A. Kajatheepan

R. Ramasamy

S.N. Surendran

Journal of Vector Borne Diseases

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J Vect Borne Dis 44, March 2007, pp. 65–68Short Research CommunicationsSocio-environmental factors and sandfly prevalence in Delft Island,Sri Lanka: implications for leishmaniasis vector controlS.N. Surendrana, A. Kajatheepana & R. RamasamybaDepartment of Zoology, Faculty of Science, University of Jaffna, Jaffna, Sri Lanka, bInstitute of Medicine, University ofBrunei Darussalam, Gadong, Brunei DarussalamKey words Biting menace –  Delft Island – leishmaniasis – Phlebotomus argentipes – sandflies – Sri LankaSri Lanka was free of any form of leishmaniasis un-til recently. The first autochthonous case of cutane-ous leishmaniasis (CL) was only detected in 19921.By the year 2002, 65 cases, mainly from northerndry zone, were reported2. Leishmania donovanizymodeme MON-37 was identified to be responsiblefor CL in Sri Lanka3, though L. donovani is moretypically associated with visceral leishmaniasis (VL).In neighbouring India anthroponotic CL (ACL) ismainly caused by L. tropica and is vectored by Phle-botomus sergenti and P. papatasi4. In Sri Lanka thepresence of  P. argentipes, the well known vector ofVL caused by L. donovani in the Indian subcontinent,has been reported for many years5–7. However, thepresence of P. sergenti and P. papatasi has not beenreported so far from Sri Lanka.Delft Island lies in the Palk strait, 37 km from thecoast of Tamil Nadu state in India where kalar-azar(a form of VL) caused by L. donovani is endemic.There was a request from the health officers in DelftIsland to the Jaffna Health Services to take necessaryaction to control severe insect biting nuisance in early2004. In mid-May 2004, flies were collected in DelftIsland using human landing catches (HLC) and cattlebaits. Later, the collected flies were identified assandflies with P. argentipes as the predominant spe-cies8. In early 2005, three patients from northernmainland were diagnosed with CL. In May 2005, thepresence of morphospecies B of P. argentipes, whichis more associated with VL caused by L. donovanithan morphospecies A in India9  was detected in DelftIsland10.  These developments prompted the healthauthorities in Jaffna to carry out a single indoor re-sidual spray (IRS) in Delft Island in June 2005. In thiscontext, a questionnaire-based study was carried outamong the residents of Delft Island to assess theirperception of sandflies and knowledge of leishmania-sis transmission and also to determine factors thatinfluence sandfly biting frequencies.Sandfly specimens were collected from a westernarea of Delft Island (9:32N 79:41E). Collections weremade in two adjacent houses on a single day in mid-May 2004 and in the months of May, July and Augustof 2005 using HLC. Due to logistical problems HLCwere carried out from 2000–2200 h.In addition, a questionnaire and accompanying inter-views were carried out in July/August 2005 in the in-habited western and eastern sectors of Delft Island(9:31:35N, 79:41:26E).  These were designed to elicitfour types of information: (a) demographic informa-tion; (b) knowledge about sandfly and leishmaniasis;(c) attitude towards and steps taken to prevent sandflybiting; and (d) details of the dwellings that could in-66 J  VECT  BORNE  DIS  44, MARCH 2007fluence sandfly breeding.  Details investigated in-cluded: house type, monthly income, occupation ofthe respondent, educational qualifications, sandflyand its role in disease transmission, perceived sever-ity of sandfly biting, knowledge of conditions idealfor sandfly breeding, sandfly biting times, sleepinghabits, measures taken against sandfly biting andtheir cost. The questionnaires were prepared in Tamil,the local language and were administered by univer-sity undergraduates and health workers with second-ary education.In mid-May 2004, during two hours collection from2000–2200 h, 154 flies were collected. In mid-May2005, during similar collections, 162 sandflies werecollected. After the June 2005 IRS, however, nosandfly could be collected during similar collectionsin mid-July and August 2005.Chief of occupants, 59 males and 49 females, of ran-domly selected 108 house-holds (10% of the totalhouse-holds in Delft Island) were interviewed.Seventy-nine percent of the respondents were dailypaid workers and had a monthly income <LKR 5000(≈US$ 50). Forty percent had their education up toYear 8 and 43% studied up to Year 10. Forty-fivepercent of the respondents travelled to the Jaffnamainland once a week and 51% at least once in amonth. Of the travellers, 39% reach the mainland topurchase essential commodities and 31% for medi-cal treatment. The type of dwellings in Delft Island,that has an impact on sandfly biting is presented inTable 1.Ninety-three percent of those interviewees cate-gorised the biting by sandflies as severe, and the restas a moderate nuisance in the period before the June2005 IRS. They agreed that this IRS had reduced thebiting intensity. Knowledge on possible sandflybreeding sources is given in Table 2. Sixteen percenthad knowledge of more than one possible breedingsite and  30% however, had no knowledge of thepossible breeding sites of sandflies. Biting activity ofsandflies was reported to be in the evening by 2%,midnight 41%, early morning 8% and throughout thenight 49%. None of the respondents reported daytimebiting, were aware of leishmaniasis, or its symptoms,and all were unaware of the prevalence of leishma-niasis in mainland Sri Lanka and Tamil Nadu (India).Eighty percent did not think that parapet-walls orboundary walls made of coral were good breedinggrounds for sandflies. Forty percent were unaware ofthe high density of sandflies in the island. Interest-ingly, 28% of the interviewees believed that sandflieswere introduced into the island during the Britishcolonial period (before 1947) to destroy Opuntia sp,a cactus that encroaches arable and pasture lands.Eighty-four percent of the respondents stated thattheir family members slept on the floor and not beds.Fifty-one percent of the respondents’ family membersslept on the floor of the open verandah during theTable 1. Type of houses where the respondents dwellType of houses No. ofrespondentsFloor-cement, wall-cement, roof-tiles 57 (52.8)Floor-cement, wall-cement, roof-cadjan leaves 15 (13.9)Floor-mud, wall-cement, roof-cadjan leaves 8 (7.4)Floor-mud, wall-mud, roof-cadjan leaves 27 (25)Floor-cement, wall-cement, roof-asbestos 1 (0.9)Figures in parentheses are percentages.Table 2. Knowledge on sandfly breeding sourceType of breeding source No. ofrespondentsMoist soil 31 (28.7)Caves 4 (3.7)Cervices in the mud-floor 22 (20.4)Coral stones used to construct parapet-wall 19 (17.6)None of the above 32 (29.6)Figures in parentheses are percentages.SURENDRAN et al :  SANDFLY MENACE IN DELFT ISLAND, SRI LANKA 67night, whilst 48% on the floor indoors. Eighty-fivepercent of the interviewees used one personal protec-tion measure against sandfly bites. The commonpersonal protection measures were the use of mosqui-to coils and mosquito nets not treated by insecticides(Table 3). However, nearly 23% employed more thanone personal protection measure against sandflybites. Among the mosquito net users, 36% had onlyone net for the whole house-holds where averagemembers in the family was five. This indicates the in-adequate protection to all members in the family.Nearly 57% of the respondents agreed that sandflybiting had occurred throughout the year. However,only 54% employed personal protection measuresdaily. This shows all of the inhabitants are exposed tosandfly bites frequently. The cost of personal protectionagainst insect bites, ranged  from 1% (57% spent<LKR 50) to 2% (33% >LKR 100) of the total month-ly income.CL is an emerging vector-borne disease in Sri Lanka.No study had been reported so far to assess localknowledge on CL and personal protection measuresagainst sandfly bites by residents in areas of the coun-try where CL can be transmitted. While most respon-dents perceived sandflies as a biting nuisance they didnot suspect them as potential vectors of disease inDelft Island. There was no awareness of leishmania-sis itself, and this ignorance is likely to be widespreadin the northeastern province. If sandflies are notrecognised as important in the transmission of leish-maniasis, the villagers will not take sufficiently strin-gent measures to protect themselves against theirbites. Although no case of CL had been reported frompermanent Delft Island residents, there is a seriousrisk of infecting the vector population on Delft Islandwith L. donovani arriving from mainland Sri Lanka.The disease may also not be easily recognised amongthe residents since the medical community in SriLanka has become aware of local occurrence of thedisease only recently. Hence, there is a clear need toeducate the people of Delft Island, and also probablyother areas of the northeastern dry zone, on the roleof sandflies in the transmission of leishmaniasis.Floors and plinths of houses, soil at the edges of heapsof refuse, and soil at the bases of stone walls are goodbreeding sites for the sandflies6. In the mid-May 2005study, sandfly larvae were identified in the crakes ofmud floor of 3/10 houses inspected (unpublisheddata). The cervices in the uniquely constructed para-pet-walls made of local coral-stones also provide asuitable environment for the immature forms in theDelft Island6. In addition, the environment in DelftIsland is conducive for propagation and breeding ofsandflies. The high humid and dry gray loam soil(suitable for extensive growth of pasture grass) withforest cover favours, in addition to the life style of theinhabitants, the high prevalence of P. argentipes inDelft Island. As there is the potential for a resurgenceof the sandlfly population, with the attendant dangerof CL, in Delft Island the IRS needs to be performedat regular intervals, accompanied by continuous sur-veillance of the sandfly populations.AcknowledgementThe assistance of S. Kannathasan and A. Muru-gananthan, Department of Pathology, Faculty ofMedicine, KFA. Sangeefkumar, Faculty of Science,University of Jaffna, Regional Malaria Officer andTable 3. Personal protection measures used by therespondentsMethods No. ofrespondentsMosquito coil 52 (48.2)Evaporating repellents 0Mosquito net 45 (41.7)Electric fan 1 (0.2)Smoke 2 (1.9)Net made up of clothes 7 (6.5)Spring oil on the floor 1 (0.9)Figures in parentheses are percentages.68 J  VECT  BORNE  DIS  44, MARCH 2007members of the Entomology team, and Dr. W.Suwonkerd, former Consultant Entomologist, WHOare gratefully acknowledged.References1. Athukorale DN, Seneviratne JKK, Ihalamulla RL,Premaratne UN. Locally acquired cutaneous leishmaniasisin Sri Lanka. J Trop Med Hyg 1992; 95: 432–3.2. Siriwardena HVYD, Udagedara CU, Karunaweere ND.Clinical features, risk factors and efficacy of cryotherapyin cutaneous leishmaniasis in Sri Lanka. Cey Med J  2003;48: 10–2.3. Karunaweera ND, Pratlong F, Siriwardena HVYD,Ihalamull RL, Dedet JP. Sri Lankan cutaneous leishmaniasisis caused by Leishmania donovani zymodeme MON-37.Trans R Soc Trop Med Hyg 2003; 97: 380–1.4. Kalra NL, Bang YH. Sandfly vector competence fortransmission of Leishmania parasite in tropical Asia. JCom Dis 1986; 1: 28–34.5. Lewis DJ. The Phlebotomine sandflies (Diptera: Psy-chodidae) of the Oriental region. Bull Br Museum (NaturalHistory) (Entomology) 1978; 37: 277–343.6. Carter HF,  Antonipulle P. Observation on sandflies(Phlebotomus) in Delft Island, North Ceylon. Ann TropMed Parasitol 1949; 43: 62–73.7. Lane RP, Pile MM, Amerasinghe FP. Anthropophagy andaggregation behaviour of the sandfly Phlebotomusargentipes in Sri Lanka. Med Vet Entomol 1990; 4: 79–88.8. Surendran SN, Karunaratne SHPP, Adams Z, HemingwayJ, Hawkes NJ. Molecular and biochemical characterisationof a sandfly population from Sri Lanka: evidence for in-secticide resistance due to altered esterases and insensitiveacetylcholinesterase. Bull Entomol Res  2005; 95: 371–80.9. Ilango K, Srinivasan VDR, Sadanand AV, Lane RP.Phlebotomine sandflies (Diptera: Psychoidae) of TamilNadu and Pondicherry, southern India, in relation tovisceral leishmaniasis. Ann Trop Med Parasitol 1994; 88:413–31.10. Surendran SN, Kajatheepan A, Hawkes NJ, RamasamyR. First report on the presence of morphospecies A and Bof Phlebotomus argentipes sensu lato (Diptera: Psycho-didae) in Sri Lanka – implications for leishmaniasis trans-mission. J Vect  Borne Dis 2005; 42: 155–8.Corresponding author: Dr. S.N. Surendran, Department of Zoology, Faculty of Science, University of Jaffna, Jaffna, Sri Lanka.Email: noble@jfn.ac.lkReceived: 10 April 2006 Accepted in revised form: 18 October 2006

Socio-environmental factors and sandfly prevalence in Delft Island, Sri Lanka: implications for leishmaniasis vector control

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Socio-environmental factors and sandfly prevalence in Delft Island, Sri Lanka: implications for leishmaniasis vector control

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