Download “Environmental factors influence transmission of Sin Nombre

“Environmental factors influence
transmission of Sin Nombre
hantavirus between rodents (and
to humans?)”
•
C. H. Calisher, J. N. Mills*, J. J. Root, J. B. Doty, B. J. Beaty
•
Arthropod-borne and Infectious Diseases Laboratory, Department of
Microbiology, Immunology and Pathology, College of Veterinary
Medicine and Biomedical Sciences, Colorado State University, Fort
Collins, Colorado
* James N. Mills, Ph.D., Special Pathogens Branch, National Center
for Infectious Diseases, Centers for Disease Control and Prevention,
Atlanta, GA
•
Beginning in the spring of 1993, an epidemic of
what came to be known as Hantavirus
Pulmonary Syndrome (HPS) occurred in the
southwestern U.S.A.
Most of the first case-patients were Native
Americans.
The initial mortality rate was about 60%.
The virus causing this had been unknown.
The first humans infected with this virus
were from the “Four Corners” states
Etiologic agent
• Family Bunyaviridae
• Genus Hantavirus
• Hantaviruses had been known to cause
hemorrhagic fever with renal syndrome in
Asia and Europe
• This virus, named Sin Nombre virus, was
causing pulmonary dysfunction, no
hemorrhaging, little renal involvement
The vertebrate host of Sin Nombre virus is
the deer mouse, Peromyscus maniculatus
The deer mouse is the most
common mammal in North America
• It invades houses
• It breeds prolifically (as do many rodents)
• It does NOT occur along the eastern
(Atlantic) coasts of the U.S.A. or Canada
• Populations of deer mice fluctuate from
year to year
Under contract with the U.S. Centers
for Disease Control and Prevention,
research groups in northern and
southern Arizona, New Mexico, and
Colorado began long-term studies of
the prevalence of Sin Nombre virus, the
densities of rodent populations, and the
factors that may influence both.
We began studies in southeastern
Colorado
… and in western Colorado
Major data collected
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Prevalence of antibody to Sin Nombre virus
Seasonality of transmission of Sin Nombre virus
Rodent population densities
Vegetation
Terrestrial insects
Air temperature
Precipitation (rain and snow)
Ground moisture
Deer mouse genetics
Red Rocks Canyon, Pinyon Canyon
Maneuver Site (overview)
Red Rocks Canyon, Pinyon
Canyon Maneuver Site (close view)
Recaptured deer mice, by sex and number
of weeks after first captured
Sex
Total
0a
6
7-18
19-30
31-42
43->66 Mean
201
29
53
20
10
4
17.4
313
51
55
39
14
3
17.0
Female
317
Male
475
a
0 = not recaptured
Incidence of IgG antibody reactive with Sin Nombre virus in
deer mice (Peromyscus maniculatus) recaptured and sampled
at least twice at PCMS, southeastern Colorado, January
1995-November 2000.
• Sex
Incidencea
Cum.% aby
• Male
• Female
• Total
0.81
0.23
0.57
3.4
0.9
2.2
•
a
New infections per 100 mice per month
Quarterly precipitation as recorded at three weather
stations at or near the Pinyon Canyon Maneuver Site,
southeastern Colorado, 1995-2000.
300
Red Rocks Canyon
Rocky Ford
Bear Spring Hills
250
200
150
100
50
0
W Sp Su A W Sp Su A W Sp Su A W Sp Su A W Sp Su A W Sp Su A
A.
14
12
10
8
6
4
2
0
*
3
*
2
*
1
0
-1
-2
-3
-4
3.5
3
*
Mean maximum temperature deviation
*
P. maniculatus trap success
B.
14
12
10
8
6
4
2
0
*
*
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
Mean minimum temperature deviation
P. maniculatus trap success
-2
125
100
16
14
12
10
8
6
4
2
0
-2
-4
-6
-8
*
C.
*
75
*
50
*
*
25
0
-25
-50
Precipitation deviation
-75
W
Sp Su
1995
A
W
Sp
Su
1996
A
W
Sp
Su
P. maniculatus trap success
A
1997
Season and Year
W
Sp Su
1998
A
W
Sp
Su
1999
A
W
Sp Su
2000
A
Peromyscus maniculatus
trap success (%)
o
Mean Maximum Temperature
C) (
o
C) (
Mean Minimum Temperature
4
150
Precipitation (mm)
Deviation from-yr50Mean
5
Quarterly trap success for deer mice and total quarterly precipitation
(A); percent of adults in reproductive condition and percent of
captures consisting of juveniles (B), at two mark-recapture sites in
southeastern Colorado, 1995-2000.
Precipitation (mm)
250
16
P re c ip it a t io n
A.
T ra p s u c c e s s
14
12
200
10
150
8
6
100
4
50
2
0
100
0
B.
B re e d in g
J u ve n ile
Percent
80
60
40
20
0
W
Sp
Su
1995
A
W
Sp
Su
1996
A
W
Sp
Su
1997
A
W
Sp
Su
1998
S eason and Year
A
W
Sp
Su
1999
A
W
Sp
Su
2000
A
Individuals/100 trap nights
300
The 1991-1993 El Niño
Peromyscus spp.
rodent abundance
begins to increase in
central New Mexico
Peromyscus spp. rodent
abundance increases
abruptly at some central
New Mexico sites
El Niño
begins
Warm, wet winter
9/91
11/91
1/92
3/92
Rodent densities
decline to normal
levels by fall
Second
consecutive warm,
wet winter
5/92
7/92
9/92
11/92
1/93
3/93
5/93
7/93
9/93
11/93
Initial HPS cases detected
near the Arizona-New
Mexico-Colorado border
Main HPS outbreak ends by
August, with 29 cases in Four
Corners states
The 1997-1998 El Niño
Deer mouse abundance
increases 20-fold at
some northwestern New
Mexico sites
El Niño
begins
4/97
6/97
SNV antibody
prevalence begins
to increase in deer
mice in
northwestern New
Mexico
The 1997-1998
El Niño ends
8/97
10/97
12/97
2/98
4/98
6/98
10-fold increase in
abundance of SNVantibody positive deer
mice at some sites in
New Mexico
SNV antibody prevalence
increases rapidly in deer
mice
8/98
10/98
12/98
2/99
4/99
33 HPS cases reported
(5.5-fold increase over the number of cases expected)
6/99
8/99