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Tsetse fly repellents
341 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE. Vo]. 40. No. 3. December, 1946.
TSETSE
FLY REPELLENTS BY
G'. M. F I N D L A Y , * J. H A R D W I C K E A1ND A . J. PHELPS.
Substances capable of deterring the tsetse fly from biting have received little attention. HOR•BY and FRENCH (1948) found that pyrethrum protected cattle and donkeys, wh{le HOLDEN and FINDLAY (1944) showed that pyrethrum in a vanishing cream base had a repellent action when applied to the human skin. A number of other compounds have now been tested for repellent action, the technique being similar to that used by HOLDEN and FINDLAY (1944). The tsetses were almost exclusively Glossina palpalfs. All the compounds were in solution. EXPERIMENTAL RESULTS.
The compounds used and the results obtained are shown in Table I. The figures recorded are the totals obtained from at least two experiments made on different days. In the case of Formula 622, six separate experiments were made. * Our thanks are due to Colonel LESLIE E. KNAPP, U.S.A.A.F., for a supply of the compounds tested.
342
TSETSE
REPELLENTS
It will be seen that N-n-amylsuccinimide, 2-phenyl-cyclohexanol and
n-butyl-dl malate all reduced the number of tsetses which settled and bit. The most striking results were obtained with inda]one and Formula 622, while Rutger's 612 had no significant action. T A B L E 1. TSETSE FLY REPELLENTS.
Compound.
Controls
Treated
N u m b e r of tsetse
N u m b e r of tsetse
Settling. N-sec-Butylphthalamide ...... 2-Phenylethyl-a-hydroxyisobutyrate ... N-n-Amylsuccinimide . . . . . . . . . Benzyl ether . . . . . . . . . . . . 2-Phenyl-cyclohexanol . . . . . . . . . n - B u t y l - a l l malate ......... *Ethylhexane-dlol-1, 3 (Rutger's 612) ... *2, 2 ' - D i m e t h y l - 2 - c a r b o b u t o x y - d i h y d r o 7-pyrone (Indalone) . . . . . . * F o r m u l a 622 (Dimethyl phthalate "6 parts, indalone 2 parts, R u t g e r ' s 612 2 parts) . . . . . . . . . . . . . . .
39 39 147 82 77 74
~
04.
!
Biting.
Settling.
Biting.
27 27 119 67 68 65
50
41. 25 55 79 42 43 67
33 23 33 64 21 29 46
52
22
11
162
74
23
:
65 ! 217
* T h e s e c o m p o u n d s u n d e r the trade m a r k " Skat," are m a n u f a c t u r e d b y the G a l l o w h u r Chemical Corporation, Windsor, Vermont, for the Skol Co., Inc., N e w York, N.Y.
Duration of Effectiveness of Indalone and Formula 622. To determine the time during which these compounds were effective, they were applied at intervals of from 1 to 8 hours before exposure to tsetse bites. The results were as follows :--
Interval between application and exposure.
1 hour 2 hours 4 hours 6 hours 8 hours
Controls.
Indalone.
622.
N u m b e r of tsetse
N u m b e r of,tsetse
N u m b e r of tsetse .
Settling.
Biting.
Settling.
Biting.
Settling.
Biting.
67 52 60 33 48
58 46 52 30 38
12 14 22 26 28
5 4 5 18 32
16 14 20 32 29
6 6 7 27 20
G. M. F [ N D L A Y , J . H A R D W I C K E AND A. J. P H E L P S
343
Both compounds thus showed a loss of efficiency between 4 and 6 hours after application.
The Effect of Sunlight and Sweating on the Efficiency of Formula 622. In tests on p y r e t h r u m the question arose whether sweating or exposure to sunlight reduced its efficiency. T h e conclusion was reached that excessive sweating was the more deleterious. Similar experiments were carried out with Formula 622. T w o treated and two control fly-boys sat for 30 minutes exposed to the direct rays of the sun in a tsetse-free area. T h e y then sat for 1 hour just within the shadow of t h e . b u s h fringing the Volta Ri~er. T h e results were : - -
Controls.
Treated.
Number of tsetse.
Number of tsetse.
Settling.
Biting.
Settling.
Biting.
52
48
35
30
Some loss of repellent power was noted. T o test the effect of heavy sweating, two treated and two ur/treated fly-boys danced strenuously in the shade for 30 minutes. T h e y were then exposed to tsetse flies as before. T h e results were : - -
Controls.
Treated.
Number of tsetse
Number of tsetse
Settling.
Biting.
Settling.
Biting.
42
39
19
4
No loss of efficiency was observed. DISCUSSION. O f the nine compounds tested for their repellent action on tsetses, Formula 622, indalone, N-n-amylsuccinimide, 2-phenyl-cyclohexanol, and n-butyl-dl malate were all to a certain degree effective.
344
TSETSE R E P E L L E N T S
Unfortunately, dimethyl phthalate in pure form was not available, but Rutger's 612 was without action while indalone was~ active, so that some and possibly all the activity of Formula 622 is due to indalone. Both Formula 622 and indalone were found to be effective up t o 4 hours of application against the bites of West African species of Culicoides. Experiments carried out by Major LEWIS BERNER (1945) with the above nine compounds against anopheline and culicine mosquitoes showed that 2-phenylethyl-a-hydroxyisobutyrate was one of the most efficient compounds, while n-butyl-dl malate and 2-phenyl-cyclohexanol were two of the least efficient. Repellent action against tsetse flies thus does not entirely parallel that against mosquitoes. •CONCLUSIONS.
Under field conditions nine compounds were tested for repellent action against tsetses. Indalone, Formula 622, N-n-amylsuccinimide, 2-phenylcyelohexanol and n-butyl-dl malate possessedsome activity. REFERENCES. (1945). Testing of Insect Repellents. Unpublished Report to the SurgeonGeneral, U.S. Army. HOLDEN, J. R. & FINDLAY,G.M. (1944). Trans. R. Soc. trop. Med. Hyg., 38, 199. HORNBY, H. E. & F~NCH, M . H . (1943). 1bid., 37, 41. BERNER, L.
TSETSE
FLY REPELLENTS BY
G'. M. F I N D L A Y , * J. H A R D W I C K E A1ND A . J. PHELPS.
Substances capable of deterring the tsetse fly from biting have received little attention. HOR•BY and FRENCH (1948) found that pyrethrum protected cattle and donkeys, wh{le HOLDEN and FINDLAY (1944) showed that pyrethrum in a vanishing cream base had a repellent action when applied to the human skin. A number of other compounds have now been tested for repellent action, the technique being similar to that used by HOLDEN and FINDLAY (1944). The tsetses were almost exclusively Glossina palpalfs. All the compounds were in solution. EXPERIMENTAL RESULTS.
The compounds used and the results obtained are shown in Table I. The figures recorded are the totals obtained from at least two experiments made on different days. In the case of Formula 622, six separate experiments were made. * Our thanks are due to Colonel LESLIE E. KNAPP, U.S.A.A.F., for a supply of the compounds tested.
342
TSETSE
REPELLENTS
It will be seen that N-n-amylsuccinimide, 2-phenyl-cyclohexanol and
n-butyl-dl malate all reduced the number of tsetses which settled and bit. The most striking results were obtained with inda]one and Formula 622, while Rutger's 612 had no significant action. T A B L E 1. TSETSE FLY REPELLENTS.
Compound.
Controls
Treated
N u m b e r of tsetse
N u m b e r of tsetse
Settling. N-sec-Butylphthalamide ...... 2-Phenylethyl-a-hydroxyisobutyrate ... N-n-Amylsuccinimide . . . . . . . . . Benzyl ether . . . . . . . . . . . . 2-Phenyl-cyclohexanol . . . . . . . . . n - B u t y l - a l l malate ......... *Ethylhexane-dlol-1, 3 (Rutger's 612) ... *2, 2 ' - D i m e t h y l - 2 - c a r b o b u t o x y - d i h y d r o 7-pyrone (Indalone) . . . . . . * F o r m u l a 622 (Dimethyl phthalate "6 parts, indalone 2 parts, R u t g e r ' s 612 2 parts) . . . . . . . . . . . . . . .
39 39 147 82 77 74
~
04.
!
Biting.
Settling.
Biting.
27 27 119 67 68 65
50
41. 25 55 79 42 43 67
33 23 33 64 21 29 46
52
22
11
162
74
23
:
65 ! 217
* T h e s e c o m p o u n d s u n d e r the trade m a r k " Skat," are m a n u f a c t u r e d b y the G a l l o w h u r Chemical Corporation, Windsor, Vermont, for the Skol Co., Inc., N e w York, N.Y.
Duration of Effectiveness of Indalone and Formula 622. To determine the time during which these compounds were effective, they were applied at intervals of from 1 to 8 hours before exposure to tsetse bites. The results were as follows :--
Interval between application and exposure.
1 hour 2 hours 4 hours 6 hours 8 hours
Controls.
Indalone.
622.
N u m b e r of tsetse
N u m b e r of,tsetse
N u m b e r of tsetse .
Settling.
Biting.
Settling.
Biting.
Settling.
Biting.
67 52 60 33 48
58 46 52 30 38
12 14 22 26 28
5 4 5 18 32
16 14 20 32 29
6 6 7 27 20
G. M. F [ N D L A Y , J . H A R D W I C K E AND A. J. P H E L P S
343
Both compounds thus showed a loss of efficiency between 4 and 6 hours after application.
The Effect of Sunlight and Sweating on the Efficiency of Formula 622. In tests on p y r e t h r u m the question arose whether sweating or exposure to sunlight reduced its efficiency. T h e conclusion was reached that excessive sweating was the more deleterious. Similar experiments were carried out with Formula 622. T w o treated and two control fly-boys sat for 30 minutes exposed to the direct rays of the sun in a tsetse-free area. T h e y then sat for 1 hour just within the shadow of t h e . b u s h fringing the Volta Ri~er. T h e results were : - -
Controls.
Treated.
Number of tsetse.
Number of tsetse.
Settling.
Biting.
Settling.
Biting.
52
48
35
30
Some loss of repellent power was noted. T o test the effect of heavy sweating, two treated and two ur/treated fly-boys danced strenuously in the shade for 30 minutes. T h e y were then exposed to tsetse flies as before. T h e results were : - -
Controls.
Treated.
Number of tsetse
Number of tsetse
Settling.
Biting.
Settling.
Biting.
42
39
19
4
No loss of efficiency was observed. DISCUSSION. O f the nine compounds tested for their repellent action on tsetses, Formula 622, indalone, N-n-amylsuccinimide, 2-phenyl-cyclohexanol, and n-butyl-dl malate were all to a certain degree effective.
344
TSETSE R E P E L L E N T S
Unfortunately, dimethyl phthalate in pure form was not available, but Rutger's 612 was without action while indalone was~ active, so that some and possibly all the activity of Formula 622 is due to indalone. Both Formula 622 and indalone were found to be effective up t o 4 hours of application against the bites of West African species of Culicoides. Experiments carried out by Major LEWIS BERNER (1945) with the above nine compounds against anopheline and culicine mosquitoes showed that 2-phenylethyl-a-hydroxyisobutyrate was one of the most efficient compounds, while n-butyl-dl malate and 2-phenyl-cyclohexanol were two of the least efficient. Repellent action against tsetse flies thus does not entirely parallel that against mosquitoes. •CONCLUSIONS.
Under field conditions nine compounds were tested for repellent action against tsetses. Indalone, Formula 622, N-n-amylsuccinimide, 2-phenylcyelohexanol and n-butyl-dl malate possessedsome activity. REFERENCES. (1945). Testing of Insect Repellents. Unpublished Report to the SurgeonGeneral, U.S. Army. HOLDEN, J. R. & FINDLAY,G.M. (1944). Trans. R. Soc. trop. Med. Hyg., 38, 199. HORNBY, H. E. & F~NCH, M . H . (1943). 1bid., 37, 41. BERNER, L.