iophenoxic acid as a bait marker for wild mammals: efficacy and safety considerations

REVIEW

Iophenoxic acid as a bait marker for wild mammals:efficacy and safety considerations

Cristina BALLESTEROS* Instituto de Investigación en Recursos Cinegéticos, IREC(CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13071 Ciudad Real, Spain.E-mail: [email protected]ël SAGE Game and Wildlife Agency/Office National de la Chasse et de laFaune Sauvage, Wildlife Sanitary Unit/Unité Sanitaire de la Faune, F 67150,Gerstheim, France. E-mail: [email protected] FISHER Pest Control Technologies Team, Landcare Research, PO Box 40,Lincoln 7640, New Zealand. E-mail: [email protected] MASSEI The Food and Environment Research Agency, Sand Hutton,York YO41 1LZ, UK. E-mail: [email protected] MATEO Instituto de Investigación en Recursos Cinegéticos, IREC(CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13071 Ciudad Real, Spain.E-mail: [email protected]é DE LA FUENTE Instituto de Investigación en Recursos Cinegéticos, IREC(CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13071 Ciudad Real, Spain, andDepartment of Veterinary Pathobiology, Center for Veterinary HealthSciences, Oklahoma State University, Stillwater, OK 74078, USA.E-mail: [email protected] ROSSI Game and Wildlife Agency/Office National de la Chasse et de laFaune Sauvage, Wildlife Sanitary Unit/Unité Sanitaire de la Faune, F 67150,Gerstheim, France. E-mail: [email protected] GORTÁZAR Instituto de Investigación en Recursos Cinegéticos, IREC(CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13071 Ciudad Real, Spain.E-mail: [email protected]

ABSTRACT1. Bait delivery of vaccines, toxicants or contraceptives to target wild mammals is anessential component of management strategies worldwide. Marking agents arerequired to enable the identification of individuals that consume the baits in orderto evaluate and optimize the cost-efficacy of baiting campaigns.2. Ethyl-iophenoxic acid (Et-IPA) is an organic iodine-containing compound that hasbeen used increasingly since the 1980s as a bait marker. It binds to proteins in animalblood and therefore can be detected indirectly by measuring plasma or serum iodineconcentration or directly by measuring plasma or serum Et-IPA concentration withliquid chromatography. Methyl-iophenoxic acid and propyl-iophenoxic acid can alsobe used to provide quantitative information on temporal or spatial patterns of baitconsumption in a range of mammalian species. We review the suitability of Et-IPAand its analogues as bait markers in mammals.

*Correspondence author.

bs_bs_banner

Mammal Rev. 2012

© 2012 The Authors. Mammal Review © 2012 Mammal Society/Blackwell Publishing

3. The highly variable persistence of analogues and in species highlights the need forcalibration testing of each compound as a marker for each species and for eachproposed use before starting a bait delivery trial.4. After absorption, the fate of IPAs (by metabolism, distribution and excretion) isvariable, but most are bound to plasma proteins. Marking efficacy is therefore high.5. The implications of exposure to IPAs for predators and humans were analyzed toevaluate its safety for delivery to wild mammals. Although it is highly unlikely thatsecondary exposure through ingestion could involve sufficiently large quantities toproduce adverse effects, further studies are necessary to assess long-term effectsafter chronic exposure to these compounds.6. IPAs can mark animal serum for long periods of time, and improvements indetection methods for them are currently being developed, so that they are a goodchoice for oral baiting field experiments with mammals.

Keywords: baiting campaign, iophenoxic acid, marker, vaccination, wildlife

Mammal Review (2012)doi: 10.1111/j.1365-2907.2012.00213.x

INTRODUCTIONBait delivery of vaccines, antiparasitic drugs, toxicants or contraceptives to targetwild mammals is an essential component of population and disease managementstrategies worldwide. Field assessment of the proportion of target and non-targetindividuals that consume baits is crucial, as a means to evaluate and optimize the cost-efficacy of a baiting campaign. A wide variety of substances including dyes, radioac-tive and stable isotopes, inert particles and systemically absorbed chemicals has beenused as marking agents or bait markers to enable the identification of individualsthat have consumed at least one bait (Savarie et al. 1992, Fry & Dunbar 2007).

Among the various types of bait markers, systemic markers are chemical com-pounds that, after ingestion, leave a detectable mark on internal tissues such asblood or in hair and whiskers (Fry & Dunbar 2007). A wide range of compoundshave been tested and subsequently used as systemic markers in management studies,with variable success and persistence of marking. Among these compounds,ethyl-iophenoxic acid (a-ethyl-3-hydroxy-2,4,6-triiodohydrocinnamic acid; hereafterEt-IPA) has been commonly used in bait delivery trials (Fletcher et al. 1990, Trewhellaet al. 1991, Linhart et al. 1994, Forsyth & Parkes 1995, Fleming 1997, Mitchell 1998,Ogilvie & Eason 1998, Marks & Bloomfield 1999, Fleming et al. 2000, Southey et al.2001, Cagnacci et al. 2006, 2007, Campbell et al. 2006, Cowled et al. 2008). Et-IPA isan organic iodine-containing compound that, due to its low systemic toxicity andlack of harmful side effects, was used clinically in humans in the early 1950s as an oralcholecystographic medium (to visualize the gall bladder) under the trade name ofTeridax (Shapiro 1953). Between 3 and 4.5g of the compound, equivalent to64mg kg-1 in a 70kg human, was administered to each patient (Hoffmann 1954).

After administration, Et-IPA is metabolized in the liver and excreted into the bileas the glucuronide conjugates, which makes this compound an excellent gall bladdervisualization agent (Margolin et al. 1953). However, it was proven to cause pro-longed elevation of serum iodine levels that interfered with thyroid function tests. Itwas withdrawn from clinical use in 1957 because of its long persistence in plasma

2 C. Ballesteros et al.


(half-life in human plasma is c. 2.5 years; Astwood 1957, Hall & VanderLaan 1961).The compound was replaced by the closely related iopanoic acid, which has a muchshorter half-life (~2 weeks; Mudge et al. 1978).

The highly persistent and apparently benign nature of Et-IPA indicated that itwould be a good bait marker (Larson et al. 1981). After ingestion, Et-IPA produceselevated blood iodine concentrations that can be detected indirectly by measuringplasma or serum iodine (e.g. Larson et al. 1981) or directly by measuring plasma orserum Et-IPA concentration with liquid chromatography (LC; e.g. Jones 1994). Thefact that a serum sample can be used to detect Et-IPA marking is an importantadvantage. Other persistent bait markers require invasive methods of detection; forexample tetracyclines are detected by analyzing teeth or bones (Crier 1970).

Ease of detection is one important characteristic of a practical bait marker, alongwith production of consistently reliable marking in the target species, easy incorpo-ration into baits, no effects on bait acceptance or feeding behaviour and low or niltoxicity for animals consuming it and for the environment (Cowan et al. 1984,Saunders et al. 1993). Reviews on other systemic markers such as rhodamine B areavailable (Fisher 1999), but to date, no reports on IPA derivatives have been pub-lished. We review Et-IPA and its analogues as bait markers in a variety of mammals,in field and captive studies; we analyze aspects of marking reliability and baitacceptance; we describe detection methods and pharmacokinetics of IPAs; and wehighlight the effects of the consumption of IPAs on animals’ health as well aspotential impacts on the environment.

METHODSWe conducted literature searches using the terms IPA, bait markers, oral baitingcampaigns and wildlife in the data bases Science direct, PubMed and Web of Knowl-edge in order to collect information concerning IPA utilization in a broad range ofmammals. Also, we contacted some expert colleagues working on this topic andasked them about their experiments with these compounds, i.e. number of animalstreated, doses administered, duration of the study, persistence of the compounds inthe animal organism and adverse effects detected in the individuals. These observa-tions were included in many unpublished reports. Finally, we included our own datain the review.

RESULTSEt-IPA as a bait marker for wild mammalsAbility of IPAs to mark the serum of mammals consuming themEt-IPA is strongly bound to serum albumin with very high affinity (Mudge et al.1971). It has been tested in many species to determine its long-term persistence inblood after ingestion and has consequently been deemed a suitable marker formammalian species such as coyote Canis latrans (Larson et al. 1981, Knowlton et al.1987), dog Canis familiaris (Baer et al. 1985), red fox Vulpes vulpes (Baer et al.1985, Trewhella et al. 1991, Saunders et al. 1993), arctic fox Alopex lagopus (Foll-mann et al. 1987), skunk Mephitis mephitis (Larson et al. 1981), raccoon Procyonlotor (Larson et al. 1981, Hadidian et al. 1989), cat Felis catus (Eason et al. 1994),ferret Mustela furo (Ogilvie & Eason 1998), goat Capra hircus (Eason & Batcheler1991, Eason & Frampton 1992), red deer Cervus elaphus scoticus (Sweetapple &Nugent 1998), white-tailed deer Odocoileus virginianus (White et al. 1995), wild

Iophenoxic acid as a bait marker for wild mammals 3


boar Sus scrofa (Cowled et al. 2008, Massei et al. 2009, Ballesteros et al. 2010) andrabbit Oryctolagus cuniculus (Hartley & Hamilton 1997, King et al. 1998). However,Et-IPA was not found to be a long-term marker in stoats Mustela erminea (Spurr2002), failed to elicit an increase in serum iodine level in black-tailed prairie dogsCynomys ludovicianus (Creekmore et al. 2002) and did not elevate total iodine inRichardson’s ground squirrels Spermophilus richardsoni or in any species of bird(Larson et al. 1981).

Although a persistent marker in some mammals, Et-IPA appears to have a relativelyshort persistence and therefore limited utility as a marker in marsupials such as thebrushtail possum Trichosurus vulpecula (Eason et al. 1994) and the swamp wallabyWallabia bicolor (Fisher & Marks 1997). The rapid clearance of Et-IPA from the plasmaof these species suggests that it is metabolized into a form that is readily available forexcretion by a pathway distinct from those in eutherian physiology (Fisher & Marks1997).

Persistence of Et-IPA in blood varies considerably between mammal species andalso appears to be dependent on the amount of Et-IPA ingested (Spurr 2002; Table 1).Baer et al. (1985) found that it persisted for more than 52 weeks in dogs receiving1mg Et-IPA kg-1, while in red foxes treated with 2.2mg Et-IPA kg-1 it persisted for lessthan 13 weeks. Similar variable persistence of Et-IPA was found in three species ofmammalian herbivore (red deer, white-tailed deer and goat; the latter had thelongest persistence; Sweetapple & Nugent 1998).

Field use of Et-IPA as a bait markerEt-IPA has been established as an effective, persistent bait marker in some mamma-lian species (Table 2) in doses ranging from 4.9mg Et-IPA per bait (Fleming 1997) to40mg Et-IPA per bait (Mitchell 1998, Cagnacci et al. 2006, 2007). An additionaladvantage of Et-IPA is that it appears to act as a quantitative marker in some species:ingestion of larger doses of Et-IPA produces correspondingly higher blood concen-trations with longer persistence (Saunders et al. 1993, King et al. 1998, Sweetapple &Nugent 1998, Cowled et al. 2008, Massei et al. 2009).

However, estimating the number of Et-IPA-treated baits ingested by a mammalmight be complicated by the partial consumption of baits, the size and the age of theindividual and the time elapsed between ingestion and detection (Saunders et al.1993). While some captive studies have demonstrated a quantitative markingresponse to Et-IPA (Saunders et al. 1993, Massei et al. 2009), due to the range ofvariables in field uptake of bait by wild mammals, only approximate estimates of thenumber of Et-IPA-marked baits consumed by individuals are possible (Saunders et al.1993, Mitchell 1998).

Et-IPA is soluble in organic solvents, such as oils, propylene glycol and ethanol, andcan be added directly to baits (Massei et al. 2009), injected as a solution into baits(e.g. Fleming 1997, Mitchell 1998, Fleming et al. 2000, Campbell et al. 2006, Balles-teros et al. 2010) or placed inside a gelatine capsule, plastic blister or wax ampoulecontained within bait (Fletcher et al. 1990, Linhart et al. 1994, Southey et al. 2001,Cowled et al. 2008). In contrast to other systemic markers such as rhodamine B (Fisher1999), Et-IPA has no reported aversive taste or adverse influence on bait acceptanceor palatability (Knowlton et al. 1987, Ogilvie & Eason 1998, Southey et al. 2001).Though it may not be relevant in studies of captive animals, the bioavailability ofEt-IPA delivered in bait requires consideration for field studies. Cowled et al. (2008)



Tab

le1.

Exam

ple

so

fca

pti

vetr

ials

con

du

ced

ind

om

esti

co

rw

ildm

amm

als

–m

eth

od

s,p

ersi

sten

ceo

fIP

As

afte

rin

ges

tio

nan

dad

vers

eef

fect

so

bse

rved

du

rin

gth

etr

ial

Spec

ies

Nu

mb

ero

fte

sted

anim

als

(+n

um

ber

of

con

tro

ls)

IPA

s’ad

min

istr

atio

n

Du

rati

on

of

the

stu

dy

or

tim

eo

fla

stsa

mp

ling

An

alyz

edti

ssu

ean

dm

eth

od

of

det

ecti

on

IPA

s’p

ersi

sten

ceaf

ter

ing

esti

on

Ad

vers

eef

fect

sR

efer

ence

Wild

bo

arSu

ssc

rofa

n=

8(+

1)G

avag

e;5

(n=

3)an

d15

(n=

5)m

go

fEt

-,M

t-an

dPr

-IPA

kg-1

540

day

sSe

rum

,LC

/ESI

-MS

Mt-

IPA

=9

mo

nth

sEt

-an

dPr

-IPA

>18

mo

nth

s

No

ne

rep

ort

ed(n

ot

test

edfo

r).

Five

IPA

-tre

ated

fem

ales

had

hea

lth

yp

igle

ts14

mo

nth

saf

ter

IPA

con

sum

pti

on

Bal

lest

ero

set

al.

2010

n=

12(+

2)40

mg

of

each

IPA

(Et-

,M

t-an

dPr

-IPA

)g

avag

e(n

=6)

and

bai

tin

g(n

=6)

190

day

sSe

rum

,LC

/ESI

-MS

Mt-

IPA

<3

mo

nth

sEt

-an

dPr

-IPA

>6

mo

nth

s

No

ne

rep

ort

ed(n

ot

test

edfo

r)S.

Blo

me

&C

.G

abri

el,

per

son

alco

mm

un

icat

ion

n=

12B

aiti

ng

;Et

-an

dPr

-IPA

-tre

ated

bai

tsat

5,10

and

20m

gkg

-1o

fb

od

yw

eig

ht

273

day

sSe

rum

,H

PLC

>273

day

sN

on

ere

po

rted

(no

tte

sted

for)

Mas

sei

etal

.20

09

Ferr

etM

ust

ela

pu

tori

ou

sfu

ron

=6

Gav

age;

1.5m

go

fEt

-IPA

kg-1

84d

ays

Plas

ma,

PBI

<28

day

sN

on

ere

po

rted

(no

tte

sted

for)

Og

ilvie

etal

.19

95n

=6

Gav

age;

5mg

of

Et-I

PAkg

-156

day

sPl

asm

a,PB

I<2

8d

ays

No

ne

rep

ort

ed(n

ot

test

edfo

r)O

gilv

ieet

al.

1996

n=

2G

avag

e;1

(n=

1)an

d10

(n=

1)o

fEt

-IPA

mg

kg-1

10d

ays

Plas

ma,

PBI

3d

ays

<<10

day

sN

on

ere

po

rted

(no

tte

sted

for)

Fish

eret

al.

2007

Sto

atM

ust

ela

erm

inea

n=

12Eg

gco

nta

inin

g1,

2,4

or

5mg

of

Et-I

PAp

ereg

g21

day

sPl

asm

a,PB

I14

<<21

day

sN

on

ere

po

rted

(no

tte

sted

for)

Spu

rr20

02

Wea

sel

Mu

stel

an

ival

isn

=2

(+1)

Egg

sco

nta

inin

g1

or

2mg

of

Et-I

PA(o

ral

exp

osu

res

of

9an

d15

mg

kg-1

Et-I

PA)

21d

ays

Plas

ma,

PBI

>21

day

sN

on

ere

po

rted

(no

tte

sted

for)

Spu

rr20

02

Red

dee

rC

ervu

sel

aph

us

n=

12(+

2)B

olu

so

ffo

liag

eco

nta

inin

g20

,20

0o

r40

0mg

of

Et-I

PAm

ixed

into

ap

etro

latu

mca

rrie

r(m

ean

do

ses

of

0.3,

2.6

and

5.4m

gkg

-1Et

-IPA

)

40d

ays

Plas

ma,

PBI

>40

day

sN

on

ere

po

rted

(no

tte

sted

for)

Swee

tap

ple

1995

Go

atC

apra

hir

cus

n=

3(+

3)G

avag

e;1.

5mg

of

Et-I

PAkg

-115

0d

ays

Plas

ma,

PBI

>5m

on

ths

No

ne

rep

ort

ed(n

ot

test

edfo

r)Ea

son

&Fr

amp

ton

1992

n=

51.

5mg

of

Et-I

PAkg

-1>3

mo

nth

s,q

uan

tita

tive

resp

on

se

No

ne

rep

ort

ed(n

ot

test

edfo

r)Ea

son

&B

atch

eler

1991



Tab

le1.

(Co

nti

nu

ed)

Spec

ies

Nu

mb

ero

fte

sted

anim

als

(+n

um

ber

of

con

tro

ls)

IPA

s’ad

min

istr

atio

n

Du

rati

on

of

the

stu

dy

or

tim

eo

fla

stsa

mp

ling

An

alyz

edti

ssu

ean

dm

eth

od

of

det

ecti

on

IPA

s’p

ersi

sten

ceaf

ter

ing

esti

on

Ad

vers

eef

fect

sR

efer

ence

Bru

shta

ilp

oss

um

Tric

ho

suru

svu

lpec

ula

n=

7G

avag

e;1.

5mg

of

Et-I

PAkg

-1(n

=3)

and

10m

go

fEt

-IPA

kg-1

(n=

4)14

day

sPl

asm

a,PB

I<5

–10

day

sat

bo

thd

ose

sN

on

ere

po

rted

(no

tte

sted

for)

Easo

net

al.

1994

Cat

Felis

catu

sn

=3

Ora

llyd

ose

d;

1.5m

go

fEt

-IPA

kg-1

335

day

sPl

asm

a,PB

IA

pp

roxi

mat

ely

20w

eeks

No

ne

rep

ort

ed(n

ot

test

edfo

r)Ea

son

etal

.19

94R

at–

lab

ora

tory

Rat

tus

no

rveg

icu

s

n=

12(+

4)G

avag

e;5m

go

fEt

-IPA

kg-1

21d

ays

Seru

m,

HPL

C>2

1d

ays

No

ne

rep

ort

ed(n

ot

test

edfo

r)Pu

rdey

etal

.20

03

Rab

bit

Ory

cto

lag

us

cun

icu

lus

n=

9O

rally

do

sed

;1.

5,5.

0an

d10

.0m

go

fEt

-IPA

kg-1

(n=

3fo

rea

chd

ose

)11

9d

ays

Plas

ma,

PBI

=13

,15

and

17w

eeks

for

each

do

se,

resp

ecti

vely

No

ne

rep

ort

ed(n

ot

test

edfo

r)K

ing

etal

.19

98

n=

12G

avag

e;0.

7,3.

6an

d7.

1mg

of

Et-I

PAkg

-142

day

sPl

asm

a,H

PLC

=42

day

s(t

wo

low

erd

ose

s)>4

2d

ays

for

the

hig

her

do

se

No

ne

rep

ort

ed(n

ot

test

edfo

r)H

artl

ey&

Ham

ilto

n19

97

Go

lden

ham

ster

Mes

ocr

icet

us

aura

tus

n=

17Pr

egn

ant

and

no

n-p

reg

nan

tfe

mal

ein

ject

edin

trap

erit

on

eally

wit

hra

dio

lab

elle

dEt

-IPA

(0.5

–80m

gkg

-1)

fro

md

ays

8–15

of

ges

tati

on

Euth

aniz

edfo

rsa

mp

ling

on

day

15o

fg

esta

tio

n

Var

iou

sB

y7

day

sfo

etal

pla

sma

equ

ilib

rate

dw

ith

mat

ern

alp

lasm

aco

nce

ntr

atio

ns

Plac

enta

ltr

ansf

erd

emo

nst

rate

d.

No

dem

on

stra

ble

tera

tog

enic

effe

cts

or

foet

alre

sorp

tio

n.

Mill

eret

al.

1972

Wal

lab

yW

alla

bia

bic

olo

rG

rou

ps

of

cap

tive

wal

lab

ies

Ora

llyd

ose

d;

0,15

and

30m

go

fEt

-IPA

kg-1

20d

ays

Plas

ma,

PBI

24h

ou

rs<<

4d

ays

No

ne

rep

ort

ed(n

ot

test

edfo

r)Fi

sher

&M

arks

1997

Et-I

PA,

eth

yl-i

op

hen

oxi

cac

id;

HPL

C,

hig

h-p

erfo

rman

celiq

uid

chro

mat

og

rap

hy;

IPA

,io

ph

eno

xic

acid

;LC

/ESI

-MS,

liqu

idch

rom

ato

gra

ph

yw

ith

elec

tro

spra

yio

niz

atio

n-m

ass

spec

tro

met

ry;

Mt-

IPA

,m

eth

yl-i

op

hen

oxi

cac

id;

PBI,

pla

sma

bo

un

dio

din

eco

nce

ntr

atio

n:

con

cen

trat

ion

so

fp

lasm

aio

din

eo

fd

ose

dan

imal

sco

mp

ared

wit

hth

eb

asel

ine

mea

sure

db

efo

reIP

As’

adm

inis

trat

ion

or

mea

sure

din

con

tro

lin

div

idu

als;

Pr-I

PA,

pro

pyl

-io

ph

eno

xic

acid

.



Tab

le2.

Use

of

IPA

sas

ab

ait

mar

ker

for

wild

mam

mal

sin

fiel

dtr

ials

Spec

ies

test

edQ

uan

tity

of

IPA

su

sed

(mg

per

bai

t)B

ait

com

po

siti

on

Mo

de

of

inco

rpo

rati

ng

IPA

inth

eb

aits

An

alyz

edti

ssu

ean

dm

eth

od

of

det

ecti

on

Ref

eren

ce

Wild

bo

ar,

fera

lsw

ine,

wild

swin

eo

rfe

ral

pig

sSu

ssc

rofa

40m

go

fM

t-IP

Ao

r40

mg

of

Et-I

PAB

aits

con

sist

of

pig

let

feed

,p

araf

fin

,su

cro

sean

dci

nn

amo

n-t

ruffl

ep

ow

der

attr

acta

nt

(Bal

lest

ero

set

al.

2009

)

Dis

solv

edin

eth

ano

lan

din

corp

ora

ted

wit

hin

each

bai

tm

atri

x

Seru

mfr

om

tho

raci

cb

loo

dfr

om

hu

nte

r-h

arve

sted

wild

bo

ar,

LC/E

SI-M

S

Bal

lest

ero

set

al.

2011

22.7

mg

of

Et-I

PAPI

GO

UT®

bai

tsIn

ject

edin

toea

chb

ait

Seru

m,

LC/E

SI-M

SC

amp

bel

let

al.

2006

20m

go

fEt

-IPA

Poly

mer

fish

mea

lb

aits

Dis

solv

edin

ho

tco

rno

ilan

din

corp

ora

ted

insi

de

ag

elat

ine

cap

sule

wit

hin

each

bai

t

Seru

m,

PBI

Flet

cher

etal

.19

90

20m

go

fEt

-IPA

Two

typ

es:

PIG

OU

T®an

dm

eat-

bas

edb

aits

Dis

solv

edin

a50

:50

mix

ture

of

eth

ano

lan

dp

rop

ylen

eg

lyco

lan

din

ject

edin

toea

chb

ait

Wh

ole

blo

od

,PB

IC

ow

led

etal

.20

08

24m

go

fEt

-IPA

Kan

gar

oo

mea

tb

aits

Dis

solv

edin

eth

ano

lan

din

ject

edin

toea

chb

ait

Seru

m,

PBI

Flem

ing

etal

.20

0040

mg

of

Et-I

PAC

attl

em

eat

bai

tsD

isso

lved

inet

han

ol

and

inje

cted

into

each

bai

tPl

asm

a,PB

IM

itch

ell

1998

Bad

ger

Mel

esm

eles

40m

go

fEt

-IPA

or

40m

go

fPr

-IPA

Thre

ety

pes

:m

eat,

fru

itan

dce

real

-bas

edb

aits

Ad

ded

to1M

NaO

H.

The

resu

ltin

gsa

ltw

asm

ixed

into

the

bai

tSe

rum

,H

PLC

Cag

nac

ciet

al.

2006

,20

0710

mg

of

Et-I

PAM

ixtu

reo

fp

lan

tan

dan

imal

pro

tein

san

dfi

sho

ilag

gre

gat

edb

ya

syn

thet

icp

oly

mer

Dis

solv

edin

corn

oil

and

inco

rpo

rate

dw

ith

lact

ose

into

gel

atin

eca

psu

les

Plas

ma,

PBI

Sou

they

etal

.20

01

Red

fox

Vu

lpes

vulp

es4.

9mg

of

Et-I

PAFo

xoff

®b

aits

Dis

solv

edin

eth

ano

lan

din

corp

ora

ted

wit

hin

each

bai

tm

atri

x

Seru

m,

PBI

Flem

ing

1997

5mg

of

Et-I

PAFo

xoff

®b

aits

Dis

solv

edin

eth

ano

lan

dp

ipet

ted

into

the

mid

dle

of

each

bai

tsPl

asm

a,PB

IM

arks

&B

loo

mfi

eld

1999

Rac

coo

nPr

ocy

on

loto

r10

mg

of

Et-I

PAC

orn

-bas

edb

aits

encl

ose

din

pla

stic

bag

sD

isso

lved

in1.

5ml

of

pro

pyl

ene

gly

col

and

pla

ced

ina

par

affi

nw

axam

po

ule

,w

hic

hw

asin

sert

edin

sid

eea

chb

ait

Seru

m,

PBI

Lin

har

tet

al.

1994

Fera

lg

oat

Cap

rah

ircu

s5m

go

fEt

-IPA

Cer

eal-

bas

edb

aits

flav

ou

red

wit

hm

ola

sses

Mix

edw

ith

each

bai

tm

atri

xPl

asm

a,PB

IFo

rsyt

h&

Park

es19

95

Et-I

PA,

eth

yl-i

op

hen

oxi

cac

id;

HPL

C,

hig

h-p

erfo

rman

celiq

uid

chro

mat

og

rap

hy;

IPA

,io

ph

eno

xic

acid

;LC

/ESI

-MS,

liqu

idch

rom

ato

gra

ph

yw

ith

elec

tro

spra

yio

niz

atio

n-m

ass

spec

tro

met

ry;

Mt-

IPA

,m

eth

yl-i

op

hen

oxi

cac

id;

PBI,

pla

sma

bo

un

dio

din

eco

nce

ntr

atio

n:

con

cen

trat

ion

so

fp

lasm

aio

din

eo

fd

ose

dan

imal

sco

mp

ared

wit

hth

eb

asel

ine

mea

sure

db

efo

reIP

As’

adm

inis

trat

ion

or

mea

sure

din

con

tro

lin

div

idu

als;

Pr-I

PA,

pro

pyl

-io

ph

eno

xic

acid

.



found that gavage-delivered Et-IPA resulted in higher iodine plasma concentrationsin wild boar than bait-delivered Et-IPA, perhaps because absorption of the marker islower when it is delivered inside baits. This problem can be overcome if the formu-lation to be used in field trials is tested in captivity with the same species andadjusted if necessary.

The detection of Et-IPA is moderately invasive depending on the species beingconsidered. Typically, restraint and anaesthesia of live-caught mammals are requiredto collect blood samples. Very little serum is required from each subject: 0.1–0.4ml(Jones 1994, Purdey et al. 2003, Wiles & Campbell 2006, Ballesteros et al. 2010). Thecost of capturing and restraining individuals of the target species should be added tothe costs associated with Et-IPA analysis and the cost of the marker itself (in 2012,around 32 Euros for 1g of Et-IPA; Sigma Aldrich, St. Quentin Fallavier, France). Ifmammals are being harvested as game (e.g. wild boar in Spain; Ballesteros et al.2011) or if carcasses are being collected for pest control (stoats in New Zealand;Purdey et al. 2003), samples may be collected by hunters or others, thus making theuse of Et-IPA more cost-effective and possible on a large scale.

Et-IPA analoguesMultiple markers are required to provide information on temporal or spatial pat-terns of bait consumption (Massei et al. 2009). Et-IPA has some analogues, such asmethyl-IPA (Mt-IPA) and propyl-IPA (Pr-IPA), which are produced by altering the sidechain and which may also be useful bait markers (Fig. 1). Their prices are similar tothose of Et-IPA (in 2012, around 22 and 30 Euros for 1g of Mt-IPA and Pr-IPA,respectively). Pr-IPA has been tested in the red fox (Jones et al. 1997), the Eurasianbadger Meles meles (Cagnacci et al. 2006, de Leeuw et al. 2006) and in wild boar(Massei et al. 2009, Ballesteros et al. 2010); Mt-IPA has been tested only in foxes(Jones et al. 1997) and wild boar (Ballesteros et al. 2010, 2011).

Pr-IPA has been found to have a similar persistence and elimination half-life toEt-IPA when tested in the same species and at the same dose (Jones et al. 1997,Cagnacci et al. 2006, Massei et al. 2009, Ballesteros et al. 2010). However, Mt-IPA haslower persistence (Jones et al. 1997, Ballesteros et al. 2010). This confirms that bothEt-IPA and Pr-IPA can be used as long-term markers (persistence: 7–8 weeks in foxes),whereas Mt-IPA can be used as a medium-term marker (persistence: 3 weeks in foxes;Jones et al. 1997). However, the shorter persistence of Mt-IPA may be beneficial insituations in which long-term monitoring is not required or if very persistent markingcould confound future marker trials with the same individuals. For example afterdistribution of Mt-IPA-marked baits in the field, treated mammals could be moni-tored for a few months, and then they could be used for subsequent studies or fornew marked-bait delivery trials.

Analytical methods for detection of IPAsIn the studies we reviewed, IPA concentrations were either indirectly or directlymeasured in blood serum or plasma by using various methods (Tables 1 and 2). Someauthors (e.g. Larson et al. 1981, Baer et al. 1985, Fletcher et al. 1990, Ogilvie & Eason1998, Knowlton & Olmstead 2001, Creekmore et al. 2002, Cowled et al. 2008) mea-sured the elevation of iodine concentration in blood, serum or plasma of differentspecies by spectrophotometry. The disadvantage of this method is that determina-tion of normal background iodine level in the wild population is needed prior to



the distribution of marked baits. Jones (1994) analyzed Et-IPA concentration in bloodsera of foxes directly by high-performance LC, followed by ultraviolet detection.The extraction procedure consisted of adding sulphuric acid, sodium tungstatedihydrated and methanol to serum in order to precipitate the proteins. Then thesolution was centrifuged and the supernatant was recollected for analysis. Purdeyet al. (2003) developed another extraction process with only precipitation of serumin methanol, centrifugation and direct injection of supernatant. This extractionmethod is much cheaper and may be carried out in the field (centrifuging ofprecipitated proteins can be done at a later stage) with a recovery of 100%, com-pared with the rate of up to 85% achieved by Jones (1994). Jones’s (1994) methodwas later adapted for use on badgers and wild boar by Cagnacci et al. (2006) andMassei et al. (2009), respectively, by identifying the IPA derivative ingested and

Fig. 1. Molecular structure of ethyl-iophenoxic acid (IPA) (a) and its analogues methyl-IPA (b) andpropyl-IPA (c).



quantifying more precisely the serum levels of each marker (Jones 1994, Jones et al.1997). Ballesteros et al. (2010) adapted Wiles and Campbell’s (2006) method fordetecting IPAs in blood serum, in which LC was coupled to electrospray ionization-mass spectrometry (ESI-MS) in the negative ion mode. The modification of theextraction method allows the concentration of the final extract, so that the injectionvolume is reduced to 50ml. This improves the limits of detection and quantification inwild boar serum (Ballesteros et al. 2010).

Fate of IPAs after absorptionMetabolism, distribution and excretion of IPAsThe metabolic fate of Et-IPA was first studied by Perlman et al. (1955). Its metabo-lism, distribution and excretion in the dog were described by Wade et al. (1971) andMudge et al. (1971). The three major metabolites are diglucuronide and the acyland ethereal monoglucuronides. These metabolites are themselves relatively lipidsoluble, though far less so than the parent compound. However, it is unlikely thattheir lipid solubility per se is the major determinant of the unique persistence ofEt-IPA; the rate of conjugate formation appears to be a more important factor (Wadeet al. 1971).

Et-IPA appears to be widely distributed in tissues and is firmly bound to plasmaproteins (e.g. >99% in the golden hamster Mesocricetus auratus; Miller et al. 1972).Berndt et al. (1971a, b) compared the accumulation process of Et-IPA between liver,kidney and plasma. By the end of the 1970s, several researchers concluded that theexceptionally high affinity of Et-IPA for a single site of human serum albumin (site 1)appears to underlie its unusual persistence in plasma (Mudge et al. 1978, Mudge1980). Later, the crystal structure of the human serum albumin-IPA complex revealeda total of four binding sites on the protein, only two of which are likely to bephysiologically relevant, the higher-affinity being confirmed in the drug site 1 of theprotein (Ryan et al. 2011).

The parent molecule itself appears not to be excreted in more than trace amounts(Miller et al. 1972). After administration in dogs, initial excretion of conjugates inbile and urine is prompt but is followed by very low rates when plasma levels decline(Mudge et al. 1971). Equal amounts of Et-IPA are lost from the body via the faecaland urinary routes after the administration of a larger dose. However, at low plasmalevels (chronic studies or those with lower dosage), the main loss from the body isalmost exclusively via the urine (Mudge et al. 1971). Under this circumstance, to thelow excretory rate must be added the effect of both the intestine and the renaltubule re-absorption. Mudge et al. (1971) demonstrated that all these mechanismscontribute to the exceptional persistence of the compound in the human body.However, the rate of clearance of Et-IPA from plasma varies considerably betweenspecies (Spurr 2002). This suggests that Et-IPA can be metabolized into forms readilyavailable for excretion by different pathways, depending on the relative ability ofdifferent species to metabolize it (Fisher & Marks 1997).

Transfer of IPAs across the placentaAfter Et-IPA was used as a contrast medium for cholecystography in humans duringthe 1950s (Shapiro 1953), it was demonstrated that Et-IPA could cross the placen-tal barrier to the foetal blood and could be detected in the offspring’s serumseveral years after ingestion by the mother either prior to or during pregnancy



(Shapiro & Man 1960, David et al. 1961, Shapiro 1961, Hung 1966, Jankowski et al.1967, Carakushansky et al. 1969). Shapiro (1961) described transplacental passage ofEt-IPA in 63 children born from 51 mothers who had been treated with Et-IPApreviously. Later, high long-term persistence was reported in both children andEt-IPA-treated mothers. For example a persistence of 6.7 years was found in theserum of a child whose mother had received the chemical about 21 months beforethe child’s birth (Carakushansky et al. 1969). Jankowski et al. (1967) reported a casethat demonstrated the transplacental transfer of Et-IPA even after 8 years. However,the longest period in which Et-IPA was present in a mother and a child was reportedby Hung (1966), since there was an interval of at least 10 years between the time oflast administration of Et-IPA to the mother and the evaluation of the child. Thelong-term persistence of this compound in humans is due to its low rate of excretion(Jankowski et al. 1967) and to the high quantities administered to human patients(e.g. 3–4.5g; Hoffmann 1954).

Et-IPA passage into foetal blood has also been reported in golden hamsters(Miller et al. 1972), badgers (de Leeuw et al. 2006) and wild boar (Ballesteros et al.2010). Miller et al. (1972) injected pregnant hamsters with radiolabelled Et-IPAfrom days 8–15 of gestation, and they were euthanized for sampling on day 15 ofgestation. By 7 days after administration, foetal plasma concentrations were equili-brated with maternal plasma concentrations. At low doses, foetus/maternal plasmaratios reached 0.52, and only the yolk sac had a higher concentration than mater-nal plasma. Ballesteros et al. (2010) found Et-IPA and Pr-IPA in 4-month-old wildboar piglets born 420 days after their mothers ingested doses of 5–15mg kg-1 ofboth compounds. The maximum concentrations of Et-IPA and Pr-IPA found were 15and 22 times lower, respectively, than those observed in 4-month-old wild boarpiglets that consumed these IPAs directly at 2 months of age (Ballesteros et al.2010).

Safety of IPAs as bait markersEffects observed in mammals consuming IPAsThe risk of toxicity or adverse effects of IPAs in animals consuming marked baits andthe potential risk of secondary transfer to predators or humans are importantconsiderations in the practical field application of IPAs as bait markers (Cowan et al.1984).

Et-IPA has been shown to produce no adverse effects when 3–4.5g of the com-pound is administered orally for x-ray visualization of the gall bladder in humans(Hoffmann 1954) and has no known side effects in laboratory mammals (it has beenstudied in mice Mus musculus, rats Rattus norvegicus, guinea pigs Cavia porcellus anddogs; Margolin et al. 1953). No signs of pathological changes in organs of mammalstreated with Et-IPA have been found. An acute median lethal dose LD50 of1850mg kg-1 was obtained when Et-IPA was delivered to mice orally.

Several researchers reported hyperthyroidism in patients that presented highlevels of bound iodine in serum after Et-IPA administration for gall bladder visual-ization (e.g. Astwood 1957). Although the relationship between hyperthyroidismand Et-IPA exposure is not established, the long residency of Et-IPA is thought likelyto affect tests of thyroid activity (Ralston et al. 1964).

Studies on transplacental transfer demonstrated that Et-IPA may accumulate in thefoetus without any known deleterious effects to mother or foetus (Shapiro & Man



1960, Carakushansky et al. 1969, Miller et al. 1972, de Leeuw et al. 2006). Moreover,in experiments on captive mammals, many species were given different IPA doses(Table 1). Monitoring of the subjects was possible for variable times of up to 4 yearsafter exposure, and no adverse effects on health, food intake or reproduction havebeen reported in IPA-treated mammals (Table 1).

Risk assessment for non-target speciesAfter absorption, Et-IPA is excreted to the environment via urine and faeces in verysmall quantities (Mudge et al. 1971). The risk of contamination of the environmentis probably low, but there have been no direct studies of the environmental fate ofEt-IPA or its metabolites. Ballesteros et al. (2010) observed that a wild boar that didnot receive IPAs showed low concentrations of the compounds after living in thesame enclosure as wild boar that was given IPA by syringe. This confirms that IPAsthat are excreted in faeces or urine can be transferred to non-consuming animals.However, in this case, the captive animals shared the same enclosure for a longperiod of time, a situation that is unlikely to occur in the field.

Knowlton and Olmstead (2001) showed that Et-IPA can be transferred to a mam-malian carnivore consuming any blood-bearing tissues of Et-IPA-exposed prey. So,the possibility of secondary IPA marking, through transfer to carnivores or humansconsuming the meat of IPA-marked mammals such as wild boar, should be evaluated.In order to assess this risk of transfer, a worst case scenario was developed for wildboar as follows. The bait acceptance studies of Ballesteros et al. (2009) using artificialfeeders in the field showed that baits were accepted by 2- to 3-month-old animals.So we can assume that 2-month-old piglets (body mass between 12 and 15kg) are theyoungest wild boar that may consume baits and that may be shot by hunters. If suchpiglets consume between 1 and 10 baits each containing 40mg of IPA (Mitchell 1998,Ballesteros et al. 2011), they may ingest between 40 and 400mg of IPAs, i.e. 2.7–33.3mg kg-1 of body mass. Mudge et al. (1971) showed rapid bilary elimination justafter exposure, at high plasma levels, and then a more gradual elimination with astabilization phase. They demonstrated that Et-IPA is distributed widely in tissues, sowe may suppose that the calculation presented above is a worst case scenario. Joneset al. (1997) found no adverse effects in foxes fed 160mg of Et-IPA, and the acute oralmean lethal dose in other species is much higher (LD50 for mice: 1850mg kg-1).Nevertheless, humans (as well as other predators) could eat meat of IPA-markedgame several times a year over several years, so chronic exposure of humans andpredators should be evaluated. Depending on which test is used for thyroid function(e.g. if the amount of iodine taken up by the thyroid gland is measured), falsepositive hyperthyroidism tests may occur in people who ingested meat from IPA-treated mammals.

CONCLUSIONEt-IPA and its analogues have been shown to be suitable bait markers for a numberof mammalian species (e.g. Baer et al. 1985, Cowled et al. 2008, Massei et al. 2009,Ballesteros et al. 2010). However, variation in the persistence of IPAs in differentspecies and in the effect of the dose ingested highlights the need for calibrationtesting of each compound as a marker for each species and for each proposed usebefore starting a bait delivery trial (Spurr 2002).



The use of IPA derivatives as bait markers has numerous advantages, including thefollowing: (i) their long-term persistence in the target organism, which makes themsuitable for long-term field trials; (ii) their detectability in only a small sample ofserum; (iii) the use of different IPA analogues allows different modalities of baitdistribution experiments in the same place or bait campaigns at different timepoints; and (iv) their lack of reported adverse effects on exposed captive, domesticand wild mammals.

A relatively small, single oral uptake of IPAs is required to mark most mammals. So,low doses of IPAs may be placed inside baits to monitor bait uptake by wildmammals. Furthermore, doses of IPAs delivered inside baits in field trials could bereduced, as the limit of detection obtained by LC/ESI-MS can be improved by aceto-nitrile evaporation and sample re-dissolution in a suitable organic solvent (Balles-teros et al. 2010). It is highly unlikely that in a field situation any individual mammalwould consume sufficient baits to approach toxic or potentially harmful levels ofIPAs. Implications for the accidental exposure of humans and carnivores were inves-tigated by extrapolation of IPA residues found in the meat of wild boar. It appearshighly unlikely that, by secondary exposure, they could ingest sufficient IPAs toproduce any adverse effect of acute toxicity, although the risk of chronic exposureshould be addressed in future research.

Transfer from mother to foetus in mammals is not a concern, as it has beenproven that the quantities of IPAs detectable in the offspring are minimal incomparison to those observed in those mammals consuming IPA-marked baits(Ballesteros et al. 2010). However, the possibility of vertical contamination fromIPA-consuming mothers to non-consuming offspring should be taken into accountto identify vaccinated or drug-treated mammals in baiting campaigns correctly. Itwould be desirable to establish a limit following a conservative criterion, belowwhich the animal is not deemed to have consumed a whole bait (Ballesteros et al.2010).

Et-IPA and its analogues are more expensive per se than other commonly usedmarkers such as rhodamine B and tetracyclines; moreover, IPA analysis requiresexpensive equipment such as LC/ESI-MS apparatus. However, IPAs can be detectedfrom a small sample of animal serum, and the possibility of using IPA analoguesallows different modalities of bait distribution trials (Ballesteros et al. 2010).

In summary, the ability of Et-IPA and its analogues to mark serum of consumingwild mammals for long periods of time, together with recent and ongoing improve-ments in their detection, makes them a good choice for oral baiting field experi-ments or vaccination campaigns. However, future experiments should be conductedin order to assess the long-term effects of these compounds on organisms, as well astheir bioaccumulation after chronic exposure of wild mammals to them.

ACKNOWLEDGEMENTSWe received support from the French Ministry of Agriculture. The research leading tothese results was also funded by the European Community’s Seventh FrameworkProgramme (FP7/2007–2013) under grant agreement no. 227003 CP-FP (projectCSFV_goDIVA) and no. 212414 (TB-STEP), the Grupo Santander and the FundaciónMarcelino Botín (Spain). This is a contribution to Ministerio de Economía y Competi-tividad Plan National Research grant AGL2011-30041 (Spain) and ERDF: EuropeanRegional Development Fund.



REFERENCESAstwood EB (1957) Occurrence in the sera of certain patients of large amounts of a newly isolated

iodine compound. Transactions of the Association of American Physicians Philadelphia 7: 183–191.Baer GM, Shaddock JH, Hayes DJ, Savarie P (1985) Iophenoxic acid as a serum marker in carnivores.

Journal of Wildlife Management 49: 49–51.Ballesteros C, Gortazar C, Canales M, Vicente J, Lasagna A, Gamarra JA, Carrasco-García R, de la

Fuente J (2009) Evaluation of baits for oral vaccination of European wild boar piglets. Research inVeterinary Science 86: 388–393.

Ballesteros C, Camarero PR, Cristòfol C, Vicente J, Gortázar C, de la Fuente J, Mateo R (2010) Analysisby LC/ESI-MS of iophenoxic acid derivatives and evaluation as markers of oral baits to deliverpharmaceuticals to wildlife. Journal of Chromatography B 878: 1997–2002.

Ballesteros C, Vicente J, Carrasco-García R, Mateo R, de la Fuente J, Gortazar C (2011) Specificity andsuccess of oral-bait delivery to Eurasian wild boar in Mediterranean woodland habitats. EuropeanJournal of Wildlife Research 57: 749–757.

Berndt WO, Mudge GH, Wade DN (1971a) Hepatic slice accumulation of iopanoic and iophenoxicacids. The Journal of Pharmacology and Experimental Therapeutics 179: 85–90.

Berndt WO, Wade DN, Mudge GH (1971b) Renal cortical slice accumulation of iophenoxic acid andiopanoic acid. The Journal of Pharmacology and Experimental Therapeutics 179: 74–84.

Cagnacci F, Massei G, Coats J, de Leeuw A, Cowan DP (2006) Long-lasting systemic bait markers forEurasian badgers. Journal of Wildlife Diseases 42: 892–896.

Cagnacci F, Massei G, Cowan DP, Walker N, Delahay RJ (2007) Effects of bait type and deploymentstrategy on uptake by free-living badgers. Wildlife Research 34: 454–460.

Campbell TA, Lapidge SJ, Long DB (2006) Using baits to deliver pharmaceuticals to feral swine inSouthern Texas. Wildlife Society Bulletin 34: 1184–1189.

Carakushansky G, Cardenas LE, Gardner LI (1969) Transplacental passage and persistence in serum for6.7 years of iophenoxic acid (Teridax) in a child. Pediatrics 44: 1020–1021.

Cowan DP, Vaughan JA, Prout KJ, Christer WG (1984) Markers for measuring bait consumption by theEuropean wild rabbit. Journal of Wildlife Management 48: 1403–1409.

Cowled BD, Lapidge SJ, Smith MI, Staples LD (2008) Vaccination of feral pigs (Sus scrofa) usingiophenoxic acid as a simulated vaccine. Australian Veterinary Journal 86: 50–55.

Creekmore TE, Rocke TE, Hurley J (2002) A baiting system for delivery of an oral plague vaccine toblack-tailed prairie dogs. Journal of Wildlife Diseases 38: 32–39.

Crier JK (1970) Tetracyclines as a fluorescent marker in bones and teeth of rodents. Journal ofWildlife Management 34: 829–834.

David R, Alexander D, Wilkins L (1961) Placental transfer of an organic radiopaque medium resultingin a prolonged elevation of the protein-bound iodine. The Journal of Pediatrics 59: 223–226.

Eason CT, Batcheler D (1991) Iophenoxic and iopanoic acid as bait markers for feral goats. WildlifeResearch 18: 85–90.

Eason CT, Frampton CM (1992) The plasma pharmacokinetics of iophenoxic and iopanoic acids ingoats. Xenobiotica 22: 185–189.

Eason CT, Batcheler D, Frampton CM (1994) Comparative pharmacokinetics of iophenoxic acid in catsand brushtail possums. Wildlife Research 21: 377–380.

Fisher P (1999) Review of using rhodamine B as a marker for wildlife studies. Wildlife Society Bulletin27: 318–329.

Fisher P, Airey A, Warburton B, Morgan D (2007) Animal Health Board Project No. R-10679. A PassiveToxin Applicator for Ferret Control. Landcare Research contract report LC0607/194 (unpublished),20. Prepared for the Animal Health Board, Wellington, New Zealand.

Fisher PM, Marks CA (1997) Evaluation of iophenoxic acid as a biomarker for swamp wallabies(Wallabia bicolor). Wildlife Research 24: 97–103.

Fleming PJS (1997) Uptake of baits by red foxes (Vulpes vulpes): implications for rabies contingencyplanning in Australia. Wildlife Research 24: 335–346.

Fleming PJS, Choquenot D, Mason RJ (2000) Aerial baiting of feral pigs (Sus scrofa) for exotic diseasecontrol in semi-arid rangelands of New South Wales. Wildlife Research 27: 531–537.

Fletcher WO, Creekmore TE, Smith MS, Nettles VF (1990) A field trial to determine the feasibility ofdelivering oral vaccines to wild swine. Journal of Wildlife Diseases 26: 502–510.

Follmann EH, Savarie PJ, Ritter DG, Baer GM (1987) Plasma marking of arctic foxes with iophenoxicacid. Journal of Wildlife Diseases 23: 709–712.

Forsyth DM, Parkes JP (1995) Suitability of aerially sown artificial baits as a technique for poisoningferal goats. New Zealand Journal of Ecology 19: 73–76.



Fry TL, Dunbar MR (2007) A review of biomarkers used for wildlife damage and disease management.In: Nolte DL, Arjo WM, Stalman DH (eds) Proceedings of the 12th Wildlife Damage ManagementConference, 216–222. University of Nebraska, Lincoln, Nebraska, USA.

Hadidian J, Jenkins SR, Johnston DH, Savarie PJ, Nettles VF, Manski D, Baer GM (1989) Acceptance ofsimulated oral rabies vaccine baits by urban raccoons. Journal of Wildlife Diseases 25: 1–9.

Hall RR, VanderLaan WP (1961) Effects of iophenoxic acid on tests of thyroid function. Journal of theAmerican Medical Association 177: 648–649.

Hartley FG, Hamilton TL (1997) Iophenoxic acid as a quantitative bait marker for rabbits (Oryctolaguscuniculus). Gibier Faune Sauvage, Game Wildlife 14: 395–403.

Hoffmann RC (1954) Teridax, a new cholecystgraphic medium. The American Journal of DigestiveDiseases 21: 150–152.

Hung W (1966) Elevation of protein-bound iodine in an 8 year old due to transplacental passage ofan organic iodine dye. Pediatrics 37: 677–680.

Jankowski JJ, Feingold M, Gellis SS (1967) Effect of maternal ingestion of iophenoxic acid (Teridax) onprotein-bound iodine: report of a family. The Journal of Pediatrics 70: 436–438.

Jones A (1994) High-performance liquid chromatographic determination of iophenoxic acid inserum. Journal of Chromatography B 654: 293–296.

Jones A, Woods J, Cheeseman C, Nadian A, Page R (1997) Two new iodinated compounds as serummarkers in foxes. Journal of Wildlife Management 61: 241–245.

King DR, Robinson MH, Eason CT, Batcheler D (1998) Iophenoxic acid as a biomarker for rabbits(Oryctolagus cuniculus). Wildlife Research 25: 65–68.

Knowlton FF, Olmstead SR (2001) Using iophenoxic acid injections of prey to identify mammals thatfeed on them. Wildlife Society Bulletin 29: 495–500.

Knowlton FF, Savarie PJ, Wahlgren CE, Hayes DJ (1987) Retention of physiological marks by coyotesingesting baits containing iophenoxic acid, mirex, and rhodamine B. In: Shumake S, Bullard RW(eds) Vertebrate Pest Control and Management Materials, vol. 5. 141–147. American Society forTesting and Materials, Philadelphia, USA.

Larson GE, Savarie PJ, Okuno I (1981) Iophenoxic acid and mirex for marking wild, bait-consuminganimals. Journal of Wildlife Management 45: 1073–1077.

de Leeuw AN, Smith GC, Woods JA (2006) Use of iophenoxic acid to assess bait uptake by Europeanbadgers. In: Feare CJ, Cowan DP (eds) Advances in Vertebrate Pest Management, vol. 4. 243–254.Filander, Furth, Germany.

Linhart SB, Blom FS, Engeman RM, Hill HL, Hon T, Hall DI, Shaddock JH (1994) A field evaluation ofbaits for delivering oral rabies vaccines to raccoons (Procyon lotor). Journal of Wildlife Diseases30: 185–194.

Margolin S, Stephens IR, Spoerlein MT, Makovsky A, Belloff GB (1953) Experimental oral cholecys-tography with a new contrast medium, teridax (triiodoethionic acid). Journal of the AmericanPharmaceutical Association 42: 476–481.

Marks CA, Bloomfield TE (1999) Bait uptake by foxes (Vulpes vulpes) in urban Melbourne: thepotential of oral vaccination for rabies control. Wildlife Research 26: 777–787.

Massei G, Jones A, Platt T, Cowan DP (2009) Iophenoxic acid as a long-term marker for wild boar.Journal of Wildlife Management 73: 458–461.

Miller RK, Ferm VH, Mudge GH (1972) Placental transfer and tissue distribution of iophenoxic acid inthe hamster. American Journal of Obstetrics and Gynecology 114: 259–266.

Mitchell J (1998) The effectiveness of aerial baiting for control of feral pigs (Sus scrofa) in NorthQueensland. Wildlife Research 25: 297–303.

Mudge GH (1980) Cholecystographic agents and drug binding to plasma albumin. InvestigativeRadiology 15: 102–108.

Mudge GH, Strewler GJ Jr, Desbiens N, Berndt WO, Wade DN (1971) Excretion and distributionof iophenoxic acid. The Journal of Pharmacology and Experimental Therapeutics 178: 159–172.

Mudge GH, Desbiens N, Stibitz GR (1978) Binding of iophenoxate and iopanoate to human serumalbumin. Drug Metabolism and Disposition 6: 432–439.

Ogilvie SC, Eason CT (1998) Evaluation of iophenoxic acid and rhodamine B for marking feral ferrets(Mustela furo). New Zealand Journal of Zoology 25: 105–108.

Ogilvie SC, Spurr EB, Morgan DR (1995) A bait, bait marker, toxin and baiting strategy for the controlof ferrets. Landcare Research Contract Report LC9495/114 (unpublished), 19. Prepared for theAnimal Health Board, Wellington, New Zealand.

Ogilvie SC, Spurr EB, Eason CT, Young N (1996) Development of a poison baiting strategy for ferrets.Royal Society of New Zealand Miscellaneous Series 36: 78–84.



Perlman PL, Kosinski RE, Sutter D (1955) Studies on the absorption and excretion of a new chole-cystographic agent, Teridax. Journal of the American Pharmaceutical Association 44: 69–74.

Purdey DC, Petcu M, King CM (2003) A simplified protocol for detecting two systemic bait markers(rhodamine B and iophenoxic acid) in small mammals. New Zealand Journal of Zoology 30:175–184.

Ralston DE, Schattenberg TT, Owen CA, McConahey WM (1964) Protein-bound-iodine in serum andtyroidal uptake of I131. Postgraduate Medicine 36: 141–148.

Ryan AJ, Chung CW, Curry S (2011) Crystallographic analysis reveals the structural basis of thehigh-affinity binding of iophenoxic acid to human serum albumin. BMC Structural Biology 11: 18.

Saunders G, Harris S, Eason CT (1993) Iophenoxic acid as a quantitative bait marker for foxes. WildlifeResearch 20: 297–302.

Savarie PJ, Johns BE, Gaddis SE (1992) A review of chemical and particle marking agents used forstudying vertebrate pests. In: Borrecco JE, Marsh RE (eds) Proceedings of the 15th Vertebrate PestConference, 252–257. University of California, Davis, California, USA.

Shapiro R (1953) A preliminary report on Teridax, a new cholecystographic medium. Radiology 60:687–690.

Shapiro R (1961) The effect of maternal ingestion of iophenoxic acid on the serum protein-boundiodine of the progeny. The New England Journal of Medicine 264: 378–381.

Shapiro R, Man EB (1960) Iodophenoxic acid and serum-bound iodine values. Journal of the AmericanMedical Association 173: 1352.

Southey AK, Sleeman DP, Prendergast J, O’Sullivan RF, Mulcahy MF (2001) Use of biomarkers to assessthe feasibility of delivering a vaccine to badgers (Meles meles). Journal of Zoology 253: 133–139.

Spurr EB (2002) Iophenoxic acid as a systemic blood marker for assessment of bait acceptance bystoats (Mustela erminea) and weasels (Mustela nivalis). New Zealand Journal of Zoology 29:135–142.

Sweetapple P (1995) Effectiveness of foliage bait for poisoning deer: development of a plasmamarker for deer and a toxic field trial. Landcare Research Contract Report LC9596/55 (unpub-lished). Prepared for the Animal Health Board, Wellington, New Zealand.

Sweetapple PJ, Nugent G (1998) Iophenoxic acid as a serum marker for red deer (Cervus elaphusscoticus). Wildlife Research 25: 649–654.

Trewhella WJ, Harris S, Smith GC, Nadian AK (1991) A field trial evaluating bait uptake by an urbanfox (Vulpes vulpes) population. Journal of Applied Ecology 28: 454–466.

Wade DN, Desbiens N, Strewler GJ Jr, Berndt WO, Mudge GH (1971) Metabolism of iophenoxic acidin the dog. The Journal of Pharmacology and Experimental Therapeutics 178: 173–179.

White LM, Huetter DP, Linhart SB, Savarie PJ, van Brackle MD (1995) Iophenoxic acid as an oralbiomarker in white-tailed deer. Wildlife Society Bulletin 23: 194–197.

Wiles MC, Campbell TA (2006) High-performance liquid chromatographic determination of iophe-noxic acid in serum. Journal of Chromatography B 832: 144–157.

Submitted 24 October 2011; returned for revision 3 January 2012; revision accepted 19 January 2012Editor: KH



iophenoxic acid as a bait marker for wild mammals: efficacy and safety considerations

Documents