Protective efficacy of doramectin and ivermectin against Cochliomyia hominivorax

Homeopathic Sulphur Ointment as Adjuvant in the Treatment of Sheep with Myiasis by Cochliomyia hominivorax (Diptera: Calliphoridae): A Case Series

BACKGROUND

 Myiasis by Cochliomyia hominivorax (Diptera: Calliphoridae) is a serious problem in animal health. Homeopathic Sulphur presents similarity with the clinical presentation verified in these cases and has already shown in vitro efficacy on the blowfly that causes this pathology. This article presents the report of a series of clinical cases of myiasis by C. hominivorax in sheep that underwent adjuvant treatment with homeopathic Sulphur and presents a theoretical-scientific discussion of biological events related to the clinical treatment of the condition.

PATIENTS

 Seven naturally occurring myiases affecting sheep from an experimental farm were treated by an ointment impregnated with the homeopathic medicine Sulph 12cH, used as adjuvant after the manual removal of accessible larvae from the wound during wound cleaning. The animals were treated daily and evaluated clinically until complete healing of the lesions. Clinical information on the evolution of the inflammatory and scarring process was collected. Blood counts and bacteriological examinations were performed before and after topical homeopathic treatment.

RESULTS

 The homeopathic ointment Sulph 12cH was able to inhibit the development of parasitic C. hominivorax larvae and promote tissue repair and healing in naturally occurring myiasis in the sheep of this study.

CONCLUSION

 The homeopathic medicine Sulphur, formulated as an ointment, may be a useful new and adjuvant therapeutic option for treating myiasis in animals.

First report of the efficacy of a fluralaner-based pour-on product (Exzolt® 5%) against ectoparasites infesting cattle in Brazil

BACKGROUND

This study describes the effectiveness of a novel active pharmaceutical ingredient, fluralaner (isoxazoline class), against important ectoparasites infesting cattle in Brazil.

METHODS

A total of 13 studies involving a 5% fluralaner-based pour-on formulation (Exzolt 5%; further referred to as Exzolt) were conducted. Specifically, the effectiveness of this formulation was studied against Rhipicephalus microplus (6 studies), Cochliomyia hominivorax larvae (4 studies), Dermatobia hominis larvae (1 study) and Haematobia irritans flies (2 studies).

RESULTS

The therapeutic efficacy of Exzolt was found to exceed 98% at 4 days post treatment (DPT), while persistent efficacy (> 90% efficacy) against repeated infestations of R. microplus was observed for up to 79 DPT. In field studies, ≥ 98% therapeutic efficacy was demonstrated at all study sites by 7 DPT, and a persistent efficacy (> 90% efficacy) was observed for 42, 49 or 56 DPT. Exzolt prevented C. hominivorax eggs from developing to the larval stage, thus mitigating the development of myiasis in cattle naturally and artificially infested with this screworm. The efficacy of Exzolt against D. hominis larvae was 98% at 3 DPT, while persistent efficacy (> 90% effectiveness) was found to last for up to 70 DPT. Against H. irritans, Exzolt showed therapeutic efficacy (≥ 90%) within the first day of treatment at both study sites, while persistent efficacy (≥ 90%) was observed for 7 DPT at one site and for 21 DPT at the other site.

CONCLUSIONS

Overall, the results from these studies confirm that Exzolt is therapeutically efficacious against the most important ectoparasites infesting cattle in Brazil. The novel active pharmaceutical ingredient, fluralaner, provides a new treatment option for farmers to control cattle ectoparasites, especially where there is resistance to other chemical classes. In addition, an effective control of ectoparasites will improve overall cattle health and well-being as well as production.

In vitro test for the evaluation of the efficacy of topical products for the control of Cochliomyia hominivorax larvae

Cochliomyia hominivorax larvae cause myiasis in animals and humans. To register a commercial product to control this dipteran is necessary to experiment on animals. The in vitro test was standardized to evaluate the larvicidal efficacy of commercial topical products. Five formulations were analysed in vitro and in vivo. For the in vitro test, a colony was formed and three replicates (n = 200) of each larval stage (L1, L2 and L3) were treated. The viability of the larvae was evaluated after 5 and 30 min, and at 1, 2, 6, 12, 24, 48, 60 and 72 h post-treatment (HPT). For the in vivo test, 30 bovines divided into six groups were castrated to achieve natural infestation with C. hominivorax. Animals in the treated groups received the product. Myiasis and efficacy were evaluated 12, 24, 36, 48, 60 and 72 HPT. Four formulations tested in the in vitro test achieved 100% efficacy at 24 HPT. In the in vivo experiment only one achieved 100% efficacy at 24 HPT. However, all products achieved the maximum efficacy by the end of study. The in vitro test developed here could be adopted to evaluate the efficacy of topical products for the control of C. hominivorax larvae.

Prophylactic and therapeutic efficacy of Australian-registered insecticide formulations against Old World screwworm (Chrysomya bezziana) infestation

OBJECTIVE

To determine the prophylactic and therapeutic efficacy of Australian-registered insecticide formulations against Old World screwworm (OWS) myiases for potential use in screwworm containment and eradication programs.

METHODS

The longevity of protection provided by six insecticidal formulations (subcutaneous ivermectin, doramectin and abamectin, a topically applied aqueous formulation of spinosad, ivermectin controlled-release capsule and a dicyclanil spray-on formulation) was tested using implants of 1st-instar OWS larvae on Javanese thin-tail sheep. Therapeutic efficacy of four formulations (topical ivermectin, chlorfenvinphos/cypermethrin mixture, aerosol spinosad formulation and a formulation containing propetamphos and eucalyptus oil) was tested against 2- and 4-day-old OWS strikes.

RESULTS

Both the ivermectin capsule and dicyclanil spray-on formulation gave 100% protection against screwworm implants for the full 12 weeks of the study. Ivermectin, doramectin and abamectin administered SC all gave 100% protection at 3 days post-treatment, but at 2 weeks the protection had become incomplete. Spinosad dipping did not give complete protection at any time. All four therapeutic treatments gave complete resolution of 2-day-old strikes and topical ivermectin, spinosad and chlorfenvinphos/cypermethrin, but not the propetamphos/eucalyptus oil formulation, gave complete resolution of all 4-day-old strikes.

CONCLUSION

Dicyclanil spray-on and ivermectin capsule formulations, both registered for use in sheep, but not for cattle or other livestock species, gave much longer protection against screwworm implants than the currently recommended SC ivermectin. Pre-emptive action to facilitate rapid deployment of these formulations in the event of a screwworm incursion is urgently needed.

Proteolytic activity of excretory/secretory products of Cochliomyia hominivorax larvae (Diptera: Calliphoridae)

Abstract: The protein profiles and proteolytic activity of the excretory secretory products (E/SP) of the first (L1), second (L2) and third (L3) larval stages of Cochliomyia hominivorax were studied in the laboratory. Analysis on the E/SP protein profile was carried out using polyacrylamide gel containing sodium dodecyl sulfate (SDS-PAGE). The E/SP of each larval stage (L1, L2 and L3) treated with protease inhibitors, containing 30μg, 40μg and 50μg of protein, was applied to the 10% polyacrylamide gel. The proteolytic activity of the crude E/SP was analyzed in gels copolymerized with gelatin and by colorimetric assays using azocasein as a substrate, with the characterization of the proteases using synthetic inhibitors. Different protein profiles were observed for the larval instars, with L1 presenting the most complex profile. Nevertheless, various protein bands were observed that were common to all the larval instars. The E/SP of all the instars showed proteolytic activity on gelatin, evidenced by proteolysis zones, predominantly with apparently higher molecular masses in L1, while for L2 and L3 the proteolysis zones could also be observed in regions with lower masses. Tests with protease inhibitors using gelatin as substrate showed that the E/SP of larvae were mainly composed of serine proteases. Additionally, inhibition was observed in L2 E/SP treated previously with EDTA, an inhibitor of metalloproteases. The assays with azocasein revealed a gradual increase of proteolytic activity on this substrate with larval development progress, with the strongest inhibitions being observed after treatments with 3,4-dichloroisocoumarin (DCI) for E/SP of L1, L2 and L3. These results suggest that C. hominivorax larvae produce different proteases, a fact that can be related to the parasite's vital processes for survival, such as penetration into the host's tissues and nutrition during the larval stage.

In vitro control of the camel nasal botfly, Cephalopina titillator, with doramectin, lavender, camphor, and onion oils

Camels are very important livestock particularly in arid and semiarid lands. The oestrid fly, Cephalopina titillator (Clark), causes nasopharyngeal myiasis in camels, and it is widely distributed in many camel breeding areas triggering health hazards and severe economic losses in camels. The prevalence of infestation of camels (slaughtered at Tokh's slaughterhouse, Qalyubia Governorate, Egypt, during the period from September 2011 to March 2012) was 41.67 % (100 out of 240). Most infested camels developed clinical signs of nasal discharge, restlessness, loss of appetite, difficulty in breathing, frequent sneezing, and snoring. Postmortem examination of infested camels explained that breathing of the animal is greatly impaired because of blockage of the nasopharynx by larvae and/or mucofibrinous secretions. The larval count per camel ranged from 1 to 250 (mean 28.45 ± 6.48). In vitro larval immersion tests were carried out to determine the efficacy of doramectin (0.003 %) as well as some essential oils (50 % each) such as lavender, camphor, and onion oils against the second and third larval stages (L2 and L3) of C. titillator. Another trial had been done for imitating what could happen if the area around camels were treated with an insecticide or an insect repellent. All treated L2 died 18 h posttreatment (PT) with both doramectin and lavender, and 100 % mortality was reached for L3 after 24 and 30 h PT with lavender and doramectin, respectively. Doramectin and lavender induced the highest response against C. titillator as their lethal time (LT50) values after treatment of L2 were 3.40 and 3.60 h, respectively, and those of L3 were 4.99 and 5.53 h, respectively. Against both L2 and L3 of C. titillator and based on LT50 values of onion oil and those of other applied materials, doramectin and lavender oil were four times more effective than onion oil, and camphor oil was two times more effective than onion oil. Based on LT50 values of essential oils and those of doramectin, as a reference substance, the relative speed of efficacy indicated that camphor and onion oils were, respectively, two and four times less effective than doramectin and lavender. With regard to fumigant technique, neither the insecticide, New Pyrosol, nor the insect repellent, Keto, was effective in controlling C. titillator larvae. Our results indicated that doramectin and lavender could be selected as drugs of choice for controlling C. titillator, but it is not permitted to use doramectin on dairy animals during lactation. Lavender (50 %) has a great potential to be developed as a novel larvicide and could be used as nasal drench against nasal botfly which will reflect on camel production and the national economy.

Patient with tracheostomy parasitized in hospital by larvae of the screwworm, Cochliomyia hominivorax

Myiasis is the infestation of living vertebrates by fly larvae that feed for at least part of their development on the host's dead or living tissues, body substances, or ingested food. The occurrences of traumatic myiasis in humans and animals in urban and rural environments represent serious economic and public health concerns. This study reports a 49-year-old tracheostomized man undergoing chemotherapy treatment who was parasitized in the hospital in São Gonçalo, Rio de Janeiro, Brazil, by larvae of the screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) in the thoracic cavity.

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against myiasis causing parasites on ruminants

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of efficacy of ectoparasiticides against the myiasis causing parasites of ruminants. These guidelines specifically focus on larvicidal efficacy against myiasis causing flies. Information is provided on the selection of animals, dose determination and dose confirmation studies, field studies, record keeping and result interpretation. These guidelines advocate the use of pen facilities for dose determination and dose confirmation studies for defining therapeutic and persistent efficacy. These guidelines are also intended to assist investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the world-wide adoption of standard procedures.

Screwworms

New World and Old World screwworms pose threats to the livestock industry in the United States and other countries. Diligence on the part of veterinarians, physicians, and their respective staffs is essential to protect the livestock industry.

Assessment of cypermethrin and doramectin for controlling wohlfahrtiosis in Crete

The fleshfly, Wohlfahrtia magnifica, became an animal health problem in Crete, Greece, during 1999, causing outbreaks of wohlfahrtiosis throughout the main livestock producing regions of the island. The aim of this study was to determine the efficacy of commercially available drugs in order to design control strategies against wohlfahrtiosis. The test substances were cypermethrin and doramectin sc. The test animals were randomly divided between three groups (30 in each): one treated with cypermethrin pour-on, one treated with doramectin and one untreated controls. The trial lasted 45 days and the animals were inspected daily for natural infestations by W. magnifica. The first infestations were recorded on the 5th, 13th and the 23rd day in the control, cypermethrin and doramectin groups, respectively. There was a statistically significant difference between the survival curves for doramectin and the control group up to day 40, but not at the end of the study.

Efficacy of macrocyclic lactones for the control of larvae of the Old World screw-worm fly (Chrysomya bezziana)

OBJECTIVE

To assess the efficacy of four macrocyclic lactones for the control of larvae of the Old World Screw-worm Fly (OWS), Chrysomya bezziana, and to examine the effects of excreted residues on the dung fauna.

ANIMALS

100 heifers were divided into five groups of 20 animals. One group remained untreated, whereas the other groups were treated respectively with pour-on formulations of moxidectin, eprinomectin or doramectin, or a sustained-release bolus of ivermectin.

PROCEDURES

At intervals of 1 to 15 weeks after treatment, five cattle from each group were challenged with newly-laid eggs of OWS. The efficacy of each treatment was determined 48 h later by comparing the number of myiases in the treated and untreated groups. Abundance of fly larvae in naturally-voided dung pads and the survival of a species of dung beetle, Onthophagus sagittarius, were used to assess the effects of drug residues on the dung fauna.

RESULTS AND CONCLUSIONS

Moxidectin showed no activity against larvae of OWS during the first 14 days after treatment. Eprinomectin provided protection for 3 days after dosing, but failed at days 7 and 14, whereas doramectin was effective at day 7, but not at days 14 or 21. In contrast, no myiases were established on bolus-treated cattle from 14 to 102 days after treatment. Faecal residues of moxidectin had no effect on the survival of larvae of dung-feeding flies, whereas those of eprinomectin and doramectin reduced survival for 1 to 2 weeks. Dung voided by bolus-treated cattle inhibited fly breeding and had adverse effects on the development and survival of O sagittarius for up to 15 weeks after treatment.

Persistent activity of doramectin and ivermectin in the prevention of cutaneous myiasis in cattle experimentally infested with Cochliomyia hominivorax

A study was conducted to evaluate the activity of a single administration of doramectin or ivermectin against severe, induced infestations of Cochliomyia hominivorax. Twenty-four Holstein bull calves were allocated to four groups of six animals each and treated either with saline, doramectin 1%, or either one of two formulations of ivermectin 1% at a dose rate of 200 microg/kg. On Day 12 after treatment, each calf was anesthetized and two wounds were created on the left side of the shoulder and rump of each calf and 2 h later, each wound was implanted with 100 newly hatched larvae of C. hominivorax. On Day 15 after treatment, the procedure was repeated on the right side of each calf. Wounds were examined daily for 5 days and evidence of live larvae was recorded. Doramectin provided reduction in myiasis of 90.9 and 83.3% at 12 and 15 days after treatment, respectively, compared to the saline control treatment (P < 0.0001). In contrast, there were no significant differences in the number of calves with myiasis between those treated with either of the ivermectin formulations and the saline control.