Ostertagia ostertagi primarily causes disease in cattle by what mechanism?

Ostertagia ostertagi, a type of stomach worm affecting cattle, primarily causes disease through the destruction of the abomasal glands due to larval growth. As the larvae penetrate and develop within the gastric glands of the abomasum (the equivalent of the human stomach), they disrupt the normal architecture and function of these glands. This results in a significant impairment of digestive enzyme production and acid secretion, leading to clinical signs such as diarrhea, weight loss, and reduced appetite, collectively referred to as "bovine parasitic gastroenteritis."

The impact on the abomasal glands is critical for understanding the pathophysiology of the disease. The loss of functionality in these glands allows for increased gastric pH, which can further contribute to nutrient malabsorption and gastrointestinal upset. Consequently, the primary mechanism through which Ostertagia ostertagi inflicts harm on cattle is by damaging these essential gastric structures, rather than through processes like causing anemia, producing intestinal blockage, or skin infestations.