Gastrointestinal worms are a very common problem associated with sick goats, especially kids and does in late pregnancy or early lactation, with all goats having some degree of parasitism. Goats also share many common worms with sheep and alpacas, and can become infected with some cattle species of roundworm. Animals are infected when eating pasture contaminated with the larval stage of the gastrointestinal worm. After ingestion, the larvae mature into adult worms in the gastrointestinal tract and will start producing eggs. These eggs are passed onto the pasture through the animal’s faeces and mature into the infective larval stage.
Figure 1, Roundworm lifecycle in goats. Obtained from http://www.wormboss.com.au/worms/roundworms/roundworm-life-cycle.php
Disease caused by gastrointestinal parasites is multifactorial and depends on the number and density of animals on a property, size or number of pastures and the availability of safe pastures, immune status, nutrition and health of individual animals as well as the presence of worms that are resistant to commonly used medications used to treat them. The weather also influences how quickly larvae develop on pasture, with prolonged dry periods lower risk compared to wetter, warmer weather. Faecal testing should be considered every 4-6 weeks in summer and 4-8 weeks in winter, especially if there has been significant rain (20mm+) followed by more rain (10mm+) within a few weeks.
Affected animals may exhibit various symptoms if they are suffering from heavy worm burdens. These can be ill-thrift, unkempt coat or weight loss, diarrhoea, lethargy, pale gums and conjunctiva, swollen jaw or abdomen, or even collapse and death. It is important to body condition score your animals to ensure that emaciated or underweight animals are identified. Very prominent, sharp vertebrae and ribs with little back fat covering are suggestive of poor body condition and warrant investigation. Weight loss and ill thrift are symptoms that are caused by a variety of diseases, and animals that are sick will have a compromised immune system predisposing them to higher worm burdens at the same time. It is also important to recognise that some species of worms are associated with more severe disease, particularly Barber’s Pole (Haemonchus contortus). Goats affected by Haemonchus will show symptoms of anaemia (pale conjunctiva and gums), submandibular swellings (bottle jaw), severe lethargy or death. A faecal sample can be taken and quickly tested at the clinic to look for worm eggs. If deaths have occurred, a post mortem examination can be performed.
Anthelmintic drenches are used to treat worm burdens. There are a number of registered drenches for use in goats and in some cases sheep drenches can be used. It is important to know that goats will metabolise these chemicals at a faster rate than sheep, and so a different dose rate is used so that an effective dose is given. Pour on drenches have been shown to be ineffective in killing worms in goats, and drenches registered for use in horse or cattle should NEVER be used in goats. Withholding periods and DO NOT USE directions must be strictly adhered to and drenches must be used judiciously to minimise the development of drench resistance. Drench resistance and usage can be minimised by using low worm burden pastures. This involves spelling pastures from being grazed by goats (3 months rest for autumn use and 5-6 months for spring use) or rotating pasture use with cattle (note that goats can become infected with cattle Ostertagia species). Strategic use of drenches will also ensure their efficacy. We recommend a quarantine drench for all stock coming onto a property using a drench including 3 or 4 drench groups or fenbendazole/abamectin in the case of dairy goats where milk is to be used for human consumption. It is important to remember that recently drenched goats will continue to shed eggs already produced in their intestines for 3-4 days after a drench. Thus, a period of 3-4 days should be given prior to moving drenched animals onto clean or uncontaminated pasture. Pre-kidding does suffer a decrease in their natural immunity and should be drenched 4 weeks prior to kidding. Kids should be drenched at weaning and animals showing symptoms suggestive of worms should be individually drenched. Your veterinarian should examine individuals not responsive to initial treatment.
Pasture and parasite management in goats is a complex issue, if you have any questions regarding parasites and the health of your herd, be it an individual or a number of animals, please don’t hesitate to contact the friendly staff at Albion Park and Gerringong Veterinary Hospitals.
Figure 2- Body condition scoring in goats. Obtained from http://agriculture.vic.gov.au/__data/assets/image/0014/260141/Goats-Welfare-Appendix-1.gif