Visitors since August 2003:
 
 

 
 
Worm Resistance
  Worm resistance is the ability of parasitic worms causing scour and ill-thrift to survive treatment with anthelmintics. Most sheep farmers rely heavily on the use of anthelmintics to control diseasses associated with these worms due to relatively high stocking rates.
 

Traditionally white drenches (benzamidazoles) have been a problem specifically with resistance from strains of T.circumcincta, but now resistance to levamisole and ivermectin and even cases of triple worm resistance have begun to emerge ie worms that are resistant to all three major groups of anthelmintic.

Three major groups of anthelmintic:

Benzamidazoles (white drenches)

Ivermectins (Ivomec, Dectomax, Cydectin)

Levamisole (Exhelm)
  In the past advice has been to rotate use of the three groups annually, unfortunately this seems to have facilitated the emergence of multiple resistant worms. It seems that resistant worms have tended to be found on farms that have good control of parasitic disease.
  Once you have resistant worms on your premises , it is very difficult to get rid of them, if not impossible.
 

Our best advice to you to avoid the problem is the following:

Maintain a closed flock as far as possible*.

Double fence your boundary and avoid stray sheep.

Quarantine sheep that enter the flock (including purchased tups) and treat them with an appropriate dose of Moxidectin (Cydectin), only releasing them after it has had a chance to work (24hrs)
  * Also helps to control other diseases such as Scab, MV, CLA, etc.
 
 
VITAMIN E/ SELENIUM DEFICIENCY
  General principles of Trace Element Deficiency

There are 4 stages in the progression of trace element related problems:
Depletion loss of mineral from storage sites (eg liver)
Deficiency blood levels drop.
Dysfunction metabolism is affected.
Disease clinically detectable abnormalities (infertility etc)

Vitamin E and Selenium are closely related as Selenium is required for the production of vitamin E. Selenium is also required for Thyroid hormone production. They play a vital role in protecting the cells of the body from damage. Unlike copper there is little long term storage of Selenium in the body, therefore a constant supply is required.

There are some areas of the country where soil selenium is very low leading to low pasture levels. Vitamin E is high in green pasture but levels can drop during dry periods and when forage is stored long term. Therefore housed animals can be most at risk from deficiency.

Clinical Signs of Selenium / Vitamin E deficiency:

Ill thrift poor growth rates, poor resistance to worms and other disease.
White Muscle Disease at birth or delayed occurring at 1-3 months. Stiffness, discom fort, respiratory distress and sudden death.
Fertility associated with increased embryonic death at 3-4 weeks after tupping. In Bulls there is evidence of selenium deficiency causing infertility.
Impaired Immune Function particularly in young lambs.

Diagnosis of Selenium / Vitamin E deficiency (professional help often required)

Blood sample , liver sample, soil samples, clinical examination and evaluation of
fertility/ health records. Response to period of supplementation.

Treatment and prevention

Sodium selenate orally (included in anthelmintic drenches such as Panacur SC™). Other, more expensive general mineral drenches have Selenium in chelated form which is
theoretically more use to the animal (eg. Liquithrive™).
Itra-ruminal boluses such as Cosecure can provide longer term protection as can Deposel™ injection.
Shorter term injections such as Vitenium™ can also be used at target times such as late pregnancy. (Remember Selenium does not cross placental barrier in last month so inject before this time if you want it to get to the lambs).
Inclusion in feed - most commercial feeds contain Selenium but remember do not rely on this getting to the lamb in late pregnancy.
Free access minerals in buckets or licks can be convenient but some animals may not take them. Inclusion of minerals in the water supply could also be used where animals are housed.
Check Selenium levels in pasture / forage and treat with Sodium barium selenate
granules as necessary. This could help avoid the route problem.

BEWARE Inorganic Selenium (eg Sodium Selenate) can be toxic. No more than 0.3mg/kg in feed, 0.75mg as an injection in lambs or 3mg/kg body weight injection in ewes. Be careful when supplementing by more than one route.
 

LAMENESS

When to trim is probably the biggest 'new' issue with lameness in sheep.

Scald: Predominantly a disease of the skin between the toes, no under-running or extension into the horn of the foot.

Treatment: Do not trim, just treat with footbath or spray. The scald bug is present all the time and tends to flare up if the conditions are right. Often high proportion of group affected "over night". I use hibiscrub diluted 50:50 with surgical spirit in a hand sprayer - cheaper than spray cans and highly effective, although some commercial sprays are coming out now that spray better and last longer (Animedazon ® - Forte Healthcare). Dry standing time is important, the alcohol in preparations such as Terramycin® facilitar-tes quick drying. Surgical spirit is basically alcohol.

Foot Rot: Often starts as scald but quickly progresses to the horn and can cause extensive under-running. Highly contageous and should be treated as such.

Treatment: Do not trim, seperate affected animals. Foot bath both groups. Trim affected group after a few days and carry on bathing intermittently until treatment successful. Penicillin at 30mg/kg (high dose) followed by dry standing for 24 hours is very effective in more severe cases. I prefer straight penicillin (depocillin® Intervet) than pen-strep, it is easier to inject and you don't need the "strep" part.

Oxytetracycline (Terramycin®) also very effective as an injectable solution. Only bring groups back together once treatment successful. There is a very successful commercial vaccine available, Footvax®, initial course 1ml 4-6 weeks apart then a booster prior to high risk periods. Unsightly lumps are common and not always popular with pedigree breeders ! One breeder suggested injecting on the inside of the back leg, I suppose as long as it is sub-cutaneous there won't be a problem and at least it will be out of sight !

Remember footrot bug only survives in soil / grass for 4 days. So treat and move.

Standard bath: Formalin 40% formaldehyde diluted to 1:20 = overall 2% solution. Copper sulphate and Zinc sulphate are 1kg per 10 litres of water.

Contageous Ovine Digital Dermatitis: Predominantly affests the skin of the coronary band and is highly contagious. Often made worse by conventional foot bathing.

Treatment: Do not trim immediately, as with footrot. When you do bath, use Tylan® soluble (1g/Litre) or Lincomycin for 20 minutes. Dry standing after bathing particularly important here to allow treatment to dry on. Can use weedkiller type sprays in a small number of sheep. These products are also effective against scald and footrot but are quite expensive. Routine foot trimming - do not do it ie only trim badly overgrown feet or lame animals AFTER an initial course of treatment to avoid spread.