Anatomic Pathology Readings 11-14 Flashcards
How can you get a cDNA (copy of DNA) for PCR of an RNA infectious agent?
Use the enzyme “reverse transcriptase” to promote synthesis of DNA from the RNA template = cDNA (copy of the DNA)
How does PCR work?
- Primers (nucleotides) compliment intended target DNA and are added to reagents
- heated to separate DNA to two strands
- cooled to allow primers to bind to DNA
- heated again
- 25-40 cycles
- PCR products (amplicons) read by gel electrophoresis
Advantages of molecular approaches:
- Faster and no need for special media
- Diagnose organisms hard/slow to grow or ones that cannot be cultured
- Detect evidence of infection before Ab response
- Clarify Ab + due to infection or maternal Ab
- Document latent infections or carriers
- Diff btwn pathogenic and non-path or vaccinal isolates
- Retrospective analysis and characterization of zoonotic infection
PCR can help dx organisms that cannot be cultured like:
many viruses some mycoplama (haemobart)
PCR also good with disease organisms that grow slowly for example:
mycobacteria
Good examples of diseases that historically have required seroconversion but now can be diagnosed via molecular assays: name 2
RMSF (rocky mountain spotted fever)
Leptospira
Examples of a PCR clarifying infectious dz or maternal Ab
FIV (otherwise can’t tell!)
T/F: PCR and RFLP (Restriction fragment length polymorphism) can help select appropriate antimicrobial therapy.
true
List Koch’s 3 postulates:
- Agent found in every case of the disease
- Agent was not found in other diseases
- Agent can be isolated and cultured and cause disease in a new host
(4. Agent could be isolated from the experimentally inoculated host)
Why use Koch’s postulates - what do they mean?
They show that a given agent was the cause of clinical disease if the postulates were satisfied
What’s considered an additional point of proof of infect dz:
If an agent can be isolated from experimentally inocculated host
When trying to find a cause for a disease, what is the most important first question for a clinician when they have detected an infectious agent?
Is it is likely that the infectious organism is truly responsible for clinical disease or other abnormalities?
Give an example where the PCR-positive blood sample doesn’t guarantee an infection.
Hemobartonella = IMHA
Hemobartonella can cause IMHA but IMHA can be caused by other causes
Are there known pathognomomic or typical gross lesions for anesthetic-associated death (AAD)?
no!
Over half of cases with natural disease had ____ lesions which included:
pulmonary:
- Aleurostrongylus abstrusus
- pneumonia
- acute aspiration pneumonia
Pulmonary dz was the most common lesion tied to AAD, which two wereafter that?
-heart disease (2 HCM; 4 lymphocytic myocarditis)
-systemic (Panleukopenia; Toxoplasmosis)
(also CNS disease causing one death; noting hepatic lesions in 3 cases)
What is the connection between renal disease and anesthetic-associated death (AAD)?
Of the 54 cases of AAD death, none had gross or histo evidence of renal dz! (no connection)
What is the life cycle of Aleurostrongylus abstrusus
- Adult worms in terminal bronchioles
- Eggs are laid by females, with L1 coughed up and excreted
- L1 exits in the feces to intermediate host: snail, slug
- L1 matures to L3 in intermediate host and then either eaten by cat (DH) or paratenic host then to the definitive host
t/f cats can never eliminate A. abstrusus on their own?
False! they will eliminate it after 5months and cannot be re-infected
What is the gold stnd diagnosis of A. abstrusus
Baerman fecal exam
Aleurostrongylus abstrusus infections results in: (2)
- Granulomatous pneumonia
- Hypertrophy and hyperplasia of tunica muscularis in the pulmonary artery = pulmonary hypertension (can persist for up to a year)
What parasite other than Aleurostrongylus abstrusus can cause pulmonary hypertension in cats?
Dirofilaria immitis
Why do cats die from anesthesia with pulmonary hypertension?
There is a decrease in gas exchange -> less blood back to LA -> LV
There were cases with lymphocytic myocarditis- etiology?
Toxoplasma
Possibly Bartonella henselae or a cardiomyopathy
Why can’t you rule out toxoplasma with a negative IHC?
It only takes a few of tiny T gondii tachyzooited to incite sign inflammation
Can you detect a mechanical causes of death eg. soft palate occlusion or improper ET-tube intubation on PM?
no
Can you detect respiratory acidosis secondary to hypoventilation on PM?
no
Can you detect heart conduction failure on PM?
no
What should you sample for histopath on stillborn, or neonatal death? (6 + 1 general)
Placenta Liver Kidney Lung Heart Brain Anything specific
What should you sample fresh* for virology and bacteriology?
same as histo except also sample spleen but don't sample heart and brain (Placenta Liver Kidney Lung Spleen Anything specific)
Who’s serum do you sample in fetal necropsy?
Dam and fetus
What is most critical tissue to obtain on fetal necropsy:
Placenta! may have more info than fetus itself
In the case of neonatal death, do what before opening up fetus?
- record wt, measure crown to rump, check for hair growth and texture, check for teeth (teeth = close to term)
- rinse fetus and fetal membrane and put on wet table to examine
In the case of neonatal death, specifically check for these before opening up animal:
- congenital defects (e.g. VSD)
- evidence of redness, swelling, improper mobility= fx
- umbilicus for swelling (hernia)
In the case of neonatal death, what should you do once cavities are open:
Collect samples:
- virology/bact (1cm+)
- histo- in formalin (<0.5cm)
- Sample of blood & stomach contents in a red top tube with new needles
When examining placenta on dog, if you see dark red-green band what do you conclude?
It’s normal! marginal hematoma on zonary band (zonary placenta) (pale brown and smaller in a cat)
Cats placenta differs from dog placentas how?
The marginal hematoma is more narrow with less distinction and is pale brown
It’s important to do this with placenta to check of evidence of inflammatory cells and bacterial organisms:
Take an impression smear of the chorioallantois
What organism loves placenta?
Brucella organisms
What if you see a red tinge on internal organs of fetuses?
incidental (unless well demarcated areas of obvious hemorrhage and/or edema are present)
What about a clear yellow or red fluid in body cavities of fetuses?
incidental
What if you see clotted blood within cavities in a fetus?
This is not normal- may indicate trauma
Fetal mummification (dry, shrunken, wrinkled) can mean what?
Non-sepcific. Can point to a viral cause or many other causes in utero
What is the cause/name of a fetus which is just a bag of bones with reddish brown uterine fluid?
This is fetal maceration and is commonly due to bacterial infection (specific to bateria*)
What is an example of an incidental congenital defect?
hydrancephaly (brain’s cerebral hemispheres are absent)
unilateral renal agenesis
What is the most common cause of viral abortion in neonatal dogs?
herpes!
Clinical signs and PM findings with Herpes
- Sudden death, lethargy, excessive crying
- PM: multi organ hemorrhage (kidney, lungs, liver most obvious)
t/f herpes likes warm temp to grow?
FALSE! Herpes virus is optimized at lower temps
You can confirm herpes infection with what tests?
histo and PCR
How does having herpes affect pregnancy in cats?
Abortion is rare in cats with herpes. It is mostly tied as a secondary cause because of respiratory disease in the queen
BUT kittens can have neonatal death due to herpes
List other differentials for sporadic abortions and neonatal deaths in dogs, other than the most common (herpes virus)
CPV-1 (canine parvovirus-1)
CDV (canine distemper virus) -> rare
CAV-1 (canine adenovirus-1) -> not typical; pneumonia in pups
BTV (bluetongue virus)
(can be secondary to maternal morbidity or due to direct infection)
Ddx viral abortion and neonatal death in cats:
- FeLV
- FPLV (feline panleukopenia virus/parvo)
- FIV
- Feline coronavirus
- FCaV (feline calicivirus)
2 most common bacterial neonatal death in dogs:
Brucella canis (take more than 48 hours to culture)
Streptococcus spp
Others: salmonella, campylobacter, leptospira, e.coli
Protozoal causes for abortion, stillbirth, neonatal death dogs and cats:
Toxoplasma
Neospora
(dogs and cats are DH for both)
This virus is assoc with fatal pneumonia in puppies <4wks
CAV-1
How do you tell if there was trauma with dystocia?
regional hemorrhage or edema
+/- fractures
What makes you think infanticide?
hemorrhage in brain and broken skull
seroconversion detects what?
active immune response 10-14days post inital challenge
Serology is best used when?
Serology is best used to monitor for active infections in a group of cattle, rather than specific disease in a single animal
“if animal test +, it has dz” =
pos predictive value
VNT vs ELISA with serology
ELISA only tells you that Ab binds to Ag- may bind to part of virus that’s not nec for infection
VNT- demonstrates what amnts of Ab will neutralize the virus
serology detection for bacteria: egs
varies: ELISA, CF, agglutination, leukotoxin inhibition
LN vs antileukotoxin
LN measures fxn Ab which interfer with toxin b/c antileukotoxin binds to any leukotoxin (LN better indicator of + predictive immunity)
problem with VI at cellular level
not all cells show cytopathy with certain dz’s (non-cyto BVDV)
main disadv of VI
- takes 2 wks before actual -
- cells needed may be hard to get
- can’t find new or emerging viruses
use EM for
enteric and sometimes resp viruses
disadv of bacterial isolation
- tech has to pick correct colony
- bacteria present are all N in resp tract
- antibiotic therapy can = negative culture
direct vs indirect FA
direct detects Ag
disav of FA
dye won’t stay long without breaking down so can’t have another lab consult (IHC helps with this problem)
limitation of IHC
lack of specificity to monoclonal Ab, esp. newly recogn agents
IHC vs in-situ hybridization
same but doing IHC in-situ is potentially more sensitive and can identify low numbers of copies of the infectious agent nucleic acid
RT-PCR also called
q (quantitative) PCR b/c can show if large load of agent if fluor earlier on
these study pathogenesis, host-agent interaction and type animal pathogens (req. strict QC)
microarrays
should use PCR on secretions in the water?
no- meaningless
PCR vs. IHC, in-situ hybrid which is more accurate
IHC, in-situ and PCR as adjunct
Definition of stillborn
Born dead at full term
Definition of neonatal death
Death within the first 3 weeks after birth
