Viral Diseases of Wildlife and Pocket Pets, Lecture 19

What is the most important viral disease of deer in the US?

Epizootic Hemorrhagic Disease

What two closely related orbiviruses both cause hemorrhagic disease in deer and have indistinguishable clinical signs?

Epizootic hemorrhagic disease virus and Bluetongue virus

What parent virus do Epizootic hemorrhagic disease virus and Bluetongue virus belong to?

Reoviridae

What orbivirus is a foreign animal disease?

African Horse Sickness

How are Epizootic hemorrhagic disease and bluetongue viruses transmitted?

• Culicoides sonorensis is the confirmed vector for bluetongue and EHD

• Culicoides insignis confirmed vector of bluetongue in SE USA

• transmitted July through November

What are the wildlife hosts if Epizootic hemorrhagic disease and bluetongue?

• white tailed deer

• mule deer

• pronghorn

• bighorn sheep

What is the distribution of epizootic hemorrhagic disease and bluetongue?

• widely distributed in temperate and tropical climates worldwide

• hemorrhagic disease occurs only in Cervids

• 3 serotypes of EHDV, many of BTV

The following clinical signs match which viruses;

• cause damage to small blood vessels (replicate in lymphoreticular system) resulting in fluid loss, hemorrhage, and tissue damage

• sudden death to chronic disease

• pyrexia, depressoin

• hyperemia (reddenning of peri ocular skin and nostrils)

• swelling of head and neck due to vascular damage and hemorrhage

• ataxia, blindness, loss of fear

• sick and dead animals oftten found near water

• sloughing of hoof, antlers

• some deer survive infection

Epizootic hemorrhagic disease virus and bluetongue virus

The following gross pathology matches which virus:

• petechial hemorhhages

• pulmonary edema

• swelling of tongue, mucosal surfaces, head, and neck

• pericardial effusion

• splenomegaly

• hyperemia or hemorrhage of forestomach

epidemic hemorrhagic disease and bluetongue

How do we diagnose epidemic hemorrhagic disease and bluetongue?

• histopathology (non-specific)

• RT-PCR

• virus isolation

• serology

• fluorescent antibody test

• immunohistochemistry

Are vaccines available for epidemic hemorrhagic disease and bluetongue viruses?

Vaccines are available for farm animals, but not approved for zoo animals or wildlife

What is Chronic Wasting Disease?

Transmissible Spongiform Encephalopathy

The following characteristics match which disease:

• brain degeneration with vacuolation

• long incubation period (>2.5 years)

• cause is believed to be a unique infectious agent called a prion which is an infectious protein

• infectivity very hard to inactivate

• invariably fatal

• transmitted by meat products, indirect contact and iatrogenic (use of needles)

Transmissible Spongiform Encephalopathy (Chronic Wasting Disease)

How is Chronic Wasting Disease transmitted?

• transmission method is not known, but maybe associated with grazing contaminated pastures

• prion material has been detected in urine and horizontal transmission through infected placenta may be possible

How can we diagnose Chronic Wasting Disease?

• prions can be detected ante mortem in lymph nodes when deer clinically affected and also lymphoid tissues in rectum

• lymphoid tissue examination is about 60% as sensitive as brain histopathology

What is the clinical presentation of chronic wasting disease?

one of progressive loss of condition

Rabies and Canine Distemper affect which wildlife species (that we discussed in lecture)?

• raccoon

• skunk

• gray fox

• red fox

• coyote

Other species for distemper:

• big cats (lions and tigers)

• pandas

• seals

• ferrets

• raccoons

How is rabies transmitted?

• bite or scratch of a rabid animal

• aerosol transmission in bat caves

• contamination of mucous membranes

What is the incubation period of rabies?

1-3 months, but can range from days to years

Discuss the pathogenesis of rabies.

• virus replicates in peripheral nerves or non nervous tissue such as muscle

• virus then moves to the central nervous brain system via the spinal cord to the brain

Discuss the clinical course of rabies virus.

• infection (bite) occurs

• incubation <10 days to several months

• prodromal period 1-2 days

• acute neurological period 1-10 days

• death — paralysis leads to respiratory, cardiac failure

Describe the prodromal period of rabies virus.

• early symptoms and signs of an illness that precede the characteristic manifestations of th acute, fully developed illness

• viral shedding occurs despite lack of obvious clinical signs

Describe the acute neurological period of rabies virus.

• obvious clinical signs: excitable, hyperesthesia, agitation, aggression, head tilt, head pressing, strange phonation, drooling

• active viral shedding

• paralytic hase may follow agressive phase, or occur directly after prodromal period with no excitation (ataxia, ascending flaccid paralysis, lethargy, prostration)

• wildlife lose fear of humans and domestic animals

How do we control rabies virus?

fish paste based recombinant oral vaccine (Raboral V-RG)

Explain what genes are involved in the fish paste based recombinant oral vaccine for rabies.

the gene for rabies G-protein has been inserted into the vaccinia virus TK gene

The vaccinia component of the rabies recombinant vaccine allows for what?

replication in mammal cells (back of the throat in the case of the fish paste based recombinant oral vaccine)

What is the most common source of human rabies in the United States?

bats

How is canine distemper virus transmitted among wildlife?

direct contact, aerosol droplets

Describe the pathogenesis of canine distemper virus in wildlife.

• virus is shed from all excretions and secretions

• virus replicates in lymphatic tissue associated with the respiratory tract mucosa

• subsequent viremia, wide spread infection of epithelial tissue

• most lymphtic tissue becomes infected, as well as CNS

What are clinical signs of Canine Distemper Virus?

• respiratory distress

• fever

• anorexia

• serous nasal discharge and mucopurulent ocular discharge

• weight loss and diarrhea

• hyperkeratosis of nasal planum and footpads

• CNS signs (localized twitching, ataxia, convulsions, salivation and chewing movement of the jaws, paddling movements of the legs, urination and defecation)

Which virus is used in the canine distemper recombinant vaccine for black footed ferrets?

canarypox

When was smallpox globally eradicated?

1980

When did terrorism and bioterrorism emerge in the US?

Fall 2001

Did Smallpox hit the Midwest of USA in May 2003?

No, it was Monkeypox transmitted by a pet prairie dog bite

How did the US Monkeypox outbreak in 2003 occur?

through a chain of legal important, pet shops, and “pet swaps” where a Gambian Giant Rat is believed to have infected prairie dogs which, in turn, infected humans

The current moneypox outbreak represents the first time that monkeypox is spreading through sexual activity networks. This riases concerns that the virus may now spread extensively from?

person to person

Which disease is described:

• Calciviridae, Lagovirus

• identifies in China in 1984

• hemorrhages in the lungs and liver

• killed half a million rabbits in 6 months

• 1988 reached Europe and quickly spread to North America

• fecal/oral transmission

• epidemiologically, some spread was intentional because it was thought to be a good way to control wild rabbit populations

Rabbit Hemorrhagic Disease

What are the clinical signs of rabbit hemorrhagic disease?

• older than 2 months

• 24-72 hour incubation time

• depression, fever, serosanguinous or blood nasal discharge, nervous signs such as incoordination and shaking

What can be seen on necropsy in cases of rabbit hemorrhagic disease?

• nasal hemorrhages

• pulmonary congestion

• edema

• zonal necrosis of the liver

How do we diagnose rabbit hemorrhagic disease?

• hepatocytes contain viral antigen which can be seen using immunohistochemistry

• RT-PCR

• not able to be grown in cell culture

How do we control rabbit hemorrhagic disease?

easily spread and highly resistant so control using good husbandry

Is there a vaccine for rabbit hemorrhagic disease?

• vaccine available in Europe

• currently no licensed vaccines available for rabbits in the US

Is Rabbit Hemorrhagic disease classified as a foreign animal disease?

Yes

Which disease is described:

• Poxviridae, Leporipoxvirus

• Natural host is wild rabbits in North America and seen as localized benign fibromas

• in domestic rabbits, seen as severe generalized disease, Blepharaconjunctivitis and swelling of the muzzle and anogenital region, become febrile and listless, often die within 48 hours of clinical signs, CA strain has rapid progression and fatal outcome

Myxomatosis

How do we diagnose Myxomatosis is rabbits?

• clinical appearance

• cell culture

• electron microscopy

Is there a vaccine for Myxomatosis in rabbits?

• vaccine available in Europe — combination with RHD

• In US, attenuated California strain has been used in vaccine but not widely available

• COMBO VACCINE UTILIZING VECTORED STRAINS

What was the result of myxomatosis and RHD being used to control rabbit overpopulation?

• rabbits developed genetic resistance to the disease, surviving rabbits acquired immunity

• virus mutated to an attenuated strain

Why are hamsters not allowed in school classrooms, dormitories and are illegal to own in some states/countries?

Lymphocytic Choriomeningitis affecting hamters/pet rodents is zoonotic

If you have a pet rodent, what precautions should you take to reduce the risk of Lymphocytic Choriomeningitis infection?

• wash hands with soap and water after handling or use waterless alcohol based hand rubs when soap is not available

• keep rodent cages clean and free of soiled bedding

• clean the cage in well vetilated area or outside

• wash hands immediately after cleaning cages/handling dropping

• do not kiss pet rodents or hold them close to your face

What are the viral diseases of exotic and wild birds (that we discussed in lecture)?

• Eastern equine encephalitis (EEE)

• West Nile virus (WNV)

• avian influenza

How is Eastern Equine Encephalitis virus transmitted?

• multiple mosquito genera transmit virus to other animals

• transmission by direct contact among birds via pecking and preening

• transmission cycle between birds and mosquitoes

• C. Melanura is the primary vector for virus transmission to birds

• possible overwintering hoses (snakes, frogs)

• horses are dead end host

What is a dead end host?

a host from whcih infectious agents are not transmitted to other susceptible hosts due to insufficient viremia

What are the clnical signs of Eastern Equine Encephalitis virus in birds?

• clinical signs do not usually develop in most native species of wild birds infected

• clinical signs for nonindigenous birds, pen reared birds, and whooping cranes: depression, tremors, paralysis of legs, unnatural drowsiness, profuse diarrhea, voice changes, ataxia or loss of muscle coordination, involuntary circular movements, death

How do we control Eastern Equine Encephalitis virus?

• mosquito free flight cages recommended for rehabilitation situations and bug zappers

• killed virus vaccine used off label

How is West Nile Virus transmitted?

• mosquito vector (mosquito to bird to mosquito to bird cycle)

• horses are dead end host

What are the clinical signs of West Nile Virus?

• depressoin

• ataxia

• weight loss

• torticollis

• difficulty flying

• death

Which birds are very susceptible for West Nile virus?

songbirds of the family Corvidae (crow family)

What was found on necropsy of Alligators affected by West Nile Virus in Florida in 2002?

• meningoencephalomyelitis

• necrotizing hepatitis and splenitis

• pancreatic necrosis

• myocardial degeneration

• interstitial pneumonia

• stomatitis and glossitis

What diagnostic tests were used for West Nile in alligators?

• plague assay on tissues

• titers

How was West Nile transmitted between alligators?

• fecal-oral with virus shed in feces

• fighting between alligaors (not mosquitos)

• feeding infected meat, such as horse meat

• feeding opportunistically on infected wild birds

How do we diagnose West Nile virus?

• virus isolation via RT-PCR confirmation

• immunohistochemistry

• serology via plague reduction neutralization, ELISA, or hemagglutination inhibition

• WHOLE BIRD/ANIMAL MUST BE SUBMITTED

How do we control West Nile virus?

• mosquito control for rehab situations

• vaccination in zoo collections (no vaccine approved at this time for use in birds, equine vaccines have been used in avian species but efficiacy is not known)

Is West Nile Virus zoonotic?

Yes

What are the natural hosts and reservoir for avian influenza?

• wild waterfowl (ducks and geese)

• shorebirds

• gulls

What strains of highly pathogenic avian influenza (HPAI) affect swans and raptors?

H5N1, H5N2, or H5N8

How do raptors become infected with highly pathogenic avian influenza (HPAI)?

probably from eating infected water fowl