Inf. diseases II - Ruminant respiratory disease 2/2 Flashcards
Bovine viral diarrhea (BVD) ) is a highly contagious disease of cattle, caused by a Pestivirus, and characterized by (3)
variable diarrhea,
respiratory illness and
persistently infected (PI) calves.
Causative agent of BVD.
genus, family, DNA type
Bovine viral diarrhea virus (BVDV)
Genus Pestivirus,
family Flaviviridae
RNA virus
Biotypes/strains of BVDV.
Bovine viral diarrhea virus
Biotypes 1 and 2
- 1 – worldwide
- 2 – North America and occasionally Europe
Both biotypes have non-cytopathic and cytopathic forms.
Non-cytopathic (NCP) form is most common.
Variable clinical disease with enteritis and respiratory illness .
Causes persistently infected (PI) animals after intrauterine transmission.
Cytopathic (CP) form causes mucosal disease in persistently infected PI animals.
Causes cytopathic effect in cell culture
Both BVDV biotypes have non-cytopathic and cytopathic forms.
Describe the non-cytopathic (NCP) form.
Non-cytopathic (NCP) form is most common.
Variable clinical disease with enteritis and respiratory illness .
Causes persistently infected (PI) animals after intrauterine transmission.
Both BVDV biotypes have non-cytopathic and cytopathic forms.
Describe the cytopathic (CP) form.
Cytopathic (CP) form causes mucosal disease in persistently infected PI animals (those who get infected in utero?).
Causes cytopathic effect in cell culture.
What all types of disease can BVDV cause? (6)
benign bovine virus diarrhea,
mucosal disease,
peracute fatal diarrhea,
thrombocytopenia and hemorrhagic disease,
reproductive failure,
congenital abnormalities in calves.
Host range of BVDV.
ruminants, especially cattle
Found worldwide.
(NOT in humans but this is a notifiable dz nonetheless)
Morbidity of BVDV.
Morbidity 40%
Mucosal disease: <5%
Mortality of BVDV.
Mortality 20%
Excretion of BVDV.
Excretion: nasal discharge, saliva, semen, feces, urine, tears and milk, aborted fetuses
Major source of virus: PI animals!!!
Transmission mode and route of entry of BVDV.
Direct contact
Transplacental transmission
Indirect transmission: fomites, flies and airborne
Route: oral, respiratory, genital, transplacental
Clinical signs of BVDV.
Can result in a wide spectrum of clinical dz varying from subclinical infection (70-90%) to fatal dz.
Most common signs:
Infertility or abortion
Diarrhea
Mucosal disease
Respiratory signs
How does the fatal hemorrhagic disease form of BVDV develop?
Immunocompetent adult animals can experience transient infection, but if the animal happens to be pregnant before day 120 of gestation, the fetus will be become persistently infected (if it doesn’t abort).
Only the ncp biotype can cause persistent infection of the bovine fetus.
Initially the fetus is infected with the non-cytopathic biotype, this can mutate and become cytopathic and eventually cause fatal hemorrhagic mucosal disease. Typically die before 2 years old.
There are two different strains of BVD: Transient type 1 and type 2.
Both strains can have the same effect on fertility and overall health, however type 2 can be more severe and can result in bleeding syndrome and death.
Describe differences in the symptoms of each type.
Infection with BVDV from approximately nine days prior to service until 120 days of gestation may result in: (4)
Failure to conceive
Early embryonic death
Fetal loss
Persistently infected (PI) calves
Clinical signs of mucosal disease BVDV.
Fever
Diarrhea
Inappetence
Progressive emaciation
Rough dry hair coat
Chronic bloat
Hoof deformities
Chronic erosions in the oral cavity and on the skin
IP of BVDV mucosal disease.
IP animals 6-24 months of age
Morbidity of BVDV.
Morbidity 44%
Mortality of BVDV.
mortality <100%
Post mortem signs of mucosal disease BVDV.
lesions in alimentary tract
Erosions
Lesions on Peyer’s patches
Pneumonia (mostly secondary)
If you test a cow’s blood and its positive for BVDV virus but negative for antibodies against BVDV - what is it?
a persistently infected individual
then if its virus mutates or it happens to catch the other strain (cytopathic), it develops fatal mucosal disease.
Tx for BVDV.
no tx
Prevention & control of BVDV. (3)
Control:
Detection and elimination of PI animals from the herd
Prevention of introduction of infection into herd
Vaccination of breeding females to prevent fetal infection
Eradication of BVDV by
detection and elimination of persistently-infected animals (in this case, you can’t have used vax (in order for you to be able to identify them)) and strict biosecurity measures to prevent introduction of PI animals into the herd.
Mycoplasma bovis infection is a contagious disease of cattle, characterized by (4)
respiratory disease,
mastitis,
arthritis and
otitis media.