Summertime for sheep farmers is a busy time of the year, with silage to be made, sheep to be shorn, lambs to be sold, and ewes to breed. But nothing is more important than protecting the flock from disease.
There are numerous disease in sheep more specific to summertime, one of which is Johnes disease.
Johnes disease is a contagious, chronic and mostly fatal disease in sheep, cattle and goats.
It affects mainly the intestines of ruminant animals, causing their intestines to swell up, and thus meaning they are less productive and less efficient at absorbing nutrients.
This means that although the sheep may be eating the same amount as normal, but still losing weight.
Johnes disease is caused by a resistant type of bacteria which comes from the same family as TB and leprosy. It is caused by Mycobacterium avium subspecies paratuberculosis (MAP) and there are several strains.
The sheep strain of the bacteria is very difficult to culture, and an optimal method for detection has yet to be found for the strain.
Up to 70% of sheep may never show any signs of the disease but shed the bacteria in their feces, causing the disease to spread through the flock.
Similiar to the human disease, Chrons, it can cause decreased milk production in an animal, and dcrease carcass yields also.
Flocks with a high rate of infection could mean the loss of up to 10% of animals in the flock.
The disease also often shows similiar sympthoms to diseases such as dental diseases, pneumonia, crapie, parasitism, chronic infections of the organs, and caseous lymphadentis abscesses.
It should be noted that if you have a good deworming and dosing programme in place that maybe Johnes disease is the cause of sheeps health problems.
Lambs are more susceptible to the disease than adult sheep, although this age resisitance is usually overpowered by higher doses of the disease in the flock and prolonged exposure to infected animals.
The bacteria are resistant to heat, desiccation, freezing, disinfectants and UV light and is known to survive in water and urea on pastures for as long as 11 months.
There are many stages of infection, usually stage one of the disease in undetectable and as previously mentioned there are very few physical signs. Stage two: again there are no sign, though traces can be found in the animals faeces. Only the weaker younger sheep show any signs during this stage.
Stage three: this is the time when sheep continue to eat extremely well but are losing weight, if this is observed an immediate blood test is advised as the disease can now be detected. Stage four is the stage where a sheep is weak, shedding high numbers of the bacteria, and in overall bad condition. Usually once an animal has reached this stage of the disease they tend to die.
To help determine if an animal is infected there are various tests, including a faecal test of tissue culture test. Though the effectiveness of tissue culture tests are not yet great. A blood test, as previously mentioned, can also be undertaken, though this can only usually detect the disease in its third stage.
It is advised to test all of the flock once any sign of the disease is detected in any animal, to help prevent its spreading. Your flock should be regularly checked and tested to ensure you catch the disease at its earliest.
Usually, it is advised to immediately cull any sheep found with the disease, such is the rapid spreading nature of the bacteria. It's better to lose one animal than a whole flock. Never put sheep back on a pasture where the disease was present the year before, don't forget the bacteria can survive for up to 11 months in water and pastures.
Overall there's not much a farmer can do, bar being extra vigilant. The only way to prevent the rapid spreading of this disease is constant care, and observation of your animals. The saying goes "better be safe than sorry" and is a perfectly suited motto to combatting Johnes disease in sheep.
Be safe, be vigilant, care for your animals, dose regularly, resist using previously infected pastures OR you will be sorry.