Rubber plantations and Mosquito borne Diseases

Rubber Plantations and Mosquito Borne Diseases: An experience from Kerala, India: 

Rubber Plantations and Mosquito Borne Diseases: An experience from Kerala, I ndia Dr. P.K. Sumodan Assistant Professor Post Graduate Department of Zoology Government College Madappally, Kerala, India

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About Kerala

The Legend: 

Kerala was reclaimed from the ocean by ‘Parasurama,’ The 6 th incarnation of Hindu God Vishnu using his Axe The Legend

The land of coconut: 

The land of coconut

Political map of Kerala: 

Political map of Kerala

Vital statistics: 

Kerala is one of the 28 states in India. Area - 38,863 sq km Lies between longitudes 74° 52' and 76° 07' E and latitudes 11° 40' and 12° 48' N. Population in 2011: 33,387,677 (33.33 million) Bordered by Western Ghats on the east and Arabian Sea on the west Vital statistics

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Rubber plantations in Kerala

History: 

First rubber plantation- 1902 at Thattekkadu in Central Kerala by Europeans (Periyar syndicate owned by JJ Murphy, J A Hunter, K E Nicoll and CMF Ross) They used Para Rubber ( Hevea brasiliensis ) By 1914 it replaced all other species ( Tharian George et al, 1988 ) Indigenous species Ficus elastica History

Malabar migration: 

Starting from 1914, there was a massive migration from south central Kerala (Central Tranvancore) to North Kerala (Malabar) in search of virgin land Majority of them were Christians Migration peaked in the 1950s They spread rubber plantations to north Kerala Malabar migration

Statistics (2009): 

Total area: 517475 (0.5 million) Hectares Holdings (20 hectares and below): 480240 (92.80%) Estates: (Above 20 hectares ): 37235 (7.20%) Tapped area: 401706 hectares (77.63%) (Source: Indian Rubber Statistics Vol. 33, 2010) Statistics (2009)

Rubber vs Coconut (Hectares): 

Rubber vs Coconut (Hectares)

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Mosquito Borne Diseases in Kerala

Average number of cases per year (2006-2010): 

Average number of cases per year (2006-2010) Lymphatic filariasis (reliable data not available)

First outbreaks: 

Malaria – Not known Lymphatic filariasis- Not known Japanese Encephalitis- 1996 Dengue- 1997 Chikungunya-2006 First outbreaks

Vectors: 

Malaria- Anopheles stephensi, Anopheles culicifacies, Anopheles fluviatilis Lymphatic filariasis- Culex quinquefaciatus, Mansonia uniformis, Mansonia annulifera Mansonia indiana Dengue- Aedes albopictus, Aedes aegypti Chikungunya- Aedes albopictus, Aedes aegypti Japanese Encephalitis- Culex vishnui group Vectors

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Mosquito borne Diseases and Rubber Plantations

Potential Mosquito breeding sites in rubber plantations: 

Plastic containers (300-500 ml) are used for collecting rubber latex There are 500 trees per hectare Potential Mosquito breeding sites in rubber plantations

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During south west monsoon (June-September) two types of rubber plantations are observed in Kerala 1. Under active tapping using rain guards and 2. Where tapping is suspended

Rainfall in Kerala inmm-2010(Source: India Meteorological Department): 

Rainfall in Kerala inmm-2010(Source: India Meteorological Department)

Latex collecting containers with rainwater : 

Latex collecting containers with rainwater

Factors promoting mosquito breeding: 

Source of food: Carbohydrates present in the latex and decaying leaves promote bacterial growth Attraction: Black color of the containers are attractive to mosquitoes Blood source in the vicinity Factors promoting mosquito breeding

Mosquito breeding: 

Mosquito breeding

Mosquito breeding in rubber plantations (Based on studies in 3 districts from 2005-07): 

DISTRICT NO. OF BREEDING SITES SURVEYED NO. POSITIVE FOR BREEDING (%) KANNUR 4832 4768 (98.7) WAYANAD 2466 2178 (88.7) KOZHIKODE 3862 2822 (73.1) Mosquito breeding in rubber plantations (Based on studies in 3 districts from 2005-07)

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S.No . Mosquito sp. Breeding status Kannur Wayanad Kozhikode 1 Aedes . ( Stegomyia ) albopictus Y Y Y 2 Ae .( Stegomyia ) subalbopictus N Y N 3 Ae . ( Finlaya ) chrysolineatus N Y 4 Ae . ( Finlaya ) cogilli Y Y Y 5 Ae . ( Finlaya ) gubernatoris Y Y N 6 Ae . ( Finlaya ) harveyi Y N Y 7 Armigeres . ( Armigeres ) subalbatus Y Y Y 8 Culex ( Eumelanomyia ) brevipalpis Y Y Y 9 Cx . ( lophoceraomyia ) uniformis Y N Y 10 Heizmannia ( Heizmannia ) chandi Y N Y 11 Toxorhynchites ( Toxorhynchites ) splendens Y N N 12 Verrallina sp. N Y N

Vector species: 

Aedes . ( Stegomyia ) albopictus - Dengue and Chikungunya Armigeres ( Armigeres ) subalbatus - 1 . Incrminated as vector of Wuchhreria bancrofti (Tanaka et al 1979) 2. Susceptible to JE virus (Wei-June et al, 2000) 3. Vector of Dog heart worm, Dirifilaria immitis (Cheong et al, 1981) Vector species

Aedes albopictus: 

Aedes albopictus

Outbreaks near rubber plantations: 

1997- Dengue outbreak in Kottayam district 2001- Dengue cases in Kannur district 2008- Chikungunya outbreak in Kottayam district 2007- Dengue cases in Kozhikode district 2007- Chikungunya outbreaks in Malappuram and Kozhikode districts In all the above cases Aedes ( Stegomyia ) albopictus was the vector Outbreaks near rubber plantations

Reasons for suspension of tapping: 

Heavy rainfall Price of rubber Productivity Cost effectiveness (Productivity, labor charge, cost of rain guard, rubber price) Tappers employed on daily wage in small plantations versus regular tappers in estates Possibility of fungal diseases Belief of the planters that tapping during rainy season could reduce the life span of the trees Reasons for suspension of tapping

Suspension of tapping vs productivity and type of plantations : 

Suspension of tapping vs productivity and type of plantations

Suspension of tapping vs Rubber price (Kozhikode dist.): 

Suspension of tapping vs Rubber price (Kozhikode dist.)

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Possible control strategies

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1. Encouraging tapping during rainy seasons using rain guards 2. Source reduction by Educating the planters 3. Biological control using predator and competing mosquito species

Effect of Toxorhynchites splendens on the mosquito immature densities in Nilappuram estate of Kannur district : 

S.No . Species No. positive Average Per site density of Toxorhynchites splendens Per site density of other mosquitoes Larva Pupa Larva Pupa 1 Tx . splendens alone 43 1.5 0.1 0 0 2 Tx . splendens along with other mosquitoes with other species 19 1.0 0.1 14 0.1 3 Without Tx . splendens 25 0 0 42 8 Effect of Toxorhynchites splendens on the mosquito immature densities in Nilappuram estate of Kannur district

Dominant species: 

District Dominant mosquito species Contribution to per site density of immature stages Dominant species Aedes albopictus Kannur Heizmannia chandi 44-66% 31-41% Wayanad Aedes chrysolineatus 68-74% 21-32% Kozhikode Culex uniformis 47-50% 18-39% Heizmannia chandi 32-70% 18-24% Dominant species

Published works: 

Published works Mosquito- Breeding in the Rubber Plantations of Kerala, India: A study based on Ecosystem Approach , VDM VERLAG, 2010, Germany pp 64 Potential of Rubber Plantations as breeding source for Aedes albopictus in Kerala, India. Dengue Bulletin. 2003, 27: 197-198.

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Thank you sumodan@indiatimes.com