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