In the first edition of our new Ask Afrivet column, Dr Tod Collins discusses bovine leukosis in cattle. Every month, Food For Mzansi readers will have their animal health questions answered by a different Afrivet expert. Email questions to info@foodformzansi.co.za.
Thomas Ntlokwana from Pietermaritzburg writes: I don’t mean to gossip, but I heard about fellow dairy farmers really struggling with bovine leukosis in their cattle herds. Hau! To be honest, I don’t even really know what that means, but they’re talking about lesions and lots of abdominal pain. How do I know if I have bovine leukosis in my dairy herd and what can I do to treat or prevent it?
Dr Tod Collins, widely known as the Village Vet consultant, replies:
Thomas, now where did you hear this? In the pub, probably! However, if your consulting vet told you of the disease and its ramifications, that is good.
He probably referred to it as EBL (“enzootic bovine leukosis”) or maybe even BLV (“bovine leukaemia virus”). It is a puzzling, enigmatic viral disease that can take on different guises in different herds.
Sometimes a farmer notices some cows just getting lazy and a bit thin and despite what he and even the vet treats them with, they end up dying. When the vet opens them up, he often finds these large white “cancers” that can be involved with any organ in the body.
I’ve found them on the uterus, liver, abomasum, and heart! Often when the growths are on a vital organ the cow doesn’t even show prior symptoms; she drops dead! So, that’s the most obvious form of EBL.
Then there’s a form of EBL which we as humans associate with our blood leukaemia. This is a difficult form to confirm, but I reckon it can be likened to human’s HIV or immunodeficiency where the animals are susceptible to other conditions. Here, we often see an upswing in mastitis or lung conditions. It can really only be confirmed by laboratory tests.
The third form of EBL is the type that if your herd has to have it, is the best! This is because you’ll probably never even know that they are infected. This form has no symptoms and no deaths! It is only diagnosed after the vet or a researcher takes blood from every cow in your herd and yells down the phone at you, “Heck man! Your herd is full of EBL!”
That’s why we vets cry into our glasses of wine and shake our heads and say, “Heck, we deal with an inexact science!”
Impact of colostrum
Now, you are probably going to ask: “Is it really as widespread as my mates in the other pub say?”
Well yes, it is. In about 1990, a research veterinarian at Allerton State Veterinary Laboratory in Pietermaritzburg conducted a very thorough investigation of the prevalence of EBL in dairy herds in KZN. He found that over 75% of herds WERE infected; and many fell into Category 3.
However, what was even more staggering is that he found that in the infected herds, between 30% and 80% of cows were infected.
The gurus reckon it is mostly transmitted from infected cows to their calves via the colostrum; then those calves can grow up with one of those three forms. To prevent that, you have to separate calves from their mothers at birth before drinking colostrum. Instead, you must give them stored colostrum from cows that were tested free of EBL.
You might then wonder why farmers should even breed with these infected cows? It is a good point – if your herd numbers and infectivity can support it. In the USA, some states are trying to eradicate the disease this way.
They bleed, bleed and bleed the herds all the time to sort out the infected individuals. Of course you might want to replace those cows culled from having EBL; then you must insist that you only buy heifers or cows certified as being free of EBL.
However, we aren’t out of the woods yet. Have another beer and let me tell you more.
Another recognised form of transmission of EBL is by fomites. That is artificial stuff like vets going from one cow to the next doing rectal examinations with the same glove, or using an ultrasonic scanner transporting the virus (by tiny unseen amounts of blood) between cows without rinsing the probe or using the same hypodermic needle to inject several cows.
My argument, when the champions at the bar counter say, “Yes! The bloody vets spread the disease. They must use a new glove for each cow or disinfect that TV thing they stick up the cows’ backsides!” is this: “Even if we as vets do all that, you must still use a new clean injection needle for each cow when you are inoculating the herd. When you have a couple hundred cows, boet, then it’s one heck of a job!”
Take all precautions
Then, my final statement that makes you, who asked that original question, cry into your beer is this: Try to cull all positive cows and don’t allow their calves to get a squirt of colostrum, insist on your vet using a new glove per cow or disinfect the ultrasound probe between cows or use a sterile new needle for every cow.
But, and this is important: Make sure you don’t have a single biting fly, stable fly or horse fly on your farm! Because if you have, I reckon all those other precautions will have been in vain. Those little buggers bite a cow with EBL, and then whilst they are not quite dik gevreet, they go on to a naïve cow and bite her too. In so doing, the little buggers transmit the virus.
Ask an old vet who has knees like a rough mountain goat and has spent all his working life with cattle, which infectious diseases have been the most exhausting to prevent, treat and understand.
He’ll rattle off mastitis, redwater, gall sickness, BVD, trichomoniasis… pause… and oh yes, lumpy skin disease which has developed from a mild non-entity to a very serious condition these days.
Then he’ll look at the sky, or at a spot far beyond the corner where the pub wall meets the ceiling, and in a tired voice utter, “But heck, this enzootic bovine leukosis thing… that’s got us all waxed! They’re doing their best to get a vaccine made, but Retro viruses are very hard to succeed with.”
Afrivet Business Management, the biggest truly South African animal health company, was established in 2000 by Dr Peter Oberem. Afrivet’s formation marks the results of a dedicated group of pioneers in the South African animal health industry’s continued efforts to serve the industry with distinction.
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