"feeling under the weather?" bioweather

“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

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f out

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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)

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anoph

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(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

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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.