- You are called to investigate a beef cattle operation where several young adults (1-2 years of age) have developed acute, watery diarrhea (see image). One of the affected cows died and a necropsy reveals worms and petechiae in the abomasum. The wall of the abomasum has a nodular “cobblestone” appearance that is most severe in the fundic region. Which of the following agents is most likely?
- This is a description of type II ostertagiasis. The other parasites listed could be differentials with the exception of Dictyocaulus which is a lungworm. The main reason that Ostertagia is the best answer is the description of the abomasum. The cobblestone appearance which is also sometimes described as having a Moroccon leather appearance is essentially pathognomonic for Ostertagia. This occurs because Ostertagia larva undergo hypobiosis (larval inhibition) and lay dormant in the early fourth larval stage within the glands of the abomasum, forming the nodules. They resume development and emerge seasonally leading to severe signs.