3Desert 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.
4juvenileeggsolitary hoppergregarious locustSource: BBC website
6Last major locust plague (1987-89) Outbreak:Drought in Africa in 1970’s and early 80’s produced a recession in the locust cycle.Heavy rains in In Jan 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 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 They reached as far west as Jamaica.
7Sudan - Ethiopia - Somalia -Eritrea) Upsurges in 1990’s: Local upsurge in Red Sea Basin (from Yemen - Saudi Arabia toSudan - Ethiopia - Somalia -Eritrea)
82004 outbreak a b c map of outbreak b) swarms in Mauritania Nov.CYPRUS,EGYPT2004 outbreakcmap of outbreakb) swarms in MauritaniaAerial spraying in the western SaharaSource: BBC website
9Monthly snapshots of outbreaks from Nov. 2003-Nov. 2004 gregarious adults gregarious juveniles
10Rainfall and the Australian plague locust Scale of outbreakSources: BBC website;
11Combating 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 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)
12Combating 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 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.
14Malaria (Ital: “bad air”) 1990’s: M people at risk300 M are infected M cases reported annually (85% in Africa; 7% in SE Asia)Deaths: M annuallyVector: Anopheles mosquito (50-60 spp of the 380 knownspecies 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
15Global incidence of malaria Map area equivalent to cases per 100 people (92% of all cases in Africa)Source:
17The 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.
18Role 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.
19Temperature-controlled development of Plasmodium 4P. malariae3Length of the life-cycle in anophelines (weeks)2P. falciparumP. vivax1optimalTemperature (°C)minimummaximum
21Sri Lanka (Ceylon): topography and annual precipitation (mm) 10001500>2000Summer monsoon
22Malaria 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 resulted in major epidemic in south.30% of population fell ill; 80,000 died. IllustratesRoss’s “math of malaria” (~25d fever cycle)1000100101casesdays
23The East African malaria resurgence: is climate change to blame? KerichoKabaleGikonkoMuhangaMonths suitable for P. falciparum transmissionHay et al., (2002) Nature 415,
25Geography of malaria risk in N. America (AD 2000)
26Disease and climate change: a future geography of malaria?
27The demise of malaria in the USA (1918-1946) Wetland drainage (e.g. by TVA)Public educationInsecticide (esp. DDT) spraying (4.5 M houses sprayed)
28Malaria resurgence ….. and decline Renewed campaign of spraying of DDT in housesIneffective therapies (e.g. quinine-based) replaced with artemisin combination therapiesIntensified surveillance and public education~ cases in South Africa~3 000 cases in South Africa
29Why was malaria widespread in northern Europe in the LIA? LittleIce AgeReiter has campaigned to show how public health meaures eradicated malaria from European countries (e.g. Scandinavia, Poland, Finland), and thatfrom: Reiter, P "From Shakespeare to Defoe: Malaria in England during the Little Ice Age” Emerging Infectious Diseases vol. 6
30Bilharzia (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.
32Bilharzia: flukes, intestinal worms and a severe symptoms (enlargement of the liver and spleen)
33Lyme DiseaseInfection 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.
34Deer ticks (Ixodes species) N.B. - The “dog tick” is not a member of the Ixodes genus and cannot spread Lyme disease
37Farm abandonment in early decades of last century. 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 years.Expansion of suburban development into rural areas around NYC-Boston.Reduced hunting of deer?
38Lyme disease and the ecology of oak-maple woodlands
39Climate and viral disease Viral disease transmissionEcology of flavivirus outbreaks(e.g. dengue, West Nile encephalitis)Ecology of bunyavirus outbreaks(e.g. sin nombre)
40Emerging virusesFamily Disease Vector and Reservoir
42Dengue (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).
43World distribution of Aedes aegypti and dengue fever epidemics
44Distribution of Aedes aegypti in the Americas 1995Prior to yellow fever eradication programme.After post-war yellow fever eradication programme.Two decades after eradication programme relaxed
45Distribution of dengue in the Americas 1981-1995Prior to 1981Distribution of dengue in the Americas
46West Nile virusWest 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.
53WNV cases - Canada *some related to travel outside province 200220032004200520062007Nova Scotia2**1**New BrunswickQuébec2017341Ontario3948913954212*Manitoba1425550578*Sask.9375*58191285*Alberta2721*1039318*BC20**19**Yukon/NWTCANADA4141481252251512215*some related to travel outside province**all related to travel outside province
54Total number of cases by state November, 2003Total number of cases by stateIs the WNV threatdeclining in N. America?November, 2007
55Resurgence 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)
56Ecology of a hantavirus* outbreak animalreservoir(esp. mice)faeces, urinehumansSymptoms 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.
58“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%.
59Ecology of a “Sin nombre” (Hantavirus) outbreak Control? Keep mice out of, and away from buildings.