Bovine Viral Diarrhea (BVD) - also know as Bovine Viral Diarrhea Virus (BVDV) 

(posted on the NJAC Website 12/20/05)

Previously BVD was not considered a problem in alpacas. It came to my attention however when "Miss P", a cria which we purchased at a spring auction with her mom, was diagnosed as a PI cria. What is BVD? What is a Persistently Infected cria (PI)? Why should you be concerned about BVD?

BVD is a virus that is passed to alpacas through bodily fluids of an infected animal. Most times it is not a problem - alpacas become infected, mount a response with antibodies and clear the virus. Females who are exposed to the virus for the first time during pregnancy are a different story. Several problems can become an issue. For instance when a female is exposed to the virus for the first time in the early part of gestation, the fetus that she is carrying will never be able to mount antibodies to the virus and will always have the virus. After it is born it will continually shed the virus and spread it to other animals throughout its life. This cria is a Persistently Infected (PI) cria and must be culled to stop the spread of the virus.

"Miss P" was possibly the first PI cria Cornell University diagnosed. Fortunately we had quarantined our new purchase from the auction and when we tested our herd we never had a positive result for the active virus on our property. However, there were 4 females and one young male who tested positive for antibodies to BVD - which means they were probably exposed to the virus before they came to our farm. To prevent the spread of BVD precautions will be taken with the pregnant females who tested positive for BVD antibodies. They will be quarantined for birthing and kept quarantined until the cria is tested for BVD.

We were very fortunate that the virus did not spread. There are others in New Jersey and the Northeast who have not been as fortunate. To those that say NJ is just a 'hot spot' for BVD, I beg to differ. How many farms in other states have done testing? If so, have the farms been willing to share the info with other farms? The cria we purchased was from the west coast. Other animals we own who tested positive for antibodies came from New England and New Jersey.

One of the biggest problems I see with BVD is the breeder who ignores it or simply doesn't admit there is a problem. Once you know the status of your herd, it is a matter of herd management to eliminate BVD. The breeder who sold us "Miss P" continues to state that they have no problem and that "Miss P" obviously contracted BVD when she came to NJ. Remember, we purchased her as a cria at side and Dr. Dubovi classified her as a PI cria, which means her mother was exposed to the virus while "Miss P" was in utero. (i.e. while the dam was still on the west coast)

I do not expect that every farm who tests will show signs of BVD exposure. To the contrary, it probably is a small percentage. But unless you have a closed herd, never go to shows, never purchase new animals and never do outside breedings, exposure to the BVD infection can become an issue on your farm.

When NJAC members had a discussion on BVD last fall, it was a unanimous decision to help educate our members, other breeders and vets about BVD by sponsoring a seminar. On February 19, 2006 Dr. Ed Dubovi, one of the top veterinary virologists in the country, will discuss Bovine Viral Diarrhea in alpacas. Dr. Katrina Alger will talk about Quarantine Issues and Current Immunization Protocols. Even if you are planning to attend this seminar, we suggest that you familiarize yourself with BVD beforehand. The various links and reference articles listed below will help you to understand the basics of BVD.

Please pass this information on to fellow breeders and your vet. BVD is too important an issue to disregard. Ignoring it will not make it go away.


Frieda Goodrich

 

References About Bovine Viral Diarrhea (BVD)     (posted on the NJAC Website 1/4/06)

Links

1. ARF website

2. Articles in both the December 05 MaPaca Newsletter (posted on the web www.mapaca.org)


Reference articles in

1. Camelid Quarterly:

a. June 2005: "BVD Virus" pg. 93
b. September 2005: "BVD in Camelids - A Practical Approach"

2. Alpacas Magazine:

a. Summer 2005 "Bovine Viral Diarrhea Virus" pg 144 and 146
b. Winter 2006 "ARF Update on BVD" pg 42

 

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MORE ARTICLES & INFORMATION

List of Articles from the CLAA:

 

  

Welcome to the Alpaca Research Foundation

The Alpaca Research Trust was established by the ARI Board of Directors in December, 1997 as a Colorado, non-profit corporation for charitable, educational and scientific purposes. The Board of Directors, of what is now known as the Alpaca Research Foundation, is composed of a select group of camelid veterinarians, research scientists and medical professionals. Their job is to establish research goals and critically evaluate research proposals from qualified research scientists.

The Mission of the Alpaca Research Foundation is to encourage and support scientific research which benefits the North American alpaca industry, primarily in the areas of alpaca health and husbandry, genetics and fiber.

Census: Confirmed BVDV Cases in Alpacas - Click Here.

BVDV - CONTROL WEBSITE

 

 

WISCONSIN DAIRY PRODUCER WEBSITE:

BOVINE VIRAL DIARRHEA VIRUS (BVDV)

What is BVDV and What Diseases Does It Cause?

BVD is an RNA virus that is classified into two different genotypes known as type 1 and type 2. Within each genotype there are several different strains of BVD virus that can differ significantly in their ability to cause disease. In addition, there are 2 different biotypes of BVDV called cytopathic and non-cytopathic with 99% of the field strains of BVDV being non-cytopathic. Infection with BVDV is most often inapparent or subclinical, but the virus can cause one or more of the following problems:

  • Abortion or early embryonic death (most important)
  • Pneumonia
  • Fever (temperature 105*F or greater)
  • Diarrhea
  • Lameness
  • Immunosuppression

How is BVDV Infection Spread?

If BVDV has not previously been on the farm, the virus is usually brought in by replacement animals or their unborn calves. Replacement animals can shed the virus in the air, manure and in body secretions. Susceptible animals typically become ill 10-14 days after exposure and usually develop a fever with signs of pneumonia. Often animals will also develop diarrhea and occasionally have ulcers and erosions in their mouths. Pregnant animals may abort beginning as soon as 1 month after exposure. Sometimes BVDV is introduced into a herd by people with contaminated footwear and/or clothing and occasionally by fence line contact with your neighbor's cattle.

Persistently Infected (PI) or Carrier Animals

How does an animal become persistently infected with BVDV?
An animal becomes persistently infected with BVD virus if the fetus is exposed to a slow-growing, non-cytopathic strain of virus between days 30 and 125 of gestation. Fetuses exposed to BVDV after 125 days of gestation will mount an immune response against the virus (which clears the infection) and usually develop quite normally. Fetuses exposed to a rapidly growing or "hot" strain of virus are usually killed, and the dairyman notices abortions or early embryonic death. It is important to remember that a persistently infected or PI animal is the only permanent carrier of BVD virus. Animals that are exposed to BVD virus (acute disease) may become infected and shed the virus for a few days but recover and become immune.

Do PI animals shed a lot of virus?
Yes, PI animals shed several billion viral particles a day and serve as a reservoir of BVDV in a herd.

Do PI animals remain in herds for a long time?
Yes and No. Ninety percent of PI animals are culled from dairy herds before they reach 2 years of age but some PI animals can remain in the herd for several years. However, new PI animals are constantly developing as a result of fetal exposure to BVDV from PI animals. Remember that a persistently infected or PI animal is the only permanent carrier of BVD virus.

Can I tell a PI animal by looking at it?
Some PI animals are stunted and are poor doing but many appear normal and cannot be distinguished from non-PI animals. You must test an animal to determine if it is persistently infected with BVD virus.

Can't I control BVDV infection in my herd with a good strategic vaccination program?
Yes and No. Vaccination usually protects animals from disease (illness and death) but does not protect them from becoming infected with the virus (subclinical infection). Subclinically infected animals can shed the virus in their blood (viremia) and hence expose the fetus to BVDV.

How common are PI animals?
About 1% or less of all cattle tested at the Wisconsin Animal Health Laboratories (WAHL) are persistently infected with BVDV. However, studies indicate that approximately 15% of the dairy herds in Wisconsin contain at least one PI animal. Some of the PI herds tested at WAHL contained 5% or more PI animals.

How do I find out if I have BVD virus present in my herd?
If you suspect acute BVDV infection or if you are concerned about the possibility of a PI animal(s) being present in your herd contact your veterinarian. He or she will know the proper samples to sent to the laboratory to confirm BVDV infection. If your veterinarian has any questions, he or she may contact the Wisconsin Animal Health Laboratory in Madison 800-608-8387 or Barron 800-771-8387.

Prevention and Management

  • Do not purchase BVDV infected cattle, especially bulls. Test all replacement animals for persistent infection prior to admission to the herd. In addition, the unborn calves carried by the replacement animals should be tested for persistent infection soon after birth.
  • Isolate all newly purchased cattle for at least 30 days, preferably on another farm.
  • Purchase only animals from herds with a known effective vaccination program. Get specific information about the vaccination history such as what vaccine was used and when it was given. If killed vaccines were used, make sure that a primary series (two doses given a few weeks apart) was given.
  • Make certain your own cattle are properly vaccinated according to the manufacturer's recommendations before bringing new cattle into the herd. Consult your herd veterinarian when developing a vaccination program.
  • Control farm traffic. Do not allow people to enter your barn without wearing clean footwear and coveralls. For more detailed information about biosecurity please read Biosecurity for Dairy Farms.

Additional information can be obtained by contacting your local veterinarian or the Wisconsin Department of Agriculture, Trade and Consumer Protection, Division of Animal Health, Wisconsin Animal Health Laboratories (Madison 800-608-8387 or Barron 800-771-8387).

AgriLabs WEBSITE: 

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Let's Talk BVDV
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Q: We have many well managed cow/calf operations in our practice and most now use a 5-way MLV for their cow and calf vaccination programs. A couple years ago we experienced some BVDV “breaks” which convinced us to use a product with a Type 2 BVDV, and we have had fewer overall incidents of BVDV since that time. However, another herd which changed to a 5-way MLV recently experienced BVDV problems among some of the cows and calves. The problem is now under control, but in the diagnostic work up we requested analysis by PCR to determine the BVDV genotype and to our surprise found it to be a Type 2. What is the degree and extent of protection afforded by popular, known effective vaccines against the two genotypes, subgenotypes, and all the different strains of BVDV?

DVM responds

Q: Our vet clinic has recently received information on recombination in BVDV vaccines. Should we be worried about recombination when using a modified live vaccine that contains both type 1 and type 2 cytopathic BVDV antigens in it?

DVM responds

Q: There seems to be a lot of information out recently regarding BVDV vaccine biotypes, ie. cytopathic and noncytopathic. Is this difference important in the selection of a MLV vaccine?

DVM responds

Q: With a modified live vaccine that contains both a cytopathic type 1 and cytopathic type 2 BVDV that has been clearly demonstrated to be safe in healthy calves, is it possible for this vaccine to cause problems due to recombination?

DVM responds

Q: Is it true that if a persistently infected calf is administered a modified live virus BVDV vaccine that the calf will develop a mucosal disease and die?

DVM responds

Q: Could you review the important points in determining which cow herds should be considered for PI testing and which should not?

DVM responds

Q: Is it true that the BVD virus can behave differently when it infects reproductive tissues?

DVM responds

Q: At times it seems that BVD can be difficult to recognize and confirm in the field. What factors are involved and why does it seem to take a long time for BVD titers to come up after a natural infection, and even sometimes after vaccination?

DVM responds

Q: What is the difference between cytopathic and noncytopathic biotypes of BVDV? And can they convert back and forth?

DVM responds

Q: Our practice has conducted PI testing on several herds this spring using the IHC ear notch test. The results in most cases were negative, but in a couple of herds (which had experienced repro problems) we identified PI calves. Please discuss some of the follow up steps for continued control and management measures.

DVM responds

Q: What tests are used for identification of PI animals?

DVM responds

Q: I recently heard the term CI. What is it, and what problems might it cause?

DVM responds

Q: Our practice recommends vaccination of calves at turnout/ branding time (approx. 2-3 months of age) and again at weaning. We have found this to be a very effective program. What are your thoughts related to vaccine response and interference of passive maternal immunity with this initial vaccination?

DVM responds

Q: Some MLV vaccines that contain only a Type I BVDV, claim that the product will cross protect against disease caused by Type II BVD. Isn't it true that this cross protection is incomplete and variable against virulent field isolates of BVDV?

DVM responds


How do you protect your herd from type 1 and type 2 BVDV?

What is PI?



BVDV Roundtable

BVDV – How do we define it?
BVDV Diagnostics
BVDV Tests
BVDV Vaccination

 

MSU EXTENSION WEBSITE:

Bovine Viral Diarrhea Virus

Bovine Viral Diarrhea Virus (BVDV) BVDV is a small RNA virus which is a member of the genus Pestivirus. It is closely related to hog cholera virus in pigs and border disease virus in sheep. BVDV can infect all ages of susceptible cattle including the unborn fetus.

The disease is spread primarily by cattle persistently infected with BVDV. Cattle become persistently infected with BVDV when exposed to the virus as a fetus by transplacental infection. Cattle acutely infected with BVDV can shed the virus for short periods of time primarily in respiratory tract and nasal secretions. Virus can also be transmitted through semen of both acutely and persistently infected bulls.

Two genotypes of BVDV exist: Type I and Type II.  Type II BVDV has been associated with more severe clinical disease including a hemorrhagic syndrome.

Cattle producers loose millions of dollars annually due to illness, pregnancy wastage, death and reduced production caused by infection with BVDV. 

Clinical Outcomes of Infection

The clinical outcome following infection with BVDV is dependent on the following factors: 

  • The virulence of the virus. Different isolates of BVDV may cause a range of clinical outcomes with varying severity. 
  • Immunity to BVDV. Previous exposure to BVDV through either natural infection or vaccination can change the clinical outcome following subsequent exposure to BVDV. 
  • Physiological state. Cattle suffering from immunosuppression may be more susceptible to more sever clinical outcomes following infection with BVDV.
  • Pregnancy status. BVDV can infect the developing fetus at all stages of gestation resulting in a variety of outcomes. 
Acute Infection: Cattle susceptible to infection with BVDV can become acutely infected. The outcome is dependent on the above factors and may include: 
  • Subclinical infection. This is the most common outcome. 
  • Fever, anorexia, diarrhea, production drop. 
  • "Mucosal like" disease. 
  • Sudden death. 
  • Suppression of the immune system with subsequent secondary infections. This may be the major role for BVDV as part of the bovine respiratory disease complex. 
  • Hemorrhagic syndrome. Bleeding occurs as a result of a decrease in platelets. 
The reproductive effects of BVDV occur most commonly following acute infection of the dam. The outcome is dependent on the stage of gestation and the virus isolate. 
  • Poor conception rates. Results from infection around the time of breeding. 
  • Early embryonic deaths. Results from infection during the first 30 days of gestation. 
  • Abortions. Abortions can occur at any stage of gestation. 
  • Congenital defects. Occur most commonly following infection mid gestation. 
    • Cerebellar hypoplasia 
    • Cataracts and retinal atrophy 
    • Hypotrichosis 
    • Weak, undersized calves. 
  • Seroconversion to BVDV. Exposure during the last 3 months of gestation usually results in the birth of a normal calf. 
  • Fetal immunotolerance. Exposure to BVDV before the fetal immune system is developed (before day 125 of gestation) can result in BVDV immunotolerance. This results in a persistent life-long infection in surviving calves. 
Cattle become persistently infected when they are exposed to the virus as a developing fetus before day 125 of gestation. Following birth several outcomes may occur. Normal productive life. However these cattle are continually shedding virus into the environment and are the major source of virus for susceptible herdmates. Weak, unthrifty calves. These calves often die at a young age from secondary diseases such as pneumonia. Poor producing as adults. Development of mucosal disease. Classic mucosal disease occurs only in cattle persistently infected with BVDV. It most commonly occurs following a mutation of the persisting virus. It may also occur following vaccination with a modified live BVDV vaccine containing cytopathic virus. Various forms of mucosal disease exist (Acute, Chronic, Delayed onset) but all are fatal.

Diagnosis

Virus Isolation 

  • Persistent Infection 
    • Adults — Serum 
    • Calves — Serum if pre colostrum or older than 4 months of age. 
    • Calves — Whole blood if post colostrum and less than 4 of months age.
  • Acute Infection
    • Whole blood. 
  • Post Mortem 
    • Spleen, Peyer's patch, lymph nodes.
  • Abortion 
    • Spleen, thymus. 
Serology 
  • Acute and convalescent serum. 
Herd Screening
  • Bulk milk tank. 
  • Pre immunization antibody titers at 6-12 months of age.

Control & Prevention 

The key to the control and prevention of BVDV infection is to detect and eliminate cattle persistently infected with the virus

Elimination of Carrier Animals 

  • Herd testing.
  • Test calves at birth.
Immunization 
  • Modified live or killed vaccines. 
  • Maximize immunity pre-breeding and early gestation.
Biosecurity 
  • Closed herd. 
  • Test all new arrivals 
  • Test newborns of new arrivals.
    Quarantine all new arrivals and reintroduced cattle for 21 days.

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