Beg, M A

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eCommons@AKUDepartment of Pathology and Laboratory Medicine Medical College, PakistanJanuary 2000Risk of imported filariasis in PakistanM A. BegAga Khan UniversityFollow this and additional works at: https://ecommons.aku.edu/pakistan_fhs_mc_pathol_microbiolPart of the Microbiology Commons, and the Pathology CommonsRecommended CitationBeg, M. A. (2000). Risk of imported filariasis in Pakistan. Journal of Pakistan Medical Association, 50(1), 33-35.Available at: https://ecommons.aku.edu/pakistan_fhs_mc_pathol_microbiol/991Risk of Imported Filariasis in PakistanMohammed Asim Beg ( Department of Microbiology, The Aga Khan University, Karachi. ) Introduction Human filariasis is a chronic and debilitating disease affecting over 120 million humans which causesextensive morbidity but little mortality1. Clinical filariasis is widespread in the developing countries ofAfrica, Asia and South America. In particular four species are of importance:Onchocerca volvolus, which causes onchocerciasis (river blindness), is transmitted by the blackflySimulium and affects approximately 18 million people, about 300,000 of whom are blind; Wuchereriabancrofti, Brugia malayi and B.tirnori, all of which cause lymphatic filariasis, are transmitted byvarious species of mosquitos and affect approximately 90 million people in over 76 differentcountries2.Other known filarial parasites of humans are Loa loa, Acanthochièlonema ozzardi,A.perstans and A.streptocerca. Zoonotic infections may also occur from time to time e.g. Dirofilariaimmitis and B.pahangi.Adult filarial worms are vector borne, obligate extracellular parasites of their definitive hosts andbelong to one of two families, the Filariidae and Onchocercidae, which comprise the superfamilyFilarioidea of the phylum Nematoda3. In both cases microfilariae are ingested by blood-sucking vectorsin which they moult twice to become infective larvae, these are transmitted to the new host when theinsect bites again.Filarial infection and in particular lymphatic filariasis has a wide spectrum of clinical disease thataffects individuals of endemic regions4. The presentation is diverse with individuals having no clinicalmanifestations (asymptomatic) or microfilariae, patients being asymptomatic with microfilariae orthose having bouts of filarial fevers or displaying gross lymphatic obstruction. At the extreme end ofthis clinical spectrum however lies the Tropical Pulmonary Eosinophilia (TPE) syndrome. This ischaracterized by lymphadenopathy, asthmatic bronchitis, hypereosinophilia and an increase in theproduction of antifilarial immunoglobin antibodies5. Diagnosis of filariasis is important not only for theidentification of infected individuals and their subsequent treatment but also as a tool forepidemiological mapping. This topic has been comprehensively covered by Taylor and Denham in theirreview6. Since then new antigen detection techniques have been developed which do not require nightblood sampling and rely on serology, making epidemiological studies much easier7.Disease status in Pakistan and Neighbouring countriesLymphatic filariasis is unevenly distributed in the Southeast Asian Region but it is generally more arural problem. Due to vastness of some of these countries and poor accessibility of many areas,coverage of filariasis surveys have been inadequate. Reports of the endemicity in many areas are henceunderestimates of the actual situation. The situation in several countries including Vietnam, Laos,Cambodia, Thailand, Malaysia. Singapore. Indonesia and Philippines was reviewed by Mak8. This is avaluable reference as it gives a historical perspective on filarial infections in the region.Geographically Pakistan is not surrounded by filaria endemic countries except India. China which hada filariasis problem, successfully initiated a national campaign against lymphatic filariasis in the late1950’s. Epiderniological surveillance since 1984 indicates that the transmission of infection has beeninterrupted using simple Diethylcarbamazine therapy and effective control has been achieved9-11.Lymphatic filariasis is a major health problem in India12,13 particularly in the southern regions. A studyfrom a Bancroftian filariasis endemic area in Pondicherry14 discussed the infection dynamics andsupported a central role for worm burden in the initiation and progressions of chronic filarial disease.Functional impairment as a result of lymphatic filariasis in Tamil Nadu, South India15 showed that 66%patients of filariasis confirmed that their lives had been adversely affected. Thus the economic effectsand productivity loss of this disfiguring disease has been greatly underestimated.A study in Pondicherry16 compared the ti-end of prevalence and spectrum of manifestations ofBancroftian filariasis disease. The surveys conducted in 1957, 1986 and 1992 showed the overallprevalence of filarial disease as 4.7,   6.7 and 9.9% respectively showing that it was still a significanthealth problem.The situation in Pakistan however is very different. Because of inadequate availability of informationthe actual prevalence of disease is not known. According to Ahmed17, lymphatic filariasis due toW.bancrofti and B.malayi did not exist in Pakistan prior to 1947 (partition from india), except for a fewisolated cases. It was however endemic in former East Pakistan presently Bangladesh18. Resultsshowed a mean microfilaria infection rate of 16.8% with clinical manifestations present in 10.1% of thesampled population. The endemicity rate was 24.2%, which suggested that filariasis was a significantpublic health problem in Thakurgaon region, Dinajpur District, of former East Pakistan. A ten yearhistory of infection was a prerequisite for the clinical manifestations of filariasis to become apparent.Other workers19 also reported similar infection rates for this region and discussed the various spectra offilatial disease with relevance to urban and rural settings.Entomological studies showed the principal vector for bancroftian filariasis is Culex pipiens fatigans20and there was a suggestion that the infective larvae were present in the mosquito for a specific timeperiod, which correlated w itli optimum environmental conditions needed for transmission. This was anusual finding for a highly endemic area, according to the criteria set by Acton and Rao21. Pani et al22stated that vector infection rate may be used as an indicator for rapid assessment ol human infection.Geographically Pakistan is not surrounded by filaria endemic areas except India. However, during massimmigration from former East Pakistan in 1974, many immigrants from endemic areas settled in urbanareas of Sind particularly Karachi. Furthermore, the rapidly changing political and economic conditionsin the region and the continous rural - urban drift of population to the major cities may have created anew focus of transmission. In addition Culex quinquefasciatus, the ubiquitous vector for bancroftianfilariasis, is abundant in Pakistan. Southgate23 has emphasized the importance of low-densitymicrofilaraemia coupled with the ability of Culex spp. to transmit infection as a major risk factor forpropagating filariasis.Imported filariasis has been well documented and several studies have shown that individuals fromendemic regions of filariasis pose a theoretical risk of transmission to the indigenous population.Kirsch, et al24 showed that immigrants to Germany had microflaraemia; of the 1925 patients examined,78(4.1%) were positive for microfilaria. The presence of W.bancrofti, B.malayi and A.perstans wasconfirmed. Similarly Yangco, Vincent et al25 reported on a filariasis survey among Haitian immigrantsand Southeast Asian refugees residing in Florida USA. Microfilarae were detected only in Haitians,with 6.7% positive for W.bancrofti and 1 .3% positive for Mansonella ozzardi.Recently, Omar26 has confirmed bancroftian filariasis among South East Asian expatriate workers inSaudia Arabia, with microtilaraemia of 3.5% among Indian male workers. He also succeeded intransmitting the infection to laboratory bred Culex pipens mosquitoes and this was the first report everto show that local mosquitoes had the potential to act as vectors of bancroftian filariasis. Omar26 alsodiscussed the dangers of imported filariasis and more importantly the establishment of a self-sustainedfocus of disease which was likely to depend on the presence of microfilaraemic carriers and asusceptible population of vector mosquitoes.A study of repatriated Biharis from former East Pakistan27. now Bangladesh, showed that in a sampleof 1.101 people above one year of age. 9.0% were infected with W.bancrofti. The infection rate wassignificantly higher in males 10.2%, than in females 6.7%. Most importantly the mosqu toes, Cu lexpipiens fatigans collected in the vicinity of the camps were positive for infective larvae andtransmission was observed in the hottest and driest months. Thus, favorable climatic conditionscoupled with a constant source of microfiariae provided the perfect conditions for filarial transmissionto occur. A brief filariasis survey conducted by Wolfe and Khan28 also highlighted the obvious dangersof imported filariasis in Pakistan and recommended that further investigations were needed.Are we at risk?Filariasis is one of the most enigmatic helm inthic infections of medical importance and presents achallenge to the profession. With significant migration of people in the last two decades, the foci ofendemicity for filarial disease may have been modified greatly in Pakistan and therefore in this reviewwe have attempted to highlight the need for reexamination and further study of filarial infection in thecountry. It would be very useful to get suitable information from hospital records which would give anapproximate idea of the disease prevalence in the indigenous population.Serological studies would be helpful in diagnosing the population actually exposed to the infection.Detailed questionnaires could be administered to the patients to assess whether infection was acquiredlocally or from endemic countries. We can then undertake indepth epidemiological studies,encompassing both blood surveys as well as entomological investigations to determine the exact statusof filariasis in Pakistan. The dangers of imported filariasis thickly populated areas like Karachi need tobe investigated to shed light on possible transmission patterns and host susceptibility to infection.References 1.Nelson OS. Current concepts in parasitology. Filariasis N. Lug!. J. Med.. 1979:300:1136-12.2.World Health Organization Tropical l)iseascs Research 1989- 1990. Geneva, W.H.O, 1991: pp. 1-135.3.Yamaguti S. The nematodes of vertebrates. In : System a H elminthon vol.3 (Part 1 and II). New Yorkand London, lnterscience Publishers Inc, 1961, pp. 1261.4.Ottesen EA. Imirninopathology of lymphatic filariasis in man. Springer Sem in. in Immunopathol., I980;2:373-85.5.Hussain R, Hamilton RG, Kumaraswami V, et al. IgE responses in human filariasis I. Quantificationof filarial-specific IgE. J. of immunol, 198 1; 127: 1623-29.6.Taylor AER and Denham DA. Diagnosis of Filarial Infection. Trop. Dis. Bull., 1992; 89:2.7.Weil GJ., Lammic PJ and Weiss N. The ICT filariasis test: A rapid-fonnat antigen test for diagnosis ofBancroftian filariasis. Parasitol Today, 1997;13:401-4.8.Mak 3W. Filariasis in Southeast Asia. Ann. Acad. Med., 198 1;10:1 12-19.9.Cao W, Van-der-Ploeg. CP, Ran Z, et al. Success against lymphatic filariasis. World Health Forum,1997; 18:17-20.10.Chung-Kuo-Chi-Shcng-Chung-Hsueh-Yu-Chi et al. A great success in lymphatic filariasis control inChina. National Technical Steering Group for Filariasis Control and Research, MOPH. 1995;13:88-85.11.Zhang S., Cheng F and Webber R. A successful control programme for lymphatic filariasis in Hubci,China. Trans-R-Soc-Trop-Med-Hyg, 1994;88:5 10-20.12.Sass M. Human filariasis a global survey of epidemiology and control. Tokyo: University of TokyoPress, 1976, pp. 663-734.13.Rao CK, Shanrma SP. Control of fmlariasis in India. J. Commun. Dis., 1986; 18:276-82.14.Chsn MS. Srividya A, Nonuan RA, et at. Epifil: A dynamic model of infection and disease inlymnphatic filariasis. Ama. 3. Trop. Mcd. Hyg., 1998;59:606-14.15.Ramaiah KD, Ktanar KN, Ramu K, et at. Functional impainaent caused by lymphatic filariasis inrural areas of south India. Trop Med tat Health, Sep; 1997;2:832-38.16.Surrendran K, Pani SI’, Sommdarssanane MB, et al. Natural history, trend of prevalence andspectrum of manifestations of Bancrofmian filarial disease in Pondieherry (South India). Acts. Trop., I196:61:9-18.17.Ahmed SS. Filariasis in Sind. J. Pak. Mcd. Assoc., 1971:21:167-72.18.Bany C, Ahmed A, Khan AQ. Endemic filariasis in Thakurgaon, East Pakistan, Ant. J. Trop. Med.Hyg., 1971;20:592-97.19.Wolfe MS attd Khan MA. Bancroftian fitariasis in two villages in Dintmjpnr district, East Pakistan.I. Infections in nan. Am rop. Med. t-Iyg., 1972:21:22-29.20.Khan MA and Wolfe MS. Bancrnflian tilariasis in two villages in Dinajpur District, East Pakistan.II.Entomological investigations. Am. J. Trop. Med. Hyg., 1972;21:30-37.21.Acton HW and Rao 55. Factors which determine tIme differences in ttte types of lesions producedby Filaria bancrofli in India. Indian Med. Gazette. 1930:65:620-29.22.Pant SP, Srividya A, Krishnamoorthy K, et at. Rapid assessment procedures (RAP) for lymphaticfilariasis. NatI. Med. J. India, 1997:10:19-22.23.Southgate BA. TIme significance of low density microfilariasis in tIme transmission of lymphaticfilarial parasites. 3. Trop. Mcd. Hyg.. 1992:95:79-86.24.Kirsh WD, Ruble F, Stein Ilk. Fitariasis in foreign immigrants . Z. Gesamte Inn. Med., 985:40:720-22.25.Yangco GG, Vincemmt AL, Vickery AC. et at A sursey of Imlariasis among refugees in SouthFlorida. Am,J. Trop. Med. Hyg., 984:33:246-51.26.Omar MS. A survey of bancrofiiamm filariasis among South East Asian expatriate workers inSammdma Arabia. Trop. Mcd. Int. Health, 1996:1: 155-60.27.Khamm MA and Pervez SD, Imported tilariasis in Pakistan. Trsn. R. Soc. Trop. Med. Hyg.,1981;75:869-71.28.Wolfe MS and Khao MA. Fitariasis smmrvcy in Karachi. Trait. R. 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Risk of imported filariasis in Pakistan

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Risk of imported filariasis in Pakistan

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