sharon sanders
Editor-in-Chief & President
An overview of Aedes aegypti and Aedes albopictus control in the British Overseas Territory of the Cayman Islands
AW Wheeler (alan.wheeler@gov.ky), WD Petrie
Cayman Islands Mosquito Research and Control Unit, Grand Cayman, British West Indies
There have been six confirmed cases of dengue on the Cayman Islands in the last month, introduced from residents returning from elsewhere in the Caribbean. These are the first dengue cases in the islands since 2005, when there was a single case of local transmission. To date, there have been no reported cases of local transmission this year. However, it is possible that a returning resident infected with dengue could set up a local transmission cycle, especially with the current Breteau index (number of positive containers with larvae/100 houses) of 12.9. Given the current high incidence of dengue in the Caribbean [1], effective control of Aedes aegypti and Ae. albopictus is essential if the Cayman Islands are to remain free from dengue.
The Cayman Islands are a British Overseas Territory ? all citizens have British citizenship and are therefore European Union citizens. The Caymans consist of three islands in the northwestern Caribbean Sea. Grand Cayman, the largest of the three, is approximately 200km<SUP>2</SUP> while the two 'Sister Islands'?, Cayman Brac and Little Cayman, are both approximately 30 km<SUP>2</SUP>. The islands have a seasonally variable tropical climate with a rainy season from May to November. Grand Cayman and Little Cayman are low-lying and extensively covered by mangrove swamps, while Cayman Brac rises to 46m above sea level and has only isolated pockets of swamp area. A detailed description of the geology, climate vegetation and animal fauna of the Cayman Islands is given by Brunt & Davies [2]. Early surveys of the mosquito fauna on the islands by Somers in 1938 [3], Lewis in 1938 [4] and Giglioli in 1948 [5] all reported the presence of Ae. aegypti (Linnaeus) on Grand Cayman. The survey by Somers recorded a 99%-positive house index while Giglioli reported that Ae. aegypti was 'abundant' and recommended control using intra-domiciliary and peri-focal treatment with DDT.
From 1950 to 1954, this treatment was carried out by two government employees using a yearly cycle of 5% DDT. These treatments appear to have been effective, because two surveys in 1953, one of which was by Pan-American Health Organization/World Health Organization staff, failed to find any Ae. aegypti on the island.
In 1965, the Mosquito Research & Control Unit (MRCU) was established on Grand Cayman with the objective of promoting tourism by the effective control of nuisance-biting mosquitoes. At this time, Ochlerotatus taeniorhynchus accounted for over 90% of the mosquitoes collected in New Jersey light traps. Due to its status as the primary vector of dengue in the region, Ae. aegypti was also targeted for control.
In 1966, the MRCU established a network of ovipots [6] on Grand Cayman to detect and monitor the presence of Ae. aegypti. Ovipots are black enamel-coated glass jars half filled with tap water containing a 3/4? x 5? x 1/8? screenback hardboard paddle onto which ovipositing females lay eggs. The ovipots and subsequent island-wide surveys of yards in 1966 and 1967 found no evidence of the mosquito. However, in 1967 a survey of the mosquito fauna of Cayman Brac and Little Cayman revealed that Ae. aegypti was present on the Sister Islands. An elimination campaign launched in 1970 resulted in the last Ae. aegypti find occurring in June 1971 [7]. Final verification of the eradication was made by PAHO in 1972. Since then, there have been numerous reintroductions of Ae. aegypti onto Grand Cayman; 1973 and 1980 and from 1991-1996. All these introductions were successfully eliminated [8]. In 2002, Ae. aegypti was again detected on Grand Cayman and remains present. In addition to Ae. aegypti, Ae. albopictus was detected in George Town Grand Cayman in 1997 and became established in the George Town and West Bay areas, where it remains to date.
Control methods
The MRCU uses the same control techniques against Ae. aegypti and Ae. albopictus. The control program consists of three components: prevention of entry into the islands (Port Disinsection), ovipot surveillance and chemical control. Due to their small size and lack of natural resources, the Cayman Islands? economy relies heavily on the importation of goods, primarily from the United States. Growth in the human population and the development of tourism have resulted in considerable increases in the number of aircraft, ocean-going vessels and goods being bought to the Islands. This has greatly increased the risk of Ae. aegypti being introduced. Since 1966, legislation in the Cayman Islands has allowed the MRCU to carry out disinsection activities on all vessels arriving from overseas. Port Disinsection activities on the Islands ensure that all planes (excluding air ambulances and American military planes), ships (excluding cruise ships) and containerised goods (excluding refrigerated containers) are treated with an aerosol application of 2% D-phenothrin.
Since 1966, the MRCU has maintained a network of ovipots to monitor oviposition rate. Ovipots are concentrated around ports of entry and areas historically known to harbour Ae. aegypti. The current network on Grand Cayman consists of over 700 traps. The ovipots? wooden paddles are changed once a week and examined under a X40 dissecting microscope for eggs. Any paddles containing eggs are placed in water-filled jars to allow hatching and subsequent species identification. The MRCU also uses CO<SUB>2</SUB> baited traps (American Biophysics Mosquito Magnet Pro) with an L-lactic acid lure. These have been shown to be effective at sampling adults of both Ae. aegypti and Ae. albopictus.
The third component of the container-breeding mosquito control program is the application of insecticides against both adult and larval stages. The MRCU has employed teams of up to 25 survey officers to survey for larvae and treat any finds with residual larvicides and/or residual adulticide applications. Originally, survey officers searched both the inside and outside of residences. Results over the years have shown that, in the Cayman Islands, breeding occurs mainly outdoors. It is for this reason (and also to decrease the manpower required to survey yards) that surveying today is confined to searching outdoor breeding sites for the detection of larvae. Representative samples are collected from any container found holding larvae and these are returned to the laboratory for microscopic examination. The Breteau index is used as the standard larval index. Containers found in yards that are deemed suitable breeding sites for Ae. aegypti and Ae. albopictus are treated with a residual insecticide. Insecticides used include Methoprene, Temephos and Bacillus thuringiensis var. isrealensis (Bti). Based on the results of ovipot collections and larval surveys, yards found to be consistently breeding container mosquitoes are routinely treated with a residual wall and/or barrier treatment applied to external walls and vegetation. Insecticides used in this treatment have included Permethrin, Temephos, Deltamethrin, Lambdacyhalothrin and Bifenthrin.
Current infestation status
Ae. albopictus was first detected on Grand Cayman in 1997, one year after Ae. aegypti had been eliminated from the island. The initial larval find was made in July by a survey crew working in a yard located less than 1km from the George Town. The infestation area had a radius of 1,200 meters and 55% (thirty-three) of the subsequent larval finds occurred within 500m of the depot. The first positive ovipot finds were not made until September with three finds all located in the George Town collection area. Confirmation that the eggs were Ae. albopictus was made by hatching the eggs and identifying the larvae. By 2002, Ae. albopictus had become firmly established in the Western part of the island and were found in the same areas that had historically harboured Ae. aegypti.
The first find of Ae. aegypti larvae occurred on 15 October 2002 by yard survey at a location less than 2km from the cargo distribution depot. On the same day, a second focus was found by survey. A distance of over 14km separated the two foci. The presence of Ae. albopictus and Ae. aegypti in the same habitats caused some confusion when it came to the identification of these species. Initially, there were many instances where Ae. aegypti were mis-identified as Ae. albopictus and vice-versa. These mis-identifications resulted from using the banding pattern of the thorax for identification as it is easily damaged. A much more reliable method of identification was found to be the scales on the clypeus [9].
Following the introduction of Ae. aegypti, the population of Ae. albopictus declined rapidly and by September 2004 Ae. albopictus accounted for less than 5% of larval finds. The MRCU?s control efforts maintained the Breteau index below 5, which is considered below the threshold level for dengue transmission to occur [10]. In September 2004, Hurricane Ivan hit Grand Cayman and caused widespread destruction, resulting in a 13-fold increase in the number of larval samples collected at the start of the following rainy season. To deal with the increased population (at this point almost exclusively Ae. aegypti), the MRCU increased the number of survey crew from four to 10 officers. From 2005 to date, there has been a gradual decrease in the number of Ae. aegypti finds. The Breteau index for Grand Cayman has dropped from a peak of 19.19 in June 2005 to 12.9 in October 2007. Ae. albopictus levels appear to have stabilised and now account for approximately 5% of larval finds.
Discussion
It is hard to quantify the value of the MRCU?s Port Disinsection activities. We can conclude that they are not 100% effective at preventing the introduction of mosquitoes capable of transmitting dengue. Since the introduction of Port Disinsection, there have been four instances of Ae. aegypti becoming established in the islands and one instance of Ae. albopictus. We do not know if any introductions occurred that failed to establish, nor how many instances there have been when our disinsection activities successfully prevented an introduction.
There can be little doubt that aircraft provide a means for the dissemination of mosquito species [11]. However, the overall importance of aircraft in the world-wide dissemination of Ae. aegypti and Ae. albopictus has to be questioned. Should an adult mosquito arrive by aircraft, in order to become established in its new environment it would have to have mated prior to its arrival (unless a male mosquito of the same species also hitches a ride to the new area). Even if a mated female does arrive, it then has to find a suitable location to lay its eggs. The airport on Grand Cayman is quite a desolate area in terms of suitable oviposition sites, except for the ovipots located throughout the airport. A Study by Reiter [12] showed that Ae. aegypti will rarely travel more than 100m in search of an oviposition site. This suggests that if the airport were the major source of introductions, the mosquitoes would first be detected in ovipots at the airport.
Yachts and other ocean-going vessels are another means by which Ae. aegypti could enter the Cayman Islands. Such a vessel could be the source of multiple introductions into the Islands since a bucket on board a yacht could contain hundreds of larvae that could fly the short distance from the yacht to the shore.
The most likely sources of introduction into the Cayman Islands are containerized goods. Although all containers are treated, the insecticide used is unlikely to have any effect on eggs laid on goods in the container.
The dissemination of both Ae. aegypti and Ae. albopictus as eggs laid on the surface of car tyres is well documented [13] and has been incriminated as the main route of spread of these species. The high numbers of both adult and larval finds in and around the container depot in George Town suggests that the current introduction originated from that location (Wheeler, unpublished). When a container of mixed goods arrives, the container is unloaded and the goods may be left in an open area exposed to rain. Quite often tyres and other water holding objects are left out for periods in excess of one week until they are collected. Conditions found at the container depot allow for a situation whereby eggs arriving inside an imported container may left exposed to rain resulting in the emergence of adult mosquitoes. These can then mate and lay eggs on other objects at the depot, which are subsequently collected and taken to other parts of the island and potentially establish secondary infestations. This may explain why Ae. aegypti was initially detected at two separate foci separated by a distance of over 14km.
Ovipots have proven to be a valuble means of monitoring the distribution of container-breeding mosquitoes and thereby directing control operations. They are a simple, low-maintenance tool to passively monitor both Ae. aegypti and Ae. albopictus. However, they need to be correctly positioned in and around all ports of entry if they are to detect early introductions. In the current infestations, ovipots failed to detect the presence of both species until several months after the first larval find by yard survey; this was probably as a result of them being poorly positioned.
House-to-house larval survey has been found to provide the most reliable method of assessing the distribution of Ae. albopictus and Ae. aegypti and detecting infestations at an early stage.
At the time of both the current infestations, the survey crew consisted of only four employees. With a population of over 45,000 on Grand Cayman living in approximately 10,000 residences, the survey crew remains undersized (even though it has now increased to 10 men), and during the rainy season the number of larval breeding sites becomes too great for any effective control to be implemented. A study by Wheeler (unpublished) has shown that populations of both species can be effectively reduced if yards are surveyed on a weekly basis. To do this on Grand Cayman would require between 20 and 25 workers. In the current dengue outbreak, the Sister Islands have not reported any cases of dengue, and both those islands remain free of Ae. aegypti, although MRCU staff on Cayman Brac recently prevented the introduction of the mosquito as larvae on board a cargo vessel. House-to-house inspections, population assessments of Ae. aegypti and insecticidal treatments of selected areas will remain in force in the Cayman Islands, certainly for the immediate future.
References:
AW Wheeler (alan.wheeler@gov.ky), WD Petrie
Cayman Islands Mosquito Research and Control Unit, Grand Cayman, British West Indies
There have been six confirmed cases of dengue on the Cayman Islands in the last month, introduced from residents returning from elsewhere in the Caribbean. These are the first dengue cases in the islands since 2005, when there was a single case of local transmission. To date, there have been no reported cases of local transmission this year. However, it is possible that a returning resident infected with dengue could set up a local transmission cycle, especially with the current Breteau index (number of positive containers with larvae/100 houses) of 12.9. Given the current high incidence of dengue in the Caribbean [1], effective control of Aedes aegypti and Ae. albopictus is essential if the Cayman Islands are to remain free from dengue.
The Cayman Islands are a British Overseas Territory ? all citizens have British citizenship and are therefore European Union citizens. The Caymans consist of three islands in the northwestern Caribbean Sea. Grand Cayman, the largest of the three, is approximately 200km<SUP>2</SUP> while the two 'Sister Islands'?, Cayman Brac and Little Cayman, are both approximately 30 km<SUP>2</SUP>. The islands have a seasonally variable tropical climate with a rainy season from May to November. Grand Cayman and Little Cayman are low-lying and extensively covered by mangrove swamps, while Cayman Brac rises to 46m above sea level and has only isolated pockets of swamp area. A detailed description of the geology, climate vegetation and animal fauna of the Cayman Islands is given by Brunt & Davies [2]. Early surveys of the mosquito fauna on the islands by Somers in 1938 [3], Lewis in 1938 [4] and Giglioli in 1948 [5] all reported the presence of Ae. aegypti (Linnaeus) on Grand Cayman. The survey by Somers recorded a 99%-positive house index while Giglioli reported that Ae. aegypti was 'abundant' and recommended control using intra-domiciliary and peri-focal treatment with DDT.
From 1950 to 1954, this treatment was carried out by two government employees using a yearly cycle of 5% DDT. These treatments appear to have been effective, because two surveys in 1953, one of which was by Pan-American Health Organization/World Health Organization staff, failed to find any Ae. aegypti on the island.
In 1965, the Mosquito Research & Control Unit (MRCU) was established on Grand Cayman with the objective of promoting tourism by the effective control of nuisance-biting mosquitoes. At this time, Ochlerotatus taeniorhynchus accounted for over 90% of the mosquitoes collected in New Jersey light traps. Due to its status as the primary vector of dengue in the region, Ae. aegypti was also targeted for control.
In 1966, the MRCU established a network of ovipots [6] on Grand Cayman to detect and monitor the presence of Ae. aegypti. Ovipots are black enamel-coated glass jars half filled with tap water containing a 3/4? x 5? x 1/8? screenback hardboard paddle onto which ovipositing females lay eggs. The ovipots and subsequent island-wide surveys of yards in 1966 and 1967 found no evidence of the mosquito. However, in 1967 a survey of the mosquito fauna of Cayman Brac and Little Cayman revealed that Ae. aegypti was present on the Sister Islands. An elimination campaign launched in 1970 resulted in the last Ae. aegypti find occurring in June 1971 [7]. Final verification of the eradication was made by PAHO in 1972. Since then, there have been numerous reintroductions of Ae. aegypti onto Grand Cayman; 1973 and 1980 and from 1991-1996. All these introductions were successfully eliminated [8]. In 2002, Ae. aegypti was again detected on Grand Cayman and remains present. In addition to Ae. aegypti, Ae. albopictus was detected in George Town Grand Cayman in 1997 and became established in the George Town and West Bay areas, where it remains to date.
Control methods
The MRCU uses the same control techniques against Ae. aegypti and Ae. albopictus. The control program consists of three components: prevention of entry into the islands (Port Disinsection), ovipot surveillance and chemical control. Due to their small size and lack of natural resources, the Cayman Islands? economy relies heavily on the importation of goods, primarily from the United States. Growth in the human population and the development of tourism have resulted in considerable increases in the number of aircraft, ocean-going vessels and goods being bought to the Islands. This has greatly increased the risk of Ae. aegypti being introduced. Since 1966, legislation in the Cayman Islands has allowed the MRCU to carry out disinsection activities on all vessels arriving from overseas. Port Disinsection activities on the Islands ensure that all planes (excluding air ambulances and American military planes), ships (excluding cruise ships) and containerised goods (excluding refrigerated containers) are treated with an aerosol application of 2% D-phenothrin.
Since 1966, the MRCU has maintained a network of ovipots to monitor oviposition rate. Ovipots are concentrated around ports of entry and areas historically known to harbour Ae. aegypti. The current network on Grand Cayman consists of over 700 traps. The ovipots? wooden paddles are changed once a week and examined under a X40 dissecting microscope for eggs. Any paddles containing eggs are placed in water-filled jars to allow hatching and subsequent species identification. The MRCU also uses CO<SUB>2</SUB> baited traps (American Biophysics Mosquito Magnet Pro) with an L-lactic acid lure. These have been shown to be effective at sampling adults of both Ae. aegypti and Ae. albopictus.
The third component of the container-breeding mosquito control program is the application of insecticides against both adult and larval stages. The MRCU has employed teams of up to 25 survey officers to survey for larvae and treat any finds with residual larvicides and/or residual adulticide applications. Originally, survey officers searched both the inside and outside of residences. Results over the years have shown that, in the Cayman Islands, breeding occurs mainly outdoors. It is for this reason (and also to decrease the manpower required to survey yards) that surveying today is confined to searching outdoor breeding sites for the detection of larvae. Representative samples are collected from any container found holding larvae and these are returned to the laboratory for microscopic examination. The Breteau index is used as the standard larval index. Containers found in yards that are deemed suitable breeding sites for Ae. aegypti and Ae. albopictus are treated with a residual insecticide. Insecticides used include Methoprene, Temephos and Bacillus thuringiensis var. isrealensis (Bti). Based on the results of ovipot collections and larval surveys, yards found to be consistently breeding container mosquitoes are routinely treated with a residual wall and/or barrier treatment applied to external walls and vegetation. Insecticides used in this treatment have included Permethrin, Temephos, Deltamethrin, Lambdacyhalothrin and Bifenthrin.
Current infestation status
Ae. albopictus was first detected on Grand Cayman in 1997, one year after Ae. aegypti had been eliminated from the island. The initial larval find was made in July by a survey crew working in a yard located less than 1km from the George Town. The infestation area had a radius of 1,200 meters and 55% (thirty-three) of the subsequent larval finds occurred within 500m of the depot. The first positive ovipot finds were not made until September with three finds all located in the George Town collection area. Confirmation that the eggs were Ae. albopictus was made by hatching the eggs and identifying the larvae. By 2002, Ae. albopictus had become firmly established in the Western part of the island and were found in the same areas that had historically harboured Ae. aegypti.
The first find of Ae. aegypti larvae occurred on 15 October 2002 by yard survey at a location less than 2km from the cargo distribution depot. On the same day, a second focus was found by survey. A distance of over 14km separated the two foci. The presence of Ae. albopictus and Ae. aegypti in the same habitats caused some confusion when it came to the identification of these species. Initially, there were many instances where Ae. aegypti were mis-identified as Ae. albopictus and vice-versa. These mis-identifications resulted from using the banding pattern of the thorax for identification as it is easily damaged. A much more reliable method of identification was found to be the scales on the clypeus [9].
Following the introduction of Ae. aegypti, the population of Ae. albopictus declined rapidly and by September 2004 Ae. albopictus accounted for less than 5% of larval finds. The MRCU?s control efforts maintained the Breteau index below 5, which is considered below the threshold level for dengue transmission to occur [10]. In September 2004, Hurricane Ivan hit Grand Cayman and caused widespread destruction, resulting in a 13-fold increase in the number of larval samples collected at the start of the following rainy season. To deal with the increased population (at this point almost exclusively Ae. aegypti), the MRCU increased the number of survey crew from four to 10 officers. From 2005 to date, there has been a gradual decrease in the number of Ae. aegypti finds. The Breteau index for Grand Cayman has dropped from a peak of 19.19 in June 2005 to 12.9 in October 2007. Ae. albopictus levels appear to have stabilised and now account for approximately 5% of larval finds.
Discussion
It is hard to quantify the value of the MRCU?s Port Disinsection activities. We can conclude that they are not 100% effective at preventing the introduction of mosquitoes capable of transmitting dengue. Since the introduction of Port Disinsection, there have been four instances of Ae. aegypti becoming established in the islands and one instance of Ae. albopictus. We do not know if any introductions occurred that failed to establish, nor how many instances there have been when our disinsection activities successfully prevented an introduction.
There can be little doubt that aircraft provide a means for the dissemination of mosquito species [11]. However, the overall importance of aircraft in the world-wide dissemination of Ae. aegypti and Ae. albopictus has to be questioned. Should an adult mosquito arrive by aircraft, in order to become established in its new environment it would have to have mated prior to its arrival (unless a male mosquito of the same species also hitches a ride to the new area). Even if a mated female does arrive, it then has to find a suitable location to lay its eggs. The airport on Grand Cayman is quite a desolate area in terms of suitable oviposition sites, except for the ovipots located throughout the airport. A Study by Reiter [12] showed that Ae. aegypti will rarely travel more than 100m in search of an oviposition site. This suggests that if the airport were the major source of introductions, the mosquitoes would first be detected in ovipots at the airport.
Yachts and other ocean-going vessels are another means by which Ae. aegypti could enter the Cayman Islands. Such a vessel could be the source of multiple introductions into the Islands since a bucket on board a yacht could contain hundreds of larvae that could fly the short distance from the yacht to the shore.
The most likely sources of introduction into the Cayman Islands are containerized goods. Although all containers are treated, the insecticide used is unlikely to have any effect on eggs laid on goods in the container.
The dissemination of both Ae. aegypti and Ae. albopictus as eggs laid on the surface of car tyres is well documented [13] and has been incriminated as the main route of spread of these species. The high numbers of both adult and larval finds in and around the container depot in George Town suggests that the current introduction originated from that location (Wheeler, unpublished). When a container of mixed goods arrives, the container is unloaded and the goods may be left in an open area exposed to rain. Quite often tyres and other water holding objects are left out for periods in excess of one week until they are collected. Conditions found at the container depot allow for a situation whereby eggs arriving inside an imported container may left exposed to rain resulting in the emergence of adult mosquitoes. These can then mate and lay eggs on other objects at the depot, which are subsequently collected and taken to other parts of the island and potentially establish secondary infestations. This may explain why Ae. aegypti was initially detected at two separate foci separated by a distance of over 14km.
Ovipots have proven to be a valuble means of monitoring the distribution of container-breeding mosquitoes and thereby directing control operations. They are a simple, low-maintenance tool to passively monitor both Ae. aegypti and Ae. albopictus. However, they need to be correctly positioned in and around all ports of entry if they are to detect early introductions. In the current infestations, ovipots failed to detect the presence of both species until several months after the first larval find by yard survey; this was probably as a result of them being poorly positioned.
House-to-house larval survey has been found to provide the most reliable method of assessing the distribution of Ae. albopictus and Ae. aegypti and detecting infestations at an early stage.
At the time of both the current infestations, the survey crew consisted of only four employees. With a population of over 45,000 on Grand Cayman living in approximately 10,000 residences, the survey crew remains undersized (even though it has now increased to 10 men), and during the rainy season the number of larval breeding sites becomes too great for any effective control to be implemented. A study by Wheeler (unpublished) has shown that populations of both species can be effectively reduced if yards are surveyed on a weekly basis. To do this on Grand Cayman would require between 20 and 25 workers. In the current dengue outbreak, the Sister Islands have not reported any cases of dengue, and both those islands remain free of Ae. aegypti, although MRCU staff on Cayman Brac recently prevented the introduction of the mosquito as larvae on board a cargo vessel. House-to-house inspections, population assessments of Ae. aegypti and insecticidal treatments of selected areas will remain in force in the Cayman Islands, certainly for the immediate future.
References:
- Caribbean Epidemiology Centre. CAREC Alert. 2007. http://www.carec.org/pdf/denguealert-october-2007.pdf
- Brunt MA, Davies JE. The Cayman Islands: natural history and biogeography. Kluwer Academic Publishers. 1994.
- Somers FG. A sanitary report with special reference to sanitation and mosquito problems and organizing health work. Senior Sanitary Inspector, Jamaica. 1938.
- Lewis CB. Preliminary report concerning mosquitoes found in Grand Cayman: Cayman Islands Government Report. 1938.
- Giglioli G. The mosquito problem of Grand Cayman in relation to recent advances in mosquito control techniques. H.M. Colonial Office. 1948.
- Thaggard CW, Eliason DA. Field evaluation of components for an Aedes aegypti (L.) oviposition trap. Mosquito News 1969;29(4):608-612.
- Nathan MB, Giglioli MEC. Eradication of Aedes aegypti on Cayman Brac and Little Cayman, West Indies, with Abate (temephos) in 1970-1971. Bull. Pan. Am. Hlth. Org. 1982;16(1):28-39.
- Petrie W, Allen F. Cayman Islands Mosquito Research & Control Unit. In; 2007.
- Savage HM, Smith GC. Identification of damaged adult female specimens of Aedes albopictus and Aedes aegypti in the New World. Journal of the American Mosquito Control Association 1994;10(3):440-442.
- Macdonald WW. Aedes aegypti in Malaysia. II. Larval and 1. adult biology. Annals of Tropical Medicine and Parasitology 1956;50:399-414.
- Gratz NG, Steffen R, Cocksedge W. Why aircraft disinsection? Bulletin of the World Health Organization 2000;78(8):995-1004.
- Reiter P, Amador MA, Anderson RA. Short report: Dispersal of Aedes aegypti in an urban area after blood feeding as demonstrated by rubidium-marked eggs. Am. J. Trop. Med. Hyg. 1995;52(2):177-179.
- Reiter P. Aedes albopictus and the world trade in used tires 1988-1995: the shape of things to come? Journal of the American Mosquito Control Association 1998;14(1):83-94.