November 2020

Thankful for cattle parasites

​A beef cattle herd located in central Oklahoma, started showing weight loss over the past few months. Five cows died during the last week of October.  One of the cows was submitted for necropsy and the following parasites were found on the trachea. 

Image 1: ​Anterior end of worm

Image 2: Caudal portion of a male worm.

​Image 3: Larvated eggs recovered from adult females

Images 5–7: Larva hatching from an egg

What's your diagnosis?

Dictyocaulus spp.

Adults: Up to 3 inches long, white in color. Found in the bronchial tree, where they cause chronic bronchitis and localized occlusion of the bronchial tree. Adults of Dictyocaulus viviparus are the only parasites that reach maturity in the lungs of cattle. 
 
Eggs: Contain a vermiform embryo that usually hatches before is eliminated in the feces (Images 5–7). While in the environment these larvae derive their energy from stored food materials ‘food granules’. Development to the infective stage requires about five weeks, and prepatent period is approximately one month.