INTERPRETING ROUNDWORM EGG COUNT RESULTS
It is very difficult to give hard and fast rules on interpreting egg counts, as there are so many variables to consider. These include:
Age of Animals:
Adult dry animals in good condition tolerate worms much better than young or poor animals.
Nutritional Status & Paddock Conditions: Well-nourished animals develop stronger immunity to worms faster and so withstand a worm challenge better than poorer animals. Sometimes moving animals onto a better paddock is as good as a drench.
Physiological Status: Are these animals young and growing, pregnant or rearing young? All these factors can place added stress on their systems and render them more susceptible to worm infestations. Young animals, such as weaners, are an important group to sample because they tend to be quite vulnerable to worms.
Weather Conditions & Outlook: Seasonal weather conditions need to also be considered and how they will impact your livestock and the worm numbers in the paddock. Warm, moist conditions can cause worm numbers to increase and become a problem very quickly.
Grazing & Management: Cross grazing can be an effective tool if you graze more than one species. Most worms are species specific and do not infect other types of animals. It can be a useful way of cleaning up the numbers of eggs and larvae on your pasture, as they do not survive in the second animal species. The only worms capable of infecting both sheep and cattle are Barbers Pole Worm and Stomach Hair Worm (T. axei)
Spelling paddocks can be useful but the length of time required will depend on weather conditions, pasture length and the types of worms present. Some worms can survive for a number of years. Short term spelling has little effect on worm control. Studies show a paddock would have to be rested for more than 10 weeks in the autumn and winter months to have a significant impact on reducing the numbers of worm larvae present.
If animals are to be mustered for some other reason, you may decide to drench based on egg count as well as convenience.
Worm egg counts considered with the other factors listed gives you the power to make an informed decision.
The table below offers a guide to egg counts. It is not hard and fast for many reasons, which include those stated above.
StockWatch suggests you contact your vet for the best advice.
What do my results mean?
epg (eggs per gram)
Remember young animals are more vulnerable to the effects of worm infestation and may require treatment at lower levels.
| Sheep, Goats, Alpaca, Deer | Cattle | Horses |
|---|---|---|
| < 200 epg: Drench probably not required | < 50 epg: Drench probably not required | < 200 epg: Drench probably not required |
| 200 – 500 epg: Seek Advice | 50 – 100 epg: Seek Advice | 200 – 500 epg: Seek Advice |
| > 500 epg: Drenching required | > 100 epg: Drenching required | > 500 epg: Drenching required |
Your Report:
The report shows numbers of roundworm eggs present split into two groups (Strongyle and Nematodirus). Larval culturing and differentiation is available for those requiring the breakdown of the exact species present. Your report will also provide a comment on the level of Coccidia cysts and Tapeworm eggs if observed.
Nematodirus sp:
Thin Necked Intestinal Worm: Occurs in most of the major sheep production areas of Australia and is mostly an issue in the winter rainfall districts. It can cause scouring in young sheep. It is very resilient and survives severe winters and dry conditions. Heavy infections of thin necked intestinal worms can cause diarrhoea in lambs. Thin necked intestinal worm can be a serious problem in young sheep in cool regions or after dry periods when sheep graze short, green feed. In sheep with heavy infections, tangled masses of worms are found in the lower part of the small intestine.
Strongyle sp: Includes most of the significant worm species such as:
Barbers Pole Worm: (Haemonchus spp.) Cause anaemia as they suck blood from the lining of the stomach. Signs of a heavy infestation include lack of stamina, pale gums, and possibly bottle-jaw and constipation. Keep an eye on stock in the warmer moist months as levels can escalate very quickly.
Dipstick Test: tests the level of blood present in a mob dung sample
| Negative | No blood present in the sample provided | Monitor |
|---|---|---|
| Low | May indicate a low level or early stage infection | Monitor |
| Moderate | A percentage of the mob is significantly infected | Consider treatment |
| High | Severe infection and deaths are likely to occur | Immediate Treatment Required |
Brown Stomach Worm: (Ostertagia spp) Damage the lining of the stomach as they mature. Stock with heavy infections of this type will lose condition quickly, scour profusely and may die. Animals with a lower burden are unthrifty and daggy. Burdens as low as 150 epg can cause ill-thrift in young cattle.
Black Scour Worm: (Trichostrongylus spp.) Damage the lining of the first three metres of the small intestine. Stock with heavy infections of black scour worms may lose condition very quickly and develop scours, which may be black. In young cattle burdens of 50 epg in cattle can cause ill-thrift.
What else do we report?
StockWatch Faecal Egg Counts (FEC’S) will also report if Coccidia and Tapeworm eggs are present.
The implications of these parasites are outlined below:
Coccidia: (Eimeria spp.) It is a condition often associated with stress in young stock, which can be increased by overstocking, severe weather conditions, poor nutrition and worms. Generally, unless very high numbers are observed they are not considered to have an economic influence.
Tapeworm: (Moniezia spp.) We report the presence of tapeworm eggs. The jury is still out on exactly the effects to animals of tapeworm. Young animals appear more susceptible. Folklore blames tapeworms for all manner of problems, but none of it is substantiated.
Liver Fluke: (Fasciola Hepatica) Animals grazing creeks and wet marshy areas favoured by the fluke snail (Lymnaea tomentosa – an indigenous freshwater snail) are likely to become infected. Liver Fluke Test Results are represented as either Positive or Negative. A positive result indicates the presence of adult Liver Fluke. If positive, management actions are most likely required.
