Parasitic nematodes or internal parasites or worms as they are commonly known, are the biggest health issue for goats in Australia, particularly in higher rainfall areas. Worms cause production losses which can affect the animal before it starts showing physical signs or deaths occur. Worms have a high cost of treatment and management.
Types of Parasites
Goats and sheep share similar parasites. These include gastrointestinal parasites (round worms, liver fluke, intestinal coccidia, tapeworms), and lungworms. Goats and sheep don’t share many of the same worms with cattle, apart from liver fluke.
As with sheep, the most important internal parasites of goats in Australia are:
- Haemonchus contortus (barber’s pole worm)
- Trichostrongylus species (sp) (black scour worm)
- Teladorsagia sp (small brown stomach worm)
The three worms above are widespread, with barber’s pole worm especially being a problem in summer rainfall areas with average annual rainfall above 500-600mm. Fasciola hepatica (liver fluke) mainly occurs in higher rainfall areas (>650mm a year) of southeastern Australia, including tablelands and nearby areas, and some irrigation areas due to the host snail living along slow moving streams and irrigation channels.
Lifecycle of Worms
1. Egg Stage:
- The lifecycle begins with adult worms residing in the goats gastrointestinal tract
- Female worms lay eggs that are passed out in the goat’s dung/faeces
2. Larval Stage (Outside the Goat):
- Eggs hatch in the environment, typically on pasture or in bedding
- Larvae develop and go through several moulting stages (L1 and L2)
3. Infective Larval Stage
- Larvae mature into an infective stage known as the third-stage larvae (L3)
- These L3 larvae are the stage that goats ingest to become infected
- Goats ingest infective L3 larvae while grazing or by ingesting contaminated food, water or bedding
5. Gastrointestinal Stage:
- Once ingested, L3 larvae develop into adult worms in the goat’s gastrointestinal tract
- Adult worms attach to the lining of the stomach or intestines and reproduce and lay eggs, repeating the cycle
The lifecycle varies slightly among different types of internal parasites, such as gastrointestinal nematodes, lungworms and coccidia, but the general pattern involves eggs being shed, developing into infective larvae in the environment, and being ingested by goats to complete the cycle.
Signs of a Worm Burden
Signs of a worm burden or internal parasite infestation in goats can vary depending on the type and severity of the infestation.
Common signs to look out for include:
- Weight loss
- Anaemia: Worms, especially blood-sucking parasites like the barber’s pole worm, can causeanaemia, leading to pale mucous membranes (gums and eyelids). Assess using a FAMACHA chart.
- Diarrhea or soft faeces: Consistency and colour of faeces can change, often becoming more liquid and darker.
- Rough coat
- Bottle jaw
- Reduced milk production
- Coughing: Lungworm infestations may cause goats to cough, particularly when the parasites affect the respiratory system.
- Unthriftiness/lack of energy
- Death: In severe cases or if left untreated, internal parasite infestations can be fatal, especially in young or immunocompromised goats.
It’s important to note that some goats may not show obvious signs of infestation until the worm burden becomes severe. Regular monitoring through worm egg counts (WEC) and the use of the FAMACHA system (for anaemia assessment) can help detect and manage internal parasite infestations before they become critical. Timely treatment and proper prevention measures are essential for maintaining the health and productivity of goats. Consultation with a veterinarian is recommended to confirm and address any suspected worm infestations in your goat herd.
Managing Worms
Managing, controlling and treating worms in goats requires multiple components which are most effective when used in combination.
1. Worm Egg Counts (WEC): Perform WEC tests at recommended times to assess the level of worm infestation in your goats. This helps determine if treatment is necessary and which goats require it. For more information, click here.
2. Selective treatment: Only treat goats that have high WEC counts or show clinical signs of infestation. This helps manage drench resistance.
Every time an effective goat treatment is required to control worms, a goat owner should consider the four ‘R’s:
- The use of REGISTERED drenches
- Chemical RESIDUES following treatment
- Worm RESISTANCE to drenches
- The number of parasites in REFUGIA (number of parasites that have not been exposed to a drench)
Consult with a veterinarian to determine the most effective treatment and drench test every 2-3 years.
3. Grazing Management: Implement rotational grazing practices to prevent overgrazing and reduce parasite contamination of pastures. Allow pastures to rest between goat rotations to break the parasite lifecycle.
Browse plants, such as lucerne, leguminous crops and saltbush to reduce worm contamination on pastures.
Grazing cattle alongside goats can reduce contamination risks for goats.
4. Quarantine and Biosecurity: Drench and quarantine all new goats for at least 21 days before introducing them to the herd.
5. Genetic Selection: Breeding for resistance to internal parasites can help reduce susceptibility in your herd over time.
6. Record Keeping: Maintain detailed records of drench treatments, WEC results, and goat health status to track trends and make informed decisions.
7. Regular Monitoring: Continuously monitor the health and condition of your goats for early signs of infestations.
8. Consult a veterinarian: Seek veterinary advice for accurate diagnosis, treatment plans, and periodic check-ups for your goat herd.