Bovine Virus Diarrhea Virus -...
Transcript of Bovine Virus Diarrhea Virus -...
Bovine Virus Diarrhea Virus
Jessica Seate
LCS 630 Rotation
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