Lecture 5 - animal pathogens 2 Flashcards
what is foot and mouth disease?
Foot and mouth disease (FMD) is a virus of hoofed animals e.g. pigs, cows, sheep, goats etc
First animal virus discovered in 1898
Highly contagious, outbreaks difficult to control
- virus of greatest economic threat to agriculture
In 2021 UK spent £3 billion and 6.5 million animals slaughtered
- containment measures essential
what is foot and mouth disease virus?
Picornavirus of cloven-hoofed livestock
- non-enveloped positive ssRNA virus
- 7 serotypes complicate diagnosis/vaccination
Endemic in Asia, Africa and South America
- export of infected livestock to Europe is not uncommon
- important to contain trade of animals and animal products
The incubation period can be up to 2 weeks
what is the FMDV the disease?
Spreads quickly in immunocompromised animals, with high rates of morbidity
Debilitating illness affecting the productivity
>40.0°C fever
loss of appetite and increased salivation
depression and drop in milk yield
virus causes temporary immunosuppression
Serious long-term effects
- reduced milk production
- lameness
how is FMDV spread?
Can be spread over larger distances through abiotic surfaces
- footwear, vehicle wheels
- may survive in the environment for several months
what are the major outbreaks of FMDV?
-In 2001, FMDV detected at Essex abattoir on 19th Feb, later discovered the outbreak originated elsewhere
- 2030 cases, 6 million animals culled
- £2.5 billion for compensation, disposal, clean-up
- huge effect on tourism
The UK is FMDV-free, mainly due to the containment of the outbreak through culling.
In 2007, FMDV detected at Surrey farm on 3rd August, however this was controlled more quickly than 2001.
Control mechanisms
- protection/surveillance zones
- all animals culled
- nationwide ban on movement
Causative strain characterised and identified as one from government research lab
Recent outbreaks in Germany
How is FMDV diagnosed?
Virus detectable 2 days prior to clinical manifestations
Environmental shedding, very contagious state
DIAGNOSTICS
Antibody based
qPCR
Sequencing
assays for FMDV detection- look at imagine
how do you control FMDV?
Slaughter of infected animals and uninfected contacts
Disinfection of premises
Imposed restriction on movement of stock
- 10 km radius
- includes animal products e.g. milk, carcasses etc
- no entry/exit to infected area
Notifiable disease
- illegal to observe symptoms and not report
how is FMDV vaccinated?
Vaccine is available but immunity is short-lived
Routine preventative vaccination is banned under EU law
- can vaccinate all animals but cannot sell them
- used during an outbreak to reduce symptoms and prevent spread
- cannot distinguish between vaccinated and naturally infected
Animals (infected or vaccinated) can develop carrier status
- FMDV remain in the lymph nodes
- source of persistent infection
what are the challenges to vaccinating FMDV?
Existing vaccines are live, chemically attenuated
- production is risky (2007 outbreak) and therefore costly
Seven serotypes, each with many variants due to high viral mutation rate
- challenging to produce vaccine against all strains
Intact virus is fragile
- costly to store and distribute, limited life span
Subunit vaccines are in development
- non-pathogenic, more stable, can they give protection?
What are the diseases of cats?
Wildcats are endangered species therefore infections in domestic cats can infect wildcats and put them in danger of extinction.
what are feline viruses?
> 10 million cats in the UK
0.5 million healthy cats thought to carry Feline Leukaemia Virus (FeLV) or Feline Immunodeficiency Virus (FIV)
Both supress the immune system
- can leave the host susceptible to other infections (toxoplasmosis)
Retrovirus
enveloped virus
RNA genome +ve ssRNA
uses reverse transcriptase for replication
retroviral DNA integrates into host genome
what is feline leukaemia virus (FeLV)
FeLV discovered by William Jarrett and colleagues at UoG Vet School
Transmitted via saliva, bites and licks
Causes immunosuppression/deficiency, anaemia and lymphoma in cats
30-40% stay viraemic, however persistent viraemic cats die within 2-3 years
Feline leukaemia initially thought to be a cancer
Found to be transmissible & viral particles discovered
All those infected had leukaemia, further studies discovered the virus
Later showed the virus could be horizontally transmitted
Also carried out early work on vaccines, developing 1st whole inactivated FeLV vaccine
what is feline immunodeficiency virus (FIV)?
FIV is the cat equivalent of HIV
- infects T helper cells
- impairs immune system
- spread by bites/scratches
Similarities make FIV a good model for HIV studies
- cats are in vivo model
- not working with human pathogen
Fel-O-vax – chemically inactivated whole virus
- underutilised as no differentiation in diagnostics
what are the symptoms of FIV?
Common signs:
Loss of appetite
Enlarged lymph nodes
Persistent fever
Pale gums
Inflammation of the gums
Secondary infections
Persistent diarrhoea
Behaviour changes
Abortion
What is the treatment and control of FIV?
Variety of vaccines are now available
No vaccine is 100% effective
Supportive therapy & nursing
- treat secondary infections
- maintain vaccinations
- keep cat indoors
DIAGNOSIS
ELISA, false +ve common
PCR
Virus culture (viraemia)
what are bird diseases?
Birds are important in farming, pets, wildlife with many diseases being zoonotic bird flu
In 1997, Influenza A H5N1 transmitted to humans
- 60% mortality rate, 359 deaths since
- currently circulating in poultry in Asia/Africa
H7N9 is less deadly but is difficult to track
- discovered in China (2013)
- 30% mortality rate, can resist Tamiflu
what is avian influenza?
Family – Orthomyxoviridae
Genus – Alphainfluenzevirus
Subtypes based on haemagglutinin (H) and neuraminidase (N)
The flu virus appears naturally among birds
Wild migratory birds such as ducks, geese, gulls and shorebirds are natural carriers of the virus, but are resistant to severe infection from the virus
Direct infection can occur fromexposure to saliva, mucous, or faeces from infected birds
18 different H antigens (H1 to H18) –> Haemagglutinin – recognized/bind to host
- 11 different N antigens (N1 to N11) –> Neuraminidase – release of new viral particles
Avian influenza A viruses are classified into
low pathogenicity avian influenza (LPAI) A viruses
highly pathogenic avian influenza (HPAI) A viruses
The categories refer to the molecular characteristics of a virus and its ability to cause disease and mortality in chickens in a laboratory setting
how is avian influenza diagnosed and treated?
Diagnosis
based on history, clinical signs and post-mortem
conclusive diagnosis PHA
Treatment and Control
no readily available treatment
most countries have a culling policy of affected birds
biosecurity is paramount to preventing Avian Influenza
what is trichomonas in birds?
Protozoan parasite Trichomonas gallinae
- only pathogenic trichomonad in birds
- yellow deposits and lesions on oral cavity
- malnutrition
Spread via unwashed bird feeders
- contaminated water and food
- sharing of feeding stations
It also infects house sparrows and yellowhammers
- does not pass to humans
PREVENTION
- allow feeders to dry out
- Trichomonas can’t survive periods outside
What is eimeria in birds?
Causes coccidiosis in poultry & goats
- many different species
- Eimeria tenella is highly pathogenic
Major pathogen of intensively reared poultry
Economically significant
- ~30 billion chickens worldwide
- UK cost of disease is ~£38 million/year
Faecal-oral transmission
- introduced on farmers boots or new infected stock
wha tis eimeria and coccidiosis?
Intracellular protist – apicomplexan parasite
- plastid = apicoplast
Replicates in intestinal epithelial cells
- causes tissue damage & sometime bloody diarrhoea
- malabsorption of nutrients
- death in severe cases
Ubiquitous parasite but pathology depends on level of infection
parasites – number, pathogenicity, promote immunity in host
host – susceptibility, protection by anticoccidials, regenerate from parasite damage
environment – intensive rearing, hygiene, drug prophylaxis
what are the controls for eimeria an coccidiosis?
Chemotherapy
- anti-coccidial drugs available but emerging drug resistance
Live attenuated vaccine available
- others in development
Housing
- warm, humid, crowded, deep litter encourage spread of parasite
- ensure chickens not standing in their litter
Management
- free range
