Endectocide residues affect insect attraction to dung from treated cattle: implications for toxicity tests

A 3-year study was performed in southern Alberta, Canada to assess the effect of endectocide residues on the attractiveness of cattle dung to colonizing insects. In 2003 and 2004, insect captures were compared between pitfall traps baited with dung of untreated cattle and paired traps baited with dung of cattle that had been treated 7 days previously with topically applied doramectin, eprinomectin, ivermectin or moxidectin. Faecal residues associated with each compound affected insect captures in both spring and autumn of each year. Effects were detected (P < 0.05) for a total of 94 cases representing 27 insect taxa from 13 families in three orders (Coleoptera, Diptera, Hymenoptera). Two-fold differences in captures were common. Up to six-fold differences were observed. Eleven cases of attraction and 11 cases of repellency were associated with residues of doramectin. Eprinomectin tended to repel insects, with decreased captures for 19 of 29 cases of effect. Ivermectin showed a strong attractive effect, with increased captures for 17 of 25 cases. Moxidectin also showed a strong attractive effect, with increased captures for 17 of 18 cases. Comparisons between compounds suggested that results for doramectin best predicted results for eprinomectin and vice versa. In 2005, insect captures were compared between pitfall traps baited with dung of untreated cattle and traps baited with dung from cattle treated 3, 7 or 14 days previously with topically applied doramectin. Effects were detected in 14 cases plus one case of near significance (P= 0.053). Significant differences between control vs. days 3, 7 and/or 14 dung were detected in nine cases. Residues enhanced captures in seven of these cases. Day 14 dung affected captures in six of these cases. This study shows that endectocide residues can affect the number of insects attracted to colonize and oviposit in dung. Hence, the emergence of their offspring from field-colonized dung of untreated vs. endectocide-treated cattle should not be used as a measure of residue toxicity per se, but rather as a measure of 'insect activity'. Insect activity is a composite measure of residue toxicity, the number and species composition of insect colonists, and the mortality factors (e.g. predation, parasitism, competition) associated with the co-occurrence of these species in the dung pat.     

Fly larvicidal activity in the faeces of cattle and pigs treated with endectocide products

Bioassays were conducted to study the effect of a single therapeutic dose of injectable ivermectin, doramectin or moxidectin given to cattle and pigs and excreted in their faeces, against larvae of the housefly, Musca domestica L. (Diptera: Muscidae). Five cattle were treated with each of the test products. Cattle faecal samples were collected before treatment and on days 1, 2, 3, 6, 10, 16, 20, 23 and 28 after treatment. Three groups of pigs, each comprising 12-14 pregnant sows and gilts, were used in the experiment. Pig faeces was collected from each group before treatment and on days 1, 3, 5, 7, 9, 11, 13, 15 and 20 after treatment. Thirty, first-stage larvae were placed into 100 g of faeces. Five replicates were examined for each time-point and for each endectocide group. Evaluation was based on the number of larvae surviving to adult emergence. Low numbers of adults emerged from samples taken from cattle 1 day after treatment, indicating that ivermectin and doramectin were rapidly excreted in the faeces and affected the development of the house fly. A larvicidal effect of both drugs in cattle faeces was present for a period of about 3-4 weeks and lasted a few days longer in cattle treated with doramectin than with ivermectin. In cattle, the larvicidal activity of moxidectin was first observed in faecal samples collected 2 days post-treatment; however, it killed fewer larvae than the other two drugs. The larvicidal effect of moxidectin subsequently decreased. Ivermectin and doramectin exhibited a pronounced larvicidal effect against the house fly in the faeces of pigs. The effect of doramectin was of longer duration. Moxidectin gave the weakest larvicidal effect in pig faeces. The main difference between the results obtained for the two livestock species is that peak toxicity occurred relatively later and for a shorter duration in pig than in cattle faeces.     

Effects of ivermectin and doramectin faecal residues on the invertebrate colonization of cattle dung

Abstract: The effects of avermectin [ivermectin (IVM) and doramectin (DRM)] faecal residues on dung colonization and degradation by invertebrates were evaluated during late spring in the east of La Pampa province, Argentina. The study was conducted after collection of faecal material from animals (10 steers per group) allocated to the following groups: untreated control group (CG) and groups treated subcutaneously (200 μg/kg) with either DRM (DG) or a long‐acting formulation of IVM (IG). Fifty pats (550 g each) per group were collected, prepared and deposited on the field on days 3, 7, 16 and 29 post‐treatment (pt). Eight pats per group were recovered after 7, 14, 21, 42, 100 and 180 days post‐deposition (pd) on the field. The weight, percentage of dry matter, number of arthropods and nematodes from faeces were determined. The faecal concentrations of IVM and DRM were measured by high performance liquid chromatography (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 pt in IG and DG. A decrease in the number of Coleoptera larvae (P < 0.05) between days 21 and 42 days pd was observed in both treated groups. Diptera larvae counts in CG pats were significantly higher (P < 0.05) than those obtained in treated groups in the 7‐ and 14‐day‐old pats. A lower number (P < 0.05) of Collembola, compared with pats from CG, was recovered from IG and DG pats deposited at days 3 and 7 pt and exposed from day 42. The counts of 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 destroyed by great dung beetles. Dung specific nematodes were reduced (P < 0.05) in IG and DG pats from 3 and 7 days pt compared with those of CG pats. The comparative results shown here demonstrate that the negative effects of both IVM 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 to 180 days pd. Concentrations as high as 13 ng/g (IVM) and 101 ng/g (DRM) were measured in faeces obtained from pats deposited on day 27 pt and exposed to the environment during 180 days. The results show a decrease in invertebrate colonization of dung recovered from IVM‐ and DRM‐treated cattle, which is in agreement with the large drug residual concentrations measured in faeces.     

Abundance of stable flies on heifers treated for control of horn flies with organophosphate impregnated ear tags

Ear tags containing 40% organophosphate insecticides (diazinon or diazinon plus chlorpyrifos-ethyl) were applied to control Haematobia irritans (L.) (Diptera: Muscidae) in treated (TG01 and TG02) and untreated (UG01 and UG02) groups of Holstein heifers born in 2001 and 2002, respectively. Control and treated groups were assessed for the abundance of Stomoxys calcitrans (L.) (Diptera: Muscidae) from August 2001 to April 2002 and again from August 2002 to April 2003. The treatment had a high efficacy for control of horn flies (maximum median number per heifer of TG01 and TG02 = 5) but a low effect on the abundance of stable flies. The total numbers of S. calcitrans were 1251 (42.9% of the total) and 1668 (57.1%) for TG01 and UG01, and 1423 (48.8%) and 1494 (51.2%) in TG02 and UG02, respectively. No significant difference in stable fly burden was found in 55 of the 76 weeks evaluated. A unimodal peak of abundance in the spring was found during the first fly season, and a bimodal abundance, with peaks in the spring and autumn, during the second season. No strong associations between horn fly and stable fly burdens was found in individuals of the CG01 (correlation coefficient = 0.13, P > 0.05) or CG02 (correlation coefficient = 0.538, P < 0.05, determination coefficient = 0.289).     

The role of volatile semiochemicals in mediating host location and selection by nuisance and disease-transmitting cattle flies

The role of volatile semiochemicals in mediating the location and selection within herds of Holstein-Friesian heifers by nuisance and disease-transmitting cattle flies was investigated using coupled gas chromatography-electrophysiology (GC-EAG), coupled gas chromatography-mass spectrometry (GC-MS), electrophysiology (EAG), laboratory behaviour and field studies. Using volatile extracts collected by air entrainment from heifers in the Netherlands, a number of active peaks were located by coupled GC-EAG for Musca autumnalis (de Geer) (Diptera: Muscidae) and Haematobia irritans (L.) (Diptera: Muscidae). Volatile samples were also collected from two heifers in Denmark shown in previous counting experiments to differ significantly in their fly loads. Coupled GC-EAG using Ha. irritans antennae revealed differences in the EAG response to the samples, with additional EAG activity in the sample collected from the heifer with the lower fly load. To identify more EAG active compounds, volatiles were also collected from 48-h-old urine by air entrainment. In total, 23 compounds were located and identified by coupled GC-EAG and GC-MS. Further electrophysiological testing of these compounds with five fly species [M. autumnalis, Ha. irritans, Hydrotaea irritans (L.) (Diptera: Muscidae), Stomoxys calcitrans (L.) (Diptera: Musicidae) and Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae)] showed that only some of the compounds were physiologically active across the range of flies tested. These included 1-octen-3-ol, 6-methyl-5-hepten-2-one, (Z)-3-hexen-1-ol, naphthalene, and all EAG active compounds identified from urine. Compounds showing significant EAG activity were tested for behavioural activity using a wind-tunnel designed for measuring upwind flight behaviour. At certain concentrations, 1-octen-3-ol, 6-methyl-5-hepten-2-one and 3-octanol increased upwind flight, whereas naphthalene, propyl butanoate and linalool reduced upwind flight. In field studies using small herds of heifers ranked according to their fly load, individual slow-release formulations of 1-octen-3-ol and 6-methyl-5-hepten-2-one, when applied to low and high fly loading heifers, reduced fly loads on these individuals. This study provides evidence for the hypothesis that the natural differential attractiveness within herds of Holstein-Freisian heifers, i.e. a single host species, for cattle flies is partly due to differences in volatile semiochemicals emitted from the host. It is suggested that this phenomenon applies to other vertebrate host species and their associated insect pests.     

Larvicidal potential of the polyol sweeteners erythritol and xylitol in two filth fly species

The house fly, Musca domestica (L.) (Diptera: Muscidae), and the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), are two filth flies responsible for significant economic losses in animal production. Although some chemical control products target adults of both species, differences in mouthpart morphology and behavior necessitates distinct modalities for each. For these reasons, larvicides are an attractive means of chemical control. We assessed the potential of the polyol sweeteners erythritol and xylitol as larvicides to the house fly and stable fly. LC₅₀ values of erythritol against 2^nd instar larvae were 34.94 mg/g media (house fly) and 22.10 mg/g media (stable fly). For xylitol, LC₅₀ values were 74.91 mg/g media (house fly) and 41.58 mg/g media (stable fly). When given a choice, neither species showed a preference for ovipositing in media treated with either sweetener at various concentrations or in media without sweetener. Significantly lower development from egg to adult was observed when the 2^nd instar LC₅₀ equivalent of each sweetener was present in the media compared to controls. Erythritol and xylitol both have larvicidal qualities, however their effective concentrations would necessitate creative product formulation and deployment methods to control all stages of developing flies.     

Salivary gland hypertrophy virus of house flies in Denmark: prevalence, host range, and comparison with a Florida isolate

House flies (Musca domestica) infected with Musca domestica salivary gland hypertrophy virus (MdSGHV) were found in fly populations collected from 12 out of 18 Danish livestock farms that were surveyed in 2007 and 2008. Infection rates ranged from 0.5% to 5% and averaged 1.2%. None of the stable flies (Stomoxys calcitrans), rat-tail maggot flies (Eristalis tenax) or yellow dung flies (Scathophaga stercoraria) collected from MdSGHV-positive farms displayed characteristic salivary gland hypertrophy (SGH). In laboratory transmission tests, SGH symptoms were not observed in stable flies, flesh flies (Sarcophaga bullata), black dump flies (Hydrotaea aenescens), or face flies (Musca autumnalis) that were injected with MdSGHV from Danish house flies. However, in two species (stable fly and black dump fly), virus injection resulted in suppression of ovarian development similar to that observed in infected house flies, and injection of house flies with homogenates prepared from the salivary glands or ovaries of these species resulted in MdSGHV infection of the challenged house flies. Mortality of virus-injected stable flies was the highest among the five species tested. Virulence of Danish and Florida isolates of MdSGHV was similar with three virus delivery protocols, as a liquid food bait (in sucrose, milk, or blood), sprayed onto the flies in a Potter spray tower, or by immersiion in a crude homogenate of infected house flies. The most effective delivery system was immersion in a homogenate of ten infected flies/ml of water, resulting in 56.2% and 49.6% infection of the house flies challenged with the Danish and Florida strains, respectively.     

Pupal parasitoids (Hymenoptera: Pteromalidae) of muscoid filth flies in Israel

Pupal parasitoids of muscoid flies were collected monthly on three farms in southern Israel in preparation for an IPM programme for the control of filth-breeding flies. 50% and 25.5% of viable puparia collected during 1985 and 1986/87, respectively, were parasitized. Three species of Spalangia Latreille and two species of Muscidifurax Girault & Saunders (Hymenoptera: Pteromalidae) accounted for 82.0% and 94.2% of parasitoids recovered in the two seasons. Variation in the seasonal abundance and distribution of the leading parasite species are discussed in connection with their conservation and possible use for augmentative releases within IPM projects.     

Field effects of faecal residues from ivermectin slow‐release boluses on the attractiveness of cattle dung to dung beetles

A 2‐year study was performed in two sites in southern France to assess the effect of ivermectin residues on the attractiveness of cattle dung to colonizing insects. Insect captures were compared between pitfall traps baited with dung from untreated cattle and dung from cattle that had been treated with a slow‐release (SR) bolus of ivermectin. Cattle dung was collected at different times after treatment (4, 14, 42, 70 and 98 days). Excretion showed a plateau, with levels ranging between 0.688 µg and 1.123 µg ivermectin per gram of wet dung. Faecal residues affected insect captures at both sites. Effects were independent of the time dung was collected after treatment, except for one result subsequent to a severe drought during the baiting period. Ivermectin‐contaminated dung showed a significant attractive effect, with increased captures regardless of the guild to which beetles belonged. This study demonstrates the attractiveness of ivermectin residues over a long period after the treatment of animals. It draws attention to the danger of widespread use of this endectocide‐based SR bolus, which is attributable to the preferential attraction of insects to treated dung, which potentially puts at risk the survival of their offspring.     

Evidence for activation of endogenous opioid systems in mice following short exposure to stable flies

Biting flies influence both physiology and behaviour of domestic and wild animals. This study demonstrates that brief (30 min) exposure of male and female mice to stable flies leads to significant increases in nociceptive responses, indicative of the induction of analgesia. The biting fly-induced analgesia was mediated by endogenous opioid systems as it was blocked by the prototypic opiate antagonist naloxone. Exposure for 30 min to the bedding of biting fly-exposed mice also induced significant opioid mediated analgesic responses in mice. Exposure to either house flies or the bedding of house fly-exposed mice had no significant effects on nociception. These results indicate that brief exposure to either stable flies, or to olfactory cues associated with mice exposed to stable flies, activates endogenous opioid systems leading to the induction of analgesia and likely other opioid mediated behavioural and physiological stress responses. These results suggest the involvement of endogenous opioid systems in the mediation of the behavioural and physiological consequences of biting fly exposure in domestic and wild animals.     

Mites of the familyMacrochelidae as predators of two species of dung-breeding pest flies

Nine species of macrochelid mites [Macrocheles “glaber” (Müller),M. aestivus Halliday,M. mammifer Berlese,M. peniculatus Berlese,M. robustulus (Berlese),M. merdarius (Berlese),M. peregrinus Krantz,M. eurygaster Krantz,Glyptholaspis confusa (Foà) were tested in the laboratory as predators of 2 species of dung-breeding pest flies (Musca vetustissima Walker,Haematobia irritans exigua de Meijere). The mites varied in their ability to attack the 2 fly species at both egg and larval stages. larger mites were generally more effective predators than the smaller species. The level of predation imposed byM. “glaber” onMusca vetustissima also varied with the developmental stage of both predator and prey.      

Exposure to stable flies reduces spatial learning in mice: involvement of endogenous opioid systems

Abstract. Biting flies influence both the physiology and behaviour of domestic and wild animals. This study demonstrates that relatively brief (60min) exposure to stable flies, Stomoxys calcitrans (L.), affects the spatial abilities of male mice. Stable fly exposure resulted in poorer subsequent performance in a water maze task in which individual mice had to learn the spatial location of a submerged hidden platform using extramaze visual cues. Determinations of spatial acquisition and retention were made with mice that had been previously exposed for 60min to either stable flies or house flies, Musca domestica (L.). Mice exposed to stable flies displayed over one day of testing (six blocks or sets of four trials) significantly poorer acquisition and retention of the water maze task than either mice that had been exposed to house flies or fly-naive mice. This attenuation of spatial learning occurred in the absence of any evident sensorimotor or motivational impairments. The reduction in spatial abilites involved endogenous opioid systems, as the decreased performance resulting from stable fly exposure was blocked by pre-treatment with the prototypic opiate antagonist, naltrexone. These results indicate that relatively brief exposure to biting flies can lead to a decrease in spatial abilities which is associated with enhanced endogenous opioid activity. These results support the involvement of endogenous opioid systems in the mediation of the behavioural and physiological effects of biting fly exposure. They further suggest that decreases in spatial abilities and performance may be part of the behavioural consequences of biting fly exposure in domestic and wild animals.     

Studies on the possible role of cattle nuisance flies, especially Hydrotaea irritans, in the transmission of summer mastitis in Denmark

The summer mastitis pathogens Actinomyces pyogenes, Peptococcus indolicus, Bacteroides melaninogenicus ss. levii, Fusobacterium necrophorum and Streptococcus dysgalactiae were isolated from the polyphagous symbovine dipterans Hydrotaea irritans (Fallén) and Morellia sp. caught around dairy heifers on pasture, but not from the haematophagous species Haematobia irritans (L.), Haematobosca stimulans (Meigen), Culicoides sp. and Simulium sp. Secretions from clinical cases of summer mastitis proved to be sources of summer mastitis bacteria for more than 3 weeks despite antibiotic treatment and teat amputation. Taking into account the seasonal activity pattern of Hydrotaea irritans and its topographical distribution on grazing cattle, it appears evident that this fly may play a central role in the establishment and maintenance of the bacterial contamination with summer mastitis pathogens on the teats of healthy cattle. In the present study the survival of A.pyogenes and P.indolicus for 7 days in experimentally infected Hydrotaea irritans, as demonstrated by the recovery of these microorganisms from agar plates exposed to live infected flies, is described. However, experimental transmission of summer mastitis from sick to healthy heifers by Hydrotaea irritans proved unsuccessful.