Pathogenicity and Symptoms

The primary pathogenic effect of H. placei is blood loss caused by the adult worms feeding in the abomasum. This leads to anemia, or a low red blood cell count, weakness and lethargy. One of the most characteristic signs of a Haemonchus infection is the presence of edema or fluid accumulation in the lower abdomen and under the jaw known as bottle jaw. Affected cattle may also show signs of weight loss, reduced milk production, and diarrhea, especially in heavy infections. Even with a lack of clinical signs, Haemonchus infections can reduce overall productivity due to decreased feed efficiency and lower growth rates in growing cattle.