Lecture 1 - Introduction Flashcards
Define:
Zoonosis
An infectious disease that is transmitted between species from animals to humans
T/F
Zoonosis can be passed only directly
F
Both
Directly: ex. Rabies or Avian Influenza
Indirectly Via a vector intermediate (ex: WNV and mosquitos) Via food (ex: campylbacteriosis) Contaminated environment (Q fever)
Define: Reverse zoonosis (anthroponosis)
Diseases transmitted from humans to animals
Example of reverse zoonosis (anthroponosis)
Human to Gorillas (ex: Measles)
What is Conservation medicine
An emerging, interdisciplinary field that studies the relationship between human and animal health, and environmental conditions.
What are some criteria for zoontic disease **
1) a vertebrate reservoir exclusive of humans
2) transmission of the agent directly to people or from products derived from the host animal or through an arthropod intermediate
3) a recognized infectious disease syndrome in susceptible individuals
T/F
As animals became domesticated and a close bonds developed between animals and humans, the occurrence of zoonotic diseases decreases
False
It increased
Why are emerging zoonoses are a growing concern?
- Novel diseases that current medical system is not prepared to handle (Ex: SARS, mad cow disease)
- Outbreaks are unpredictable (Ex: Avian influenza)
3/ Outbreaks are increasing in recent times
(70% of all infectious outbreaks are zoonotic in origin)
- Outbreaks can occur anywhere and spread quickly throughout the globe
- Have a significant impact on global and country’s economies
Define
Enzootic
Epizootic
Enzootic: refers to a disease that is endemic (i.e. present at stable levels) among animal populations
Ex: Lyme disease in ticks and mice and plague in rats
Epizootic: and “epidemic” in animals
If in a specific locations, it an “outbreak”
If widespread it is “panzootic”
Define panzootic
Widespred epidemic in animals
Define:
Epidemic
Refers to human disease spread to a large number of people within a defined short amount of time
T/F
Of 1415 species of human pathogens recognized, 800 are known to be zoonotic
True
over half are zoonotic
T/F
Discovery of new human pathogen species is at a rate of 3-4 species /year
True
Types of zoonotic infections (5)
Bacterial Viral Fungal Parasitic Prions
List of viral diseases
Rabies
Rift Valley Fever West Nile virus Yellow Fever Dengue Monkeypox Lassa Fever
List of Bacterial Diseases
Brucellosis
Leptospirosis
Plague
Q fever
Rat bite fever
Lyme
List of Parasitic Diseases
Echinococcosis
Angiostrongliasis African and American Trypanosomiasis Babesiosis Chagas Clinorchiasis Cryptosporidiosis leishmaniasis
Risk Factors for zoonotic diseases
- Household pets
- Increased contact between humans and wildlife
- Increased human activity into wilderness areas
- Wild animals encroaching into human civilization
How Diseases Spread
- Through feces
- Fecal-oral
- Direct contact
- Insect vectors
What diseases can be passed through feces?
- Parvo
- Feline panleukopenia
- Salmonella
- Toxoplasma
- Worm eggs (rounds, whips, hooks)
- Giardia and Coccidia
What diseases can be passed through direct contact?
- Ringworm
- Scabies
- Ear mites
- Hookworm larvae
What diseases can be passed through insect vectors?
Mosquitoes - heartworms and encephalitis
Heartworm in humans extremely rare, but few reports can be found
Fleas - tapeworms, cat scratch fever, plague, typhus.
Ticks - Lyme disease and RMSF
List some agricultural exposures
- Frequent contact with domestic animals
- Overlap with wildlife habitat
- Large scale livestock production
- Poor animal sanitation and personal hygiene
T/F
Salmonella is a part of the normal gut flora in turtles and is shed in their stool, heavily contaminating whatever environment they are in
True
What happened after turtle/aslmonella outbreak
Small turtles (<10cm) were banned specifically to protect children as these are often purchased for children
Federal ban is difficult to enforce, many locally owned or independent pet shops still sell small turtles
T/F
Rabies has been used as an attempted weapon
True
Some attempted to use it as a weapon
DaVinci : terror-bomb created from Sulphur, arsenic, tarantula venom, toxic toads, and the saliva of mad dogs
T/F
Rabies remains endemic throughout the world
True
2/3 of the world’s population lives in a rabies endemic area
T/F
Rabies virus has the ability to infect and replicate in a wide host range
True
Historically, _________ transmission was more common until wide scale canine vaccine programs
canine-to-human
______ are important reservoir for rabies virus
Bats
T/F
Rabies deaths are predominately in the developing world
True
50,000/year
Main reservoir associated deaths are canines
Rabid dog exposures to rabies is responsible for
> _____% of human exposures
______% of human deaths
> 90% of human exposures
>99% of human deaths
Rabies is member of the order _____________
Mononegavirales
Other members of this order, Mononegavirales, are ______ and ________
filoviridae (ebola) and paramyxoviridae (measles)
Rabies
Family
Genus
Family Rhabdoviridae, genus lyssavirus
Rabies has a ________________ genome
Non-segmented negative strand genome
Rabies virions are ______ shaped with ______ appearance
“bullet” shaped, with “spiky” appearance
Majority of rabies cases occurring in which countries
Asia and Africa
Where has rabies never been endemic
New Zealand and Australia
Two main types of spread/maintenance for rabies
Urban: through dogs
Sylvactic (forest): through wildlife
What is the main reservoir for rabies worldwide? And why?
Main reservoir worldwide is dogs
Main reason for spread is lack of rabies control programs and lack of vaccinations
What is the main reservoir for rabies in the US? And why?
Main reservoirs in US are wildlife, due to successful dog vaccination programs
T/F
From 2003 to 2013 there were only 34 cases of human rabies in the US
True
Due to animal control and vaccination
What wild animals in the US have rabies?
- Raccoons
- Skunks
- Foxes
- Coyotes
- Bats
What wild animals in the US have bever transferred rabies to humans?
- Squirrels/chipmunks
- Rats/mice/hamsters
- Rabbits
In the US which wild animal accounted for most of the rabies cases?
- Bats
- Raccoons
- Skunks
- Foxes
In the US which domestic animal accounted for most of the rabies cases?
- Cats
Rabies in:
Europe
Successful control but fox and raccoon populations continue to pose a threat to complete elimination
Rabies in:
Asia
Grossly underreported
In India alone, estimated 20,000 people die of canine rabies.
Dramatic rise of rabies in China.
Rabies in:
Africa
Primarily canine in origin
Jackals, bat-eared foxes and mongoose are involved in rabies transmission in Africa
Rabies in:
Central & South America
Thru PAHO rabies vaccine programs, over the past 20 years has led to an almost 90% decrease in dog and human cases.
Rabies disease transmission
- Bite of an infected animal that contains virus in the saliva (Infection may occur at exposed mucous membranes (conjunctiva, oral mucosa….)
- Inhalation of aerosolized virus in bat caves has been reported. (extremely rare)
- Organ transplantation has been reported
- After the bite, the virions may enter the CNS directly or after initial replication within muscle tissue
Enters motor nerves through neuromuscular junctions
Can stay at inoculation site for days to months
T/F
After the bite, the virions may enter the CNS directly or after initial replication within muscle tissue
True
Enters motor nerves through neuromuscular junctions
Can stay at inoculation site for days to months
T/F
Non-Bite Exposure of rabies is common
False
- Aerosol exposure: laboratory accidents, caves with high concentrations of bats
Open wounds or mucus membranes must come into contact with infectious material like saliva or brain tissue - Organ transplant
Rabies Virus remains at inoculation site for ___________ before ascending up the nervous system
weeks to months
incubation period
T/F
Patient is asymptomatic during incubation phase for rabies
True
Length of phase determined by amount of virus and how close the site is to the CNS
- Virus inoculated through bite
- Replicates locally in muscle near bite
Prodrome phase of rabies
- Enters peripheral nervous system (nerves not in the brain or spine)
- Ascends up via sensory fibers
- Replicates in Dorsal Root Ganglia
- Rapidly ascends into spinal cord
Neurologic phase
the infection of the brain is rapid as is the spread to the tissues
- Infects CNS (spinal cord, brainstem, cerebellum, other parts of brain)
- Infection descends into eye, salivary glands, and skin
T/F
Little histologic change can be seen in post mortem brain tissue
True
Classic finding is the “Negri Body”
T/F
Rabies infection elicits an antibody response early before the beginning of the neurologic stages of the disease
False
Rabies infection does not elicit an antibody response until the late neurologic stages of the disease
However, antibody is effective at stopping the disease prior to the neurologic phase
T/F
Exogenous antibody can block rabies
True
The long incubation period allows for the vaccine to be administered as post exposure treatment
Length of Incubation period for rabies is determined by 5 factors
- The concentration of the virus in the inoculum
- The proximity of the wound to the brain
- Severity of the wound
- Host’s age
- Host’s immune status
Incubation period for rabies is typically ______ days but may be as long as _____ years
20-90 days
14-19 years
Entry virus at a _______ innervated site often leads to swift progression (ex: hands vs calves)
highly
(Also factors, the dose delivered, the subtype of rabies virus, and types of nervous tissue at bite site, depth of the bite, closer to the head)
Mortality rates for rabies due to location/type/extent of wound highest to lowest
- Face/bite/deep
- Face/nite/single
- Fingers/bite/severe
- Trunk+legs/scratch/mutiple
- Skin covered by clothes/wound/superficial
5 clinical stages of rabies
Incubation Period Prodrome Acute Neurologic Phase Coma Death
Prodrome- Early symptoms may be difficult to appreciate
and may resemble
tetanus, typhoid, malaria, and other viral encephalitis
Fever, nausea, vomiting, headache, lethargy
Describe the ACUTE NEUROLOGICAL DISEASE of rabies
- 80% develop “furious” rabies
1. Hyperactivity, disorientation, bizarre behavior, hypersalivation, sweating
2. Hydrophobia is actually dysphagia - 20% develop paralytic rabies (“dumb”)
1. Ascending symmetric paralysis with flaccidity and decreased tendon reflexes
T/F
No tests are available to diagnose rabies infection in humans before the onset of clinical disease
True
Unless the rabies-specific signs of hydrophobia or aerophobia are present, the clinical diagnosis may be difficult.
Antibodies in blood are not present until neurological disease starts
Post mortem, the standard diagnostic technique is to detect rabies virus antigen in brain tissue is ______________
by fluorescent antibody test
Diagnosising rabies
- Histopathology
- Antigen detection - brain/spinal fluid
- VIrus isolation (takes a long time)
- Nucleic Acid based PCR
Diagnosis of rabies:
Histopathology
Negri bodies-consist of reticulogranular matrix containing tubular structures
Found in the cytoplasm of undamaged nerve cells, particularly in the hippocampus
Diagnosis of rabies:
Antigen detection- brain/spinal fluid
Fluorescent antibody test, recommended by OIE and WHO as the “gold” standard
95-99% accurate, results within hours
Diagnosis of rabies:
Virus Isolation
Takes too long
Mouse inoculation test-Used for confirmation, tissue sample is injected into weanling mice
In-vitro isolation-inoculation into a neuroblastoma cell line and FAT test used
Diagnosis of rabies:
Nucleic Acid based-PCR
Increasingly used
Serology antibody testing not done, since rabies infection is uniformly fatal
Allows for strain typing which allows for identification of the likely source of infection and geographic location
Various strains are adapted to specific animal reservoir hosts
Instrumental for CA- told us risk of bat
T/F
We have had an effective vaccine for rabies has been available for over 100 years
True
Invented by Pasteur in 1885
100% effective
T/F
Rabies vaccine may be given pre-exposure or post exposure
True
Pre-recommended for those working with the virus or have potential of contact
Post-key point is timing
Should be administered rapidly
Expensive and in short supply
RIG-Injected surrounding the wound and any left over injected into the intramuscular + rabies vaccine given
T/F
Animals can be vaccinated for rabies
True
Estimated that at least 50 million dogs are vaccinated each year against rabies.
However, in many parts of Asia and Africa the vaccination coverage established in the dog population (30% to 50%) is not high enough to break the transmission cycle of the disease
Considerations for rabies prophylaxis
- Epidemiology of rabies in the region
- Type of exposure
- Whether it was provoked or unprovoked
- The species and vaccination status of the animal
Data shows that animals like dogs, cats, and ferrets begin to sicken and die within _______ days of exposure to rabies
10 days of exposure
If a domestic animal with rabies bites a person, then they should be observed for ______ days
r 10 days
- If they show any illness, then they should be euthanized and the head should be shipped to a laboratory for rabies testing
- If animal is healthy for 10 days, then no rabies
- If bit around head, prophylaxis immediately as the incubation period can be as short as four days
Post Exposure Rabies Prophylaxis
- After bite, wash area with soap and water and use virucides such as povidone-iodine if possible
- Requires both active and passive immunity
3/ Must be given ASAP - Rabies vaccine = active immunization (body will produce its own antibodies)
- Rabies immunoglobulin= passive immunization (provides a shot of immediate antibodies to fight virus)
Pre-Exposure Rabies Vaccine
- Vaccine only
- Travelers in whom rabies pre-exposure prophylaxis should be encouraged include:
- The following groups should be vaccinated as well: animal workers, lab workers who handle potentially infected tissue, and travelers
Rabies Prevention
- Estimated public health costs assoc. w/ disease detection, prevention, & control have risen, >$300 million annually.
- Surveillance is important in the US
- In the US, domestic animals are continuously vaccinated
- National mass dog vaccination campaigns are the most cost-effective strategy for preventing rabies globally
- WHO program to eliminate rabies world wide
T/F
Culling is effective in preventing rabies
False
WHO Tanzania Rabies Unique Approach (3)
- Data collection - mobile phoe syrvveillance system
- Human post-exposure prophylaxis
- Canine vaccination (aiming for 70%)
WHO Tanzania Rabies
Achievement
- Animal bites halved in areas
- Human rabies death decreased
- Established mobile phone survellance system
- Canine vaccination campaign
WHO has been collecting rabies data electronically through ______
“Rabnet”
