Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Animal Health*4230 > Lecture 9: Infectious Disease > Flashcards

Lecture 9: Infectious Disease Flashcards

1
Q

What is the principles of infectious disease control?

A

-Disease: complex interactions, is the result of a combination of risk factors
-Biology of the individual and biology of the interaction of the individuals (herd effect) and the agent and environment (lead to increase in infection)
-Control of disease is based on management of risk factors that may change overtime

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are principles of infectious disease control?

A
  1. ELIMINATE at herd, regional or national level
  2. PREVENT entry into a herd or country that doesn’t have disease (foot and mouth disease spreads really easily)
  3. CONTROL to keep it a manageable level in a herd or country (restrictions)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is Bovine Viral Diarrhea Virus?

A

-two genotypes of the BVD virus:
-Type 1 and type 2 (increased mortality)
-Type 2 was isolated in acute clinical cases from CA and USA in the mid 1990’s-Both types are capable of causing sever disease
-There is some, but incomplete immunologic cross-protection b/w genotypes
-Therefore most vaccines contain both type 1 and 2 strains
-FOr BVDV the biotype is defined by the growth characteristics of the virus in cell culture
1. Cytopathic (CV) strains kill cells in culture
2. Noncytopathic (NCV) strains do not kill cells in cutie (associated with PI animals)
-Biotype doesn’t relate to acute virulence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

TRUE OR FALSE? In a persistent BVD infection, an infection of the fetus with non-cytopathic BVDV <125d of gestation can result in the production of a persistently infected (PI) calf?

A

TRUE
-virus not recognized as non-self
-Virus shedding is continuous for most of the animals life (good news) most don’t survive to adulthood (bad news) if they do they are a continuous source of infection for the herd

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

TRUE OR FLASE? PI animals are the main reservoir of BVDV n the bovine population?

A

-TRUE mostly < 2years (many PI will develop mucosal disease and die by then)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is transmission for BVD?

A

-Spreads by direct contact with shedder
-Mainly though viral shedding in saliva, music, semen (manure)
-In urtero (leads to PI)
Shedding:
-PI (large # and content)
-Acute, virulent type 2 (shorter duration)
-Other acutely ill animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where is BVDV present and what systems does it attack? not *

A

-upper resp. tract and lymphoid tissues are the sites of virus replication (destruction of lymphoid tissue –> immune suppression)
-Viremia (reproduction of virus) starts 3d to 8-10d after infection but duration may be as short as 2-3d for some cattle
-70-90% of infections are subclinical (no overt disease, seroconversion ie successful immune response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are risk factors for BVD disease?

A
  1. Herd has a history of inadequate immunization (no MLV used or failure to give primary series of killed vaccine
  2. Animals are purchased (screening tests for BVD not performed new purchases are not isolated)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are BVD clinical presentations?
Not *

A

Mucosal disease
-Only in PI’s

Per-Acute BVD
-High fever
-Off feed
-Diarrhea (with blood)
-Severe platelet depression and death
-Death within 48 hours

Acute BVD
-Fever, diarrhea, pneumonia, abortion

Immune suppression and secondary pneumonia

BVD- associated reproductive problems, abortions and congenital anomalies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is mucosal disease? not *

A

-PI animals only, usually < 2yrs
-Morbidity low (few animals) BUT case fatality ~100%
-Fever, oral erosions
-Diarrhea with blood sometimes
-Die in 5-7d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

TRUE OR FLASE: BVD is a congenital disease that causes cerebellar hypoplasia and calfs that are blind or cataracts, small unthrifty

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does BVDV affect reproduction and the economic cost for the producer?

A

Reproductive
-Best available vaccination ~80-90% effective at fetal protection
-Reproductive problems can persist despite an aggressive immunization program
-A PI dam will always produce a PI calf

Economic
-Very small percentage of all BVDV infections are clinical
-Acute disease of highly pathogenic strain may kill 25-40% of infected animals and cause sever milk depression and weight loss (Bb not eating)
-Abortions
-Smoldering reproductive problems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the treatment for BVDV?
not *

A

-No specific treatment
-Supportive care and antibiotics for secondary infections in acute BVD
-PI calves generally die of mucosal disease or should be euthanized as a source of virus to the herd

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are some control points for BVD?

A

-Adequate, correctly implemented vaccination program
-MLV for fetal protection
-Intros: no nose-nose or manger/waterer contact for 3 weeks
-Test for BVD-PI in quarantine
-Vaccinate purchases in quarantine
-Isolation of animals with diarrhea and respiratory disease
-Eliminating PI’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is salmonellosis?

A

-Infection <–> Shedding <–> Disease
-1. Sporadic and 2. epidemic associated with parturient disease and “stress”
-Prevention of introduction unlikely (rodent/wild life control) sheds in feces and cows consume
-Following outbreak infection becomes endemic
-Cows = weeks-months even years
-Farm=years
-Many strains of various virulence (host-adapted vs non-host adapted (other species)
-Infects any species with an intestinal tract
-Organism is prevalent and disease is opportunistic (only affects animals immunosuppressed)
-Zoonotic (like Dublin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are clinical signs for most salmonella species? not *

A

-Diarrhea (bloody, fibrin/inflammation strings commonly in fresh cows)
-Fever
-Off-fed
-Drop in milk
-Abortions
-Calf septicemia, diarrhea and death

17
Q

What are clinical sings for salmonella Dublin?

A

-Emerging disease in ON
-Causes respiratory sings ans septicemia
-Was diagnosed in dairy herds in northern USA and in Quebec on veal farms
-Cases now seen on ON dairy farms (7% positive rapid spread in pop)

18
Q

What is the transmission of salmonellosis?

A

-Fecal» oral/nasal/urine (septicemic)
-Infected not clinical septicaemia not clinical ie not always showing signs but shedding
-Clinical animals shed up to 10^9/g manure
-Rumen VFA’s protective
-Infectious does in healthy adults about 10^9
-Infectious dose in off-feed cows about 10^2-10^3
-Opportunist of calves and peri-partum cows

19
Q

What are critical control point for salmonellosis?

A

-INTRA-Herd biosecurity (restrictions movement of manure/fomites) if do buy into herd
-Separate hospital and calving pens
-Rational antibiotic use
-Separation of calves and cows in outbreak
-NOT vaccination

20
Q

What is Johne’s Disease?

A

-Caused by mycobacterium avian, subsp. paratuberculosis (MAP)
-Thick walled bacteria very resistant to environmental destruction
-Can infect cattle, deer, bison, sheep and goats
-VERY slow growing (won’t see clinical signs for 1-2year after infection)
-Mainly in ileum (distal small intestine)

21
Q

What is the transmission for Johne’s disease?

A

Transmission = mostly fecal-oral
-Organism shed in manure
-Contaminate feed, pasture, water, calving pen (oral ingestion of bacteria by young calves)
-In advanced stages of disease organism may pass from dam to fetus in utero OR in colostrum (very rare usually fecal/oral)
-Generally thought to infect calves < 6 m old… highest risk is newborns… but evidence that older calves can be infected (increased risk newborns)

22
Q

What is the epidemiology of Johne’s Disease?

A

-Animals exposed as adults may become infected but don’t know infective dose
-Many animals will never develop clinical disease (only 5-10% develop signs)
-Clinical disease onset from 18m to 6+year of age (until show sings)
-Age of onset of disease may depend on level of exposure as a calf
-Bacteria may survive years on pasture

23
Q

What is the pathology of Johne’s Disease?

A

-Intestines become thickened with bacteria and inflammatory cells
-Malabsorptive diarrhea

24
Q

What are clinical signs of Johne’s Disease?

A

-Episodes of profuse diarrhea, weight loss but good appetite, no blood or fever
-Often in fresh cows
-Diarrhea eventually becomes chronic
-Cows usually culled before death
-Subclinical infection appears to reduce milk production

25
Q

What is the treatment and control for Johne’s Disease? Not *

A

-No effective treatment
-Goal to remove infected animals (selective slaughter) and prevent new infections
-Diagnostic tests are very important
-Blood or milk-ELISA for serum Ab’s to MAP
-Sensitivity = 15-45%
-Specificity =99.2% for subclinical
-Milk ELISA is useful to estimate herd prevalence
-Fecal culture of individuals or pooled samples
-Expensive and takes up to 3 months
-Better sensitivity but still ~ 40-60%
-Direct PCR on feces
-Faster results on decal samples but sensitivity is still low

26
Q

What are some biosecurity steps for Johne’s Disease?

A

-Don’t allow calves to eat manure
-Basic control measures will help prevent salmonellosis, calf scours
-Risk assessment and management plan (RAMP)

27
Q

How does Johne’s disease relate to human health? not *

A

-Johne’s disease and Crohn’s disease in ppl are clinically and pathologically similar
-MAP has been detected with increased frequency in tissues from Crohn’s patients than healthy ppl or patients with other IBD
-Not all Crohn’s patients have MAP (probable role of genetic and other host factors, MAP might be factor in only a subset of patients if any)
-MAP in Crohn’s patients may not be viable, not clear if the organism is cause or eggiest (opportunist) of lesions in ppl
-MAP has been dented in raw milk, meat, water, sewage, wildlife
-MAP may survive pasteurization -controversial

28
Q

What are the critical control points for John’s Disease?

A

-Prevent manure movement from adults to calves
-Identification and accelerated removal of infected (shedding) individuals
-Clean maternity pens
-Immediate calf removal
-Non-pooled colostrum, not from infected cows
-Do not feed cows feed refusals to young heifers
-Avoid manure spreading in same heat as forage harvest
The following Not *
-JD is complicated (V slow to develop clinical disease, V hard to diagnose specially in young animals, farmers believe it is difficult to control)

29
Q

What are some biosecurity options for Johne’s disease?

A

-Programs for infectious disease control that prevent or reduce the introduction or movement of disease on an operation
1. Into of pathogens onto farm
2. Movement of pathogens within farm
3. Transfer of pathogens to humans

30
Q

What are some important principles for infectious disease? not *

A

-Dairy herds tend NOT to take ALL PERILS approach
-Decide what your trying to control/prevent
-Keep diseases you don’t have OUT and minimize spread of diseases you do have (endemic)
-Emphasize the need for INTRA-hred biosecurity
-Basic practices will reduce risk of numerous disease (JD control will help with calf diarrhea)

31
Q

What is ‘A’ list for biosecurity basics? Not *

A
  1. Correctly implemented vaccination program
  2. Milking time hygiene
  3. Restricted manure movement & handling
  4. Isolation of sick animals
  5. Separate sick and maternity pens
  6. Prompt calf removal from cow environment
  7. No colostrum pooling
  8. Remote headstock, cull cow, and surplus calf collection
  9. Disease monitoring program
32
Q

What is ‘B’ list for biosecurity basics? not *

A
  1. selective sourcing of purchases (buyer beware)
  2. Max knowledge of sources and animals being purchased (small numbers)
  3. Pre-into testing
  4. Milk replacer instead of milk/waste milk
33
Q

What are the take home messages from this lecture?

A

-Infectious diseases are common (BVD, Salmonella, Johne’s)
-Biosecurity is critical
-Prevent disease entry onto the farm if don’t have it
-Min risk of disease w/in the herd if you have it

Animal Health*4230 (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions