Viral and Bacterial Infections Flashcards
What are the two types of horizontal transmission?
Venereal - virus present in semen or in lesions of the genital tract
Haematogenous or ascending - spread to genital tract from other sites, particularly upper respiratory tract
What ways can vertical transmission occur?
Placental - haematogenous
Genital tract - ascending, spreads to foetus through cervix or infection during birth
Milk
What can reproductive failure be caused by?
Viral replication in foetal tissues leading to malformation or death
Damage to placental blood vessels leading to interrupted blood supply to the foetus
Stress and pyrexia due to viral infection
A combination of the above
Describe a carrier animal
Shedding of virus without clinical signs - in semen, respiratory secretions, faeces
Shedding may be intermittent
What are the two viruses of the reproductive tract of the horse?
Equine herpesvirus (EHV) Equine arteritis virus (EAV)
What are the three types of equine herpesvirus?
EHV-1 - abortions, respiratory disease, paralysis
EHV-3 - genital pustules, not abortion
EHV-4 - respiratory disease, rarely isolated abortions
Describe EHV-1 cycling
Over 90% of carrier horses in UK are latently infected Virus is reactivated from latency Nasal shedding of infectious virus Young horses are infected Recruitment of new hosts into cycle Viral latency established Horses latently infected again
Decribe EHV-1
Abortion in last third of pregnancy
Lung oedema
Multifocal necrosis in liver, lungs and spleen
Abortion accompanies or occurs shortly after foetal death
How can EHV-1 abortion be diagnosed?
Post mortem examination of foetus and placenta
PCR or virus isolation
Microscopic examination of tissue sections
EHV-1 immunostaining
How can EHV be prevented?
Isolation of pregnant mares during last trimester
Vaccination of all horses on the premises
Combination vaccines EHV-1 and EHV-4
Describe EHV control
Isolate affected mare if abortion
Collect foetus and placenta for testing
Paired serum samples from mare to test for rising antibody titre
Describe equine arteritis virus
Arterivirus Causes equine viral arteritis (EVA) Notifiable disease Last case in UK in 2012 Entry via respiratory tract or semen Infects macrophages and endothelial cells and causes arteritis
How is EAV abortion diagnosed?
Clinical signs in mare - variable, fever, depression,conjunctivitis, abortion
Post mortem examination of aborted foetus and placenta
Virus-neutralising antibody levels in mare high at abortion or rising
Stallions are persistently infected and shed virus in semen
Investigate if travel history
What problems are there with EAV diagnosis?
Subclinical
Stallions can shed intermittently or persistently
Virus persists in accessory glands
Not considered to persist in mare
When is EVA notifiable?
Clinical signs observed in stallion
Evidence for EAV infection by semen or blood testing
Clinical signs or laboratory results indicate EVA - mare mated or artificially inseminated within past 14 days
Describe EAV control
Diagnosis on aborted foetus or semen samples using virus isolation or PCR
Movement restrictions
Vaccination of stallions
What are the four viruses of the reproductive tract of cattle?
Bovine viral diarrhoea virus
Bovine herpesvirus
Schmallenberg
Bluetongue
Describe BVDV
Pestivirus
Shed in respiratory secretions and faeces
Transmission also via semen during AI
Virus replication in respiratory and enteric tract
Haematogenous spread to foetus via placenta
What may BVDV damage to the developing foetus lead to?
Stillbirths Abortions Early foetal death with reabsorption Infertility Mummification Congenital damage - cerebellar hypoplasia, retinal dysplasia
Describe BVDv infection timing
First trimester (0-110 days) - embryonic/foetal death causing resorption/abortion/mummification, persistent infection Second trimester (111-190 days) - abortions/mummification, PIs usually only until day 140, congenital deformities (esp. days 125-175) Third trimester (after day 191) - occasional abortions/still births/weak calves, predominately normal calf
How can BVD abortion be diagnosed?
PM examination on aborted foetus with PCR of lymphoid tissue
Histopathology with immunohistochemistry
Foetal serology on free foetal fluids for indication exposure
Maternal serology
Describe prevention and control of BVDV
Endemic in UK
Vaccination of dams before pregnancy
Identify and remove persistently infected animals
Various European countries have eradication programs
Describe BHV-1
Causes - Infectious bovine rhinotracheitis (IBR), infectious pustular vulvovaginitis (IPV), infectious balanoposthitis (IBP)
Transfers - venereal, contact, aerosol
Describe IPV/IBP
Painful genital lesions
Swelling
Frequent urination
Tend to be self-limiting
Describe BHV-1 abortions
Follow respiratory infections Abortion may occur weeks after infection of dam Usually at 4-8 months of gestation Necrosis in foetal liver and lung Frequently extensive autolysis Abortion due to BHV-1 uncommon in the UK
How can BHV-1 be diagnosed, prevented and controlled?
Latent herpesvirus can become reactivated due to stress
Isolate and test new stock to prevent herd spread
Diagnosis - immunofluorescence/immuno-peroxidase on foetal tissues
Serological testing difficult to interpret
Vaccination reduces severity and duration of clinical disease
Eradication programs in various European countries
Describe Schmallenberg virus
Orthobunyavirus
Arbovirus
Infection of dam during early pregnancy
Virus has neurotropism
Common findings in foetuses/neonates - arthrogryposis, hydranencephaly, cerebellar/cerebral hypoplasia
Diagnosis - PCR, histopathology, foetal serology, maternal serology for indication
Describe bluetongue
Orbivirus Arbovirus Abortions Congenital defects due to teratogenic effect - hydranencephaly Notifiable
What viruses cause reproductive failure in pigs?
Porcine respiratory and reproductive syndrome (PRRS) Porcine parvovirus Influenza virus Porcine circovirus 2 Suid herpesvirus 1 - Aujeszky's disease Swine fever
Describe PRRS
Family Arteriviridae
Infection of respiratory tract via aerosol
Genital tract infection via virus infected semen
Respiratory disease and oedema or subclinical
Blue ear disease
Less virulent strains may not cause obvious clinical signs
Immunosuppression
Late abortions/mummification/premature piglets
How can PRRS be diagnosed in abortions?
PCR of lymphoid tissue
How can PRRS be prevented and controlled?
PRRS is endemic in UK
SPF, all in
Separate pregnant sows from rest of herd
Avoid transfer of fomites
How can PRRS be prevented and controlled?
Screening of semen for AI by PCR
Vaccination with inactivated vaccine
PRRS rapidly mutates leading to circulation of many genetic and antigenic variants
This makes diagnosis and control by vaccination difficult
Describe porcine parvovirus
Stillbirths, mummification, embryonic death and infertility (SMEDI)
Abortion uncommon
Transmission - faecal oral
Replicates in GIT without clinical signs
Transplacental infection of foetus
Early embryonic death leads to resorption
Infection at later stages causes death of foetus with mummification
Death at late stages leads to stillbirths
If infected >70 days, foetal death less frequent due to immune response
How can porcine parvovirus be diagnosed, prevented and controlled?
PCR on liver tissue if CRL is <70 days
Foetal fluid serology in older immunocompetent foetuses
DIagnosis by immunofluorescence on frozen foetal liver
Virus isolation
Vaccination
Describe swine influenza
TypeA influenze virus (H1N1, H3N2)
Predominately respiratory signs
Pyrexia >41 degrees Celcius
Abortions predominately due to disease in sows
Transplacental infections considered rare
Diagnosis - PCR in acutely infected sows, paired serology
What are two notifiable pig diseases?
Aujeszky’s disease
Swine fever
Describe Aujeszky’s disease
Pseudorabies Family Herpesviridae Notifiable Entry via respiratory tract CNS signs and high mortality in piglets Pregnant sows - haematogenous spread to foetus, abortions/stillbirths Eradicated from UK
Describe classical swine fever
Pestivirus in family Flaviviridae Notifiable - last outbreak in UK in 2000 High mortality Diarrhoea Haemorrhages in skin and other organs Abortion, mummification, stillbirths, congenital tremors
Describe African swine fever
Family Asfaviridae
Notifiable
So far never occurred in the UK
Clinical signs very similar to classical swine fever
Describe canine herpesvirus
Infection of pups during birth or shortly after birth can lead to systemic herpesvirus infection
Part of Fading Puppy Syndrome
Immature immune system and poor body temperature regulation allows infection to establish
Organ necrosis and death
Haemorrhages esp. in kidneys
Diagnosis by gross and histopathological findings
Vaccine now available for pregnant bitches
What are the two viruses causing reproductive failure in cats?
FLV - feline leukaemia virus
FPV - feline parvovirus (feline panleucopenia virus)
Describe FLV
Can cross placenta and elad to reproductive failure
Diagnosis - antigen test, immunofluorescence/PCR on aborted foetuses
Prevention - vaccination
Describe FPV
Can elad to reproductive failure
Canlead to cerebellar hypoplasia
Prevention - vaccination
What are the two laboratory diagnoses of reproductive failures?
Detection of virus
Detection of antibody
Describe viral detection
Samples from foetal organs or whole foetus as well as placenta
Virus isolation, PCR or antigen detection
Problems if sampes aren’t fresh - viruseslose infectivity, nucleic acids and proteins degrade
Describe antibody detection
Antibody detection in foetal fluids
Serology of the dam showing rising antibody titres
Problems with possible delay between - infection of dam and foetus, infection of foetus and reproductive failure becoming apparent
What are the six bacterial consequences of infection?
Abortion Endometritis Metritis Infertility Prostatitis Orchitis
What are the three routes of transmission for bacterial infections?
Venereal transmission
Endogenous infection
Environmental infection
What are the six bacteria that can cause bovine abortion?
Leptospira hardjo Bacillus licheniformis Salmonella dublin Brucella abortus Brucella melitensis Mycoses
What is the biggest cause of cattle abortion?
Leptospira hardjo
What sort of infection does Leptospira cause?
Subclinical
What is the reservoir of infection for Leptospira?
Animals - cattle, sheep, others
Is Leptospira zoonotic?
Yes
How can Leptospira be diagnosed?
Sera from a group representative sample of the animals
Examined by microscopic agglutination test at VLA
Describe Bacillus licheniformis
Causes cattle abortion
From environment
Opportunist causing sporadic occurrences of abortion
Probably not spread from animal to animal
Describe Brucella abortus
Largely eradicated in UK
Remains common in many parts of the world
Reservoirs of disease in wildlife
Chronic infections - granulomatous lesions
Organisms enter via phagocytosis at mucosal surfaces
Migrate via lymphatic to blood
Localises in lymphatics, liver and spleen
Organism attracted to placenta in pregnant animals
Causes placentitis and abortion
Zoonotic
Spreads easily through a herd
Facultative intracellular pathogen hiding in liver cels
How has Brucella abortus been eradicated in the UK?
Vigorous policy of testing for antibody and slaughter of reactors
Vaccination using both live and killed vaccines
Describe Salmonella enterica infection
Causes abortion Invasive serovars (S. Dublin) can cause a septicaemia Invasive serovars can also cause abortion in pregnant animals
Describe mycotic abortion
Due to Aspergillus sp. mainly
Many different fungi recorded as a cause
High numbers of fungal spores inhaled or ingested
Haematogenous migration to placenta
Placentitis and death of foetus
Subsequent fertility and health of the cow is unaffected
May also cause equine abortion
Describe Bovine Infectious infertility
Caused by Campylobacter fetus subsp. venerealis
Mucous membrane and prepuce of mature bull
Lifelong asymptomatic infection
Infection of the cow at service leads to catarrhal inflammation of gential tract, endometritis and inflammation
Return to service and infertility
Detected by culture - sheath washings, vaginal washings or products of abortion
Describe Bovine endometritis
Inflammation of uterine mucosa
Non-specific bovine endometritis - Arcanobacterium (Actinomyces) pyogenes, E. coli, Streptococci
Leads to pyometra - acute or chronic suppurative infection
Luteolysisprevented by inflammation
CL retained
Drainage prevented by closed cervix
What is the main cause of abortion in sheep?
Chlamydophila abortus
Describe Chlamydophila abortus
Obligate intracellular pathogens Long-term persistent infection Late pregnancy abortion in ewes Subsequent fertility not impaired Enzootic abortion
What is the reservoir for Chlamydophila abortus?
Sheep infection, faeces and birds
Venereal or oral transmission
Antigen detection by ELISA and Kosters stain
Vaccination prevents new cases but does not clear established infection
Describe Campylobacter fetus subsp. fetus
Sporadic abortion in cattle and sheep
Reservoir in intestinal tract and faeces on pasture
Ingestion - invasion - blood - bacteraemia - placenta - abortion
Describe canine reproductive tract infections
Pyometra and endometritis - Coliforms (E. coli), Beta-haemolytic streptococci (S. canis, S. zooepidemicus)
Prostatitis - non-specific infections, E. coli, Proteus, Streptococci, Staphylococci, Mycoplasma felis
Which bacteria causes abortion in mares?
Streptococcus zooepidemicus - Beta-haemolytic streptococci, Lancefield group C
Describe contagious equine metritis
Taylorella equigenitalis Acute Contagious Venereal transmission Metritis, cervicitis, discharge Originally from USA and eradicated from UK Spread by stallion at service and by fomites Diagnosis by culture and by PCR Serology gives uncertain results
Describe equine metritis
Klebsiella pneumoniae
Serotypes - K1, K5 and K7
Culture to demonstrate freedom from infection
