Effective Internal Parasite Control in Sheep

Internal parasite infestation is a major cause of production losses in sheep in Australia. Castro-intestinal roundworms, lungworm and liver fluke are all considered to be economically important parasites to control.
Despite considerable research being conducted into developing integrated parasite control programs (e.g. grazing management strategies to minimise worm burdens and breeding parasite resistant sheep) to minimise the use of anthelmintic's (drenches), farmers continue to rely heavily on anthelmintic's for effective internal parasite control in sheep.
Coopers Animal Health (a division of Schering-Plough Pty Limited) has established themselves as a reputable company with emphasis on product quality and customer service over many years. Accordingly, Coopers has developed a diverse range of quality products for the control of internal parasites in sheep.
This information below aims to help you identify the Coopers product which is most suitable for your needs.

Broad Spectrum Anthelmintic's

Broad spectrum drenches kill a wide range of susceptible internal parasites of sheep. They are:
Benzimidazole "white" Drenches
Benzimidazole's work by inhibiting the parasite's ability to absorb nutrients, which ultimately leads to the starvation of the parasite. Benzimidazoles are effective against gastrointestinal roundworms, lungworm and tapeworm. Albendazole when used at a higher rate will aid in the control of adult liver fluke.

Valbazen® (Albendazole)

• Control of susceptible gastrointestinal roundworms, lungworm's, tapeworms and to aid in the control of adult liver fluke.

Levamisole "clear" Drenches
Levamisole based products will affect the transmission of nerve impulses in the worm resulting in paralysis and expulsion of the parasite. Levamisole based products are effective against gastrointestinal roundworms and lungworm.
Coopers have combined Oxyclozanide with Levamisole in the product Nilzan LV to also provide control of adult liver fluke and to assist the removal of tapeworm segments in sheen and lambs.

Nilverm® Oral and Nilverm LV

• Control of susceptible gastrointestinal roundworms and lungworm's in sheep and cattle.

Nilzan® LV (also contains Oxyclozanide)

• Control of susceptible gastrointestinal roundworms, lungworm's and liver fluke in sheep and cattle. Assists in the removal of tapeworm segments in sheep and lambs.

Ripercol® Soluble Powder

• Control of susceptible gastrointestinal roundworms and lungworm's in sheep.
  

Macrocyclic Lactone (endectocides)
Macrocyclic Lactone (ML) products control a range of internal (gastrointestinal roundworms, lungworm) and external (itchmite, nasal bot) parasites in sheep when administered orally. Macrocyclic Lactones inhibit the transmission of nerve impulses in the worm leading to paralysis and expulsion. Macrocyclic Lactones are effective against adult and immature gastrointestinal roundworms and lungworm. The Macrocyclic Lactones have no activity against liver fluke or tapeworm.

PARAMAX® Multi-Purpose Concentrate for Sheep (lvermectin)

• Oral treatment for control of susceptible gastrointestinal roundworms, lungworm's, nasal bots and itchmite in sheep*.

*Can also be used for prevention and treatment of blowfly strike and treatment of lice by jetting in long woolled sheep (See product label).

Combinations (Benzimidazole/Levamisole)
In an attempt to manage anthelmintic resistance, combination drenches (mixtures of Benzimidazole and Levamisole based products) have become an important tool on many sheep properties. Where resistance to either of the Benzimidazole or Levamisole based compounds is present, the use of a combination drench is usually more effective.

Scanda® Mineralised (Levamisole, Oxfendazole, Selenium, Cobalt and Zinc)

• Control of gastrointestinal roundworms, lungworm's and tapeworms in sheep and lambs, including Macrocyclic Lactone, Levamisole or Benzimidazole resistant strains susceptible to this product. Supplements diets deficient in Selenium, Cobalt and Zinc.
  

Narrow Spectrum Anthelmintics
Narrow spectrum drenches are only effective against one or two parasite species. They include:
Triclabendazole
Triclabendazole is a Benzimidazole compound that when administered on its own is effective against all three stages of liver fluke, including early immature, immature and adult liver fluke. Coopers have developed PARAMAX F, a Macrocyclic Lactone/Triclabendazole Combination, which is effective in the control of gastrointestinal roundworms, lungworm plus liver fluke.

PARAMAX F (Triclabendazole; also contains Ivermectin)

• Control of susceptible early immature, immature and adult liver fluke in sheep. Control of susceptible gastrointestinal roundworms, lungworms, nasal bots and itchmite in sheep.
  

Closantel
Closantel based products when administered on their own (e.g. Seponver® Se) have a narrow spectrum of activity against blood sucking parasites (Barber's Pole Worm and liver fluke). Closantel based products provide sustained activity for up to 4 weeks against susceptible strains of Barber's Pole Worm and controls adult and immature liver fluke 6 weeks of age and older Closantel also controls nasal bot.
Because of its high level of effectiveness and its sustained activity, Closantel has formed the basis of strategic drenching programs in areas of Australia where Barber's Pole Worm (Haemonchus contortus) has been a problem, greatly reducing the losses due to this parasite.
Closal is a combination of Closantel with Albendazole that provides sustained activity against Barber's Pole Worm as well as controlling a broad spectrum of other internal parasites.

Seponver Se (Closantel plus Selenium )

• Sustained control of Barber's Pole Worm and control of liver fluke and nasal bots in sheep. Aids in the control of Selenium responsive conditions.

Closal® (Closantel plus Albendazole)

• Control of susceptible gastrointestinal roundworms, lungworms, tapeworms, nasal bots and liver fluke in sheep. Reduces output of viable worm and fluke eggs. Sustained control of Barber's Pole Worm in sheep.
  

Naphthalophos (An Organophosphate Compound)
Naphthalophos is the active ingredient in Rametin and is commonly used in situations where resistance exists to other drench groups. Rametin is sometimes referred to as a 'mid-spectrum' drench as it is registered for control of Barber's Pole Worm, Stomach Hair Worm, Black Scour Worm, Small Brown Stomach Worm and adult stages of Thin Necked Intestinal Worm in sheep and lambs. Rametin is often mixed under veterinary supervision with other drenches to give broad spectrum activity.

* Increase dose rate to I mL/4 kg LW to aid in the control of adult liver fluke
¹Coopers Selenium Drench Concentrate for Sheep, Cattle and Poultry is registered to be added to PARAMAX Multi-Purpose Concentrate for Sheep and Nilverm Oral. The concentrate may also be added to other sheep drenches under veterinary instruction
²Other levamisole based products for sheep have an ESI set at 7 days
³ESI is under review and final ESI may be longer

Drench Resistance

Drench resistance is when a strain of parasite survives a dose of drench at the recommended dose rate. Drench resistance parasite strains are present when a chemical used at the recommended dose rate achieves < 95% reduction in worm faecal egg counts.
Drench resistance is becoming a major problem in many areas of Australia as outlined in the following.

Benzimidazole "white", Levamisole "clear" and Combination Benzimidazole/ Levamisole
Resistance to Benzimidazole "white" and Levamisole "clear" drenches is widespread and resistance to combination Benzimidazole/Levamisole drenches is increasing. However, Levamisole based drenches still remain relatively effective against Barber's Pole Worm in many Summer Rainfall areas of Australia where Barber's Pole Worm is a significant problem.
Macrocyclic Lactone
Despite Macrocyclic Lactone based products being the last of three broad spectrum anthelmintic groups to be introduced to the market, their use has been extensive and frequent since their introduction. Resistance to Macrocyclic Lactone based products is common in Western Australia for the control of Small Brown Stomach Worm (Teladorsagia circumcincta) and is emerging on many properties in the Eastern States of Australia.
Closantel
Resistance in Barber's Pole Worm to Closantel is present on many properties in Northern NSW and South East Queensland. Producers are urged to check the efficacy of Closantel against Barber's Pole Worm where this parasite is a problem. A Closantel resistance assay is now available to determine the effectiveness of Closantel drenches. Consult your local veterinary advisor for further information.
Triclabendazole
Small numbers of Triclabendazole resistant strains of liver fluke are present in Australia. The majority of cases identified are confined to the Goulburn Valley region in Victoria.

Recommendations for Effective Internal Parasite Control
There are a number of guidelines, which can be adopted in order to help delay the emergence of anthelmintic resistance on your property.
Determine the Need to Drench

• In deciding whether to drench it is important to assess whether the drench is required. Conducting
  a worm faecal egg count test can help determine this.
• Anthelmintics should be used as part of an overall strategic parasite control program. Programs have been developed for most sheep growing areas of Australia. Consult your local veterinary advisor for further information.

Choose an Effective Drench

• It is recommended that properties conduct a drench resistance test every 2-3 years to determine the effectiveness of drenches from each of the chemical groups. Faecal egg count reduction tests (FECRT) and the laboratory based DrenchRite test are now being used widely.
• Effective drenches should kill 95% or more of the adult and developing worms in the sheep.

Administer the Correct Dose

• Shake the container to mix contents
• Double check the dose rate and regularly check, calibrate and service your drench guns.
• Check sheep weights and drench to the heaviest animal in the mob.
• Always follow the label.

Follow Correct Drenching Technique

• Ensure drench gun is correctly inserted. Place the tip of the drench gun over the base of the tongue and expel dose.
• Allow time for the dose to be swallowed before moving on to the next sheep.

Ensure Correct Pre-drenching and Post-drenching Management
For Benzimidazole and Macrocyclic Lactone drenches:

• Maximum effect will be obtained if animals are held off feed for up to 24 hours pre-drenching and at least 6 hours post-drenching. This helps to prolong the period in which the drench remains in the gut.
• Do not restrict feed or water in heavily pregnant, stressed or poor sheep.

For Levamisole or Organophosphate drenches:

• Do not hold animals off feed or water overnight.
• Ensure animals are returned back onto feed and water immediately after drenching.
• Do not treat severely debilitated or stressed animals.

Drench Rotation

• It is important to continue to rotate between effective and different drench groups as part of a strategic and effective internal parasite control program.
• However, it has become evident that drench rotation alone will not prevent the development of anthelmintic resistance occurring. For further information consult your local veterinary advisor.

Mixing Drenches

• On some properties it may be necessary to use more than one drench group family This may require mixing of drenches to achieve effective control of roundworms. This practice should only be conducted under veterinary direction due to concerns of compatibility, safety and efficacy. This includes the use of Rametin (Naphthalophos) with a broad spectrum drench.

Quarantine Drenching

It is important to prevent introducing resistant worms to your property when buying in new sheep. There is now a real risk of importing Macrocyclic Lactone resistant worms to your property in many areas in this way. For effective quarantine drenching always:

• Treat sheep at loading or on arrival.
• Use a combination of products including a Macrocyclic Lactone product-and at least two other anthelmintic groups (e.g. PARAMAX Multi-Purpose Concentrate for Sheep and Scanda Mineralised).
• Retain drenched sheep in the yards (with access to water) for 24-48 hours after drenching to allow the sheep to empty out.
• Move sheep to a quarantine paddock. It is recommended that the quarantine paddock be one that is either going to be cropped in the coming year or a pasture paddock that is moderately contaminated with worm larvae to dilute with any introduced resistant worms.
• Monitor worm faecal egg counts 10- 12 days after treatment to ensure that resistant worms have not been
  introduced to the property.