Resurgent Vector borne diseases - In context of Bangladesh
Editorial: NMJ 2006, 15(2)
Dr. Md. Mujibur Rahman
The effects of globalization in exacerbating the risk of spreading infectious diseases are mediated not only through the movement of people but also by the increased mobility of disease vectors, livestock and other animals that may host zoonoses, as well as the greater propensity for food-borne disease in consequence of increasing legal and illegal trade. 1
In the 120 years since arthropods were shown to transmit human disease, hundreds of viruses, bacteria, protozoa, and helminthes have been found to require a hematophagous (blood-sucking) arthropod for transmission between vertebrate hosts). Historically, malaria, dengue, yellow fever, plague, filariasis, louse-borne typhus, trypanosomiasis, leishmaniasis, and other vector-borne diseases were responsible for more human disease and death in the 17th through the early 20th centuries than all other causes combined.2
Prevention and control programs are mainly based on controlling the arthropod vectors. However, the benefits of vector-borne disease control programs were short-lived. A number of vector-borne diseases began to reemerge in the 1970s, a resurgence that has greatly intensified in the past 20 years I. Although the reasons for the failure of these programs are complex and not well understood, two factors played important roles: 1) the diversion of financial support and subsequent loss of public health infrastructure and 2) reliance on quick-fix solutions such as insecticides and drugs. )
During controlling vectors, in addition to use of safe insecticides or taking other common measures, it should be emphasized upon the matter of migration of these vectors through vehicles from one country to other countries.
In context to Bangladesh, India can be major source of those new types of diseases like dengue. In India, dengue has been epidemic for several years.5 Although dengue fever was documented in Bangladesh from the mid-1960s to the mid-1990s, but an outbreak of dengue hemorrhagic fever has not been previously reported.4 But in 2000, through mid November 5,575 hospitalized dengue cases were reported to the Ministry of Health in Bangladesh,. with a case-fatality rate of 1.61 %.4, 6, 7
Ades mosquito, the vector of this disease, can not fly more than 100 meters from its residence 8. So, there is no way to move this vector from air port to populating area of Dhaka, where dengue outbreak started first in Bangladesh. Moreover, the air way communications from Bangladesh to India have been established many years before liberation but there was no dengue outbreak during this period. So, there is very little chance of transmitting the disease by this route. Moreover, under the WHO International Health Regulation (IHR), all international airports and seaports are kept free from all types of mosquitoes for a distance of 400 meters around the perimeter of the ports.8 But it is possible that, the infected mosquito can travel via bus or train under their seats, in between luggage and transmit the disease to other populating area nearby the stoppage. The time of emergence of
dengue outbreak in Bangladesh that occurred first in Dhaka coincides with period after the
introduction of bus communication between Dhaka and Kolkata. So it will be logical to claim that the infected vectors can easily migrate to Dhaka via bus from India. Now, the recent introduction of railway communication can exacerbate the condition or import of new diseases agents like Japanese B encephalitis, chikangunya which are known to prevalent in many areas of India. So, it should be an urgent matter to prevent such migration of vectors through vehicles like bus or train. The measures those can be taken to limit vectors migration could be as follows: 1) Before starting, the train or bus should make free from any vectors by using effective insecticides before the passengers take their seats. 2) The international train or bus should not be used for domestic purposes. 3) The stoppages for train or bus in both countries should be sufficiently away from localities and the area should be carefully monitored for vectors. 4) Traveler's quarantine should be strictly maintained. Our government should be aware of the factor of migration of infected vectors urgently. If it is ignored, it will be not so late when even a lay man will bother for uncommon diseases like Japanese B encephalitis, chikangunya or other uncommon vector borne diseases as like as dengue today.
References:
1. Weiss,R.A. and Mc Michael,AJ. (2004) in the emergence of infectious dieases. Nature Medicine 10, S70-S76.
2. World Health Organization. Dengue haemorrhagic fever: diagnosis, treatment,prevention and control (2nd edition). Geneva: World Health Organization; 1997.
3. Russell PK, Buescher EL, McCown JM, Ordonez J. Recovery of dengue viruses from patients during epidemics in Puerto Rico and East Pakistan. Am J Trop Med Hyg 1966;15:573-9.
4. Amin AAA, Hussain AMZ, Murshed M, Chowdhury lA, Mannan S, Chowdhuri SA, et al. Sero- diagnosis of dengue infections by haemagglutination inhibition test (HI) in suspected cases in Chittagong, Bangladesh. WHO Dengue Bull 1999;23:34-8.
5. Anuradha S, Singh NP, Rizvi SN, Agarwal SK, Gur R, Mathur MD. The 1996 outbreak of dengue hemorrhagic fever in Delhi, India. Southeast Asian J Trop Med Public Health 1998;29:503-6.
6. Yunus EB. Dengue outbreak 2000: the emerged issues. Bangladesh Med J (Khulna) 2000;33:46-7.
7. Mahbubur Rahman, Khalilur Rahman, A. K. Siddque et.al. First Outbreak of Dengue Hemorrhagic Fever, Bangladesh. Emerging Infectious Disease, CDC Vol. 8, No. July 2002.
8. K. Park. Park's Textbook of Preventive and Social Medicine. 16th edition, 2000. page 538-539.
