 2 weeks then required before turnout in order to achieve protection
T/F: cattle vaccinated against lungworm do not become infected in future.
False
Vaccine prevents clinical disease
Cattle may still become mildly infected, excrete larvae and therefore perpetuate further infection
If a cattle slaughtered at the abattoir is found to have lungworm, what should you do?
Reject affected organ(s) as Category 2
Reject entire carcass as Category 2 if lungworm has caused pneumonia which is accompanied by emaciation/anaemia
Describe the immune response to lungworm in cattle
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
Lungworm larvae often make use of what in their environment to disperse themselves?
Fungal spores of Pilobolus
Which kind of weather conditions favour lungworm in cattle?
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
When do lungworm outbreaks peak?
Late summer and early autumn
Describe the name and composition of the vaccine for lungworm in cattle
Bovilis Huskvac
Live vaccine containing irradiated lungworm larvae
Oral administration
Describe a possible farm control plan for lungworm in cattle
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
Which areas of Britain is cattle lungworm more prevalent?
Wetter, western areas
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
a) first season grazing calves
When or why might a previously immune animal exhibit signs of lungworm infection?
If immunity has waned
If pasture infectivity is high
How do cows become infected with Dictyocaulus viviparus?
Ingestion of infective L3 larvae on pasture
Describe the life cycle of Dictyocaulus viviparus
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
