Dictyocaulus Viviparus

Causes parasitic bronchitis 'husk' in cattle. Common in the wetter west UK. 

• Trichostrongyle superfamily (not metastrongyle like the other lungworms).
• D.viviparus-> cattle. D.filaria-> sheep. D.arnifieldi-> horse respiratory disease. Patent donkey infection (carriers).
• Trachea & bronchi. 

Life Cycle

• Direct life cycle. Female ovoviviparus-> gives birth to larvated eggs which hatch immediately.
• L1 in lungs, coughed up, swallowed and pass out in the faces.
• Lympho-tracheal migration. 

L3 infective stage. L1-L3 stages all ensheathed to protect them from adverse weather conditions. Takes 5-7 days to develop. 

ppp= 25 days (slightly longer than nematodirus, PGE and ostertagia). 

1. Penetration Phase

• 0-7 days.
• Lymph-tracheal migration (mesenteric lymph nodes). Moults to L4 in the lymph node. L4 in the lung.

2. Pre-patent phase. 

• 8-25 days. 
• L4-L5 in lungs. L5 migrate UP the bronchial tree so the adults reside in the bronchi and trachea. 

Clinical Signs 

• Intense inflammatory response-> bronchitis & bronchiolitis. 
• Interstitial emphysema. 
• Pulmonary oedema-> coughing. 
• Respiratory distess & tachypnoea.
• Weight loss. 

3. Patent Phase

• 26-55 days.
• Adult worms in upper respiratory tract. Eggs and L1 in alveoli. 

Clinical Signs

• Intense inflammatory response.
• Frothy white mucus.
• Emphysema & hypoxia.
• Gasping & coughing.
• Possible death. 

4. Post-patent phase

• 55+ days.
• Immune expulsion of adults and protective immunity.

Clinical Signs

• Some animals epitheliation of the lung tissue & never completely recover. 

Epidemiology

• Unpredictable.

Factors affecting the pre-parasitic stages:

1. Temperature.
2. Moisture.
3. L3 dispersal by Pilobolus Fungi.

L3 overwinter. L1 are also shed by carrier animals.

Disease= AUGUST-> SEPTEMBER. Same as ostertagia etc. 

• Dairy replacement calves.
• First cycle= few L3 so no disease.
• L1 shed->L3.

Only 1000 worms are needed to cause clinical disease. Disease is from turn out to november. Immunity is short lived and needs continual boosting. 

Diagnosis

• Antibody detection ELISA.
• Treat-> anthelmintics, NSAIDS for inflammatory reaction & antibiotics to protect against secondary infection.
• House most severely affected calves.

Control

• No intermediate host.
• No immunity- adult cattle naive and at risk. 
• More break outs in adult cattle than calves.

Vaccines

• Huskvac.
• 1000 live attenuated irridated L3 given orally. 
• Give before turnout.
• Needs natural immunity boosting.