Eshghy, N.

Motabar, M.

Horizon / Pleins textes

Field tria1 of Sumithion (O.M.S. 43) in the Mamasani area, 
Southern Iran, August-December, 1972 
ABSTRACT. h 
Tice aine of this tria1 was to determine the toxic effect 
OMS-43 OJZ operators and inhabitants and to evaluate the 
effectiveness of this insecticide fos the control of adult 
anopheline mosquitoes. 
One round of spraying was implencented in August, 1972, 
at the peak of activity of A. stephensi, and this lasted for 
30 successive days. 
Titis study showed that : (a) the use of Sumithion under 
local conditions (subtropics, hot and dry season) is safe for 
residents, but its toxic eflect on operators with lirnited 
precautionary nceasures should be considered further and 
(b) Suncithion is an effective insecticide against anopheline 
ncosquitoes and controlled A. stephensi under the conditions 
of this experirnent for more tha?i two months. 
RÉSUMÉ. 
Le but de ce travail etait de déterminer la toxicite de 
I’OMS-43 pous la main-d’œuvre de pulvérisation et d’évaluer 
son effet dans la lutte contre les anophèles adultes en Iran. 
Un cycle d’aspersions fut exécuté en aofit 1972, au pic 
d’activite d’A. stephensi. 
L’étude a montré que : l’utilisation du Suncithion 
(OMS-43 : Fenitrothion) est sans danger pour les habitants 
dans les conditions locales (saison chaude et sèche sub- 
tropicale) mais l’eflet toxique sccr la main-d’œuvre est à 
prendre en considération ; le Sumithion est 11~1 insecticide 
‘eficace contre les anophèles adultes et contrôle A. stephensi 
pendant plus de deux nco’is dans les conditions de l’expérience. 
M. MOTABAR 
and N. ESHGHIY 
Departncent of Environmental Health 
University of Teheran, P.O. Box 1310, 
Telzeran, Iran 
INTRODUCTION. 
Due to the development of resistance of A. stephensi, 
the main malaria vector of southern Iran, to chlorinated 
hydrocarbon insecticides (Mofidi et al., 1962), Malathion 
is in use at the present time for malaria control in this 
area. This program may be faced with serious obstacles 
in the near future, and there is thus a vital need for a 
safe and effective insecticide which couId be used as a 
substitute for Malathion. A large-scale field tria1 of 
Sumithion (OMS-43) at stage VI was carried out in the 
Mamasani area in southern Iran, from August fo De- 
cember, 1972, by the School of Public Health and Institute 
of Public Health Research in collaboration with ME0 
of Iran and the Sumitomo Chemical CO., Ltd., Japan. 
OBJECTIVES. 
The main objective of this tria1 was to determine: 
1. the safety of the material in regard to spraymen 
and inhabitants under operating conditions; 
2. the toxic effects of the insecticide on domestic 
animais and poultry; and 
3. the impact of insecticide treatment on the overall 
local anopheline population, especially on A. stephensi. 
BACKGROUND INFORMATION. 
A. stephensi, the main vector of the area, developed 
resistance to DDT in 1957 and to Dieldrin in 1960. Mala- 
This paper was presented at the Ninth International Congress on Tropical Medicine and Malaria, Athens, 14-21 October 1973. 
Cah. O.R.S.T.O.M., sér. Ecu. méd, et Parasitol., vol. XII, no 1, 1974 : 15-18 $15 
M. MOTABAK AND N. ESHGHY 
thion at the rate of 2 gm /sq m has been applied since 1968. 
The secondary vectors such as A. d’thali, A. superpictus 
and A. fluviatilis with relatively exophilic .and exophagic 
habits are active in the area. Malaria transmission usually 
occurs during 8’ months (April-December) of the year, 
with the peak from mid-August to mid-October. 
The main larval breeding places are rice fields, canais 
and river banks. Due to rice season cultivation activity 
in July and the consequent extension of breeding sites, a 
remarkable increase in anopheline density has been 
observed in the .area. 
MATERIALS AND METHODS. 
AREA : A vast plain northwest of Kazeroun, which 
is almost entirely surrounded by mountains, was selected 
and 57 villages with a population of 11,445 were sprayed 
at a rate of 2 gm Sumithion sq m (99.6 % of temporary 
shelters and 96.1 % of permanent dwellings in the area 
were sprayed). The spraying operation lasted for 30 conse- 
cutive days in 1972 and two teams consisting of 20 spray- 
men, 2 mixers, 4 foremen and 2 team leaders were engaged 
in this operation. The operators were under systematic 
and closed clinical observation and cholinesterase determi- 
nation (tintometric method) during the operation as well 
as, in some cases, two months after it. 
The following entomological measures were conducted 
in five representative villages in the OMS-43 sprayed 
area and in two villages in the comparison area treated 
with Malathion: 
1. pyrethrum spray collection at ten-day intervals at 8 
fixed capture stations in each village; 
2. floor sheet collection-the number of dead mosquitoes 
found on sheets pread overnight on the floors of six sprayed 
shelters was counted at lO-day intervals; 
3. window trap collection-a total of 20 exit traps were 
installed, four window traps per village; 
4. shelter pit collections-20 artltïcial pits were examined 
at lO-day intervals in sprayed villages; 
5. night-biting collections on human and animal bait 
carried out at IO-day intervals in sprayed villages; 
6. vector age determination-Detinova’s method carried 
out in sprayed villages; 
7. larval density-collected in sprayed villages; 
8. biological evaluation on various surfaces of sprayed 
houses at 30-minute xposure with lab-bred A. stepfiensi was 
carried out at weekly intervals; about 600 mosquitoes were 
tested each time on sorbent and non-sorbent surfaces: 
9. susceptibility tests using the WHO technique with 
DDT, Malathion and Fenitrothion were carried out on 
A. stephensi. 
RESULTS AND DISCUSSION. 
A. TOXICOLOGICAL STUDY. 
In spite of the rigid instructions given to the spraymen 
to follow the necessary precautions, there were 42 cases 
of clinical symptoms. In some individuals several relapses 
occurred during the operation. No complaints or choline- 
sterase depression was observed during the first 2-week 
exposure. 
The majority of cases were mild and short, recovery 
resulted after washing and rest (2-3 hours), and most cases 
returned to work on the same day. 
The main clinical symptoms were headache, giddiness, 
nausea and abdominal cramps; some workers felt weak- 
ness. Diarrhoea was reported among two cases and 
was treated with Enterovioform (Ciba). 
A drop in whole blood ChE was seen among both 
mixers accompanied by clinical symptoms. One of the 
mixers left his job when his @hE was depressed to 12.5. 
Out of 20 spraymen, 8 showed depression of ChE, in 
some cases with clinical symptoms. After Atropine was 
injected and rest prescribed, recovery resulted. Among 
the 4 foremen (except one) and 2 team leaders, ChE 
depression was not significant (fig. 1). 
FIG. 1. - Whole blood cholinesterase depression among 
2 mixers (Ser. Nos. 21,22) and 4 spraymen (Ser. NOS 1,2, 
5, 13) during spraying period. 
Clinical investigation and laboratory tests among 
925 inhabitants of 5 villages, carried out 24 hours after 
insecticide application, showed only 15 cases with light 
symptoms. No significant change in ChE level was 
observed. 
16 Cah. O.R.S.T.O.M., sér. Ertt. méd. et Pauasital., vol. XII, no 1, 1974 : 15-18 
FIELD TRIAL OF SUMITHTON (O.M.S.-43) IN THE MAMASANI AREA 
TABL. 1. - Summary of entomological evaluation of OMS-43 on tl. stephensi n 5 treated villages, Mamasani, 1972. 
Days Indoor % Outdoor Floor 
-# /Bait /Night Bio-Assay 
Month after 
Exit Trap 
Resting Gravid, Collection Sheet 
Spraying den /but l?$ grav. 
% 
Parous 
den/pit (e dead) mortality Man Amn$ Rate Sorbent Non-Sor. 
Walls (wood) 
-- 
May. . . prespray 11 ii.05 0 0 1 ZZTZ 
June . . . )) 0.8 9.4 0.1 - - T--- 
1) 1 20 0.5 - - 23 = - 
July. . . >) 8.7 52.8 4:: 
0 
4.39.3 62.4 
)) 352.9 50.5 56 38.4 213 54.1 
Aug. . . 3 2.9 21.8 37 100 14.9- 27.1 9.8 96.9 100 10 11.4 z.4 
0:7 1::: 
18 16.6 % 
24.1 
% 
95.7 
20 3.5 
100 
9 100 2 3.8 92.1 100 
Sept. . . . ii 4.2 14.3 3.6 0 --- 2.1 4.7 3.5 83.1 100 
0.2 0 6.5 0.2 0.3 72.6 
50 0 
99.6 
0 0.05 0 z 0.1 0 63.3 98.6 
Oct. . . . 60 0.07 0 0.15 0 --- 0 0 40.0 
70 0 
93.9 
0 0.15 0 - 0 0.17 35.2 
80 
92.1 
0 0 0 - 0 0.5 27 89.8 -- 
Nov. . . . 90 0 0 Fi 0 --- 0 
100 0 - 0 : 
19.4 84.1 
0 0 8 67.6 
TABL. 2. - Summary of entomological studies of effect of Malathion on A. stephemi 
in two comparison villages, Mamasani, Iran, 1972. 
Mont11 
Days Indoor 
after 
% Gravid 
Collection and 
Spraying den. /but i/z Gravid 
Bio-Assay 
Sorbent 
mud walls Non-Sor. wood 
May. . . . . . . . . . pre-spray 0 - 
P 0 - 
June . . . . . , . . . . . 1) 0.1 20 % 
1) 2.2 65.7 -- 
July . . . . . . . . 1 » 10.9 Il 675.7 55 
1) 847.6 33.8 
Aug . . . . . . . . . . . . 11 997.6 37.9 
5 42.6 10.5 47.5 100 
15 9.3 26.2 57.8 
Sept.. . . 
100 
. . . . . . . 25 30.9 48.4 96.6 
35 2:: 41.8 41.8 92 
45 4.2 42.5 
oct. . . 
32.4 89 
. . . . . . . . i: 18.1 9.8 47.3 23.5 .7 83.3 
75 4.1 
Nov.. . . 
- 24.5 
. . . . . . . 85 0.06 - 18 z4 
95 0 - 11.7 39:6 
Cah. O.R.S.T.O.M., sér. Ent. méd. et Parasitol., vol. XII, no 1, 1974 : 15-18 17 
2 
M. MOTABAR AND N. ESHGHY 
This study showed that the consumption of Sumithion 
under local conditions (sub-tropics, hot dry season) was 
safe for residents, but its toxic effect on operators should 
be considered and further toxicological investigation 
with restricted safety measures which cari be used under 
tropical conditions are required. 
B. ENTOMOLOGICAL STUDY. 
- Pyrethrum spray catches showed a remarkable 
reduction in the indoor resting density of A. stepherui, 
i.e. from 352.9 per shelter before application of insecticide 
to 2.9, 11.4, 3.5, 4.2, 0.2 and zer’o aftewards (August- 
September). The number of empty, blood-fed, half 
gravid and gravid females was 1167 (8.3 x), 5820 (41.2 %), 
5339 (37.8 %) and 1972 (12.7 %) respectively before 
application, and 3 days after spraying these rates changed 
to 98 (82.4 %), 10 (8.4 %), 10 (8.4 %), 1 (0.8 %) respec- 
tively (tabl. 1). In the two comparison villages sprayed 
with Malathion, the density decreased from 997.6 per 
shelter before spraying to 42.6, 9.3, 7.5, 6.1, 4.2, 18.1 and 
19.8 in August-October (tabl. 2). 
- Exit trap observations indicated 100 % mortality 
within a 24-hour recovery period. Among the collected 
mosquitoes no higher stages of blood digestion were 
seen (tabl. 1). 
- The man-biting rate for A. stephaui was reduced 
during the course of collection, i.e. from 38.4 per bait 
per night before application to between zero and 16.6 per 
bait per night after spraying (tabl. 1). 
In spite of a remarkable decline in A. stepherzsi biting 
indices, the animal-biting rate of A. d’fhali during the 
same period of time was considerable, due to the relatively 
exophagic and exophilic habits of this species. 
- Ovary dissections revealed a drop of parous rate 
from 54.1 % and 62.4 % to between 3.5 % and 9.8 % 
after insecticide application (tabl. 1). 
- Bio-assay tests showed a mortality rate of 72.6 % 
on mud walls up to 40 days after spraying; this dropped 
to 8 % after 100 days. On non-sorbent surfaces (wood, 
rush mats), more than 67 % mortality was observed up 
to 100, days after spraying (tabl. 1). 
In the tests with one-hour exposure, 74.5 % and 
96 % mortality was observed on mud walls and wood 
respectively after 88 days insecticide application, and 
44.8 % and 74 % after 104 days. 
- Susceptibility tests using the WHO technique were 
carried out with regard to 0.1 ‘A and 1 % Fenitrothion 
(OMS-43) concentrations. The range of mortality after 
half-an-hour exposure followed by a 24-hour recovery 
period was observed to be between 0.0 % to 2.9 % and 
99.2 % to 100 % respectively, and with.one-hour exposure 
between 0.7 % to 5.8 % and 100 % respectively. 
The mortality rate with 0.5 %, 3.2 % and 5 % Mala- 
thion with one-hour exposure was 2.1 % to 19.2 %, 
93.6 % to 99.3 %, and 100 % respectively. 
In the case of 4 % DDT concentration with one and 
four hours exposure, the mortality rate was 0.0 % to 1 % 
and 8.9 % to 12.9 % respectively. 
Manuscrit reçu au S.C.D. le I8 dècemhre 1973. 
BIBLIOGRAPHIE 
DETINOVA (T. S.), 1962 - Age-grouping methods in 
Diptera of medical importance. Wld Hlth Org. Mo- 
nogr. Ser. 47, 216 p. 
ESHGHI (N.) et al. - Studies of the susceptibility level of 
anopheline mosquitoes to insecticide in different 
areas of Iran. I.P.H.R. Publ. 1816, Teheran. 
FRITZ (R. F.), 1972 - Operational evaluation of Feni- 
trothion for control of adult anophelines. WHO /VBC 1 
72.391. 
HADAWAY (A. B.), BARLOW (F.), GROSE (J. E. H.) and 
TURNER (C. R.), 1970 - Evaluation of compounds 
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Wld Hlfh Org., 42 : 553, 368. 
MOFIDI (Ch. M. H.), 1962 - Resistance of Anopheles (m.) 
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presentend to CENT0 Scientific Symposium, Labore, 
January 1962. 
MOTABAIZ (M.), 1971 - Observations and the effects on 
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18 Cah. O.R.S.T.O.M., sér. Ent. méd. et Parasitol., vol. XII, no 1, 1974 : 15-18 


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