“Feeling under the weather?” BIOWEATHER Pests : locust plagues Parasites : worms, flukes and spirochetes Diseases : ‘emerging’
Mar 28, 2015
“Feeling under the weather?”
BIOWEATHER
Pests: locust plaguesParasites: worms, flukes
and spirochetesDiseases: ‘emerging’
viruses
Locusts and grasshoppers
in Africa
Desert LocustsLocusts 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.
egg
juvenile
solitary hopper
gregarious locust
Source: BBC website
Last major locust plague (1987-89)
Outbreak: 1967-68. Drought in Africa in 1970’s and early 80’s 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.
Upsurges in 1990’s
1996-1998: Local upsurge in Red Sea Basin (from Yemen - Saudi Arabia to
Sudan - Ethiopia - Somalia -Eritrea)
2004 outbreaka) map of outbreakb) swarms in Mauritaniac) Aerial spraying
in the western Sahara
a b
c
CYPRUS,EGYPT
Nov.
Source: BBC website
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Monthly snapshots of outbreaks from Nov. 2003-Nov. 2004
gregarious adults gregarious juveniles
Rainfall and the Australian
plague locust
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Sources: BBC website; www.affa.gov.au; www.bom.gov.au/silo/products/cli_chg
Sca
le o
f out
brea
k
2004 plague
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)
Combating locustsBad 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 cooperate;The 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.
Malaria (Ital: “bad air”)
1990’s: 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
Global incidence of malaria
Map area equivalent to cases per 100 people (92% of all cases in Africa)
Source: www.worldmapper.org/posters/worldmapper_map229_ver5.pdf
The malaria transmission cycle I
http://www.cdc.gov/malaria/biology/life_cycle.htm
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.
The malaria transmission cycle II
http://www.cdc.gov/malaria/facts.htm
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 25-30°C the malarial parasites and mosquito larvae mature quickly, the adult mosquitoes live longer, and female mosquitoes feed more frequently.
Temperature-controlled development of Plasmodium
15 20 25 30Temperature (°C)
Len
gth
of
the life-c
ycl
e in
anoph
elin
es
(w
eeks
)
4
3
2
1
0
minimum maximum
optimal
P. malariae
P. falciparumP. vivax
Sri Lanka (Ceylon):topography and annual precipitation (mm)
1500
1000
>2000
Summer monsoon
Malaria epidemic Sri Lanka (Ceylon) 1934-5
Malaria hyperendemic in dry north of island but rarein 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. IllustratesRoss’s “math of malaria” (~25d fever cycle)
1000
100
10
10 25 50 75 days
case
s
The East African malaria
resurgence:
is climate change to
blame?
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Kericho
Kabale
Gikonko
Muhanga Hay et al., (2002) Nature 415, 905 - 909
Mo
nth
s su
itab
le fo
r P
. fa
lcip
aru
m tr
ansm
issi
on
Geography of malaria risk in N. America (AD 2000)
Disease and climate change:a future geography of malaria?
The demise of malaria in the
USA (1918-1946)
2005-6 ~10 000 cases in South Africa2006-7 ~3 000 cases in South Africa
Malaria resurgence ….. and decline
Why was malaria widespread in northern Europe in the LIA?
from: Reiter, P. 2000. "From Shakespeare to Defoe: Malaria in England during the Little Ice Age” Emerging Infectious Diseases vol. 6
LittleIce Age
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.
Bilharzia distribution
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.
Deer ticks (Ixodes species)
N.B. - The “dog tick” is not a member of the Ixodes genus and cannot spread Lyme disease
Lyme disease riskHighLowCanadaU.S.A.Mex.IxodespacificusIxodesscapularis
Number of cases of Lyme disease reported in US:1982- 1997
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?
Lyme disease and the ecology of oak-maple woodlands
heavy acorn cropattracts deer, provideswinter food for mice.Ticks breedmice BREEDNymphs and adult ticks to humans or deerNon-Mast Year (e.g. 1995)Larval ticks to mice;feed, move to shrubsmice emigrate
Mast Year (e.g. 1994)
Few acorns few deer few ticks in oak forests;deer stay in maple forests and mice migrate there because of over-population in oak forests
SpringTicksTicksTicksTicksSummer
ticksFallWinteroak
Climate and viral diseaseViral disease transmission
Ecology of flavivirus outbreaks(e.g. dengue, West Nile encephalitis)
Ecology of bunyavirus outbreaks(e.g. sin nombre)
Emerging viruses
Flavi- Yellow feverDengueEncephalitis
Mosquitoes (Aedes)Mosquitoes (Aedes)Mosquitoes+birds
Arena- Lassa feverMachupoJu nín
Aerosols+rodentsAerosols+rodentsAerosols+rodents
Bunya- HantafeverSabíaRift Valleyfever
Aerosols+rodents
Aerosols+rodentsMosquitoes+sheep & cattle
Filo- EbolaMarburgfever
direct? + monkeysmonkeys
Family Disease Vector and Reservoir
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 >20% of cases if untreated).
• DF cases common in humid (sub)tropical climates esp. in wet season (improved breeding success for Aedes).
World distribution of Aedes aegypti and dengue fever epidemics
1995
Distribution of Aedes aegypti in the Americas
After post-war yellow fever eradication
programme.
Two decadesafter eradication
programme relaxed
Prior to yellow fever eradication
programme.
1981-1995
Prior to 1981
Distribution of dengue in the Americas
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.
fever, aches, stupor, (brain lesions, coma, paralysis, death?)
direct transmission?
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
WNV cases - Canada
November, 2003
November, 2007
Total number of cases by state
Is the WNV threat
declining in N. America?
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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)
Ecology of a hantavirus* outbreak
Symptoms first noted in a Chinese medical text dating from about AD1000.
Major outbreak in Korean War (>2000 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.
animalreservoir
(esp. mice)humans
faeces, urine
“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%.
Ecology of a “Sin nombre” (Hantavirus) outbreak
High moisture availability(e.g. El Niño year)Large pine seed croprapid increase in deer micepopulation (x10 in 1995-6)Mice invadebuildingsViral outbreaksfrom breathingmouse “dust”thick snowpack
WinterWinterSummerSpring/Summer
Control? Keep mice out of, and away from buildings.