Carnivore Virology

Question 1

Describe the efficacy of deliving rabies vaccine to duodenal mucosa in Gray foxes (Urocyon cinereoargenteus).

Discuss the advantages of preserving rabies vaccine by vaporization.

Answer 1

Preserved, non-preserved, and alginate encapsulated vaccine was delivered to duodenal mucosa via endoscopy

• Alginate encapsulated vaccine failed to stimulate immune responses
• Live attenuated RABV Preserved by Vaporization & RABV without vaporizaiton preservation both produced sufficient immune responses
• No viral shedding in saliva or blood was documented
• No nerve tissue or CSF virus was isolated at necropsy either

Vaporization

• foam-drying technique PBV effectively stabilizes RABV at ambient temperatures for 15 months
• can induce RABV-neutralizing antibodies when delivered IM
• advantage - ability to micronize biologics, which allows for needle-free and traditional pharmaceutical delivery (intradermal microneedle patches, intranasal inhaler, dissolvable oral gels, or gastric capsules)

Reference: AJVR 2017 78(6) 752-756. Assessment of the immunogenicity of rabies vaccine preserved by vaporization and delivered to the duodenal mucosa of gray foxes (Urocyon cinereoargenteus)

Question 2

Describe the infection of SARS-CoV-2 in wild animals.

What hosts have been documented?

How is it transmitted?

How is it diagnosed?

What treatments are available?

How is it prevented?

What disinfectants are effective?

Answer 2

Range of hosts
* NHP and carnivores main spillover hosts in first year
* Farmed mink
* Feral boars, red foxes, jackals had seroconversion
* WTD seroconverted and had DNA in LN

Transmission routes and clinical signs in animals
* Aerosol main route, fomite contamination role low
* Animals generally expressing milder signs than humans
* URT (sinusitis, tracheitis), LRT (pneumonia), and SI tract (diarrhea)
* Virus can be found in many organs, including brain
* Mortality rate very low, even zero in most species
* Except African monkey

Diagnostic
Direct
- Sample nasal, tracheal, rectal, fecal swabs
- PCR
– rtPCR is gold standard
– some kits may lose efficacy with variants
– rtPCR targeting nucleocapsid, envelop should be used as those are most stable sequences
– Genomic analysis paramount (online databases exist)
- Antigenic analysis
– Commercial tests can be used on nasal, trachea, rectal, fecal swabs to detect SARS-Cov02 antigen
– 98% specific, but sensitivity may be low (30-88%) depending on viral load
– Low predictive value in zoo setting
Indirect
- Serology
– Triggers both cellular and humoral immunity
– First Ig (usually IgM) in first week post-infection, then IgG, IgA rise and last for several months
– In rhesus, reinfection at 28 and 35 days was protective enough to greatly decrease signs
– ELISA or LIPS assays looking for antibody targeting N or S subunits

Treatment
- Supportive care
– NSAID, mucolytic and fluid/vitamin (D)
– Glucocorticoids can be used
- Antimicrobials
– Avoid secondary infections
– Some have in vitro properties vs SARS-Cov-2: azithromycin, hydroxychloroquine, ivermectin, itraconazole
- Monoclonal antibody
– It has been proven than human monoclonal antibodies can protect animals
– mAbs has been used in a gorilla
– Innocuity was good, efficiency in viral load decrease could not be determined
– Should be given early in infection to be most effective

Prevention
- Viral circulation
– Level of viral circulation in zoo
– Human screening, vaccination, biosafety, temp monitors, auto-tests
– Environmental monitoring – sewers
- Best practice and PPE
– Reducing indoor time with animals, increasing distance, increasing air flow
– Surgical masks or N95/N99
– Wear gloves with food
– Adjust medical training behaviors

Disinfection methods
- Very resistant as it is enveloped
Inactivated by heat after 10min above 56C or 5 min at 70C
- Barely impaired by freezing
- UV light can inactivate virus on surfaces or aerosols (sunlight over 5 min)
- All anthropogenic items should be disinfected or kept for a week before used as enrichment
- Effective compounds: alcohol >70% (30 sec), sodium hypochlorite >0.1% (1min), hydrogen peroxide >0.5% (1min)
- Other disinfectants can be used, but exposure time 5-10min

Vaccination
- Staff vaccines reduce risk of passage to animal
- Human RNA vaccines successfully used in NHP
- Vet vaccines: based on recombinant antigen (S) with adjuvants to elicit antibody response in carnivores
- Serology: carnivores show high titers, NHPS reach weak titers after booster
- Use killed or recombinant in wild species to avoid risk of recombination events