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| − | ==Clinical==
| + | #redirect[[Dictyocaulus viviparus]] |
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| − | *''Dictyocaulus viviparus'' causes [[Respiratory Parasitic Infections - Pathology#Dictyocaulus viviparus|parasitic bronchitis]]
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| − | [[Parasitic Bronchitis - Cattle]] | |
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| − | [[Image:Dictyocaulus viviparus.jpg|right|thumb|100px|<small><center>Dictyocaulus viviparus (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | [[Image:Parasitic bronchitis.jpg|right|thumb|100px|<small><center>Parasitic bronchitis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | *Found in [[Tracheitis#Infectious causes of tracheitis|trachea]] and [[Bronchitis#Infectious causes of bronchitis or bronchiolitis|large bronchi]]
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| − | *Causes parasitic bronchitis, synonyms: bovine dictyocauliosis, husk, hoose
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| − | *Primary infection:
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| − | **Penetration phase (week 1)
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| − | ***Larvae migrate to lungs, no clinical signs
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| − | **Prepatent phase (weeks 1-3)
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| − | ***Development and migration of larvae -> [[Bronchitis#Bronchiolitis|bronchiolitis]] -> eosinophilic exudate -> air passage blocked -> alveolar collapse (distal to blockage) -> clinical signs (tachypnoea, coughing)
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| − | **Patent phase (weeks 4-8)
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| − | ***Egg-producing mature worms
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| − | ***[[Bronchitis|Bronchitis]] - due to mature worms
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| − | ***[[Lungs Inflammatory - Pathology#Verminous pneumonia|Parasitic pneumonia]] - due to aspiration of eggs and larvae -> cellular infiltration of [[Neutrophils|neutrophils]], macrophages, giant cells
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| − | **Postpatent phase (weeks 8-12)
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| − | ***Majority of worms are expelled
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| − | ***In 25% of cases clinical signs may reappear as a result of alveolar epithelialisation
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| − | ***May be together with [[Lungs Ventilation - Pathology#Emphysema|interstitial emphysema]] and [[Lungs Circulatory - Pathology#Pulmonary oedema|pulmonary oedema]], or secondary bacterial infection
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| − | *Reinfection syndrome:
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| − | **Immune cattle show clinical signs only if exposed to large numbers
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| − | **Pathogenesis - large numbers of larvae reach bronchioles where they are killed by immune response
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| − | **Pathology - parasite granulomata (grey-green, 5mm diameter, macrophages, giant cells, eosinophils) and eosinophilic plugs in bronchioles
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| − | <small>Above from RVC Parasitology study guide (2005-2006)</small>
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| − | *Preferentially in dorsocaudaland ventrocaudal regions
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| − | *Histologically
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| − | **Bronchial epithelium may show hyperplasia due to the chronic irritation
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| − | **Cross-sections of the parasites
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| − | **Exudate contains many eosinophils
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| − | **Foci of necrosis in the rest of the lung tissue due to aspiration of eggs and larvae fromhese adults
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| − | **In mild infestations, the adults are normally expelled in two months - self cure
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| − | *Repeated infestation and secondary bacterial infection are common
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| − | *Two other types of lesion in lung tissue due to this worm have been reported:
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| − | **Nodules (2-4mm in diameter) with greenish centres in the reinfection of an immune animal - the host mounting a successful defence and preventing larval migration
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| − | **Pulmonary oedema and emphysema - thought to be a hypersensitivity response to a massive invasion of larvae in previously- sensitised animals - the gross and microscopic appearance is similar to that of [[Lungs Inflammatory - Pathology#Acute bovine pulmonary emphysema and oedema (ABPEE)|fog fever]]
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