‘Next-level’ worm control for healthy goat herds

Goat producers around Australia are grappling with worms this year. The reason?

Successive seasons with wetter weather have laid the foundations for massive worm larval contamination of pastures. This means that goats are continually re-exposed to worm infections, even after they’ve just been treated. Here we examine the fundamentals of a healthy goat herd, using knowledge of goat physiology and nutrition as well as worm biology and drenches to help you work towards your healthiest herd ever.

Impact of worms

Worms suck blood and destroy tissue in the stomach and intestines resulting in blood loss, poor digestion and absorption of nutrients, lower production of milk and fibre, poor animal welfare and sometimes death. Common signs in herds of goats include anaemia (pale gum or eye colour), scours, dags around the tail, low body condition, weakness and inability to exercise. Worm infestations also make goats more susceptible to other diseases and tapeworms may affect meat quality and human health e.g. hydatids, bladder worm, sheep (goat) measles.

Worm biology and life cycle

The 3 most common worms in goats (barber’s pole worm, black scour worm, brown stomach worm) take a minimum of 4 days to develop in warm wet conditions from eggs to infective larvae (stage 3) on pasture. Once eaten by the goat, they take 14-21 days to develop from infective larvae to adults, when they start laying eggs.

This means if you put goats onto a clean paddock:

1. they will begin to pick up infective larvae (auto-infection from their own worm egg output) only 4 days after introduction.
2. they will be re-infected with worm larvae (second generation auto-infection) about 21 days after introduction.

Other worms

Goats will often have infections with other roundworms including the thin-necked intestinal worm (Nematodirus). They are also susceptible to liver fluke and lungworms. These have indirect life cycles involving small snails that live in wet areas. These cause damage to liver and lungs respectively, leading to poor health, anaemia, jaundice, coughing and sometimes death.

Diagnostics

Worm eggs passed in the goat’s dung can be counted under the microscope in a laboratory. This gives an indication of how bad the worm infestation is and what type of worm is present (larval culture and worm identification). These tests will also show the presence of coccidia. Worm egg counts (WECs) done after treatment will also tell you how well a drench (treatment) has worked against the worms present. Liver fluke and lung worms can be diagnosed using a sedimentation test on dung samples.

Consult your veterinarian or ParaBoss WEC QA pages for diagnostic test providers.

Drench selection

In general, drenches (anthelmintics) don’t work well in goats, due to the goat’s natural ability to detoxify external substances. Because of low absorption, pour-on drenches are very poor at killing worms in goats, despite some being used overseas. Injectable products also fail to provide the protection they do in sheep.

Incorrect use (underdosing, frequent use, using single active products, failing to rotate, long-acting products) of goat drenches leads to rapid onset of resistance. Use the Drench Decision Guide to know when to drench.

Before using a drench, check the goat dose rate, which is different from the label dose rate for sheep. Your veterinarian is qualified to provide detailed advice on dose rates and drench selection, which involves off-label use. Doing a worm egg count and worm ID 14 days after drenching will tell you how well the drench worked. A quarantine drench is essential when bringing new goats onto your property.

Toxicity

Some drenches are harmful, especially to young goats. Weigh goats prior to dosing to ensure the correct dose without risk of toxicity. Where possible, avoid drenches in young goats or use drenches with low toxicity. Active ingredients with highest toxicity for goats include abamectin (drowsiness, coma in young animals), levamisole (neurological signs), albendazole (bone marrow depression) and closantel (blindness). Check product labels for ‘contraindications’- or warnings for when products should not be used.

Residues

The National Residues Survey monitors the level of residues in products from goats. Unfortunately, there have been unacceptable levels in recent years, posing a risk to trade. Care should be taken to observe withholding periods for meat and milk for all products used on goats.

Read about using management tools to create healthy goat herds here.