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J. Appl. Ent. 127, 481–488 (2003)Ó 2003 Blackwell Verlag, BerlinISSN 0931-2048
Effects of ivermectin and doramectin faecal residueson the invertebrate colonization of cattle dung
V. H. Suarez1, A. L. Lifschitz2, J. M. Sallovitz2 and C. E. Lanusse2
1Estacio´n Experimental Agropecuaria Anguil, INTA, Anguil, La Pampa, Argentina; 2Laboratorio deFarmacologı´a, Dpto. Fisiopatologı´a, Facultad de Ciencias Veterinarias, UNCPBA, Campus Universitario,Tandil, Argentina
Ms. received: May 10, 2002; accepted: January 14, 2003
Abstract: The eﬀects of avermectin [ivermectin (IVM) and doramectin (DRM)] faecal residues on dung colonizationand degradation by invertebrates were evaluated during late spring in the east of La Pampa province, Argentina. Thestudy was conducted after collection of faecal material from animals (10 steers per group) allocated to the followinggroups: untreated control group (CG) and groups treated subcutaneously (200 lg/kg) with either DRM (DG) or along-acting formulation of IVM (IG). Fifty pats (550 g each) per group were collected, prepared and deposited on theﬁeld on days 3, 7, 16 and 29 post-treatment (pt). Eight pats per group were recovered after 7, 14, 21, 42, 100 and180 days post-deposition (pd) on the ﬁeld. The weight, percentage of dry matter, number of arthropods and nematodesfrom faeces were determined. The faecal concentrations of IVM and DRM were measured by high performance liquidchromatography (HPLC) throughout the trial period to correlate the pattern of drug degradation in dung with pd time.
The total number of arthropods in dungs from CG was higher (P < 0.05) than those counted between days 3 and 29 ptin IG and DG. A decrease in the number of Coleoptera larvae (P < 0.05) between days 21 and 42 days pd wasobserved in both treated groups. Diptera larvae counts in CG pats were signiﬁcantly higher (P < 0.05) than thoseobtained in treated groups in the 7- and 14-day-old pats. A lower number (P < 0.05) of Collembola, compared withpats from CG, was recovered from IG and DG pats deposited at days 3 and 7 pt and exposed from day 42. The countsof Acari in pats from treated animals were lower (P < 0.05) than those observed in CG pats at 3, 8 and 16 days pt.
There were no diﬀerences neither in adult Scarabaeidae recovered nor in the proportions of dung buried and destroyedby great dung beetles. Dung speciﬁc nematodes were reduced (P < 0.05) in IG and DG pats from 3 and 7 days ptcompared with those of CG pats. The comparative results shown here demonstrate that the negative eﬀects of bothIVM and DRM on dung colonization are similar. The pattern of drug degradation in the environment was very slow.
High residual concentrations of both active parent compounds were recovered in dungs exposed in the ﬁeld for up to180 days pd. Concentrations as high as 13 ng/g (IVM) and 101 ng/g (DRM) were measured in faeces obtained frompats deposited on day 27 pt and exposed to the environment during 180 days. The results show a decrease ininvertebrate colonization of dung recovered from IVM- and DRM-treated cattle, which is in agreement with the largedrug residual concentrations measured in faeces.
Key words: cattle-Nematoda, doramectin, dung-fauna, environmental toxicity, faecal residues, ivermectin
treated animal and excreted in large concentrations asunchanged parent drugs in faeces (Lifschitz et al.,
The endectocide drugs are 16-membered macrocyclic
2000). There are diﬀerences on the pharmacokinetic
lactones with a broad-spectrum antiparasitic activity
behaviour, pattern of faecal excretion and eﬃcacy of
against a wide range of nematodes and arthropods.
endectocide compounds in cattle according to the type
The macrocyclic lactones available on the market for
of formulation and route of administration used (Herd,
use in cattle include the avermectins [ivermectin (IVM),
abamectin, doramectin (DRM) and eprinomectin), and
Cattle productive assessments in the Pampeana
milbemycins (moxidectin). These compounds cause
region of Argentina have demonstrated that parasitic
paralysis or several sublethal metabolic disorders and
losses can be important in bovine grazing systems
eventually death of invertebrates that ingest or tran-
(Suarez et al., 1991, 1999) and that parasite control is
scuticulally absorb them (Campbell and Benz, 1984).
very proﬁtable. In this area, as in many other regions
Endectocides are potent parasiticide molecules with
of the southern hemisphere, a great proportion of
high eﬃcacy patterns at extremely low dosages. They
current parasite control programmes are based on the
are extensively distributed to diﬀerent tissues in the
U. S. Copyright Clearance Center Code Statement:
use of endectocides, taking advantage of their persist-
ence eﬀect on a broad range of target parasites.
At deposition day, weight, dry matter and parasitological
Early studies have reported high eﬀect on target-
measurements from fresh faeces were determined. Ten
pest insect in the dung pats, such as Haematobia
grams wet weight of the samples from each group was
irritans (Miller et al., 1981). These led to further
collected for estimating faecal moisture by drying samples
investigations into the adverse eﬀects of these drugs
for 48 h at 100°C and expressed as percentage of dry
upon non-target fauna of the dung (Wall and Strong,
weight. Nematode eggs were counted according to the
1987). Currently, there is some information from
method of Roberts and O’Sullivan (1949) and speciﬁc
Europe, Australia and North America (Madsen et al.,
infective larvae (L3) diﬀerentiated after culture of faecal
Herd, 1995; Wardhaugh and Beckmann, 1996) on
the non-speciﬁc eﬀects of IVM, which can kill or
Eight pats per group were recovered and examined after 7,
14, 21, 42, 100 and 180 days on the ﬁeld. Collected pats were
disrupt the development of a wide variety of insect-
transferred to polyethylene bags and taken to the laboratory.
colonizing dung pats. This decomposing dung fauna
Each pat sample was weighed and the dry weight was
help to maintain the ecosystem by returning nutrients
determined. The dung fauna was enumerated and identiﬁed.
to the soil; thus, the long-term consequences of
Arthropods were recovered using the Berlese method (Ber-
endectocide utilization remain unknown (Strong,
lese, 1904), while a 5-g dung subsample was processed
through Baermann modiﬁed method (Suarez, 1997) to isolate
Current knowledge of the environmental impact of
endectocide-based control strategies in countries with avery intensive use, such as in Argentina, is scarce.
2.4 Measurement of faecal drug residue concentrations
Some preliminary information has shown the adverseeﬀect of IVM on the level of invertebrate colonization
Faecal samples (10 g) of IVM- and DRM-treated animals
and faecal dispersion in dung pats during autumn
were collected, kept in labelled vials and stored at )20°C
until analysed by high-performance liquid chromatography
Suarez, 2001). However, no information is available
on the ecotoxic eﬀects of these types of drugs during
(HPLC). The extraction of IVM and DRM from faecalsamples was carried out following the technique described by
other seasonal periods and in other ecological regions.
et al. (2000), using abamectin (ABM) as internal
Additionally, scarce information of ecotoxic eﬀects of
standard. The solid phase extraction was carried out using an
DRM is available worldwide (Dadour et al., 2000).
Aspec XL autosampler (Gilson, Villiers Le Bell, France). The
This ﬁeld study was conducted to evaluate the
derivatization to convert IVM and DRM in ﬂuorescent
comparative eﬀects of IVM and DRM faecal residues
molecules was done as described by De Montigny et al.
on cattle dung-colonizing fauna and on dung mass
(1990). IVM and DRM faecal concentrations were deter-
mined by HPLC with ﬂuorescence detection using a Shim-adzu 10 A HPLC system (Shimadzu Corporation, Kyoto,Japan) following the technique described by Lifschitz et al.
(1999, 2000). The IVM or DRM/ABM peak area ratios were
used to estimate the IVM and DRM concentrations in spiked(validation of the analytical method) and experimental faecal
samples. The solvents (Baker, Phillipsburg, NJ) used duringthe extraction process and drug analysis were of HPLC
The experiment was carried out at the Agricultural Research
Station (EEA) of Anguil in the Western Pampeana region of
A complete validation of the analytical procedures used for
Argentina. On 9 November 1998, 30 steers aged 18 months
extraction and quantiﬁcation of IVM and DRM was
and weighing 378 ± 18 kg were randomly allocated to three
performed before starting the analysis of experimental
groups of donor animals. These animals were representative
samples. Calibration curves were prepared in a range
of the grazing fattening system of the region and were
between 0.5 and 100 ng/g using least squares linear regres-
naturally infected with prevalent gastrointestinal nematodes
sion analysis. Correlation coeﬃcients (r) were >0.99. Drug
(Suarez, 1990). Steers received a injectable treatment with
recovery from faeces at diﬀerent concentrations was 72.3%
either a generic long-acting IVM (IG) formulation (Feno-
(IVM) and 73.6% (DRM). The intra-assay precision
max; Hoechst Roussel Vet., Av. Int. Tomkinson 2054 (1642),
expressed as coeﬃcient of variation was 3.31% (IVM) and
San Isidro, Province of Buenos Aires, Argentina) or DRM
(Dectomax; Pﬁzer S.A.C.I., Virrey Loreto 2477 (1426),Buenos Aires, Argentina) (DG), both given at 200 lg/kg.
Group CG was the untreated control.
Daily rainfall, evaporation, relative humidity and daily
2.2 Faecal collection and pat preparation
temperatures were recorded from the Department of Mete-orology of INTA, Anguil, near the experimental site.
At days 3 (12 November), 7 (16 November), 16 (25November) and 29 (8 December) after treatment, faecesvoided in the previous 18–22 h were collected separately from
each cattle group for deposition on the ﬁeld, using separate
Data on the counts of arthropods and nematodes recovered
equipment. The dung from each group was then mixed
per 100 g of dry dung matter, weight and dry matter
thoroughly and weighed into 550 g wet weight aliquots
percentages from replicated pats were analysed by analysis
fashioned into 50 experimental pats of 15 cm diameter. These
of variance with treatment and duration of ﬁeld exposure as
50 artiﬁcially formed pat replicates per group were placed in
alternating 2 m sequence in three rows on bare-scraped soil
SAS, 1988). The arthropod data were rank trans-
Iman and Canover, 1979) for analysis.
Eﬀects of avermectins on dung colonization
The annual rainfall in this region ranged between 700and 800 mm and the highest incidence was fromOctober (spring) to April (autumn). However, at thebeginning of the study rainfall decreased by 30%below the 45-year mean and late spring and earlysummer period experienced severe drought.
The great variety of species collected were divided intolarge arthropods, mainly Coleoptera and Dipteralarvae, and microarthropods such as Collembola and
Fig. 1. Total cumulative number of Coleoptera larvae
Acari. The total number of arthropods recovered from
from day 3, 7, 16 and 29 post-treatment, recovered in
IG and DG pats was signiﬁcantly (P < 0.05) lower
100 g of dry weight of pats exposed after 7, 14, 21, 42,
than in control pats. Diﬀerences were recorded in all
100, 180 days on the ﬁeld. Dung pats were obtained from
pat data depositions from the 3rd to the 29th day post-
treatment (table 1). There was a signiﬁcant (P < 0.01)
doramectin (DG) or untreated controls (CG)
interaction between treatment groups and time in theﬁeld.
number of larvae after 7 and 14 days of exposure in the
ﬁeld. Only larvae of the Sarcophagidae, Muscidae andSphaeroceridae families were observed. Control pats
The majority of families of Coleoptera present in the
contained the highest counts (P < 0.05) in the 7- and
pats were Scarabaeidae and Aphodiidae. The largest
14-day-old pats from the 3rd and 7th post-treatment
dung beetles found were Sulcophanaeus menelas,
faecal extraction. Total mean Diptera counts for all
Onthophagus hirculus and Canthidium breve, but the
post-treatment depositions is presented in ﬁg. 2.
most frequent family recovered by the Berlese methodwere mainly Aphodiidae and other families speciessuch as Histeridae and Staphylinidae. No signiﬁcant
diﬀerences were observed between the adult Scara-
Collembola specimens numbers showed signiﬁcant
baeidae, Aphodiidae, Histeridae and Staphylinidae
(P < 0.05) diﬀerences between treated and non-
treated groups at days 3 and 7 post-treatment.
The number of Coleoptera larvae (mainly Aphodii-
Numbers of Collembola from faeces from injected
dae) collected per 100 g of pat dry weight is shown in
animals were smaller after 42–180 days in the ﬁeld
ﬁg. 1. In general, larval counts in the dung pats from
compared with controls. Mean total Collembola
treated animal groups were signiﬁcantly (P < 0.05)
numbers recovered from 100 g of dry faeces from
lower than those from the control group. However,
day 3 and 7 post-treatment were 2.0, 2.3 and 3.7 for
while the control dung showed the highest diﬀerencesin larval numbers between groups at 21 and 42 days,no statistical diﬀerences were seen up to 14 days in the
Diptera larvae occurred in low numbers and were
distributed very irregularly. Pats contained the highest
Table 1. Mean total arthropod number recovered in
100 g of dry weight of pats deposited 3, 7, 16 and
29 days after treatment. Dung pats were from cattlegroups injected withivermectin (IG), doramectin (DG)
Fig. 2. Mean number of Diptera larvae recovered in
100 g of dry weight of pats deposited 3, 7, 16, and
29 days after treatment. Dung pats were obtained from
Column mean values with different scripts are signiﬁcantly dif-
doramectin (DG) or untreated controls (CG)
The appearance between treated and control group
pats was not diﬀerent throughout this study. There
were very low numbers of pats destroyed by the great
dung beetles (Sulcophanaeus and Onthophagus) and
there were no diﬀerences between treatments in the
proportions of dung buried. Most of them rest
78.9 ± 20.05% of mean dry weight during the whole
trial. There were no signiﬁcant diﬀerences in wet and
dry weight (moisture content) of pats among the threegroups at any time.
Fig. 3. Total cumulative number of Acari from day 3, 7,
Statistical analysis comparing dung fauna numbers
16 and 29 post-treatment, recovered in 100 g of dry
showed that the eﬀects of the IVM and DRM were not
weight of pats exposed after 7, 14, 21, 42, 100, 180 days
signiﬁcantly diﬀerent. All ﬁgures and tables of arthro-
on the ﬁeld. Dung pats were obtained from cattle groups
pods recovered showed similar numbers of inverte-
treated witheither ivermectin (IG), doramectin (DG)
brates collected from pats from both drug-treated
IG, DG and CG, respectively. There was a signiﬁcantinteraction between treatment and exposition in the
Large concentrations of IVM and DRM were meas-
ﬁeld. Collembola counts from pats during the ﬁrst
ured in all the dung pat samples evaluated from
42 days in the ﬁeld were negligible in all groups.
treated groups. Faecal IVM concentrations were
Numbers of Acari recovered from the control group
1150 ng/g (at day 3 post-treatment) and 22.8 ng/g (at
pats were signiﬁcantly (P < 0.05) higher than those of
day 29 post-treatment). DRM faecal concentrations
treated groups from day 14 in the ﬁeld and from
obtained at the same days post-treatment varied
depositions collected from day 3, 7 and 16 post-
between 1122 and 135 ng/g, respectively. Long per-
sistence of both molecules was observed in the patsexposed in the ﬁeld during diﬀerent periods. TheIVM and DRM concentration levels measured in dung
pats obtained at diﬀerent days post-treatment and
The infective larval genera of gastrointestinal nema-
after the diﬀerent post-deposition periods are sum-
todes recovered from the control cattle pats were
marized in tables 2 and 3. The long persistence of the
Ostertagia, Haemonchus, Cooperia, Trichostrongylus
active parent compounds in the environment was
and Oesophagostomum. No infective nematode larvae
corroborated by the large faecal concentrations meas-
were detected in pats of treated groups.
ured in dung pats up to 180 days after their deposition
About dung-speciﬁc nematodes recovered, only in
3 and 7 days after treatment, total counts occurred insigniﬁcant (P < 0.05) reduced numbers in pats fromtreated cattle compared with controls. The mean
number of dung-speciﬁc nematodes recovered from5 g of dung dry matter during the study was 87.2, 68.9
Residues of both IVM and DRM induced a marked
and 123.0, respectively, for IG, DG and CG. This drug
adverse eﬀect on diﬀerent dung-colonizing inverte-
adverse eﬀect was noted in treated cattle pats until
brates. These results are in agreement with previously
reported data suggesting the toxicity of IVM faecal
concentrations (ng/g dryweight) in cattle dung pats
pt, post-treatment; pd, post-deposition; ND, not determined.
Eﬀects of avermectins on dung colonization
posed in the ﬁeld for diﬀerentperiods (from 7 to 180 days)
pt, post-treatment; pd, post-deposition; ND, not determined.
residues on non-target dung arthropods (Strong, 1993;
abamectin were toxic to dung beetles larvae for
Herd, 1995; Wardhaugh and Beckmann, 1996). How-
2–4 weeks post-treatment (Wardhaugh and Mahon,
ever, there were no diﬀerences on adult Coleoptera
1991; Ridsdill-Smith, 1993). In Brazil, Iglesias (1998)
counts in any pats regardless of the treatment, and it
reported a minor number of Coleoptera larvae after
seems that there was no repellent eﬀect in pats
30 days of deposition in faeces of IVM-treated ani-
collected from IVM-treated animals. In addition, these
results seem to show non-lethal toxic eﬀect on adult
Dipteran larvae, present in low numbers in this
dung colonizing Coleoptera. However, the methodo-
trial, aerate dung, making them attractive to other
logy used in this work was unable to measure precisely
invertebrates. According to previous results (Suarez,
the probable residue toxicity to the reproductive
2001) ﬂy larvae were reduced in treated cattle faeces,
performance of colonizing Coleoptera. A recent work
but the low number of ﬂy larvae limited statistical
(Wardhaugh et al., 2001) documented IVM- and epri-
analysis. In the subtropical region of Brazil, where the
nomectin-induced reproductive deﬁciencies in dung
trials were carried out in July during the drought
beetles. Other studies (Wardhaugh and Rodriguez
season, very high numbers of ﬂy larvae were collec-
´ndez, 1988; Ridsdill-Smith, 1993) have also shown
ted. In this scenario, signiﬁcant reduced number of
that some species of newly emerged adult beetles are
Diptera larvae in IVM-treated cattle faeces from 3 to
aﬀected by IVM faecal residues, but with few days
28 days post-treatment after 10, 30 and 60 days in the
older they can survive. About the impact of DRM
ﬁeld were reported (Iglesias, 1998). Another trial
residues, Dadour et al. (2000) indicated that this drug
showed that in faeces from IVM-treated cattle, the
aﬀects the mortality and reproductive potential on
development of Musca domestica was not observed
newly emerged adults of Onthophagus binodis between
(or neglegible), for H. irritans it was prevented for up
to 35 days post-treatment, while Stomoxys calcitrans
Although this study was not designed to obtain
development was less aﬀected (Miller et al., 1981). In
quantitative data on the largest dung-burying beetles
addition, no target ﬂies were aﬀected by avermectin
such as Sulcophanaeus and Onthophagus, these beetle
faecal residues for 10 and 30–35 days post-treatment
species were those recovered at the largest counts.
These beetles destroy and bury the dung pats during
(Madsen et al., 1990; Wardhaugh and Mahon, 1998).
the ﬁrst days after deposition. Pitfall traps must be
Biological assays indicated that avermectin residues
necessary to quantify their presence and other meth-
varied according to the formulation and route of
odology to study their nesting and larval stages.
administration of the drug, and oral formulation
Contrary to previous autumn observations (Suarez,
(0.2 mg/kg) for sheep or horses adversely aﬀected ﬂy
2001) where numbers of adult Staphylinidae of treated
larvae only for 3–4 days after administration (Herd,
groups were lower up to 16 days post-treatment, in this
trial with diﬀerent climatic conditions, there were
Microarthropods were also aﬀected by IVM and
similar numbers of this predator insect family. Simi-
DRM treatments. In Collembola, numbers were only
larly, Strong et al. (1996), under England weather
reduced in treated groups during 7 days after treat-
conditions, obtained no Staphylinidae diﬀerences
ment, while in a previous autumn trial, numbers were
negatively aﬀected for 28 days after treatment (Suarez,
The Coleoptera larvae (mainly Aphodiidae) were
2001). These diﬀerences may be due to the reduced
present in the DRM and IVM pats in lower numbers
density observed in the present study or other inter-
than in control pats from 21 or 42 days in the ﬁeld.
acting factors related to a drought period in late
These data evidenced that drug residues could be
implicated in adverse eﬀect on Coleoptera immature
Data of Acari collected in the current assay are in
stages at least during 29 days after treatment under our
agreement with those obtained from the autumn trial
regional conditions. Previous studies in Europe (Som-
(Suarez, 2001), where mites of treated groups were
et al., 1993; Strong et al., 1996) conﬁrm these
signiﬁcantly fewer than those of control group during
ﬁndings, showing that IVM aﬀects reproductive per-
3, 8 and 16 days post-treatment. There are few reports
formance of adults, feeding activity and development
about microarthropods. In agreement with the present
of larvae. Injectable formulations of both IVM and
results, Iglesias (1998), in Brazil, reported that mites of
several suborders (Gamasida, Oribatida and Acaridi-
with a more rapid rate of excretion, and as a
da) were reduced in the dung from IVM-treated cattle
consequence, is likely to be less harmful to the
during 3, 14 and 28 days after treatment. Endectocide
environment. Drug formulation, dosage and admin-
concentrations in faeces directly account for the
istration route are important factors in determining
deleterious eﬀect on Acari. However, the presence of
drug proﬁle elimination and persistence of dung
drug residues in nematodes and Diptera eggs eaten by
residues (Herd et al., 1996). Comparative studies
some Acari species, may also contribute to reduction in
indicate that moxidectin has no detectable eﬀects on
Acari. The food source of some Acari and Collembola
non-target arthropods and hence it is environmentally
are based in bacteria and saprophytic fungi (Moore
safer than IVM (Fincher and Wang, 1993; Strong and
and DeRuiter, 1993). The consequences of the endect-
Wall, 1994). Comparisons between pour-on formu-
ocide residues on these invertebrates and their inter-
lations of eprinomectin and moxidectin showed that
actions with the dung food web need to be elucidated.
cattle faeces voided after treatment with eprinomectin
Suarez (1990) reported infective larvae of gastroin-
were associated with high Onthophagus juvenile mor-
testinal nematode genera recovered from the control
tality during the ﬁrst 1–2 weeks post-treatment, while
cattle pats. There were very few studies on dung-
moxidectin had no detectable eﬀects (Wardhaugh
speciﬁc nematodes, many of which are fungivorous
and help reduce fungal populations. Data from this
Large IVM and DRM faecal concentrations were
trial conﬁrm the initial autumn observation of Suarez
measured in dung pats throughout the experimental
(2001) where dung pats from treated cattle had low
period. The concentrations of DRM in faeces were
nematode numbers. However, in that report the
higher than those measured for IVM, which is highly
persistence of adverse eﬀect was prolonged until
consistent with the previously reported patterns of
2 weeks after injection, while in the present trial the
tissue distribution and excretion proﬁle for these
eﬀect was noted only in the ﬁrst week post-treatment.
molecules in cattle (Lifschitz et al., 2000). A pro-
In Germany, Barth et al. (1993) pointed out that only
longed persistence of both active parent compounds
some dung-speciﬁc nematodes species occurred in
(IVM and DRM) permitted their detection in faeces
reduced numbers in pats of the IVM bolus-treated
from pats exposed for up to 180 days in the ﬁeld
(tables 2 and 3). Remaining drug concentrations in
The similar rate of pat degradation for the groups
dung deposited after 27 days post-treatment and
reported in this trial diﬀer from previous data obtained
exposed to environmental conditions for 180 days
during early autumn. Autumn results (Suarez, 2001)
represented between 56% (IVM) and 75% (DRM) of
showed signiﬁcant delays in the rate of degradation of
the concentrations measured immediately after their
those pats from cattle injected with IVM and DRM,
deposition. Hence, this scarce eﬀect of ﬁeld exposure
utilizing reduced pat weight as indicator. Dung fauna
on IVM and DRM faecal concentrations determined
diversity recovered in late autumn trial was not
that enough drug to adversely aﬀecting dung-colon-
diﬀerent from those of the actual trial, but was more
izing fauna was present throughout the entire trial
abundant and the number of pats dispersed was also
period. These concentrations were far above those
higher. These contradictory results agree with other
determined as lethal (Sommer et al., 1992) or suble-
controversial results obtained under diﬀerent experi-
thal (Strong, 1992; Dadour et al., 2000) for dung
fauna. Altogether, these results indicate that expo-
(Strong, 1992) and Denmark (Madsen et al., 1990)
sure to ﬁeld conditions will not prevent the deleteri-
showed signiﬁcant delays in dung disappearance in
ous eﬀects of faecal residual concentrations of
pats from IVM-treated cattle, while others obtained no
endectocide molecules on dung fauna. These eﬀects
delay diﬀerences (McKeand et al., 1988; Wratten et al.,
will be exerted for a long time until dung pats are no
1993). These diﬀerences may have been inﬂuenced by
more suitable for feeding and colonization of beetles.
several factors, such as the methodologies used for pat
A more pronounced eﬀect can be expected when
dispersal measurements, dung fauna regional species,
administering IVM as an intraruminal long-acting
the inﬂuences of climate and season fauna variation
bolus. The administration of an intraruminal IVM
(Herd, 1995). Seasonal peaks of insect activity are
bolus showed a long-lasting deleterious eﬀect as high
likely to produce greater degradation eﬀects (Strong,
concentrations (38 ng/g) are achieved in faeces for up
1993). In the present study, drought conditions seem to
be the cause of reduced arthropod number and pat
The results reported here for this geographical
In accordance with a similar previous ﬁeld trial
region demonstrate that cattle faecal residues of both
during autumn (Suarez, 2001), there were similar
IVM and DRM adversely aﬀect the invertebrate
eﬀects between the two injectable avermectins under
colonization of dung in late spring. Both drugs appear
late spring ﬁeld conditions of the La Pampa region.
to equally aﬀect dung fauna, which is consistent with
Likewise, Wardhaugh and Mahon (1998) observed
their large faecal concentration proﬁles measured up to
that, in faeces from abamectin-injected cattle, survival
180 days after pat exposure in the ﬁeld. These results
of Musca vetustissima larvae was not signiﬁcantly
also emphasize the need for further testing studies to
diﬀerent from that recorded after an equivalent IVM-
evaluate the environmental impact of endectocide
injected treatment, while the oral IVM formulation
compounds under a variety of conditions, and partic-
was less harmful because of its reduced persistence.
ularly on long-term evaluations under real production
It would appear that drug aqueous oral formulation
Eﬀects of avermectins on dung colonization
Moore, J. C.; DeRuiter, P. C., 1993: Assessment of distur-
bance on soil ecosystems. Vet. Parasitol. 48, 75–85.
The authors are grateful to Carina Bonetti, Olga Urmente and
T. N., 1997: Ecological implications of control
strategies: arthropods of domestic and production ani-
management of the assays. We also wish to thank Professors
mals. Int. J. Parasitol. 27, 155–165.
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2012 UPDATED CHAPTER C: PRESENTING PROBABILITIES SECTION 1: AUTHORS/AFFILIATIONS Lyndal Trevena Vrije Universiteit (Free University) Medical Center Children’s Hospital of Eastern Ontario Max Planck Institute for Human Development Dartmouth Institute for Health Policy and Clinical The University of Texas MD Anderson Cancer Center Max Planck Institute for Human Development Su