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Feeling under the weather?

• BIOWEATHER
• Pests locust plagues
• Parasites worms, flukes and spirochetes
• Diseases emerging viruses

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Locusts and grasshoppers in Africa
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Desert Locusts
Locusts eat their own weight (about 4 g) in plant
matter per day a swarm may consist of a billion
insects, and 100 swarms may be on the move during
a plague (eating 400 kilotons per day). A swarm
can fly 300 km in one day, remain afloat out at
sea (and take off again), and remain active even
when covered by snow.
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juvenile
egg
solitary hopper
gregarious locust
Source BBC website
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Last major locust plague (1987-89)
Outbreak 1967-68. Drought in Africa in 1970s
and early 80s produced a recession in the locust
cycle. Heavy rains in 1987-89. In Jan. 1987
large swarms formed in Saudi Arabia. Despite the
Saudis massive control efforts some of the
swarms crossed the Red Sea and gradually moved
west to Mauritania and north to Algeria. Western
Sahara had heavy rains, and threat to the states
in North Africa was so grave that Morocco
deployed 200 000 soldiers to combat the
swarms. Strong winds aloft (associated with
Hurricane Joan) carried some of these locusts
across the Atlantic to the Caribbean in October
1988. They reached as far west as Jamaica.
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Upsurges in 1990s
1996-1998 Local upsurge in Red Sea Basin (from
Yemen - Saudi Arabia to Sudan - Ethiopia -
Somalia -Eritrea)
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2004 outbreak
a
b
Nov.
CYPRUS, EGYPT
c

• map of outbreak
• b) swarms in Mauritania
• Aerial spraying in the western Sahara

Source BBC website
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Monthly snapshots of outbreaks from Nov.
2003-Nov. 2004
gregarious adults gregarious juveniles
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Rainfall and the Australian plague locust
2004 plague
Scale of outbreak
Sources BBC website www.affa.gov.au
www.bom.gov.au/silo/products/cli_chg
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Combating locusts

• Good news
• Prediction of swarm development and movements
  much easier with satellites which can identify
  areas of new plant growth and wind patterns in
  remote desert areas.
• Aerial spraying of young (pre-swarm) populations
  with insecticide (e.g. malathion) is still
  effective.
• New biopesticide (Metarhizum fungus Green
  Muscle) kills locusts and grasshoppers in 3 - 4
  weeks.
• Trigger for gregarious behaviour (hind leg
  stimulation!) recently identified may lead to
  suppression techniques.
• Locusts are more nutritious than beef - Cooking
  with Sky Prawns (20 recipes for cooking locusts
  from Australia)

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Combating locusts

• Bad news
• Highly cyclical nature leads to poor maintenance
  of surveillance and control equipment during
  recessions.
• Political conflicts create refuge areas for
  swarms The western Sahara desert is littered
  with land mines from the Polisario
  war.Morocco-Algeria-Libya are reluctant to
  cooperateThe Sudan is currently in the midst of
  a civil war locust control is not a priority for
  the local government or for international
  humanitarian agencies.

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Malaria (Ital bad air)
1990s 2 000 M people at risk
300 M are infected 110 M cases
reported annually (85 in
Africa 7 in SE Asia) Deaths 1 - 2 M
annually
Vector Anopheles mosquito (50-60 spp of the 380
known species of anophelines) can
carry the parasites. Parasites Four species of
Plasmodium. P. falciparum causes most severe
symptoms. Symptoms high fever, dehydration,
death in severe cases
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Global incidence of malaria
Map area equivalent to cases per 100 people (92
of all cases in Africa)
Source www.worldmapper.org/posters/worldmapper_ma
p229_ver5.pdf
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The malaria transmission cycle I
http//www.cdc.gov/malaria/biology/life_cycle.htm
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The malaria transmission cycle II
After a single sporozoite (the parasite form
inoculated by the female mosquito) of Plasmodium
falciparum invades a liver cell, the parasite
grows in 6 days and produces 30,000-40,000
daughter cells (merozoites) which are released
into the blood when the liver cell ruptures. In
the blood, after a single merozoite invades a red
blood cell, the parasite grows in 48 hours and
produces 8-24 daughter cells, which are released
into the blood when the red blood cell ruptures.
These male and female gametocytes are ingested by
the mosquito during a blood meal, and inoculation
of sporozoites begins again in the mosquito.
http//www.cdc.gov/malaria/facts.htm
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Role of climate in malaria outbreaks
Moisture Breeding success of mosquitoes is
maximised in nutrient-rich pools populations
are most abundant in wet weather. Too much rain,
however flushes pools and reduces breeding
success. At temperatures between 25-30C the
malarial parasites and mosquito larvae mature
quickly, the adult mosquitoes live longer, and
female mosquitoes feed more frequently.
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Temperature-controlled development of Plasmodium
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P. malariae
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Length of the life-cycle in anophelines (weeks)
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P. falciparum
P. vivax
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optimal
0
15 20 25
30
Temperature (C)
minimum
maximum
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Sri Lanka (Ceylon)topography and annual
precipitation (mm)
1000
1500
gt2000
Summer monsoon
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Malaria epidemic Sri Lanka (Ceylon) 1934-5
Malaria hyperendemic in dry north of island but
rare in wet south (heavy rains flush mosquito
larvae away). Southern population has little
natural immunity. Drought in 1934-5 resulted in
major epidemic in south. 30 of population fell
ill 80,000 died. Illustrates Rosss math of
malaria (25d fever cycle)
1000 100 10 1
cases
0 25 50 75 days
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The East African malaria resurgenceis climate
change to blame?
Kericho Kabale Gikonko Muhanga
Months suitable for P. falciparum transmission
Hay et al., (2002) Nature 415, 905 - 909
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Geography of malaria risk in N. America (AD 2000)
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Disease and climate changea future geography of
malaria?
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The demise of malaria in the USA (1918-1946)
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Malaria resurgence .. and decline
2005-6 10 000 cases in South Africa 2006-7 3
000 cases in South Africa
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Why was malaria widespread in northern Europe in
the LIA?
Little Ice Age
from Reiter, P. 2000. "From Shakespeare to
Defoe Malaria in England during the Little Ice
Age Emerging Infectious Diseases vol. 6
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Bilharzia (Schistosomiasis)

• Infection caused by parasitic flatworms
  flukes in the genus Schistosoma.
• Freswater snails are the intermediate hosts.
  Infection occurs through skin whilst wading in
  water. Eggs released by humans defecating or
  urinating near these bodies of water.
• Victims become emaciated and very weak.
• Common in areas such as the Nile Valley for
  several thousand years. Incidence varies with
  intensity of flooding in (sub)tropical lowlands.

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Bilharzia distribution
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Bilharzia flukes, intestinal worms anda severe
symptoms (enlargement of the liver and spleen)
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Lyme Disease

• Infection caused by bacterial spirochetes
  (Borrelia burgdorferi) transmitted by
  blood-sucking ticks.
• Symptoms include arthritis, heart problems and
  severe neurological/nerve disorders.
• Discovered in USA in 1975 (Lyme, CT)
• Continued to increase and spread since
  surveillance began in 1982.
• Lyme disease has global distribution in temperate
  areas.
• Complex ecology linked to climate and land-use
  changes.

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Deer ticks (Ixodes species)
N.B. - The dog tick is not a member of the
Ixodes genus and cannot spread Lyme disease
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Number of cases of Lyme disease reported in
US 1982- 1997
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Why has incidence of Lyme disease increased in
New England in the last 25 years?

• Farm abandonment in early decades of last
  century.
• Abandoned farmland undergoes ecological
  succession to oak-maple forest in about 50-80
  years.
• Expansion of suburban development into rural
  areas around NYC-Boston.
• Reduced hunting of deer?

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Lyme disease and the ecology of oak-maple
woodlands
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Climate and viral disease

• Viral disease transmission
• Ecology of flavivirus outbreaks
• (e.g. dengue, West Nile encephalitis)
• Ecology of bunyavirus outbreaks
• (e.g. sin nombre)

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Emerging viruses
Family Disease Vector and Reservoir
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Dengue (hemorrhagic) fever

• Inter-human transmission of DF by mosquito (esp.
  Aedes) bites. Fever lasts a few days.
  Complications can give rise to DHF (Fatal in gt20
  of cases if untreated).
• DF cases common in humid (sub)tropical climates
  esp. in wet season (improved breeding success for
  Aedes).

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World distribution of Aedes aegypti and dengue
fever epidemics
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Distribution of Aedes aegypti in the Americas
1995
Two decadesafter eradicationprogramme relaxed
After post-war yellow fever eradicationprogramme
.
Prior to yellow fever eradicationprogramme.
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Distribution of dengue in the Americas
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West Nile virus

• West Nile virus is a strain of flavivrus, closely
  related to Japanese encephalitis. Previously
  reported from Africa and adjacent areas of
  southern Europe and western Asia. Previous
  outbreaks in Israel, France and S. Africa. and
  Romania (1996 450 cases, 39 deaths).
• It joins at least four other encephalitis viruses
  in North America, one of which St. Louis
  encephalitis is widespread.
• Likely introduced into N. America by an infected
  international traveler or as a result of the
  importation of exotic birds.

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fever, aches, stupor, (brain lesions, coma,
paralysis, death?)
direct transmission?
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WNV cases - Canada
2002 2003 2004 2005 2006 2007
Nova Scotia 0 2 0 1 0 1
New Brunswick 0 1 0 1 0 0
Québec 20 17 3 4 1 2
Ontario 394 89 13 95 42 12
Manitoba 0 142 3 55 50 578
Sask. 0 937 5 58 19 1285
Alberta 0 272 1 10 39 318
BC 0 20 0 0 0 19
Yukon/NWT 0 1 0 0 0 0
CANADA 414 1481 25 225 151 2215
some related to travel outside province all
related to travel outside province
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November, 2003
Total number of cases by state Is the WNV
threat declining in N. America?
November, 2007
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Resurgence of WNV in southern California Is
this a by-product of the credit crisis? Have
foreclosures led to increased mosquito breeding
in neglected ponds and pools?
L.A. Times (Aug. 6, 2008)
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Ecology of a hantavirus outbreak
animal reservoir (esp. mice)
humans
faeces, urine
Symptoms first noted in a Chinese medical text
dating from about AD1000. Major outbreak in
Korean War (gt2000 UN troops infected). Hantaan
is a river in Korea. Fatal form stretches west
to Balkans and into Americas non-fatal form in
north and western Europe.
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Four Corners aka sin nombre virus

• Outbreak began in 1993 in Four Corners area of
  US southwest with three unexplained deaths
  from pulmonary illness amongst local Navajo
  population.
• Virus identified by CDC as a type of hantavirus.
• Virus endemic in deer mouse populations across
  western states and interior BC.
• Symptoms include high fever, coughing and other
  flu-like symptoms.
• Death rate following infection now reduced to
  40.

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Ecology of a Sin nombre (Hantavirus) outbreak
Control? Keep mice out of, and away from
buildings.