When to WormTest and when to drench

When to WormTest and when to drench

In the Rangeland region, no drenches should be given routinely, apart from quarantine drenches for purchased goats (unless just captured), including bucks. Consideration could be given to drenching in unusual circumstances e.g. a predicted flood which would mean goats would be concentrated in smaller wet areas.

Why check worm burdens in goats?

Checking worm burdens with a WormTest is essential for correct and timely drenching decisions and to confirm that your worm control program is on track. The result is healthy goats, without unnecessary drenching. 

WormTests are the best basis for drenching decisions (Drench Decision Guides):

• To confirm whether signs of ill-health are likely to be due to worms. Many signs are not specific to worms, e.g. weight loss and poor growth rates, a weaker tail group lagging behind the others, scouring and possibly deaths. These signs occur well after production losses from worms are occurring in the herd.
• To check whether worm burdens are causing production loss, even though signs of worms are not present. Reduced weight gains and fibre growth occur well before signs of ill-health are seen.
• To show whether the number of worm eggs being passed onto pasture is too high for a particular time of year.
• To give early warning to prevent significant production losses (or where barber's pole worm exists, the risk of deaths).

Drenching based on WormTests is also the most cost-effective ongoing option for worm control in this region, as unnecessary drenching of large herds is expensive in both drench and labour costs.

How are worm burdens tested?

1.   Using WormTest

• Checking worm burdens throughout the year using WormTests is a critical part of the WormBoss worm control program. Most WormTests are done through a laboratory.
• Worm egg counts (but usually not larval cultures) can be done by producers if they have the equipment and skills. Ideally, producers should have their preparation and counting technique reviewed by an accredited laboratory and perform ongoing quality control checks, just like an accredited laboratory to ensure their results are correct.
• Seek professional advice where worm egg count results are not simple to interpret.

2.   Checking on farm

• Where it is not practical to conduct WormTests, FAMACHA^© (for barber’s pole worm only) and Body Condition Scoring (BCS) can be used to indicate if treatment is required.
  • For FAMACHA, check the eye mucous membrane (lower) – normal healthy goats have dark pink to red lower inner eye mucous membranes. Goats suffering from anaemia, which can occur with barber’s pole worm and liver fluke, will have paler membranes; in severe cases they can be almost white. The FAMACHA© scoring system evaluates the level of anaemia in the individual goat. 
  • For BCS, check the back region—use the lumbar vertebra for condition scoring in meat goats. A condition score of 2.5–3.0 is desirable while a score of 2.0 is too low, and above a score of 3.5 is too high. Does need to be in condition score 3.0 at kidding.

Which goats and how many should have a WormTest?

It is best to test each herd or group of goats separately as it is difficult to extrapolate worm egg count results from one group of goats to another, even of the same age or class.

There are usually differences between paddocks in the favourability for worm survival, the number of worm eggs being deposited by different groups of goats, and the time since a drench was given. In some cases, a drench may have been given to some goats but not to others.

When should WormTests and drenches be routinely done?

In this region there are only three situations when drenches should routinely be given.

• When bringing new goats onto the property
• When extensive flooding is predicted to isolate goats
• When nodule worm has been found to be a problem on your property (pimply gut)

Otherwise, always conduct a WormTest before drenching goats.

Use the results with the Drench Decision Guide to decide whether to drench and when other WormTests should be done. A larval culture (larval differentiation) with the WormTest is particularly useful in areas or seasons in which summer rainfall occurs and barber’s pole worm is a risk.

Young bucks under 2 years and weaners are highly susceptible to worms and should be regularly monitored.

WormTest 

• Goats showing signs that suggest a worm infection
  Scour worms: dark scours (or sometimes clotted dung instead of pellets); weight loss; death.
  Barber’s pole worm: anaemia (pale inside eyelids and gums); ‘bottle jaw’ (swelling under the jaw); lagging or collapse when mustered; death.
  Note: a WormTest can save an unnecessary drench if signs are from another cause, however, if severe anaemia and bottle jaw are noted, an immediate drench for barber's pole worm is usually warranted. A concurrent WormTest should also be carried out (take samples before drenching) to confirm the diagnosis, as similar signs may occur in this region from the blood parasite Mycoplasma ovis (formerly called Eperythrozoon ovis) and other causes.
• Prior to weaning kids (or at 4–6 months old if a set weaning does not occur)
  Kids are the most susceptible mob on the property: if only one drench is ever needed on a property it will be the weaning drench. If monitoring worm egg counts and productivity over a number of years shows drenching at weaning is not required on your property, only WormTest again at weaning if the conditions have been wetter than usual.
• 6 weeks after rain that has resulted in a green pick of annual grasses and herbage
  Generally, a single fall of rain won’t cause a significant increase in worms in this region. However, follow up rain sufficient to allow annual grasses to germinate and persist will also favour development of worm larvae; sometimes these can increase to a serious infection within a month or two.
• 4–6 weeks after goats have been congregating in small areas
  When goats are restricted to smaller areas, such as when paddocks are flooded, they are forced to re-graze areas more quickly and heavier than normal. The pasture becomes more contaminated with worm eggs and if conditions have favoured egg hatching, the goats will have higher worm infections.
• Each 2–3 months for goats on bore drains/irrigation channels when there is little other paddock feed
  In very dry times or drought (when worms are otherwise not expected), goats preferentially graze green pick along drains and channels. This can lead to higher levels of worm contamination along the drains, and infection and illness in the goats, compounded by the generally poorer condition of the goats in these times.
• In north-west Victoria and the western Riverina during November/December and February
  In years when winter and spring have been much wetter than usual check whether a first summer drench (November/December) and/or second summer drench (February) could be required. Under these conditions, consider a WormTest when the pasture is haying off and again in February.
• In southern Queensland, if autumn and winter were wet and the spring and summer is wet or likely to be wet
  WormTest each 4–8 weeks (depending on the amount of rainfall) until the season dries out.
• Before mustering for management events
  As goats are mustered infrequently in this region, it is good to conduct a WormTest before mustering for routine activities, rather than drenching ‘just in case’.

Drench

• In the situations listed above, drench if the mob’s WormTest result is equal to or above the threshold figures in the table below for the class of goat and the type of WormTest result
  Unless professionally advised, use an effective registered short-acting drench when treating for worms.
• Quarantine drench all introduced goats (including bucks)
  Use an effective short-acting drench that provides (for meat goats) four drench groups including one from either of the most recently available products or (for dairy goats) fenbendazole and abamectin, which are registered for use where milk is for human consumption. Goats coming from properties with liver fluke should also be treated with triclabendazole. If the goats being introduced are recently captured ferals this may not be needed.
• Drench when predicted extensive flooding is expected to isolate and restrict goats for some weeks
  Drench (without a prior WormTest) prior to the flood arrival. Generally, use an effective short-acting product, but consider a long-acting product only if goats are likely to be isolated for more than 6 weeks and they are in a summer rainfall area and ground conditions are wet. Then move goats to higher paddocks. Long-acting drenches are not registered for goats and in some states may need a veterinarian’s prescription.
• In May, if goats have been found to have nodule worm
  Nodule worm can be a problem in this area; check for signs in the intestines when any sheep or goats die or are killed for rations. Open the abdomen and find the large and small intestines. Examine the outside wall of each for firm white pimples or nodules. If these are present, you should routinely drench in May with a drench that contains either a macrocyclic lactone (ML) or a benzimidazole (BZ).

Table 1. Threshold worm egg counts at and above which goats should be drenched in the rangeland region.

Class of goat	No culture or culture has less than 60% barber’s pole (i.e. mostly scour worms)	Culture has more than 60% barber’s pole
Does (dry to mid-pregnancy) or wethers	400 epg	700 epg
Does pre-kidding	300 epg	300 epg
Goats under 18 months or bucks	300 epg	500 epg

 

 

 

 

 

 

 

 

When choosing the drench to use, refer to the next section in this program: ‘Managing drench resistance’.

For nodule worm, use a drench containing either a benzimidazole (BZ) or a macrocyclic lactone (ML) group.

The WormBoss website has a section on drenches where you can search on drench names, drench groups, or the parasite you wish to target.

What samples should be collected for WormTests?

Goats do not need to be yarded for a WormTest. Collect warm fresh dung from the paddock (but make sure that doe and kid samples are not mixed).

To conduct a WormTest obtain WormTest kits or sample collection details from your testing laboratory or advisor.

If you do your own worm egg counts, use the bulk sampling method where dung is collected into a single container.

• Collect 3 pellets per pile of dung from at least 20 individuals.
• Choose pellets of equal size so that each goat is equally represented.
• If dung consistency is runny, use a plastic spoon. Don’t avoid runny or soft dung.
• Collect kid and doe samples separately.

Avoid delays in transit (when worm eggs can hatch) by collecting and posting early in the week. Also ensure samples are kept cool (refrigerate but do not freeze) before sending, include an ice brick in transit in very hot weather and exclude as much air from the sample bags as possible.

Checking a mob of sheep or goats for worms with a WormTest

Assessing worm burdens without a WormTest