The Point of Entries (POEs) in India are obligated to meet requirements under the World Health Organization International Health Regulation 2005, to prevent the spread of vectors/reservoirs and vector borne diseases from one country to another. One of the areas stressed in the IHR-2005 is capacity building for vector surveillance and control at PoE and up to a minimum distance of 400 meters from those areas of POE facilities that are used for operations involving travelers, conveyances, containers, cargo, and postal parcels, with extension of the minimum distance if vectors with a greater range are present.
Routine entomological surveillance has been carried out at all POE in India for risk assessment, organizing evidence-based vector control programme to keep the vectors density below the threshold level and if necessary, invoking emergency measures to prevent the spread of vector-borne disease.
The vector dynamics are constantly monitored by the headquarters through seasonal vector surveys carried out at POEs by the central surveillance teams of National Centre for Disease Control (NCDC) and National Vector Borne Disease Control Programme (NVBDCP) of the Dte. GHS.
The International Health Regulations (2005) advocate achieving a vector-free zone at seaports, airports, and ground crossings and within a 400-metre perimeter around these entry points.
- Maintaining vector free status to reduce the risk of vector borne disease transmission
- Reduce transmission risk of pathogens imported with vectors/reservoirs
- Prevent dispersal of local vectors/reservoirs to other countries
- To prevent invasive species of vectors from establishing in local environments
- National or regional intersectoral cooperation for the implementation of integrated vector management
Diseases such as malaria, dengue, chikungunya, yellow fever, Zika virus, plague, leptospirosis, etc. are vector-borne diseases that pose major public health risks via PoE to a non-endemic area.
Vectors such as mosquitoes (Anopheles, Culex, Aedes and Mansonoid spp.), sandflies (Phlebotomus spp), rodents, flies (M. domestica), fleas (Xenopsylla spp), louse, ticks and mites are of high priority organisms that are kept under the threshold level to prevent disease transmission and distribution.
The vector surveillance plans for POE are based on the current epidemiological situations and risk assessment of importation/exportation of vectors and vector borne diseases at PoE. The surveillance activities are carried out routinely in all PoE and up to a minimum distance of 400 meters from those areas of POE with extension of the minimum distance if vectors with a greater range are present. Situation in and around PoE will continually evolve with respect to disease vectors, and seasonal variability may also influence disease transmission risk
- Under normal circumstances: A routine surveillance plan is followed.
- In epidemics/outbreaks: An emergency surveillance plan for rapid action is followed.
Vector control at PoE assumes great importance in achieving a vector-free zone at POEs in order to prevent invasive species form establishing in local environs and also to prevent exportation of local vector species to other countries by land (through lorries and trains), by air (through aircraft) and water (via ships at ports). This is achieved through Integrated vector management (IVM) by utilization of all appropriate technological and management techniques to bring about an effective degree of vector suppression in a cost-effective manner.
Mosquitoes
Mosquitoes are responsible for the transmission of many medically important pathogens and parasites such as viruses, bacteria, protozoans, and nematodes which cause serious diseases like malaria, dengue, yellow fever, encephalitis or filariasis. Surveys of immature mosquitoes are important aspects of an effective mosquito surveillance and control programme at PoE. The most popular indices are the Breeding Index, House Index, Container Index, Breteau Index, and Pupal Index. Adult sampling techniques such as Hand held and/or motorized aspirator and adult traps (light traps with or without carbon dioxide, CDC, UV, or BG-Sentinel traps are also used.
Threshold of tolerance varies with breeding habitats, flight ranges, feeding behavior, and activity rhythms of mosquito species, above which Vector control activities are initiated at PoEs. The threshold for initiating control action against any invasive species at PoE should be zero.
- House Index (HI)- The percentage of houses infested with larvae or pupae.
- Container Index (CI)- The percentage of water-holding containers infested with larvae and pupae out of those inspected.
- Breteau Index (BI)- Number of positive containers per 100 houses inspected (Aedes immatures).
- Pupal Index (PI)- Number of pupae per 100 houses inspected.
Mosquito Control
The choice of which vector control to employ would depend upon a situation analysis at the point of entry, ground crossing, or conveyance. Various well-tested control measures in order of priority are the following.
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Environmental management:
- source reduction
- habitat modification/manipulation
- Mechanical control:
- window and door screening
- drilling holes in fenders for drainage
- removal and safe storage of scrap.
- Biological control:
- larvivorous fish
- biological larvicides.
- Chemical control/insecticide treatment:
- larvicidal application
- adult control
- fogging
- indoor spraying
- insecticide treated material/special circumstances
- repellents
Rodent
Rodents have been implicated in transmitting plague, Leptospirosis, murine typhus, and food-borne Salmonellosis. It can also cause destruction aboard ships, crafts, rail cabins and motor lorries by gnawing through fittings, wiring, and circuitry, which can even cause short circuits resulting in fire hazard. Rodent surveillance is essential to identify species, extent of their infestations, and location for initiating control measures. Traps specifically designed for rodents which are durable and of standard quality are used for surveillance. The captured rats are be examined for ectoparasites such as fleas, mites etc. Sanitation, Rodent-guards, Illumination for rodent movement restrictions and Pier side inspections/surveillance on-board ships are common rodent prevention methods adopted. Rodents can be controlled using different types of traps.
Fleas
Fleas are holometabolous insects with 2380 described species. Fleas are entirely ectoparasites and are of tremendous medical and economic importance as vectors of several diseases to human health including bubonic plague, murine typhus, and (seldom) tularemia. When the flea index increases above a certain level, it may be necessary to initiate control measures to decrease the risk of human cases and plague epizootics. If Specific Flea Index found to be more than 1.0 through active surveillance at PoE especially in areas infested by rodents such as warehouses vector control is initiated. Insufflation measures involve treating rodent burrows and rat runs with 10% DDT or 5% malathion dust powder.
Cockroaches
Cockroaches are distributed worldwide and are one of the most common pests aboard ships, aircraft, and lorries especially in the areas where food is kept or stored. They prefer dark and warm areas, crevices and a variety of other human-made hideouts. They act as mechanical vectors and may. It can be controlled by application of Boric acid or a 2% aerosol formulation of d-phenothrin or recommended formulation of pyrethrins is suggested for aerosol applications. Gel baits are available with a variety of active ingredients, several of which can work on cockroaches.
Houseflies
Houseflies, Musca domestica, are found worldwide and constitute over 90% of all flies. Given their distribution, they can be found at PoE and also on vessels, particularly the kitchen and service areas. Houseflies can transmit over 100 pathogens causing cholera, dysentery, salmonellosis, typhoid, viral hepatitis A & E, etc. They also transmit anthrax, parasitic worms, pyogenic cocci, E. coli, enteroviruses, etc. Elimination of fly breeding sites involves repeated flushing of floors of kitchens, using sanitizers to clean cooking surfaces, utensils and other food preparation and dining areas (e.g. in galleys), and covering leftover food. Use of air curtains above doors can prevent fly entry as well. Devices that electrocute insects, sticky traps, slowly release insecticide, Dichlorvos vaporizer strips can also be used.
If an outbreak of vector-borne disease occurs or an exotic vector species is detected at PoE during routine surveillance that merits emergency measures, action must be initiated immediately on a scale commensurate with the risk posed. An emergency coordination meeting of the task force should be called to discuss the outbreak/infestation. Full-scale containment measures must be conducted followed by impact assessment of the measures used. The containment operations must continue until the exotic vector/rodent species is eradicated.
