Diseases Flashcards
– Infectious diseases have many sources
• Viruses, bacteria, fungi, prions, and protozoans
Disease – Impairment to health
- Physiological or psychological imbalance
- Poor nutritional state
- Stressed state
- Infections
Zoonoses
• Infectious diseases transmitted between animals and
humans
• Wildlife may serve as hosts or vectors
• Constitute over 70% of emerging infectious diseases
– Human-wildlife contact more common
– Outdoor recreation and ecotourism are increasing
• Three factors must be present for any disease
to occur
– Host must be susceptible to disease agent
– Environmental conditions must promote pathogen
stability and viability
– Host and pathogen must come into contact
relatively frequently
• Parasites generally do not kill their hosts
• Parasitic diseases can lead to population
declines
• Parasite-caused extinctions
– Occur in multi-host parasites
– Groups with domestic mammals most susceptible
(Artiodactyla and Carnivora)
– Reducing contact between wild and domestic
mammals may minimize disease
Monkeypox Virus
• Member of orthopoxvirus family
– Creates skin lesions similar to smallpox
– Humans infected via direct contact with infected
animals
– Disease endemic to Central and West Africa
– Bushmeat may be important route of infection
– 2003 US outbreak
• Shipment of infected small mammals from Africa
distributed to pet stores
Ebola Virus
• Ebola hemorrhagic fever (EHF)– a Filovirus
– Rare but often fatal infectious disease
– Discovered in Central Africa in 1976 near Ebola
River
– Causes fever, vomiting, diarrhea, pain, and
internal and external bleeding
– Pteropodids believed to be primary reservoir
Nipah Virus
• Humans suffer neurological problems • Endemic to Malaysia • Viral reservoir includes pteropodids – Large bat roosts spread virus to pigs – Pig farmers contracted disease from sick pigs
Hantavirus
• Hantavirus family of viruses
• Originated in Korea and in western United States
(Sin Nombre virus)
• Muroid rodents reservoir for varieties infecting
humans
– Also found in shrews in United States, Asia, Africa
– Humans infected by aerosolized saliva, feces, urine, or
when bitten
– Most species that host hantavirus do not frequent
urban areas
Rabies
• RNA virus
• Infects endotherms (including humans)
– Infects bats, primates, cattle, and a wide range of
carnivores
– Domestic dogs and cats pick up rabies from
contact with wild animals
• Virus present in saliva of infected animal
– Typically contracted from a bite
Rabies
• Late-stage symptoms
– Acute pain – Uncontrolled movements – Aggressive behavior – Profuse salivation – Inability to swallow water • Eventually results in coma and death
Rabies
• 55,000 human deaths from rabies in 2006
• In Africa, Asia, and Latin America dogs are
primary reservoir
• Pattern of wildlife rabies in the United States
is regional and species-specific
– Raccoons in the mid-Atlantic and Northeast
– Skunks in the Midwest
– Insectivorous bats widespread
Prion Diseases
• Prions
– Misfolded proteins
– Cause neurodegenerative diseases
• Bovine spongiform encephalopathy (BSE)
– “Mad cow disease”
– Suspected link between BSE and human prion
disease
• Variant Creutzfeldt-Jakob Disease (vCJD)
• Outbreaks in Europe and North America
Prion Diseases
• Chronic Wasting Disease (CWD)
– Transmissible spongiform encephalopathy
– Infects deer, elk, moose
– Spreading across western and midwestern United
States since 1967
– Spreads via nose-to-nose contact or contact with
excrement
Bacterial Diseases
• Plague – Bacterium Yersinia pestis – Human infections have led to pandemics – Symptoms include fever, body ache, and nausea – Three clinical forms • Bubonic plague (most common) • Septicemic plague • Pneumatic plague
