Observations of physical signs

Determining which worm species are present and faecal worm egg counts (WECs) is important but must be balanced against other factors that affect the productivity and health of the cattle. Individual cattle show different degrees of response to worm burdens, in young cattle even mild burdens result in a loss of appetite, known as ‘parasite-associated anorexia’. Along with metabolic and direct parasitic effects, reduced feed intake leads to slower growth rates and weight loss. Other signs of worm burdens include scouring (diarrhoea), or for barber’s pole worm (Haemonchus placei), pale mucous membranes, indicating anaemia.

Figure 1. Cattle with scours show possible signs of worms, drenching may be of benefit. Image courtesy of Jenny Cotter

Table 1: Signs of worm infestations in cattle




Weight loss or reduced weight gains

Cattle weights or growth rates lower than expected.

Major effect of worms, indicates heavy infections if obvious, but may be evident only when cattle are weighed.

Body condition score

Decreases with worm burdens, in parallel with weight loss.

Is a measure of the fat and muscle covering the bony frame of a cow regardless of frame-size. There are different scoring systems for beef cows (1-5) versus dairy cows (1-8) with considerations of whether a Bos indicus, Bos taurus or a cross is being assessed. Measured generally from 1 (skinny) to 5 (or 8, fat).


Dags, dried faecal staining around and on tail and back legs.

Common with worms, but many other causes, such as high water content of feed e.g. new rich pasture. May need veterinary diagnosis.


Mucous membranes pale with high worm burden.

Safely observed by looking at the colour of conjunctiva (tissue lining the eyelids and covering the white of the eye) or parting the lips of the vulva in a restrained female.


Less time spent grazing with high worm burden.

May also affect rumen fill and cud-chewing time. Modern technologies such as GPS and activity trackers can accurately measure animal activity.

Bottle jaw

Soft fluid swelling under jaw.

A less common sign of barber’s pole worm or liver fluke infection caused by low blood proteins.

Milk production

Low milk production.

Largely related to decreased feed intake and higher protein losses.