Impact of rodents

4 nights’ catch, 1917 Lascelles, Victoria, Australia

Impact of rodents

AgricultureField damage/reduced yield of staple crops

Loss, damage, contamination to stored crops

Health

Zoonosis – lassa fever, plague, leptospirosis

Yield of vegetable crops, marketability

Contamination – dysentery (Salmonella etc.)

PropertyBuildings, furniture, utensils, roads, wires, clothes, blankets, fishing nets …..

>750 million poor in rice-producing Asia!>750 million poor in rice-producing Asia!70% of the 70% of the

world’s poor world’s poor live in Asialive in Asia

Nutrition from rice (selected Asian countries, 1999)Nutrition from rice (selected Asian countries, 1999)

Sources: FAO online database (2001); World Development Report (2002); World BankSources: FAO online database (2001); World Development Report (2002); World Bank

0

10

20

30

40

50

60

70

80

Mya

nmar

Laos

Vie

tnam

Ban

glad

esh

Cam

bodi

aIn

done

sia

Thai

land

Phi

lippi

nes

Kor

ea

Chi

na

Mal

aysi

a

Indi

a

Japa

n

Wor

ld

Calories

Protein

Region Region and and populationpopulation

Rice Rice produced produced (tonne)(tonne)

Loss to Loss to rodents rodents (%)(%)

Rice eaten Rice eaten (kg/year)(kg/year)

People fed People fed per year if no per year if no rat lossesrat losses

IndonesiaIndonesia

210 million210 million

50,000,00050,000,000 1717 249249 33 million33 million (52% calories)(52% calories)

VietnamVietnam

80 million80 million

31,000,00031,000,000 3030 280280 8 million8 million

(67% calories)(67% calories)

AsiaAsia

3.6 billion3.6 billion

540,000,000540,000,000 55 150150 180 million180 million

(32% calories)(32% calories)

1010 360 million360 million

Rice field losses to rats Rice field losses to rats

Losses to rats in Bangladesh Losses to rats in Bangladesh

Field losses 10 – 20 % (up to 100% in some years)

Storage losses 5 – 10 % (can be > 200kg per house)

Foregone production ?

Other crop losses

Field losses 10 – 20 % (up to 100% in some years)

Storage losses 5 – 10 % (can be > 200kg per house)

Foregone production ?

Other crop losses

Damage Damage crops, stored crops, stored grain, clothes, grain, clothes, houseshouses

Loss of Loss of production production increases increases crop areacrop area

EnvironmentalEnvironmentalrisks from risks from poisonspoisons

Disease Disease impactsimpacts

Rats are the No. 1 pest affecting rice Rats are the No. 1 pest affecting rice production in many Asian countriesproduction in many Asian countries

Rodents and DiseaseRodents are vectors and reservoirs for more than 60 different diseases.

Hantavirus

The Plague

Leptospirosis

Rat Typhus (rickettsia)

Neuro-angiostrongyliasis (rat lungworm)

are five of the major rodent-borne diseases that commonly affect human populations in Asia

Why rodents?

Why are rodents important reservoirs and vectors of human disease?

Mammals with common physiology

Commensality with long “co-evolution” living in close proximity to humans

Generalist feeders exploiting waste and human/livestock food

Rodents can pick up and transmit more than 60 different diseases

Morbidity rate of Morbidity rate of LeptospirosisLeptospirosis by province, by province, NortheasternNortheastern region, region, Thailand Thailand 1996 - 20021996 - 2002

0- 2.40- 2.4 2.41 -152.41 -15

1919

9696

19971997 1919

9898

19991999

15.01 - 5015.01 - 50 > 50> 50Morbidity rate/100,000Morbidity rate/100,000

200020002001200120022002

W. Tangkanakul W. Tangkanakul et al. et al. 2005. 2005. SE Asian J Trop Med Public HealthSE Asian J Trop Med Public Health 36, 36,

YearYear CasesCases IncidenceIncidence

(/100,000) (/100,000)

DeathsDeaths

19961996 398398

19971997 23312331 3.43.4

19991999 60806080 9.89.8 266266

20002000 1428514285 23.723.7 362362

20012001 1021710217 16.416.4 171171

20022002 68646864 9595

Leptospirosis human epidemiology in ThailandLeptospirosis human epidemiology in Thailand

7 to 9 times more males affected7 to 9 times more males affected

71-84% farmers; most 25-54 years71-84% farmers; most 25-54 years

Peak incidence in Aug to Nov (rains)Peak incidence in Aug to Nov (rains)

Serotypes: australis, sejroe, pyrogenesSerotypes: australis, sejroe, pyrogenes

Higher incidence if villages had pot Higher incidence if villages had pot

holes in roadsholes in roads

Information on leptospirosis in Asian Information on leptospirosis in Asian countries is extremely limited.  countries is extremely limited.  

Little is known about:Little is known about:The status of rodent diseases in Asia The status of rodent diseases in Asia

that affect humans and/or their livestockthat affect humans and/or their livestockWhich rodents are key reservoir speciesWhich rodents are key reservoir speciesThe persistence of the infective parts of The persistence of the infective parts of

the disease life cycle in rice agro-the disease life cycle in rice agro-ecosystemsecosystems

Leptospirosis human epidemiology in ThailandLeptospirosis human epidemiology in Thailand

Leptospirosis & Typhus in Lao PDRLeptospirosis & Typhus in Lao PDR

In 2001-2003 at Mahosot Hospital in In 2001-2003 at Mahosot Hospital in

Vientiane, of 427 adults with unexplained Vientiane, of 427 adults with unexplained

fever, from serological evidence:fever, from serological evidence:

10% leptospirosis 10% leptospirosis

10% murine typhus 10% murine typhus

15% scrub typhus 15% scrub typhus

Main risk factor – time spent in flooded paddies

Health impacts of rodent diseasesHealth impacts of rodent diseases

Epidemics of rodent-borne diseases can have a Epidemics of rodent-borne diseases can have a significant impact on a local rural economy. significant impact on a local rural economy.

Zoonosis can cause disability at key times and lead to no Zoonosis can cause disability at key times and lead to no crop, a late crop, or reduced crop yield. crop, a late crop, or reduced crop yield.

In poorer communities, disability for a month at a key time In poorer communities, disability for a month at a key time may lead to no crop, a late crop, or reduced crop yield. may lead to no crop, a late crop, or reduced crop yield.

Rodent diseases can lead to a debt treadmill! Rodent diseases can lead to a debt treadmill!

The Plague

Etiologic agent Yersinia pestis - bacillus

Bubonic Plague: enlarged, tender lymph nodes, fever, chills and prostration.

Septicemic Plague: fever, chills, prostration, abdominal pain, shock and bleeding into skin and other organs

Pneumonic Plague: fever, chills, cough and difficulty breathing; rapid shock and death if not treated early

Pharyngeal and Meningitic Plague also documented

Discovery of new foci = based on human cases!World Distribution of Plague, 1970-2005Discovery of new foci = based on human cases!World Distribution of Plague, 1970-2005World Distribution of Plague, 1970-2005Importance of Plague in modern timesImportance of Plague in modern times

Transmission

flea bites

meat consumption

airborne

long distance transport

(a)

(b)(c)

Stenseth, N.C, Aikimbayev, A., Atshabar, B.B., Begon, M., Belmain, S.R., Bertherat, B., Carniel, E.,

Gage, K.L., Leirs, H. and Rahalison, L. (in press) Plague: Past, Present and Future. PLoS Medicine.

Surat, Surat, Gujarat, Gujarat, India, 1994India, 1994

Squalid high-density slum conditions and poor sanitation promote transmissionSqualid high-density slum conditions and poor sanitation promote transmission

Confusion fuelled by poor levels of information in government press statementsConfusion fuelled by poor levels of information in government press statements

Media reports unconfirmed/suspected cases, exaggerating death tollsMedia reports unconfirmed/suspected cases, exaggerating death tolls

Agricultural exports and cargo embargoed, export loss of more than $420 millionAgricultural exports and cargo embargoed, export loss of more than $420 million

Investor confidence plummets, $600 million to $3 billion loss to Indian economyInvestor confidence plummets, $600 million to $3 billion loss to Indian economy

45,000 people cancelled flights to India45,000 people cancelled flights to India

International migrant workers strandedInternational migrant workers stranded

Divali [Festival of Lights] cancelledDivali [Festival of Lights] cancelled

Official death toll was 56Official death toll was 56

Approx. 700 suspected casesApprox. 700 suspected cases

Speculation that it was not plague Speculation that it was not plague continues to this daycontinues to this day

SuratSurat

Urban outbreaks of Urban outbreaks of plague will happen plague will happen againagain

Can we learn from Can we learn from the past?the past?

Economic non-Economic non-disease costs can disease costs can be very highbe very high