Bovine Virus Diarrhea Virus

Jessica Seate

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BVDV, What is that??

BVDV has two biotypes: non-cytopathic (NCP) and cytopathic (CP) (defined by the growth characteristics of the virus in cell culture). The predominant biotype is the non-cytopathic

BVDV is also divided into two genotypes: BVDV type 1 and BVDV type 2, based on the antigenic and genetic differences. Both genotypes are capable of causing severe disease and containing both the CP and NCP forms.

Diseases related to BVDV cause economic losses to cattle producers throughout the world due to:

decreased performance

loss of milk production

reproductive wastage

increased risk of morbidity and mortality

BVD is currently one of the most costly diseases of cattle. Cost estimates in herds with BVD range from $24 to $200 per cow per year.

Bovine viral diarrhea virus (BVDV) is a single stranded RNA virus that is a member of the family Flaviviridae and is of the genus Pestivirus. It is related to classical swine fever in swine and border disease in ovine.

BVDV was first identified in cattle 1946 and initially thought to be a gastro-intestinal disease, however, today it is primarily associated with reproductive problems

Transmission

Horizontal

Direct contact with body fluids from

PI cattle. Virus has been isolated from

nasal swabs, aerosols, saliva, urine,

feces, semen, and uterine fluids from

PI cattle.

Introduction of an acutely infected

animal or pregnant animal carrying a PI

fetus

Fence contact, communal pastures, and

shows/exhibits

Contaminated instruments

Animal caretakers

Transplacental

VERY EFFICIENT

Can result in persistently infected

calf

Factors influencing pathogenesis: pregnancy status

gestational age of the fetus at time of infection

immune status (passive or active from natural

exposure or vaccination)

concurrent level of environmental stress at the time of infection

genetic diversity

antigenic variation

differences in virulence among

BVDV isolates

The BVDV complex can result in subclinical

benign bovine viral diarrhea, fatal mucosal disease,

peracute fatal diarrhea, immune suppression,

thrombocytopenia and hemorrhagic disease,

reproductive failure, and congenital abnormalities in

calves

For this presentation, BVDV infections fall into three broad types:

acute infection, fetal infection, and persistent infection (PI).

Acute Infection of Neonates

Associated with failure of passive transfer

Clinical Presentation: enteritis and pneumonia

cough

cough

Acute Infection of Calves at 6-24

months in age

Most acute BVDV infections are subclinical (70 to 90 % of infections) in nature, resulting only in mild fever, leucopenia, inappetence, depression, and the development of antibodies. These infections often go undetected and usually last only a couple of days.

Incubation period of the virus is 5-7 days

Clinical Presentation: fever, leucopenia, depression, anorexia, oculonasal discharge, oral erosions, ulcerations, diarrhea, decreased milk production

Acute infections can cause impairment of the immune system giving opportunities to secondary infections.

Viremia lasting 2-5 days, possibly two weeks

Severe Acute Infection

Acute course with high morbidity and

substantial mortality (10-20%)

Clinical Presentation: fever, pneumonia,

ulcerations, sudden death, abortions are

common

Respiratory Distress Esophageal Ulcerations Erosions of Peyer’s Patches

Hemorrhagic Syndrome

BVDV has an affinity for cells of the bone

marrow (primarily the megakaryocytes):

Results in: decreased platelets and bleeding disorders

Clinical Presentation: epistaxis, bloody diarrhea and

vomit, hemorrhages of mucosal surfaces, pyrexia,

leucopenia

HIGHLY FATAL!!

Bovine Respiratory Disease Complex

Since BVDV is a lymphotrophic virus and can

induce immunosuppression it plays an important

role in the bovine respiratory disease complex

(“shipping fever”) in feedlots.

It potentiates infections by now allowing other

pathogens (BRSV, M. hemolytica) to cause effect

that normally would not be able to do so alone.

Developmental defects

(100- 150days of gestation)

hydrocephalus

cleft palate

cerebellar hypoplasia or

aplasia

Torticolli, wide stance, ataxia

if born alive

hypotrichosis

Retinal atrophy,

cataracts,

microophthalmia

Persistent Infection Regardless of their prevalence, PI animals are typically

the largest source of infection in any given herd

Infection of the fetus during the first trimester (50-125 days) can result in the birth of an animal that is persistently infected (PI) with BVD. Takes about five months in utero for the immune system to react, before that calves are immunotolerant. Carries the virus for life

Sheds loads of BVD virus in all secretions and excretions

Level of virus being shed is HIGH

PI animals are sickly since the infection can impair their normal immune function and end up being culled or dying before reaching adulthood

PI animals are the means by which BVDV is maintained in the bovine population. Important to identify these PI calves after birth by observation or screening and

eliminating the PI calf and mom from the herd

**Death rate of PI calves is 50% during 1st year of

life

**Fewer than 10% of PI dairy replacement heifers

reach lactating herd

Mucosal Disease

Acute Mucosal Disease

Clinical Signs: severe bloody

diarrhea, erosions of gums, hard palate

lesions, tongue lesions, esophageal

ulcers, hyperemia of rumen and

abomasum, lymphoid depletion of

thymus and spleen, decreased milk

production, fever, anorexia, secondary

infections leading to pneumonia,

mastitis, metritis

High Mortality

Short Disease Course of 3-10

days

Chronic Mucosal Disease

** NCP and CP strains are less

closely related as they are in

acute mucosal disease

Clinical Signs: lameness,

interdigital necrosis,

immunologically compromised,

SEVERE emaciation,

secondary bacterial infections

Usually Fatal

“Eye Opener” for indicating BVDV is circulating in a herd

Calf is infected in utero by a non-cytopathic strain during 50-125 days

of gestation

The non-cytopathic strain transforms into a cytopathic variant of that

strain

Testing/Diagnostics

Virus Isolation

Tissue, whole blood, serum

Antibody Detection tests

Serum Neutralization

Nucleic Acid Detection

PCR testing

Antigen Detection tests

fluorescent antibody test (frozen tissues)

immunoperoxidase test (formalin fixed tissues)**The choice of test depends on the

current clinical problem and on the

past test data from the herd or animal.

BVDV Ear Notch Sampling: by far the

most common diagnostic sample in

calves less than 3 months of age for

persistent infection (perform either IHC,

ACE, or PCR)

Tests Available

BVDV Tests Offered by Cornell Diagnostic Laboratory

1. Bovine Viral Diarrhea Immunohistochemistry (IHC) test

2. Bovine Viral Diarrhea Serum Isolation (with IHC detection)

3. Bovine Viral Diarrhea Fluorescent Antibody test (FA)

4. Bovine Viral Diarrhea Virus Isolation

5. Bovine Viral Diarrhea Virus Serum Neutralization test (SN)

6. Bovine Viral Diarrhea Serum Isolation

7. Bovine Viral Diarrhea Whole Blood Isolation

8. PCR Detection Using (Bulk) Milk Samples

9. Bovine Viral Diarrhea Antigen Capture ELISA test [ACE](serum)

10. Bovine Viral Diarrhea Antigen Capture ELISA test [ACE](skin)

11. Pooled PCR testing for herd screening

12. BVDV PCR test

•Any combination of these tests are appropriate for multiple circumstances. For instance

if there is a suspected Chronic BVD case, Found dead animal with suggestive lesions,

Possible PI in herd, Cattle with sporadic abortions and poor reproductive performance,

and even for animals that are being shipped for AI purposes.

Treatment/Prevention

Animals persistently infected with BVDV are an important target for control of transmission

Strategic management of the production

system, diagnostic investigation, vaccination., herd-monitoring, biosecurity and biocontainment programs.

Each management program will need to involve multiple components and customized to fit the goals and capabilities of each producer.

As treatment infected animals is not a

viable option:

the control, prevention, and future

eradication efforts for this disease must

be implemented by the cow-calf

industry and by individual dairy barns

Cows and heifers need to be well protected during FIRST TRIMESTER of pregnancy. Recommend vaccination of cows and heifers with a modified-live BVD

vaccine a few weeks before breeding for adequate protection during early pregnancy.

Or...a killed vaccines can be administered to all animals, semi-annually. Killed vaccines must be administered twice (two to four weeks apart) if the animal is being vaccinated for the first time (i.e. heifers).

Without the booster vaccination, animals are not protected against BVD, even if they receive annual revaccinations with the killed product

Bovine Viral Diarrhea Control

Procedures/Protocol

1. Implement an effective immunization program

a. Vaccinate heifers initially with a modified-live BVD vaccine

b. Booster in 2-4 weeks with a modified-live or killed BVD product

c. Booster annually (MLV to open animals only), or semi-annually (killed).

d. Depending on vaccination history, all purchased animals should be vaccinated

against BVD at least once, and possibly twice.

e. Store and handle all vaccines according to label recommendations

2. Maintain a closed herd if possible.

3. If expanding, purchase replacements from a local grower practicing good animal

husbandry. Isolation of new additions for minimum of three weeks.

4. Test all purchased animals for BVD persistent infection (PI) status.

Protocol Continued

5. Test all replacements for BVD PI status either before colostrum feeding or at 3-4 months of age.

6. Cull any PI animal and its offspring.

7. Prevent disease entry into the herd by

a. Isolating all animals entering the facility (replacements, bulls, and animals

returning from shows or contractual raising) for two weeks.

b. Requiring clean boots, clothing, and equipment for people and employees

entering the premises.

c. Moving dead and down cows away from the facility prior to pickup.

d. Moving animals with your own truck, or at least insisting on a clean truck

moving only your animals.

e. Purchasing semen from AI establishments with active BVD screening

procedures.

Differentials Acute Infection of Neonates:

Rotavirus

Corona virus

Cryptosporidium

E.Coli

Salmonellosis

BRSV

Pasteurellosis

Coccidiosis

Hemophilosis

Mycoplasma

Acute Infection of 6-24 months:

Salmonella

Winter dysentery

Johne’s Disease

Malignant Catarrhal Fever

Vesicular Stomatitis

FMD

Bluetongue

Intestinal parasites

Arsenic poisoning

Severe Acute Infection:

Mucosal Disease

References:

Baker, JC. (1995) The clinical manifestations of bovine viral diarrhea infection. Vet Clin North Am Food Anim Pract. 13(3):425-54.

Brook, K.V. (2004) Strategies for the control and prevention of bovine viral diarrhea virus. Vet Clin Food Anim.20:171-180.

Campbell, J.R. (2004) Effect of bovine diarrhea virus in the feedlot. Vet. Clin. North. Am. Food Anim. Pract. 20(1):39-50.

Grooms, DL. (2009) Integrated BVD Control Plans for Beef Operations. The Bovine Practitioner 43(2): 106-116.

Dr. Maes Virology Notes MMG 565

Merck Veterinary Manual Ninth Ed. Merck & Co., Inc. 2005: 220-222

Smith, BP. Large Animal Internal Medicine. 4th ed. Elsevier Inc. 2009: 610-611