Cattle Lungworms

Question 1

What are the two superfamilies of lungworms in large ruminants?

Do they have direct or indirect life cycles?

Are they pathogenic or non-pathogenic?

Answer 1

1. Trichostrongyloidea - direct LC
   
   • Dictycaulus
2. Metastrongyloidea - indirect LC
   
   • Metastrongylus

• Trichostrongyloidea - pathogenic
• Metastrongyloidea - non-pathogenic

Question 2

What is the life cycle of Dictycaulus viviparus?

What animal(s) do these parasites infect?

Answer 2

• Direct
• L3 is infective
• PPP ~4 weeks
• Site of infection - bonchioles (young adult worms) and bronchi / trachea (adult worms)
• Affect cattle
• Adult worms in mainstem bronchi / trachea and produce eggs
• Eggs hatch in lungs and L1 migrate up trachea and are swallowed
• L1 in feces, matures to L3
• Ingestion of L3 and penetration of intestinal mucosa
• L3 travel to mesenteric lymph nodes where they mature to L4
• L4 via lymph and blood to lungs where they break out of the capillaries and into the alvioli (about 1 week after infection)
• L4 to adult in bronchioles, then migration to mainstem bronchi / trachea

Question 3

How is diagnosis made for Dictycaulus viviparus?

Answer 3

• Clinical signs and time of year (July - Sept/Oct)
• Grazing / vax / anthelmintic hx
• L1 present in feces - not present during pre-patent phase so collect from a number of affected individuals. Collect from rectum to eliminate contamination of sample by pasture.
• Use Baermann apparatus for detection of L1 in feces
• Dark food granules in intestine of L1
• Also, broncho-alveolar lavage, eosinophilia
• ELISA - detects antibody to adult and L3 antigens

Question 4

Is there a good immune response to Dictycaulus viviparus?

Answer 4

• Yes
• But, imm response could lead to pathology

Question 5

What are some clinical signs of Dictycaulus viviparus?

What is the dz called?

Answer 5

• It is called Parasitic Bronchitis

1. Mildly affected
   
   • intermittant cough
2. Moderately affected
   
   • coughing at rest, tachypnea, crackles in posterior lung lobes
3. Severely affected
   
   • harsh cough, tachypnea, dyspnea, mouth breathing
   • Pyrexia - due to secondary bacterial infection

Question 6

What is the pathogenesis of Dictycaulus viviparus?

Answer 6

1. Penetration phase
   
   • days 1-7. Larva migrating to lungs. No pathology.
2. Pre-patent phase
   
   • days 8-25. Larva migrating up through lungs
3. Patent phase
   
   • days 26-60. Mature adults in airways
4. Post-patent phase
   
   • days 61-90. Adults expelled from airways. Recovery period.

Question 7

During the pre-patent phase of Dictycaulus infection, what is causing the pathology?

Answer 7

• Days 8-25
• L4’s and young adults migrating through the alveoli and up the respiratory tree
• There is an acute inflammatory response from monocytes and eosinophils
• Collapse of the alveoli due to mucus / cellular plugs
• This is the time where clinical signs are first seen
• If the infection is heavy enough, calves can die from days 15+

Question 8

During the patent phase of Dictycaulus viviparus infection, what is causing patholgoy?

Answer 8

• days 26-60
• Lesions from two main causes
  
  1. Worms in bronchi - parasitic bronchitis
     
     • profuse inflammatory exudate
     • hyperplasia of bronchial epithelium
     • interstitial emphesema and edema
     • Eosinophils!
  2. Aspiration of eggs / larva - parasitic pneumonia
     
     • aspiration of eggs / larva into alveoli

Question 9

During the post-patent phase of Dictycaulus viviparus infection, what is causing the pathogenesis?

Answer 9

• Most animals show gradual recovery with subsequent strong acquired immunity
  
  • expulsion of adult worms is due to immune response
• Some animals show an increase in clinical signs, which can be fatal
  
  • due to either “alveolar epithelialization”, or Bacterial Infection

Question 10

What is the epidemiology of Dictycaulus viviparus?

Adult cattle or calf disease?

Answer 10

• Temperate regions with high rainfall
• Usually July - Sept / Oct
• L3’s can overwinter
• Carrier animals
• Traditionally it was a dz of 1st season grazing calves. Now, its is common in adult cattle.

Question 11

Why is lungworm (Dictycaulus viviparus) now common in adult cattle?

also, lungworm in cattle can be called Husk

Answer 11

• No previous hx of lungworm or vax (so no immunity)
• Anthelminitic use in first and second years (so no immunity)
• Susceptible to heavy challenge (because no immunity)

Question 12

What are some ways to prevent bovine lungworm / Husk / Dictycaulus viviparus infection?

Answer 12

• Vax with irradiated L3 vax (2 doses)
• Vax 1st season calves before turnout
• Effective but not sterile immunity - so don’t mix with unvaccinated
• Immunity can be boosted by infection

Question 13

How do you treat bovine lungworm / Husk / Dictycaulus viviparus?

Answer 13

1. Mildly affected
   
   • treat with anthelmintics (ivermectin, Levamisole) and move to clean pasture
2. Severely affected
   
   • treat with anthelmintics, house, hydrate, NSAIDs, abx if pyrexic
   • Caution - treatment with anthelmintics may exacerbate clinical signs due to parasite death