Determination of LD50 of Propoxur on American Nymph cockroaches

Joseph Scott - 11986573

Pharmacology 1 - 91707

May 26, 2017

Introduction

The purpose of this experiment has the purpose to determine the definitive LD 50 of the Carbamate

insecticide Prodoxur when given to American nymph cockroaches.

The American nymph cockroach (Periplaneta Americana) at adult hood grow up to a average

length of 30-40mm in length (University Library University of Illinois at Urbana-Champaign) This is

the specimen used during this experiment. The selection criteria for the cockroaches used within this

experiment are of an approximate size of 2cm in length lacking the stage of their development giving

them wings. The point in the life cycle between birth and adult hood is referred to the nymph stage in

their development (Bell & Adiyodi 1981).

These cockroaches can become a public health hazard due to their association with human waste,

disease and their ability to move from sewers into households or commercial constructs. Their

presence is of epidemiological significance with at least 22 species of pathological human bacteria,

viruses, fungi and protozoans isolated from field collected American cockroaches (Rust MK, Reierson

DA, Hansgen KH. 1991).

Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573

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Figure 1: Life cycle of the nymph cockroach (University Library University of Illinois at Urbana-Champaign 2014)

Figure 2: American nymph

cockroaches and their excrement

(L.J. Buss, TR Fasulo, University

of Florida)

Many insecticides have been developed throughout the world. One of the most common forms of

insecticides used commercially in households are Organophosphate Carbamates which is the

generalized term for this category of insecticides. Within carbamates we focus on the use of Propoxur

Carbamates are used to kill or control insects. They are made from carbamic acid and come in many

forms, each different in how they work and their toxic effects towards the targeted insect.

Carbamates have low effect on the surrounding environment long term as they break down within

the environment in weeks to months (Delaware Health and Social Services). Carbamates work as

reversible inhibitor of cholinesterase, which is an essential nervous system enzyme of insects, this

results in a fast immobilization and death of the insects (Hayes 1982).

Propoxur is a non-synthetic insecticide that was introduced in the year 1959. Propoxur has a fast

knockdown and extended residual effect towards insects such as flies, fleas, ticks and as in the

experiment against cockroaches, in the household or environment. (Hayes & Laws 1990). There are

many forms purchasable of this product which affect its concentration spread and release such as

liquid and aerosol forms which are ready to use. (USDA 1992). The type used within this experiment

is in the form of powder, diluted into different concentrations.

Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573

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Figure 3: Carbamate mode of

action (University of

Technology Sydney 2017)

Figure 4: Chemical Structure

of Propoxur (university of

Technology Sydney 2017)

LD50 is referred to the Lethal Dose expected to eliminate half of an exposed population of individuals

(Stenersen 2004). The usual unit of dosage is in mg per kg (mg/kg). When there is only needed a

small dose to reach the LD50 than there is a higher level of toxicity while a higher dose required to

achieve the LD50 means there is a lower level of toxicity from the substance towards the organism.

The LD50 test is a procedure in which a substance such as insecticides is applied to animals such as

cockroaches with the purpose to determine the substances concentration needed to achieve a

predetermined rate of death reaching 50% of the test population (NSW Department of Primary

Industries 2013).

Method

Refer to pages 28-35 Pharmacology 1 Subject Number 91707 Course Practical Manuel, Autumn

Semester 2017 (University of Technology, Sydney 2017).

Results

Notes:

Concentrations determined by demonstrator.

Purity of stock samples of propoxur (97.6%).

Table 1. The death percentage of American Nymph cockroaches to propoxur at varied concentrations (group and class results).

Concentrations (% W/V) Roach Fidty (RF) % Death Class average % DeathControl 0.00 0.00

0.01 20.00 16.250.02 70.00 42.500.05 70.00 68.750.10 100.00 83.75

Notes:

Class Average result from all 8 Groups.

Roach Fidty (RF) singled out as our own group.

There is a duplicate of 2 cups for each concentration to achieve greater accuracy.

The percentage of death is calculated by the measurement of the number of dead cockroaches

after a 24-hour period after cockroaches have been exposed to propoxur to the presence of 5

cockroaches per 1 cup.

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Data shows that as dose concentration increases so does death rate.

Average Weight of each cockroache from RF = 0.56g. from Class = 0.48g.

Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573

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Figure 5: Log-Linear

graph based on

experimental results of

RF and Class average to

determine the LD50.

Figure 6: Log-Probit

graph based on

experimental results of

RF and Class average to

determine the LD50.

Table 2: LD50 average w/v determination based off experimental result graphs.

Log Linear Log Probit AverageLD50 Group RF (w/v) 0.021 0.018 0.039LD50 Class (w/v) 0.030 0.031 0.0305Average 0.0255 0.0245

Table 3: Calculation from percentage w/v to mg/kg.

LD50 From Log Linear Group LD50 From Log Probit Group= 0.021 w/v= 0.021 g/100ml= 0.00021 g/ml= 0.00021 mg/ul – per cockroach injection divided by average weight from RF group= 0.00021 mg/0.56g= 0.000375 mg/g= 0.375 mg/kg

= 0.018 w/v= 0.018 g/100ml= 0.00018 g/ml= 0.00018 mg/ul – divided from average weight per 1 cockroach RF group= 0.00018 mg/0.56g= 0.000321 mg/g= 0.321 mg/kg

LD50 From Log Linear Class LD50 from Log Probit Class= 0.03 w/v= 0.0003 mg/ulDivide by average class weight= 0.0003 mg/0.48g= 0.000625 mg/g= 0.625 mg/kg

= 0.31 w/v= 0.00031 mg/ulDivide by average class weight= 0.00031 mg/0.48g= 0.000646 mg/g=0.646 mg/kg

Table 4: Propoxur LD50 of American nymph cockroaches by group and class results calculated from

linear and probit log graphs

Log Linear Log Probit AverageLD50 Group (mg/kg) 0.375 0.321 0.348LD50 Class (mg/kg) 0.625 0.646 0.636Average 0.500 0.484

Discussion

The LD50 found by RF and Class results of Propoxur on American Nymph Cockroaches were

0.348 mg/kg and 0.636 mg/kg respectively.

In 1999 a study was performed by Valles, Koehler and Brenner of which they determined

the LD50 of propoxur towards American Nymph Cockroaches was 0.65mg/kg. the class

Determination of LD50 of Propoxur on American Nymph cockroaches | Joseph Scott - 11986573

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results closely represent the same result as their experiment, while the RF group was below

their experimental found value.

There can be many sources of variation within the experiment, a few of these can include

but are not limited to:

Different size / length of cockroaches used (measurement of individual cockroaches

was difficult due to their nature to move run around).

The RF group has an outlier on the 0.2 w/v propoxur concentration that caused a higher

line of best fit giving a lower Ld50.

Application of 1ul dose to cockroaches as application due to cockroach movement was

difficult which could have caused bad placement of propoxur.

Recommendations for the improvement of this experiment for future studies.

Weighing of individual cockroaches to get more consistent and specific results.

Exact measure each individual cockroach between group and class as to assure less

variation.

Differentiate females to males as their weights vary.

Maintain health of test population.

Produce more test samples, more cockroaches per cup/ more cups for greater accuracy.

Table 4 has shown that the average calculation for the log linear as well as the log probit

graphs provide similar results. The log probit graph shows better results than that of the log

linear graph for the class results but not as good for the RF results. This result for RF may be

due to the outlier on the 0.2 w/v concentration pushing the Ld50 backwards. These

improved results on the Log probit graph may be due to its extended section between the

10/90 range for horizontal observation. By following the line of best fit we can see that on

the log probit graph the results are much easier to determine while the log linear graph

raises results quickly over a small area making it difficult to determine the LD50

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References

1. Bell WJ, Adiyodi KG. 1981. The American Cockroach. Chapman and Hall, London.

2. Fasulo TR. (2002). Cockroaches and Pest Ants. University of Florida

3. Hayes, W. J. 1982, Pesticides studied in man, Williams and Wilkins, Maryland.

4. Hayes, W.J. & Laws E.R. (ed.). 1990, Handbook of pesticide toxicology, Vol. 3, Classes of

pesticides. Academic Press Inc, New York

5. University Library University of Illinois at Urbana-Champaign 2014, IPM photo reference,

viewed 20th May 2017,

6. University of Technology Sydney. 2017, ‘Pharmacology 1 autumn semester 2017’, UTS

Online Subject 91707, course Manual

7. University of Technology Sydney. 2017, ‘Pharmacology 1 autumn semester 2017’, Lecture

insecticides 1/2 'Pharmacol1 L1-2 Insecticides.pdf

8. USDA. 1992, The biologic and economic assessment of propoxur. NAPIAP, Extension Service,

USDA, Washington, DC.

9. NSW Department of Primary Industries 2013, LD50 and lethality testing, viewed 20th May

2017, <http://www.animalethics.org.au/accreditation-and-licensing/ld50-and-lethality-

testing>.

10. Valles, S. M., Koehler, P. G., Brenner, R. J. 1999, Comparative insecticide susceptibility and

detoxification activities among pestiferous Blattodea. Elsevier Science enzyme

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