Eradication of aedes aegypti on Cayman Brac and Little Cayman West Indies, with Abate (Temephos) in 1970-1971

In 1970-1971 an intensive campaign against Aedes aegypti and larvae resulted in eradication of this mosquito from the Lesser Cayman Islands. This account of problems encountered and the measures taken to overcome them provides useful information for those concerned with aegypti eradication (AU)

Abate for the control of blackfly larvae in the river Burru, Lethem area, Rupununi, Guyana

Abate (emulsifiable concentrate) for the control of Blackfly larvae was used in the river Burru, Lethem, Rupununi, Guyana. The results showed that it was not effective at 0.5 p.p.m. against larvae of S. incrustatum (AU)

Preliminary trials using abate to control Kabowra flies in the Rupununi, Guyana - abstract

Control of Simulium (called Kabowras in Guyana) black flies is usually directed to the larvae which breed in fast flowing waters. The purpose of the project was to determine the effectiveness of Abate Insecticide 200E in controlling Simulium sp., in a selected river in the Rupununi Savannah, Guyana. Two bioassays were carried out on the San Jose River near Lethem, Rupununi to determine the effective distance of Abate 200E at a concentration of 0.3 ppm during August, 1979 along a 2.4 km and 3.5 km stretch of the river. River discharge rates were calculated at a point of injection of the Abate. The volume of Abate required to give a concentration of 0.3 ppm when dispensed over approximatelty thirty minutes at the measured discharge was dripped into the stream. Counts of larvae on marked vegetation were made at several points before injection of Abate and four and nineteen hours after injection. The results of the first bioassay over 2.4 km showed at 57.8 percent drop in larvae four hours after injection of larvicide and a 99.3 percent drop within nineteen hours. Larval mortality was 97 percent at 2.4 km. Larval counts after the second Abate application two weeks later at 3.5 km showed a 52.8 percent drop after four hours and 96.1 percent after nineteen hours. Larval mortality was 100 percent at 2.7 km and 9.3 percent at 3.5 km. Larval counts were very low during the subsequent four weeks. Abate 200E at a concentration of 0.3 ppn was found to be effective in killing Simulium larvae over a distance of 3.5 km with a mortality of 93 percent nineteen hours after injection of larvicide. These trials should continue using lower concentrations of the larvicide (AU)

Spatial distribution of insecticide resistance in Caribbean populations of Aedes aegypti and its significance

To monitor resistance to insecticides, bioassays were performed on 102 strains of the dengue vector Aedes aegypti (L.) from 16 countries ranging from Suriname in South America and throught the chain of Caribbean Islands to the Bahamas, where the larvicide temephos and the adulticide malathion have been in use for 15 to 30 years. There was wide variation in the sensitivity to the larvicide in mosquito populations within and among countries. Mosquito strains in some countries such as Antigua, St. Lucia, and Tortola had consistently high resistance ratios (RR) to temephos, ranging from 5.3 to 17.7. In another group of countries-e.g., Anguilla and Curacao-mosquitoes had mixed levels of resistance to temephos (RR=2.5-10.6), and in a third group of countries, including St. Kitts, Barbados, Jamiaca, and Suriname, mosquitoes had consistently low levels of resistance to temephos (RR=1-4.6) (P<0.05). On occasion significantly different levels of resistance were recorded from neighboring A. aegypti communities, which suggests there is little genetic exchange among populations. The impact of larval resistance expressed itself as reduced efficacy of temephos to kill mosquitoes when strains were treated in the laboratory or in the field in large container environments with recommended dosages. Although a sensitive strain continued to be completely controlled for up to 7 weeks, the most resistant strains had 24 percent survival after the first week. By week 6, 60 percent to 75 percent of all resistant strains of larvae were surviving the larval period. Responses to malathion in adult A. aegypti varied from a sensitive population in Suriname (RR=1.3) to resistant strains in St. Vincent (RR=4.4), Dominica (RR=4.2), and Trinidad (RR=4.0); however, resistance was generally not on the scale of that observed to temephos in the larval stages and had increased only slightly when compared to the levels that existed 3 to 4 years ago. Suggestions are made for a pesticide usage policy for the Caribbean region, with modifications for individual countries. This would be formulated based on each country's insecticide-resistance profile. Use of physical and biological control strategies would play a more critical role than the use of insecticides (AU)