Transcript West Nile Virus in the U.S. and Missouri: Current Numbers

Arthropod Diseases Affecting
Outdoor Activities: Lyme Disease
Dr. Richard M. Houseman
Department of Entomology
University of Missouri
Lyme Disease Background
• Bacterial disease first identified in
Conneticut (1977)
– Inflammation of joints (arthritis)
– Rarely, if ever fatal
• 92% of all cases occur in nine states
– CT, RI, NY, PA, DE, NJ, MD, MA, WI.
• Leading cause of vector-borne infectious
disease in U.S. (15,000 cases annually)
– Borrelia burgdorferi
– Similar bacteria in Europe, Asia
Lyme Disease Transmission
• Transmitted by the bite of infected tick
Ixodes scapularis
– Rodents, deer, birds, dogs are primary hosts
– Human infections after tick feeds for >36 hours
• In temperate areas (24º-66º latitude)
virus transmission is seasonal
– Most in late spring to mid summer (nymphs)
– Few in fall and early spring (adults)
adults + eggs
SPRING
nymphs
adults
nymphs
FALL
adults
nymphs
WINTER
adults
YEAR 1
SUMMER
(dormant)
(dormant)
YEAR 2
larvae
Lyme Disease Risks
• Risk of exposure is greatest in woods
and fringe areas of properties
– Ticks may also be transported to lawn/garden
• Highest attack rates
– Children 0-14 and 30+ years of age
• Outdoor recreation, outdoor work, new
homes in wooded areas
• Blood transfusions, infected blood, urine
are NOT documented risks
Lyme Disease Symptoms
• Within 7-14 days 80% of people
develop red, expanding bulls eye
– Tired, fever, headache, muscle aches, joint pain
• If untreated some patients develop
arthritis within a few weeks to months
– Also swelling, meningitis, facial palsy, encephalitis
• Antibiotic treatment for 3-4 weeks
– Doxycycline, amoxicillin, erythromycin
– NO immunity
Lyme Disease in Missouri
• 90 to 100 cases per year on average
– Low risk overall
– Relatively high compared to neighboring
states
– Reported cases have decreased
dramatically in recent years
• Lyme-like condition present (STARI)
– Southern Tick Associated Rash Illness
Average Number of Lyme Disease Cases Reported
Each Year by State Health Departments (1990-1999)
120
MO
AR
OK
KS
NE
IA
IL
KY
TN
Average Cases per Year
100
80
60
40
20
0
MO
AR
OK
KS
NE
State
IA
IL
KY
TN
Lyme Disease Cases Reported to CDC by Missouri
State Health Department (1990-1999)
250
Cases Reported
200
150
100
50
0
1988
1990
1992
1994
Year
1996
1998
2000
STARI
• Southern Tick Associated Rash Illness
– ER indistinguishable from Lyme Disease
• Transmitted by bite of Amblyomma
americanum
– Tick is abundant in southern states
– Similar life cycle and ecology
• Borrelia lonestari
– Serologically different from Lyme bacteria
Preventing Lyme Disease
• Minimize and Avoid tick habitats
– Leaf litter, brush, wood piles, tall grass
– Spring/summer when nymphs are prevalent
• Use personal protective measures
– Clothing
• Long sleeved shirts, light colors, tuck pants into socks
• Permethrin
– Repellents
• DEET on clothing or skin
– Tick check and removal