Difference between revisions of "Dictyocaulosis - Cattle"

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==Clinical==
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#redirect[[Dictyocaulus viviparus]]
 
 
*''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 [[Tracheitis#Infectious causes of tracheitis|trachea]] and [[Bronchitis#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 -> [[Bronchitis#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
 
***[[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]]
 

Latest revision as of 21:48, 28 March 2011