Others cause malnutrition-like symptoms due to decreased appetite, diarrhea, and loss of nutrients, including protein, into the digestive tract. Mixed infections also may contribute to the severity of the problem in many cases. Signs of gastrointestinal worm parasitism may vary depending upon severity of infestation, general health of the animals involved, and other factors. Animals showing signs of severe parasitism generally will be quite unthrifty in appearance. They may be off feed, suffer severe weight loss, have diarrhea, and be severely anemic.
Death can occur in severely affected animals.
Less severely affected or chronically parasitized sheep show lesser signs of parasitism. These animals may show intermittent diarrhea, weight loss or reduced weight gains, reduced wool production, decreased milk yield, and poor reproductive performance. Inapparent or subclinical parasitism may be the most costly. These animals may show no outward signs which can be attributed directly to worm parasites, but they actually are not producing to their optimum potential. Susceptibility to secondary disease, such as pneumonia, may increase in these, as well as in other acute and chronic infestations.