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| *''Dictyocaulus viviparus'' causes [[Respiratory Parasitic Infections - Pathology#Dictyocaulus viviparus|parasitic bronchitis]] | | *''Dictyocaulus viviparus'' causes [[Respiratory Parasitic Infections - Pathology#Dictyocaulus viviparus|parasitic bronchitis]] |
| [[Parasitic Bronchitis - Cattle]] | | [[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>]] |
| + | [[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 |
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| + | *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 |
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| + | *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]] |
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| [[Category:Trichostrongyloidea]][[Category:Cattle_Nematodes]] | | [[Category:Trichostrongyloidea]][[Category:Cattle_Nematodes]] |
| [[Category:To_Do_-_Parasites]] | | [[Category:To_Do_-_Parasites]] |