WC~~.LD
HEALT::-i -JRGANIZATION
NHO; 'iBC/68 .l.C4
ORGA.i'TISATION .YiONDIALE DE LA SANTE
ENGLISH ONLY
, A ?Il..LAGE SCALE TRIAL OF OMS-597~ FOR THE CONTROL OF AN. ·3AMBIAE Al'{D AN. FIJNESTUS IN NORTHERN NIGERIA
by .f.
c.
P. Pant,
J;'.
R.osen, :\1. Ramasamy, G. Joshi, P. Renaud, J. Pearson .V"rlO Anopheles Control Research Unit I Kaduna, Nigeria SUMMARY
2
The Anopheles Control Research Unit, conducted a village scale trial of OMS-597 wdp near Kaduna in 1967. This insecticide gave good control of An.gambiae and An, funestus for a twomonth period.
OMS-597 has been shown to be an effective insecticide against anophelines in Stage II tests carried out in Savannah, Gainesville and Porton. 3 It has also given satisfactory 3 performance in the experimental hut tests (Stage IV) conducted at Arusha and Bobo Dioulasso. . In continuation of the WHO Programme for the Evaluation and Testing of New Insecticides, the Anopheles Control Research Unit carried out a village scale trial of this insecticide in the Guinea savannah region of Northern Nigeria near Kaduna for the control of An. gambiae and An. funestus. Vandekar & Wilford 3 confirmed the safety of this insecticide to the operators and the inhabitants of sprayed dwellings; Ramasamy, and Renaud4 reported on the storage stability of this insecticide, MATERIALS AND METHODS Area of operations - The villages of Hayan Gada and part of Buruku located about 20 miles west of Kaduna with a population of about 600 and 292, respectivel~were sprayed, and Sabon Gida was observed as the comparison village. These are typical Hausa villages as described by Service (1964) and Pant & Self (1966). The villages have permanent sources of anophelines within one mile of their boundaries. For entomological assessment of spraying only Hayan Gada was utilized.
Active ingredients are 3,4,5 and 2,3,5 trimethylphenyl methylcarbamates, (also known as SD 8530 and landrin). 2 Project Leader, Entomologist, Chemist, Entomologist, Chemistry Technical Officer and Sanitarian, respectively. 3 . Unpubl1shed document WHO/VBC/68.99. 4
1
Unpublished document WHO/VBC/68.102.
The issue of this document does not constitute formal publication. lt should not be reviewed, abstracted or quoted 'Nithout the agreement of the World Health Organization. Authors alone are responsible for views expressed in signed articles.
Ce document ne constitue pas une publication. 11 ne doit faire l'objet d'aucun compte rendu ou resume ni d'aucune citation sans l'autorisation de !'Organisation Mondiale de la Sante. Les opinions exprimees dans les articles signes n'engagent que leurs auteurs.
WHO/VBC/68.104 page 2 Soraying operations - A 50% wdp of GMS-597 was sprayed as a 5% suspensi:Jn using i-Iudson compression spray pumps fitted with HSS 8002 nozzle tips giving an oucpm; of 750 ml/ minuta at 40 lbf/in2 (2.81 kgf/cm 2 )~ The spraymen were trained to spray at the ra-ce of 19m2 minute (target dose 2g/m2). For the protection of spraymen, clean overalls were -.vorn each a.ay along -.vi th plastic shoes and southwesters. Soap and water was provided at the mixing poLn for frequent -nashing of spraymen' s hands and faces. The mixer handling the concentrate -.vore long rubber gloves. ;~-pert
Chemistry - On arrival the OMS-597 wdp formulation was checked for acti'Je ingredient ccntent, suspensibility, and other criteria in conformity with the WHO interim specification. Representative samples were kept in well sealed bottles and analysis carried out at regular intervals to determine the storage stability under Kaduna conditions. The active ingredient content was determined by hydrolysis with 60% sulfuric acid under reflux. The methyl amine formed was distilled into 2% boric acid solution and titrated directly against standard 0.1 N sulfuric acid using bromocresal green indicator. The manufacturing process yields a technical product of OMS-597 consisting of approximately 80% 3,4,5 triroethylphenyl methylcarbamate and 20% 2,3,5 trimethylphenyl methylcarbamate. The above method of determining active ingredient does not distinguish between the two isomers. The suspensibility determinations were made with a prepared suspension containing 2.5% w/v of trimethylphenyl carbamate in a specially designed 250 ml graduated cylinder as described in the WHO Specifications for Pesticides (1:967). Entomology - The residual effectiveness of the treatment was determined by making comparative entomological observations in the treated village of Hayan Gada and the untreated village Sabon Gida located in the same general area. Observations were made every 15 days, of the following: (a) Number of anophelines resting in the huts in the morning as shown by pyrethrum spray collections. These were identified to species, sex and abdominal condition. some cases age grading into parous and nulliparous groups was also carried out. (b) Number of anophelines leaving the huts as shown by exit (door) trap collections. Their species, sex, abdominal stage and the 24-hour survival rate was also recorded. (c) Bio-assays according to the procedure laid down by the WHO Expert Committee on Insecticides (1963) were carried out on the thatch and mud walls employing fed, colony produced Ae. aegypti. RESULTS Operations - The formulation proved difficult to mix, caused frothing when poured into the sprayer and a sediment formed before the sprayer charge was finished.l It was also noted that it eroded the nozzle tips excessively. 2 An increase in output by 30.50% was noted in the pumps after four days of spraying. This caused overdosage in the latter part of the applications. The over-all dosage was 2.6 g/m2. Entomology - Hut resting densities of An. gambiae and An. funestus were reduced to zero for more Lhan a month after spraying. (See Tables land 2). Exit trap collections were less than one per hut for this period. Comparable hut resting and exit trap collections in the unsprayed village during this time were 16-21 per hut for An. gambiae and 30-40 for An. funestus. Bio-assay mortalities on mud dropped below 70% by 35 days after spraying but remained satisfactory on thatch through 49 days. (See Table 3). During the second month after
In
l
Editor's noLe- manufacturer indicates that formulation problems are rectified. Nozzle tips were noc of the new hardened "C" metal.
2
.NH0/'130/68 .104 page 3 :rea-::nen: -:I1e1:·e ·vas 3. 32.igh:: ·::Jt:.: ~1,~-::. >:?aj:e ::"3DC :;:: :iensi ~~' :.~c::..""9ase ., ?8d/g~~"l1.:.-2 An. gambiae a.nd _.m, :·unestus ·vere :1.:.sc Gol:.actaa iur:.ng the 3econd month 3.nd on :::e thirt•Tsixth day after ::reatment there vas no :norta_;_:.c;y (:fed,'gr3.v:.ds; ot:fcer 24 hours 3lllong :'ive An. gambiae .1.nd ::.ve An. :funes--c~s ,~c::llec-:ec: :f:... . Clm lQ hu:3. ~i"!us -:he:-s -vas :3vidence :Jf a breakdown of :he e:::::'acci veness ,_Jf OMS-397. 3i-J-3.ssay :nor-:aii ties during the second month on mud ·.val::.s and thatched roofs l-:ad gene io'-'m. :::uring -:he ;;;,L·d :nonth ':liter cl·ea:::nen: and onwards there was a markad increase i::1 the hue densi:::ies :"Fig, l).
These criteria showed that the i:lsec-::::.:;ide was ef:':ecti-Je treatment.
~P
to abou:; two mcm:hs after
Formulation properties - The insecticide samples conformed to the requirements of WHO Specifications for ?esticides on arri7al. (See Table 4). A small amount of sediment in the form of a fai:·ly hard cake was depcsi ted at the bottom of the cylinders used fer suspensibili -;;;y determinations. This sediment on chemical analysis was found to contain 69% fillers. The sediment collected from the spray pumps contained 97,5% fillers. The formulation did not show any significant change either in the active ingredient content or suspensibility after 10 months of stcr~ge under tropical conditions. The drop in suspensibility after 10 months of storage was 4.7%. DISCUSSION During the fi~st month after treatment OMS-597 gave excellent control of both -~· gambiae and An. funestus. During the second month there was an increase in the number of anophelines collected in the exit traps some of which survived 24 hours. During the third month after treatment there was an increase in the numbers of mosquitos collected in the traps a majority of which survived the 24-hour holding period. Pyrethrum spray collections were low for two months. It has been shown by bio-assays that the compound stays on the thatched surface much longer than mud walls. It has also been shown that the majority of An. gambiae and An. funestus rest on the roofs in the Kaduna area. This may account for low numbers in pyrethrum spr~y collections. However, as the increase in numbers in exit traps, a significant number of which were fed or gravid, during the third month was so great it can be concluded t~at this insecticide was effective for only two months. It should be noted that the densi ti.8s in the treated village remain very low as compared to those of the comparison village because the potential for density increase is apparently lowered after a spray treatment. However, the bio-assay mortalities and the survivors in the traps are important considerations. Bio-assays of mud walls (see Fig. 2) showed mortalities of only 60-70% in the anophelines and 44.4% in the case of Ae. aegypti, 49 days after treatment. By the sixty-second day, mortality of An. gambiae was down to 9.4% compared with 12% for An. funestus and 17.5% for Ae. aegypti. On thatched surface, bio-assays gave a 95% kill of anophelines on the fortyninth day but fell sharply by the sixty-second day (68.2% for An. gambiae, 46,1% for An. funestus and O% for Ae. aegypti). The crend of increase in densicy in the treated huts very clearly demonstrates the point where the insecticide lost effectiveness (Fig. 1). Although pyrethrum spray collections in the sprayed area were low compared with those of the unsprayed area, up to three months after treatment, "the combined pyrethrum spray catch and exit trap figures were sufficiently high during the second month of treatment to be considered epidemiologically significant. During che fourth and fifth month after spraying, anopheline densities in the Kaduna area declined, ~ut sufficient An. funestus were entering the huts and surviving to indicace the loss of activicy of OMS-597.
WHO/VBC/68.::.04 page 4 During c;<e :::rial no adverse ~ffects ,.Jn spraymen wsre observed clinical2.y and :10 compLlints were :nade ~JY i;J.haoi tar..ts .:)f the sprayed vl::_lages ('!andekar & Wilford, unpublished repor::).
CONCLUSIONS l.
OMS-597 applied at a ~arget dose of 2 g/m An. funestus for about cwo monchs.
2
gave good control of i\n. gambiae and
However, it did The formulation gave some problems with sedimentation and erosion. 2. conform to the WHO Interim specifications and there was no deterioration of the active ingredient on tropical storage for 10 months,
ACKNOWLEDGEMENTS We are grateful to the Permanent Secretary of the Ministry of Health, Kaduna, Dr J. D. Soleye for his co-operation and assistance to this project. We also wish to thank ~r T. M, Leach, Director, NITR, Kaduna for providing laboratory facilities. REFERENCES Service, M. W. (1964) Bull. ent. Res.,~'
29-34 ~,
Pant, C. P. & Self, L. S.
(1966) Bull. Wld Hlth Org.,
709-719
WHO Expert Committee on Insecticides (1963) Wld Hlth Org. techn. Rep. Ser., 265, 227 pp. WHO 1967 Specification for pesticides used in public health, World Health Organization, Geneva, 300 pp.
1 TABLE 1. SUMMARY OF ENTOMOLOGICAL DATA FROM OMS-597 SPkAYED AREA (Date of spraying - 12 July 1967) Anopheles gambt~e
-· Days Date** after spraying
Sprayed area Average per hut 17.7 13.2
--·--
Pyrethrum spray collection
Exit (door) trap collection* ---.~--
-Unsprayed area Average per hut Sprayed area Average per hut 6_.6 4.9 Total fed/ gravids 31 28
% gravids
% gravids 7.9 10.8
% 24 hr mortality 3.2 3.5
Unsprayet areu ··--- --------··-Average 'l'otal f< d/ % 24 hr wortality gravid s per hut
I
-- ------
Jun.
9 23 7 21 4 17 31
Prespray
-
" Jul.
" " 9 22 36 50 64 78 92 106 120 134 148 162
14.6 11.1 14.2 7.4 2.9 6.1 3.3 2.0 1.2 0.2 0.2 0.0 0.0
22.6 13.5 41.5 28.3 27.6 36.0 0.0 45.0 0.0 I*** I***
4.4 9.2 7.2 8.9 2.2 11.0 14.3 10.5 4.0 0.5 0.1
25 69 57 66 14
0.0 0.0 0.0 0.0 0.1 0.6 0.5 0.2 0.4 0.1 0.0 0.0
-
0.0 0.1 0.8 0.1 1.6 3.2 2.0 1.3 0.8 0.3 0.0 0.0
0.0 0.0 5 0.0 8 22 8 5 5 1
-
4.0 2.9 12.2 3.0 7.1 4.0 1.7 2.7 19.0
" Aug.
-
0.0
" "
I*** 3*** 0 0 0 1***
0.0 0.0 r*** I*** 0 0
Sept. 14
75 114 36 21 1 0 1
" " Nov.
28
Oct. 12 26 9 23 7 21
" Dec.
0
-
-
-
-
0.1 0.0
" Note:
-
-
-
'Cl Ill ()Q
* **
..:
Ten huts were examined on each occasion. Within a week comparable observation in the
::r. 0
(!)
"'·
<:
Dates in the first column refer to observation in the unsprayed village. treated village was made.
(J1
'· ..... Q") OJ
("')
to
*** Actual number.
When fewer than 20 mosquitos were examined, no percentage figures were calculated.
..... 0
""-
TABLE 2.
SUMMARY OF ENTOMOLOGICAL DATA FROM OMS-597 SPRAYED AREA (Date of spraying - 12 July 1967) Anopheles funestus
'-o
!lJ
l)q
0 CD "--O)I:Jj ()
< ::r: <
-·--------Morning flit catch * Date** Days after spraying Unsprayed area Average per hut Sprayed area Average per hut 6.5 3.9 Sprayed area Average per hut 3.4 3.3 Total fed/ gravids 19 22 Door trap *
" 0
0)
00 f-'
-------Unsprayed area
"'-
% gravids
% gravids 10.7 25.6
% 24 hr mortality 2 dead 0.0
Average per hut
Total fed/ gravids
-% 24 hr mortality
Jun. 11
9 23 7 21 4 17 31
Prespray 11
21.4
30.3 53.0 39.2 23.9 55.8 36.1 28.4 33.1 37.5 55.8 28.8 28.7 36.0
15.0 22.1 20.2 14.3 8.1 25.0 20.3 44.3 51.6 24.6 5.5 2.4 1.6 ---'---
117 171 152 94 60 163 144 282 368 197 44 17 12
-0.0 7.6 14.4 11.1 10.6 3.0 6.2 19.5 25.2 61.4 47.7 11 ***
Jul. 11
11
0.1 0.1 0.0 0.1 0.0 0.2 1.1 1.0 1.6 1.1 0.1 0.3 0 0 0 0 0
-
0.2 0.6 0 0 5 1 2 4 4 12 2 6 3 2
-
-
9 22 36 50 64 78 92 106 120 134 148 162
19.4 17.1 17.0 10.2 16.6 23.2 42.5 29.6 35.1 11.1 8.0 6.1
Aug. 11
0 0 0 2*** 0 0 0 1*** 2*** 1 ***
-
1.0 0.2
11
Sept. 14 11
-
1.4 1.2 3.1 2.1 1.4 2.0 0.5 0.4
28
Oct. 12 11
26 9 23 7 21
1*** 1*** 3*** 1*** 3 ***
Nov. 11
Dec. 11
6
***
'--·
--
Note:
* **
Ten huts were examined on each occasion. Within a week comparable observation ill the
Dates in the first column refer to observation in the unsprayed village. treated village was made.
*** Actual number.
When fewer than 20 mosquitos were examined, no percentage figures were caleul11ted.
"NHO/VBC/ 68. 104 page 7 TABLE 3. RESULTS OF BIG-ASSAYS OF OMS-597 TREATED SURFACES USING WILD CAUGHT (FED/GRAVID) ANOPHELINES AND LABORATORY BRED AEDES AEGYPTI (period of exposure 30 minutes) ·-
Days after treatment
24 hour % mortality An. gambiae An. funestus
Ae.
ae~pti
Temperature exposure
Humidity exposure
MUD WALLS 7 21 35 49 62 76* 91 105 100.0 (64) 84.0 (50) 63.3 (30) 61.5 (65) 9.4 (74) 48.9 (92) 25.0 (4)
69.1 (55) 71.0 (lOO) 12.0 (23) 53.1 (64) 28.3 (155) 14.0 (144) THATCH ROOFS
97.1 (69) 57.9 (88) ..
78 76 74 74 76 81 82 72
74 91 87 96 87 76.5 80 74.5
-
44.4 (81) 17.5 (91) 2.0 (97) 6.5 (91) 2.0 (98)
95.8 (24) 68.2 (41) 41.1 (34) 50.0 (6)
21 49 62 76 91 105
94.8 (39) 46.1 (26) 56.2 (32) 45.7 (59) 10.3 (58) .
80.0, (15)
76 74
91 96 87 76.5 80 .74.5
0 0 (22) (20) 17.4 (23)
76 81 82 72
-
o· (22)
* 1. 2.
Exposure period on this day ·was one hour.·
Note: The number of mosquitos exposed:are given within parenthesis. Control morta1ities were all below 5%.
TABLE 4. Date received at this unit: Date of sampling :
RESULTS OF STABILITY TESTS OF OMS-597 - 50% WDP Batch no. SD 8530 Code 3-3-3-13 No. of drums: eight Date of analyses: 10.5.67 to 24.5.67 Sieve test Suspensibili ty pH of 10% w/v after Suspensibility suspension in hard water in hard water accelerated after in 25 ml acetone storage without b accelerated + 75 ml distilled pre-treatment% retained storageb,c water on BS 200 mesh 85.7 86.2 85.3 86.7 85.5 86.2 85.0 84.5 85.7 84.1 84.2 84.1 84.0 83.7 84.8 84.1 81.6 83.8 0.27 0.30 0.13 0.31 0.57 0.38 0.63 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 -·
llQ
'2
CD ~ ())I:IJ ()
0
~
8.4.67 5.5.67
'-....
en ())
f-'
0
.!»
Drum No.
Active ingredient % w/w~
Suspensibili ty in distilled water withoub pre-treatment-
Alkalinity as NaoH (% w/w)
1 2 3 4 5 6 7 8 Average of all drums
50.9 51.0 51.1 51.2 51.3 51.5 51.4 51.3 51.2
85.6 86.4 86.6 86.4 85.9 87.1 85.4 86.2 86.2
0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03
o. 71 0.41
a - Methyl-amine method (WHO Interim specifications for OMS-33.
--
Water dispersible powders 2.0033
=2
para 2.1.2). The active
£A suspension containing 2.5% w/v of 3,4,5 and 2,3,5 trimethylphenyl methylcarbamates was employed. ingredients in the prepared suspension were determined by the methyl-amine method (~) given above.
£The accelerated storage test was carried out by maintaining the sample at 54 ~ 1 °C for 24 hours with an added pressure 2 of 25 g/cm applied to the powder.
"'l
FIG. 1 COMBINED PYRETHRUM AND EXIT TRAP COLLECTIONS IN THE OMS 59'7 SPfUWED VILU\CI
6·--·-· >,
.A
An. gambiae.
§ 5 ·(/)
o An. funestus
Q)
ro
E
2 ~
4 ·..I..
=
::::3
·-
Q) (/'J
a.
3 ·-
':::3 (/)
..8
= ~ 2 c:: Q)
0
0
OD Q)
~
1 0 0
<::(
>
• ... 0
0
' - - - - - - - - ' - - - - - ' - - - - - ' - - - - ' - - - - - ' - - - - ' - - - - . J . . - - - ' - - - L - - _ _ ! _ __
0
10
20
30
40
50
60
70
80
90
100
110
Days after spraying
WllO Hl itJtJ
FiG. 2
RESUL IS OF BIOASSA YS OF OMS 597 ON MUD 'f/tl,LLS AND THATCHED SURFACES
lOO :
80 ~
' I :~ ' l i
~
a,
Test insect: An. gambiae
b~
>ro
so :~ 40 20
''
:2:
0
I 0 10
I I
I
I
'
"' ' ' "b--70 80
..D
20
30
40
50
60
90
100
110
Days after treatment
100 80 ~ ~
I
L I I I
~
\
Test Insect: An. funestus
\
>-
50 L I 40 120 ~
\
\
~ ~
m 0
b---..o--
--"'\
:2:
' 10
! 0 20 30 40 50 60 70 80 90 Days after treatment
'
~
lOO
110
100
80 ~ ~
Test insect, Ae. aegypri
>-
60 40 1~ 20
m
:2:
0
~ I 0
'' 10 20 30 40
'' 50
''' 60
o----o' ~
A
.... '
70
80
90
lOO .'vl--l:'::
-
110
Days after treatment o--- -o Thatched roofs 0
-~:._ "'~7
o Mud walls