Wednesday, November 30, 2011

Are Southern Deer Genetically More EHD Resistant?

 
EHD Resistant Southern Deer????
I keep seeing things about 'buy my deer because they are EHD resistant southern deer'. Everyone can have an opinion on something but when it's controversial sometimes people get a little overzealous in their arguements. I'm a scientist, not a mad scientist, and not one in a lab with bubbling bottles. I was trained as a wildlife biologist and studied deer behavior for two masters degrees. That doesn't make me smarter than anyone else but that much education does make your mind look at things a little differently.
In a scientific study, all variables not being manipulated for research should be controlled. For example, if I had two groups of deer in my study to determine if protein supplements produced bigger antlers and one group was my 'control' that didn't recieve the supplement but they had a food plot with high protein beans and the group that received the supplement had bermuda grass, then it wouldn't be a good scientific study because the variables in the food plot would make the study inaccurate.
A lot of what you hear about deer health and what works is anecdotal evidence. Anecdotal evidence is not scientific in nature. An example would be if I put vanilla extract in my deer water when they had pneumonia and they all got well, then vanilla being the cure for pneumonia would be anecdotal evidence. They may just have gotten over it on their own.
'Facts' that you hear about EHD resistance in deer is often anecdotal. There is some evidence but not much that proves a southern deer may be inherently more EHD resistant than a northern deer because of years of breeding to only southern deer. I haven't found the study again yet but I had read one a couple of years ago and if I do find it again I'll post it. The study was on passive immunity for EHD and I think southern deer were used. The study took a group of fawns as newborns to bottle feed. Titer levels were checked and found there was some EHD resistance. That was from passive immunity from the mother either through the placenta or immunoglobins in the cholostrum.
The fawns were divided into two groups. One was left outside and the other was moved inside to an insect-free environment. At weaning the two groups were checked for titer levels for EHD resistance again. The outside group showed resistance but the inside group did not. The results of the study showed that resistance exists from passive immunity when born but the passive immunity does not relate to permanent immunity. The difference in the two groups of fawns is that the outside group had exposure to the virus but the inside group did not. EXPOSURE is necessary either through direct exposure to the virus in the environment or through vaccines. Otherwise, after the passive immunity wears off the animal will be unprotected.
If the animals were EHD resistant because they were from the south and it was in their genetics passed down, then the EHD would have been there after weaning for both groups. The arguement is that if you buy northern deer and move them to the south, they won't survive. I have about 300 pure northern genetics deer in Louisiana. Did I lose many when I moved them here? You bet. I got sick of going out and dragging dead deer to my burn pile. The southern resistance guys will say that mine died because they weren't EHD resistant or weren't used to our insects or other diseases. I agree in part, but.....when deer are handled, they are stressed. If they are darted they are stressed even more. A study in South America on red deer showed lack of immune response 30-40 days after tranquilization. Hauling deer in a trailer for 20+ hours adds to the stress level they already have. Then you dump them out in foreign surroundings often mixed with deer that start pecking order fights. They are put abruptly on new feed. It's no wonder so many die. And stress doesn't just last 2-4 weeks. Some studies indicate that stress related illnesses can occur up to a year later.
I believe that moving northern deer south will result in some deaths. Minimizing stress through proper handling will help a great deal. Bringing feed from their origin and gradually changing the ratio of new/old feed will be less stressful. Pen size changes can cause stress. I use Aureomycin in my feed for a month after the deer are moved. Anything to mitigate the changes and stress that results from it will increase survival rates.
As for EHD, I believe that northern deer can survive very well in the south. They must have some exposure to the virus. There will be deaths. But, I know of many pure southern deer that have died from EHD. Ask a biologist from any southern state when there is a bad epidemic of EHD. Native deer are dying in the woods.
If you move northern deer south, just prepare for higher death rates. Once they get past that first year they do much better. The offspring don't know the difference. The advantages of northern bloodlines are worth what we went through initially. If you don't want that heartache and stress, buy northern bloodlines from someone who has suffered through it and has the strongest survivors.
EHD and BT viruses are killers no matter where the deer are from when it hits hard.
Please respond with your comments. I know there will be a lot of you that feel differently but at least try and find some scientific evidence to back up your arguements.

EHD: Northern vs. Southern Deer Resistance

 
I had a conversation with a friend about northern vs. southern EHD resistance. I wanted to share some of my thoughts. From the research I've read, I don't believe northerns with exposure to EHD will have any more trouble than southerns if their previous exposure history is the same. I hear it all the time that northerns aren't EHD resistant but I think that the people that have southerns are the ones promoting that view. If you bring northerns down south they likely won't have the resistance of deer born and raised in the south. I know someone in southern Louisiana who has said for years that it was a mistake to have northerns in the south. I haven't heard him say much since he lost a bunch of his southerns a few years ago when I was losing northerns. Even with southerns, research shows that fawns lose their immunity after weaning if they don't have continued exposure to the virus. It takes time for northerns to build their immunity because of the cyclic nature of EHD. If you bring northerns down and there is no significant EHD present for a few years, when it hits hard I would expect northerns to have somewhat higher death losses. Likewise, though, if fawns lose their immunity without having contact with the virus wouldn't the southern ones have higher death losses later in life too? I personally believe we're going to see EHD worsen for southerns in the future. If someone puts up a mister system around their pens, they eliminate the chance for building immunity to the virus. Animals MUST be exposed and get the virus to have immunity. One thing that you may be seeing in your southerns with flu-like symptoms, rather than more severe symptoms with northerns, is their history. Research shows if a deer gets EHD-1 it will have SOME cross protection but NOT immunity to EHD-2. Once the animal has the virus it should have lifetime immunity for that particular serotype. That's why live virus vaccines are only given once without the need for annual boosters as compared to killed virus vaccines. The problems facing us with EHDV and BTV is similar to humans and the flu. Mutations each year present the animals with slightly different viruses. The permanent immunity to one serotype doesn't prevent infection from a different one. Give northerns in the south some time to build their immunity and lets hope mister systems don't cause our southerns to lose their resistance. Something else I hear people promote is buying semen from their EHD resistant southern bucks. I have seen NO evidence of EHD protection passed down from the sire. Think about it just from a common sense perspective. Why do we vaccinate for BRSV, BVD, IBR, PI3, C&D, etc. if there is passdown immunity from the mother. We should be able to vaccinate a doe and all of her offspring would have immunity without ever needing to be vaccinated. Immunity doesn't work that way!!! Feel free to comment.