|Photo: Ovine Johne's disease affected sheep|
Ovine Johne's (pronounced 'yoh-nees') disease is an infectious fatal wasting disease of sheep. It is often abbreviated to OJD. OJD can have severe economic effects in sheep flocks if it is left uncontrolled. It is caused by a strain of the bacterium Mycobacterium paratuberculosis.
OJD - What's new?
Message from the Chief Veterinary Officer
OJD distribution and vaccination
The natural ecology of Mycobacterium paratuberculosis (M ptb), the causative bacterium of ovine Johne’s disease (OJD) in sheep, involves a faecal-oral route of transmission and requires a period of survival of the bacterium in the environment for spread to occur between sheep.
A combination of environmental factors including temperature, rainfall, humidity, stocking density, soil pH and quality, impact on environmental survivability of M ptb and hence the distribution and impact of OJD. Higher temperature, lower rainfall, lower stocking density and higher soil pH all tend to be unfavourable to environmental survivability of M ptb and/or transmission of infection to susceptible sheep.
DEPI’s Disease Epidemiology Surveillance and Control (DESC) group has produced a highly informative analysis on the incidence of OJD in Victoria over the past 5 years.
The analysis shows that for much of our state environmental conditions are highly conducive to environmental survival of M ptb and ready transmission of infection to susceptible sheep can occur. Fortunately there is an effective vaccine available which protects exposed sheep against developing OJD and which significantly reduces environmental contamination with M ptb.
Conversely, there is an area in the north west of Victoria where the incidence of OJD is very low, and any infection brought in with diseased sheep can be expected to be self-limiting and ultimately of low long term impact on health and productivity in the flock. This reflects our long experience of ongoing negligible impact of OJD in the north west corner of the state despite countless movements of infected sheep into the area over decades.
What does this mean for Victorian Sheep Producers?
Sensible broad scale management of OJD needs to recognise the concept of geographical OJD susceptibility rather than being too preoccupied with ‘area prevalence’ or ‘protected areas’ that are supposedly shielded by government regulated restrictions on sheep movement, but in reality are protected by environmental conditions.
High Susceptibility Area
On much of Victoria’s grazing land sheep are highly susceptible to OJD as a result of environmental conditions that are conducive to environmental survival and transmission of the causative bacterium. In this area (the high susceptibility area) producers need to take measures to mitigate risk of disease.
Within this area sheep producers should consider vaccinating all replacement lambs against OJD, and should consider only introducing sheep into their flocks that are approved vaccinates (e.g. as attested by a Sheep Health Statement provided by the vendor).
Low Susceptibility Area
In the north west corner of Victoria (the low susceptibility area) environmental conditions are unfavourable to survivability of M ptb; should OJD infection be brought in with introduced sheep, infection in the flock can be expected to be self-limiting and of low long term impact on health and productivity of the flock irrespective of intervention measures.
In my opinion, OJD vaccination would not generally be considered necessary or cost-effective for sheep that will remain continuously within the low susceptibility area. Individual producers should consider vaccinating sheep that they may wish to move or trade into the high susceptibility area or if required for other markets (e.g. if required for interstate movement or market assurance programs).
Producers, of course, should form their own opinion based on their own circumstances and veterinary advice.
Chief Veterinary Officer
What is the National OJD Management Plan (2013-2018)?
What is the National Sheep Health Statement?
The National Sheep Health Statement (SHS) is a formal document that accompanies non-slaughter sheep when they are sold. It does not replace a national vendor declaration (NVD) but should be used in conjunction with a NVD. The SHS indicates the health status of the sheep being sold and is signed by the vendor. It contains sections relating to the OJD, footrot, lice and ovine brucellosis history of the flock. It is an offence to make a false declaration on this statement.
It is not mandatory to complete a SHS when selling sheep within Victoria. However, it is strongly recommended that you request a SHS from the vendor prior to purchasing sheep. It may also be mandatory to complete a SHS prior to moving sheep interstate.
To download a copy of the SHS, please click on the link below:
- AG1126 - What is Ovine Johne’s Disease?
- AG1133 - Vaccinating Sheep Against Ovine Johne’s Disease
- AG1301 - Identification of Sheep and Goats in Victoria
- AG1128 - Legal Requirements for Ovine Johne's Disease
How to obtain Gudair Vaccine
Gudair vaccine is available from approved veterinarians and rural merchandisers from approved retailers. This is a list of authorised Gudair vaccine retailers within Victoria (as of August 2010).
- Animal Health Australia
- NSW Department of Primary Industries
- International Association for Paratuberculosis
- Johne's Information Centre - University of Wisconsin
- Meat and Livestock Australia