Number of rainy days in a week influencing screwworm navel myiasis in beef calves and efficacies of injectable and topical antiparasitics.

Rainfall incidence as a risk factor for umbilical myiasis by Cochliomyia hominivorax in newborn beef cattle and the preventive and curative efficacies of injectable and topical products against its larvae were evaluated. The prevalence of navel myiasis did not differ between sex, however, it did differ between seasons of the year, independent of animal sex, with it being higher in the rainy season than in the dry season for both sexes (males 64.6%, females 62.1%). During the rainy season, rains occurred intermittently and the number of rainy days in a week had a direct influence on prevalence, with an increase (≥87%) in the number of calves with navel myiasis caused by C. hominivorax. When it rained intermittently for four, five and six days in a week during the rainy season, calves had ≈12, 24 and 11 times greater chances, respectively, of having navel myiasis compared to a week without rain during the rainy season. The injectable products did not reach preventive efficacies higher than 35%, while all treatments of topic products reached 100% preventive efficacy at 10 days post-treatment. Only the formulations with 30% dichlorfenthion and 0.32% fipronil achieved 100% curative efficacy. The results reinforce the need for intensified inspection and healing of the umbilicus during the rainy season, mainly during rainier weeks. Furthermore, topical formulations may be a better alternative as a preventive treatment than avermectin formulations. However, the curative efficacy of the topical product containing dichlorvos did not demonstrate a relationship with preventive efficacy for newborn calves.

Chrysomya bezziana (Diptera: Calliphoridae) infestation in two Malaysian cats treated with oral lotilaner.

The most common fly species associated with screwworm myiasis in Southeast Asia is Chrysomya bezziana (Ch. bezziana), the Old-World screwworm. Treatment of screwworm myiasis in cats traditionally has comprised subcutaneous injection of ivermectin or oral administration of nitenpyram, combined with aggressive tissue debridement and larval removal under general anaesthesia. Two cats diagnosed with cutaneous myiasis caused by the larvae of Ch. bezziana were treated with lotilaner. In both cats, a single dose of lotilaner at 6-26 mg/kg, killed all larvae within 24 h, negating the need for general anaesthesia. Both cats were simultaneously infested with Lynxacarus radovskyi (L. radovskyi) which also was eradicated with lotilaner. No adverse reactions were observed and both cats recovered without complications.

L'espèce de mouche la plus fréquemment associée à la lucile bouchère en Asie du sud-est est Chrysomya bezziana (Ch. bezziana), espèce du vieux continent. Le traitement chez le chat consiste en une injection sous-cutanée d'ivermectine ou une administration orale de nitenpyram, associé à un débridement tissulaire agressif et retrait des larves sous anesthésie générale. Deux chats avec myase cutanée causée par les larves de Ch. Bezziana ont été traités avec lotilaner. Pour les deux chats, une dose unique de lotilaner à 6-26 mg/kg, a tué toutes les larves en 24h, sans besoin d'anesthésie générale. Les deux chats ont été infestés simultanément par Lynxacarus radovskyi (L. radovskyi) qui a également été éradiqué par le lotilaner. Aucune réaction indésirable n'a été observée chez les deux chats guéris sans complication.

La especie de mosca más común asociada con la miasis de larvas barrenadoras en el sudeste asiático es Chrysomya bezziana (Ch. Bezziana), la larva barrenadora del Viejo Mundo. El tratamiento de la miasis de larva barrenadora en los gatos ha consistido tradicionalmente en inyección subcutánea de ivermectina o administración oral de nitenpiram, combinado con debridamiento agresivo de tejido y eliminación de larvas bajo anestesia general. Dos gatos diagnosticados con miasis cutánea causada por las larvas de Ch. bezziana fueron tratados con lotilaner. En ambos gatos, una dosis única de lotilaner a 6-26 mg/kg, eliminó a todas las larvas en 24 h, evitando la necesidad de anestesia general. Ambos gatos estaban infestados simultáneamente con Lynxacarus radovskyi (L. radovskyi), que también fue erradicada con lotilaner. No se observaron reacciones adversas y ambos gatos se recuperaron sin complicaciones.

A espécie de mosca mais comumente associada à miíase no sudeste da Ásia é a Chrysomya bezziana (Ch. bezziana), a larva de rosca do Velho Mundo. O tratamento da miíase por larva de rosca em gatos tradicionalmente inclui injeção subcutânea de ivermectina ou administração oral de nitempiram, associado com debridamento agressivo do tecido e remoção larval sob anestesia geral. Dois gatos diagnosticados com miíase cutânea causada pelas larvas de Ch. bezziana foram tratados com lotilaner. Nos dois gatos, uma dose única de lotilaner de 6 a 26 mg / kg matou todas as larvas em 24 horas, negando a necessidade de anestesia geral. Ambos os gatos foram infestados simultaneamente com Lynxacarus radovskyi (L. radovskyi), que também foi erradicada com lotilaner. Nenhuma reação adversa foi observada e os dois gatos se recuperaram sem complicações.

Efficacy of sarolaner on the treatment of myiasis caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in dogs.

The aim of this study was to evaluate the larval expulsion, larvicidal effect, retention rate of dead larvae and overall efficacy of sarolaner on the treatment of myiasis caused by New World screwworm Cochliomyia hominivorax in naturally infested dogs. Eight Beagle dogs received a single dose of saroalner 40 mg, with dosage ranging from 2.7 mg/kg to 3.7 mg/kg. Evaluations occurred every 15 min in the first hour, every hour for up to 6 h, and after 24 h of treatment. At 24 h post-treatment, total wound cleaning was performed, including removal and counting of remaining live and dead larvae. The animals received antibiotic, analgesic and wound cleaning support until complete wound healing. The average expulsion of the larvae was 50.9 % occurring mainly after 4 h of treatment. The larvicidal effect was 70.6 % at 6 h after treatment and 100 % at 24 h. The mean retention rate of dead larvae of sarolaner was 33.9 %, The overall efficacy was 100 %, thus making sarolaner an excellent treatment option in myiasis caused by C. hominivorax larvae in dogs.

Efficacy of spinosad on the treatment of myiasis caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in dogs.

The purpose of this study was to evaluate the overall efficacy, larval expulsion and larvicidal effect of spinosad on the treatment of myiasis caused by New World screwworm Cochliomyia hominivorax in naturally infested dogs. Six Beagle dogs presenting with myiasis were treated once with spinosad 560 mg, with dosages ranging from 43 to 577 mg/kg. Dogs were observed with 15 min post treatment, and with intervals of 15 min within the first hour followed by hourly evaluations up to six hours post-treatment. After this period, the remaining larvae were mechanically removed. Spontaneous expulsion of larvae was variable among dogs. All dogs received support treatment and were followed up for healing of the myiasis-associated lesion. On average, the highest larval expulsion occurred four hours after treatment. A single spinosad treatment had an overall efficacy of 79.7% (56.7-100%). The average larval expulsion rate was 73.3% (56.7-100%), reached its maximum within 6 h post-treatment, and the average larvicidal effect was only 23.7% (0-58.3%). No animal needed a second dosage 24 h post-treatment, lesions were completely healed within 8 days post-treatment. Despite not reaching the desirable 100% efficacy, spinosad treatment is an option in managing NSW myiasis, in conjunction with mechanical removal of maggots that remain in the lesion and support treatment.

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.

Oral myiasis caused by the screwworm Cochliomyia hominivorax treated with subcutaneous ivermectin and creolin: report of six cases after trauma.

Human myiasis is a rare condition that is more common in regions with a warm and humid climate. The larvae involved in myiasis are voracious; they destroy healthy tissues and may cause serious haemorrhage. The condition can be life threatening. Six patients with craniofacial trauma and oral myiasis are reported. The diagnoses were made after larvae had been extracted. Treatment consisted of subcutaneous ivermectin therapy and the application of a phenol preparation (10% creolin) as a local measure for the control of larvae. After 12 (±1) days of hospitalization, no larvae remained in the patients' mouths and the patients were discharged. The laboratory identified the larvae as those of the fly Cochliomyia hominivorax. Healing was uneventful in the six cases presented, and no undesirable reactions were observed throughout the period of treatment. Although the usual treatment for myiasis involves surgical removal of the maggots, pharmacological therapies are emerging as effective alternatives.

Oral myiasis caused by Cochliomyia hominivorax treated with ivermectin and nitrofurazone: case report.

Myiasis is the infestation of tissues and organs of animals and humans by certain dipteran fly larvae. This phenomenon is well-documented, especially among animals and people in tropical and subtropical areas. Oral myiasis is a rare condition that can be caused by several species of dipteran fly larvae. When the larvae are removed from the mouth, the tissues seem to recover with no subsequent complications and no need for further treatment. This article presents a case involving a patient with oral myiasis caused by Cochliomyia hominivorax and treated with ivermectin and nitrofurazone.

Treatment of oral myiasis caused by Cochliomyia hominivorax: two cases treated with ivermectin.

The term myiasis is applied to the injurious action that larvae of certain diptera cause to the organism of vertebrate animals in the living or dead tissue in which they grow. Because of its great destructive potential, appropriate and preventative treatment are necessary. Among the sites of infestation, the human mouth is a common site, mainly in tropical countries. We present two cases of oral myiasis caused by Cochliomyia hominivorax spp. Ivermectin is an extremely effective semi-synthetic macrolides, in the treatment of this condition.

Evaluation of the prophylactic effect and curative efficacy of fipronil 1% pour on (Topline) on post-castration scrotal myiasis caused by Cochliomyia hominivorax in cattle.

A field trial was carried out during a summer-fall period on a commercial beef cattle farm in Minas Gerais State, located in the Southeast of Brazil. In order to evaluate the prophylactic effect and the curative efficacy of fipronil in a 1% solution, 200 Zebu crossbred bulls, with ages varying from 20 to 30 months and weights from 233 to 362 kg, were selected. The bulls were assigned by ranked pair to an untreated control group (A) or to a treated group (B), resulting in 100 animals per group. All experimental animals were surgically castrated on day 0, following routine procedures. After castration all animals in the group B were treated with 10 mg/kg bw of a 1% fipronil solution, topically on the dorsal mid-line. The wounds were individually inspected on days: 2, 4, 7, 10, 14, 17, 21, 28 and 35. After castration the animals were naturally exposed to Cochliomyia hominivorax and remained in the same pasture throughout the trial. Among the animals in the control group, 83 were observed to harbor C. hominivorax eggs, with a total of 97 ovipositions, and among those 73 animals had active myiasis. In group B (fipronil 1%), 66 animals showed C. hominivorax eggs, with 92 ovipositions and five animals with active myiasis. Most ovipositions and active myiasis were detected until seven days post-castration for both groups. Wound parasite infestation evidenced bleeding, serous purulent exudation and presence of active C. hominivorax larvae. Treatment with fipronil 1% had a prophylactic effect on scrotal wounds against the development of C. hominivorax larvae in more than 95% of the treated animals for up to 17 days after castration. The treatment showed partial protection of 66% and 50% on days 21 and 28 post-treatment (pt), respectively. Three animals from the control group and one from the treated group showed active screwworms on day 21 pt, and one animal from the treated group and two from the control group also presented C. hominivorax larvae on scrotal wounds on day 28 pt. By the end of the observation period (day 35 pt), the castration wound had healed in all animals. All experimental animals presenting scrotal wounds infested with C. hominivorax larvae were treated with a 1% pour-on formulation of fipronil, on the same day that infestation was observed. Active C. hominivorax larvae were not seen during the monitoring period immediately after treatment. The curative efficacy of fipronil 1% against C. hominivorax larvae infestation in castration wounds was 100%.

[Local administration of ivermectin for the treatment of Cochliomyia hominivorax's myiasis]. / Traitement des myiases dues à Cochliomyia hominivorax par application locale d'ivermectine.

Myiasis with Cochliomyia homonivorax induce sensitive and nauseating cutaneous ulcerations. The usual treatment is limited to the mechanical extraction of the larvae. The authors have made a report on the treatment of C. hominivorax by local application of ivermectin. The use of this molecule paralyses and then kills the larvae. This allows rapid alleviation of pain and makes the extraction of the larvae easier.

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.

Prophylactic and persistent efficacy of doramectin against Cochliomyia hominivorax in cattle.

Two prophylactic studies and one persistent efficacy study were conducted in Brazil to evaluate one injection of doramectin at a dose rate of 200 micrograms kg-1 against induced infestations of the New World screwworm, Cochliomyia hominivorax. In each prophylactic study, 12 calves were allocated to two groups of six animals. Six calves were treated with doramectin and six with saline. Two hours after treatment, animals were anesthetized and received two incisions, one in the shoulder and one in the rump. Each incision was then infested with 50 first instar larvae. In the persistent efficacy study, 24 calves were allocated to six groups (T1-T6) of four animals each. On the day of treatment, three groups (T1, T3 and T5) were treated with saline and three groups (T2, T4 and T6) with doramectin. All animals were anesthetized and received four incisions, one in the shoulder and one in the rump of each side. Each incision was then infested with 30 first instar larvae of C. hominivorax with the following schedule: T1 and T2 at Day 3, T3 and T4 at Day 7, and T5 and T6 at Day 14 post-treatment. Calves were observed daily and incisions evaluated for 8 days post-infection. Larvae that completed development and exited the wounds were collected and incubated to evaluate viability. In all experiments, doramectin was 100% efficacious in preventing screwworm infestation caused by field isolates of C. hominivorax. First instar larvae were eliminated from the incisions of doramectin-treated calves between 24 and 48 h post-treatment, and no third instar were recovered at any time. As a consequence, healing started at 24 h and was completed at 96-120 h post-infection. Screwworm infestations and viable third-instar larvae developed in all the incisions in non-treated calves, and healing did not begin until larvae had completed their normal life cycle and exited the wounds. The persistent efficacy of a single injection of doramectin extended beyond 14 days.

The efficacy of insecticides against the screw-worm fly (Chrysomya bezziana).

A number of insecticides used for ectoparasite control in the livestock industry were screened for their efficacy against larvae of the screw-worm fly, Chrysomya bezziana, using in vivo and laboratory tests. Proprietary screw-worm fly treatments (after exposure to outdoor conditions for up to 10 days) were also tested against eggs and adults of C bezziana. Three of these were also evaluated on naturally acquired screw-worm infestations. Residual protection was generally of short duration. Among the organophosphorus compounds, the most effective formulations contained relatively high concentrations (3 to 4% al) of coumaphos, 2.5% fenchlorphos or low concentrations (0.05 to 0.5% al) of diazinon, chlorfenvinphos and fenthion methyl. Two chlorinated hydrocarbon insecticides containing 3% lindane and 5% dieldrin were very effective but are now prohibited for use in Australia. Preparations had serious deficiencies when used under field conditions, especially for treating large, deepseated myiases for which systemic insecticides are recommended. A comparison of methods demonstrated that a laboratory test could supersede live animal experimentation, at least for the initial screening of potential insecticides.

Otolaryngic manifestations of myiasis.

Although rare in North America and Europe, myiasis is seen occasionally in tropical and undeveloped countries. This disorder results from the penetration of a fly larva into a part of the human body, and it causes various symptoms in the host. The exposed areas of the skin are the ones predominantly affected and the eyes, ears, nose, and paranasal sinuses are less commonly affected. We review our experience with 12 patients with myiasis of the ears, nose, and paranasal sinuses.

The efficacy of ivermectin against larvae of the screw-worm fly (Chrysomya bezziana).

An in vitro technique for screening systemic insecticides against larvae of the screw-worm fly, Chrysomya bezziana is described. Susceptibilities of screw-worm larvae of different ages to ivermectin (MK-933) were determined. Based on 24 h larval mortality, the LD50 of 1-,2-,3-,4- and 5-day larvae was 0.01, 0.02, 0.03, 0.2 and 0.4 ppm of ivermectin. LD50 based on adult emergence following treatment of 4- and 5-day larvae was 0.02 and 0.05 ppm. The LD99.9 for 4-day larvae based on 24 h larval mortality and adult emergence was 11.0 and 0.15 ppm respectively and for 5-day larvae, was 44.3 and 0.4 ppm respectively. Pen and field trials with cattle infested with screw-worm fly demonstrated the potential of ivermectin as a systemic insecticide. Dosages of 50, 100 and 200 micrograms/kg, of ivermectin administered subcutaneously to experimentally infested cattle gave complete control for 6, 12 and 14 days respectively. Ivermectin at 200 micrograms/kg caused 100% mortality of screw-worm larvae up to 2 days old at the time of treatment with 70, 64 and 21% mortality of 3-, 4- and 5-day old larvae at the time of treatment. The residual protection from a single dose of 200 micrograms/kg was 16 to 20 days. When bull calves were treated with ivermectin at a dose of 200 micrograms/kg at the time of castration and branding, none of the 77 treated animals sustained a screw-worm strike in the scrotal area compared with 47 strikes (44%) in the 106 control cattle.

The efficacy of some acaricides against screw-worm fly larvae.

Thirteen acaricides used for control of cattle tick in Queensland were evaluated for their potential in the chemical control of the screw-worm fly, Chrysomya bezziana. Laboratory evaluations and in vivo tests using artificially infested cattle were made in Papua New Guinea. Most of the acaricides caused some mortality of screw-worm larvae in infested cattle and in laboratory tests. Acaricides of the organophosphorous, carbamate and organophosphorous/synthetic pyrethroid groups showed reasonable activity against screw-worm fly, but the amidines were less effective.