Slide1 : Emerging Zoonoses and Species Jumping
September 11th 2007
Slide2 : Zoonoses- transmission of the infectious agent
to humans from an ongoing reservoir life cycle
in animals, without the permanent establishment
of a new life cycle in humans.
Species Jumping- the infectious agent derives
from an ancient reservoir life cycle in animals,
but they have established a new life cycle in
humans that no longer involves the animals. Definitions
Slide3 : Emerging Infectious Diseases-
nearly all are zoonotic or species jumping agents
Animals Involved in Species Jumping : Animals Involved in Species Jumping Arthropods (e.g. ticks and mosquitoes)
Wild animals (e.g. chimps and rodents)
Domestic animals (e.g. dogs and cats)
-draught (e.g. horses)
-food (e.g. poultry and cattle)
Elements that Contribute to the Emergence of a New Zoonoses : Elements that Contribute to the Emergence of a New Zoonoses Microbial/viral (e.g. mutations and evolution)
Individual host (e.g. acquired immunity (vaccination)
and lack of immune surveillance (AIDS)
Population host (e.g. transportation and urban crowding)
Environmental (e.g. ecological and climate influences)
Increases in Zoonotic Pathogens : Increases in Zoonotic Pathogens Global human and livestock populations continue to grow
-this brings people and animals in closer contact
Advanced transportation makes long distance travel
possible in less than the incubation period
of most infectious agents
Massive ecological and environmental changes brought
about by humans
Zoonotic agents may be the choice for many
bioterrorist activities
History of West Nile Virus (WNV) : History of West Nile Virus (WNV) In 1937, WNV first isolated from a febrile woman in the
West Nile Distinct of Uganda
Negative strand RNA virus of the family Flaviviridae
In 1957, WNV outbreak in Israel
Early 1960s, WNV noted in horses in Egypt and France
In 1999, WNV first seen in North America
West Nile Virus Human Cases in the US :
-62 cases with 7 deaths in New York only
-21 cases with 2 deaths in 12 states
-66 cases with 9 deaths in 10 states
-4156 cases with 284 deaths in 40 states
-9862 cases with 264 deaths in 46 states
2004 -2539 cases with 100 deaths in 42 states
2005 -3000 cases with 119 deaths in 44 states
2006 -4269 cases with 177 deaths in 44 states West Nile Virus Human Cases in the US
U.S. cases of West Nile for 2003 : U.S. cases of West Nile for 2003
U.S. cases of West Nile for 2004 : U.S. cases of West Nile for 2004
U.S. cases of West Nile so far for 2007 : U.S. cases of West Nile so far for 2007
West Nile Virus : West Nile Virus -Spread by mosquitoes, which transmit it from infected birds.
mosquito species does make a difference.
-Alligators have WNV titers as high as birds, thus they can serve as a reservoir too.
-Certain titers need to be reached in order to infect mosquitoes. Horses and humans do not have high titers.
-300 captive alligators that died in 2002 in Florida, necropsies showed the alligators had high viral loads of WNV.
-Although birds often die within hours of contracting WNV, alligators may live for days or weeks after being infected. That allows the alligator to pass the virus on to more mosquitoes.
Slide14 : Finding WNV in NYC
First 8 cases were in a 2 x 2 mile radius in NYC
Older patients that most had been outside a lot
Lots of mosquito breeding places and dead
crows around the area
Exotic birds died at the Bronx zoo
Birds had died of encephalitis and had WNV
Slide15 : West Nile Fever
Incubation is 3-15 days
Symptoms: fever, headache, backache, myalgia,
Can include: nausea, vomiting diarrhea, rash,
muscle weakness, paralysis….weakness and
confusion can go on for months afterwards
Encephalitis usually does not have
muscle weakness and paralysis
Other WNV : Other WNV In the US during 2002, 23 cases of WNV were transmitted through blood donations. Blood in now screened for WNV
8/8/03 American Red Cross reported 31 positive blood donations in Nebraska, the highest number of positive donors in US
9/12/03 More than 150 Colorado blood donors tested positive for West Nile virus, thus more than 35,000 people statewide might be infected. 116 positive from Nebraska.
WNV shows symptoms in only 20% of the people who contract it.
Equine vaccine- some questions for pregnant horses, but definitely all non-pregnant horses should be vaccinated, since fatality rate is 35%.
Questions about WNV : Questions about WNV How did West Nile virus get into this country?
-a mosquito on an airplane?
-a bird on an airplane?
Where will the impact be greatest?
Why does West Nile virus grow in different types
of mosquitoes?
As WNV spread west, why were there less cases east?
Monkeypox : Monkeypox -Normally occurs in central and western Africa
-It is called “monkeypox” because it was first found in 1958 in laboratory monkeys
-African squirrel are likely the common host, but rats, mice, rabbits, (maybe any mammal) can get monkeypox
First reported in humans in 1970
-It belongs to the orthopoxvirus group of viruses. Other orthopoxviruses that cause infections in humans include variola (smallpox), vaccinia (used for smallpox vaccine), and cowpox viruses.
How was monkeypox introduced into the US? : How was monkeypox introduced into the US? -A shipment of animals from Ghana that was imported to Texas on April 9 is the probable source.
-The shipment contained approximately 800 small mammals (9 different species). These included rope squirrels, tree squirrels, Gambian giant rats, brush-tailed porcupines, dormice, and striped mice.
-Evidence of infection was found in some animals. They were separated from the rest of the shipment on the day of their arrival, but there was already likely widespread infection among the remaining animals in the shipment.
-CDC laboratory testing of some animals by using PCR and virus isolation demonstrated that at least 1 Gambian giant rat, 3 dormice, and 2 rope squirrels from the April 9 importation were infected with monkeypox virus.
-Gambian rats from this shipment were kept in close proximity to prairie dogs at an Illinois animal vendor implicated in the sale of infected prairie dogs.
How did people catch monkeypox? : How did people catch monkeypox? People bought infected prairie dogs at pet stores
and swap meets
If they were bitten or if they touched the animal’s blood,
body fluids, or rash, they were infected
Epidemiology showed that there was not person to
person spreading.
Number of cases reported to the CDC : Number of cases reported to the CDC
STATE # of cases
Illinois 16
Indiana 20
Kansas 1
Missouri 2
Ohio 1
Wisconsin 39
Total 79
What are the symptoms of monkeypox? : What are the symptoms of monkeypox? About 12 days after people are infected, they get fever, headache, muscle aches, backache, swollen lymph nodes, and they feel tired.
One to 3 days (or longer) after the fever starts, they get a rash that develops into raised bumps filled with fluid. The bumps go through several stages before they get crusty, scab over, and fall off.
The illness usually lasts for 2 to 4 weeks.
There is no specific treatment for monkeypox.
Epidemiologic criteria is exposure to:
-a new exotic or wild mammalian pet obtained on or after April 15 2003
African Trypanosomiasis : African Trypanosomiasis Classical example of an emerging infection, 1890-1930
Leading public health problem in Africa during that time,
colonialism brought it to new areas
Nearly eliminated by 1960 using population screening,
case treatment, chemoprophylaxis
Re-emerging infection in central Africa
African Trypanosomiasis, cont. : African Trypanosomiasis, cont. West African East African
Agent: T. brucei gambiense T. brucei rhodesiense
Vector: riverine tsetse fly savanna tsetse fly
Distribution: west/central Africa east/south Africa
Reservoir: human antelope/cattle
Disease: chronic (years) rapid progression: 1-4 weeks
Mortality: 70% 100%
At risk: rural persons rural, visitors to game reserves
Problems Estimating Disease Burden : Problems Estimating Disease Burden 60 million people at risk, but <2 million screened
No health facilities in many areas at risk
Conflict or insecurity in epidemic foci
Outbreaks in 2004 reported in DRC, Angola
Clinical diagnosis is difficult until late in disease
-intermittent fever
-lymph node swelling
-headaches and sleep disturbance
-weight lose (they look like AIDS)
-lab diagnosis is hard (antigenic variation)
Prevalence of trypanosomiasis : Prevalence of trypanosomiasis -In 1986, WHO est. that 70 million people lived in transmission areas.
-In 1998, 40,000 cases were reported, but it was estimated that 300,000 to
500, 000 cases were undiagnosed.
-Villages in the Congo, Angola, and Sudan, prevalence has reached 50%.
-By 2005, surveillance had been reinforced and new cases dropped.
1998-2004 cases fell from 40,000 to 18,000.
-The estimated cases is currently between 50,000 and 70,000.
Management of Trypanosomias : Management of Trypanosomias Disease management in three steps:
1) Screening for potential infection. Serological tests and/or checking for swollen cervical glands.
2) Diagnosis shows whether the parasite is present.
3) Staging to determine the disease progression. -examination of cerebro-spinal fluid by lumbar puncture
Treatments for Trypanosomias : Treatments for Trypanosomias First stage treatments:
Pentamidine: discovered in 1941, used against T.b. gambiense. Despite a few undesirable effects, it is well tolerated by patients.
Suramin: discovered in 1921, used against T.b. rhodesiense. Effects in the urinary tract and allergic reactions.
Second stage treatments:
Melarsoprol: discovered in 1949, used against both forms. Arsenic derivative with many side effects. Fatal encephalopathy (3% to 10%). 1997 resistance up to 30%.
Eflornithine: was registered in 1990. Only effective against T.b. gambiense. Less toxic alternative to melarsoprol, but the regimen is strict and difficult to apply.
Dealing with Zoonoses : Dealing with Zoonoses Why are they jumping? Can we predict or stop it?
Who will be the world’s doctor?
Who will be the world’s expert on zoonotic diseases?
New strategies need to be developed to deal specifically
with emerging zoonoses
These strategies need to involve more field and
lab research than traditional surveillance