Scouring Lambs

Question 1

You arrive back from a holiday to be confronted by a colleague who has been trying to manage a scouring problem in young lambs in a large flock which doesn’t usually have much contact with the practice. It is a 5000 ewe flock that lambs in large sheds through April. In shed 4, almost every lamb gets scour at about 24 hours old. Some lambs very ill, others apparently recover with antibiotic treatment. · Not a high associated mortality but antibiotic treatment is intense. Your colleague starts to fill you in on the details. They tell you that when the farmer phoned them a week ago, he was giving all lambs given a double dose of spectinomycinas soon as possible after birth & then any lamb seen to scour was given a further oral treatment & a potentiated amoxycillin (SynuloxRTU) by injection* Shocked by this, your colleague visited the farm in the previous week. On 14th your colleague collected in a sample of scour & the results were back a couple of days ago - E coli was cultured & it was found to be resistant to spectinomycin. Then just yesterday (20th April) they had got hold of some Neomycin & put in place Neomycin prophylaxis for all lambs. You decide to visit the farm without further delay. What else might you consider by way of further investigation?

Answer 1

• Swab the environment
• Clinica lexam of the sheep and lambs
• Ask questions about history –where and when did it start, how old are the lambs when they are affected, what is their lambing strategy? Etc.
• Rainbow strip

Question 2

As you visit the farm & discuss the situation with the farmer, you decide to collect some samples of scour to test with Rainbow strips (lamb & kid) which are pensidelateral flow devices that will test for Rotavirus, E coli F5, Cryptosporidia, C perfringens & epsilon toxin.

Results are pictured.

1. What is the significance of positive for Epsilon toxin?

Answer 2

The epsilon toxin (Etx) is one of the 4 major toxins produced by C. perfringens -it affects cell membranes directly by increasing permeability and causing ion imbalances The epsilon toxin is considered to be the most toxic toxin produced by C. perfringens Etxproduced by C. perfringens types B and D is involved in animal (goats, sheep and less frequently cattle) enterotoxemias that can be rapidly fatal and economically devastating. Etxis the most potent of all C. perfringens toxins as determined by a 50% lethal dose

Question 3

What additional questions do you want to ask the farmer?

Answer 3

• What is your lambing strategy?
• Why did you double the dose of antibiotics?
• Are they on other medications?
• How old are the lambs, are they affectedpre or post weaning?
• Have you done any colostrum testing recently?
• Do most lambs manage to suckle okay?
• Do you have any lambing records or medication records?
• Have you had this happen before in previous years?

Question 4

A few years ago one of your sheep farmer clients had some goats which he kept in the field by the house that he now lambs in. A couple of the goats lost weight to the extent that they eventually wasted away despite adequate feed and worming treatments. The same client is now concerned that he is seeing an issue with thin ewes & he is needing to cull 3 year old ewes due to poor body condition. The ewes are not scouring.

1. What would be on your differential list for ill-thrift in ewes?

Answer 4

• Johnesdisease – faecal sample, ELISA, direct PCR, acid fast stain or antibody test in blood or milk
• Maedi Visna – blood test, to be negative you need 2 qualifying blood tests 6 months apart to be accredited
• Ovine pulmonary adenocarcinoma (Jaagsieket), it’s the retrovirus that is the causative agent of the lung cancer –PM histology is gold standard, so gotta kill it
• Dental problems –good oral cavity exam
• Scrapie –PCR on neuro tissue,histology
• Caseous lymphadenitis –bacteriology
• Nutritional deficiency –clinical signs and asking the farmer about feeding regime etc.
• Intestinal tumour –PM, ultrasound if they are keen
• Parasites due to poor pasture management and erroneous control strategies –faecal exam, check worming regime with farmer
• Virulent foot rot can also cause weight loss and wasting –good clinical exam of feet

Question 5

What is the important clinical sign that you often find in cattle with Johnes Disease but rarely see in sheep or goats with the disease?

Answer 5

• Economic losses from the disease can be measured in terms of reduced production as well as culled animals. Unlike cattle, in which the disease has been more extensively studied, chronic diarrhoea is not a consistent feature of Johne’s disease in sheep and goats; the predominant clinical sign in these smaller ruminants is weight loss over a period of weeks or months.
• Cattle–diarrhoea with wasting
• Sheep–wasting,lessdiarrhoea

Question 6

This client breeds his own replacement ewes. What are important control measures that he can use for Johnes disease?

Answer 6

• Don’t use new lambs as replacement stock –keep them separate and get them to slaughter as soon as thee are viable –get in new breeding stock, from a Johnesaccredited flock –keep these separate when they come in though.
• Keep sheep away from cows –cross infection can take place
• Most thin ewes are culled
• Live with the disease and limit the spread of infection by culling cases early in the disease process. Since transplacental infection is recognised. offspring of confirmed cases should not be retained for breeding.
• Test and cull. This has been shown to be a successful strategy in a goat herd where an aggressive programme of quLarter-lyblood testing and biannual faecal culture was instituted. In this case, several management practices were also instituted to present faeco-oral infection, including stopping grazing, installing automatic water drinkers and ensuring the frequent clearing and cleaning of pens. This could, however, be an expensive option.
• Vaccination. This has proved to be a useful method of controlling the disease in both sheep and goats and has been used in the UK to good effect (Cranwell 1993). On infected premises, young animals need to be vaccinated early in life (i.e. at less than one month old). If replacements are being purchased, they need to be vaccinated on arrival and kept in isolation for one month before being exposed to potential sources of infection. It should be understood that vaccination does not eliminate the infection from a flock or herd. Vaccinated animals are known to excrete the organism in their faeces, but are more likely to have a full productive life, being culled for other reasons before the onset of clinical Johne’s disease. It should also be noted that the vaccine causes a significant local reaction, particularly in goats. Vaccination produces an antibody response which is detectable serologically for some considerable time. This may have implications for the flock should exporting of stock be a possibility in the future.