TOXO - navigating a breeding season without Toxovax
Unfortunately Toxovax is not going to be available to anyone for this breeding season going forward. There is no other licensed vaccine available worldwide for Toxoplasmosis in sheep.
Whilst this is a major blow to the sheep industry, here's a reminder of how the disease spreads, the risks of infection, and the some possible control points that should be considered.
Where does Toxo infection come from?
The risk of toxoplasmosis in your flock comes from cats and vermin. Vermin such as rodents or wild birds can carry cysts of the Toxoplasma organism in their tissues. Cats eat the rodent containing the parasite. The parasite then replicates in the cats body tissues and oocysts (“eggs”) are shed in huge numbers (millions) in the cat faeces with little clinical symptoms. Any contamination of the farm environment, which may include stored feed, forage, water etc., then poses a risk to the sheep that eat contaminated feed. The oocysts are very resistant in the environment and can persist for years.
What happens when a sheep is infected with Toxo?
Infection in early pregnancy leads to foetal death and reabsorption which will render the ewe “barren”. Infection in mid pregnancy can result in foetal death or survival but with the lamb being brain damaged and very weak. This is often the case where one lamb of a set of twins is born alive and the other dead. Infection in the last third of gestation can result in birth of a normal lamb because its immune system is developed enough to fight off the effects of infection.
If I have had confirmed Toxo, will she abort again?
Most sheep will only abort once with Toxo and then develop natural immunity. The natural immunity of the sheep is not reliable enough for flock control however, so Toxoplasma vaccine is used mostly for incoming sheep and replacements before breeding to protect against any future lamb losses.
Can we treat for Toxo once the sheep is infected?
There is no treatment for Toxo in sheep once they are infected.
What control measures can we do this year if we don't have Toxo vaccine?
Most cats will only shed oocysts once and for a short time. Unstable cat populations where a lot of strays are involved or there are cats breeding regularly on the farm leading to a lot of young cats being born pose the greatest risk to sheep flocks. It can be helpful to neuter males to reduce cat breeding on farm. Another important step in control is protecting sheep feedstuffs and bedding from cats by the use of vermin proof bins and sealed bales for examples.
There is no supply issue with Enzovax - enzootic abortion vaccine, another important vaccine to prevent against lamb losses.
WEANING: a seamless transition for your calves?
Weaning can be a risky time for calves as they transition over from a liquid milk diet to solid feed. Weaning should not be an event, but a process that takes weeks to prepare for.
The only thing that should change at weaning is the final reduction in milk volume over that last week; no vaccinations, no disbudding, no mixing groups, no moving sheds, no change to the concentrate, fibre or protein source. Just a gradual decline in milk and a gradual increase in concentrate feeding.
If the rumen has been well prepared before weaning, it just continues to process and digest the increasing amount of solid feed so there is no dip in available nutrients to the calf.
Weaning should only ever take place when the SMALLEST in the group is eating 2kg concentrate a day for 5 days in a row. Delaying weaning for smaller individuals will protect them from disease risk around weaning.
We will be running weaning audits over the next month - this time of year can sometimes highlight weak spots in weaning protocols that show up as poor health in the week or two after weaning.
Johne's Update: "Priority Culls" on NMR and CIS
The way high risk Johne's cows are being classified is changing with a new "priority cull" category for milk recorded herds from 1st October.
A "priority cull" highlights the most urgent cows to cull out of those infected with the Johne’s-causing bacteria Mycobacterium avium subspecies paratuberculosis – commonly known as MAP.
Previously we have classified infected cows with repeated test results above 30 as ‘red’ or high risk cows. But there can be a huge difference in infection risk between a cow with a result just over 30 for the first time, compared with a cow with consecutive results over 100 - these repeated, very high result cows are a lot further on in the disease and can be shedding enormous amounts of bacteria into the environment.
These priority cull cows present more of a risk of transmission and the infection will have a much greater impact on their performance. The priority cull report will list cows with two consecutive results above 60 and/or one result above 100.
These cows are ‘losing control’ of the disease and are likely to be shedding large amounts of MAP. They are the highest risk animals in the herd and the ones that should be prioritised for culling.
We will be updating your on farm Johne's reports to include "priority culls" as standard.
TSDG Herds & Priority Culls:
A reminder of the Johne's rules:
- Tesco "red cows" are 2 consecutive high results >30%
- You need to make sure you have no more than 2% red cows in the herd
- if you go over 2% "tesco red cows" you will need to either cull before the next recording window, or "retain and test" the positives with a faecal PCR test with all results being uploaded onto the Authenticate site.
- If the PCR result is negative she can stay, if the PCR test is positive she must be culled.
ARLA 360 / C.A.R.E HERDS & Priority Culls:
A reminder of the Johne's rules:
- from Jan 2023 less than 5% of the herd can be "red cows" - the red cows here are defined as having results over 30% in the last 2 in 4 recordings
- from Jan 2023 no PRIORITY CULL COWS can contribute to the saleable milk. This means any cow that's ever been >100% positivity must not contribute to the bulk tank.