Bovine Respiratory Syndrome and Infectious Bovine Rhinotracheitis - What are they?
Let us begin with Bovine Viral Diarrhea (BVD) which is sort of misnamed because it is considered the #1 respiratory virus of cattle. Of course, it causes all that other stuff as well. This Pestivirus Flaviviridae RNA virus comes in numerous forms and mutated varieties, some are cytopathic (cell killing) and some are non-cytopathic. They are all seriously dangerous, they just destroy in different ways. There is also a Type 1 BVD, the type that is predominate world‑wide and a Type 2 which makes up 50% of the US cases. There are also now at least 17 known viral mutant variants as well. But, for now anyway, you don't really need to know all the names of these variants, just know that no one vaccine will protect your herd from them all. And, like many viruses, this microbe is mutating constantly. Collectively, these forms add up to being the worst bovine respiratory virus in the world and it accounts for huge financial loss. The virus also causes Border Disease i n sheep and Viral Swine Fever. Note that there are currently at least 160 different BVD vaccines for cattle available right now!
BVDV, like the HIV virus for example, is a serious immuno-suppressive; meaning it opens the door for other viruses and bacteria to wreak havoc on all parts of the body. These are called secondary infections. Various viral forms and other contributing conditions usually result in a wrecked digestive system; diarrhea, pneumonia, hemophilia (bleeders), eye and nose discharges (can look exactly like bacterial pinkeye) and high fevers. There are also tremendous numbers of reproductive disease symptoms and loss due to the virus, primarily through abortion or stillborns, but there is also a loss in fertility and conception.
Particularly problematic is that BVDV can spread vertically (to offspring) or laterally (herd mates), it can also retrograde up from a calf to the mother. The worst‑case scenario comes from a pregnant female that is either given a live vaccine during gestation or that gets the wild disease while pregnant. Her calf (if it survives) can become what is known as a Persistent Infection (PI) Carrier and even though these animals are usually somewhat asymptomatic, they can spread trillions of virions throughout their entire life (luckily, they rarely live beyond two years of age). Basically, PI calves only occur if the fetal calf is immunologically or physically weak. Vaccine options include: the safer but less effective killed version, the modified-live version or other attenuated viruses. Most BVD vaccines come with (anywhere from) 1-5 other virus antigens in the same syringe. Multi-valent examples include Bovi-Shield Gold or Preg-Gard.
Which leads us to the #2 problem, Infectious Bovine Rhinotracheitis Virus. IBR, aka "Red Nose." This double‑strand DNA virus is called Bovine Herpes Virus‑1 (BHV‑1) and acts very much like herpes in humans. It lives, usually forever, within the nerves and brain of the patient and tends to emerge whenever there is stress, deficiency, toxicity or other unfortunate set of circumstances. In humans it is the chicken pox herpes virus that can emerge as Shingles later in life. BHV‑1 is by far the #1 cause of viral abortion in the US. It also hits the bovine body everywhere destroying lung and respiratory epithelium, creating eye infections (also looks like pinkeye), genital infections, brain infections, the aforementioned abortion, and a typically lethal and virtually untreatable "generalized infection " state in newborns. Just the reproductive diseases alone from this virus cost ranchers over $500M a year in losses. There are numerous vaccine options here too, from killed versions to MLV concoctions. The live virus vaccines will definitely reproduce in the host once injected. There are strict guidelines as to when and how to vaccinate, for example a pregnant and previously unvaccinated heifer or cow will abort if vaccinated during gestation. Likewise, a vaccinated calf nursing on an unvaccinated cow can transfer the disease to the mother. Scientific studies by the maker of the most common and most desirable vaccines show that the vaccines themselves are also seriously damaging to reproductive fertility. They show that vaccinated heifers have a conception rate below 40% and there is always a 5‑25% increase in abortion losses. The vaccines present such a drain on immunity that many vaccines contain bacterial proteins to help develop more resistance to secondary invaders such as: Leptospirosis, C ampylobacter, Mannheimia hist., Pasteurella Multocida and others.
Next time we will consider some more dangerous diseases/infections that afflict a lot of cattle herds across the country.