WO2000000027A1

WO2000000027A1 - Method for repelling tsetse flies and other insects

Info

Publication number: WO2000000027A1
Application number: PCT/KE1999/000006
Authority: WO
Inventors: Rajinder Kumar Saini; Ahmed Hassanali
Original assignee: International Centre Of Insect Physiology And Ecology (Icipe)
Priority date: 1998-06-26
Filing date: 1999-06-22
Publication date: 2000-01-06
Also published as: AU4169699A; AP2003002854A0

Abstract

4-Methylguiacol (2-methoxy-4-methylphenol) and related compounds are potent repellents of tsetse flies. 4-Methylguiacol decreases by about 80 % the number of flies attracted to cattle with proportionate reduction in feeding efficiency. Such chemicals provide a useful tool in the integrated management of tsetse and trypanosomosis and other blood feeding insects.

Description

TITLE: METHOD FOR REPELLING TSETSE FLIES AND OTHER INSECTS

BACKGROUND ON INVENTION

Trypanosomosis is one of the most devastating diseases of animals and man in sub-

Saharan Africa and has a profound effect on rural development over vast areas. In fact

tsetse flies through the cyclical transmission of trypanosomes to both humans and

domestic animals, greatly influence food production, natural resource utilization and the

pattern of settlement throughout much of Africa. It is estimated that the annual direct

production losses in cattle alone amount to between USS 600 - 1.200 million, while losses

due to animal deaths may be as high as 3 million. About one-third of Africa is affected.

Where trypanosomosis prevails, the reduαion in livestock produαion ranges between 20

and 40%, depending on the degree of agricultural activity and rainfall.

Veαor control methods include appropriate land use taαics, periodic aerial and

ground spraying, odour bait traps and targets (with or without inseαicidal impregnation),

the sterile inseα technique and use of inseαicides in animal dips or pour-on formulations. No vaccine exists for the disease. Trypanocidal drugs as prophylactics or for treatment

are also widely used. However, only 3 drugs are available and all of them have been in the

market for nearly 40 years.

All current methods of control have certain disadvantages and none has proved to

be sustainable on its own. There is growing interest in new approaches that integrate vector control with disease treatment. These include strategic management of vector

populations at sustainable level using one of the methods outlined above integrated with limited use of trypanocidal drugs for the fewer animals that become infected. The use of potent repellents could similarly be integrated with disease treatment A significant reduction in tsetse challenge and concomitant reduction in disease v, ould reduce drug costs and increase proάuαivity. Repellents could also be used on trypanotolerant breeds of cattle to effect further protection of the animals. They could also be integrated with bait technologies in 'push - pull' strategies for the management of tsetse. They may also find use in barrier sysxems for minimising immigration of flies into cleared areas.

DESCRIPTION OF INVENTION

To date, no effeαive tsetse repellents are available for deployment in tsetse management tactics outlined in paragraph 3. The present invention is based on the demonstration that 4-alkyl substituted 2-methoxyphenols and related compounds are potent repellents for the Savannah group of flies and are suitable as environment-friendly agents for reducing tsetse challenge.

According to the invention, there is provided the use of compounds represented by formula (I) in repelling tsetse and other blood-feeding arthropods:

where X is an oxygen atom or nitrogen linked to a hydrogen (NH). Y is oxygen or nitrogen linked to eitr.er a hydrogen, an alkyl or substituted alkyl grc p. Z stands for hydrogen or fluorine. R¹ stands for an alkyl or substituted alkyl group, and R¹¹ stands for either hydrogen or substituent(s) on the benzene ring such as alkyl. i oroalkyl, halogen, alkoxy radicals, etc.

As examples of potentially useful repellent compounds there nay be mentioned ones where in structure (I), X is either oxygen or nitrogen (with hydrogen), Y is oxygen, Z is hydrogen or fluorine, R¹ is methyl or ethyl radical, and R¹¹ is hydrogen, as illustrated in (II), (III), (IV), and (V):

( π) ( m) ( iv) ( V)

Of these, compounds of choice in repelling Savannah species of tsetse is represented by formula (II).

As an important feature of the invention, there is provided the use of any compound represented by formula (I), singly or in combinations, to repel insects or other arthropods that use J-cresol (4-methylphenol) associated with host odours, alone or together with other host odour compounds, to locate their hosts or preferred feeding sites; these arthropods include tsetse flies, muscids, tachinids, tabinids, blaci-c flies, ticks etc. As a specific feature of the invention, there is provided the use of compounds represented by formula (I) to repel tsetse flies from livestock animals, human beings, or geographical locations, undertaken with the purpose of minimising tsetse bites and/or associated disease(s) they transmit.

It is to be understood that the invention is meant to include the use of all compositions containing any of the compounds represented by formula (I) prepared for the purpose stated in paragraphs 7 and 8. These may include formulations or concentrates containing standard diluents, solvents, dispersing agents, anti-oxidants. UV-screens, etc., added for convenience of use or proteαion of the active agent(s). Likewise, it is also to be understood that the invention includes all controlled-release formulations or devices prepared for convenience and/or extending the duration of performance of the active agents defined above or for providing greater spatial coverage on the animal or geographical locations.

It is to be understood further that the invention is meant to include the use of the said compounds, as formulations or in appropriate devices, to repel tsetse or other arthropods in all integrated control systems as outlined in paragraph 3, comprising appropriate land-use taαics, trypanocides, trypanotolerant animals, as well as to provide the 'push' effect in push-pull' strategies involving bait technologies. The invention is illustrated but not limited by the following examples

Example 1

Effect of repellent on trap catches

The efficacy of the repellent to decrease catches of odour baited traps was tested in a 4 x 4 latin square experiment in Nguruman, Kenya at two different sites and replicated twice. The treatments were NG2G trap baited with acetone and cow urine (control) and baited traps with 3 different doses (2.2, 5.0 and 9.0 mg/h) of the repellent. The repellent was dispensed from polythene sachets with 25 - 50 cm^" surface area and 150 micrometer thickness. The surface area of the sachets was varied to obtain the above release rates.

Results

The results of the above experiment are indicated in the Table 1.

The data clearly shows that baited trap catches were reduced by upto 80%) in the presence of the repellent (at high doses).

Table 1. Detransforined means and indices of catch of Glossina paUidipes with baited (cow urine + acetone)NGU traps and various doses of the repellent (2-methoxy-4-methylphenol) at two locations, Olaro track and Shompole, at Nguruman

Treatments Male Female Total

Dtrans- Index Dtrans- Index Dtrans- Index

Mean Mean Mean

a. Olaro track

Baited trap 292 a 10 660ab 10 1093 a 10 a (22 mg/h) 90b 031 215 b 032 311 b 028 b (50 mg/h) 139ab 048 165 be 025 278 b 025 c (90 mg/h) 70b 009 142c 021 224 b 015 b. Shompole

Baited trap 359 a 10 819a 10 1258 a 10 a (22mg/h) 166b 046 320 b 039 523 b 042 b (50 mg/h) 149b 042 349 b 043 51 Obc 041 c (90 mg/h) 132b 037 279 b 034 41 c 033

Means with different letters are significantly different at P<005 Baited tiap - NG2G tiap t acetone ι cow mine

Treatments a to c include baited NG2G tiap + various doses of repellent Repellent was dispensed from polythene sachets of various sizes

Example 2

Effect of Repellent on catches of ox odour

The effect of the repellent on the number of tsetse attracted to natural cattle odour were also determined. Natural cattle odour was obtained by placing an ox ι c 250 kg) in a roofed pit and exhausting the air from the pit via a ventilation shaft ( cm dia, 5 m long) fitted with a 12 V co-axial fan. Two such pits were constructed. To gauge the numbers of tsetse attracted to the odour, an electric net 1.0 x 1.0m was placed 80cm downwind of the odour source. Sheets of corrugated fiber glass coated with a thin film of polybutene were placed underneaή the electric screens to colleα the eieαrocuted flies. The treatments ( in a balanced incomplete latin square design) were: 1) ox odour; 2) ox odour + a visual model (a metal drum 501, 37 cm dia, covered with black cioth); 3) ox odour + repellent and 4) ox odour + visual model + repellent. The repellent ( 10 mg h) was dispensed from polythene sachets placed at the odour outlet. The experiments were conducted for 3 hours in the morning (0800 - 1100 hrs) and 3 hours in the afternoon (1400 - 1700 hrs.). Tr.e number of flies caught were recorded and the data statistically analysed.

Results The results of the above experiment are indicated in Table 2. It is clear that in the presence of the repellent catches with ox odour were reduced by more than 80%. Catches in the presence of a visual target and cattle odour were reduced by more than 70% by the repellent.

la ble 2. Means (+S ) and indicies ot catch ot ulosswap allimpes with electric ! screens in t he presence Ol OX 0 dour alone and in the presence of the re pellem t (2-methoxy- ■4-methylphenol)

Mean and indices of catch

Male Female Total

Treatment Mean Index Mean Index Mean Inde

Ox Odour 11.0 ± 2.9 ab 1.0 17.0±3.7a 1.0 28.016.5 a 1.0

Ox Odour + Repellent 2.2 ± 0.9 b 0.2 2.7 ± 0.4 b 0.15 4.8 ± 1 .1 b 0.17

Ox Odour + Model 14.2 ± 41 a 1.29 24.8 ±5.1 a 1.45 39.0 ±8.7 a 1.39

Ox Odour + Model + Repellent 3.0 ± 0.7 b 0.27 4.7 ±.0.9 b 0.27 7.7 ± 1 5 b 0.28

Release rate of the repellent was 10 mg/h

Number of replicates were six

Means followed by the same letters are not significantly different P>0.001

Example 3

Effect of Repellent on feeding efficiencv of tsetse flies

In order to estimate the effect of the repellent on feeding efficiency, an ox with or without the repellent was placed at the centre of an incomplete ring (8m diai of 5 electric nets. The nets covered about 20% of the circumference of the circle. Flies were separated according to the side of the net on which they were caught and classed as fed or unfed based on the presence or absence of red blood visible through the abdominal wall. The feeding efficiency was estimated as the number of fed tsetse caught on the inside of the ring of nets expressed as a percentage of the total catch from the inside of the ring.

The rings were constructed at two different locations and the treatments : ox alone or ox + repellent compared using a randomized block design. The treatments were randomly assigned to the two experimental sites. At the site which received the repellent treatment, the sachet containing the repellent (lOmg/h) was placed 50 cm from the animal. Since, in the experimental sites most flies were caught in the afternoon the experiments were run for 3 hours from 1500- 1800 hours daily. The animal was kept stationary but the repellent treatments were rotated after each experimental period.

Results

Table 3 shows the resuits of the above experiments.

The results clearly show that in all the experiments the feeding efficiency was significantly reduced when the repellent sachet was placed near the cattle. Table 3. Mean catches (+SE) and percentage feeding efficiency of Glossina pallidipes on cattle with or without the repellent ( 2 - methoxy-4-methylphenol)

Treatment Mean catch (±SE) Feeding efficiency¹

(Percentage)

Experiment 1

Cattle alone 45.5 ± 6.3 a 7.32 a

Cattle + Repellent 12.3 ± 1.6 b 1.52 b

Experiment 2

Cattle alone 82.6 ± 20.3 a 12.4 a

Cattle + repellent 24.2 ± 4.6 b 3.7 b

Experiment 3

Cattle alone 84.3 ± 17.3 a 19.1 a

Cattle + repellent 24.8 ± 2.8 b S.6 b

¹ Feeding efficiency is the total catch of fed flies inside the ring of screens expressed as proportion of the total catch (fed + unfed).

Ox was enclosed with incomplete ring 5 electric screens

Number of replications = 9

Means followed by different letters are significantly different at PO.01

Claims

1. A method of reducing tsetse challenge on cattle through the application of an effective amount of a repellent compound having the structural formula:

wherein, X = O or NH

Y = O, NH or N substituted singly with alkyl or substituted alkyl radical Z = H or F

R¹ = alkyl or substituted alkyl radical R^╧Ç = H or alkyl, fluoroalkyl, halogen, alkoxy radicals, etc.

2. The method of reducing tsetse challenge on cattle as described in claim 1 wherein the said compound is 2-methoxy-4-methylphenol represented by structure (LI).

3 The method as described in claim 1 wherein the arthropod may be another blood- feeding species such as muscids, tabinids, tachinids, black flies, ticks etc.

4. The method as described in claims 1, 2 or 3 wherein the said compounds are applied as mixtures or with other repellents for augmentative effe╬▒s.

5. The method as described in claims 1, 2, 3 or 4 wherein the said compound(s) is

(are) applied as a blend with a suitable carrier, diluent, additives such as antioxidants and UV-screens, or aromatic blends.

6. The method as described in claims 1, 2, 3, 4 and 5 wherein the compound(s) is (are) contained in suitable devices for convenience of handling and/or controlled- release and/or coverage over the whole animal.

7. The method as described in claims 1, 2, 3, 4, 5 and 6 wherein the host animals used are special breeds that are genetically/immunologically tolerant to the disease(s) transmitted by arthropods, such as trypanotolerant cattle.

8. A method of controlling tsetse or blood-feeding arthropods wherein the use of the

repellents, as described in claims 1, 2, 3, 4, 5 and 6 is (are) integrated with bait

technologies, including live baits (host animals), for augmentative 'push-pull'

effects.

9. A method of minimising re-invansion of tsetse or other arthropods into cleared

areas, or their immigration into peridomestic or domestic environments, through the deployment of the said compounds as described in claims 4, 5 and 6 in barrier

systems with/without bait technologies.

10. A method as described in claims 1, 2, 3, 4, 5 and 6 wherein the repellent(s) is (are)

formulated for use by humans.