Lab 3.6

Question 1

Feline calicivirus clinical signs for virulent systemic form

Answer 1

-mild upper respiratory signs
-conjunctivitis

-severe respiratory signs
-anorexia
-drooling
-diarrhea

-death

Question 2

Feline calicivirus post mortem findings for virulent systemic form

Answer 2

• Cutaneous ulceration on the ears, face
• Subcutaneous edema of the face and limbs

Oral cavity:
* Erosion and ulceration of the tongue and hard palate

Thorax:
* Bronchointerstitial pneumonia

Question 3

how does the virulent systemic form of feline calicivirus arise? who can it target?

Answer 3

• Rare manifestation, results from viral mutation, pathogenesis is poorly understood
• Highly contagious, rapidly fatal, affects juvenile and adult populations both vaccinated and unvaccinated

Question 4

what samples should we send to the lab to test for calicivirus antemortem?

Answer 4

○ Swabs: nasal, conjunctival, pharyngeal

Question 5

best testing modality for feline calicivirus

Answer 5

○ PCR most common for antigen detection*

Question 6

What are the three possible causes for antibody to be present?

Answer 6

1. Current active infection
2. Previous infection
3. Previous vaccination

Question 7

Can any test differentiate between typical calicivirus infection and atypical virulent systemic calicivirus?

Answer 7

No

Question 8

differential diagnoses for respiratory illness in cats (viral)

Answer 8

• Feline calicivirus*
• Feline herpesvirus 1 / feline viral rhinotracheitis
• Feline panleukopenia
• SARS Co-V-2

Question 9

Suggestions to a shelter to control/prevent viral calicivirus (and other viral diseases)

Answer 9

• Quarantine new arrivals
• Vaccinate upon arrival
• Reduce stocking density if possible
• Improve hygiene → Recovered cats can shed for a long time and can be spread by BOTH aerosol transmission or fomites
• Isolate/quarantine sick animals

Question 10

challenges with vaccinations for feline calicivirus

Answer 10

• Like many RNA viruses, there is variation between strains of feline calicivirus
• Creates a challenge with vaccination
• Vaccines are either single or dual strain
• Vaccination does not prevent infection, prevent carrier state, or protect against virulent strains

Question 11

SCENARIO:
● 400 sow farrow-to-finish farm operation
● Began six weeks ago, some pigs went off feed, elevated temperatures which lasted seven to ten days
● More recently, a few pigs are coughing with increased respiratory rates
○ Pigs of all ages affected
○ Non-responsive to a course of antibiotics
○ Pigs were previously vaccinated against Mycoplasma hyopneumoniae

There has also been reproductive failure
1. Premature farrowing of live piglets(early deliveries)
2. Late term abortion
3. Stillborn and weak piglets causing increased pre-weaning mortality
4. Failure to conceive and maintain pregnancy (early pregnancy loss)

> > Piglets are coughing, farmer describes a “thumping” sound

> > 2 affected pigs have recently died

What are your differentials?

Answer 11

1. PRRSV*
2. Swine parvovirus
3. Porcine circovirus 2
4. inclusion body rhinitis
5. swine influenza

Question 12

Symptoms of porcine reproductive and respiratory syndrome virus (PRRSV)

Answer 12

● Stillbirths, mummified fetuses, premature farrowing,
● Respiratory thumping, anorexia

Question 13

most economically important disease affecting swine producers:

Answer 13

PRRSV

Question 14

how does PRRSV spread through a herd? what changes this? how is the virus maintained in the herd?

Answer 14

○ In a naive herd: infection spreads slowly throughout herd causing clinical picture as in this case with variable degrees of disease and death
○ In an endemically infected herd: infection is often subclinical
○ Virus is maintained in a population indefinitely by asymptomatic swine who shed the virus for up to 3-5 months

Question 15

what does PRRSV predispose infected animals to?

Answer 15

Virus destroys pulmonary alveolar macrophages → risk of secondary bacterial pneumonia

Question 16

what herds are most at risk for losses from PRRSV?

Answer 16

Greatest losses are seen in herds experiencing other concurrent infections

Question 17

how is PRRSV transmitted?

Answer 17

● Virus transmission is by direct contact, airborne and via semen

Question 18

can PRRSV spread in the winter?

Answer 18

Virus survives at low temperatures, so epidemic spread is quite efficient in the winter months

Question 19

what does PRRSV look like on post mortem?

Answer 19

Lungs: Red, rubbery, do not collapse→ consistent with interstitial pneumonia

Question 20

How should we test for PRRSV antemortem?

Answer 20

○ PCR on serum, oral fluids, semen
○ Testing of aborted fetuses is of less diagnostic utility

Question 21

How should we test for PRRSV post mortem?

Answer 21

○ PCR on lung and/or lymphoid tissue
○ Immunohistochemistry on FFPE tissue:
low specificity and need to submit multiple pieces of lung

Question 22

How does PRRS infection persist on an individual farm?

Answer 22

• Persistent infection of individual animals (specific numbers NOT important)
• Continual outside additions to farm population

Question 23

What are the long-term consequences for a herd infected with PRRSV?

Answer 23

● Severity of PRRS within a herd long term is variable: no clinical disease, continued clinical disease and production losses

● Secondary opportunistic infections:
* e.g. bacteria like Hemophilus parasuis, Streptococcus suis, Mycoplasma hyponeumoniae

● Coinfection with PCV-2 can cause more severe lesions
* More severe clinical presentations and pulmonary lesions compared to either infection alone

Question 24

Control of PRRS; what can we try, and how can we create a PRRS stable farm?

Answer 24

● No single effective control strategy
● Often goal is to create a “PRRS stable” farm through intentional exposure of entire stock (before breeding)
● Vaccination
● Elimination on individual farm very difficult

Question 25

is vaccination for PRRSV effective?

Answer 25

commercial modified live PRRSV vaccine (IM) and inactivated vaccines exist; efficacy variable against circulating strains

Question 26

why is elimination of PRRSV on an individual farm tough?

Answer 26

Elimination on individual farm very difficult due to long shedding period, asymptomatic carriers, and extreme biosecurity measures required for maintenance (including massive initial depopulation)